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[
"How similar is reading notated sheet music to reading the written word?"
] |
[
false
] |
I help teach children music literacy (specifically on-staff notation for piano students). I often read articles about different ways to enhance this process for them, and I also occasionally read articles about teaching literacy in general to children. Some are very practical tips from fellow teachers, some are academic research. What I would like to know is, is it possible to take research on teaching general literacy to children and apply those findings to teaching music literacy? Are the brain processes for reading a book aloud similar to reading a piece of sheet music and performing it? Apologies if the flair isn’t quite right. I’m not actually sure what kind of question this is!
|
[
"I found this interesting article on musical dyslexia that I think answers your question from a neurological perspective.",
"https://neurosciencenews.com/musical-dyslexia-17971/amp/",
" ",
"They are different. Apparently reading music activates a few of the same parts of the brain as reading written words but they are mostly built on different neural networks. Reading the written word relies on connecting the occipital love to the centers of our brain involved in speaking and processing oral language. Reading music appears to involve a lot more of the brain including regions that have nothing to do with oral language.",
"A person could have dyslexia in reading the written word but still be able to read music and vice versa."
] |
[
"Non-scientist here, so take this with a very large grain of salt",
"Reading symbols and converting them to a meaning is probably both present in sheet music and regular reading. The problem is however, that people are taught reading from a very young age and are assigned to read a lot. This isn’t the case with sheet music. So it’s kinda like teaching someone to read for the first time.",
"Myself I’m a pretty good piano player, but I still have trouble reading music. Also, this might be useful for you, there’s a website where people can learn to recognize notes quickly. ",
"https://www.musictheory.net/exercises/note",
". This can help them recognize notes more quickly."
] |
[
"I would somewhat disagree, there are two routes to reading: ",
"the phonological route - converting symbols to sounds to access meaning (grapheme-> phoneme -> word identification -> meaning).",
"the lexical route - memory of practiced patterns of symbols that mean that memory can be accessed without this conversion (graphemes -> word identification -> meaning).",
"Both of these routes are activated at the same time when you see a word, but whichever works fastest is the one that provides you with the meaning you need. ",
"The lexical route - works fastest, but requires you to know what the word looks like in the first place (i.e. have seen it before and see it frequently enough that it has an established place in your memory).",
"The phonological route - enables you to read words you’ve never read before out loud. When you know the meaning of the word from auditory conversation, reading it aloud then allows you to access the meaning of the word that you’ve heard but not seen.",
"Even if you discount the fact that reading language is culturally emphasised before reading music, children have years of experience identifying meaning from the sounds in language before they can even attempt to start reading. Once they then learn the basic rules for mapping the sounds they hear onto the symbols they see accessing meaning would in my opinion be way more fluent because the sounds and meanings are already so well established. ",
"This is my opinion it could be wrong, it is based on my understanding of the dual-route cascade model of reading (Coltheart et al., 2001)."
] |
[
"Why does your heart rate decrease when you hold your breath? Wouldn't that make your heart work harder?"
] |
[
false
] |
I cannot seem to comprehend this phenomena.
|
[
"I'm not sure why this is but on a related note, if you keep your mouth closed and try breathing out then your heart rate will increase due to increased pressure in the chest (",
"http://en.wikipedia.org/wiki/Valsalva_maneuver",
")."
] |
[
"Your heart is a strong muscle in the body that uses up oxygen as it pumps. If it can slow down, this will conserve oxygen.",
"This response is thought to be a vestige of the ",
"mammalian diving response",
". It often requires facial submersion, but in young adults just a breath hold has been shown to significantly decrease heart rate.\nAnother part of the body response is constricting blood vessels out in the periphery like hands and feet. This will slightly raise the blood pressure (which can actually make the heart have to work a bit harder) but mainly serves the purpose of reducing the blood/oxygen going out to less 'important' tissues, and saving it for the brain and heart. Some other mechanisms including the spleen compressing blood back into circulation have been postulated as well.",
"This ",
"review",
" from UBC explains some of the physiology and the hypothesized mechanisms that this reflex saves oxygen."
] |
[
"The same amount of oxygen will get circulated no matter how fast the heart is pumping. There will be a difference in how quick it goes around (not a big deal if standing at rest) and how much energy it takes to get it around."
] |
[
"How do astronomical observatories make self-positioning?"
] |
[
false
] |
If they have static "earth" coordinates, do they consider tectonic plates movement? If they constantly calculate their coordinates what points they use for the references? What the coordinate system do they use and where is origin of this system?
|
[
"Hello, amateur astronomer here. I agree with my learned geologist friend that the baseline is where we know where to expect celestial bodies. This can quite easily be calculated using historic movements whilst factoring in other variables such as gravity of nearby bodies. ",
"On a far grander scale they use very distant quasars and pulsars as they don’t “move” as much m much relative to the earth and are extremely bright. Any movement they do have can be negated by calculating the distance (redshift etc) and therefore calculating the rate of which it is moving away (inflation) from us. NASA uses this technology I believe, in conjunction with various other methods."
] |
[
"Just to add to this, one component that ",
" taken into account during certain high-precision observations is the ",
"Earth tide",
". Much like tides on the ocean, the solid ground beneath your feet can rise and fall as much as a meter twice a day, depending on your location and Moon phase.",
"This turns out to be very important if one if taking observations of lunar ranging. By firing powerful lasers at the Moon and bouncing them off the retroreflector mirrors left by astronauts, we can get millimeter precision of the distance between the Moon and the telescope; knowing the effect of a meter-sized shift in telescope altitude due to Earth tides turns out to be really important in this case."
] |
[
"Hello geologist here. To answer part of your question the movement of plate techtonics is not take into account. This is because observatories use lattitude longitude elevation date time and orientation as their refecernce points for where they are and they sky should be at any given time, much like starmap apps on cell phones. ",
"While some plates move up to 10cm a year average movement is like 2-3cm a year so the effects on obsevatories are pretth minimal. ",
"That being said, once there is enough diplacement over a great peroid of time the observatory would have a slightly different lattitude and longitude. I dont know if their coordinates would be automatically updated by gps, or if it would have to be done manually, but this wouldnt be a problem till far beyond the life expectancy of most observatories. Hope this answers some of your question!"
] |
[
"How Can Drugs Affect You for 12 Hours?"
] |
[
false
] |
I take Dextroamp ER which has effects that last for for 12 hours. How does this happen? Wouldn't my body digest it before then? Also, how does the effect stay consistent for such a long time?
|
[
"Drug metabolism",
", includes two basic premises. ",
"Pharmacokinetics",
" and ",
"pharmacodynamics",
" which describe how drugs react within the body. A drug that is absorbed into the blood stream quickly may have a very long half life within the body because the enzymes and processes that break it down are in short supply, or very slow within the body.",
"The ER on drugs, or sometimes XR means extended release, and thus they are typically released more slowly into circulation through a special enteric coating, which helps ensure there is a more stable level of active drug in the bloodstream for longer. Some drugs don't require this, because of their slow metabolism within the body however."
] |
[
"The big one here is pharmacokinetics. There are several ways to extend the life of a drug in the body but any drug that follows first-order kinetics will need to have a restricted clearance rate to extend its activity"
] |
[
"A nice easy concept to get your head around is the \"therapeutic window\". There's a minimum concentration level (i.e. level of the drug in your blood) that the drug must reach in order to have an effect on your body, below this, nothing will happen. There's also a higher dose level above which, you'll start to experience signs of toxicity. The point of ",
" (the science of drug formulation) is to keep the concentration between these two points for as long as needed. (Incidentally the wider the concentration between these two points, usually the safer the drug is with regard dosing.)",
"ER, MR, XR all mean that the rate at which the active drug is released from the drug formulation ( tablet, capsule, whatever) is modified. In a \"normal\" formulation, all the drug is released once the tablet or capsule is dissolved in the stomach. ",
"3 main ways of doing this for oral formulations are:\n* Matrix systems\n*Reservoir / membrane-controlled systems\n*Osmotic pump systems",
"Each will essentially allow the drug to \"trickle\" out of the capsule / tablet so that the concentration will be in the therapeutic window for 12 hours. The method is all that changes.",
"Hope this makes sense \n",
"Therapeutic window"
] |
[
"In the Scientific American of 1863, it's claimed that if the sun were made of coal, it would only last 5,000 years. Given our present knowledge, how accurate was their estimate?"
] |
[
false
] |
In this month's Scientific American, in the "50, 100 & 150 Years Ago" section, there is this excerpt from August 1863: The Sun "If the sun were composed of coal, it would last at the present rate only 5,000 years. The sun, in all probability, is not a burning but an incandescent body. Its light is rather that of a glowing molten metal than that of a burning furnace. But it is impossible that the sun should constantly be giving out heat, without either losing heat or being supplied with new fuel. Assuming that the heat of the sun has been kept up by meteoric bodies falling into it, and proof has been given of such fall, it is possible from the mass of the solar system to determine approximately the period during which the sun has shone as a luminary. The limits lie between 100 millions and 400 millions of years." The speculation on the sun's source of fuel was interesting enough, but I also thought their 5,000 year coal estimate was interesting. Presumably they had a decent idea of the sun's mass, but how accurate was their estimate of the sun's energy output? Given today's knowledge, how fast would the sun exhaust its fuel if it was made of burning coal? Of course, that's setting aside the physics of whether a sun-sized lump of coal like that would be stable.
|
[
"Coal's energy density is ",
"24 megajoules per kilogram",
" according to Wiki. I'm going to neglect the mass of the oxygen required to combust the coal. ",
"(1 solar mass) x (24 MJ/kg) / (1 solar luminosity) = 4000 years",
"So their estimates of coal's energy density (which will vary depending on the type of coal, so who's to say mine is more accurate than theirs) and/or their estimates of solar luminosity were a little bit off, but still pretty reasonable."
] |
[
"Fascinating! This WP section has some interesting historical tidbits about the discovery of the sun's actual power source.",
"http://en.wikipedia.org/wiki/Hans_Bethe#United_States"
] |
[
"Wow! I had no idea that it wasn't until 1938 that we figured out the exact process by which the sun shines. For some reason, I figured it would have fallen out of one of Einstein's or some other early nuclear physicist's papers on atomic physics. It's such a fundamental question."
] |
[
"If a wooden structure (let's say a log cabin) is adequately protected from moisture and things like termites and fungus, could it last indefinitely? (Let's say 100,000 years.)"
] |
[
false
] | null |
[
"True, but I think that was the gist of the question, i.e. under what circumstances can wood be preserved, and for how long?",
"Here",
" is a fairly-recent story about a mummified forest found in the Arctic that's between 2 and 10 ",
" years old. Note that it's a ",
", not ",
" forest - this is still the original wood, not minerals or other material that has taken its shape. In this case, the preservation was so complete that even ",
" and ",
" are being recovered intact. As kermityfrog noted, the primary reason this wood hasn't decomposed over that astounding period of time seems to be that it was very quickly covered over by landslides, and thus more-or-less protected from exposure to air and light, thereby preventing oxidation."
] |
[
"Streaming Link"
] |
[
"You can ",
"buy",
" wood that is 50,000 years old, so I am going to go with yes on that."
] |
[
"Do people’s core personalities change as they get older, or do they just mature and adapt?"
] |
[
false
] | null |
[
"This may not be the right sub for this question as the anecdotal/speculative answers so far illustrate. So in recognition of the theme of the sub, but without the knowledge to comment on the quality of the sources, here are some studies and articles about studies that I got on a quick google of the topic:",
"APA, 2003: Personality changes for the better with age",
"APA, 2016: Personality Stability From Age 14 to Age 77 Years",
"NPR, 2016: Personality Can Change Over A Lifetime, And Usually For The Better",
"Greater Good, 2018: Can Your Personality Change Over Your Lifetime?",
"LiveScience, 2020: Does your personality change as you get older?"
] |
[
"I don't think you're arguing to the contrary, so I just want to add to your comment by saying that this is absolutely the right sub for this question. Psychology is a science, and personality psychology is a core branch of psychology. However, it's difficult to study personality experimentally, so researchers who study personality have to rely on a variety of methods of scientific inquiry. These include longitudinal and cross-sectional research designs, and various other quasi experimental designs. Personality researchers also study genetics, epigenetics, neurobiology, and other interdisciplinary sciences.",
"I'm a cognitive psychologist, but I do teach upper-level undergraduate personality psychology. In general, the research shows that some core personality traits drift as we age, but we typically stay pretty consistent over time. However, our environments do shape certain traits more than others, and ongoing epigenetic work on this topic is quite interesting to most people. For those interested in more information, those resources in the parent comment are a good place to start!"
] |
[
"Lot of speculation here. Psych generally uses the Big 5 (OCEAN) to quantify \"personality\" - certainly far from perfect but the most scientific way to quantify personality traits at the moment. Studies indicate ~50% of each of these traits is genetic in origin, so we can safely say that about half of a person's personality (based on those measured traits) is unchanging; you're born with it. The other half comes from our environment, is certainly plastic, and will evolve over time - for better or worse.",
"Source: 10.1111/j.1467-6494.1996.tb00522.x\n",
"https://pubmed.ncbi.nlm.nih.gov/8776880/",
"Edit: added the link below the DOI"
] |
[
"Am i right for a Masters Degree in CS? What will it take?"
] |
[
false
] |
I just finished college (Information Technology degree) and I'm in the process of evaluating my options. I really enjoy my field and I couldn't picture myself doing anything else but so far, I've had terrible experiences working in the private sector and I've always wanted to devote myself to research and apply my knowledge to an interdisciplinary area. I may have the opportunity to get a scholarship to study a Masters Degree in Computer Science but I don't know if I've got what it takes for it. Any advice from my fellow redditors?
|
[
"MS in CS degree holder here. What would be your end goal after getting another degree? If you want to do research, a masters degree will open up some opportunities but not nearly as many as a Phd. Also, keep in mind CS research is essentially applied mathematics research.",
"IT has absolutely nothing to do with Computer Science. What is the most advanced math course that you had?"
] |
[
"Vector Calculus, but it's been quite a while since i took it. What kind of math courses do you recommend to refresh my math skills?"
] |
[
"Integral and differential Calculus and discrete mathematics are essential. ",
"What area in CS are you looking to concentrate in? What sort of course offerings does the University that you are considering have?"
] |
[
"What is loop quantum gravity and how does it differ from String Theory?"
] |
[
false
] |
I'm only in my sophomore year in high school, and they don't teach particle physics here at my school. I've read some books on String Theory, but recently I came across "loop quantum gravity" and I don't really understand what it is.
|
[
"This is difficult because, according to general relativity, gravity is not a force. Instead, it's a property inherent to space itself.",
"I dont know why these kind of statements are so popular.. You can describe gravity with a spin-2 force field. It is just that at a classical level the geometric description is much more appealing. The problems from quantizing gravity stem from the fact that the corresponding couplings are non-renormalizable (of course there are also other problems like that the absolute energy scale matters, vacuua in curved spacetimes,.... ). "
] |
[
"This is difficult because, according to general relativity, gravity is not a force. Instead, it's a property inherent to space itself.",
"I dont know why these kind of statements are so popular.. You can describe gravity with a spin-2 force field. It is just that at a classical level the geometric description is much more appealing. The problems from quantizing gravity stem from the fact that the corresponding couplings are non-renormalizable (of course there are also other problems like that the absolute energy scale matters, vacuua in curved spacetimes,.... ). "
] |
[
"A couple articles might be helpful.",
"(1) First, about Loop Quantum Gravity (LQG), here is an excerpt from ",
"this article",
": \"LQG has as one of its central features that space itself is discrete. Imagine a common analogy for gravity: a bedsheet pulled taut, with a bowling ball in the center. Rather than a continuous fabric, though, we know that the bedsheet itself is really quantized, in that it’s made up of molecules, which in turn are made of atoms, which in turn are made of nuclei (quarks and gluons) and electrons. Space might be the same way! Perhaps it acts like a fabric, but perhaps it’s made up of finite, quantized entities. And perhaps it’s woven out of “loops,” which is where the theory gets it name from. Weave these loops together and you get a ",
"spin network",
", which represents a quantum state of the gravitational field. In this picture, not just the matter itself but space itself is quantized.\"",
"(2) This ",
"Quanta magazine article by physicist Sabine Hossenfelder",
" not only contrasts string theory with loop quantum gravity but also considers ways in which the proponents of the two theories might have some common ground to work together."
] |
[
"Would we be able to travel places if we just levitated, using any means not directly in contact with the Earth(some kind of thrust generating machine) and allowing the Earth to rotate as usual?"
] |
[
false
] | null |
[
"No. If you throw a ball up in the air, it doesn't fly behind you"
] |
[
"Throwing up a ball and staying above the ground without coming back are two different scenarios. In my query I mentioned levitation. The ball will fly back if we throw it up while standing on a moving object e.g a train. "
] |
[
"This is not true. If you are inside of a closed moving train, the ball will land back in your hand. There is no magical physics that only applies to levitating objects. If you like, you can think about a balloon or a helicopter. Neither of those magically zooms backwards the moment it is no longer in contact with the earth. "
] |
[
"Do I really need special eyewear for viewing an eclipse? Why/why not?"
] |
[
false
] |
The optics part of my physics series was a bit rushed, but I reckon with some thought I could understand why it's damaging (or why it's not)
|
[
"Yes! I posted this link in another thread:",
"NASA - Eye Safety During Solar Eclipses",
"They have this part in bold: ",
" The first paragraph discuses why. ",
"\"Even when 99% of the Sun's surface is obscured during the partial phases of a total eclipse, the remaining photospheric crescent is intensely bright and cannot be viewed safely without eye protection [Chou, 1981; Marsh, 1982].\""
] |
[
"In spite of these precautions, the total phase of an eclipse can and should be viewed without any filters whatsoever. The naked eye view of totality is completely safe and is overwhelmingly awe-inspiring!>",
"Is the last line of the article..."
] |
[
"It's like looking directly at the Sun... because you're looking directly at the Sun. Having part of it blocked off doesn't help much, in fact it's worse because it makes you think you can look at it for a long time. But the intensity of the light is still the same even if there's less of it, so it can still damage your eyes. The good news is that you ",
" regain full eyesight in one month to a year."
] |
[
"What are the processes in warm blooded creatures that regulate body temperature so precisely?"
] |
[
false
] | null |
[
"That just tells me it's generated in deep organs and lost to the environment, I was looking for a bit more depth than that. Besides it doesnt address how the body so finely tunes it's temperature. "
] |
[
"That just tells me it's generated in deep organs and lost to the environment, I was looking for a bit more depth than that. Besides it doesnt address how the body so finely tunes it's temperature. "
] |
[
"The hypothalamus gland, located at the base of the brain, controls internal body temperature. This gland responds to sensory signals from temperature receptors in the skin and deep inside the body. The hypothalamus establishes a \"set point\" for the internal body temperature, then constantly compares this with its own actual temperature. If the two temperatures do not match, the hypothalamus activates temperature-decreasing or temperature-increasing procedures until the temperatures are equalized.",
"Sources: Guyton, Arthur C. Textbook of Medical Physiology, 8th ed., p. 802; Selkurt, Ewald E. ogy, 5th ed., p. 169.",
"This is for humans, at least."
] |
[
"Do multiple wounds take longer to heal than a single one?"
] |
[
false
] | null |
[
"Assuming several things:\n1. all the wounds are exactly the same in type, size and depth\n2. there's no underlying infection\n3. blood supply hasn't been compromised (either due to the wound or due to the person's hand's arterial supply)\n4. the general condition of the hands are the same, eg no skin disease on one hand compared to the other",
"Then yes, they will heal at the same rate. Healing is based on a lot of things including clotting factors and platelets (the things that form scabs), fibroblasts (which are cells that produce the scars) and blood supply (which is how the clotting factors and fibroblasts arrive at the site of injury) so the main factor is the blood supply",
"This is very simplified but the main gist of it is there"
] |
[
"So if I have this correct, each wound will take a different amount of time to heal but due to each wound being unique and it is not impacted by the quantity of wounds?",
"Edit: Because wow, what happened to my spelling."
] |
[
"Thanks for the detailed answer! Really interesting "
] |
[
"Is the net biomass of Earth constant?"
] |
[
false
] |
Is there any real way of scientists estimating the total mass of all the organisms on Earth? And if so, is this total biomass constant, increasing, decreasing? If increasing/decreasing, where is the extra mass coming from/going to respectively?
|
[
"Pretty much, since most biological material is built on a carbon backbone."
] |
[
"It changes depending on how much carbon is sequestered in non-biological traps, like carbonate rocks or fossil fuels. Carbon trapped in these is not a continuously cycling part of the carbon cycle. "
] |
[
"Right, so it depends on how much of the Earth's carbon supply is actually participating in the carbon cycle?"
] |
[
"Would burning alive be excruciating or would shock/adrenaline block most of it?"
] |
[
false
] |
I've had a pretty natural fear of burning alive (dreams about it and such) and seeing stuff like the woman killed in the elevator this week is deeply disturbing. Having had small burns before I know how painful even second degree burns can be. My question is would it hurt that badly all over your body the whole time or would the pain mostly be blocked? Obviously it wouldn't be pleasant but surely it can't be as bad as I'd think, right?
|
[
"My intensive care unit treats burns, so we see the pretty bad ones; usually anything from 30% upwards. People with big burns are often not screaming with pain, for several reasons I think; full thickness burns are not painful as the nerve fibres have been destroyed but its very unusual for someone to have just full thickness burns. Most injuries will have superficial and partial thickness wounds as well and these are certainly incredibly painful. A massive shock response probably dulls the pain, and of course when I see the patients they have usually already been seen by first responders and given analgesia.\nThe recovery period can take months - just to get out of the ICU and involve many operations as well as multiple dressing changes and various horrible complications. The patients will spend nearly all of this time on a morphine infusion. A really big burn is just a terrible thing to to endure, and to recover from. "
] |
[
"Depends on how you burn. ",
"Medieval and Renaissance executioners would, depending on the accused's crime, their mood, how much the relatives bribed them, the time of day, and any number of other highly scientific factors, either prolong their victims' suffering by causing them to burn slowly from the bottom up, or rig their pyres so as to cause quick unconsciousness and death by smoke inhalation."
] |
[
"Check out an ",
"escharotomy",
" (NSFL) used to treat burn patients. Pretty brutal."
] |
[
"What did the ice front look like during the ice age?"
] |
[
false
] |
Would it appear as a wall of ice or more of a gradual slope that you could walk on. Are there any modern day places that might look similar?
|
[
"It would have looked like the end of modern-day glaciers. In fact, they were glaciers at the ends. In fact, we are still in the ice age today, as there are still significant parts of the earth covered by ice."
] |
[
"TIL glaciers aren't just floating ice mountains. This changes everything. Thank you."
] |
[
"The general public often refers to the last ",
"glacial period",
" as the last ice age, but scientists call the last 2.5 million years ",
"the quarternary ice age",
" during which there were many ",
"glacial-interglacial periods",
". Interestingly the last interglacials periods tended to last only about 10-20.000 years while typical glacials last around 100.000 years. That means there were icesheets covering large parts of Europe and North Amerika most of the time during the last 2.5 million years"
] |
[
"Do butterflies remember being caterpillars?"
] |
[
false
] | null |
[
"Yes and no. Butterflies don’t have a complex memories that humans have, so no they don’t remember being caterpillars. However, caterpillars can be trained to respond to stimuli and they will remember how to react to that stimuli when they’re butterflies. So no they can’t remember being caterpillars, but they can remember stuff they learned while they where caterpillars "
] |
[
"While some parts of a pupating insect do completely dissolve to form new parts, many of the critical organ systems, including the trachea, digestive system, and parts of the nervous system, remain intact, though they undergo some changes. Here's ",
"a link",
" to the paper that found this persistent learning in moths. They refer to research in fruit flies (which also undergo complete metamorphosis) showing that the alpha and beta neurons of the mushroom bodies that form parts of the sensory brain in insects develop during late larval stages and persist through metamorphosis."
] |
[
"I remember reading in an article years ago that when a caterpillar transforms, it dissolves into a liquid in the chrysalis. Do the nerves/brain of the caterpillar stay intact somehow in that process? Or do we not know how the training memories are stored?"
] |
[
"Did Marie Curie ever wonder if the radiation she was studying was dangerous?"
] |
[
false
] | null |
[
"Both Curies were plagued by ailments—burns and fatigue—that, in retrospect, were clearly caused by repeated exposures to high doses of radiation. Both, too, were resistant to the suggestion that their research materials caused their ailments.",
"https://www.smithsonianmag.com/history/madame-curies-passion-74183598/"
] |
[
"Thanks for this link! After 4 years of performing crystallizations she only had a thimble-ful of radium?? Wow she was dedicated! The world owes her so much for her sacrifice"
] |
[
"If you look at some of the devices created years after her discoveries, radium paint (radium girls who painted clocks) and Shoe-fitting fluoroscopes people had no clue.",
"They would have probably attributed the symptoms to long nights in the lab and clumsiness, poor eating habits, or any number of bad habits, none of which were related to the importance of conducting their work in further research.",
"If they'd known, I would think they would have done some precautions but continued as they were determined in furthering mankind and science.",
"Here is an interesting story on how the dangers of radiation and health issues were connected:",
"https://www.news-medical.net/health/Radiation-Poisoning-History.aspx#:~:text=The%20mutagenic%20effects%20of%20radiation,Hermann%20Joseph%20Meller%20in%201927",
"."
] |
[
"Any evidence for fertile hybrid origin for *Homo sapiens* ?"
] |
[
false
] |
There is increasing evidence being reported in the scientific literature of fertile hybrids forming new species for both plants and animals. Orchids of the genera and , rodents , Frogs , Guenon monkeys to name a few examples. A common theme reported is that fertile hybrid formation seems to be associated with ecotones, zones of overlap in species that once had ranges completely separated. Fertile hybrids can result where there is a wide difference in number of chromosomes between parent species. This leads up to my OP question, is there any evidence to suggest that modern humans, , has origin as a fertile hybrid species of two proto-human Hominid species that once had allopatric distribution that over time came to overlap, I assume in Afirica ? EDIT TO OP: Looking at a few Hominid timelines, and assuming can be traced back in time ~200,000 - 220,000 years as suggested from genetic studies, there are a few possible paths for a fertile hybrid origin: 1) 2) 3) 4) 5) others ?
|
[
"There is definite evidence that we cross bred with Neanderthals, it’s quite clear in our DNA. I don’t believe there’s evidence that we are the product of two separate species producing a third, it’s mostly just our ancestor species gaining genetic information from others as we progressed."
] |
[
"All humans are most definitely the same species, starting with the standard biology 101 definition ”can interbreed, producing fertile offspring”. We’re also the same subspecies, ",
". \nThere’s some Neanderthal in those of us that are of European descent, but not enough to make them (or any other human subgroup) a distinct subspecies by any reasonable metric. Any successful hybridization events would have been very rare. ",
"Whether the Neanderthals should be ",
" or ",
" is an open and somewhat controversial question. On the other hand, modern genomics show that humans and the two species of chimpanzees should really be in the same genus; the division between ",
" and ",
" is not well supported."
] |
[
"All humans are most definitely the same species, starting with the standard biology 101 definition ”can interbreed, producing fertile offspring”. We’re also the same subspecies, ",
". \nThere’s some Neanderthal in those of us that are of European descent, but not enough to make them (or any other human subgroup) a distinct subspecies by any reasonable metric. Any successful hybridization events would have been very rare. ",
"Whether the Neanderthals should be ",
" or ",
" is an open and somewhat controversial question. On the other hand, modern genomics show that humans and the two species of chimpanzees should really be in the same genus; the division between ",
" and ",
" is not well supported."
] |
[
"If something was on fire in a fridge that could go to extremely low temperatures and it kept getting colder. Is there a lower temperature limit where the fire can no longer exist?"
] |
[
false
] | null |
[
"Do note, however, that different reactants can ignite at different temperatures. ",
"Foof",
" for example:",
"\"Being a high energy oxidizer, dioxygen difluoride reacted vigorously with organic compounds, even at temperatures close to its melting point. It reacted instantaneously with solid ethyl alcohol, producing a blue flame and an explosion. When a drop of liquid 02F2 was added to liquid methane, cooled at 90°K., a white flame was produced instantaneously, which turned green upon further burning. When 0.2 (mL) of liquid 02F2 was added to 0.5 (mL) of liquid CH4 at 90°K., a violent explosion occurred.\""
] |
[
"Do note, however, that different reactants can ignite at different temperatures. ",
"Foof",
" for example:",
"\"Being a high energy oxidizer, dioxygen difluoride reacted vigorously with organic compounds, even at temperatures close to its melting point. It reacted instantaneously with solid ethyl alcohol, producing a blue flame and an explosion. When a drop of liquid 02F2 was added to liquid methane, cooled at 90°K., a white flame was produced instantaneously, which turned green upon further burning. When 0.2 (mL) of liquid 02F2 was added to 0.5 (mL) of liquid CH4 at 90°K., a violent explosion occurred.\""
] |
[
"There is a technical term for the temperature that you describe. It is called a ",
"Flash Point",
".",
"The flash point is the lowest temperature at which a substance will burn sustainably.",
"Below the flash point the vapour pressure of the combustible material is too low to supply enough fuel for a sustained flame."
] |
[
"\"There is no cure for smallpox, but vaccination can be used very effectively to prevent infection from developing if given during a period of up to four days after a person has been exposed to the virus.\" How does a vaccine work AFTER being exposes? How can giving you more of the virus prevent it?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason:",
"We do not debunk or vet theories or offer peer review on ",
"/r/AskScience",
".",
"For more information regarding this and similar issues, please see our ",
"guidelines",
".",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"Huh? How is this peer review or theory vetting? The scientific consensus is that you can apply the vaccine four days after infection, I'm simply asking how that works?"
] |
[
"It is absolutely not the scientific consensus that vaccines work after infection, with very rare exceptions (rabies - see a recent question asking how that works). If you have a genuine source making this claim, please link to it. Otherwise this is asking to review someone’s incorrect pet theory."
] |
[
"Why are nuclear fusion explosions not 100% symmetrical?"
] |
[
false
] |
Please see photos in comments as an illustration of my question
|
[
"Explosions aren't completely symmetrical for the same reason that no cut cube of steel is perfectly cube-shaped. The mechanical limitations of how we make stuff will always result in imperfections. There's also the \"imperfections\" in how the nuclear reaction won't advance through the reacting material with 100% effectiveness or efficiency. A few atoms slow on this side and a fizzled out proton on that side means that the initial ball of plasma won't be a perfect sphere. And that's entirely ignoring the fact that all of those explosions were subject to Earth's gravity as well.",
"If you're talking about the blobby nudules out the side of those plasma balls, those are guy wires evaporating.",
"Many of those nuclear devices were detonated in place sitting on a large metal structure to suspend them several dozen feet above the ground. Guy wires were used to keep them standing straight. Because the matter in the wires is much thinner and easier to heat than the structure, they evaporated quickly in the first moments of the detonation."
] |
[
"Great response. Thank you "
] |
[
"https://commons.m.wikimedia.org/wiki/Category:Photos_taken_with_Rapatronic_cameras"
] |
[
"It is estimated that there are between 1-10 quadrillion ants on Earth. How did we come to that number?"
] |
[
false
] | null |
[
"Count/ estimate the number of ants in individual colonies of particular species. ",
"Count/ estimate density of colonies of each species in different environments and ecosystems. ",
"Multiply everything out by the measured area of those different environments and ecosystems on the planet. "
] |
[
"Exactly this, and hopefully when all was said and done, the number on the calculator screen was in the 3 quadrillion range (allowing an error of a factor of 3 up or down within 1-10 quadrillion)."
] |
[
"Start with ",
"https://en.m.wikipedia.org/wiki/Fermi_problem"
] |
[
"If the electromagnetic force overcoming the \"strong force\" is responsible for decay -- why do unstable isotopes with a small nucleus decay?"
] |
[
false
] |
Sorry for the dumb question, I am just trying to better my understanding of physics but I am not very well educated. Specifically, I understand that say, when uranium 235 is hit with a free neutron, the Uranium 236 isotope fissions, because its nucleus is bigger than the distance that the strong force is capable of exerting, (about the diameter 2.5 protons?), so the electromagnetic force therefore has enough energy to pull the deformed nuclei apart -- but what is causing unstable isotopes, say carbon 14, to decay, when their nucleus is so small? Writing this out, I'm thinking that my understanding of the "strong force" is totally wrong... surely it doesn't have the kind of centre of "force" that idea of competing forces seems to imagine... I really don't understand where the strong force between the nucleons in the nuclei exist... is it between the individual particles themselves? So I guess I'm trying to find out the relationship between the stability of isotopes to the proton/neutron ration, and how this relates to the strong force/electromagnetic force equilibrium that I was under the impression sort of holds an atom together?
|
[
"Not all decays of unstable nuclei are due to the electromagnetic force overcoming the nuclear force. Your example of Carbon 14 decays via beta emission, and the weak force is responsible for beta emission. Other nuclei decay by emitting alpha particles (He nuclei), which involves the alpha quantum tunnelling through the potential barrier of the nuclear force holding the nucleus together. Only very large nuclei decay via spontaneous or induced fission. ",
"The nature of Nuclear force itself comes from all of the nucleons continuously exchanging (virtual) mesons.",
"As for the stability of isotopes, generally proton rich nuclei will decay via beta + emission, and neutron rich nuclei will decay using beta emission. Alpha emission is related to how tightly bound the alpha particle formed in the nucleus is due to the nuclear force potential barrier and repulsion from EM force."
] |
[
"Oh boy, there's a bunch of things to point out so let me just do one of them. Carbon 14 decays via ",
" which is due to the ",
" which is the force which controls quarks changing flavours. When carbon 14 decays one of its neutrons is converted into a proton due to one of the 'down' quarks changing flavour to an 'up' quark (this also releases an electron and a particle called an electron anti-neutrino)."
] |
[
"Not all decays of unstable nuclei are due to the electromagnetic force overcoming the nuclear force. ",
"oh wow... it seems so obvious to me now haha... Thanks for this, it's what I needed. I still struggle in understanding how adding a neutron is able to destabilise the nucleus, is it to do with the energy of adding a neutron, combined with the changing of the shape of the nucleus? Lots of reading to do -- thank you for clearing up my confusion though.",
"Only very large nuclei decay via spontaneous or induced fission.",
"In this situation, is the thing that finally breaks the nuclei in two, usually as a result of the electromagnetic force overcoming the strong force (after the slow neutron interacting with the uranium nuclei deforms the nuclei's shape)?",
"I understand the basics of fission, (uranium splitting into smaller nuclei, releasing other radiation and also free neutrons which continue the chain reaction if there is a critical mass), but I don't understand what is happening when the neutron is added that causes the nuclei to split -- this is why I posted the question originally. Is it that the energy of the slow neutron greater than the binding energy of the Uranium 235 molecule? Or does it cause it to go into some kind of excited state, similar to electrons with orbital shells and the release of photons in stimulated emission?"
] |
[
"Are there clear examples of self-destructive behavior, similar to alcoholism or overeating, in other species?"
] |
[
false
] |
This question arose out of a discussion of alcoholism. Essentially, do other organisms eat, drink or otherwise over-indulge themselves to death?
|
[
"Laboratory rats were given unlimited access to intravenous cocaine hydrochloride or heroin hydrochloride. Animals self-administering cocaine quickly developed a pattern of episodic drug intake, with periods of excessive cocaine self-administration alternating with brief periods of abstinence. Subjects allowed continuous access to intravenous heroin showed stable drug self-administration, with a gradual increase in daily heroin intake over the first two weeks of testing. The general health of the animals became markedly different: those self-administering heroin maintained grooming behavior, pretesting body weight, and a good state of general health; rats self-administering cocaine tended to cease grooming behavior, to lose up to 47% of their pretesting body weight, and to show a pronounced deterioration in general health. The mortality rate for 30 days of continuous testing was 36% for animals self-administering heroin and 90% for those self-administering cocaine. These results suggest that cocaine is a much more toxic compound than heroin when animals are given unlimited access to intravenous drug.",
"http://jama.jamanetwork.com/article.aspx?articleid=399323"
] |
[
"But what about the ",
"Rat Park",
" experiment? Were the laboratory rats only interested in drugs because their living conditions were bad?"
] |
[
"Alcoholic Monkeys."
] |
[
"Can a compressed helium gas balloon be used to slow an object down from free fall"
] |
[
false
] |
I'm wondering if a space probe, for example, which is descending from orbit (from either earth or Mars) can be slowed by deploying a helium balloon from compressed gas. Would the balloons upward force be enough to slow the fall? Is this a viable alternative to parachutes?
|
[
"Answer! ",
"http://what-if.xkcd.com/62/"
] |
[
"Theoretical, yes. I'll leave out explanations listed elsewhere, but perhaps unmentioned is that the helium won't generate any lift until in the lower atmosphere (when it can displace a heavier gas), and by then your velocity would be too high for any substance we know to realistically contain helium and be lightweight. "
] |
[
"Not sure if I get the question right ... but I will try to answer:",
"You only have free fall in vacuum. And in vacuum a balloon falls as fast as everything else does. ",
"If you mean descending from an orbit above atmosphere into the atmosphere then a balloon would slow the fall theoretically because it would act like a parachute. Practically the balloon would be destroyed in a very short time because of the high speed when entering atmosphere from an orbit."
] |
[
"Why exactly does shaving foam keep a mirror from fogging up?"
] |
[
false
] |
Applying a thin layer of shaving foam on a mirror and wiping it off keeps the mirror from fogging up after a shower, which is very, very practical. My question is: What's the scientific reason behind it?
|
[
"Triethanolamine reduces surface tension, so a film of water forms instead of a bunch of droplets."
] |
[
"Along with Triethanolamine being a surfactant, shaving foams contain oils which adhere to the surface of the mirror and create a hydrophobic barrier which inhibits water from binding to the surface of the mirror."
] |
[
"It's the reason why baby-oil is a widely used mask defogger in scuba diving."
] |
[
"Why does your nose run when eating something spicy?"
] |
[
false
] | null |
[
"“Gustatory rhinitis” affects many people after they eat hot or spicy foods. When a person eats these foods, a nerve called the trigeminal sensory nerve is stimulated, which causes the nose to run. A person may prevent gustatory rhinitis by avoiding trigger foods.",
"Release of histamine, a nonspecific immunity mechanism to external stimulus."
] |
[
"Certain spicy compounds will trigger the TRPV1 receptors (capsaicin/vanilloid receptor) which can cause an inflammatory response due to perceived heat damage. That rush of blood to the face will warm up the sinuses and cause the mucus in them to become less viscous and flow out your nose and down into your throat."
] |
[
"It's your body hitting the \"EJECT\" button and trying to flush it out. remember, almost 2/3rds of your taste is carried by smell, so if you taste spicy peppers, you're getting the scent in your nose. ",
"So of course, your body hits the handle on the mucous toilet and flushes till that spicy turd's gone......."
] |
[
"Could we turn Jupiter into a Sun?"
] |
[
false
] | null |
[
"Looks like you need 13 Jupiter masses to be a Brown Dwarf star"
] |
[
"I think this may have been asked before. The answer is: yes. The object would need to have about 80x jupiter's mass. ",
"Of course, at this point, the \"object\" would basically be replacing jupiter, as the original jupiter would only constitute a small portion of the new object. ",
"As a side note, there is no conceivable reason why we would do this at any point in the future. It would wreak havoc with the solar system and probably make Earth uninhabitable."
] |
[
"As an alternative to dumping 13 more Jupiters into Jupiter, as long as we're speculating on that level, you could put Jupiter into a magnetic jar and shrink it until it was about 1/3rd its current diameter. It would remain a star as long as the jar held. AFAIK, the energy to create such a magnetic jar far exceeds the power output of the sun, and the equipment is hypothetical. But then we don't have thirteen Jupiters to throw in there either."
] |
[
"Changing the speed of light"
] |
[
false
] | null |
[
"Changing it by 1% would probably not affect life a great deal, but it really depends on how you accomplish this. The speed of light may be derived as, for instance, a function of vacuum permeability and permittivity. Is it increased by 1% by changing each of those slightly? If so, perhaps this isn't very important to life.",
"However, what if one is changed a lot, and the other changed a lot in the other direction? The difference could still be 1% in the speed of light, but whilst also significantly changing the properties of many materials. This could clearly affect life (and everything else) a great deal.",
"Similarly, making the speed of light instance would affect life in a manner entirely dependent on how you achieved this. The Universe would have to work in a significantly different way to allow it."
] |
[
"I was thinking not changing it as in humans doing it but simply a theoretical univers similar to ours with either of these two slight diferences. However I think the answer probably doesn't change much huh?"
] |
[
"I was thinking not changing it as in humans doing it but simply a theoretical univers similar to ours with either of these two slight diferences. However I think the answer probably doesn't change much huh?"
] |
[
"What would happen if you light a match on a gas planet?"
] |
[
false
] | null |
[
"Nothing. ",
"On Jupiter, Saturn, Uranus, and Neptune there's no oxygen (O2) to sustain combustion. I doubt your match would even light in the first place.",
"Oxygen binds very readily with hydrogen and carbon to produce water (H2O) and carbon dioxide (CO2), which are more stable than diatomic oxygen. I only know of one mechanism cable of producing an atmosphere rich with diatomic oxygen, and that's photosynthesis. "
] |
[
"Probably not. Nebulae are ",
" sparse from a human point of view. They generally contain around a thousand particles per cubic centimetre, give of take. For air, that number is something like 10",
" . If you were in the middle of a nebula, you wouldn't eve notice it, much less be able to light a match."
] |
[
"Something akin to putting your eye right on your monitor. You see maybe 1 pixel at that distance. Now move 3 feet away, and you see the whole picture. ",
"Scale that up to cosmic distances... "
] |
[
"If the human ear can only hear frequncies up to about 20-22KHz, then what's the point of using a higher sampling rate in digital audio, such as 48KHz?"
] |
[
false
] |
[deleted]
|
[
"Any frequency above a certain point would work, and 44.1 kHz is kind of a weird number and was derived from TV frame rate frequencies (245 x 60 x 3, based on # of lines in a TV field).",
"Since Blu-Ray isn't 60 fps or defined by alternatively scanned lines there isn't any reason to use some weird number like 44.1. So 48 kHz works nice, Blu-Ray is 24 fps.",
"Any digitally stored sound has to return to the analog to be very useful in the real world, and an important part of that is filtering out the harmonics. A pure tone of 1 kHz sampled at 48 kHz and then regenerated with a D/A converter will have an alias at 47 kHz, another at 49, a pair at 96 kHz +/- 1 kHz, etc all the way up to infinity (theoretically). While a human ear can't hear these ultrasonic frequencies they can wreck an amplifier or speaker system and must be filtered out with an analog filter. A higher sampling frequency makes design and implementation of your anti-alias filter easier. For example, if you wanted your system to work up to 20 kHz but you only sampled at 42 kHz, your anti-alias filter would have to have a steep drop off from 20 kHz to 22 kHz where the alias of your 20 kHz tone would end up. It's difficult to design a steep filter like that without messing with the phase of the signal. With a 48 kHz sampling rate your 20 kHz tone's first alias is at 28 kHz and you've got tons of room for filtering, so your analog filter can be small, cheap, foolproof, etc."
] |
[
"Any frequency above a certain point would work, and 44.1 kHz is kind of a weird number and was derived from TV frame rate frequencies (245 x 60 x 3, based on # of lines in a TV field).",
"Since Blu-Ray isn't 60 fps or defined by alternatively scanned lines there isn't any reason to use some weird number like 44.1. So 48 kHz works nice, Blu-Ray is 24 fps.",
"Any digitally stored sound has to return to the analog to be very useful in the real world, and an important part of that is filtering out the harmonics. A pure tone of 1 kHz sampled at 48 kHz and then regenerated with a D/A converter will have an alias at 47 kHz, another at 49, a pair at 96 kHz +/- 1 kHz, etc all the way up to infinity (theoretically). While a human ear can't hear these ultrasonic frequencies they can wreck an amplifier or speaker system and must be filtered out with an analog filter. A higher sampling frequency makes design and implementation of your anti-alias filter easier. For example, if you wanted your system to work up to 20 kHz but you only sampled at 42 kHz, your anti-alias filter would have to have a steep drop off from 20 kHz to 22 kHz where the alias of your 20 kHz tone would end up. It's difficult to design a steep filter like that without messing with the phase of the signal. With a 48 kHz sampling rate your 20 kHz tone's first alias is at 28 kHz and you've got tons of room for filtering, so your analog filter can be small, cheap, foolproof, etc."
] |
[
"Read what you said. The Nyquist theorem needs double the frequency, and humans can hear up to 20khz... =40khz minimum. At that sampling rate, there are bad modulation issues, so the sweet spot for playback was considered 44.1khz using 16 bits. Increased sampling and bitrate does improve the perceived quality of the recording up to a point when dithering back down."
] |
[
"Why is the combustion engine still king of common transportation?"
] |
[
false
] |
It seems like we are so along in knowledge and technological advances, but yet we are still using these semi-primitive ways to get around. Why isn't the hydrogen cell around more commonly? Or other little-to-none emission types of engines?
|
[
"There are still a lot of problems with other types of motors. The most obvious is that the energy storage is super easy (comparably) for combustion engines.",
"Hydrogen is difficult to store. It diffuses through everything and has usually to be kept at very high pressures and/or very low temperatures. Furthermore, hydrogen fuel cells are fickle high tech things (and quite expensive).",
"Electricity is also very difficult to store. The batteries are heavy, super expensive (a battery for an electric car costs in the order of 15000$ and lasts ~10 years, many cars are not worth as much after 10 years) take long to recharge and do not get you very far compared to a full tank of gasoline. Batteries are also quite difficult to control as evidenced by Boeings latest fiasco with the dreamliner.",
"All in all, it is not suprising that combustion engines are still leading."
] |
[
"Gasoline provides the highest energy per weight of any fuel. And it is cheap even when you consider the refinery process. It is fairly safe and readily transported. Even with the inefficiencies of engines, it is the best all around fuel."
] |
[
"Gasoline provides the highest energy per weight of any fuel.",
"This is incorrect. ",
"Gasoline ~46MJ/kg",
"Hydrogen 123MJ/kg",
"http://en.wikipedia.org/wiki/Energy_density"
] |
[
"(Scientific method) Acceptable hypotheses: dark energy and phlogiston"
] |
[
false
] |
I'm not sure how to phrase my question simply, so please forgive me for trying to explain by example. I also don't have any background in physics beyond the AP level, so maybe there are just some technical details I'm not getting. Consider if you were an early chemist, researching the properties of then-generally-accepted phlogiston. As you burn wood, sulphur, coal -- most anything -- their masses decrease as they release phlogiston. So far, so good: the theory is supported. Now you burn magnesium, and, surprise! The mass increases. At this point, I believe, it would be bad form, as far as the theory goes, to explain that, while wood contains phlogiston, magnesium contains "dark phlogiston" with negative mass. It's an ugly, unparsimonious attempt to save a failing theory. As I understand it, dark energy works something like repulsive gravity. We observe that, for most anything, gravity seems to hold, but the universe seems to repel itself. So my question essentially is, why is it then OK to postulate dark energy?
|
[
"First, \"dark energy\" is just the place-holder name we give to whatever is responsible for the observed expansion of space. A lot of research remains to be done to figure out just what it is, but expansion is definitely happening and in the meantime we need some way to refer to the effect.",
"Second, according to the general theory of relativity—our current best model of gravitation, wherein gravity is the curvature of spacetime—there's no reason the effect of gravity must be attractive. One of the ",
" of the theory is that it can accommodate both the observed acceleration of massive bodies toward one another ",
" the expansion of space on large scales."
] |
[
"I would disagree with your assessment that the \"dark phlogiston\" hypothesis would be an illegitimate hypothesis. In fact, it seems it would have been a very reasonable hypothesis to propose. To call such a proposal \"unparsimonious\" or \"ugly\" (always a tricky notion) reflects the perspective of someone who is familiar with the more successful models that were developed subsequently.",
"Of course, you do experiments, you see how the \"dark phlogiston\" model works, and you see if you can come up with other explanations that are superior, or that might explain burning and other phenomena. We all know from our vantage point that this would lead to the rejection of the \"dark phlogiston\" model. But I think it would be reasonable to have viewed the \"dark phlogiston\" model, if it were proposed at the time, as a conservative proposal.",
"As RelativisticMechanic says, it is not intrinsically problematic within general relativity to incorporate dark energy. In fact, it is a very conservative approach. We get to keep all the successful predictions of general relativity and explain the acceleration observed in the expansion of the universe. That's a good reason to propose dark energy. And the real question of how the \"dark phlogiston\" and dark energy proposals would differ is one to be settled by observation and measurement."
] |
[
"Dark energy isn't a thing, it's an observation. ",
" exists to push things apart, this isn't in significant dispute. ",
"You must name this effect, even if you don't know what it is. Dark could just as easily be substituted for almost any word, in this instance synonymous with mysterious. "
] |
[
"Do black holes cores emit photons that just can’t escape to the surface?"
] |
[
false
] | null |
[
"We have no evidence of what happens beyond the event horizon of a black hole so any answer is speculation.",
"The math of General Relativity suggests that the straight line paths (geodesics) through spacetime along which all objects travel, experience such extreme curvature due to gravity that beyond the event horizon, all paths lead to the center. That is, the concept of 'direction' ceases to have meaning because there is only one direction - in. ",
"We don't know what lies at the core of a black hole. It could be the hypothetical 'singularity' - a point where all the numbers go to infinity and the normal laws of physics no longer apply. It could be that some as yet unknown physics steps in to halt the ultimate gravitational collapse into a singularity... in which case there would be some form of object there with a volume, like a much more extreme version of a neutron star (see 'Planck Star' for one such example). We have very little idea of how such objects might behave."
] |
[
"No. There is no direction they could emit photons into. Inside the black hole \"going outwards\" would be going back in time. You can't send a photon to last Tuesday. That is not an issue of Tuesday (the event horizon in this analogy) - the problem is that it's not even a direction in space."
] |
[
"Space is still a manifold, so locally Euclidean, so you could “turn around” and start out in a different local direction. Your path would still terminate at the singularity, of course."
] |
[
"What would happen if water's surface tension was much stronger?"
] |
[
false
] |
I'm interested in how this would change the world around us and everyday life. What if the surface tension doubled? What if it was increased by a factor of ten? Edit: Clarification
|
[
"If the difference in surface tension was reflected in a difference in Hydrogen bond strength, then changing it could have a huge impact on life. DNA pairs by hydrogen bonding and protein structures also often contain regions that are H-bonded to other regions in the protein, helping them to fold into their 3D structures. Changing the strength of H-bonding would probably affect these systems in a catastrophic manner."
] |
[
"Since we're here: From what I can look on the web, mercury is the liquid with the highest surface tension (5 to 10 times larger than most other fluids). Is this correct or is there something exotic with even higher tension?"
] |
[
"Walmart would have to raise prices."
] |
[
"Do mosquitoes have a preferred blood type?"
] |
[
false
] |
I'm asking because I'm usually the one in my dorm that gets surrounded by mosquitoes while my friends are relatively better off. Is it because of my blood type or does body odor has something to do with it?
|
[
"Not blood type, but CO2 levels in your breath, your skin temperature, lactic acid.",
"If you exercise, your skin temperature and lactic acid will be up, attracting mosquitoes. Do you happen to work out more often than your dorm mates?",
"https://abcnews.go.com/Health/things-make-mosquito-magnet/story?id=24676818"
] |
[
"Or drink more beer? That also attracts them"
] |
[
"There have been studies that lead to type O blood being preferred. ",
"https://amp-timeinc-net.cdn.ampproject.org/v/amp.timeinc.net/time/3311624/why-mosquitoes-bite?amp_js_v=a2&_gsa=1&usqp=mq331AQHCAFYAYABAQ%3D%3D#referrer=https%3A%2F%2Fwww.google.com&_tf=From%20%251%24s"
] |
[
"Why is alcohol universally toxic to living things?"
] |
[
false
] | null |
[
"Generally speaking, alcohol (like ethanol) is a solvent meaning it changes the solubility of cellular macro molecules. These can be lipids in cellular membranes or proteins within a cell that can denature if their solubility is altered. As membrane integrity and protein function is essential for all living beings down to bacteria alcohol us toxic for them/us all. ",
"In certain organisms (like humans for example) alcohol is detoxified by enzymatic oxidation. First to acetaldehyde (in case of ethanol, our drinking alcohol) and then to (acetic) acid. Acetaldehyde is very reactive, damaging proteins and even mutating dna. Thus, too high levels of this intermediate product are extremely toxic (and one of the causes for hangovers btw) "
] |
[
"Just wanted to add,",
"The order of toxicity of macronutrients is as follows: (in decreasing toxicity)",
"ethanol --> carbohydrate --> protein --> fat",
"100% of ethanol is oxidized. Conversely, a significant portion of fat may not be and may thus be stored instead if ethanol and fat are ingested together which brings with it a myriad of problems including fatty liver disease.",
"Here is also an interesting comment from ",
"u/the_straylight_run",
" in terms of is it worse to drink beer or soda.",
"Beer, especially stout, has vitamins, minerals, carbs, and fiber in it. It does have a nominal amount of alcohol, but in small doses this is just calories as described above.",
"It can also have hormonal effects (estrogen effects) if used too often and in too high a dose.",
"Soda has no vitamins and minerals. It's carb content is high in fructose, which is just as toxic to the liver as is alcohol. It is full of chemicals which while they have been generally considered safe, are starting to show impacts in places that hadn't been considered before.",
"For example, preservatives and artificial sweeteners were:",
"once thought of as harmful for causing cancer --> not true\nonce thought of as harmful for raising blood sugar --> not true\nonce thought of as harmful for making people crave suger --> unclear\n",
"Now we also have (in mice) evidence that they destabilise the balance of good/bad gut flora and also eliminate some of the diverse beneficial species.",
"Of course all of that research is really new and mice != humans. However, considering that studies about gut flora culture are just now being really examined, and more importantly being connected to other conditions, including obesity, is important.",
"And the picture being painted is the one that a lot of people in fitness already know: eat real food, and avoid heavily processed items. It just may be that these foods people assumed were totally harmless (though calorie dense) were not. It might also mean that part of the obesity epidemic is also due to all of these high calorie, highly processed convenience foods being recommended as equivalent to natural foods.",
"So if I have to choose between a substance that is composed of ethanol and simple sugars, whose potential for metabolic damage is limited (provided it's not abused), and from which at least there is some nutritional value, and a substance devoid of all of those and whose composition is vaguely pointing to being systemically harmful, I choose the latter.",
"In general I make it my mission to 'eat real foods' and in that beer can have a space, but coke cannot."
] |
[
"I choose the latter.",
"Uh, did you mean the former? Because the rest of this sentence sounds like you're saying that soda is much worse than beer."
] |
[
"Can a metal detector detect a higher amount of iron in our blood?"
] |
[
false
] |
For example if I eat mussels, which contain high amounts of iron, am I more likely to set of a metal detector?
|
[
"The answer to your question is yes, but not from food intake. There is a disorder called Hemochromatosis which results in a higher than normal iron content in the body. A normal person has ~4 grams of iron in their body, while someone suffering from Hemochromatosis might have up to 50 grams in their body. These extreme cases have been known to set off standard metal detectors, such as those found in airports.",
"For reference, a 3oz portion of mussels contains ~6mg of iron. You would have to eat thousands of mussels in one sitting before the level of iron in your body would be high enough to set off a detector."
] |
[
"If they're losing blood, and you bleed them enough, the bleeding will stop..."
] |
[
"Blood loss."
] |
[
"Was the cosmic background radiation ever visible?"
] |
[
false
] |
to be clear, the cosmic background radiation has been red shifted down to microwaves. so assuming that someone was there to see it, was it ever visible to the naked eye when it was in the visible light spectrum?
|
[
"The cosmic background radiation dates from when the universe cooled to a temperature of about 3000 K (cool enough when atoms could form; they're electrically neutral, and thus the universe becomes transparent, and so those photons form background radiation from that point forward).",
"If you look at ",
"this image",
", you can see intensity of light at different wavelengths as a function of temperature. The bottom curve shows the distribution at 3000 K, and also shows the portion of that distribution in the visible spectrum. It was an appreciable amount of the background radiation."
] |
[
"\"",
" shifted\"",
"The background radiation you are talking about is thought to be the intense light left over from the big bang. So if you mean, \"did this light ever have a wavelength that falls within what we call the visual spectrum?\" then the answer is yes. But obviously no one was there to view it."
] |
[
"Ah, thanks for pointing out my typo. i made this post pre-coffee this morning so i didn't have my head on right.\ncheers"
] |
[
"Would a half gram of U-238 with a .2% concentration of decaying U-235 be safe to handle in a sealed glass jar?"
] |
[
false
] | null |
[
"Um, why do you ask? (Calls FBI.)",
"Yes. Natural uranium is .711% U-235, so you have some depleted uranium that is less radioactive than something you could theoretically find laying on the ground. Half a gram is not a large quantity. Perhaps someone will do the math for you, but it should be safe enough. The depleted uranium shells the US military uses contain kilograms of depleted uranium, and the military says they're safe to be around... you trust the military, don't you? Don't you?",
"Under the \"as low as reasonably achievable\" dose guidelines you should only expose humans to radiation when there is a purpose for doing so, so you should keep this source in a lead box or similar and only handle it when necessary."
] |
[
"Fresh nuclear fuel pellets (so, somewhat enriched) are handled without more protection than gloves all the time. I wouldn't think depleted uranium would require much more than the usual chemical safety precautions. You don't want to inhale or ingest it, but it should be fairly harmless externally. ",
"Edit: ",
"Here's",
" an MSDS for UO2, and it does say essentially the same thing. \"Minimal external radiation hazard.\""
] |
[
"Both U-238 and U-235 undergoes alpha decay, which is the easiest mode of decay (to block) out of the three common radioactive mechanisms. In fact, it has trouble getting through air.",
"Edit: Fixed non-sensical wording."
] |
[
"Since the singularity of a black hole theoretically has infinite density, would sound then travel at infinite velocity through it?"
] |
[
false
] |
So because sound travels faster the higher the density of the material it travels through, would that mean, in theory, that sound travels at infinite speeds through the singularity of a black hole?
|
[
"Nothing can travel through the singularity, it has no spatial dimensions. There's nowhere to travel from or to."
] |
[
"We don't know that it ",
" exist. What we have is a model that says \"stuff falls toward this one spot and there are no known forces that can stop it, so it all just collects at that one spot.\" If it had some size, then there would need to be some outward pressure holding the \"stuff\" up against the intense gravity, but we don't know of any source of such pressure. In fact, many physicists (probably most of those who work in the area) believe that the singularity is a mathematical artifact that indicates a break-down in our models rather than being indicative of an actual physical singularity."
] |
[
"It is infinitely dense from the outside, not from the inside. We don't know about how the inside works. You can say, in a way, that sound does travel infinitely fast in that we treat the singularity as a point. So the energy entering one side is on the other side."
] |
[
"Why is Optical interconnection faster?"
] |
[
false
] | null |
[
"The main performance increase in fiber-optic interconnects compared to say copper, is the bandwidth that is permitted by the medium, ie; the amount of data that can be travelling the cable at any given moment. (comparable to the width of a pipe carrying water)",
"This is due to fiber-optics using beams of light to transmit the data, which operate at much higher frequencies than copper does. Another benefit of using light is the minimal interference over long cable runs, copper is very susceptible to all sorts of electromagnetic interference meaning it is somewhat more likely that the data does not reach the destination as it was intended and may need to be re-sent."
] |
[
"To expand on that a little, the ",
"capacity of a channel",
" is defined by the following equation (from the Shannon-Hartley theorem):",
"C = B * log2 (1 + S / N)",
"Where C is the capacity in bits/second, B is the bandwidth, S is the signal power and N is the noise power.",
"As bandwidth (B) increases, your channel capacity increases in a linear fashion. Similarly, if noise (N) decreases, your channel capacity increases (though slower than increased bandwidth).",
"Edit: formatting."
] |
[
"Do you mean bandwidth or latency?",
"For bandwidth, it's about modulation rate and Shannon, other posts have treated this quite well.",
"For latency, the term you're looking for is \"propagation velocity\" or \"velocity factor\". In this respect, copper and fiber are very similar, both vary (depending on construction) around 0.7C, whereas radio in free space travels at C.",
"There's also some protocol-related legacy stuff: Most optical gear has a heritage in time-division multiplexing and synchronous networks, which tends to impose a very low latency per hop, per regenerator, etc. Typically one bit-time, sometimes one frame, but because of the way muxes handle interface speeds, one frame of the high-speed interface is typically one bit-time of the lower speed interfaces. :) ",
"Most copper gear has its heritage in packet-based networking, where it's common to have buffers in every device. Read about \"buffer bloat\" and the effects this has on other protocol layers, it's sort of amazing."
] |
[
"Can time be subdivided infinitely?"
] |
[
false
] |
Similarly, is there a time measurement equivalent to the planck length?
|
[
"Nobody knows the answer to whether time can be subdivided infinitely.",
"Yes, there is a Planck time, but whether this is the minimal unit of time is not known. The various Planck scales are simply the scales at which quantum field theory and general relativity must both be included, and so the theory of what happens on those scales depends on having a quantum theory of gravity (or whatever theory harmonizes quantum field theory and general relativity)."
] |
[
"The Planck Time",
" is the time it takes light to travel one Planck Length."
] |
[
"neither/both? Essentially, one of the biggest problems about the math is that we just have no (or very little) data to guide us with what that math should look like. As we'd develop the technology to probe those regions closer, we may get the necessary data to inform us on how to do the maths. So I'd imagine that both problems would end up solving themselves simultaneously.",
"The exception being some very specific ways of making a discrete space time which may have larger measurements we can make. ",
"Some data",
" has ruled out certain models of discretized space-time down to 10",
" m or so (much smaller than Planck scales)."
] |
[
"Has anyone ever tried to properly educate any non human species?"
] |
[
false
] | null |
[
"No non-human animal has language."
] |
[
"But you don't ",
" language to teach. Besides we don't need them to speak a human language. If we made them a language that they could speak we could just translate it. As long as their teacher could understand their language and they could understand ours, we wouldn't need to speak the same language. "
] |
[
"They have no capacity for any kind of language in the way that we do. There is no language they could speak or sign with. "
] |
[
"How do brain-eating amoebas (e.g. Naegleria fowleri, Balamuthia, etc) know the way to the olfactory bulb after binding to the mucosa?"
] |
[
false
] | null |
[
"The olfactory nerves exit the skull into your nose thru the cribriform plate. It's just a thin bone with tons of tiny holes in it for the nerve fibers. Naegleria has a flagella tail so if you accidentally \"snort\" it up your nose when you are in contaminated water, the protozoan can swim up and enter thru the cribriform plate into your skull."
] |
[
"Thanks. Im'a never swim again in any water that is not at least 2% bleach by volume."
] |
[
"Imagine that people use Neti pots with tap water sometimes from unreliable sources"
] |
[
"Is it advances in sheet metal molding that has enabled us to manufacture better looking, modern cars? Or is there something fundamentally different about how we think about aesthetics? Like a cultural difference?"
] |
[
false
] | null |
[
"The front end differences as AdShea mention.",
"Also there is a minimum amount of empty space above the engine to ensure a pedestrian's head cannot hit the top of the cylinder head.",
"There's probably other things I'm not aware of but those are certainly the bigger things."
] |
[
"Modern car design is based around a few things...",
"Obviously not an exhaustive list but essentially design considerations are behind a lot of modern automotive aesthetic.",
"There is a certain aesthetic that some manufacturers try to achieve. For example white tough looking cars are \"in\" at the moment. That will change again."
] |
[
"I've seen this mentioned a lot on car literature but never really seen specifically what the pedestrian safety features are of the newer cars? it's still a many thousand pound metal object hitting a person at high speed, and odds are not good whether it's a 70's caddy or a '13 accord? "
] |
[
"Efficiency of heaters"
] |
[
false
] |
Is a fan forced element heater less efficient then a oil heater? Completely energy sealed room vs normal room
|
[
"On the other hand, ",
" (for heating, in this case) is more effective than any other heater. Why? Because although oil/fan/electric heaters all turn 100% of the energy you invest into heat, air conditioners actually use your energy to ",
" and put it into the room - so in addition to all the energy you spent being turned to heat (as all energy eventually does), there is more heat that came from the outside, resulting in >100% efficiency."
] |
[
"On the other hand, ",
" (for heating, in this case) is more effective than any other heater. Why? Because although oil/fan/electric heaters all turn 100% of the energy you invest into heat, air conditioners actually use your energy to ",
" and put it into the room - so in addition to all the energy you spent being turned to heat (as all energy eventually does), there is more heat that came from the outside, resulting in >100% efficiency."
] |
[
"yea you're right about the air conditioning reverse cycle being more efficient by moving more heat than it creates. you can get carnot cycle efficiencys beyond 200% depending on the volumetric efficiency of the refrigerant you've chosen and its mollier graph. \nair con has a huge isentropic efficiecy compared to more conventional heaters."
] |
[
"Are visual inputs in the center of your retina processed and perceived faster than those in your retina's periphery?"
] |
[
false
] |
Ok, so perfect example: I'm sitting here in my car looking at my phone, scrolling up and down Reddit. In the upper left corner of my left eye, I can see my phone's reflection in my left front window. Now, I SWEAR TO GOD, I'm seeing the reflection in the corner of my eye happen slightly the scrolling that I see happening on my phone in the center of my vision. Like maybe a few miliseconds after. Every time I scroll. Now, assuming light speed is too fast to notice this difference, my guess is the time dilation happens in my brain somewhere. I know the fovea is the most sensitive part of vision. But, is it actually so important to survival that the brain processes information in the fovea it processes information outside the fovea? Meaning, we become consciously aware of phenomena from our fovea before we become aware of phenomena from outside our foveas? So, am I crazy? Or, am I really seeing the same event essentially happen twice in my head due to seeing it from different places in my eye?
|
[
"Signal transduction in wires is slower than light, sometimes by a fairly significant fraction. Signal transduction in nerves is even slower because nerves don’t work like wires."
] |
[
"This may be a similar phenomenon to the one where the second hand of an analog clock sometimes seems to skip a second. During a ",
"saccade",
", we are functionally blind for a brief moment, as the visual information would be too motion-blurred to make any sense. So our brains just extrapolate from past data so we don’t perceive a disruption in vision."
] |
[
"I know a lot of fact about eyes and i never heard something like that.. After, the \"nervous flow\" is electric and as fast as light so it's not caused by the difference distance between the fovea, the periphery and the blindspot. Finally, each cells can be placed in a \"bit map\" so if the brain (can) do(es) that first, it's possible that he analyzes firstly the center, most important in wild life"
] |
[
"How can California be in a drought when they're next to an ocean?"
] |
[
false
] |
[deleted]
|
[
"The technology you're referring to is called desalination and it does exist.",
"Through techniques like reverse osmosis, we can very effectively turn ocean water into drinkable water, and there are plants in operation that do this. The problem is that these plant cost massive amounts of money and take tremendous amounts of electricity to operate.",
"Basically in reverse osmosis, you're using pressure to force the process of osmosis to happen backwards, which as you can guess, it ",
" doesn't want to do!",
"Ultimately the reason is cost, the initial investment is huge, and the energy needs are incredibly high (I.e. expensive) which would then make the water produced very expensive as well.",
"There are developments in desalination and research is being done on improving the efficiency and cost effectiveness of the process, but for now it's just to expensive to be reasonable here.",
"Note: IIRC Qatar is planning to build a desalination plant on the Persian Gulf soon as they need water desperately, and luckily, have a lot of money to spend on infrastructure... Although, the fact that they have no other options probably helped them make up their minds lol"
] |
[
"Yessir, plain ol' evaporation is the most common version of desalinization! The problem is (as mentioned before), it takes a lot of heat to evaporate all of that water. Californians use water at about the same rate as the flow rate of the Nile river (around 100 km",
" /year), so imagine what the engineering project would look like trying to evaporate, collect, and re-condense the Nile river in real time!"
] |
[
"Desalination is expensive",
":",
"Most projects are small, capable of providing less than three million gallons per day, often for rural areas. The state’s largest is in El Paso, where the $91 million Kay Bailey Hutchison Desalination Plant, completed in 2007, can supply up to 27.5 million gallons of water a day, though it rarely operates at full capacity because of the high energy costs associated with forcing water through a membrane resembling parchment to take out the salts. (Production of desalinated water costs 2.1 times more than fresh groundwater and 70 percent more than surface water, according to El Paso Water Utilities.) Last year, the plant supplied 4 percent of El Paso’s water.",
"El Paso's population is 674,000. If costs were strictly scalable, California would need to build 1,400 desalination plants at a cost of about $130 billion, to supply 100% of its water, and that doesn't include the cost of actually running them.",
"Of course they don't need to replace 100% of their water, probably 10% would help a lot. But then suppose they start building, spend $1 billion/year to build enough plants over 13 years to get 10% of their water, but then the drought breaks this year, or in 2 years, or whenever. Now they've got all these plants making expensive water, and then taxpayers start whining about all the wasted money that could have been spent on schools and whatnot."
] |
[
"Total internal reflection question."
] |
[
false
] |
Let's say the critical angle or an incident ray going from one medium to a medium with a higher index of refraction is 60 degrees. Any incident angle smaller than 60 degrees will simply refract through the second medium, while at exactly 60 degrees the refracted ray is parallel to the plane between the media. Now we also know for incident angles greater than 60 degrees total internal reflection will occur. Such that a 70 degree incident ray results in a 70 degree (with respect to normal) internally reflected ray. My question comes from what happens in the differential increase from 60 degrees up to some arbitrary value, like 70 degrees for example. At exactly 60 degrees incidence, the "resultant" ray is parallel to the surface junction; in other words it has an angle of 90 with respect to normal. But at even 61 degrees this resultant/reflected angle becomes 61 degrees. In this short change incident angle (of just 1 degree) we lowered resultant angle by 29. How did this happen? Is the resultant degree non continuous for that region, because it is for all other values greater than the critical angle right? E.g. 70 degree incidence results in 70 degree reflection, 80 for 80... all continuous up to 90 of course. I know this is a bit lengthy and maybe even a bit arbitrary... but I'm just curious; thanks anyway!
|
[
"At angles below the critical angle not all of the light will be transmitted into the second medium. There's something called the coefficient of Reflection (and a related coefficient of transmission), which can be calculated with fresnel's equations. See: ",
"http://en.wikipedia.org/wiki/Fresnel_equations",
"If you take a look at the graph for the reflection coefficient you'll notice it's growth near the critical angle when the second medium has a lower refractive index than the first. In other words even before the critical angle more and more of the light is being internally reflected. This happens in a nice smooth continuous way. The critical angle however is special because beyond that all light is reflected as you know."
] |
[
"Link",
" to a simulation I created that allows you to explore total internal reflection. Just set n2 to a value smaller than n1 and then vary the angle of incidence. Watch the percentages of light reflected and transmitted (simulation requires Java).\n",
"iPad friendly version"
] |
[
"You are awesome!"
] |
[
"Do people in large population-dense cities like Tokyo, Mexico City and New York get sick more frequently, being exposed to more people on a daily basis?"
] |
[
false
] |
Related question: do they end up with stronger immune systems for the same reason?
|
[
"Short answer is yes and possibly. More people touching more areas allows for a greater spread of any bacteria. More hosts allow for a greater chance of mutation and more strains. Each time you contract a strain, even if it doesn't make you physically sick causes your body to create antibodies, thus theoretically boosting your immune system in a way."
] |
[
"The fact that there is some increase in illness isn't surprising. Really, it's interesting that there isn't a MORE striking increase. That's fortunate given our proclivity to live close to one another. "
] |
[
"The increase is definitely noticeable during flu season or among children in those types of locations. With the recent increase in anti-vaccination beliefs, cities are at the highest risk of epidemic outbreaks."
] |
[
"Has anything changed in the last 20 years to make the forecasting of weather more accurate?"
] |
[
false
] |
So I was sitting on my deck and I was looked at my weather app at 11:30. It said that at 12:00 pm there will be a 100% chance of rain. The rain started at 11:50. Is this just a case of weather forecasts being more accurate closer to the event, or has something in the way that weather is forecast fundamentally improved?
|
[
"Now you can get customized forecasts based on your GPS coordinates instead of just your region or town. Radar and instrumentation has also improved over the years. Still, my weather app is wrong almost as often as it is right when it comes to rain forecasts."
] |
[
"You’ll have to specify if you refer to a specific region in the world or if you look at average forecast quality in general. ",
"Weather forecasting is wildly different from region to region. Coastal vs. inland, flat regions va. regions with mountains, regions with lots of lakes and other water vs. with none, area with notable Coriolis effects vs. none, etc etc"
] |
[
"It’s a matter of the app knowing your exact location and the current track of storms. It’s common for my app to send me lightning alerts as well as, “rain will be starting in X minutes”. ",
"To answer your overall question, some of the biggest advancements in weather forecasting has come from the launches of newest GOES weather satellites over the last decade. ",
"Here is a site",
" for some of their data.",
"For a history of the GOES satellites, ",
"check here.",
"."
] |
[
"How does cold welding work? What causes the metal to fuse?"
] |
[
false
] |
I recently read about how cold welding is possible in a vacuum while reading about some space type stuff, but I'm unable to dig up / understand the specifics behind this.
|
[
"If you have two metal surfaces that are extremely clean and well matched, you can compress them together very tightly to make a cold weld. The atoms at the interface start to diffuse and intermingle with one another, resulting in one solid piece of metal.",
"If you cut a metal block in vacuum, you will reveal a fresh, non-oxidized metal surface. These cold welds work much better in a vacuum environment because no metal oxides form at the surface to block the diffusion."
] |
[
"No, whole atoms will move. There are some animations of this ",
"here",
"."
] |
[
"ok I can wrap my head around that. am I correct in assuming that when you mention atoms diffusing it's primarily electrons?"
] |
[
"In the double slit experiment, the peaks and troughs cancel out from the light from the two slits. Why does the peak and trough from a single slit not cancel out on the display screen?"
] |
[
false
] |
I was just thinking of the double slit experiment... We're told (and can see) in the experiments that the waves of light travelling offset from each other cancel out, or reinforce each other... If so - how come we can see any light coming from a single slit? How come it's not got a net brightness of zero, if the wave's troughs and peaks are hitting a screen? What about two light sources and two slits overlaid? Where's the waves go? Surely both sets of light create their own waves and troughs that can still interact? It seems they only exist when light's "split" into two from a single source? It's all very confusing...
|
[
"The peaks and troughs from a single slit do cancel out, this produces what is called a diffraction pattern. It is not completely dark, but it does have alternating light and dark spots.",
"In general, the intensity of light a particular point is due to the amplitudes of light at that point from all possible sources. So, on an approximate level, you could think of a single slit as a rectangular grid of point sources of light. The brightness at some point on the screen is a result of the amplitudes from all these sources added up, after taking phase into account."
] |
[
"Oh! I didn't suspect that! I thought there may have been something deeper happening - in a deeper dimension than usual."
] |
[
"How come it's not got a net brightness of zero, if the wave's troughs and peaks are hitting a screen?",
"The \"brightness\" is proportionnal to the square of the amplitude of the EM field. In average the EM field is 0, but not the \"brighness\".",
"It seems they only exist when light's \"split\" into two from a single source?",
"The interferences always exists. However, if the two light sources have different frequencies (or wavelengths), the resulting signal will vary very fast in the time domain, and only the average is seen. So the interference exist but can't be observed. ",
"In practice, it is next to impossible to have two independant light sources at the same frequency. Especially since the frequency of a light source always fluctuate. ",
"Even stabilized low power lasers have a linewidth >1kHz, this means if you make 2 of those lasers (identical) interfere , you would have about 1000 on/off succession per second, and your eye wouldn't see any interference. Note that we have detectors that can work at >10Ghz and easily see such interferences. "
] |
[
"What are the unique detriments to a Guaranteed Minimum Income?"
] |
[
false
] |
[deleted]
|
[
"Indeed. A guaranteed income needs to not be based on any additional income. You should get that 15k on top of anything else you decide to earn, it should be like your allowance for being a citizen, not something that gets sucked away whenever you put forth effort to try and better yourself.",
"On the plus side though this likely would vastly pump up wages as employers would have to actually attract labor rather than negotiating cheaper wages by means of threat of homelessness and starvation, employees would now have a leg to stand on in wage negotiations, as demand for their labor would stay the same but demand for jobs would sharply drop off."
] |
[
"Indeed. A guaranteed income needs to not be based on any additional income. You should get that 15k on top of anything else you decide to earn, it should be like your allowance for being a citizen, not something that gets sucked away whenever you put forth effort to try and better yourself.",
"On the plus side though this likely would vastly pump up wages as employers would have to actually attract labor rather than negotiating cheaper wages by means of threat of homelessness and starvation, employees would now have a leg to stand on in wage negotiations, as demand for their labor would stay the same but demand for jobs would sharply drop off."
] |
[
"Marginal Revolution has a take on this question from just days ago:",
"http://marginalrevolution.com/marginalrevolution/2013/11/what-are-some-of-the-biggest-problems-with-a-guaranteed-annual-income.html",
"Basically, while basic income could simplify and reap large savings for the entire welfare system, we actually have a complex system of benefits because there are a complex set of issues that pique our sympathy, where we want government to help a little extra: the disabled, the elderly, people who need medical care in emergencies, the EITC to help encourage work and give people a boost when they're getting back on their feet.",
"I like the idea of a basic income, but he raises some good practical questions about how much of the welfare system you'd want to replace with it, and how you'd hold the line to keep it from just heading towards cost overruns."
] |
[
"How come the undersea earthquakes and plate movements don't release oil into the environment under the oceans?"
] |
[
false
] | null |
[
"Oil seeps",
" are naturally occurring undersea oil leaks. They occur in many areas, often with oil wells there too. Oil well operators will often try to blame their own leaks on naturally occurring leaks (and not fix their leaks). My main point: It doesn't take an earthquake to leak oil from the sea bottom. In seismically active areas, an earthquake may exacerbate the issue though."
] |
[
"There are methane clathrates all over the ocean bottoms in oil producing areas. At the pressure and temperature of the sea bottoms, methane forms into an ice-like mineral with water. The crystals are clear and look like ice. The methane forms weak bonds with water and effectively raises the freezing temperature of water so the two are bonded together. In the Deepwater Horizon oil spill (10th anniversary today), capping the well was complicated by the methane clathrates rapidly filling around broken wellhead. The initial plan to put a \"helmet\" over the well failed because the methane clathrates formed so rapidly around the \"helmet cap\", they couldn't get it to seal shut and stop the leak (the clathrates build up prevented the lid from being closed down tight)."
] |
[
"That's wild, In undersea vents I read that they found a flatworm that was like eating frozen methane or something like that.\nI wonder if there are any natural animals or microbes that are found around Oil seeps?"
] |
[
"How come we can't efficiently cool something quickly?"
] |
[
false
] |
I know there's things that can supercool stuff pretty much instantly, but ho come there isn't like a microwave equivalent for cold? Refrigerators/freezers usually take hours to cool something.
|
[
"The biggest reason is that it's much easier to turn useful energy into heat than it is to do the reverse. This is a direct consequence of the ",
"Second law of thermodynamics",
", which can be restated in simple terms as: \"You can't build an isolated device that converts its own heat into useful energy.\" On the other hand, the reverse process (converting other forms of energy into heat) is much easier and in fact is essentially inevitable. Basically all the energy we use in some fashion will end up eventually being dissipated as heat. This means that we can take useful forms of energy, such as say electricity and pass it through a resistor to generate high temperatures as in an oven, or to create a strong electromagnetic field as in a microwave, which can in turn quickly heat an object. However you can never do the reverse!"
] |
[
"On the molecular level, it's a lot easier to speed up the molecules in something moving than it is to slow them down. There are a million different ways you can heat something up. Convection and conduction interactions between the object and the atmosphere, chemical reactions, radiation exposure, electric currents etc. all heat things up. In fact, any and all inefficiencies in a mechanical or electrical system are in the form of thermal energy, or heat. Cooling, on the other hand, is a different story. The only way to cool something down is to expose it to an environment that is colder. The most efficient way to do that is to suck heat out of a closed system using pressurized liquid with high heat of vaporizaiton (the amount of energy per mass at a given pressure required to change a liquid to a gas), but this system is much more inefficient than that of a microwave, which uses microwave radiation. Therefore, an cooling appliance would require far more energy than a microwave to cool something down as quickly as a microwave warms something up."
] |
[
"Nowhere close to a scientist here. Just took his question to mean cooling food rapidly, which can and is done, a lot of people aren't aware of blast freezers because they are really only used commercially."
] |
[
"What causes one chemical to be classified as addictive and another chemical with the same effects non-addictive?"
] |
[
false
] |
For instance there are painkillers that are considered to be addictive and some that are not. What makes this so?
|
[
"I'll chip in. This is hard to explain but I'm gonna try my best. ",
"A lot of brain altering substances work by blocking neurotransmitters. (You'd be shocked how many drugs do this!) So what makes your regular old prozac (fluoxetine) and cocaine. Prozac is an SSRI, which means it blocks the brain from reuptaking seretonin. Cocaine is a dopamine blocker, which stops the brain from reuptaking dopamine and then floods the brain with dopamine. (This is really hard to explain).",
"So people with seretonin deficits take prozac to make more seretonin. And this isn't a huge deal because your brain is usually pretty good about dealing with the amount of seretonin.",
"Dopamine is different because of how the hormone works. It really controls your moods as opposed to seretonin which just controls the extent of your moods.",
"See: ",
"http://upload.wikimedia.org/wikipedia/en/8/88/Dopamineseratonin.png",
"Now with cocaine your brain is flooded with dopamine and your body just can't handle coming back down from that, so typically people take another hit of cocaine so they don't experience the horrible withdrawl. Now hit after hit your body has adjusted to the new level of dopamine, this is now considered normal for your body.",
"Other substances that are addictive work by triggering other key areas of the brain or key hormones. You could write a thousand pages because chemical dependence is really complex... Did I help?",
"This question would be better asked in Neuroscience rather than medicene."
] |
[
"This is not my field so someone else feel free to correct me, but I believe it is the idea of psychologically addictive vs physically addictive. You can argue that all pain killers (among other things) are addictive but I am under the impression those classified as addictive chemicals are physically addictive. "
] |
[
"Excellent points! I was more curious about the biology of physical addiction. I suppose I should have been more specific. "
] |
[
"What's wrong with these Homeopathy studies?"
] |
[
false
] |
I've always believed homeopathy to be a pseudo-science, but yesterday someone provided me with a link to studies on homeopathy that seem to show that it has valid medical applications. List of all the studies: Here are a couple of examples from the list: - Triple blind trial, Significant improvements in patients with chronic fatigue syndrome using homeopathic methods - Double blind trial, found that homeopathy improved hayfever symptoms Most of these studies show that homeopathy works at least better than a placebo, and in some cases leads to significant improvement. I don't understand how this can be the case. Homeopathy seems to violate everything I know about chemistry, but these studies show that it works. What's your take on these studies?
|
[
"The first study states in their abstract that the results were not statistically significant. In any clinical trial you have errors due to the random nature of human response to treatment, so your sample size must be large enough to show that there is a statistically significant difference between two treatments. Imagine flipping a coin 100 times, and it comes up heads 52 times and tails 48. Even though heads came up more, you wouldn't say that the coin is biased, because the difference is so small. This is basically the result they got in this study."
] |
[
"Full meta-analysis's show that Homeopathy performs no better than a placebo.",
"http://www.cochrane.org/search/site/homeopathy",
"If you really want to find out the true results of soemthing you need a meta-analysis. This merges data from multiple trials (that have good methodology) into a single analysis. ",
"http://www.cochrane.org"
] |
[
"Try enough times and anything will ",
"look effective."
] |
[
"How accurate is radiation in fiction (e.g. irradiated cities)?"
] |
[
false
] |
Oftentimes in fiction or science fiction, the film, novel, or video game is set in a place where the setting is irradiated, such as a city that was hit by a nuclear bomb. How realistic (if at all) is it that certain areas could be more irradiated than others? Another example would be the Fallout games, where some areas have extremely lethal levels of radiation, despite the fact that the entire world was equally decimated. Also, some fiction has the survivors living underground and only occasionally make short trips to the surface; is it realistic to only need a gas mask for trips to the surface if the duration is short enough? At what point does greater protection become necessary?
|
[
"The portrayal of radiation in fiction is at best incredibly misleading and at worst outright false. Things like comic books and video games have helped contribute to the widespread (and misplaced, in my opinion) public fear of radiation. Most of the pop-media portrayals of radiation effects, like glowing green or mutating extra body parts, are nowhere near true. In almost any conceivable large radiation exposure scenario, the only widespread effect would be increases in the rate of cancer many years down the road.",
"To respond to your specific questions, radiation due to nuclear fallout is in the form of radioactive isotopes. Each specific isotope also has its own specific chemical properties, and as a result could be concentrated in the ground, water, or air in different places depending on how it interacts with those materials. For instance, if a fallout product is water-soluble, it may tend to accumulate in waterways. "
] |
[
"Thanks for the reply. If the air was irradiated and toxic to humans, would you be able to tell just by breathing it, or would it seem completely like normal air?"
] |
[
"You usually wouldn't be able to tell. The exception is if you had a specific radioactive gas that had a scent or if a smell was added to it (like natural gas in your house)",
"I work in a nuclear plant. You don't 'feel' or sense radiation at all. "
] |
[
"Do long-time smokers have a better chance of surviving smoke inhalation than non-smokers?"
] |
[
false
] |
Title says it all really. Are they better off in the situation of a house/building fire? Or worse off even? Or are they simply just as susceptible as non-smokers?
|
[
"Smokers need oxygen just as much as the rest of us. When they smoke, they are essentially replacing part of their inhale with smoke. ",
"Your question appears to be asking if one can build an 'immunity' to smoke inhalation, that enables a smoke to go longer without air... ",
"It would be the exact opposite. Cigarettes cause a build up of Carbon Monoxide in the Blood stream. This bonds with the Haemoglobin of your red blood cells more readily than oxygen does. ",
"A smoke, particularly one who has just had a cigarette (and potentially caused this fire) will have a higher level of CO in the blood, meaning they would absorb less of the oxygen remaining around them. ",
"Smokers would suffocate first....but only by a small margin."
] |
[
"It's a bit anecdotal. Basically, smoking isn't gong to prevent you suffocating, which is what kills in a fire. The smoke itself doesn't do anything to your lungs, it's the lack of oxygen."
] |
[
"It's a bit anecdotal. Basically, smoking isn't gong to prevent you suffocating, which is what kills in a fire. The smoke itself doesn't do anything to your lungs, it's the lack of oxygen."
] |
[
"What are some examples of reversible chemical reactions?"
] |
[
false
] |
I know there are physical changes such as water changing its state from ice to liquid water which can be easily reversed (changing the liquid water back into solid, ice form). I remember reading in a science textbook that chemical reactions are not so easily reversed, however. Are there any examples of everyday chemical reactions that can be easily reversed?
|
[
"Dissolution is one that comes to mind. Dissolve salt in water and then cool the water down and the salt will begin to precipitate out. \nIf that isn't \"chemical\" enough, then you can think of the same thing about carbon dioxide. When CO2 dissolves in water it follows the reaction CO2 + H2O = H2CO3, known as carbonic acid. This is a reversible reaction and is almost entirely dependent on the ambient pressure of CO2. Imagine when soda is bottled, high pressure CO2 is injected which forces the equilibrium to the right, producing a lot of carbonic acid and dissolving the CO2. When you leave a soda out, there's very low CO2 in the atmosphere, so the carbonic acid breaks back down into CO2 and water and the CO2 enters the atmosphere. This is also the cause of ocean acidification because as global CO2 levels increase, the amount of CO2 dissolving in the ocean increases. This causes more carbonic acid to form, which reduces the pH of the ocean water. "
] |
[
"One example everyday chemical reaction is the charging an discharging of batteries. A redox electrochemical reaction",
"Not to get too much on the complex chemistry of modern lithium ion batteries. Here a summary:",
"A typical Li-Ion battery discharges (when used) undergoes a reversible reaction where lithium metal is oxides to lithium ions to give out electrons (to generate electrical current). When being recharged, current is flowing into the battery supplying the battery with electrons and the lithium ions are reduced back to lithium metals."
] |
[
"Not a very helpful answer but every reaction is reversible, its just that in the case of what we call irreversible reactions the equilibrium so far toward the products that the concentration of reactant species is negligible.",
"The best example I can think of for a reversible reaction in the way we mean it most of the time is the autoprotonation of water",
"2 H2O -> H3O(+) + OH(-)",
"H3O(+) + OH(-) -> 2 H2O"
] |
[
"Schroedinger equation and wavefunction"
] |
[
false
] |
Schroedinger's equation contains the imaginary unit, i, and the solution (wavefunction psi) is a complex function. Indeed, Roger Penrose devotes pages in his books to develop and comment on the use of complex quantities in quantum physics....seemingly to say that somehow, complex quantities are needed to describe the physical world. In fact, a little math shows that the Schroedinger equation can be expressed as a pair of coupled real equations whose solutions are the real and the imaginary parts of the complex wavefunction, psi. Just substitute psi = psireal +i psiimag into Schreodinger's equation to find the two real, coupled equations. (psireal and psiimag are, respectively, the real and the imaginary parts of psi.) So it seems to me that in principle there is no need to use complex quantities in quantum physics. Perhaps the use of complex quantities is simply a convenient mathematical tool? I am really puzzled why this is not mentioned by Penrose or other quantum physicists. Am I missing something important?
|
[
"So it seems to me that in principle there is no need to use complex quantities in quantum physics.",
"It's true that one could use two real-valued equations to represent the original complex values and terms. But that would be more difficult, the math would be more involved, and the outcome would be less intuitive.",
"Consider this example:",
"(1) ",
"[; \\displaystyle f(y) = \\int_{-\\infty}^{\\infty} f(x)\\ e^{-2\\pi i x y} dx ;]",
"The above is the classic Fourier transform (time -> frequency). And here is its inverse (frequency -> time):",
"(2) ",
"[; \\displaystyle f(x) = \\int_{-\\infty}^{\\infty} f(y)\\ e^{2\\pi i x y} dy ;]",
"Consider that equation (1) converts from the time domain to the frequency domain, and equation (2) converts from the frequency domain to the time domain, ",
".",
"The above equations rely on a property of the complex exponential that looks like this (Euler):",
"[; \\displaystyle e^{2 \\pi i \\theta} = \\cos{2 \\pi \\theta} + i \\sin{2 \\pi \\theta} ;]",
"But without the use of complex numbers, this remarkable relationship is not available -- it might as well not exist. One would have to write out a series of discrete sine and cosine terms for each transform, and the mathematics would be much more involved.",
"Read more about ",
"Euler Formula",
" : \"named after Leonhard Euler, a mathematical formula in complex analysis that establishes the deep relationship between the trigonometric functions and the complex exponential function.\""
] |
[
"So it seems to me that in principle there is no need to use complex quantities in quantum physics.",
"Pretty much, yeah. You could always reformulate them in terms of real and imaginary coordinates, psi would be a length 2 vector consisting of the real and imaginary part of our current formulation. Replace every i with the 90 degree rotation matrix. It would be fine, and a lot harder to work with."
] |
[
"Thanks, lutusp. You have answered my question. We use complex functions for the same reason in electrical engineering. As you said, real functions could be used, but the math would be more involved etc. I just had not seen anyone say this wrt Schroedinger's equations and its solutions ....i am glad to get this confirmation from you. "
] |
[
"If I started a fire and then fed it nothing but damp cardboard, would the energy in the cardboard be enough to keep it going despite the water?"
] |
[
false
] | null |
[
"Water has a specific (quite high) heat capacity, which means it takes a certain amount of thermal energy to saturate it to the point it boils away.",
"If the global heat capacity of the water in the cardboard is greater than the thermal energy you get by burning the dried up mass, you're not breaking even and the fire cools down.",
"With enough water (or any coolant, for that matter), you can make the reaction no longer self sustainable and kill the fire no matter how much fuel is left."
] |
[
"I agree with your analysis, but it doesn't really answer my question. It does clarify the question though:",
"Is the global heat capacity of the water in damp cardboard greater than the thermal energy from burning the dried mass?"
] |
[
"\"damp cardboard\" a bit too much of an umbrella term for a proper calculation.\nThe type of cardboard can vary the amount of water it can hold by probably an order of magnitude (think about how many ways the paper can be folded in the layers, depending on what features the manufacturer is after).",
"If you're talking about ",
"this",
", my gut feeling is that it wouldn't be sustainable.",
"Here's a quick experiment you can make: soak a large amount of it in water, (a REALLY large amount, you need your sample to be overwhelmingly big to make losses nearly negligible) then squeeze out/evaporate all the water in order to collect it. Pour it into a large pot and use the dried up cardboard as fuel in an attempt to turn it into vapor.",
"If in the end the water's gone and there's still enough heat left to kickstart a new fire, you just invented a cheap way to extract energy from wet organic waste.",
"You could do it by trying to burn wet cardboard too, but you'd need a far larger amount of cardboard",
"EDIT: added last sentence"
] |
[
"Why does hot water sound different when it's poured?"
] |
[
false
] | null |
[
"The viscosity of water changes significantly with temperature (hot water \"flows easier\" than cold water). Viscosity and speed of sound are related, and the propagation speed of sound waves is an important factor in the sound it makes when poured."
] |
[
"No, viscosity is not related to density. Water's densitiy is not constant, but the variation is not that high, and much less noticeable than the variation in viscosity."
] |
[
"It always seemed intuitive to me that density and viscosity would be related. Mercury is a great counterexample to keep in mind."
] |
[
"Why does gas-stove and electric stove cook foods differently, even though they are both indirect?"
] |
[
false
] | null |
[
"IANAS but I imagine it's because of the distribution of heat on the pan, as well as the speed at which the temperature can change."
] |
[
"This seems correct. I've cooked with both and gas seems to have the great benefit of quick temperature change."
] |
[
"Chef here. That is correct. Also, whenever you add food to a hot pan, the temp drops. When using gas, its easier to maintain the heat. It's much easier to get that golden crust on scallops using gas. "
] |
[
"How powerful must a laser be in order to see the beam in air?"
] |
[
false
] |
I know it's a function of how hot the air gets before it starts to glow, so how powerful of a beam would it take to make it visible in daylight? EDIT: To clarify, I was watching a video of a Naval vessel firing a laser at a target. The beam was invisible, but the target exploded almost instantly. How powerful would that laser have to be for the beam to glow bright enough to see with the naked eye in broad daylight?
|
[
"Maybe you should clarify your question -- do you mean a hypothetical scenario in which the air is totally free of dust, or do you just mean in practice? In practice it depends on the color of the laser, but roughly speaking you can (barely) see the beam above around 20 mW or so in daylight. "
] |
[
"Yes in a vacuum in would be invisible regardless of wattage. But ordinary air is filled with dust (sometimes this is really obvious if light comes through a window in your house at the right angle), which reflects light. "
] |
[
"It depends on the wavelength, but in clean dry air you get air breakdown with around a TW per cm",
" so maybe around 100 MW for the usual beam profile of a laser pointer. But with the right kind of dust you can initiate breakdown much lower, and I think it just depends on the size and type of dust that's in your air. I know you can get continuous air breakdown with as low as a few kW infrared laser with a diffraction limited focus, but you need some dust to get heated up in the beam to initiate it. "
] |
[
"If the level of energy in the universe is constant, how is it that it is constantly expanding ?"
] |
[
false
] |
[deleted]
|
[
"There's no real reason to suspect that energy is conserved in the universe. Conservation of energy is a consequence of certain symmetries of a system (specifically time translation symmetry), and an expanding universe does not ",
" that symmetry."
] |
[
"expanding is easy, it's the accelerating part that's a bit trickier. if you assume energy is constant, it is still being reorganized into different forms. These different forms can cause the universe to expand and cool down simultaneously. No physics violated :)",
"In string theory, things get a bit weirder. You end up with particles (we know about those) and anti-particles, which are paired with a particle. So we have matter and anti-matter, energy and dark energy, protons, and anti-protons. Where it gets weird is the theory that matter can come from nothing. So whenever this process occurs, you get a particle and an anti-particle. The net energy is still zero, so physics is still not violated, but it's certainly weird. Also, gravity is thought to be a lots of negative energy. ",
"If you throw a rock in a pond, you get a ripple. Assuming no edge of the pond this ripple will continue forever (like a tsunami) and remain the same height. If an initial disturbance brought matter into existence like this, the center will reach a zero energy state soon after the disturbance and the outer ring will still be moving outwards. So the stars at the center will die, and new stars will be born on the edge of the ring. Eventually, a new rock will be thrown in the water and this will repeat.",
"http://richarddawkins.net/articles/806-stephen-hawking-says-universe-created-from-nothing"
] |
[
"Galaxies do die out, because they throw all of their energy out into space as heat, and since the universe is expanding, but cannot gain energy the AVERAGE temperature of the universe is becoming colder."
] |
[
"If meditation is good for the brain, is the opposite of mediation(chaotic, unfocused thoughts) bad for the brain?"
] |
[
false
] | null |
[
"I think you're going to have to explain your premise before anyone can answer your question. In what way do you think meditation is \"good\" for the brain? Do you have a source that states that meditation is \"good for the brain\" so we can form an objective definition for what that might mean?"
] |
[
"The source you provided doesn't suggest that meditation only reduces symptoms in those with illness already - \"Among healthy subjects, 5 RCT’s were performed in 247 students[36]. Anxiety decreased significantly compared to students that did not receive MBSR,...\". ",
"And even more importantly, they only evaluated 1 type of intervention (MBSR - which involves meditation, but also things like counseling for disease acceptance) with respect to a small set of clinical endpoints. So even if it had a negative result (which it doesn't), it wouldn't be good evidence that meditation \"does nothing\""
] |
[
"Thus, the 'opposite' of mediation would also do nothing. ",
"In the best interests of OP, I would suggest that you don't jump unscientific conclusions like that. You may well have sources that suggest that meditation does not have a positive effect anyway - but that doesn't necessarily mean the opposite is true, which is what OP was asking. You haven't really answered the question."
] |
[
"Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science"
] |
[
false
] |
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away!
|
[
"[deleted]",
"\n ",
"This comment has been overwritten by ",
"this open source script",
" to protect this user's privacy. The purpose of this script is to help protect users from doxing, stalking, and harassment. It also helps prevent mods from profiling and censoring. ",
"If you would like to protect yourself, add the Chrome extension ",
"TamperMonkey",
", or the Firefox extension ",
"GreaseMonkey",
" and click Install This Script on ",
"the script",
" page. Then to delete your comments, simply click on your username on Reddit, go to the comments tab, scroll down as far as possible (hint: use ",
"RES",
"), and hit the new OVERWRITE button at the top."
] |
[
"The Big Bang Theory is pretty simple, and extremely general. It says that in the distant past the universe was a hot dense almost featureless soup of particles. This expanded and cooled, and the material fragmented into galaxies, stars, planets, etc.",
"We can directly see back to when the universe was hot, dense, and almost featureless - the light from this time is called the \"cosmic microwave background\". We can also see that the universe is expanding, and has been expanding for as far as we can see. We also know that the relative quantities of all the different elements we have is just what you'd expect from a universe that started as a hot dense soup that was then enriched by nuclear fusion in stars.",
"This is completely solid, and I've never seen any argument against it that wasn't based on ignorance or just plain silliness. At this point, it's on the same level as \"the Earth is round\".",
"However, this is just the \"big picture\" of the Big Bang. There are plenty of details that are not known. The acceleration of the universe appears to be accelerating and we don't know why. This doesn't cast any doubt on the fact that the universe is expanding, it just means there's something else going on too. We also don't know what happens ",
" the universe was hot and dense - does it go on forever backwards in time? does the universe \"bounce\" back again? is there a finite point where we reach the beginning of the universe? This isn't known - but this isn't actually part of the Big Bang Theory.",
"So yes, the general picture of the Big Bang Theory has plenty of evidence and is pretty much indisputable. But that doesn't mean we know absolutely everything about the universe."
] |
[
"Is it possible that on a large enough scale our universe is in a \"solid\" state?",
"Just as my desktop appears solid but is largely empty space - as our known universe is."
] |
[
"How come we see the Milky Way almost as though we’re outside of it?"
] |
[
false
] | null |
[
"The galaxy is flattish and you can see along it... I'm not sure what you mean exactly. You are inside your room and can see the room"
] |
[
"Do you mean why is it only a strip and not taking up the entire sky? That's because it is \"flat\" like a disc. There are some renderings ",
"here",
" that might help"
] |
[
"No worries =) sorry if I didn't understand your initial question"
] |
[
"How much does covering your mouth with a hand/scarf etc or mask protect you from pathogens?"
] |
[
false
] |
[deleted]
|
[
"It varies with the pathogen and whether it is truly airborne or just aerosol (that is, contained within tiny droplets of water). Aerosols are generally mostly blocked by any mask/scarf, while truly airborne pathogens are nowhere near as affected.",
"Note that unless the mask/scarf is washed fairly quickly afterwards, it can hold the aerosol pathogens right next to a person's face, dramatically reducing the protection it offers."
] |
[
"It's actually to stop the wearer making others sick and not to avoid getting ill himself (for which it has no effect). Western hospitals use them for the same reason."
] |
[
"Agreed, but while its purpose isn't to provide protection to the wearer, it does provide a small amount."
] |
[
"Does the total volume of precipitation in the sky vary? If so, by how much?"
] |
[
false
] | null |
[
"Unsure what you are asking. Are you asking if the amount of water vapor varies? If so, it clearly does because humidity varies widely over the Earth."
] |
[
"Yes, I'm asking about water vapor in the air. Is it possible to find out the ranges of vapor?"
] |
[
"This in no way my expertise... perhaps start with ",
"http://en.wikipedia.org/wiki/Water_vapor",
". This article states:",
"Gaseous water represents a small but environmentally significant constituent of the atmosphere. The percentage water vapor in surface air varies from a trace in desert regions to about 4% over oceans."
] |
[
"Can one \"burn off\" ingested caffeine? (Or other drugs)"
] |
[
false
] |
If 2 people drank a cup of caffeinated coffee (or whatever method you prefer) that had X milligrams, one (person A) remained sedentary for the day and the other (person B) exercised rigorously (a good 2-4 hours worth) throughout the day, would the caffeine stay in both their systems for the same amount of time or would Person B 'use' it faster?
|
[
"Mainly decomposed by CYP1A2 in liver"
] |
[
"Not really. Most drugs are broken down and/or excreted by the liver & kidneys as the main method of excretion. They don't normally get used up because they act like catalysts for physiological processes rather than being directly involved in them. For example caffeine gives the perception of having more energy and fires up the sympathetic nervous system allowing you to exercise better but does not directly contribute to the movement.",
"I'm sure there would be exceptions, e.g. if the drug is actually consumed by the process e.g. L-dopa, or if it is inactivated at the site of action. There is also a processes called tachyphylaxis which means that the drug isn't eliminated any faster but the body runs out of the chemicals the drug acts on. An example of this would be if you take amphetamine, after a while the neurotransmitters get depleted and the drug seems to lose its effect."
] |
[
"Wouldn't increase in circulation rate lead to more blood going through the liver, more enzyme exposure and faster decomposition? Or might the exercise actually divert blood flow to the periphery and away from the liver?"
] |
[
"I know you can donate your body to science, but what about your death?"
] |
[
false
] | null |
[
"It wasn't just about the legality of voluntary death, but about making sure you cop it while in the tube, which practically speaking means someone pushing a death button, in my mind."
] |
[
"Right, that's what I mean by palliative treatment. Hospice doesn't extend the lives of its patients; it merely provides them with comfort while they decline."
] |
[
"Right, that's what I mean by palliative treatment. Hospice doesn't extend the lives of its patients; it merely provides them with comfort while they decline."
] |
[
"When two people are infected with the same virus, are the t cells in our bodies that deal with the virus the same?"
] |
[
false
] |
I only have a simple understanding of how the immune system works, but I learnt about the lock and key model that describes the way in which t cells operate. From what I know, a specific t cell will attack the virus depending on the antigen (?). If this is the case then would two separate immune systems identify the antigen in the same way and thus would the t cells be the same?
|
[
"Nice to see some immunology on here!",
"No. The concept of V(D)J recombination and there being \"one epitope for one clonotype\" of T cell was soundly struck down a few years ago. I, like you, however, was still taught the same dogma you've been taught. ",
"The clonal selection theory proposes that individual lymphocytes through V(D)J recombination are specific for one, and only one, antigen. For many years the concept of huge numbers of TCRs successfully providing immunity to all foreign peptides in a “one-clonotype–one-specificity” paradigm was accepted. The number of possible epitopes, however, greatly exceeds the number of T cells found within the human pool. A simple mathematical argument demonstrates that 10",
" T cells, a conservative estimate for the total number of foreign epitopes, would require a spleen the weight of a small car. ",
"Mason, therefore, posits that the “one clonotype-one specificity” paradigm is false, rather each T cell is able to respond to more than one antigen. Indeed, he suggests each T cell is required to recognise of the order of 10",
" antigens: a cross-reactive “one clonotype-million specificity” hypothesis should be adopted.",
"This means that when a T cell \"recognises\" a foreign epitope, is activated, and undergoes clonal expansion, it's recognising only 1 of a million possible steric combinations. So if someone else's T cells recognises the same epitope, there's nothing to stop it being a totally different bit of VDJ recombination - and therefore a totally different TCR receptor, and a totally different T cell.",
"Does that makes sense?",
"Edit: Forgot to add the Don Mason paper: Mason, D. A very high level of crossreactivity is an essential feature of the T-cell receptor. Immunol. Today 19, 395–404 (1998). "
] |
[
"B cells and monocytes are the \"professional\" antigen presenting cells (and to some extent dendritic cells, but they're a v small percentage of total white cells). They endocytose and present peptide fragments on MHC classes I and II, endogenous and exogenous respectively. The T cells then recognise the antigens presented by the APCs."
] |
[
"B Cells are the ones doing the antigen recognition, not T cells. I thought?"
] |
[
"Can I always use the Heisenberg uncertainty principle to understand diffraction?"
] |
[
false
] |
What happens in a single-slit diffraction experiment when the slit width "d" becomes narrower than the wavelength of the light? To put the question in more context, when I was an undergraduate I once heard that single-slit diffraction could be understood in terms of the Heisenberg uncertainty principle. The argument goes as follows: Imagine an incident plane wave of light at wavelength "λ" approaching a 1-dimensional slit aperture from the left, which I will define here as the "x" direction. The slit is of height "d" along the "y" direction, and for simplicity's sake is infinite along the z direction. Light must pass through the slit in the form of photons, and the Heisenberg uncertainty principle places limits on these photons' momenta. Specifically, we know that as a photon passes through the slit, its vertical position is known to within an uncertainty of about "d" so the vertical component of momentum, "p_y", is only defined to within a precision of about hbar / d. Now, because the incident light was coming in with wavelength λ, we know that each photon’s total momentum must be roughly 2 π hbar / λ. We can combine the two relationships to give the following relation, d sin(theta) = λ. (sin(theta) = transverse photon momentum / total photon momentum.) This is exactly the condition for the edge of the central peak in Fraunhofer diffraction. My question is this: What happens when the slit becomes narrower than λ? That is to say, what happens when the slit becomes so narrow that a photon passing though it must acquire an uncertainty in transverse momentum that is greater than the photon’s total momentum was to begin with? At least two possibilities come to mind: (a) When the slit gets narrow, light simply cannot get through. This seems reasonable except for the fact that once you close down the slit even a single photon that sneaks through the slit would have to violate the uncertainty principle. Transmittance that is identically zero seems almost as difficult to swallow as a failure of the uncertainty principle. (c) When the slit becomes very narrow, it begins to resemble a cavity where photons can be up-converted to higher energy and momentum. Would this mean that forcing light to pass through a narrow slit changes its color? Thanks in advance for any thoughts.
|
[
"I wouldn't use the uncertainty principle to try to explain anything, to be honest. It's much better to look at the underlying principle, namely that of conjugate operators or, clasically speaking, Fourier transform relationships.",
"For a diffraction experiment, the resulting image in k-space (wave vector space) is the Fourier transform of the slit. Each k vector has a direction and magnitude. If you have the distribution of wave vectors, you can then calculate the image light with this distribution would make on a screen at some distance from the slit. ",
"What happens for a slit is simply that the whole thing gets broader and broader, with the minima going to larger and larger angles, while the intensity decreases due to the smaller amount of light coming through the slit. ",
"Fourier transform relations are much easier understood for frequency and time. Imagine a ",
"beat experiment",
") with two frequencies separated by df. To be able to recognize that there are two lines here rather than one, you need to wait about a full beating period 1/df. If the time you wait is shorter, you could say that it's impossible to resolve the difference between the two frequencies. Are there still two frequencies present if the observation time is too short? Nope, there is a broadened line that depends on the temporal shape of your detection. If you make the time very short, you will hear a click (a signal with a wide frequency distribution), even from a sine wave."
] |
[
"I see the problem now, I'll have to give it some thought. The typical description relies on conservation of momentum and capping the available wavevectors to k (this is done by the relation k_y = |k|*sin(theta)). I've never really thought about how the uncertainty principle applies to this. I don't know if a small slit can cause light to have a wider frequency distribution, which would be implied by a change in |k|. If there is a change in color, it would have to be energy-conserving. ",
"I think the answer will probably something like: the slit itself, or its interaction with the light, must themselves be subject to uncertainty. I'll try to check."
] |
[
"Let me word the question a different way:",
"The Fourier transform of a slit of width = d is a distribution in k_y with standard deviation ~1/d. If d << λ, then the absolute value of transverse momentum for a typical photon passing through the slit is |k_y| >> 1/λ. How do we simultaneously understand this and the fact that a typical photon's total momentum should be given by |k| = 2 pi / λ? It would seem I have just proved that |k_y| >> |k|."
] |
[
"Which flow type cools faster, Laminar or Turbulent?"
] |
[
false
] |
If a copper rod is being cooled by a fan, and depending on its position it can experience both turbulent or Laminar flow, would the rod cool faster if the flow is more turbulent or laminar? The position the rod experiences laminar is closest to the cooling source, so intuitively this would cool faster, but experiment has shown that the further away from the source it is, and the more turbulent the flow, the faster it cools. Am I misunderstanding my results, or what is going on behind the physics?
|
[
"Laminar flow provides heat transfer only through conduction because in laminar flow the air is flowing in sheets with little mixing between them. A way to visualize this is a deck of playing cards. The layer of air that touches the rod is heated. That layer also does not mix with the other layers of air above it. The heat can only be transferred from one layer to the next by contact (conduction). Since the energy transfer rate depends on the temperature difference, the sheet of air gets warmer by the end of the rod and is removing heat at a slower rate than when it first began conducting heat from the rod. The turbulent flow has no sheets. This means that more fresh cold gas will contact the surface resulting in a faster heat transfer rate due to a larger average temperature difference between the rod and air."
] |
[
"Thank you very much for the response. When you say that laminar flow provides heat transfer only through conduction, why is this? What you have said definitely makes sense in terms of my results. I'm new to the heat transfer stuff, and just the sheer number of angles you have to approach everything from and the volume of equations involved with all the dimensionless numbers and what not has just left me overall confused."
] |
[
"Thank you very much for the response. When you say that laminar flow provides heat transfer only through conduction, why is this? What you have said definitely makes sense in terms of my results. I'm new to the heat transfer stuff, and just the sheer number of angles you have to approach everything from and the volume of equations involved with all the dimensionless numbers and what not has just left me overall confused."
] |
[
"If an object is colored in a color outside the visible light spectrum (ex: ultraviolet, infrared) would that object be perceived as invisible to us?"
] |
[
false
] | null |
[
"No. Objects that do not reflect light in the visible spectrum appear black."
] |
[
"So does that mean anything that is black is actually colored a color outside the visible light spectrum? How can we tell if a black object is colored UV or infrared or any other invisible color?"
] |
[
"An object that appears black to us may reflect light in wavelengths outside of the visible spectrum. We would need some sort of sensor to measure this that is sensitive in that range (an infrared or UV camera for example). ",
"In reality, no object perfectly absorbs all wavelengths in the visible spectrum."
] |
[
"What is the heaviest naturally forming element in the universe?"
] |
[
false
] | null |
[
"You don't need an estimate. Its Plutonium. No elements heavier than plutonium are known to occur naturally. That said, natural plutonium is so rare, for a long time it was thought to be only artificial. Uranium is the heaviest element created in appreciable quantities."
] |
[
"Wikipedia, citing Emsley's \"Nature's Building Blocks\", suggests that elements up to ",
"Fermium",
" were produced naturally in the Oklo natural reactor.",
"I've also read elsewhere that some supernova could produce elements as heavy as Californium or Curium."
] |
[
"According to ",
"THIS",
" blogpost on Scienceblogs, the one study that detected naturally occurring plutonium is \"not universally accepted\". His argument is that while plutonium could be created naturally, the supernovae that supplied our solar system with its heaviest elements was not energetic enough to do so, which is why uranium is considered the heaviest (on Earth). The post is worth a read, in any case."
] |
[
"Do insects have thoughts or is it all pre-wired actions?"
] |
[
false
] |
[deleted]
|
[
"What's really gonna bake your noodle later is when you ask yourself \"When I see a predator and think 'I should hide because that thing can kill me', is that because ",
" wired that way?\".",
"So, yes. The process by which an insect determines a reaction to an aversive situation may involve fewer steps than a more complex animal's, but pretty much anything any animal does is because of its wiring. Some wiring is just more complex that other wiring."
] |
[
"I am not an insect (to my knowledge), so I can't tell you for certain. FYI a conscience is not the same as consciousness; I doubt insects have strong moral leanings. And consciousness is hard to define, much less measure.",
"You're asking an interesting question, but the problem with these kinds of questions is that we all act like we know what consciousness is when really, we don't even know the definition for the thing we're asking about. If I asked you to prove you were conscious, how would you do it? We have things like the ",
"mirror test",
" to demonstrate self-awareness, but is that the single determinant of consciousness?",
"Anyway, insects probably have richer mental experiences than we give them credit for, but at the end of the day, yeah, they do appear to be pretty simple IO devices."
] |
[
"But then consider a virus. Is the worm any more \"special\" than a virus? The worm is obviously more complex, but they both have the same \"thoughts;\"",
"I would argue that this isn't true. Viruses work, respond to their environment, and reproduce on largely a protein/nucleotide level. A worm has an extra level of additive, emergent behavior at the level of cells, synapses, circuits, and pathways that exhibit an entirely different phenomenological properties than viruses. Viruses do not respond to external stimuli behind simple conformational changes, do no establish proton gradients to support cellular processes, and do not self replicated. They are not alive and do not care about dying, just like an additive reaction in organic chemistry cares that it goes to completion.",
"When it boils down to it - like you said, stronganawful - aren't we all wired that way on a very basic level?",
"No, emergence is important. If you're interested, one of the clearest arguments about emergence and its relation to reductionism can be found in ",
"this paper",
". More isn't just more, it is also ",
"."
] |
[
"If a racquetball and a golfball are hit with a golf club against the wall of a racquetball court, which one will have the most speed/force when returning from the wall?"
] |
[
false
] |
So here is the setup. you have a golf ball and a racquetball on separate golf tees inside a racquetball court. They are struck with a golf club at the wall and bounce back. My question is which would be traveling at a greater speed ad have more force. My guess is that the answer has something to do with the bounciness (elasticity) of the balls. I would think that the racquetball would have more speed/force after hitting the wall because the golfball is much less elastic, causing it to transfer most of its energy to the wall. Correct if I'm wrong. I guess I derived this question from the "Jackass" boys. We were wondering which would hurt more, being struck by a racquetball or a golfball. The link to the video is posted below(Sorry for any crude language)
|
[
"The golf-ball collision is ",
" more elastic",
" than the raquetball one.",
"The raquetball being squishier actually has nothing to do with its elasticity, and everything to do with it's (lack of) stiffness. Both balls are almost completely elastic and return almost perfectly to their original shape after being deformed. But since the golf-ball is less squishy, it deforms less, and loses less energy to heat, therefore it \"springs\" back into its original shape with a greater fraction of the original deforming force, which makes the collision more elastic."
] |
[
"From an energy point of view it is correct that golf-ball would be worse for the person getting hit. From a force point of view (mass * acceleration) it is also worse for the person getting hit as the racket ball will decelerate over a greater length than the golf ball.",
"[note OP that since they have the same momentum (velocity * mass) the racket ball will be moving slower but have more mass]",
"The most important thing to look at to decide what is worse in this case (as they will be so similar in energy) is actually the pressure (force/area) imparted. Since the golf ball is acting on a smaller surface area, the force will be less evenly distributed. This will cause more damage and pain. It is like getting stabbed by a knife as opposed to spoon. Or perhaps more accurate to the different masses and speeds in the question posed, getting shot with a super-sonic bullet as opposed to getting shot with a sub-sonic beanbag.",
"Either way in every analysis you can tell your friend golfball=worse."
] |
[
"Are we assuming that the golf ball will rebound perfectly off of the wall without damaging the wall? If you were to actually try this I believe that in most cases a golf ball would cause much damage to the wall and lose most of it's rebound through this damage."
] |
[
"What is the probability of TCP failing to detect an error?"
] |
[
false
] |
I am starting to learn about CRC and the TCP/IP stack protocol. Am I correct in thinking that, for as little as it may be, there is still a possibility that all of the error detection methods throughout the layers fail to discover a particular sequence of wrong bits? If so, is it an issue that programmers should take into consideration, when dealing with highly critical data?
|
[
"The TCP checksum isn't meant to guarantee anything, it's a pretty weak test, especially when you're talking about massive amounts of data. ",
"This",
" paper is pretty cool. Mostly you're relying on the fact that your data transmission protocols are pretty high-fidelity, so your base error rate is low, and therefore the probability of even needing a checksum is low, so the probability of checksum failure is low."
] |
[
"I can't seem to access the paper, though I found ",
"this",
" web page describing the phenomenon. It actually cites your source, and estimates that",
"between 1 in 16 million and 1 in 10 billion TCP segments will have corrupt data and a correct TCP checksum",
"So that is actually quite a lot, isn't it? Anyway, is it standard procedure to add an extra level of error detection on top of tcp? I always hear saying that TCP guarantees an error-free connection. "
] |
[
"Absolutely not - you can't guarantee an error-free connection, you can only guarantee one to a certain tolerance (probability of failure). In any case, not all bytes are created equal, so the consequences for an error rate of 1 in 10 billion is not necessarily that high. But if you've ever downloaded an ISO, you know that data corruption is an issue, which is why an MD5 digest (or the like) is useful - the odds of that failing are astronomically low. For high-fidelity operations you can layer this kind of checking on top of your transmission, but this has much greater computational overhead.",
"Check out ",
"this",
" link about an Amazon S3 outage due to a single-bit error in a critical place which wasn't checked with MD5."
] |
[
"During a severe asthma attack, why can't the patient resolve it with endogeneous release of epinephrine?"
] |
[
false
] |
During exercise-induced asthma, asthmatics can 'treat' bronchoconstriction while they are exercising due to epinephrine release. But when they stop, they can have an attack minutes later because there is no further release of epinephrine. My question is: why can't these patients release epinephrine because they are panicking/in a high stress situation, especially one that they know can cause them to die? Is this because they 'run out' of epinephrine in the adrenals?
|
[
"Doctor here.",
"Many asthma medications are Beta-2 receptor agonists--including albuterol. ",
"Beta-2",
" receptors are responsible for the smooth muscle relaxation that achieves symptomatic relief in asthmatics.",
"Epinephrine is non-selective and can cause myriad effects that differ based on high vs. low dose administration. In short, it CAN be used in an emergency, but will cause many undesired effects. Physiologically, the same thing is true. We will experience an increased heart rate and blood pressure which will both contribute to an increase in the oxygen demand of our cardiac muscle... creating even more stress on the already taxed respiratory system. "
] |
[
"As an asthmatic that has been struggling with it all my life, I'm a bit intrigued by this as well. ",
"Something I'm curious about as well is why Cold air seems to help my asthma significantly. If I'm having a bad attack, and I'm somehow without my inhaler, going outside and taking big gulps of fresh cold air really clears me out. (Sorry, don't mean to hijack you just piqued my interest a bit!)"
] |
[
"We will certainly use adrenaline infusions to treat asthma, but they are not first line, and as Shinkei says, more selective beta 2 receptors stimulating drugs are normally used first. However, in a severe attack even these may not be effective. Thats because part of the problem in asthma is not just the airways narrowing, but the lining of the airways becoming inflammed and swollen, which makes it even harder to get air in. Thats why, in bad attacks the most important drug is intravenous steroid, to to treat this inflammation. They may take hours to days to work though, so the beta agonists are also used for their immediate effects. They, and adrenaline, have no anti inflammatory action though, so alone they may not be enough to treat a bad attack."
] |
[
"How much potential energy could be produced using wind and solar means in the US if we took advantage of all the empty space?"
] |
[
false
] | null |
[
"that, combined with geothermal (properly harnessed) would make charging for energy obsolete as it would be so plentiful and ubiquitous. We're talking in the order of Zeta joules (the whole earth only uses about 1/2 a Zeta joule per year. "
] |
[
"I can't speak for Solar, but there were two studies back in September - one from the Carnegie Institution for Science, which speculated that there's enough wind in the world for trillions of watts of power from Wind alone - 10 times the world's current 'need'.",
"However, the catch was they would need 100 new turbines for every currently existing one, so the space needed would be probably take up a lot of the 'spare room' in the US.",
"But, the bottom line is, according to these two studies: Yes, you could run the whole planet on wind if we simply built thousands of wind farms.",
"Sources:\n",
"News Article",
"\n",
"One of the Studies"
] |
[
"The limitations to complete penetration of renewable energy are technical and economic. There is absolutely enough renewable energy potential capacity, even using current technologies, to meet global energy demands. The obstacles are cost and technical feasibility (e.g. if you build a giant grid composed of highly-variable generation sources, the power electronics necessary to regulate that grid become very complicated).",
"Saul Griffith's ",
"TED talk",
" is a nice discussion of the total potentials for renewable energy of various sorts (the part I'm referring to starts at about 2:45, but the whole talk is interesting)/"
] |
[
"Is there any difference between mass granted by the Higg's mechanism versus mass granted by the Strong force?"
] |
[
false
] |
Forgive my terminology, but as I understand it, the Higg's field creates mass for elementary particles, but the vast majority of mass we see is a result of the strong force holding together bundles of quarks and nucleons. How is it that these 2 seemingly different mechanisms result in something that on our scale look like exactly the same thing? Does mass created by the strong force interact with the Higg's field? Does mass created by the Higg's field interact with the curvature of spacetime?
|
[
"Is there any difference between mass granted by the Higg's mechanism versus mass granted by the Strong force?",
"No, there is no difference.",
"How is it that these 2 seemingly different mechanisms result in something that on our scale look like exactly the same thing?",
"Because both mechanisms are doing the same thing: confining energy. The strong force confines the energy of particles with color charge into a small amount of space, and the Higgs mechanism confines the energy of particles that interact with the Higgs into a small amount of space. In both cases, mass essentially results from the relation E=mc",
" , by virtue of the respective forces confining energetic particles and thus giving them some average rest frame. ",
"An advanced undergraduate-level exercise, which might help, is to show that a photon trapped in a massless mirror-box has an effective mass given by E=mc",
" . It doesn't matter what forces hold the mirror-box together; what matters is that energy is confined. "
] |
[
"Photons in a box are a good place to start because they're simpler to picture than the Higgs mechanism. Move the mirrored box and the photon bounces off a moving mirror, blueshifting it. This costs energy so of course you get a force opposing your attempt to move the box.",
"You find that any way you look at it the box now has mass. "
] |
[
"It's that simple all along? I've never heard that analogy before but it makes the idea of \"giving mass\" so much more plausible."
] |
[
"When would you clean with, say, vinegar or borax instead of dish soap or bleach or alcohol?"
] |
[
false
] |
What are the properties of common solvents used to clean things, and what about them makes one better or worse at certain jobs than another?
|
[
"Some of the substances you mention are solvents, and others aren't. ",
"Bleach and vinegar (acetic acid) chemically attack anorganic and some organic substances and destroy them. I don't know how Borax works. ",
"Dish soap is a surfactant, it is a long molecule with one polar (hydrophilic/lipohobic) and one nonpolar (hydrophobic/lipophilic) end. One end attaches to fat and the other to water, allowing the water to engulf the fat and rinse it off. ",
"Water itself is a polar molecule thanks to its 104.5 degree angle structure. When it acts as a solvent, other polar substances such as salts will happily dissolve in it. Nonpolar molecules such as triglycerides (fat) will not dissolve very well. ",
"On the other hand there are nonpolar solvents such as alcohol, acetone, diethylether. These are great to dissolve nonpolar substances but not polar molecules. ",
"Strangely enough, water and e.g. alcohol will happily mix with each other and then you can dissolve all sorts of things, up a point. This explains why wine and other alcoholic beverages can have such a complex taste - both solvents combine to dissolve more aromatic molecules. ",
"So you really have to pick the correct substance for the job. For permanent marker, try a nonpolar solvent. For fat, it's soap and water. Vinegar works well against calcified areas such as taps. Bleach will, well, bleach stuff."
] |
[
"Great answer, thanks! I'm off to imbibe some complex solvents😁"
] |
[
"In addition to the above, vinegar works as a decalifying agent because much of the crust that develops on sinks and tea kettles is carbonate salts, which are very soluble in acidic solutions. The acid used doesn't have to be acetic acid, but it's readily available, and acetate is itself highly soluble, so it won't precipitate out of solution when the acidic vinegar solution and the basic carbonate/bicarbonate neutralize each other. ",
"Also, as you may well known, alcohols (the commercially available forms being ethanol and isopropanol) are also good for disinfection. And unlike vinegar and bleach, they don't need to be washed off surfaces after application, as they just evaporate without leaving behind any salts."
] |
[
"Prior to the existence of pollinating insects, how did plants reproduce sexually?"
] |
[
false
] | null |
[
"Pollen is a relatively recent invention. It evolved around the same time as the seed. The first types of pollination were almost certainly by wind -- there is clear evidence for this from fossil plants (their anatomy and morphology is consistent with wind pollination).",
"Your question is more broadly about sexual reproduction. ",
"Pollination is just one means of bringing sperm -- indirectly -- to an egg. In plants this process (sperm to egg) is indirect, because the first stage of sex produces a distinct plant generation that is haploid, meaning that it is a multicellular generation with one chromosome set instead of two (just like sperm and eggs; but this haploid generation produces the sperm and eggs). ",
"In many seedless plants like mosses and ferns, these multicellular haploid generations (which are produced by unicellular sexual spores) are free-living on (or in) the soil. The soil is where sperm are released and they swim through water in the soil to the egg, usually in another haploid plant, to fertilize them there and produce a new diploid generation.",
"One evolutionary innovation in seed plants is that the haploid generation that produces sperm, which is now reduced to a few cells (all wrapped up inside the pollen grain), travels through the air (sometimes water) using a pollinator, or the wind. ",
"Its 'partner' haploid generation, which produces one or more eggs, is wrapped up in the parental ovule (= pre-fertilized seed). In flowering plants the ovules (seeds) are further wrapped up inside parental tissue that later develops into fruit. When pollen grains arrive they have to produce tunneling pollen tubes to deliver sperm to eggs in ovules. ",
"In a few seed plants, like cycads, the sperm are released inside the ovule and swim directly to the eggs there.",
"Edits: Grammar!"
] |
[
"Thank you for saying hypothesis instead of theory. It's so sad when people interchange them."
] |
[
"Prior to evolving for specific insect types for pollination (eg. corollas for insects with long tongues), plants pollinated by wind. Actually some plants still do that today!",
"It is probable that brightly coloured flower petals that are attractive to insects evolved from dysfunctional stamen (the male reproductive structure) since along the evolutionary road plants had to keep the pistils (female reproductive structure) close to the stamen for insect pollination to be effective. Of course, this is just a hypothesis, but I read it from a source which I will link later if I can find it :)"
] |
[
"What is the math behind mining bitcoins?"
] |
[
false
] |
What math does the computer do exactly to mine bitcoins? How do they make it to be harder and harder to mine and calculate so that you always end up needing more processing power? Why was it once relatively easy and now it is almost impossible to do decent mining with a desktop computer?
|
[
"What math does the computer do exactly to mine bitcoins? ",
"To \"mine\" coins you find an input to the SHA-256 hash function that produces an output that is less than some specified value. Since SHA-256 is a cryptographically secure hash function there is no way to predict the inputs that will produce a particular output. All you can do is try input after input until you find an input that produces a small enough output. Then you report your finding to the blockchain and you are given a reward for your computational effort. ",
"ow do they make it to be harder and harder to mine and calculate so that you always end up needing more processing power? Why was it once relatively easy and now it is almost impossible to do decent mining with a desktop computer?",
"Bitcoin is designed so that the rate at which blocks are mined is constant. The way it does this is by adjusting how small the output of the SHA-256 hash function needs to be. If a whole lot of people are working hard then simply make the desired output smaller so its harder for everybody to actually mine a block. Because so many people are using custom hardware now the protocol has adjusted to compensate. This means that mining a block is much more difficult than it was a few years ago. "
] |
[
"The central calculation (also known as the \"",
"proof of work",
"\") involved in Bitcoin mining is the ",
"SHA-256",
" hash function (technically, two calculations of the hash).",
"When you mine BTC, what you're technically trying to do is create a new ",
"block",
". This is done by repeatedly hashing the previous block, along with a random value called a ",
"nonce",
", which changes with each attempt. The Bitcoin protocol will only accept the new block if the integer value of the resulting candidate hash is less than a certain amount (or, stated slightly differently, contains a certain number of leading zeros). This is where the ",
"difficulty",
" comes in: the lower the target value, the higher the difficulty, and the more hashes must be computed before a new block is successfully mined. The current difficulty value is adjusted every 2016 blocks to ensure that new blocks are mined approximately every 10 minutes.",
"Once a miner successfully computes a hash below the current target difficulty value (and the Bitcoin network confirms it), a new block is created, with its first transaction being the 25 BTC reward credited to the miner who \"discovered\" it. When Bitcoin was first launched back in 2009, there were FAR fewer people mining, and GPU/ASIC cluster mining didn't come on the scene until much later, so therefore the difficulty was much, much lower, since few computations were required to find the new block hashes.",
"I left some links in the above description to the relevant articles at the ",
"Bitcoin wiki",
", if you want to read more about how the protocol works."
] |
[
"The reward and benefit is having mined the coin. It becomes \"your\" coin and is entered into your Bitcoin wallet. Some places will accept Bitcoin as currency. It has value because the people who deal in it mutually agree it has value."
] |
[
"Why does a photon have an electric field?"
] |
[
false
] |
Or rather how does it have one?
|
[
"I think discussing the reverse question is more illuminating: ",
" ",
"From electromagnetic theory, we know the Lagrangian (an incredibly compact way to describe motion and energy in physics) is for chargeless situations, ",
"ℒ = -¼F",
"F",
" ",
"where 'i' and 'j' cycle through time, x, y z, and, ",
"F",
" = (d/dx",
")A",
" - (d/dx",
")A",
" ",
"where we find the kernel of physics we are interested in. We want to know about A",
" which is our electromagnetic four-potential from which flows the electric and magnetic fields. In short through a complicated relationship of how A",
" changes, we get the equations of motion for the electromagnetic field. In classical electromagnetism, this is all find and dandy. We can figure out the electric and magnetic fields of wires and magnets. The properties of the four-potential yield us Maxwell's equations. From this we even get a classical wave equation that describes classical light! ",
"(d/dx",
")(d/dx",
")A",
" = 0",
"Light then becomes electromagnetic fields which do not have charges around them behaving in a way that obeys a wave equation. This light is continuous though, you can always have a little more or a little less or it, there are no restrictions the dynamics of this wave outside the wave equation.",
"However, something interesting happens when you try to ",
" electrodynamics. The interesting thing is that to describe behavior, you're going to get terms which describe discreet changes in the electromagnetic field. Essentially, a restriction occurs that doesn't allow the electromagnetic field to behave completely arbitrarily. Another way to think of it is to picture the sound modes of an organ pipe.",
"These restricted objects which contribute to motion in electromagnetism are called photons. So that is why electromagnetic fields have photons."
] |
[
"The photon is nothing but a particular configuration of the field; a ripple in the field, if you will."
] |
[
"More precisely, the field is ",
" photons."
] |
[
"At what point does motion become sufficiently microscopic such that it becomes tempurature?"
] |
[
false
] | null |
[
"A motion contributes to the temperature when it is in thermal equilibrium. Size doesn't matter in-itself. For translational motion, it will be in thermal equilibrium when it's randomly distributed. That is, the net motion of an object does not count towards its temperature. It doesn't matter if something is standing still or moving at 1000 m/s. (and why would it? whether it's moving depends on what you're measuring relative)",
"When a moving object slams into a stationary one and comes to a stop, the kinetic energy of its motion gets redistributed and randomized, and ",
" the temperature increases. "
] |
[
"The particle level for most familiar substances is molecules (or atoms for pure elements).",
"To me that suggests a certain amount of independence from scale, which is what I think the OP is trying to ask about. Are differences in temperature manifest at a subatomic / quantum level?",
"I'm open to being corrected, as I'm no scientist, but when OP asks \"how small\" (edit: \"sufficiently microscopic\"), doesn't that imply a certain amount of continuousness in the scales at which phenomena are manifest? I mean, if those scales are discreet, then we can look at temperature as being strictly on the molecular level, although we can see its effects at the \"next level up\", the level we're accustomed to living in, here on the surface of earth, where molecules are clumped into objects like \"atmosphere\", \"ground\" and \"body\". Does our solar system have a \"temperature\"? Is it affected by us moving around in all our directions?"
] |
[
"Then they're oversimplifying to the extent of being wrong and you're taking some very introductory level courses. Temperature is defined by dU/dS = 1/T, and encompasses all energetic degrees of freedom. If you heat something enough, electronic excitations begin to occur. Does that mean the temperature drops as energy goes into that degree of freedom? Of course not. It means that the electronic state is part of the temperature. If you heat a magnet past the Curie point, and energy goes into re-arranging the spin states, does that lower the temperature? Again no, that means the magnetization state is actually part of the temperature.",
"It is the case that at room temperature, almost all the thermal energy in most substances happens to be in the kinetic degrees of freedom. But it is not how temperature is defined. The classical thermodynamics predates statistical thermodynamics; temperature was defined before it was even accepted as fact that things were made up of atoms."
] |
[
"Why did the Apollo astronauts not just parachute from space directly? Why did they have to use the heat shield and then open the parachutes? And could someone conceivably skydive from the ISS?"
] |
[
false
] |
It seems like it would be possible to just "float" down from space on a parachute...
|
[
"The ISS is travelling at around 28000km/h (17000mph) relative to the Earth's surface. To land on the surface, that kinetic energy needs to be shed. The spacesuit (EMU) plus manned manoeuvring unit (MMU) have a combined mass of around ",
"190kg",
" (420 lbs). Combine this with an 85kg (185 lbs) astronaut and you are up to 275kg. The kinetic energy that needs to be shed is:",
"E = 0.5 m v",
"E = 0.5 * 275kg * (7750 m/s)",
"E = 8.3x10",
" J",
"E = 8 GJ",
"This is enough energy to run a 60W bulb for over 4 years! Let's pick a time period of 10 hours (",
"shuttle re-entry is around an hour",
") to dissipate this energy, and assume it is dissipated evenly over this period to the atmosphere. The power output for the process is:",
"P = 8x10",
" / (10x3600)",
"P = 229 kW",
"A room heater is around 2kW, so this power dissipation is the equivalent of wrapping 115 room heaters around the suit and leaving them running for 10 hours straight. So to do this is an hour is the equivalent of wrapping the spacesuit in over 1000 room heaters.",
" Assuming you get a nudge to push you into the denser atmosphere, you have to shed 28000km/h (17000mph) by collision with the atmosphere. This is a toasty process.",
" Formatting, TLDR, and last sentence added."
] |
[
"And could someone conceivably skydive from the ISS?",
"If you're on the ISS, then you are in orbit. Jump from it, and you'll continue to orbit the earth for decades."
] |
[
"Very true! That increases the power dissipation requirements by about an additional 10%."
] |
[
"How dangerous is uranium/uranium oxide to handle?"
] |
[
false
] |
At 38:55 of the below video, it is said that people wear gloves when handling uranium to protect the uranium from being contaminated, rather than wearing gloves to protect themselves from the uranium. It is said that since uranium's half-life is in the billions of years, it isn't that radioactive. This sounds hard for me to believe, as I thought uranium was very dangerous to handle. Is it true that uranium isn't that radioactive? That gloves are worn to protect the uranium, and not the human? Also, is uranium oxide - which is what the pellets in the video are - the same as uranium in terms of safety?
|
[
"Uranium in its natural state is not particularly radioactive. U-238 is the most common isotope in Uranium ore. U-235, the more radioactive isotope used in enriched and weapons-grade uranium only accounts for about 0.7% of natural uranium ore. But even U-235 isn't terribly dangerous from a radiation standpoint. The larger concern when handling these materials is their inherent toxicity. For this reason they are always handled with gloves and similar protection. One would have to spend a long period of time in close proximity to a very large quantity of uranium in order to receive a dose of radiation that was any more notable than the typical background radiation we receive in everyday life.",
"The perception of uranium as highly radioactive and dangerous comes from two sources. First, it is often thought of interchangeably with plutonium in this regard. Pure plutonium is significantly more radioactive and thus should be handled with much greater care, but even then, I believe the principle concern is toxicity, not radioactivity. Secondly, and more importantly, irradiated nuclear fuel is ",
" radioactive, and quite dangerous to interact with. This is probably what you're thinking of. Enriched uranium that has spent time as fuel in a nuclear reactor has undergone fission, and been bombarded with particles, all creating numerous other materials within the fuel that make it very radioactive. Spent fuel like this is what we refer to when we talk of \"nuclear waste\" and it ",
" quite dangerous. This is the material that conjures up ",
"images of technicians",
" in bulky radiation suits, daintily holding on to glowing metal rods with a pair of tongs to avoid contact."
] |
[
"I have never seen someone in a \"radiation suit\", and I work at a nuclear plant. What I have seen is people in anti-contamination clothing, which basically protects their skin and clothes from getting radioactive particles on them. Consider that typical lead shielding is one inch thick, and to give you 12 square feet of that would be 700 pounds. Instead, the anti contamination clothing stops alphas and betas, and you just get exposed to the gammas. It's a fact of life working at a nuclear plant, but if reddit loves to teach me anything, at least I'm not working at a coal plant!"
] |
[
"Purified uranium metal or uranium oxide is chemically toxic (like lead) but not very radioactive. You can handle it. Don't eat it. Don't fill your house with it. But it's not very radioactive. Handle it like you'd handle lead — wash your hands after touching it, don't vaporize it and breath it in, etc. Uranium oxide is just a convenient way to keep purified uranium — it is a chemical compound of uranium and oxygen.",
"Uranium ore, which is what you get out of the ground, is a mix of a lot of things including uranium daughter products that have been being produced for millions of years. Some of those are very toxic and radioactive indeed (e.g. radon and its daughter products, which include polonium). So uranium processing facilities (e.g., mills, which turn the ore into oxide), mines, and so forth need to have really careful ventilation and handling if you don't want people to be increasing their long-term chances for cancer. You don't want to build your home over uranium ores (or mine tailings) without checking for radon gas accumulation. Some of these effects are complicated and synergistic — your chance of getting lung cancer from radon is pretty low by itself, but goes up dramatically if you smoke around the radon, for example (because you are dragging the particles deep into your lungs). "
] |
[
"Trying to learn about ultrasound and I get that sound is reflected at an interface proportional to the difference in acoustic impedance between the two materials but what I can't find is a physical explanation for why that would be the case. Can someone help?"
] |
[
false
] |
I find it especially weird that it works in both directions equally, for instance nearly 100% of sound is reflected going from air to solid AND solid to air. Why??
|
[
"In one dimension, you can consider that your substances are a bit like a Newton's Cradle. Air has very light balls on long strings, a solid has heavy balls on short strings. It's a bit of a simplification, but the math comes pretty close to being a discretised version of the wave equation.",
"If a soundwave comes from air into a solid, it's like a light ball hitting a heavy one, in an elastic collision. Conservation of momentum means that the light ball has to bounce back pretty fast, while the heavy ball only starts moving slowly. Most of the ",
" of the wave has been reflected into the string of light balls.",
"Vice versa, if a heavy ball hits a light ball, the light ball is bounced away pretty hard, but the heavy ball barely slows down. This allows it to swing way out on its string, and then return with almost as much energy as it started out with. Again, most of the ",
" of the wave is reflected (although the wave in the less-dense medium has more amplitude than the original wave)."
] |
[
"Because of the difference in impedance the waves will travel at different speeds in the two materials. Given this, and the fact that there has to be continuity of the wave fronts across the boundary separating the two materials, a reflected wave must exist. If it didn't then there'd be an unexplained discontinuity in the wave fronts. This also explains why refraction of the wave fronts occurs."
] |
[
"That's an awesome explanation, thank you!"
] |
[
"How safe is handling a radioactive fragment of Chernobyl's nuclear fuel with bare hands? (video inside)"
] |
[
false
] |
In video, the girl finds what is purportedly a radioactive fragment of Chernobyl's nuclear fuel. She handles it with her bare hands and even takes it home. Is it safe to handle this with bare skin? If not, what protective gear should have been worn? What if the fragment was eaten or inhaled? Thank you rennovak for the additional questions: What effect does it have, if any, on the devices like the laptop, mobile phone etc? Is this fragment dangerous only from a nearby position or could my whole building be in danger if I would to take it home and keep it?
|
[
"First off, I would be highly skeptical of any YouTube video claiming to have found something like that. It is easy to make stuff up on the internet. ",
"But let's assume that the video is accurate: she claims the source she found has a contact dose rate of several Sv per hour. It seems like the source is mostly alpha and beta decay (short range charged particles) or low-energy gamma, since the dose rate is so much lower when the source is in the ground (2 uSv/hr). An alternative would be something like cesium or cobalt which emits a more energetic gamma ray that can penetrate farther through the ground.",
"We use a similar radioactive \"seed\" in cancer treatment, for a procedure called ",
". Depending on what the exact isotope is, when we handle these sources we wear gloves to avoid having the isotope stick to our hands, and sit behind a small leaded glass panel to shield our torso from exposure. The hands are fairly radiation-insensitive, so you don't need to shield them nearly as much. Alpha particles are stopped by a few cm of air, and beta particles are stopped by a few cm of dense material like water or dirt.",
"So ",
" the video is accurate and ",
" that source is actually emitting several Sv/hr at contact, one would expect to see burns on the hands (very similar to sunburn) after handling the source for around an hour. Handling it for short periods of time isn't the smartest thing, but it probably won't lead to any immediate harm.",
"From other parts of the video, it seems like the source is well-shielded by simple materials. So I doubt there was any real danger to any other occupants of a building that this source was in. If the source is shielded by a few centimeters of dirt, then the radiation detected by someone many meters away through walls will be negligible."
] |
[
"The girl in the video posted a gamma ray spectrum of that very piece of fuel on Fusor.net, an amateur Fusion/radiation discussion board. ",
"The thread and discussion can be found here.",
"That individual piece wouldn't cause acute whole body harm, but I wouldn't want to sleep near it nor would I neglect to wash my hands after handling it. In the thread I linked, she shows the surface exposure rate at 82 mSv/hr (8.2 rem/hr), which is extraordinary for such a tiny piece (probably even higher due to the paralyzing effect it would have on the GM tube). The LD50 for radiation exposure is roughly 5 Sv (500 rem) delivered over a few hours. If it were a fist sized chunk, I'd want to be very far away.",
"Edit: updated with more info"
] |
[
"You can read an AMA I did ",
"here",
". I work in a radiation oncology clinic."
] |
[
"When I'm hungry, I smell food better. Is that my brain filtering information differently or is it my nose being \"more active\"?"
] |
[
false
] | null |
[
"I don't experience this, but nonetheless it must be the former (your brain filtering the information differently).",
"There is no difference in the number or type of odor receptor cells or the \"activity\" of your olfactory epithelium in the roof of your nose between times when you are hungry and times when you are full. I am also going to go ahead and assume that your breathing patterns do not change (i.e. breathe more through your nose when hungry and mouth when not hungry)."
] |
[
"My best guess: an evolutionary defense mechanism. When you're hungry, your brain focus more resources towards finding nourishment. It makes processes that would benefit you finding food in the wild a priority. A heightened sense of smell during hunger likely benefited a primitive human in search of food in the wild. (Not certain on this, please correct me if I'm wrong."
] |
[
"As a neuroscientist, this is moreorless correct."
] |
[
"Is it possible (theoretically) to cause nuclear fusion through a purely kinetic method, or in layman's terms smash two objects together really hard to fuse them?"
] |
[
false
] | null |
[
"Yes, this was first done by Ernest Rutherford, who combined helium and nitrogen into oxygen."
] |
[
"Yes, this is routinely done using accelerators."
] |
[
"These are generally fixed-target machines rather than colliders. So the beam is shot onto a stationary target, and fusion reactions happen in the target."
] |
[
"Explain to me, in a nutshell, what Quantum Superposition is."
] |
[
false
] | null |
[
"First, you have to understand the concept of quantum states. Let me give you an example:",
"Take an ordinary photon. Any photon. And now this photon passes through a vertical polarizing filter. Now, there are two states that this photon can be in: vertically polarized, or horizontally polarized. If it's vertically polarized, it will pass through the filter just fine, but if it's horizontally polarized, it will get absorbed. These are the two quantum states of the photon. If you shine an unpolarized beam of light through a polarizing filter, you will notice that the light is only half as intense when it passes through. This is because half the photons are blocked, and the other half are transmitted.",
"Lets keep following this light. You know that all of the photons in it must be vertically polarized, since it just went through the filter. If now, you put a horizontal filter over it, you won't be too surprised to discover that none of the photons make it through.",
"What happens, though, if instead you put a filter at 45 degrees to vertical? Well, as it happens, half of the photons pass through again, and now your beam of light is polarized 45 degrees to vertical. This is because a vertically polarized beam of light can be described as a quantum superposition of photons that are either 45 degrees, or 135 degrees from vertical. The photons that are 45 degrees pass through the filter, while those at 135 degrees are absorbed. Each individual photon has a 50 percent probability of being either one, and you can't know which are which until they actually pass through the filter.",
"So, if this illustration helps at all, a quantum superposition is where a system can be described as a sum of different possible states, weighted by their probabilities."
] |
[
"In any quantum mechanical system, the state of the system is described by its wavefunction. This was the insight gained by the most important tool in quantum mechanics: the Schrödinger equation, whose solutions, given initial and boundary conditions, describe the probability distribution of observing the system in a certain position, energy, etc. If you think of music being played out of a speaker, you hear the sum of all the waves on top of each other that create the harmonic texture of the song. This is a superposition of sound waves that you hear. The wavefunction, similarly, can be a superposition of many particular wavefunctions, with one very important difference: you cannot observe a quantum superposition directly, you can only infer it from the solutions to the Schrödinger equation given initial and boudary conditions. The instant you observe the system, the wavefunction \"collapses\" into a single definable state. How you interpret this collapse and what causes it is much of a mystery to a lot of physicists, but there are several suggestions: ",
"http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics#Comparison",
" (not 100% accurate but gives some idea). To put it simply: quantum superposition is the sum of all possible states of a quantum mechanical system."
] |
[
"Superposition is counter-intuitive, but not that mysterious in the formalism of quantum mechanics. The possible states of a quantum system are often characterised as \"directions\" in Hilbert space. The state of a given system might be a direction that can be written as a sum of two other \"directions\". It's analogous to the direction \"north-east\" being interpreted as a superposition of north and east. Schrodingers cat, for example, is pointing in a direction that is a superpostion of the |dead> direction and |alive> direction. "
] |
[
"How small a particle can be effected by magnetism?"
] |
[
false
] |
What is the smallest individual particle that can be manipulated by magnetism? Would magneto be able to individually manipulate individual iron molecules?
|
[
"Mass and volume have absolutely no effect on magnetic force. Magnetic force is proportional to charge, strength of magnetic field, and velocity of particle. An ideal particle with no mass and no volume could still be affected by magnetic force. Yes, theoretically magneto could manipulate individual particles of iron."
] |
[
"An electron is the smallest charged particle, and therefore the smallest particle that can be affected by magnetism. Magnetically deflecting electron beams is how CRT monitors and televisions work."
] |
[
"Electrons are affected by magnetism, as was mentioned. There are hypothetical particles called axions that are about a millionth as massive as electrons, which would interact with magnetic fields."
] |
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