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[
"Can you help me identify this bone I found my dog chewing? I think it is a humerus bone."
] |
[
false
] |
From doing a simple search for bone images, I am guessing it is the bottom part of the Humerus bone. But i have no idea which animal and if it is indeed part of the Humerus. I would like to have an expert weigh in. Here are the pics.
|
[
"I am no expert, but it looks cut and based on my Asian grandparent's cooking, I would say it is from some sort of pork soup. So it is probably a pig.\n",
"http://www.thechinesesouplady.com/wp-content/uploads/ingredients/meat/pork/pork_marrow_bones2.jpg"
] |
[
"Why does it look like its been cut?"
] |
[
"It looks to me like part of the knee of a pig."
] |
[
"What methods are used to rescue very endangered species?"
] |
[
false
] |
What methods are used to prevent very endangered species from going extinct? Or, if we don't try to prevent them from going extinct do we do anything to try to preserve DNA? By "very endangered" I'm talking about species with a population of less than 250 in the world. For example, the is critically endangered, with a population of only about 110.
|
[
"There are a number of diffrent theories about how stuff should be done. \nOne that has been effective is the Kakapo-project i New Zealand. ",
"Basicly what they did was rid a few Islands of Everything that had not been there when the parrot was around in numbers. ",
"Wikipedia",
" "
] |
[
"Well there are so many different solutions because each endangered animals is faced with its own unique set of problems. So what are ",
" of the causes to animals becoming endangered:",
": illegal hunting, over hunting, prize/trophy hunting, sustenance hunting (for food). ",
" create spaces where you cannot hunt and set up protection programs to mitigate poaching. Set up patrols or guard each animal. e.g. rhinos, elephants, big cats.",
": through deforestation, development, pollution, destruction (trawling, burning...). ",
" Set up areas where these activities cannot be done or modify how they are done. e.g. selective logging vs. clear cutting. e.g. for Rhinos, elephants and tigers.",
": low population numbers mean a loss of genetic diversity\". ",
" start captive breeding programs if possible. Usually done through (qualified) zoos. Release the animals into protected habitat. e.g. Vancouver Island Marmot, or the whooping crane.",
": local taboos, traditions, poverty, war, famine, sustenance hunting. ",
" education for locals about their local ecosystems and learning how to bring communities and ecosystems together for long term sustainable use. Teaching communities about pollution, sanitation, and general self/community care. Providing a means for people to make alternative livings that do not end up further endangering the animal. Working with local governments to set up work incentive programs, community programs end war, improve quality of life, end poverty etc. e.g. instead of locals hunting the animal they could provide (sustainable) eco-tourism tours for that animal. - e.g. gorillas, tigers, lemurs, birds.",
": Some species enter into a new ecosystem usually because humans have brought them their. They can cause a lot of damage and out compete local species. ",
" kill or more likely keep the invasive species at bay through manual removal or introduce a predator to the invasive species (hopefully a native one). e.g. english ivy on the north-pacific west coast of north america.",
"Depending on the species, their distribution, and situation some or all of these might be used in combination.",
"The ",
"IUCN",
" is the world-body that governs the ",
"conservation status",
" of each living species on this planet. They also have definitions for different levels of ",
"park protection",
". They also have a set of ",
"criteria",
" which countries are supposed to use to categorize their species (all life, not just restricted to animals). ",
"Then each country at the federal and state/provincial level will have their own classification scheme. Depending on the category the species falls into certain measures are required to take place: usually the formation of a committee which outlines an action plan for saving the species. Then a certain amount of time, effort and resources is allotted to the species in order to aid it in recovery. ",
"There are also regulation of trade/sale of dead and alive exotic animals/plants. This is governed by ",
"CITES",
".",
"You also have other independent world body organizations that regulate hunting/fishing. Like the ",
"International whaling commission"
] |
[
"Question: What is the minimum number of animals you can start with to completely save the species? If you only had 1 or 2 breeding pairs, wouldn't they die out due to inbreeding? "
] |
[
"Is it t possible for identical twins to have different traits such as hair color or eye color?"
] |
[
false
] | null |
[
"Physically, they are identical in every way.",
"Not true. Identical twins are almost completely genetically identical but this doesn't mean they are completely physically identical. In the case of eye colour and hair colour, these traits are strongly determined by genetics so will mostly be the same. However even eye colour isn't always identical, ",
"about 2% of identical twins have different eye colour",
".\nOn the other end of the spectrum you have fingerprints which are not identical between twins. Traits that you probably learned in school are completely heritable, like tongue rolling, also are not. About 20-25% of twins will differ in their ability to roll their tongue ",
"Source",
". Other traits like height and weight have a big environmental component, so will not be precisely identical. ",
"As to why identical twins can differ, this is largely due to the environmental impact on their features. It is also due to some processes having a random element and not precisely determine by genes, for example the creation of fingerprints. Lastly identical twins develop some mutations after splitting from one another, which are very unlikely, but are possible to affect their physical traits."
] |
[
"I would assume some other forms of life experience could also alter the hair of identical twins, such as more time in the sun for one of them resulting in more bleaching."
] |
[
"Physically, they are identical in every way.",
"Not true. Identical twins are almost completely genetically identical but this doesn't mean they are completely physically identical. In the case of eye colour and hair colour, these traits are strongly determined by genetics so will mostly be the same. However even eye colour isn't always identical, ",
"about 2% of identical twins have different eye colour",
".\nOn the other end of the spectrum you have fingerprints which are not identical between twins. Traits that you probably learned in school are completely heritable, like tongue rolling, also are not. About 20-25% of twins will differ in their ability to roll their tongue ",
"Source",
". Other traits like height and weight have a big environmental component, so will not be precisely identical. ",
"As to why identical twins can differ, this is largely due to the environmental impact on their features. It is also due to some processes having a random element and not precisely determine by genes, for example the creation of fingerprints. Lastly identical twins develop some mutations after splitting from one another, which are very unlikely, but are possible to affect their physical traits."
] |
[
"How are mathematical constants computed on calculators?"
] |
[
false
] |
Such as pi, e, etc. I know in the old days before calculators they had tables for stuff like that with hundreds of decimal places for constants, but how do calculators do it now? Do they just have memory space that hold all of that same information or do they run some equation to get the number?
|
[
"I believe they are stored in calculator's memories, the manual will even tell you the precision in terms of decimal digits of these constants if I remember correctly. ",
"As for their computation on computers, if needed to a high precision:",
"e is pretty simple: since the Taylor series for e",
" is: 1 + x + x",
"/2 + x",
"/6 + ... + x",
"/n!, and thus e = e",
" = 1 + 1 + 1/2 + 1/6...",
"pi is a bit more complicated, but as someone else stated, arctan(1) = pi/4 and arctan(x) has the following Taylor series: x - x",
"/3 + x",
"/5 - x",
"/7..., and thus pi = 4*arctan(1) = 4(1 - 1/3 + 1/5 - 1/7...) but this converges slowly (since it continually adds and removes a term) so there are faster, but more complicated algorithms such as the Ramanujan series. "
] |
[
"On a handheld calculator with like 8 decimal points, it would serve no purpose for pi to be stored or calculated to any higher precision. All the extra digits would be obliterated the first time you added it to another number. I would assume they just store it as a constant value.",
"I'm curious on your source for saying that other constants were stored to hundreds of decimal places. I can't imagine that ever being useful in practice. 64 bits of precision is enough granularity to specify any position between here and Pluto with atomic-level precision. I'm also skeptical that they had even calculated all those digits, since that's something that takes processing power and memory. "
] |
[
"I don't know what's done in practice, but if you know how many terms you want to evaluate, it seems like you could avoid overflow by factoring. For instance, to evaluate",
"1 + x + x",
"/2 + x",
"/6",
"you can factor this to",
"1 + x * (1 + x/2 * (1 + x/3))",
"In practice you can compute this as follows: start with 1, multiply by x, divide by 3, add 1, multiply by x, divide by 2, add 1, multiply by x, divide by 1 (skip this step of course), and add 1.",
"Again, this only works if you know ahead of time how many terms you want to compute, and it probably won't work for series that don't have n! in the denominator."
] |
[
"What is the fidelity of human sensory perception/judgement?"
] |
[
false
] | null |
[
"This question is a bit too broad. This area of research is called psychophysics and has been going on for a long time. These measurements have been done for all of the things you list and many others besides but there is no centralized exhaustive list that I'm aware of. Do you have a specific question in mind?"
] |
[
"I recommend making a new post with exactly that question. Happy to answer it there"
] |
[
"Yeah i had that thought after i posted this, apologies.",
"My specific question is the title i guess, my other questions were more or less my way of trying to define my thought with my limited vocabulary haha. ",
"The question that prompted me to post this was how accurately a human could tell the difference in two objects weights.",
"But informing me of Psychophysics is a very good stab at answering what i am looking for."
] |
[
"Why is accelerating more fun or exciting than driving at a constant speed of 100mph?"
] |
[
false
] |
[deleted]
|
[
"Except for small bumps in the road, you can't feel any difference from going 100mph versus 0. When accelerating, you'll feel the normal force of your seat pushing you forward."
] |
[
"One of the effects of relativity is that all constant-velocity reference frames look the same. That means that if your speed/direction of travel doesn't change, you can't actually tell that you're moving. (Of course you can refer to something outside, like the trees outside the car window, but that's cheating.) Only when your velocity changes is there acceleration, and since Force = mass x acceleration, only then is there a force for you to feel."
] |
[
"G's"
] |
[
"What is happening in an operating system when a process is \"Not responding\"?"
] |
[
false
] |
I'm taking a course on operating systems right now, so I know a little about how processes work. An OS switches context between processes several times a second, and this makes it seem as though all your processes are running simultaneously (and on multicore systems many of them actually are running simultaneously). Sometimes processes get put into a waiting state when they are trying to access slower resources like I/O or a hard drive. Is this what causes an OS to mark a process as "not responding"? When a process is waiting too long? When I'm writing a program I don't write messages to the OS to let it know that I'm running fine, so I'm assuming it has to have something to do with waiting. Also, are there ways to handle your code so that this non-responsiveness doesn't happen as often for your process? EDIT: Holy crap, thanks for the responses everyone! You gave me a lot of good studying material.
|
[
"Here",
" is a nice post from Raymond Chen explaining part of your question.",
"Generally, the OS checks if an app hasn't retrieved messages from the message queue in a long time (a couple of seconds) and if it hasn't - the app is \"not responding\".",
"Usually the app is stuck performing a heavy computation on the main thread and is unable to retrieve messages from the message pump. Such computations may be heavy calculations or using a blocking API to write to the hard disk/network.",
"This can be avoided by performing heavy calculations on a separate thread, in order to keep the main thread free to respond to messages."
] |
[
"This is pretty much dead on. I have written a lot of software in which I never multi-threaded so my stuff always appeared as if it was dead. If software multi threads it can usually leave the UI active for the user and the error message is a lot less likely to happen."
] |
[
"For a simple demonstration of a thread try this page: ",
"http://afshinm.github.io/50k/",
"The \"web workers\" thingy here is an implementation of threads in you browser, the interesting aspect is that the \"children thread\" doesn't block the \"main thread\", two threads are working in parallel (opposed to serial)."
] |
[
"How high pressure does it take to transform liquid water into ice at room temperature?"
] |
[
false
] |
On high mountain tops water boils and turns to steam at a much lower temperature because of the lower atmospheric pressure. Is there somewhere in the sea deep enough to turn the water into solid ice? And can we recreate such pressure with today's tech to solidify water at normal room temperature?
|
[
"We need ~10 kbar of pressure to freeze (pure) water into solid ice at 25",
" C according to ",
"this diagram",
". At the Mariana Trench, apparently we only reach ~1 kbar according to ",
"Wiki's second paragraph",
".",
"You can create such a pressure in a ",
"diamond anvil cell",
", actually you can create about 300 GPa according, but I'm curious to see if people have done this with water.",
"Edit: never mind, we HAVE made ice at room temperature before: ",
"http://www.pnas.org/content/108/19/7685.abstract"
] |
[
"Your phase diagram doesn't go to a high enough pressure! If it were to keep going up in pressure, you'd see that you actually can form solid ice at room temperature. ",
"Here is a better diagram: ",
"http://en.wikipedia.org/wiki/Ice#Phases",
"and here is an experiment where they've done this: ",
"http://www.pnas.org/content/108/19/7685.abstract"
] |
[
"I believe it's the other way around. If you compress ice, it turns into water. Ice takes up more room than water, so you can't compress water into regular ice. You can compress water into other solid forms (called Ice II to Ice XV), but they do not have the same crystal structure as normal ice."
] |
[
"Why is the moon's horizon not directly perpendicular to the sun?"
] |
[
false
] |
I'm not sure if I worded that question correctly, but hopefully someone can help me out. I was walking close to sunset time last night (I live in Pennsylvania, I figure that has something to do with it) and I noticed something I never had before. If I looked at the moon, I could obviously see the horizon, as it's not a full or new moon. But when I drew a line, going straight out from the horizon, the line did not extend straight to the sun, as I assumed it would. It seemed to be above the sun (approximately 10-15 degrees, if I had to guess). I realize it would not extend perfectly into the sun, what with rotation, time delay, etc, but I figured it would be a lot closer than it actually was. What am I missing? It almost seemed as if the light hitting the moon couldn't be coming from the sun, though that's obviously impossible.
|
[
"I definitely know the light was from the sun, no doubt. It just didn't appear that way from my angle (which is why I was so boggled). The sun was just above the horizon in the west, and the moon was, like you said, almost in a \"noon\" position (middle of its visibility time here in PA). It was more to the south, it seemed (much closer to the southern horizon than the northern), not directly overhead. And I know the sun is close to it's most \"northerly\" point, what with it being so close to the solstice. I still thought the light should seem to be on a direct angle from the sun to the moon, which it did not appear to be.",
"I guess I was discounting the geometric effects too much, and it's quite possible my \"straight line\" drawing was simply off.",
"Are there any crude/cheap tools I could use to measure this more accurately?"
] |
[
"What you saw has nothing to do with rotation or time delay. After all, the speed of light is ",
" fast, so there's not much time delay between the Sun and the Moon and the Sun and the Earth.",
"The moon is approaching full, which means it was probably close to overhead or even a little in the East when you were watching the sunset. I imagine that what happened is that you tried drawing a line with your finger and didn't account for the spherical geometry of the situation. From your perspective in Penn., even during the summer, the sun doesn't travel in a perfect line from East to West. It travels in a great arc across the sky, as does the Moon. Also, the Moon and Sun don't cross the sky in the same plane (that's why eclipses are so rare).",
"I can assure you that the light reflected from the Moon is from the Sun. I just think your \"straight line\" geometry was a little off.",
"(However, I might have interpreted your question incorrectly. Please feel free to ask me anything)"
] |
[
"A compass and a protractor always seem to work well. You can figure out what direction (Azimuth, as it's called) and elevation (Altitude) each object is, then do some fancy spherical geometric calculations to figure it out."
] |
[
"Do we know any Neuroscience on Lucid Dreaming?"
] |
[
false
] |
I know dreaming as is is already lacking a whole lot of completeness, much less understanding how lucidity will manifest itself thereof. But with whatever it is we do know and understand, what's the best science to explain one of the most powerful experiences the human mind is capable of without foreign substance/manipulation?
|
[
"This article",
" does a fair job of discussing dreaming and it's out the Psychiatry Department at Harvard. I think it's readable by a non-scientist, but if you have specific questions, feel free to ask.",
"In studying the physiological correlates of lucid dreaming (Voss et al., 2009), it \nwas found that there is a shift of brain activity in the direction of waking as one \nbecomes lucid within REM. A degree of self-reflective awareness occurs such that \nthe dreamer becomes aware that he or she is lying in bed dreaming. In order for \nthis to happen, several brain regions that had become inactive during the REM \nstage of sleep, such as the DLPFC and the precuneus, reactivate when lucidity \nemerges in REM. Additionally, during lucid dreaming, compared with non-lucid \ndreaming, there is an increase in overall cortical connectivity and greater activity \nin the gamma band of frequencies. The gamma band, around 40 Hz, is a \nfrequency band known to be associated with conscious processing. Its predominance during lucidity indicates that conscious processing is taking place. This \nprocessing leads the dreamer to the awareness that he or she is, in fact, dreaming. \nIn short, self-reflective awareness and volitional control re-emerge in the dreamer \nwhen there is a reactivation of the DLPFC, an increase in gamma frequency \npower, and an increase in global cortical connectivity. "
] |
[
"But we already knew the brain could do all those things. In fact, it's doing that stuff ",
" when you're awake. The lucid dreaming research hasn't really informed us on how exactly it works. Also, your internal imagery isn't photoreal. It seems perfectly realistic because you only imagine a certain level of detail, roughly equivalent to what you pay attention to when you're looking at real scenes. If you'd never pay attention to the texture of the carpeting, you won't have textured carpeting in your dream and you'd never know. "
] |
[
"Wow. I wasn't sure there would be much if any actual science of lucidity, other than philosophical/scientific speculation! This is very interesting. And this was already ~2 years ago. It's exciting to think about how there really are many fields unexplored and incomplete that can still be constructed by the few who enter to change it.",
"I figure for lucid dreaming, you might have an overlap in explicit professions, no? You have people who specialize in the science of dreams, and you have those who try to categorize and confine consciousness as well... wouldn't you be using the best of both intelligences to derive any if not most of all progress in analyzing lucid dreaming?",
"Also, do you have any speculation on what may be benefited from learning the science of lucid dreaming?"
] |
[
"Why is it that when we use time less than a second we use a metric system but not for anything more than a second?"
] |
[
false
] | null |
[
"Not everything has to have a deep reason. Some conventions are just accidental. "
] |
[
"Then once we get to year, we go back to a decimalized metric system (megayear, gigayear, etc.). It's just a funny convention, and likely related to our daily lives being so intertwined with the night-day cycle. Perhaps someone more familiar with history of science can give more details."
] |
[
"Yeah I tried looking at in online but, the answers were usually \"cause that's how it is\" type answers which bothered me. I feel like we could measure days as 86.4 ks. "
] |
[
"How do we perceive the color brown?"
] |
[
false
] |
The color brown isn't part of the electromagnetic spectrum and usually results by mixing colors. Are there cones in our eye that perceived mixed signals as brown? Is it perceived later down the line at the occipital lobe due to the stimulation of multiple cones?
|
[
"You're right in that there is no wavelength of light that is brown. But our eyes don't perceive wavelengths anyway. Our eyes have 3 kinds of cones that measure 3 parts of the electro magnetic spectrum, and our brain turns any combination of signals from the 3 types of cones into a color. Brown means the eyes perceive mostly low frequency light (red-yellow) with low luminance.",
"Edit: cones not rods"
] |
[
"To clarify, we have one type of rod, not 3, and those rods respond to a variety of wavelengths of light (but peak - ie respond most easily/strongly at a particular wavelength).",
"We have 3 other types of photoreceptors called cones which “peak” at different wavelengths (but, again, each type of cone responds to a variety of wavelengths near that peak). We often call these “red”, “green”, “blue” cones colloquially but they are properly called long, medium, and short wavelength cones.",
"That said, there are plenty of wavelengths that, say, medium and long cones BOTH respond to. But since one type will respond more strongly/easily (the wavelength being closer to either the long cone peak or the medium cone peak) the brain can still distinguish between light at that intermediate wavelength and other situations that involve activating both long and medium cones.",
"Basically the brain gets a mix of activated cones (in various proportions and strengths in additional to the retinal location information). It gets passed through the LGN in the thalamus to V1 where “blobs” (the technical term) existing inside hypercolumns pass along that info for further processing in later visual areas further into the occipital lobe.",
"Only later does color info get “re-integrated” with other info from the visual scene like form, motion, location and this “binding” leads to us perceiving a whole object (red basketball on my left) rather than the brain processing a bunch of separate info (only system says sphere, one system says left, one system says red, but treated as distinct objects/problems)."
] |
[
"Yes, but still it gets created by mixing spectral colors AND these colors are picked up by the cones. How else should it work?",
"\nTop comment wrote basically the same thing like I did 5 hours earlier. The only difference is I didn't point to the fact that brown is a mix of wavelengths."
] |
[
"Is the brain's pain center(s) capable of distinguishing between physical pain and emotional pain?"
] |
[
false
] | null |
[
"A recent paper published in ",
" showed that the brain has a similar physiological response to emotional pain (social rejection) than it does to physical pain. So while different receptors may be used to initiate that reaction (since there may not necessarily be a physical stimuli that causes emotional pain), it seems that our brain treats it more similarly than initially thought.",
"Source: neuro-nerd here",
"Actual source: ",
"http://www.nature.com/mp/journal/vaop/ncurrent/abs/mp201396a.html",
"EDIT: Thanks for correcting the journal name!"
] |
[
"There is an overlap between the two. When you put people under an MRI scan, some of the same regions light up. These regions are the ones that \"feel\" that you are in pain, not the sensory areas themselves. ",
"In one study, they compared participants who had just been dumped and where looking at pictures of their ex and participants that were being prodded. The intensity of activation in those areas virtually mirrored each other."
] |
[
"Does empathy also play a role here? I am not somebody who vivedly experiences other people's emotions, but I know people that do.",
"They will sit there and weep with someone, even if they don't really know why. ",
"The way I understand it, we have a \"pain center\" in our brains that deals with all the signals that come from various sources.",
"do all stimuli emotional/physical just feed into that?"
] |
[
"Why are traits such as acute vision/hearing/smell not propagated through evolution."
] |
[
false
] |
[deleted]
|
[
"Well to begin with, your opening premise isn't correct. We do not have dull senses. For instance, cats have a visual acuity of about 0.1 degrees [1] while humans have about 0.02, i.e. we can resolve things 5 times better than cats [2]. Now, yes, there are some animals that have higher visual acuity, and some that have lower. Better hearing and worse.. etc etc etc...",
"But why. Well, senses come at a cost. To have better hearing we could have bigger ears, and bigger inner ears. This would mean more space in our head, and more ear volume to get damaged. We could have better vision by packing more retinal cells in, which would mean we would need more vitamin A in our diets, and use more energy to see. There are certainly other costs associated with better sense that I can't think of right now. Basically, evolution solves the problem \"what is the least you can get away with.\" You might as well ask, why aren't our legs longed so we can run faster? We would need more protein and energy in our diet to give us bigger muscles, and to power them. And we simply didn't need that.",
"[1] ",
"http://www.sciencedirect.com/science/article/pii/0042698976902546",
"[2] eye, human.\"Encyclopædia Britannica. 2008. Encyclopædia Britannica 2006 "
] |
[
"Humans also have a history of hunting in \"packs\". This would reduce the need for ears that can pinpoint the exact location of a noise, or need to pickup on things as finely as a lone predator."
] |
[
"Humans have a better ability to localize the source of sounds than dogs do actually."
] |
[
"why is my body still able to feel the motion of waves after having left the beach?"
] |
[
false
] |
this mostly occurs right before i am about to fall asleep.
|
[
"Our brains are very good at compensating when external stimulus throws us off. There are great experiments, for example, showing how our brains will gradually adjust to wearing special goggles with mirrors that flip everything the wrong way. Over time, the brain adjusts.",
"The brain also adjusts to coping with the ups and downs of being out at sea. However, that compensation also takes time to go away. When you're lying in bed feeling the ups and downs, you're still experiencing the compensation mechanism before it fades away."
] |
[
"Is this how it works wearing a hat and then taking it off, but still feeling the hat hours after its come off?"
] |
[
"Or when a cast comes off, in a more extreme example. Yes, likely the same compensatory/adaptation system."
] |
[
"If extinct species are brought back by implanting recovered DNA in the zygote of similar existing species would we expect epigenetics to make significant changes to the development of the baby?"
] |
[
false
] |
I'm not sure I really understand what the process of making an extinct species baby would be but if we could do it could we ever make a real mammoth or a real neanderthal or would they be effected by the surrogate mother. Also, (these are more ethics/implications of science question - not sure how appropriate it is for this thread) if we did make a neanderthal do you think it could cope in a homo-sapien society? Could we expect it to be able to learn English? At what age do we tell it that we probably drove it's species to extinction? Do we treat it like an pet or a human?
|
[
"The short answer is yes, we would expect changes, but the extent to which these changes would ultimately affect the phenotype of a successfully cloned extinct animal are difficult to predict. ",
"This type of project",
" has indeed been attempted with the ",
"Pyrenean Ibex",
" in 2009 and the efforts are documented pretty rigorously ",
"here",
". This neonatal ibex was born with lung defects that caused its death rather quickly, though this was probably due to the aged, frozen DNA and not so much an artifact of epigenetics. ",
"You can see that the process of cloning the Pyrenean Ibex involved \"clearing out\" (enuclating) the goat oocytes to leave a blank-ish slate for the ibex's genetic material to be inscribed upon. Even assuming that this did not leave any epigenetic artifacts through the handling of the ibex's DNA or the goat oocyte, we have to turn our attention to the gestation period of roughly 5 months wherein the carrier (Spanish ibex or goat/Spanish ibex hybrid) exhibits life history differences from wild Pyrenean ibex. Differences in ",
"diet",
", ",
"exposure to toxins",
", ",
"maternal care",
" (which ",
"this article",
" demonstrates in a slightly less relevant but extreme way), can all affect the physiology, behavior, and etiology of disease in infants. ",
"I guess the longer answer is to say that: provided you could control all aspects of the enuclation of the oocyte, the life history and behavior of the egg carrier, had an abundance of well-preserved genetic material from a young or even fetal extinct animal, and knew enough about the extinct animal that you could reliably reproduce all aspects of its wild-type life, you may be able to reduce epigenetic effects in phenotype to below the limits of your perception. ",
"But that's a tall order. "
] |
[
"Look I'm really not trying to step on your toes but I have a few problems with your contribution. If you look to the bullet points under the goal of what this subreddit is for you'll see what I'm referring to: ",
"we undoubtedly would treat them as lesser-slave-beings.\n\"Well they are not as smart as we are, they shouldn't earn as much as a sapien.\"",
"Epigenetics is most probably going to cause major hurdles for recreating distinct organisms.",
"My understanding of the current plans of recreating mammoths is that it will be more of a hybrid of mammoth and asian elephant than a true elephant (not necessarily 50/50).",
"-These are a combination of recollection and layman speculation. You are not citing specific articles or reasons for these beliefs and are clearly relying on memory for these statements. In this way, these points cannot be considered \"Scientific\" (another one of the guidelines to the right).",
"As an aside: Interestingly Asian elephants and mammoths are more closely related than Asian elephants and African elephants.",
"-This may fall under the bullet point for \"On topic\" even if it is very interesting. Once again, however, you provide no source for this fact.",
"I'm certainly not trying to pick on you, but I do want to point this out so that in the future you can be mindful of it and make excellent contributions. "
] |
[
"You are absolutely correct, I got caught up in the moment and wanted to share. I will now try and correct my lack of scholarship (see below). For better reference, my speculation and opinions are based on my training in molecular and cell biology. ",
"\n A number of blogs and news sources report that a man by the name of Akira Iritani is working on a project to attempt to clone the mammoth. I have not been able to find any website for Iritani’s work or find out which institution he works for with certainly because I do not know Japanese and the English version of the various referenced insitutions are incomplete.",
"\n",
"Link to a pub med search for Akira Iritani showing a history of publicans in embryonic cloning",
" ",
"My personal understanding about the mammoth cloning project was the first plan was to attempt to breed a hybrid of asian elephants and mammoths – this is aparently the interpretation of science reporters and may not necessary be fact. I have not found a primary source for the researchers actual project plans. I was wrong to state their plans as fact as I can not find the teams plans or establish if the reporting is actually correct.",
"\n",
"Example of such an aforementioned article # 1",
"\n",
"Example of such an aforementioned article # 2",
"\n",
"\nThe following snippet is from a review paper about epigentics and embryonic cloning. ",
"Source.",
"Nuclear cloning experiments in mammals have shown that a somatic cell nucleus from adult tissue can initiate embryonic development after being transplanted into an enucleated oocyte. The remarkable ability of the cytoplasm of an oocyte to trigger the ‘dedifferentiation’ of an adult nucleus indicates that a committed or differentiated cell fate can be reversed through epigenetic reprogramming. However, cloning is inefficient, as most cloned embryos die shortly after implantation and the few that survive to birth frequently have developmental abnormalities and seem to have a short lifespan. This indicates that the reprogramming of the transplanted nucleus is incomplete, as compared with that in a fertilized egg from natural mating.",
"This is why I mentioned before that epigenetics would cause hurdles. Whether it does or not in the case of mammoths remains to be seen.",
"\nI originally heard the factoid regarding the relationship of asian and wolly mamoths in a science article (non-scholarly). I have just completed some digging and here are my findings:\nA 2006 study concluded that based on mitochondrial dna and genome fragments of mammoths that asian elephant and mammoths were more closely related to each other than they were to african elephants.",
"Source",
"\nInterestingly a 2007 study refutes the conclusiveness of this previous study and suggests that there is not sufficient data to make this conclusion. ",
"Source",
"\nI have also checked what Wikipedia says on this topic. I found that the Wolly Mammoth article makes the same source-less assertions that I made. ",
"I have since edited the article",
" to include the ambiguity and sources I found.",
"\n I admit my comment was completely opinion and it was not warranted in this circumstance.",
"\nMy opinion was based on ",
" of how the human species currently and historically treats its own kind and how the human species currently and historically treat other animals."
] |
[
"How did different civilisations develop sounds/letters that others cannot pronounce?"
] |
[
false
] |
What I mean is for example,in japanese, there is no letter "L", just a thick R, in dutch & french there is the "gh" pronunciation, in arabic & certain other languages there are many letters not present in other languages, what I mean by this is why do people from other civilisations not have the ability to pronounce certain letters/characters, & how did these developments come about? EDIT: I forgot to mention another example, Arabs cannot pronounce the letter P
|
[
"Well, you don't pronounce letters, you pronounce phonemes. Letters give some hints as to what the phonemes are, but there's not a 1:1 relationship, and with English and many other languages there really aren't even any hard to fast rules - the the a and hat is the phoneme æ, while the a in all is the phoneme o:. And there are even words with the same spelling that are spoken differently depending on meaning - does \"does\" represent the third person singular of do, or is it a female deer? Different civilizations write things down in different ways, practically no one has a widely used writing system that is a totally accurate representation of how they actually speak.",
"As for the rest of your question, different peoples just developed different sounds when they were trying to get across their message. In China, one of the ways they differentiate between syllables is to alter their pitch in a set way while speaking it (which is effectively a phoneme in itself), in Bantu languages, many languages have a whole set of phonemes that just consist of various different clicking noises (one in particular has dozens of different variations on clicking, depending on the part of the tongue it's done on, the number of clicks, and such - they can easily distinguish any of them, and usually respond with mystification when a foreigner can't). These can be hard for a foreigner to reproduce simply because they're not used to them. And the actions you use when you use even relatively simple phonemes can be quite complex. ",
"Could you even tell me precisely what actions you take when you make an l sound, for instance? Well, in phonemic terms it's an alveolar lateral approximant. In it, you narrow your vocal tract at the place of articulation, on the alveolar ridge, and you perform this articulation with the tip of your tongue. It's a voiced phoneme, so you vibrate the vocal cords somewhat during it. The sound is actually made by directing the airstream over the sides of the tongue, and air is only supposed to escape by means of the mouth.",
"Now, try imagine making an alveolar lateral approximant only by being told that description. I would imagine you couldn't. But, you have the automatic muscle memory to perform this alveolar lateral approximant at the drop of a hat, even though, really, you have no idea what your doing. And if you were trying to tell a Japanese person how to do it, most likely all you could tell them would be to just make an l. And even if you repeated the description I just gave you, it probably wouldn't even help that much.",
"Confusing things even more, there are allophones, which are when different phonemes sound the same. This is the case with the Japanese l and r. The brain hasn't been trained to differentiate them, and intuitively perceives them as the same sound. So, to a Japanese person, you just sound like you're making a funny r. This is the same case with us when it comes to the unaspirated t and d - unaspirated t doesn't exist in our language, it sounds exactly like a funny d to us. When Wades-Giles made their romanization system for Chinese, though, they chose to represent unaspirated t with t, and use t' to represent a \"normal\" aspirated one, which is actually quite phonetically sensible (it's similar to how the IPA does things - only they add a small t in subscript to indicate aspiration). But this causes English speakers naive with the system usage to just pronounce everything using our t - so, taoism. Eventually, it was largely superseded by the Pinyin system, in which unaspirated t was simply d (which is why you also see daoism). This works because d and unaspirated t are allophones in the opposite direction to the Chinese, so it sounds like we're making a funny unaspirated t to them when we make a d. ",
"Also note that, to you, the difference between t and d is probably like that between night and day, if I used a d in place of a t, I might as well have substituted in a z or an m. But, phonetically, you're practically doing the same thing - in a t, there's just a puff of air, and in a d, there's no puff of air and you put a little voice into it. The rest of the actions taken when performing the phoneme, which I won't go into, are the same. What's amazing is not that certain people can't tell the difference between them, but the fact that anyone can at all. And, again, you had likely had no idea they were similar, or about that puff of air in t, or the voicing in d, you didn't know before I told you, and you probably won't remember afterward, though you do it every day."
] |
[
"You are assuming people had access to the entire range of sounds when they first made up words, when it's likely they simply stuck with whatever sound they uttered first. Think of it as a random seed that then dictates in what directions the language evolves in."
] |
[
"if you adopt a japanese kid and teach it only english, he will pronunce everything OK.",
"But he would also effectively be part of the civilization of the parent from whatever English speaking country that adopted him. "
] |
[
"What is physically happening when someone gets sick and can't smell/\"taste\" anything?"
] |
[
false
] |
I understand that what we perceive or accept to be "taste" is actually our sense of smell and that the sensation of taste (bitter, salty, sweet, sour, savory) is mostly unaffected by illness. So what is physically happening and why can't one smell "taste" anything?
|
[
"Well to address your first question, you can be suffering from congestion during a sinus infection but be able to breathe through your nose. Sometimes the infection can produce dense congestion in the deep sinuses without a lot of mucous coming out of the nose. However, when you chew food the aroma's and chemical compounds released don't all travel out of the mouth and up through the nose. The blockage can prevent the nerve receptors from receiving these. ",
"Another part of this deals with drainage into the mouth and throat. There are taste \"buds\" on the tongue as well nerve receptors in the throat and lips that help interpret taste. These can all be basically skewed by the consistent presence of mucous draining into the mouth and throat 24/7. Think about that weird taste/smell you get in your mouth when you wake up in the morning while you're sick.",
"As far as the mucous coating, yes it blocks the initiation of smell sensation within the nose, but I don't know of any aspect concerning breaking it down. The mucous is being continually produced to get rid of the unwanted substances so it's more a matter of its production level will decrease once the underlying issue is contained via your immune system.",
"This link regarding taste disorders may be off interest also to you.\n",
"http://www.medicinenet.com/taste_disorders/article.htm"
] |
[
"You're right that a significant portion of taste is smell. When your nose is congested, and you breath through your mouth, scents don't reach your olfactory (sense of smell), so flavors are diminished. You can reproduce this simply by holding your nose. It's hard to tell the difference between a very small piece of onion, and a similar-sized piece of apple while holding your nose. "
] |
[
"When your nose is congested",
"Why then when someone ",
" no congestion (their nose isn't stuffy/blocked up and they can breathe freely) would the sense of smell still be diminished or non existent?",
"Is there a mucous coating covering something specific to smell that doesn't come off easily and/or takes time for the body to break down? This is what I'd like to know."
] |
[
"How did early cyanobacteria develop the means for photosynthesis?"
] |
[
false
] |
As a preface I am somewhat of an armchair scientist so please feel free to correct me anywhere I am mistaken. Please forgive any formatting problems as well, I'm on mobile at the moment. I understand that these algae were likely the first prolific organisms on Earth, and their presence provided our atmosphere with oxygen. If they processed carbon dioxide into oxygen the way we understand photosynthesis to work, where did the carbon dioxide come from? Was there enough of a presence of oxygen for it to bond with carbon to create CO2 in large enough quantities for this form of life to develop? Was it perhaps some positive feedback loop? I'm stuck in the thinking that CO2 requires O2, and yet CO2 is required to create O2 through photosynthesis. Does current science even have a plausible answer to this question?
|
[
"How did the mechanisms of the light and dark reactions evolve? For example, the water-splitting happens through the manganese oxocluster; did this originate from inorganic sources? Similarly with the huge variety of photopigments that absorb the light. Also, how did the key dark reaction enzyme rubisco develop? Sorry, there probably are no answers to these yet, but any insight on these is welcome."
] |
[
"How did the mechanisms of the light and dark reactions evolve? For example, the water-splitting happens through the manganese oxocluster; did this originate from inorganic sources? Similarly with the huge variety of photopigments that absorb the light. Also, how did the key dark reaction enzyme rubisco develop? Sorry, there probably are no answers to these yet, but any insight on these is welcome."
] |
[
"Sorry, that's a little too specific and out of my field to answer right away, but it's an interesting topic. I've always stayed out of plant biology (and other photosynthesizers).",
"Here's a review that does a good quick summary of the various parts of photosynthesis and what we know from 2010. ",
"http://www.plantphysiol.org/content/154/2/434.full",
"And here's one that goes into a lot more detail on rubisco and carbon fixation, if that's what you're interested in: ",
"http://www.ncbi.nlm.nih.gov/pubmed/21740227",
"I did a quick look for you though. RuBisCO was interesting to me, so I started there. We have this article from 2007: ",
"http://mmbr.asm.org/content/71/4/576.full",
" (if you can't access it and want to read it, pm me) tracing RuBisCO to an archaea, specifically form III RuBisCO, which does essentially the same thing as I and II, help fix carbon from CO2. There doesn't seem to be much since then. It's always murky with these proteins that evolved so long ago.",
"Amusingly, I also found one article devoted to the possible extra-terrestrial origin of RuBisCO. ",
"For example, the water-splitting happens through the manganese oxocluster; did this originate from inorganic sources?",
"Not entirely sure what you mean by \"originate from inorganic sources\" here. But, it seems likely the Oxygen-Evolving Complex evolved (hah) from manganese containing enzymes that served other purposes, as described in this article here: ",
"http://www.sciencedirect.com/science/article/pii/S0010854507001877",
" There are also competing ideas and it's not nearly settled."
] |
[
"I’ve heard that humans can see more shades of green than any other colour, is this true? If so, would it be advantageous to outfit street lights with green hued bulbs for safety purposes?"
] |
[
false
] | null |
[
"It's true we are able to discern more shades of green than any other color, this isn't really helpful for streetlights. The purpose of those is to illuminate an area, not project an image with subtle shading gradations. So, the only real priority is that the light is bright enough for the intended purpose. Color for general illumination should be as close to white as possible so as to enable our eyes to discern colors accurately. If these lights were green, then objects illuminated by such light that were blue or red in color would be darker and hard to see, and their actual color would be difficult to interpret."
] |
[
"The yellow streetlights also have gaps in their color production, leading to things like green cars appearing black, since the light doesn’t produce green."
] |
[
"The yellow fo street lights has two benefits. First sodium tubes are cheaper and have better service lives than many alternatives and secondly, yellow light is marginally better at penetrating foggy conditions, so safer for drivers."
] |
[
"How do we know that a Hydrogen atom only has one proton and one neutron?"
] |
[
false
] |
Extrapolate this to all the elements. What experiments were preformed so that we know how many protons and neutrons each element has? Thanks!
|
[
"Hydrogen only has one proton. An atom with one proton and one neutron is a ",
"deuterium",
" atom.",
"Watch the BBC's ",
"documentary",
" (watch all the episodes!) on the periodic table. It explains much of how we learned about ",
"stoichiometry",
". Many early studies were based on gases, since the number of gas molecules is proportional to volume - an easily measured value. By using gases as a reactant or product, we can gain insight into the ratios with which atoms bind to form molecules."
] |
[
"There are many ways to study the atomic mass and structure of a nucleus. One of the most direct being mass spectroscopy, whereby ionized molecules are passed through a magnetic field, which will apply a force to the molecules and bend their path by an amount dependent on their mass. In this way we can determine that, for example, Hydrogen atoms weigh a fourth as much as Helium atoms, etc.",
"Further, since we know how many protons an atom has based on which element it is we can easily fill in how many neutrons it has by subtracting from the total number of nucleons inferred from the atomic mass. We can also study the same things using stoichiometry (e.g. 2 H2 + O2 = 2 H2O, adjust the amount of reagants used until you don't get any unreacted leftovers then simply measure their mass) but it is less precise."
] |
[
"Hydrogen doesn't usually have any neutrons. It can have as many as six or seven (I forget) with various degrees of stability, but in its overwhelmingly most common form — something like 998 atoms out of a thousand — it's got none at all."
] |
[
"If I were to drop a glass marble into an infinitely deep body of water, would it eventually crack or continue to be compressed indefinitely?"
] |
[
false
] |
Doesn't have to be a marble but a sphere seemed like an easy shape to choose and glass seems brittle. I guess my question could be more general if I rephrased to: Can a sphere be uniformally compressed indefinitely and retain its shape (not dimensions) or would another effect come into play?
|
[
"Well...at some depth of your infinite water, the water would start undergoing nuclear fusion, (if you substitute \"infinite body of water\" for \"extremely large hydrogen gas cloud\", this is what leads to star formation).",
"It would not be like in a roadrunner cartoon where the marble just gets compressed into an infinitely flat pancake. On its way down the pool, the marble would ",
"(EDIT: someone pointed out that it likely will not crack from pressure induced stress due to the minute change across the marble and the high YM of borosilicate glass would not fracture it before it hit an ICE IV barrier and stopped moving. I maintain that there would be no Ice IV barrier due to the heat from the fusion of water far far below, (remember that this is an infite ocean, infinite depth, area and constant gravity), and provide an explanation, below. We are still discussing it.), ",
"undergo some phase changes, and then start fusing, and then turn into a quark-gluon plasma with the rest of the water. That is about the limit in terms of being able to describe it with modern physics.",
"(EDIT: I understand that that scenario is impossible but the essence of his question is about the behaviour of something dropped into an unimaginably deep ocean that behaves like a pool on earth, uniform gravity in one direction, etc)"
] |
[
"On its way down the pool, the marble would crack, and then turn into a fine powder",
"This reads like your speculation. The atoms are being pushed ",
" by hydrostatic pressure. What is the driving force for a crack to open, or powder to form?"
] |
[
"Wouldn't the marble just float somewhere in the water column where water gets to the same density as the marble?"
] |
[
"Why is exercise good for your heart, but stress is bad?"
] |
[
false
] | null |
[
"Stress has a lot to do with cardiac health.",
"According to this Kaiser ",
"Permanante page on effects of stress",
": \"Stress is linked to high blood pressure, abnormal heartbeat (arrhythmia), blood clots, and hardening of the arteries (atherosclerosis). It's also linked to coronary artery disease, heart attack, and heart failure.\"",
"I believe the question he is trying to ask is why is aerobic exercise (stress on heart muscle) good for the heart while chronic stress causes such problems with the heart. I think the question was phrased poorly causing the misunderstanding.",
"Chronic stress is bad for the body because when you are chronically stressed out your body is in the \"fight-or-flight\" mode all the time. That really takes it's toll. The stress response is meant for a short period of time like running away from a wild animal or something. But with modern stressors (jobs, realtionships, family, ect.) people are stressed all the time and your body didn't evolve to be in stress mode all the time and so when that happens it causes problems. Basically it is like your body being on turbo mode all the time and as a result your body starts to have problems as a result. "
] |
[
"It does ",
"not boost the immune system",
". Cortisol is the primary stress hormone and in stress (e.g. fight or flight) it suppresses non-essential body functions temporarily like the immune system so all your energy can go into fighting or running away. ",
"Here is ",
"another source from Utah University Genetics",
". See page A2 1:35 for the part about suppression of the immune system."
] |
[
"No universal conclusions can be drawn about boost/suppress \"the immune system.\" There are many subsystems in the immune system that respond differently to cortisol, and there is not perfectly consistently directionality to response to stress, either short or long term. Both skyskimmer and TalvRW are reasonably correct from the way of looking at it that they propose, but actually over-generalizations. "
] |
[
"How is the plane of polarised light rotated by a particular 'handedness' of optical isomer?"
] |
[
false
] |
I know the basics of optical isomerism and that if both the left and right isomers are in a 50:50 ratio, the racemic mixture will have no net effect on the plane of light passing through it. What I cannot fathom is exactly how light interacts with a particular isomer to be rotated at all. Is the light absorbed and remitted along a different plane? Does the arrangement of groups around the chiral centre somehow distribute the overall charge density of the molecule in a specific way that interacts with the magnetic field of the EM Wave?
|
[
"Optical activity is a type of ",
"birefringence",
". Optically active isomers act differently on the left handed and right handed (circular) components of the light's polarization vector, resulting in a net rotation.",
"More thoroughly, the trick is to express (linear) polarization as the sum of two circular polarizations: P = P1+P2*e",
" .",
"In an optical isomer, light polarized at P1 (right handed) and P2 (left handed) experience difference refractive indices and therefore travel through the material at different velocities, which gives rise to a net rotation of the polarization plane. Optical isomers have a specific rotation (SR) which is simply the difference of these two refractive indices. ",
"The left handed isomer has the opposite SR as the right handed isomer (P1 and P2 are switched), so when they are mixed evenly the net effect is nothing.",
"EDIT: ",
"platypuskeeper",
" had an excellent physical analogy describing this in another post."
] |
[
"Well, for ",
"bi-isotropic materials",
", specifically Pasteur media (chiral and reciprocal), linear polarization can't exist within the media. You can actually show this using Maxwell's equations and the constitutive relations for bi-isotropic materials.",
"So, an incident linearly-polarized wave gets split into two left and right circularly polarized waves. These travel with different velocities, so at the opposite end the light leaving the media looks like the linear polarization has been rotated. "
] |
[
"SR is not a \"fudge factor\", it is the difference of the two RIs [SR=RI(LH)-SR(RH)]. ",
"Also, my understanding is that the two enantiomers do NOT have different refractive indices for plane polarized light, only for circularly polarized light.",
"See ",
"andand89's reply",
"."
] |
[
"What evidence (if any) would there be if a massive asteroid struck earth in the middle of the Pacific Ocean?"
] |
[
false
] |
Okay so this thought only came to me after reading an article about Scientists/Geologists now thinking there may have been a large comet impact some 13,000 years ago, but they do not have a crater to prove it. If a huge asteroid struck way back when, say in a part of the Pacific farthest from all land (the middle in simple terms) but also over incredibly deep water (Mariana trench deep) what evidence would there be? I am assuming that in 5-6 miles of water it would not necessarily reach the ocean floor to create a crater?
|
[
"How big an object are you talking about?",
"a Big object would leave behind gravitational and magnetic variation which we can measure. ",
"A lot like they have done with the Chicxulub crater"
] |
[
"Well - you'd get an thin event layer with minerals which are typical of impact environment: Coesite, Stishovite, micro-diamonds, perhaps even buckyballs. This horizon be best preserved in surrounding pelagic muds as well as ponds and lakes in continental environments."
] |
[
"Hard for me to say since I don't know much about the subject. Something that would be 'catastrophic' if it hit land...something that would wipe out a continent. A few km in diameter? Maybe something like this would make it through 5-6 miles of water to the ocean floor?"
] |
[
"Why does a discharged battery bounce higher than a fully charged battery?"
] |
[
false
] |
As seen in this video , why does this happen?
|
[
"The battery starts out as a caustic liquid and a ",
"manganese dioxide powder",
", metal bits and a membrane. As the corrosion reaction between those two proceeds, the powder changes to manganese oxide which could result in expansion, but also the powder granules becoming chemically and mechanically connected. I would hypothesize that you get a \"sandbag\" to solid transition, which would explain the video. The test would be to cut open the batteries carefully and see if the powder does indeed jam as i described, and also to make fake \"batteries\" with sand and glue, respectively.",
"Or it's just quackery ;) and a pretty crummy way to test battery voltage at any rate!"
] |
[
"My bad, I didn't even watch the video, I assumed it was the one that made the front page. And that's apparently because I'm an ass. I made my own video though and found yes there is a difference but can one tell a 1.2 from a 1.5 reliably between 2 batteries of the same brand, no not really unless you drop from a foot high. Can you tell a 0.08 to a 1.498 of the same brand, yes. Can you tell 2 different brands comparatively, no. I'll post the video when it's done uploading. Again my bad."
] |
[
" cut open a battery. If it is not charged, you will spray dangerous chemicals everywhere. If it is charged, you will spray dangerous chemicals everywhere, which carry a strong charge. This will probably result in electrical fire, pain and other bad things."
] |
[
"I've heard that yeast grows better in an acidic environment. Why is that?"
] |
[
false
] |
[deleted]
|
[
"I work in a place with industrial fermenters (but I work indirectly with the fermenters). However, from the literature I have, yeast that are fermenting produce acid on their own and will drop the pH of the solution. ",
"My information also mentions that yeast tolerate a lower pH better than bacteria. Bacteria inhibit yeast growth (or productivity. It's not clear which in my information). Keeping the pH as low as possible without negatively impacting yeast growth would keep your bacterial growth in check and increase your overall yeast productivity.",
"Edited for clarity."
] |
[
"This has been confirmed via people who do work with the fermenters every day. I also gleaned some other insightful information. Typically, you'll need some enzymes to break the long chain sugars down into the monosaccarides necessary for yeast to use. These enzymes work best at a particular pH range so the pH of our fermenters varies over time (we can raise or lower it depending on what we need). If you're factoring in enzyme use, that may also determine the optimal pH for the best yeast growth. (i.e. more enzyme activity = more food available for yeast use = more yeast growth)."
] |
[
"My theory with high school biology knowledge:",
"Some fermenting bacteria produce ethyl alcohol right? Since they normally increase the pH of the solution, dropping the pH might increase the rate of their reactions and growth. "
] |
[
"Do dogs actually enjoy playing fetch? Or do they think that is what they are supposed to do because they get appraisal when they return the ball?"
] |
[
false
] | null |
[
"There has actually been quite a bit of research having to do with two points explored in this thread. ",
"Do dogs experience joy? Do they have emotions? I don't know, but this ",
"blog",
" by Patricia McConnell, one of the leading Ph.D.'s in animal behavior frequently discusses this and does a great job of citing and discussing new articles in this field. It seems like it is likely.",
"Different dogs find different things reinforcing. A reinforcer is something the dog will work to obtain. Given a dog, you can test if it finds fetch reinforcing. Is the dog willing to work to play fetch? Go look around at some of the dog trainer pages on youtube, you will quickly find examples in both directions, you will see that some dogs do anything to play fetch and others will play fetch because they will do anything for the reinforcer they get for playing fetch (example: ",
"teaching a dog to enjoy fetching random things",
"). There are dog sports based on how much some dogs like to play fetch, ",
"flyball",
" - this video shows examples of dogs working for the opportunity to fetch) and frisbee. What makes this even more interesting, fetch is a secondary reinforcer, i.e., the dog doesn't need it to survive. Due to using other reinforcers, fetch can ",
" So a dog that doesn't initially \"like to play fetch\" can be \"taught\" to really enjoy it. Further, does the dog enjoy playing fetch, or just the tennis ball, or just casing the ball, or just brining it back . . .? "
] |
[
"There has actually been quite a bit of research having to do with two points explored in this thread. ",
"Do dogs experience joy? Do they have emotions? I don't know, but this ",
"blog",
" by Patricia McConnell, one of the leading Ph.D.'s in animal behavior frequently discusses this and does a great job of citing and discussing new articles in this field. It seems like it is likely.",
"Different dogs find different things reinforcing. A reinforcer is something the dog will work to obtain. Given a dog, you can test if it finds fetch reinforcing. Is the dog willing to work to play fetch? Go look around at some of the dog trainer pages on youtube, you will quickly find examples in both directions, you will see that some dogs do anything to play fetch and others will play fetch because they will do anything for the reinforcer they get for playing fetch (example: ",
"teaching a dog to enjoy fetching random things",
"). There are dog sports based on how much some dogs like to play fetch, ",
"flyball",
" - this video shows examples of dogs working for the opportunity to fetch) and frisbee. What makes this even more interesting, fetch is a secondary reinforcer, i.e., the dog doesn't need it to survive. Due to using other reinforcers, fetch can ",
" So a dog that doesn't initially \"like to play fetch\" can be \"taught\" to really enjoy it. Further, does the dog enjoy playing fetch, or just the tennis ball, or just casing the ball, or just brining it back . . .? "
] |
[
"Praise, not appraisal. Appraisal means evaluation, not praise."
] |
[
"How can a VTOL capable aircraft, like the V-22 Osprey, remain stabilized when added cargo throws off the balance of the aircraft?"
] |
[
false
] |
[deleted]
|
[
"There are calculations made by the Loadmaster (actual title of the person responsible) before each flight to making sure aircraft maintains a stable CoG with the addition of cargo and extra people. The loadmaster also packs the cargo in such a way so that it can be unloaded effectively, for example on military aircraft tactically important cargo (weapons/ammo) are stacked so they can be unloaded quickly in case of a combat situation.",
"Basically they've taken what dad's do packing the family car for a holiday and gone pro!"
] |
[
"Your question made me think of this:",
"http://www.youtube.com/watch?v=eWeXgvot2TI",
"As cadialg said a Loadmaster would ensure the weights are positioned correctly. Unfortunately, while passengers or crew members do not effect CoG that much a tank or heavy weight coming loose can be catastrophic."
] |
[
"I don't know about the V22 in particular, but when it comes to cargo, calculations are usually done before the flight so the cargo is positionned in a way where it will not change the position of the CoG too much.",
"As for crew members affecting the CoG, one guy moving from one end of the heli to the other would probably not affect the CoG noticeably on an aircraft the size of an Osprey. You would need to have a bunch of guys bunching up at one end of the aircraft to start causing issues."
] |
[
"How does the chemical structure of Taq Polymerase give it such a high resistance to heat?"
] |
[
false
] |
[deleted]
|
[
"In order to understand why Taq Polymerase can tolerate high temperatures, it may help to understand where the enzyme comes from in the first place. ",
"In deep water hydrothermal vents, you will find certain bacteria, T. aquaticus, that will thrive in temperatures and conditions that most organisms couldn't. Temperatures in this environment can easily exceed 100 degrees Celsius. In order to survive these temperatures, these bacteria must express proteins with an extraordinary resistance to high temperatures. To manage this, the protein sequence/structure is key in order to maintain the stability of what we call \"thermostable\" proteins, polypeptides that are functional at high temperatures. ",
"You may know from biochemistry that protein structure is highly dependent on hydrogen bonding networks and salt/ionic bridges. The ease for a protein to denature is inversely related to the number of hydrogen bonds and salt bridges that exist.",
"On the other hand, when thermostable proteins are present in cooler temperatures, for example room temperature for Taq Polymerase, the protein structure becomes rigid and the lack of flexibility disallows the enzyme to perform it's function optimally."
] |
[
"First, I appreciate you responding. I understand the background of Taq and the environmental conditions T. aquaticus lives in, but what I really want to understand, which you seemed to give me a good head start, is the ability of Taq to not denature at such high temps. and the chemistry behind why. My final goal is not to study Taq specifically, but to look at many thermo-stable chemistries that we happen to find in nature and apply it elsewhere. I am a biochemist by educational standards, but professionally a chemist."
] |
[
"I always thought, taq polymerase would contain an increased amount of disulfide bridges. This seemed logical, because H-bridge bonds in proteins are about 25 - 40 kJ/mol strong and the S-S is about 270 kJ/mol strong. But quickly googling it I found a supplier offering a taq that is supposed to contain no S-S bonds:\n",
"http://www.lifetechnologies.com/de/de/home/life-science/pcr/pcr-enzymes-master-mixes/taq-dna-polymerase-enzymes/taq-dna-polymerase.html",
"\nDoes anyone have further information on this?"
] |
[
"Is the sun capable of causing an EMP on earth substantial enough to do significant damage to the electrical grid?"
] |
[
false
] |
I've seen articles that argue how society would break down if the electrical grid were to be shut down but these articles often conflate the effects of a weaponized EMP designed to do just that with what common sense tells me are the far less significant effects of a solar flare compressing the magnetic field of earth. The whole thing smacks of fear mongering and sensationalized post-apocalyptic "prepper" fantasy. My question is this: As a followup question: If it is, how likely is it really?
|
[
"Yes. This actually occurred once before. This was prior to the wide spread use of electricity in homes but after the widespread use of the telegraph. The EMP pulse was so strong that operators were able to send messages without being connected to batteries using the electricity generated in the wires by the pulse. Fires started from arcing by telegraph lines due to the high current. So since we rely so much on our electrical system would/could cause severe damage to our society. As to chances of how likely not sure that would be more of a answer need a Solar specialist. On a brighter note the US has had some success in burying power and communications lines underground which mitigate the danger of a EMP. That would pretty much exhaust my knowledge of this topic. Hope someone with greater knowledge weighs in on this as would like to learn more on the topic."
] |
[
"I don't like to call it an EMP but it can still cause currents in any conductor. We call them ",
"geomagnetically induced currents (GIC)",
" and they can be destructive to the power grid. The most exciting demonstration of this was in 1859 where the most massive ever recorded flare, referred to as ",
"the Carrington event",
", caused a coronal mass ejection (CME) that produced very powerful geomagnetic storms.",
"What causes these currents is the ",
"magnetic field that has been dragged along with the CME",
" from the Sun squeezes and reconnects with the magnetic field of the Earth. How much the Earth's field is squeezed depends on the strength of the CME and the alignment of the fields (anti-aligned is ok, aligned is bad). This changing magnetic field produces an electric potential across the surface of the Earth.",
"In the case of Carrington, this potential drove such high currents in the telegram wires that some of them caught fire and some of them electrocuted operators. The total voltage is proportional to the length of the conductor and electricity grids don't don't have wires as long as telegram wires and they are much lower resistanceso we may not expect fires but we do still expect damage to transformers at the end of .",
"Just a few tens of Volts DC from these GIC will cause a transformer to overheat. If this continues over several hours then this overheating can become so bad that the pressure in the oil coolant causes the transformer to burst, taking out electricity supply.",
"There have been several, more modern events that have produced GIC that have damaged the grid. In the case of an event in ",
"march 1989",
" these GICS were big enough to take out 15 transformers in south africa and, even worse, cause a cascade of failures of transformers in Canada that resulted in large black outs, ",
"the entirety of Quebec lost power",
".",
"If a flare the size of the Carrington event hit we would expect this to be repeated on an even large scale.",
"The solar physicist in me has to constantly remind people that this risk is real and we should be working on early warning and protective systems (so they will pay us to research it) but at the same time I accept that these events are rare and the consequences? Not that scary.",
"The long term recovery could be problematic. An expert on GIC, someone who simulates them in order to find weak spots in the UK electrical grid, trying to find where transformers are most at risk once told me some things: there are limited companies who make transformers; transformers are widely varied so are not very interchangeable; ",
"there is no stockpile of spares that can be switched on and they can take years to make.",
"This could mean that a widespread global failure of transformers could take a lengthy time to fix but at the end of the day, it is just electricity. The grid can be repaired and solar flares+associated CMEs do not damage small scale devices."
] |
[
"https://en.wikipedia.org/wiki/March_1989_geomagnetic_storm",
"This happened in the era of electricity too, not just the Carrington flare."
] |
[
"Once light is produced does it ever stop?"
] |
[
false
] |
I just had a conversation with my Grandfather concerning the light that comes from distant suns and how we can still see that light even if the star is no longer there. So now we're curious if light ever stops moving forward once it's been produced.
|
[
"It won't stop unless it hits something. The light emitted by a distant star will continue to travel through space until it is absorbed by some particle of matter. This can be an interstellar gas cloud, a planet or another star. These will obviously only block part of the light. In addition, light can be pulled into a black hole if it happens to pass by one at a short enough distance.",
"The part of the light that doesn't encounter any of that will be able to travel beyond the time when the star has stopped shining. What we see on Earth is therefore not an instant picture of the star as it is at the current time, but rather what it looked like at the time the light was emited. In the case of the sun, we're looking 8 minutes into its past. The next nearest star is a bit more than 4 lightyears away, so we see events that happened there 4 years ago."
] |
[
"Photons are absorbed by matter and push electrons to higher energy levels. If/When the electron falls back to a lower energy level, it emits a photon. The wavelength and/or energy level of the photon (depending on how you want to look at it) determines how high an energy level the electron reaches and vice versa.",
"Its how solar cells work."
] |
[
"I have a slightly off topic question. I hope you may shed some light on it (pun). So as far as I know space itself is expanding. Was there light created at the advent of the Big Bang that did not hit anything and was able to keep going? If so could light outrun the expansion of the universe? Seeing as both the creation of space/time and light were instantaneous. Or could it be they are equally matched in a sense? Does this have anything to do with the cosmic microwave background radiation?"
] |
[
"Is it possible for a line/function to have a complex (imaginary) slope?"
] |
[
false
] | null |
[
"Functions from C to C can have imaginary slope: just take f(x) = ix. This is a perfectly valid function sending complex numbers to complex numbers.",
"Things get complicated because you can move in more than one direction in C, but the same sort of idea applies to such functions, the slope is the \"rise over run\": f(0) = 0, f(1) = i, so the slope is (i-0)/(1-0) = 1. Starting with this seed, you can develop calculus the same way as you would for real functions, just take the definition of a derivative and allow the terms to be imaginary.",
"This gets weird with functions like f(x+iy) = x-iy, the slope at 0 going in the real axis direction is 1 (compute the derivative lim_{h->0} f(h)-f(0)/h with h real) and the slope in the imaginary axis direction is -1 (compute the derivative lim_{h->0} f(h)-f(0)/h with h=xi imaginary). This is okay if you are thinking it as a function of two variables x and y, but if you want to think of it as one complex number you normally make the assumption that the slope in all directions is the same, such functions are called complex analytic and form the basis for the very rich theory of complex analysis which plays intricately with the complex arithmetic structure: complex polynomials are analytic for instance. The other direction, not requiring any compatibility of the two directions, leads to multivariable real analysis, the complex structure come up at all.",
"Addendum: a function from the real numbers to the real numbers will never have complex slope since the limit in the derivative is always real if it exists."
] |
[
"Something fun to think about:",
"We know from algebra that a line is perpendicular to a given line y = m*x if its slope is -1/m. Can a line be perpendicular to itself? It sounds absurd but we can approach the question with arithmetic. We'd need m to satisfy",
"m = -1/m",
"m",
" = -1",
"m = i, -i",
"Whatever it means for a line to have a slope of i in the cartesian plane, it's a line that's (somehow) perpendicular to itself."
] |
[
"Sure, why not? I can define a function y = (a + b",
"x. Plotting it is a little tricky. If you restrict x to be a real number, then one possible way to plot this function would be as a 3-D plot: one axis is the X-axis, one axis is the real Y-axis, and one axis is the imaginary Y-axis. You would still see it as a line. a determines the slope in the real Y-axis, and b determines the slope in the imaginary Y-axis.",
"You could also think of the above as two separate functions, one function representing the real part of y:\nR = ax",
"And the other function representing the imaginary part of y:\nI = bx",
"And plot those separately. You would see one line with slope a, and another line with slope b."
] |
[
"Since you can train cats and dogs to respond to their name, could you train any mammal to respond to it's name?"
] |
[
false
] |
[deleted]
|
[
"Basically all animal organisms have the ability to learn. If you activate a signal and then torture (or awesomely love) an animal, they will learn that the signal will soon result in torture (or awesome love). If you define the signal as their name, they will respond to it."
] |
[
"Do you have a citation for this? Isn't a sponge an animal?"
] |
[
"From the best of my knowledge a sea sponge is indeed an animal. I'm not explicitly knowledgeably about the nervous system of sea sponges (nor taxation studies) and it may well be possibly they are not intelligent enough to have intelligence be an evolution pressure in their evolution.",
"Most animals are higher order than other organisms and have developed enough intelligently to respond to stimuli in a manner characterized as having the ability to learn."
] |
[
"If you get a transplant (heart, liver, etc) can you feel pain from that area. If so, why?"
] |
[
false
] |
Title says it all. If you get a transplant of any kind, can you feel pain in that transplanted organ. If so, how does this happen? Do the nerves or whatever reconnect? How does the brain fix those connections? Thanks in advance.
|
[
"No, you cannot feel pain in the transplanted organ*.",
"This ends up being very important for certain things like kidney transplants. Normally, if your ureter (the tube connecting kidney to bladder) gets stopped up, it is incredibly painful. This is the pain experienced during a kidney stone. After a transplant, though, if the ureter gets stopped, it can go unnoticed and cause damage.",
"*Note: this is for internal organs.",
"Source: medical school"
] |
[
"No and yes. ",
"No because you generally do not reconnect the nerves, mostly because the function of the organ is generally independent of innervation, because you don't have to transplant the new organ to the same place the old one was, because results are poor with no proven advantage and increased morbidity due to extra surgical time.",
"Yes, if there is a certain degree of destruction of the tissue, inflammatory mediators are released and it can cause inflammation not only on the transplanted organ but on surrounding tissue, the surrounding tissue DOES feel pain and the patient will complain about pain on the transplanted organ. One example of this phenomenon can be observed in acute and hyperacute renal rejections. "
] |
[
"So doctors can reconnect/repair nerves, just not spinal nerves, is that correct?"
] |
[
"What is the difference between the way a white material reflects light and a mirror reflects light?"
] |
[
false
] |
If I understand correctly, we perceive white materials as white because they reflect most/all of the visual spectrum. It seems like mirror surfaces also reflect most/all light, yet my mirror isn't white. What is the difference between the way in which these materials reflect light?
|
[
"Mirrors produce ",
" -- light comes in at some angle and goes back out at an equal angle wherever it hits.",
"A generic white object, however, produces ",
" -- light come in at one angle but is reflected at a broad range of angles.",
"You can read more in this ",
"discussion",
"."
] |
[
"A white body is one with a rough surface that reflects all incident rays completely and uniformly in all directions. Light is scattered in all directions. ",
"In a mirror (and other transparent media), the light is not scattered. The incident rays of light are reflected or refracted ",
", so you get most of the rays back ",
" they hit the surface."
] |
[
"We see colors based on how light interacts with matter - for example, a green object lit by white light absorbs everything except for green light, so we see what isn't absorbed. The object has modified the spectrum of light from the source that now hits your eye.",
"Furthermore we think of color as a property an object has, but this isn't entirely true. The color we see depends on the structure of the object - the molecules that make it up, it's shape. The color of light you shine on it is also very important. The color we see depends on the interaction of light with mater. Everyone says that leaves are green, but they only ",
" green, and only ",
" green sometimes. Go outside with a red flashlight at night and you'll see the leaves don't look green at all. Another thing you can do is when you're out shopping at night look at the colors of the cars under the street lamps - suddenly all the colors are different. That red car you saw earlier might now look black under those lamps.",
"When you illuminate a white object with white light, all that white light makes it back to your eye. Put more formally, the material reflects every color (in the visible spectrum) that is incident on it. Let's take the example of snow, which is white because it scatters the incoming white light in all direction. The fact that white materials scatter light are why they appear different than a mirror (which can also reflect every color that is incident on it).",
"Mirrors are made from metals. Metals have a different electronic structure to them than other types of matter. Metals typically reflect all the colors of light equally. So whatever color of light falls on the mirror, is the same color that is reflected. As other users here have stated, mirrors preserve information about the angle at which light strikes the mirror. This is a result of the electronic structure of the metal. The incoming electric field of the incident light wave can drive the electrons in the material back and forth. In so doing, the energy of the incoming light is lost, that is, the incoming light is absorbed. Since moving charges create EM waves (light) and the electrons in the material are moving, they will now re-radiate an optical wave which has a fixed phase relationship to the incoming wave."
] |
[
"Is it possible for a particle to be made of only neutrons?"
] |
[
false
] |
I've recently learned the functions and such of an atom, and was wondering if it would be possible for a particle to be made of only neutrons, and what would be the implications of such a particle?
|
[
"There are multi-neutron resonances, but no bound states. For example, the dineutron and the tetraneutron. Because they’re unbound, they decay on timescales of 10",
" seconds."
] |
[
"That is the half life (order of magnitude). Only 0.1% survive 10 times the half life, only 0.0001% survive 20 times the half life and so on, so they are totally gone very fast."
] |
[
"Thats the half-life, or the mean lifetime. It’s an order of magnitude estimate, and both of those quantities are of the same order of magnitude."
] |
[
"How exactly do we feel pain from hot things?"
] |
[
false
] |
[deleted]
|
[
"Nah - Some nociceptors are definitely myelinated... First, we gots Aδ fiber axons. They are very myelinated and as a result the signal is sent really fast... they can allow an action potential to travel at a rate of about 20 meters/second towards the CNS. We also have slow C fiber axons. These only conduct at speeds of around 2 meters/second. This is because the axon is very lightly (or not) myelinated. This is why you feel a quick sharp pain immediately, followed by a dull ache a couple seconds later.",
"That hot stimuli is going to activate TRPV1 channels and cause an action potential in these thermal nociceptors. These nerve fibers (think Aδ and C) travel up to the dorsal root ganglion in the spinal cord where they meet up with the spinothalamic tract. The axons of these neurons cross the midline and ascend contralaterally along the anterolateral columns. These fibers terminate at the thalamus and send info to the somatosensory cortex where it is consciously processed."
] |
[
"We have nocioreceptors (pain) in our skin. They are unmeylinated free nerve endings. When they sense a change in temperature they depolarize causing a action potential. This goes up our lateral spinothalamic tract, then up to the VPL nucleus of the thalamus. From there we are aware that we are in pain but not exactly where. The thalamus sends the info via VPL nucleus to the postcentral gyrus the somatosensory cortex which tells us where the pain is...in our finger."
] |
[
"yhea iIjust left out the A delta receptors I was talking about c fibers specifically just for basics."
] |
[
"Do all vector quantities obey superposition?"
] |
[
false
] |
In my recent physics courses, we've studied electrical and magnetic fields. Both of these quantities obey superposition (fields created by independent sources can be summed using vector addition). Are there any similar quantities that DON'T follow this simple pattern?
|
[
"As a nice example of a nonlinear (pseudo)vector quantity in classical EM, you may have learned about the Poynting vector in your courses, it is related to the momentum carried by an electromagnetic field configuration, and is proportional to S = E x B. (vector cross product). ",
"Imagine we have some field configuration and simply double the source strengths so that E->2E and B->2B. Clearly S -> 2E x 2B = 4S, rather than 2S. Of course, S is not a field quantity the way that E, B, and A are. Field theories (quantum or classical) which have non-linear equations of motion are called interacting. As ",
"/u/mfb-",
" pointed out, a full quantum theory of EM (known as QED) is interacting and therefore the superposition principle is violated in extreme circumstances."
] |
[
"Everything nonlinear. That includes electric and magnetic fields if they are strong enough (the linear addition is only a really good approximation), gravity if strong enough (black holes), air resistance, ..."
] |
[
"The question that you are asking is confusing two different ideas. Superposition is a property of a system. In contrast a vector is an element of a set (a vector space). Vector fields (like B and E) assign a vector to every point in space.",
"We often mathematically represent physical quantities as a vector field. But the representation alone doesn't define a physical system. To do so we need a mathematical model that describes the interaction of one of more physical quantities. Superposition is a property of the mathematical model, it is not a property of the physical field itself.",
"A useful analogy is that we can express many physical systems as a matrix equation Ax = b. Here A is a matrix that represents the system and x is the unknown. In advanced math we generalize this notation, and we could for example express Maxwell's equation in this same form Ax=b (often you will see Lu=f). In this abstract notation A represents the differential operator, x is in the unknown E and B fields, and b represents the sources due to currents and charges. In this notation superposition is a property of A not x. ",
"To answer you original question, not all physical systems obey superposition. And given a particular physical field, there can both be systems that operate on that field that obey superposition and other systems that violate it. For example, the magnetic field in a vacuum is described by a linear system that obeys superposition. But the magnetic field in a ferromagnetic material is described by a nonlinear system that does not obey superposition, there is a hysteresis. ",
"I know the differences are subtle. But understanding these subtleties will really help as you advance to high level topics."
] |
[
"The space suit used on the moon, could they also be used on mars?"
] |
[
false
] | null |
[
"No. They were designed for the moon's gravity, about 1/6 earths. Mars gravity is twice the moons so the space suits would weigh twice as much, and therefore render the astronaut virtually immobile. Actually a light-enough space-suit for Mars exploration remains a significant problem.",
"Edit: the apollo space suits have a mass of 125Kg which = 275 pounds on earth and about 45 pounds in the moon. So on Mars they would weigh 90 pounds. So maybe \"immobile\" is an exaggeration, but certainly far too heavy to be lugging about for any time. "
] |
[
"LAYMAN: The moon suits had liquid cooling because it's so hot on the moon. It's very cold on Mars, so that part of the suit would not be appropriate. ",
"Here",
"'s a prototype NASA's looking at."
] |
[
"Those were designed over 40 years ago. I strongly suspect they'd provide a newer version."
] |
[
"Why did we evolve the inability to eat raw meat safely?"
] |
[
false
] |
Assuming that we evolve beneficial traits over time and that our ancestors were likely able to eat raw meat. Why would we evolve to not be able to eat raw meat? Surely that's disadvantageous?
|
[
"We are able to eat raw meat, provided it is fresh (or properly fermented/preserved) we just generally choose not to for three main reasons:",
"First, cooked meat tastes better. Incidentally, ",
"this doesn't seem to be limited to humans",
". Because this preference isn't limited to humans, we know it's not simply a human adaptation to keep us from eating uncooked meat. It's just a quirk of the way we perceive flavor.",
"Second, cooking meat removes parasites. I'm not talking about food poisoning from rotten meat, just parasitic worms and things carried in the flesh. Other animals simply put up with the parasites. Essentially all wild animals carry parasites, often in significant numbers. It reduces their health, but there's not much they can do about it. Human cooking lets us avoid these quite effectively, just like human weapons are effective at letting us avoid the predatory attacks that most other animals have to deal with.",
"Finally, cooking food makes the energy in it more available, requiring less energy for us to digest. Cooked meat requires less chewing (meaning less time/energy spent on chewing) and is easier to digest (requiring less energy to break down in the gut). More energy for less effort is an important trade off, and helps us support our big brains. We still ",
" eat raw meat, but it just makes it harder to get by. Other animals get a similar benefit from cooked meat, they just don't have the smarts to do it for themselves."
] |
[
"I would add, in most countries irradiation can be used to sterilize meat: killing any bacteria or parasites present and rendering it completely safe to eat raw or undercooked. However, due to people's fears and misunderstandings about the process, it is treated as a food additive, and has to be labeled \"treated with irradiation\" in big bold letters which tends to scare consumers off. When the technology was first coming out one of the big draws was that you could safely eat rare hamburgers. "
] |
[
"Second, cooking meat removes parasites....Essentially all wild animals carry parasites, often in significant numbers.",
"This is what I came here to say, and really want to emphasise. Wild animals are (relatively speaking) ",
"riddled with parasites",
"."
] |
[
"How will cooling as a result of the AMOC current stopping interact with general global warming?"
] |
[
false
] |
says that if this ocean current stops, it could make parts of the northern hemisphere colder. Would that mean just colder winters, or year-round? Would there still be more heat waves in summer? Would it make equatorial regions even hotter?
|
[
"Some housekeeping first, when commenting in AskScience, please ",
"remember our guidelines",
" for answering questions, specifically that answers should be based on peer reviewed sources when possible (and there are abundant sources in this case, so it's not a big ask) and should be free of speculation.",
"Now, with reference to the question, it's worth noting that what's spawned this latest spate of worry about the ",
"AMOC",
" in the press is this paper by ",
"Boers, 2021",
". While interesting (and worrying), Boers doesn't really help us in answering OP's question as this new paper is focused on demonstrating that the AMOC is nearing a tipping point (in the sense of ",
"Lenton et al., 2008",
") or transition to a significantly weakened state. To think about what the effects of said weakened state might be, we must look elsewhere.",
"Because the AMOC is a ",
"thermohaline circulation",
", the primary driving factor in destabilization of the AMOC is usually considered to be the introduction of a large pulse of freshwater in the North Atlantic (mostly from the melting of the Greenland ice sheet). As such, the effects of a (possible) destabilization of the AMOC is often considered in \"water hosing\" experiments, where basically two global climate models are run in parallel, one as a control and one where some amount of fresh water is \"hosed\" into the North Atlantic, reducing the sea surface salinity and influencing the working of the AMOC current. The anomalies (be those precipitation, temperature, etc) between the control and hosed models give us a sense of what the effects of a destabilized AMOC might be. If we look at an example of one of these hosing experiments, e.g. ",
"Jackson et al., 2015",
", we can start to answer the original question. Looking at Jackson et al's Figure 3, we can see on a global scale that destabilization of the AMOC leads to significant cooling (~3-5 degrees C lower average temp) and drying (~2-0.5 mm/day less precip) with respect to the control run in much of western Europe and Greenland. The effects are global though, as it suggests extreme drying in much of the tropics and a broad pattern of cooling in the northern hemisphere and warming in the southern hemisphere. Zooming into western Europe and thinking seasonally, this work suggests that the cooling is most extreme in the winter (e.g., Figure 4). Precipitation also changes seasonally with most of Europe seeing less precipitation in general, but slightly more precip in the winter in the British Isles, and slightly more precip in the summer in southern Europe (Spain, Italy, Greece).",
"Ok, so, now some caveats. First and foremost, this was just one example and not necessarily representative. Some of the challenges with considering results like those above are that (1) we don't know exactly the right forcing to apply in these models and the effects will differ as a result, (2) the above example was driving both the control and the hosing experiment with a constant, 1980 level of CO2 so from this result at least it's hard to say how this would play out in the context of climate change more broadly, and (3) importantly, many papers highlight that even with the same forcing, different models make different predictions of what will happen (e.g., ",
"Stoufer et al., 2006",
"), though the general patterns for many of them remain the same. Finally, AMOC related issues, i.e., whether it will really destabilize and what will happen if it does, has remained a pretty fraught issue. Whether it's likely that the AMOC will weaken but not really destabilize (e.g., ",
"Schmittner et al., 2005",
") vs it being likely that it will fully destabilize (e.g., ",
"Liu et al., 2017",
") has been an argument for a while. Similarly, as highlighted in Stoufer paper above (and many others, e.g., ",
"Williamson et al., 2018",
"), the extent to which the models agree on the effect of varying degrees of AMOC disruption is also problematic. Whether this new Boers paper will move the needle much in the debate remains to be seen."
] |
[
"Neither of these are likely outcomes (or maybe even possible outcomes) based on the sources above. Coming at this from the perspective of the Jackson et al, results, as for an \"ice age in Europe\", weakening/destabilization of the AMOC certainly leads to cooling of Europe but not necessarily to the point where you'd expect a reformation of something like the ",
"Fennoscandian Ice Sheet",
" (plus the models suggest a drying along with the cooling for Europe). As for \"desertification in the American northeast\" this is not suggested in the Jackson results at least. There you see a modest reduction in precipitation (<0.5 mm/day), but also less evaporation, so on balance, it gets wetter in northeastern North America (i.e., less rain, but an even larger reduction in evaporation). All of this is predicated on one model, so the caveats above are extremely important and the answer might differ depending on a lot of details. Also critical for questions like this are things like this are the duration of the effect and how this would play out in concert with rising CO2 and global temperatures as a whole. There may be models out there that look at a weakening AMOC along with a projected CO2 forcing, but I didn't see much in my admittedly quick digging over my morning coffee."
] |
[
"What is the likelihood of catastrophic outcomes like ice age in Europe or desertification in the American northeast coast?"
] |
[
"Whats the main difference between a sociopath, psychopath and a narcissist?"
] |
[
false
] | null |
[
"Poor judgment and failure to learn by experience ",
"Failure to follow any life plan.",
"Can you expand on these two? As I understand it all of the APD types are essentially caused by a lack of empathy and a lack of fear/anxiety (and likely a blunting of emotions in general). These two traits you listed stand out to me though as I can't see why they would be related."
] |
[
"Hmm... that's a good point, a reduced negative feedback enforcement. Psychopaths are very logical though so you would think they would say, \"hey, this clearly doesn't work, let me try something else.\" Plus it kind of goes contrary to the perception that many psychopaths are ",
" successful, arguably more so than the average person due to their lack of empathy or consideration for others. I have no idea what the average psychopath is as far as success goes, but CEO's, business leaders, etc have higher rates of psychopathy than the average population.",
"Just spitballing here, but for that second point, failure to follow any life plan, I could see a lack of love or any real emotional draws (short of anger which seems predominant) could leave a lack of direction. If you don't truly enjoy anything, love anyone, etc, then you may simply not have any real goals or desires other than to \"feel good,\" which usually comes down to short term gratification via drugs, sex, or thrill seeking."
] |
[
"There is a lot of overlap between them. The main point of a narcissist is someone who thinks they are wonderful, and they cannot comprehend or tolerate the idea that they are not wonderful. Narcissists can be very entertaining (think Jenna from 30 Rock) and very gracious so long as you do not run counter to their view of themselves. Narcissism comes in two flavors: stable and unstable. The difference between the two is what happens when their view of themselves is challenged. An unstable narcissist will react with harsh words or violence, and a stable narcissist will simply not listen. ",
"Psychopathy is a cluster of traits that isn't clearly one thing. Subscales of psychopathy include boldness, fearless dominance, insensitivity to pain/punishment, and a couple others. Cleckley defines it as having these traits (taken from ",
"the wikipedia page on The Mask of Sanity",
"):",
"Superficial charm",
"psychoneurotic",
"remorse",
"shame",
"antisocial behavior",
"egocentricity",
"love",
"insight",
"Suicide",
"Sex life",
"These two personality traits are part of the \"dark triad\", which also includes Machiavellianism. This trait is the desire or ability to manipulate others behind the scenes. ",
"Sociopathy is not something I know as much about. What I understand is that it is the desire to hurt others. While a psychopath will hurt you if you get in the way of their goal, for a sociopath, the goal is to hurt you."
] |
[
"Why does the Spin commute with the position but not with the momentum?"
] |
[
false
] | null |
[
"Yes, the spin Hilbert space is separate from the coordinate-space. These operators don’t care about each other because they act in different spaces. If you have some state describing a position and a spin, this state lives in a tensor product space. And when you say you have a “spin operator”, what you actually have is I x S, where I is the indenting operator in space, x is the tensor product, and S is the operator in spin space.",
"So the spatial part is just identity, and commutes with everything in that space."
] |
[
"Spin operators commute with both position and momentum operators."
] |
[
"Oh, why the spin commute and the orbital angular momentum not?\nIt is because the spin lives in a space of finite dimension and the others in one of infinite dimension?"
] |
[
"What happens whith the excess of kinetic energy that isn't being acumulated when a rocket is flying at light speed and keeps thrusting in perfect vacum?"
] |
[
false
] |
I'm sorry, another light speed question. What happens with that energy? Does it just disappear?
|
[
"Well, a rocket can't fly at light speed so the question doesn't really make sense. "
] |
[
"If a rocket is flying just under light speed but continually being accelerated (so its kinetic energy must increase), the kinetic energy will increase without bound without the rocket ever reaching the speed of light. The full equation for kinetic energy is KE = mc",
"/sqrt(1-(v/c)",
") - mc",
", which reduces to KE = mv",
"/2 for v much smaller than c, but goes to infinity as v approaches c.",
"Here's a graph",
" which plots KE + mc",
" as a function of velocity if you want to see how it looks."
] |
[
"Those are not the same thing at all..."
] |
[
"Does the Planck charge have any relation to the natural world?"
] |
[
false
] |
I'm reading about Planck units, and the Wikipedia for the Planck Charge states that its value is about 11.706 times greater than the elementary charge, . Why is there this mismatch? Is there no connection at all between and the Planck charge? I thought Planck units were fundamental units, derived from the nature of the universe. So, does this mean that isn't elementary after all? Yet, every time we observe electric charge, it's always in integer multiples of . Are there any phenomena that occur, or are theorized to occur, that have integer multiples of the Planck charge, instead of the elementary charge? If the Planck charge has no natural phenomena linked to it, does that imply that it is meaningless?
|
[
"Though all charge seems to be quantized in units of 1/3 e.",
"Actually, you can still say that charge is quantized in units of e, regardless of the 1/3. This is because charge only ",
" in unit increments of e. So for example, an up quark (+2/3) changing into a down quark (-1/3) exhbiits a change of 1e, and so forth.",
"We also model other charges similarly. For example, weak isospin for many particles is either +1/2 or -1/2, but we still say it is quantized in increments of 1 because you can only change weak isospin by units of 1.",
"Another reason for modelling weak isospin this way is because you need a system with only two states (+1/2 and -1/2) that are separated by 1 unit. You cannot possibly have that if the charges themselves can only take integer values; you could only have either 1 state (weak isospin of 0) or three states (0, 1, -1).",
"Similarly for electric charge -- you need to be able to represent one particle having twice the charge (and opposite sign) of the other particle, but only being one unit's worth of difference apart. So you must use thirds to represent that.",
"My point is, when we say something is \"quantized\" that means it changes, or propagates, in units of 1. That doesn't mean the initial or final amounts have to be in units of 1. For example, photons are the \"quanta\" of the electromagnetic field; they carry an amount of energy proportional to Planck's constant h, and also proportional to their wavelength. Yet, a free particle can have ",
" wavelength, and therefore any energy (the distribution is continuous), but it can only emit photons with an amount proportional to Planck's constant. Despite the fact that free particles can have any energy, we still say that the electromagnetic field is quantized.",
"Hope that makes sense!"
] |
[
"I thought Planck units were fundamental units",
"They're not, there's not anything special about planck units.",
"So, does this mean that e isn't elementary after all? Yet, every time we observe electric charge, it's always in integer multiples of e.",
"Quarks have non-integer charge, an up quark has, +2/3 e for example. Though all charge seems to be quantized in units of 1/3 e.",
"If the Planck charge has no natural phenomena linked to it, does that imply that it is meaningless?",
"The planck charge does have natural phenomena tied to it. It's just as valid to say that the charge of an electron is e or ~1/11.706 planck charge. "
] |
[
"No, not really. It's just the natural unit formed with the choice of constants used in the Planck system, where Coulomb's constant is 1, so the force between two charges is just e",
" /r",
" . The ratio of the fundamental and Planck charge is the square root of the fine structure constant. There are other sets of natural units where e is 1 and Coulomb's constant is not.",
"It's a really useful example showing that Planck units aren't these magical fundamental quantities that some people think they are."
] |
[
"Why is the polio vaccine still needed in the US?"
] |
[
false
] | null |
[
"I’m guessing that near eradication in the US population, which has large numbers of people visiting from other countries, is not considered to be enough to keep such a horrible disease at bay. Im young enough to have gotten immunized, and I would hope that everyone else in the world will be too one day, but we aren’t. "
] |
[
"Hepatitis A is also transmitted via a fecal-to-oral route and the US has several outbreaks right now. Advances in water cleanliness in the US are great, but not foolproof. Ask Flint, Michigan. Ask anyone who uses well water. Contamination of food and water can and does happen every day, even in the first world. There’s still a polio vaccine in the US, because the US doesn’t exist in a vacuum. People visit areas high in polio or people from those areas visit the US. The 5% “unprotected” by the vaccine are still protected by herd immunity. That is, if everyone around them is vaccinated, the risk of them coming in contact with an infected person is exceptionally low. "
] |
[
"It's a virus. It doesn't wave a little white flag just because you chased it outside your national borders with vaccines. Evolution doesn't just quit.",
"It improves and it waits because that's all evolution really knows how to do. The ascension of the antivaxx movement in the U.S. may create a situation where organized governmental response doesn't happen and herd immunity fails. Maybe the viruses deserve to win because in a way they're better than you, and are not burdened with true intelligence or doubt."
] |
[
"Why is it that animals such as birds are \"scared\" of humans, while smaller insects like flies are not?"
] |
[
false
] |
[deleted]
|
[
"Birds have a lot more \"brainpower\", which is metabolically expensive but gives them greater behavioral flexibility than insects. In general, birds are more capable of learning about humans (or even recognizing them as distinct entities), while insects rely on high reproductive rates and a series of inflexible but very fast and effective escape maneuvers.",
"EDIT: flies in particular might be better off being attracted to humans, since we aren't particularly good at killing them and tend to be associated with good food sources."
] |
[
"Not only brain power. It's mainly the quality of sight. Insect eyes do not enable recognizing a human as such. Even dragonflies (with their relatively enormous eyes) have very poor eye sight compared with birds.",
"http://cronodon.com/BioTech/Insect_Vision.html"
] |
[
"Please remember that AskScience is not for guesses or speculation, no matter how logical it may seem. Thanks!"
] |
[
"Did Neanderthals make the cave paintings ?"
] |
[
false
] |
In 2018, Dirk Hoffmann et al. published a Uranium-Thorium dating of cave art in three caves in Spain, claiming the paintings are 65k years old. This predates modern humans that arrived in europe somewhere at 40k years ago, making this the first solid evidence of Neanderthal symbolism. . Widely covered, This of course was not universally well received. Latest critique of this: 2020, team led by Randall White responds, by questioning dating methodology. . . Covered Hoffmann responds to above ( and not for the first time ) Earlier responses to various critiques, and 2020, Edwige Pons-Branchu et al. questining the U-Th dating, and proposing a more robust framework covered Needless to say, this seems quite controversial and far from settled. The tone in the critique and response letters is quite scathing in places, this whole thing seems to have ruffled quite a few feathers. What are the takes on this ? Are the dating methods unreliable and these paintings were indeed made more recently ? Are there any strong reasons to doubt that Neanderthals indeed painted these things ? Note that this all is in the recent evidence of Neanderthals being able to make fire, being able to create and use adhesives from birch tar, and make strings. There might be case to be made for Neanderthals being far smarter than they’ve been usually credited with.
|
[
"Well, neanderthals existed concurrently with humans and were just as smart as us. They eventually interbred with humans and faded/melded into homo sapiens. (As homo sapiens are breeding machines, Homo Neanderthalis couldn't keep up.) I would say its entirely possible that the paintings could have been drawn by them, depending on the region. (Neanderthals lived in mid to northern Asia/Russia)"
] |
[
"Furthermore, assumptions like this sometimes form the basis for entire scientific careers.",
"Reminds me of what happened with dating when humans moved to North America. You basically had to have an entire old guard die before evidence would be accepted that humans in NA predated Clovis. You had evidence of pre-Clovis people in Florida and other locations just discarded entirely because the scientific establishment was certain of this fact and to admit the possibility that they were wrong would ruin a lot of careers this particular field."
] |
[
"Furthermore, assumptions like this sometimes form the basis for entire scientific careers.",
"Reminds me of what happened with dating when humans moved to North America. You basically had to have an entire old guard die before evidence would be accepted that humans in NA predated Clovis. You had evidence of pre-Clovis people in Florida and other locations just discarded entirely because the scientific establishment was certain of this fact and to admit the possibility that they were wrong would ruin a lot of careers this particular field."
] |
[
"What do bees see?"
] |
[
false
] |
A few days ago I learned that bees don't have the ability to see the color red, just like us humans can't see UV. What do they see when something is red?
|
[
"It's tough to really say what bees \"see\". We can, however, point out what they ",
" see. It's important to note that not all bees are red-colorblind, and even then, most can discriminate shades of yellow and orange. As for the red flowers that don't have shades of yellow or orange to help bees out, it looks like they're mostly pollinated by beetles (Dafni, et al., 1990). But because most flowers aren't exclusively red (they have varying shades of colors), they get visited by bees. Good for them!",
"As for what they \"see\"? They see what colorblind folks see, which is to say that the reds are dominated by whatever neighboring colors are around. If they're in a completely red surrounding, it will turn out to be completely absent of color and muddy looking. They see what we see when we look at a Blackbird (who often have UV surrounding their beaks): nothing extraordinary or unusual, we just don't/can't detect anything. For a pretty in-depth look at their tri-chromatic visual system, I recommend Chittka and Wells' (2004) chapter! ",
"Dafni, A., Bernhardt, P., Shmida, A., Ivri, Y., Greenbaum, S., O'Toole, C., & Losito, L. (1990). Red bowl-shaped flowers: convergence for beetle pollination in the Mediterranean region. Israel Journal of Botany, 39(1-2), 81-92.",
"Chittka, L., & Wells, H. (2004). Color vision in bees: mechanisms, ecology and evolution. In: Prete, F.: ",
"; MIT Press, Boston pp. 165-191."
] |
[
"Whoa -- this is awesome! Thanks for sharing -- going to play with this for an hour or four."
] |
[
"Whoa -- this is awesome! Thanks for sharing -- going to play with this for an hour or four."
] |
[
"When selling your blood plasma, does the payment outweigh the cost of energy and nutrients (food) to replace the lost plasma?"
] |
[
false
] | null |
[
"Also be sure to factor in the several hours/days afterwards during which you will feel very lethargic and likely not be able to do anything productive. Overall it is not worth doing it for the money - it is primarily a selfless act so I imagine the money is meant more as compensation than actual pay"
] |
[
"In the modern world food calories are cheap. Two pounds of flour or around 1 kg is around $1.50. Let's say that prepared it costs double that, so $3 per kg. According to ",
"the label",
" 30 g is 100 calories. So, then you are paying $3 for 3000 calories. That's ridiculously cheap when you think that is probably greater than sustenance for a family of 3 for a day (let's say two adults at 1200 cal + child at 600 cal). While flour is not a complete protein source by any stretch of the imagination, I'd bet you can get there with rice and beans for less than double that.",
"How many calories does it take to synthesize plasma? That's a bit of a hard question. ",
"This site",
" says 450 cal in 500 ml of total blood. Their math seems legit. ",
"For plasma, it may be a bit lower if they are pheresing your RBCs back into you. Say your serum total protein is 7 g/dl, so in 500 ml around 35 g. Sugar is around 120 mg/dl, so figure 600 mg. Total cholesterol is around 150 mg/dl so around 750 mg. Total triglycerides are around 150 mg/dl as well, so around 750 mg.",
"35 gm of protein * 4 kcal/gm = 140 cal.\n0.6 mg of sugar * 4 kcal/gm = 2.4 cal\n1.5 gm of fats * 9 kcal/gm = 13.5 cal",
"So total from just those sources is around 155 calories, give or take. However, it probably takes at least double that to resynthesize the stuff. No matter how you look at it, you could probably easily resynthesize what you lost with under $1 of food expenditure.",
"EDIT: imperial to metric conversion wrong. Corrected. Satellites have been lost for similar reasons."
] |
[
"My ",
" is that most people eat more of most nutrients than they need, and that selling plasma would mostly mean a more-efficient use of the same diet, rather than an increase in eating. Even if the plasma requires increased eating to replace, much would depend on the ",
" of food required. (Would you want ",
" food, or basic potatoes?)"
] |
[
"Would bee hives grow larger if we didn't harvest their honey?"
] |
[
false
] | null |
[
"Not significantly. Not removing the honey instead triggers swarming and the foundation of new hives, or they get to a point the queen can't lay enough in a day to grow the population.",
"Honey is a hives food stores for winter. Adults need only carbohydrates to survive since they do not grow or repair and honey provides that. Bees have no mechanism to know how long or cold winter will be during the warm seasons so they store as much honey as possible which ends up being well in excess of their needs. ",
"When winter starts approaching the queen will stop laying (depending on environment, tropically located queens might never shut down laying) and the population of the hive declines. This is partially to ensure that there is enough honey, a smaller population needs to eat less. Its also because in the off season they have no reason to have large populations. There is less brood to be raised, no nectar or pollen to bring in and generally less work to be done. ",
"After the winter solstice and the first pollen availability the queen will start laying again. The population starts to climb but it takes population of adults to care for the young and raise them so the queen can't just lay 2000 eggs a day. She has to limit the growth for a while so there are enough adults to care for the larva. ",
"Assuming everything goes well and winter ends in a timely fashion the hive will grow significantly and just before the major spring nectar flow it will swarm. Half or more of the bees and the old queen will leave the hive and found a new hive somewhere else. A new queen will be raised in the old hive. In both space is freed up because there is a gap in brood production. In the old hive because it takes 16 days for a new queen to mature, a week or so for her to start laying and 21 days for her first brood to emerge. In the new hive the old queen can start laying as soon as there is comb, less than a day after its founding but space is limited and its still 21 days before adults emerge.",
"Both hives then go about collecting for winter. They will draw as much comb as possible given the available space and fill it with brood, honey and pollen. Situations can arise where brood nest space is backfilled with honey when they run out of space to build comb but this triggers additional swarming reducing the population. ",
"Given a very large space they will store more and more honey but the brood space has a limit. The queen can only lay so many eggs a day (the max is generally given as 1500-2000). Once those emerge as adults they have a summer life span of apr 45 days and work themselves to death. The queen can keep up with the turn over but at a certain point (50,000 workers or so) she can't lay fast enough even if there was space available to increase the population further. They will instead just store more honey. This is the honey we take as beekeepers, that honey they clearly have in excess and will never eat in winter.",
"I am a beekeeper.",
"EDIT: More info:",
"Experiments have been done to show bees look for a space ",
"apr 40L in size for a hive with an opening about a 10-15 cm3",
". So in nature they aren't looking for giant spaces anyway. The standard American hive the Langstroth with 10 frames is apr 40L. The standard is also to have 2 of those boxes for the brood nest so double what is found in nature and then to add additional boxes just for honey collection. Beekeepers also manage hives to reduce swarming (we don't want half our bees flying away just before peak production times). We also protect them from predators, pests and diseases found in the wild. If anything managed bee hives that we take honey from tend to have larger populations than those found in nature.",
"Down here in the south its not unusual to find Africanized bees in boxes as small as a water meter rather than the 40L 15' up that European ones prefer. These small hives swarm as often as the can, nearly once a month. Those small size hives produce virtually no honey and if winter is cold (like North Florida cold a few freezing nights a year) they can't survive the winter."
] |
[
"Adults need only carbohydrates to survive since they do not grow or repair and honey provides that.",
"That is fascinating in itself. To have a final rigid form that needs no protein is so ",
".",
"Meanwhile we just shed skin cells like they are going out of style."
] |
[
"This is one reason why I consider bees to be more like appendages, with the hive being the “individual” in the sense we think of with most animals. "
] |
[
"A marine biologist friend of mine told me that studies have shown that animals who are in overpopulated habitats are much more likely to exhibit homosexual behavior. Is there any validity to this?"
] |
[
false
] |
If so could I get some elaboration on why this happens?
|
[
"There are the ",
" by John B Calhoun.",
"Essentially he created a perfect system where there were no predators, plentiful food and the initial rats were all healthy - the only constraint was available space. This allowed extensive breeding, particularly early on when there was a lot of spare area.",
"Then the population hit a limit. \"After day 600, the male mice just stopped defending their territory, listless mice congregated in the centres of the Universe. These gangs would burst into pointless and sporadic violence. Females stopped reproducing and even started attacking their own young. Mortality rose phenomenally. Roaming mice either attacked or ",
", cannibalism and other acts of depravity consumed them. These were the feral ones. Then there were the ‘beautiful ones.’\"",
"But upon that point society was broken and each time it would never recover.",
"Here's one such link, but this was simply the first I've found; there is a lot out there if you google:\n",
"http://www.mostlyodd.com/death-by-utopia/",
"In particular, you can look up the term ",
", which he coined dealing with this unrecoverable change in societal behaviour. ",
"http://en.wikipedia.org/wiki/Behavioral_sink",
"Edit: As Provokateur says, it reads as though it was more a case of homosexual acts, rather than actual homosexuality."
] |
[
"This purpose of the experiments was not to portend some imminent doom for humanity, in fact Calhoun was trying to be positive. He wanted to change cities, his remedy to the behavioural sink was creativity. By changing society and changing how we designed our cities we could avoid becoming mired, stagnant, and eventually, dead as a dormouse. Over 100 Universes were designed after he published the paper in 1973, these ones designed with the aim of promoting creativity and reducing stagnation.",
"The fact that nearly everyone who read his research used it to draw out doom caused John Calhoun to become distraught. They missed his point, but still he pressed on. Regardless of what was said, there was science to do."
] |
[
"Fuck that's scary"
] |
[
"Does all the nuclear fuel in an atomic bomb undergo fission, or is some scattered before it can go critical?"
] |
[
false
] |
Is it possible that some fissile material is blown away by the force of the explosion before it can start reacting itself? On a related note, could the detonation of a nuclear weapon in close proximity to a reactor's fuel rods (unshielded for this hypothetical) cause them to explode?
|
[
"Most of it does not undergo fission, only a small fraction actually does.",
"It takes about 0.22 Moles of fission reactions to produce 1 kiloton of energy. So for the nuclear weapon that destroyed Nagasaki (21 kilotons) it took about 4.6 Moles of fission reactions to produce that amount of destructive power. Pu-239 has an atomic weight of... 239 amu, so 4.6 Moles would weigh very close to 1.1 kilogram (about 55 cm",
" or just under 2 tablespoons). In comparison, about 6.2 kilograms of Plutonium were used in that bomb, so only about 17% of the fissionable material underwent fission.",
"In the case of the \"Little Boy\" bomb dropped on Hiroshima about 0.8 kilograms out of 64 kg of Uranium fissioned, or about 1.25% of the total.",
"As far as a bomb going off near fuel rods, there are interesting aspects to that. The thing that makes a fission bomb \"go\" is that the population of neutrons grows at a geometric rate. And this occurs because when the bomb has been assembled and is detonating a neutron produced via fission is about as likely to run into another fissionable nucleus as it is to escape from the core. This is as much a function of density as it is of sheer size, which is what implosion assembly (which increases density) is all about.",
"So if you have a hunk of fissionable mass nearby that isn't at the proper density you aren't going to magically be able to get it to start magnifying the number of neutrons just by throwing more at it. If that could happen it could happen with the number of neutrons already in the reactor.",
"However, that doesn't mean nothing happens, something actually will happen. If you increase the neutron flux on fission fuel rods you won't get them to spontaneously have fission chain reactions that spiral out of control. But what could happen is that for some of the neutrons that left the bomb they could multiply their energy release by causing a fission reaction.",
"In general you'll have on the order of as many neutrons produced as the number of fission reactions that have taken place, so if you have a huge amount of fissionable material packed tight around a bomb you could easily double the yield in this way.",
"Note that because we're just talking about one off fission reactions from fast neutrons and not multiplying neutrons this can happen even with natural U-238.",
"And this is exactly how real bombs work. Often they use a \"tamper\" of heavy metal round the core of the bomb to delay the bomb blowing itself apart quickly (so that the nuclear reactions have more time to run before everything is too spread out). And if a natural Uranium tamper is used then you can increase yield.",
"The Tsar Bomba bomb, for example, was designed to use Uranium around the 3rd fusion stage, to make use of the neutrons produced by the fusion reactions. Such a design would have doubled the yield of the bomb (to 100 MT). But in testing the Soviets decided to avoid producing so much radioactive fallout from all of those fission reactions and instead used a different material for the tamper, resulting in a 50 MT yield in the test."
] |
[
"Since the other comments addressed your questions I would add a little bit about what determines the efficiency. The efficiency depends on a few factors, the largest being how long the super critical mass is held together. In the case of a gun type weapon, you are shooting a plug into a cylinder. In that case the inertia of the plug causes it to blow apart quickly. ",
"An implosion type has a symmetrical geometry. The inertia from the implosion actually helps to keep the critical mass together. You would want the first neutron to start the reaction at maximum compression or slightly before. The inertia of the material will hold the bomb together for the microsecond of fission that occurs. In this case you get around 70 generations of fission. The last three are where all the energy comes from. ",
"Efficiency is also determined by the neutron initiator. You would need a large burst of neutrons timed correctly to cause a nuclear explosion. The early designs used alpha-n sources. They work, but are not efficient. More modern devices probably use a D-T gun to generate a large burst of fast neutrons. Along with the concept of efficiency, changing the time of the neutron burst could change the yield. This is possibly how they do dial a yield weapons."
] |
[
"It is because the number of atoms involved in each fission generation is an exponential function.",
"Assume each generation is twice the size of the previous. The last one is half of all the energy release, the one before it is 1/4th of the total and the 3rd to last is 1/8th."
] |
[
"How did scientists find out the composition of DNA?"
] |
[
false
] |
I was reading journal which discusses the possibility that a bacterium could use arsenic instead of phosphorus in its DNA which turned out to be false. This led me to wonder how scientists first isolated different components of DNA and what technique they used. I was also wondering what modern techniques could be used to find out composition of DNA. Thanks!
|
[
"You mean elemental composition? Well, ",
"Miescher",
" first isolated DNA, extracting it from infected medical bandages. It was already known in Miescher's time that it contained phosphorus, I believe from ashing experiments. At the time it was routine to decompose compounds using acid, basic, and high temperatures and characterize the breakdown products. ",
"You can read about the history in Box 3, here",
".",
"Nowadays, we'd probably use ",
"X-ray fluorescence",
" to quantify the elements in DNA, but I'm not an expert in that technique. ",
"As for chemical composition, ",
"Kossel",
" determined that it contained four nitrogenous bases, and ",
"Levene",
" found they were linked in a phosphate-sugar chain. ",
"Chargaff",
" found that any DNA will have equal ratios of Adenine to Thymine, and Guanine to Cysosine, which was key to later figuring out the structure of DNA. ",
"The paper you link to was unfortunately what appears to be a bout of wishful thinking gone awry, which is too bad, because it would be interesting if it were true!"
] |
[
"The question was about chemical composition, not sequence. XRF has never been used for sequencing. All the technologies you describe depend on a lot of prior knowledge of DNA, and aren't applicable to characterizing the chemistry of an unknown substance. "
] |
[
"It only becomes straightforward ",
" somebody has already figured out what the protocol should be!"
] |
[
"Are there any materials that are plasma at room temperature?"
] |
[
false
] |
If different materials, can have different melting or boiling points, that's should apply to plasma too, right?
|
[
"Because it takes energy on the order of electron volts (eV) to ionize an atom and 1 eV corresponds to a \"temperature\" (actually kT) of around 10,000 K, there are no materials that are plasmas at room temperature without any external electric or magnetic fields. However, there is a whole category of plasmas called low-temperature plasmas, which are created when electrons are heated to a very high temperature by an electric field, but neutral atoms and ions stay near room temperature. Low-temperature plasmas are also typically low-density as well, one good natural example is the northern lights. They glow because of gases in the upper atmosphere being ionized by solar winds."
] |
[
"Yes, neon lighting is another example of a low temperature plasma. It consists of a low-density neon gas with a high voltage applied to it."
] |
[
"Would that be true for neon lamps as well?"
] |
[
"Does the body become physically dependent on caffeine for energy, or does the body just build up a tolerance?"
] |
[
false
] |
Let's say one were to drink 5 cups of coffee per day for 6 months straight, then quit suddenly. Aside from physical withdrawals such as headaches etc, you wouldn't be any less tired than you were pre testing, right?
|
[
"To oversimplify greatly:",
"Caffeine is an adenosine antagonist. It takes up spaces where the neurotransmitter adenosine should bind without activating them. In other words, it \"mutes\" your body's response to that neurotransmitter. Adenosine, to simplify grossly, slows down your neurological processes, you could say it contributes to you feeling tired.",
"When you develop a tolerance to caffeine, it means that you become more sensitive to adenosine. So even though a smaller amount makes it \"past\" the caffeine to do its job, you've become (over-)sensitive to the point where this is normal.",
"Now, when you stop taking caffeine, adenosine starts appearing at the \"normal\" rate again, but your receptor sites have adjusted to the smaller rate. As a result, adenosine now has a much greater effect at this \"normal\" level than it did before you started with the caffeine.",
"At this point, yeah, you're going to feel really tired. After a couple of weeks, your receptivity to adenosine will \"down-regulate\" again and you'll feel normal, but until then, expect tiredness.",
"tl;dr: Caffeine doesn't give you energy, it keeps you from feeling tired. If you adjust to having it, and then stop taking it, you will feel really tired for a while."
] |
[
"Tip of my hat to you sir!"
] |
[
"I understood that caffeine intake corresponds to an increase in adrenaline. Am I wrong to understand that adrenaline gives you energy?"
] |
[
"Is their a psychological or physical benefit to tennis players who \"moan\", \"groan\" or scream every time they hit the ball?"
] |
[
false
] |
I was visiting my grandma the other day. While watching tennis I noted how some players "moan","groan", or scream with every hit they give. It annoyed me terribly so I asked my grandma (who watches a lot of tennis) why they do it and she couldn't give me answer. She did, however, note that it only started a couple of years ago with Venus Williams - though she may be wrong since she is over 80 years old. So if tennis players didn't always do it, why do they do it now? Did someone realise they can hit the ball harder or more accurately? Is it a scare tactic to use against other players? Thanks in advance! Edit: Seems like the word I was looking for is "grunting". Thanks for the great answers. Edit 2: Just realised I used the wrong "there". I wish I could change the title now...
|
[
"Comming from a martial arts background where we scream at the end of some of our techniques, here's why we do it:",
"1) Psychological - anything that distracts or disrupts the other person's concentration is a benefit to you. It doesn't take much when two people are evenly matched. If you're outclassed, this isn't going to be the thing that puts you over the top.",
"2) Physical - Breathing out when tensing muscles for impact is the best situation. It means all your muscles are contracting at the same time, and your body is in unison on doing so. You don't have your chest expanding from intake, wile you're arm is trying to tense for control and strength. Again, this is going to add a 'smidge' to your technique. But when you're playing at the top of the sport with other people a 'smidge' is sometimes all it takes.",
"Both of these things are applicable to tennis, or any physical competition. We have other reasons we do it, but worrying about getting hit when you attack and other stuff doesn't apply to tennis.",
"As for why didn't they do it before? It was considered a more gentile sport. Think about when Andre Agassi wore denim shorts and how much that upset the tennis elite. There were unofficial rules of decorum that don't become official until someone decides to test the bounds.",
"I personally have no problem with it, but then I don't think sports should be played in silence.",
"Golf... I'm looking at you."
] |
[
"Not sure if this the reason they started grunting, but seems like a good reason to do it.",
"In the current study, 33 undergraduate students watched tennis players hitting balls across the tennis court. Each shot was either quiet or contained a brief \"unnh\" noise that occurred as the player struck the ball.",
"The participants were asked to enter the direction of the shot in each clip on a keyboard, answering as quickly and accurately as possible. As it turned out, the extraneous sound significantly slowed the students' response times. They also made more mistakes in entering the direction of the shots with grunts. ",
"http://www.livescience.com/10772-unnh-grunting-tennis-players-edge.html"
] |
[
"There is a physical advantage to it. The power of a tennis shot is largely generated in the hips, torso and shoulders, to get the most power you have to generate rotation in all 3 sections which requires clenching the abdomen. You can do it gently which is fine, but when you put in maximum force you are going to compress the abdomen which forces the diaphragm up expelling air from the lungs (which is why you should exhale during weight lifting).",
"There is a phychological benefit as well, both in distracting the opponent (very little) and in masking the sound of the shot (this is why tabletennis players used to stomp the floor when they shot the ball)."
] |
[
"If a cop had to fine someone for playing music too loud, wouldn't the sound meter's distance from the source be critical?"
] |
[
false
] | null |
[
"Sound intensity drops with the square of the distance to the source. So yes, in that sense, where the meter is located does matter.",
"However, the specific wording of the legislation determines the procedure for determining if a source is \"too loud.\" For instance, (anecdotally) I got a noise violation ticket in college, and the officer who cited me didn't have a meter at all, because local ordinance left it to the discretion of the officer.",
"So you're right about the distance between the source and the meter, but that doesn't always matter."
] |
[
"SPL (Sound Pressure Level)=20∙log(P/Pref), where P is the pressure due to the sound source and Pref is a reference pressure, typically 20 microPascals, the (approximate) lower threshold of human hearing at 1000 Hz. You would use a SPL meter to measure the sound, you can even use a smartphone nowadays. A difference of 10 dB corresponds to 10 times as much sound energy, which is percieved by us as about twice as loud.",
"Sound from a point source propagates along a spherical wavefront, with a surface area increasing as the radius squared. So the wavefront 20 feet from the source will have 4 times the area of a wavefront 10 feet from the source, but the same amount of total energy, so the energy is more spread out and the sound is quieter. If you plug in the numbers, you find that you lose 6 dB per doubling of distance. If you measured 80 dB at 10 feet, you would measure 74 dB at 20 feet.",
"Noise ordinances",
" here (Omaha, NE) are mostly nonspecific, saying things like ",
"not be audible for a distance in excess of one\nhundred (100) feet from the source",
"rather than \"the sound pressure level measured at a distance of 100 feet shall be below 0 dB (re 20 microPascals)\" or \"shall not exceed the background noise level by more than 3 dB\", so its really just a judgement call. The only restriction in Omaha that I am aware of is for vehicle loudness, which is specified to be measured at 50 feet. Correction factors are given for other distances.",
"Also, it doesn't make a huge difference is the cop is 50 or 100 feet from the source, 6 dB is perceivable but not that big of a difference."
] |
[
"This seems like it's a legal issue more than a science issue. In order for the cops to come because of a noise complaint, someone has to call them and complain. In that case, the cops would probably determine the noise level at the complainer's distance from the sound source. Sure, the sound gets louder as you get closer to the sound source; but since it's not bothering anyone there, the police won't really worry about it."
] |
[
"Is water cycle present in Antarctica?"
] |
[
false
] |
I was wondering, as Antarctica does not often experience temperatures above zero degrees Celsius, if snow just accumulates or if there is a water cycle present on the continent
|
[
"Sure there is a water cycle, it's just a bit different than the other continents. Snowfall is driven by winds carrying moisture in from the oceans. Water molecules can return from the ice to the atmosphere via sublimation, which is like evaporation but is a phase change directly from the solid (ice) to gas (water vapor) phase. The other key term in the water cycle is the loss of water to the ocean via the glaciers that slowly carry the ice into the sea. So a rough budget for the antarctic ice sheet is:",
"(snow fall) - (sublimation) - (glacial flow into sea) = (change in mass of ice over time). "
] |
[
"Yes, the glaciers ",
"flow downhill into the ocean.",
" Although they move rather slowly, typically 1 meter per day, glaciers can be quite thick so there is a significant transport of frozen water toward the coast."
] |
[
"I can understand how sublimation works, but I have another question about glaciers: Does the snow shifts from inland to the coast then? "
] |
[
"How different would the Earth be today if the Permian-Triassic extinction event did not occur?"
] |
[
false
] |
I know this is an oddly specific question, and I couldn't find anything using the search bar. I'm just curious how this would have effected Earth and biodiversity as a whole.
|
[
"It is impossible to answer precisely what current biodiversity and faunal composition would look like in that hypothetical never-never land of \"what ifs\".",
"The most we can say is that natural selection would have continued to operate, but with a greater number of lineages to choose fromthan those who were cut off by the Great Dying. And the relative importance of surviving lineages would (probably) not have been the same either, but life is a lottery and a hypothetical outcome is quasi-impossible to predict.",
"But lets have a look at some of the lineages which might have survived in later times, some to die out, but later (perhaps cut-off by the K-T event?), others perhaps making it to our days:",
"Trilobites;",
"Eurypterids;",
"Orthid and productid brachiopods;",
"Several orders of insects (caloneurodeans, monurans, paleodictyopteroids, protelytropterans, and protodonates);",
"And that's just by focussing on a very coarse taxonomic level, the survival of individual genera and species within lineages has the potential to completely upset future faunal assemblages. Ninety-something (depending on source) of marine species are believed to have croaked in the Great Dying. Had the dice fallen differently, a quasi-infinite number of potentially differently populated worlds could have emerged on the other side.",
"So who can say? "
] |
[
"I think another important thing to note is that the Permo-Triassic extinction paved the way for archosaurs replacing synapsids as the dominant clade of lifeforms - so no P-Tr may mean no dinosaurs, and most likely not humans as we know them today, since many adaptations seen in humans and other modern mammals arose from a life in the shadows of dinosaurs."
] |
[
"And humans would never have evolved, right?"
] |
[
"Sophomore in Electrical Engineering.. looking for projects?"
] |
[
false
] |
Hello all. As I said in the title, I am in college for Electrical Engineering. I'm doing good in all my classes and such, but I'm looking for something extra to do in my time (other than video games); I'd like to possibly build some circuits or do something to further my learning. However, I'm at a dead spot, and can't think of any circuits/projects that would be cool. Can Reddit help me think of some project ideas, to keep my time productive?
|
[
"Maybe consider doing research? I know it's different in biology than engineering since you don't need to do research in engineering to get a job, but I can honestly say that research was the most rewarding part of my college career. Your professors will all have their own research projects; look around to see what interests you.",
"Otherwise, I have known some EECS majors who have done things like build their own guitar amplifiers, or building cheap medical devices that they send to developing countries or somethign."
] |
[
"Look at your department's course catalog and find an upper-level course/elective or two that sound really interesting to you. Find out who teaches those courses. Chances are that their research is related to the elective that they teach, but look into it on the professors' web pages. Send them a quick email introducing yourself and asking if they have time to discuss some possible research opportunities. All professors have projects or odd jobs that they would like to have done but don't have the time to do because of administrative stuff and the demands of research. If you're really lucky, you can get paid to do it. I was an electrical engineering major, now an electrical engineer, and that's the route that I took. The skills that I learned in the lab were a big part of what landed me my first job out of college."
] |
[
"Thank you- I'll look around and ask my professors if they're doing any or know of any cool projects."
] |
[
"Can maglev trains go uphill?"
] |
[
false
] |
Conventional trains are incapable of going up very steep hills because of the low friction between its wheels and the track. So how would a maglev train with zero friction and only gravity and drag to worry about perform going up an incline? Would the linear motor be able to drive the train up a steep hill? And how steep? What's the limiting factor? Heat, power, weight, etc? I'm excited to see what you guys have to say!
|
[
"sure. The magnets both levitate and propel the train. It's just a matter of having enough power to overcome the incline. In this regard the maglev train would perform better than a traditional train because a maglev train does not rely on wheels and friction."
] |
[
"To add to that - magnetic levitation happily works vertically as well, ",
"here",
" is an article about magnetic elevators and ",
"here",
" is their (a bit flashier) advertisement video.",
"I have no real engineering insight into how energy efficient they would really be on a large scale, the article seems really hyped about them but they are the ones designing it after all."
] |
[
"See item #15 on this page:",
"http://northeastmaglev.com/frequently-asked-questions-about-scmaglev",
"The SCMAGLEV is capable of climbing a 4 percent gradient while maintaining its maximum operational speed of 311 mph (500 km/h). The system is capable of climbing steeper inclines, but with constant electromagnetic propulsion forces, its top speed is limited by gravity according to the law of physics. For example, at a 10 percent gradient, the SCMAGLEV may be estimated to be capable of cruising at 200 mph (322 km/h).\n"
] |
[
"How do we know what the earth's mantle, core, etc. are made of?"
] |
[
false
] | null |
[
"/u/DMos150",
" is talking about seismic tomography. Otherwise that's a good summary. I'll just add a bit more detail. There are also other seismic techniques that are used, such as receiver functions, that get at some other details, but the end goal is the same - it tells you something about earths structure.",
"Its important to clarify that seismic can't tell us much about specific compositions by it self. What it can tell us for example, is that the outer core is liquid because shear-waves (a type of seismic wave) do not travel through liquid. The links from DMos150 explain that a bit more. It also images major changes in velocity or density in the earth (see 410 and 660 discontinuities.",
"Specific compositions come from other studies. We know what the mantle is by looking at \"xenoliths\" which are pieces of the mantle that have been brought up to the surface, usually through volcanic eruptions. There may be other direct evidence that I am forgetting at the moment, but its important to note that this direct evidence only comes from the upper ~200 km on the mantle, the other ~2700 km we have no direct evidence from ( that is no physical samples.)",
"For the core, we look at meteorites, make the assumption that earth was made up of similar compositions, since these meteorites date to the time that earth was formed. Again the previous links talk more about this.",
"Beyond that, we can make high-pressure/high-temperature models that give us an idea of how minerals behave at depth. For example, olivine, the primary mineral in the upper mantle, changes to -wadsleyite, a high-pressure version of olivine, at ~410 km. We know olivine changes to wadsleyite, from experiments, and we see evidence for a discontinuity in seismic tomography, so we can estimate the pressure/temp at 410 km and see it sufficient to change olivine to wadsleyite.",
"There is a lot more that I don't remember or just don't now. But I think this should give you a good idea.",
"Source: Phd student in geophysics."
] |
[
"The study of the Earth's interior is done using a technique with the delightful name \"Seismic tomography.\"",
"When an earthquake occurs, the shock waves don't just ripple across the surface, but travel into and through the Earth. We can only detect waves on the surface, but by studying the different speeds and trajectories of waves as they re-surface after traveling through the planet, we can infer what kinds of materials they passed through on their journey.",
"Then we combine that with our knowledge of geochemistry, and comparison with other objects in the solar system, to get a good idea of what materials are sitting deep within our planet. ",
"More detailed and professional explanations ",
"here",
" and ",
"here",
"EDIT: Seismic ",
", not topography. Thanks ",
"/u/articmaze",
" for spotting that. "
] |
[
"I think most methods have been explained, but not all(on mobile, might have missed something, sorry for that)\nBasically, there are direct methods, such as the drillings in Kola Peninsule (Russia) that went 12023 m deep (continent) and the drillings in Costa Rica , 2km deep in the ocean\nOfc 12 km isn't anything compared to the earths size, so we must go deeper!\nXenoliths, as mentioned before, are little bits of rock that travel inside the mantle with the magma, but , since the mantle is mostly formed by a white Rock that has a higher melting temperature than magma, it doesn't melt with it (from Portugal, not native speaker, don't know the name of the Rock in English) and millions and millions of years later, we can analyze the rock \nSince I don't want to post a wall of text, you can study Planetology (what other planets are made off) and Astrogeology, which includes meteorites, comets and such(they were formed at the same time as the earth)\nAlso, trough density(gravimetry) and geomagnetism, which is, at first glance, pretty damn interesting, can explain the basics if anyone wants to\nThen, as before mentioned, you have sismology and Vulcanism\nHope I was of a bit of help"
] |
[
"How does rocket fuel not freeze in space?"
] |
[
false
] |
Just curious, I was watching the film "The Day After Tomorrow" and the helicopter's fuel instantly froze causing it to crash. How does this not happen to rockets in space where the temperature is near absolute zero? Are the ships just incredibly well insulated?
|
[
"In space most things are in a vacuum, which is a very good insulator. Think about vacuum flasks for an example. And close to the Earth there are few places close to absolute zero. For example the lunar surface which was explored during the Apollo program was generally very warm, because it was exposed to the sun. Having said that, rocket fuel on some deep space probes does need to be heated, though the energy cost of doing that is not as large as you probably think.",
"edit: also \"The Day After Tomorrow\" is a terrible film with terrible science in it. Best not to use it as an example around here."
] |
[
"good insulation ",
" solid fuel is already frozen. LOX freezes at 54K, which makes it likely to be used up before it becomes solid. ",
"Most ships burn up their fuel before they just start cruising, which is where they would be before they froze."
] |
[
"Water freezes slower than vodka, since water has a higher specific heat capacity, but vodka freezes at lower temperatures than water, because it has a lover melting point.",
"Be careful to use the specific meaning of words correctly in here, as people are sensitive to inaccuracies.",
"Also, some simple explosive thing like propanonperoxide has a melting point of 91",
" C, where the flammable (but not explosive) exprecursors are all liquid at room-temperature."
] |
[
"mainly an astronomy/optics question: Could we built a Telescope using the Sun as the objective? Is there any other large natural object in our solar system that would help us focus light from thousands of light-years away? Is collective astronomy observation even feasible?"
] |
[
false
] |
The idea is to place an array of photon sensors around the earth and combine the output of these sensor devices to build one unique picture of an object thousands of light-years behind the Sun. Let alone the technological/commercial barriers, is this physically even possible?
|
[
"I'm unclear what exactly you are trying to do. Are you trying to take a picture of something behind the sun?",
"Since our planet orbits the sun, at some point in our orbit we are on the other side and can certainly train our own telescopes at the object.",
"Thousands of light years is very close (where I work has seen galaxies as far as 12.9 billion light years away).",
"Also... we have satellites that are on the other side of the sun from us (however, they are looking at the sun so that we get a 360 degree constant image of the sun to study - look at the NASA STEREO mission).",
"I'm also confused as to why you would look at the sun to see something behind it. The suns light will wash out just about everything. You want to do the opposite - you only want to look at the light of the distant object. We do not use a bright light between us and a distant object to observe.",
"Or did I completely miss your original question?"
] |
[
"Are you talking about using the gravitational lensing of the sun to focus light? If so, then I should point out that gravitational lensing from massive objects doesn't have the same useful properties as a telescope lens. Here's wikipedia: ",
"Unlike an optical lens, maximum 'bending' occurs closest to, and minimum 'bending' furthest from, the center of a gravitational lens. Consequently, a gravitational lens has no single focal point, but a focal line instead. If the (light) source, the massive lensing object, and the observer lie in a straight line, the original light source will appear as a ring around the massive lensing object. If there is any misalignment the observer will see an arc segment instead. ",
"I don't know if that means it's impossible to usefully use the sun to overcome the ",
"diffraction limit",
" (which is the subject of an ",
"ongoing thread",
" here at ",
"/r/AskScience",
"), but it does mean you would have to do some serious correction."
] |
[
"Possibly",
", but not from Earth. Your telescope would need to be at least 550 AU out, and it would be pretty much limited to a single target."
] |
[
"How does your stomach know when to stop digesting food and move it into the small intestine?"
] |
[
false
] | null |
[
"A hole in the stomach means a direct route for bacteria and air to get into the abdominal cavity. So a bowel or stomach perf almost always leads to infection. ",
"But yeah it also leads to incredibly profound pain and tenderness. The acid is very very irritating to the lining of that cavity and the organs inside. Leads to what we call an \"acute abdomen\" and it's pretty unmistakable. It's a surgical emergency. "
] |
[
"It's not -good-, but it's not like movies portray acid. ",
"",
"Think about vomiting and acid reflux. If you puke, particularly on an empty stomach, you got a mouth full of stomach acid. It's not that bad, as far as causing damage to your body goes. However, repeated, long-term exposure to stomach acid, as in acid reflux, can wear away at the esophagus leading to various problems."
] |
[
"Really the fact that you’re about to get super infected is more of a concern than stomach acid is. "
] |
[
"How stable is a person's personality over time?"
] |
[
false
] | null |
[
"Personality is highly, but not perfectly stable (either rank-order or mean-level change). However, change may well be a heritable individual difference. ",
"Roberts & Delvecchio (psych bulletin, 2000) did a study on this and found that the test-retest correlations between the \"Big Five\" personality traits (agreeableness, emotional stability, conscientiousness, extraversion, and openness) were quite high over the lifespan, and actually, that the correlations increase over time. For instance, the average correlations for teenage years when tested at 13 and 19 was .49, while the correlation at 30-39 was .62 and at 50-59 years old was .75.",
"Other research (Roberts, Walton & Viechtbauer, 2006) suggests that emotional stability tends to slightly increase over the lifespan, as does conscientiousness and agreeableness, while extraversion pretty much remains constant. ",
"Ultimately, yes, personality is quite stable over the lifespan, but small changes do occur for some individuals. "
] |
[
"The answer depends on how personality is measured, how long a period of time is elapsing, the age period covered. The most common instrument is some version of the NEO Big Five, which assesses neuroticism, extraversion, openness, agreeableness, and conscientiousness. From adolescence to early adulthood, the rank order stability (i.e., ranking people from high to low on a personality attribute and then seeing how this ranking changes) is about .5. There are two ways to think about this -- 1. that number is low, because personality is a trait (i.e., it should be fairly enduring). 2. the number is high, because not may behaviors are that stable. As people get older, this rank stability increases (I believe). ",
"A different form of stability is mean level -- does the mean of agreeableness change over time, for example. Mean levels change quite a bit (basically, people mature) into the 30s and then stabilize somewhat. ",
"I hope this helps -- the answer is actually more complicated (there are other forms of stability, statistical issues etc.)."
] |
[
"This comment has been overwritten by an open source script to protect this user's privacy. ",
"If you would like to do the same, add the browser extension ",
"GreaseMonkey",
" to Firefox and add ",
"this open source script",
". ",
"Then simply click on your username on Reddit, go to the comments tab, and hit the new OVERWRITE button at the top."
] |
[
"Is it true that you are unable to learn second language as proficiently as a native speaker when you are in your mid twenties?"
] |
[
false
] |
I have seen this , and now Im wondering if I'll be ever able to learn another language the way I would like to which is as proficiently as a native speaker.
|
[
"This depends entirely on what you mean by native. Can you get really good? Absolutely! Can you discuss everything under the sun? Sure!",
"Can you pick up the phonemic contrasts that this language has that yours lacks? Possibly. Probably not to native performance levels.",
"Are there other tests that can be used to discriminate between native and non-native speakers? Sure!",
"In usage, does it matter? Not all that much - but note that many many people who are highly motivated to acquire a second language (e.g., people who move to a new country, etc) try to do so but fail to pick up the hard bits of the sound patterns (i.e., they retain an accent) or the hard bits of the syntax (e.g., they don't always say things in a way that feels right to a native, they use strange constructions, they overapply patterns like past tense marking, etc)."
] |
[
"It is very clear from a wide number of experimental investigations that there is a very big difference between people learning a language as a child and learning a language as an adult. Some of these are things caused by developmental differences, as predicted by the ",
"Critical Period Hypothesis",
", but others are caused by factors like the different expectations people place on young children as opposed to adults in what sort of language abilities they are going to have (Lightbown and Spada 2006: 68).",
"Patkowski (1980)",
" looked at the differences in second language learners of English depending on when they started learning, either before or after puberty. The speakers were rated on a scale of 0 to 5, where 0 represented having no knowledge in the language, and 5 represented being an educated native speaker. Pre-puberty learners almost uniformly scored 4s and 5s, while post-puberty learners were mostly at the 3+ level, but with significant variation; some people did well, others did poorly--exactly what we would see in any other sort of generalized learning task.",
"Other experiments, like ",
"Johnson and Newport (1989)",
" looked at the intuitions second language learners of English had regarding whether or not a sentence was grammatical. Exactly as in Patkowski (1980)'s study, they found a similar clustering of more or less native-like proficiency in pre-puberty learners, and a range of proficiencies in post-puberty learners.",
"So is it impossible to learn a second language as an adult? Certainly not. It seems to be more difficult, for a variety of factors, to get to native-like proficiency, but not impossible. And in addition, there is some evidence that because adults are learning a second language in a very different way than young children, they can do some things much faster. ",
"Snow and Hoefnagel-Höhle (1978)",
" tested children, adolescents, and adults in the first few months of learning Dutch. Adolescents scored the best on early tests, but adults, and not children, did second best. Eventually the children overtook the adults, and adolescents remained on top, but the adults are able to use other, transferable skills in order to aid their second language acquisition."
] |
[
"This is laughably, demonstrably false. Let me give you a simple example: new words. Can adults beyond the age of 35 gain vocabulary? You bet!",
"There's also a bunch of evidence about neuroplasticity into adulthood being more of a thing than really old stuff claims - see the below references for a slew of evidence.",
"Bach-y-Rita, P., & Kercel, S. W. (2003). Sensory substitution and the human–machine interface. ",
", 7(12), 541-546.",
"Draganski, B., & May, A. (2008). Training-induced structural changes in the adult human brain. ",
", 192(1), 137-142.",
"Green, C. S., & Bavelier, D. (2008). Exercising your brain: a review of human brain plasticity and training-induced learning. ",
", 23(4), 692.",
"Hofman, M. A., Purba, J. S., & Swaab, D. F. (1993). Annual variations in the vasopressin neuron population of the human suprachiasmatic nucleus. ",
", 53(4), 1103-1112.",
"Rakic, P. (2002). Neurogenesis in adult primate neocortex: an evaluation of the evidence. ",
", 3(1), 65-71."
] |
[
"Does a 1000W PC output about the same amount of heat as a 1000W heater?"
] |
[
false
] |
Assuming the PC is pulling 1000W from the wall, does it produce the same amount of heat output as a 1000W heater? if no, then where else does the energy go because the PC is not moving?
|
[
"If there actually is 1000W of electrical current going through the PC from the wall socket, then yes, it's generating just as much heat as a 1000W heater doing the same thing.",
"However, just because a PC has a 1000W PSU doesn't mean that it actually draws 1000W on average. Or ever, for that matter. How much power it actually draws will depend on what other components it has and what it's doing. The PSU's wattage rating is the ",
" power level that the PSU is designed to safely handle."
] |
[
"If it's a monitor that gets its power from the PC, such as a laptop screen, yeah. My impression is that most standalone monitors have a separate power cord, their connection to the PC being for data only. And a machine with a 1000W PSU is unlikely to be a laptop.",
"Also, inside a closed room without many transparent windows, almost all the light output from the monitor is going to turn into heat before leaving the room anyway."
] |
[
"Short answer. Every measurable watt the computer takes from the wall will be converted to heat.",
"Longer answer. No, sub fractional amounts of energy will be put into objects that increase their potential energy. Some energy that is taken from the wall going into processes that do not have a 100% conversion to thermal energy. Things such as a hard drive, and a CD burner. However this amount of energy is far far less than 1% of the energy that is drawn by the CD/Hard Drive. Some other processes like fans may spend energy degrading their components. "
] |
[
"Would filling the tires of different racing vehicles (cars, bikes, etc.) with a lighter-than-air gas like helium give the racer any kind of significant advantage?"
] |
[
false
] | null |
[
"That's exactly why. Nitrogen is inert & won't fluctuate (as much) throughout the variable daily temperatures. So instead of 28psi on a cold morning moving to 32psi in the warm afternoon, the pressure just stays where it was initially filled by nitrogen. This helps with tire longevity, as running your tires even a few PSI below or above what Is called for can reduce their lifetime. Edit: nitrogen still contracts/expands with temperature changes, just much less. "
] |
[
"That's exactly why. Nitrogen is inert & won't fluctuate (as much) throughout the variable daily temperatures. So instead of 28psi on a cold morning moving to 32psi in the warm afternoon, the pressure just stays where it was initially filled by nitrogen. This helps with tire longevity, as running your tires even a few PSI below or above what Is called for can reduce their lifetime. Edit: nitrogen still contracts/expands with temperature changes, just much less. "
] |
[
"The extra weight you would have to add for thermal control would make the whole exercise a waste of time."
] |
[
"Why do only a few concentrated acids dissolve glass?"
] |
[
false
] |
I'm assuming it doesn't have anything to do with the pH of the acids, since triflic acid is stable in glass while hydrofluoric acid eats through it. What, chemically, allows some acids to react with the oxides in glass?
|
[
"Common glass consists primarily of silica (SiO2). In order to dissolve glass you must break the Si-O bonds in silica. These bonds are very strong, so you must form even stronger bonds for dissolution to occur. Si-F bonds are also quite strong. When HF reacts with silica it will form H2SiF6 or SiF4. Both are water soluble which means that a fresh surface of SiO2 will be exposed to attack by HF."
] |
[
"HF isn't such a strong acid, if I recall correctly. The F atom radius is too small. It's weaker than e.g. HCl. there are quite some acids stronger than this.",
"HF isn't classified as a \"strong\" acid, but it is highly corrosive. Strong vs Weak acids refers to how well they deprotinate in solution. Strong acids like HCl will dissociate fully into H+ and Cl- in solution. Weak acids like HF will dissociate into H+ and F-, but also have significant concentrations of nondissociated HF in solution."
] |
[
"You're going to confuse a lot of amateur chemists with this \"strong acid\" claim. Most people don't know know the difference between pKa and pH and will think back to their highschool chemistry definition of \"strong acids dissociate completely in water\".",
"But you're right, it's not a terribly strong acid with a pKa of only 3.2. HCl on the other hand has a pKa of -7. Triflic Acid, which the OP mentioned has a pKa around -14!"
] |
[
"What would a nuclear explosion in space look like?"
] |
[
false
] |
We see hollywood special effects setting off explosions and nukes going off in shows like Battlestar Galactica but what would an nuclear explosion reasonably removed from a planet's gravity well look like?
|
[
"Searched",
"Relevant ",
"discussion",
"Original question by ",
"shishkebob202",
"Just read an article that mentioned the banning of nuclear tests in space and it got me thinking. If a nuclear weapon was detonated in some remote part of space or in a vacuum, would it have the same effect? Might vary according to the type of bomb I suppose, but I couldn't find much on google.",
"Top comment courtesy ",
"rozyn",
"Starfish Prime was the 2nd high atmospheric/space test. The distance it was detonated is close to that of the higher operating distance of the International space station. At that distance(250 miles), there is the vacuum of space. It was also the last test at that height, as Starfish prime scared the crap out of the soviet union AND the US enough for them to issue a ban on it. Not to mention it messed up our ability to measure the Van Allen Radiation belt in space with the artificial radiation it added for about 10 years after(that's how long the radiation took to dissipate from Starfish prime)",
"A video of Starfish Prime",
". You can see that the way they explode looks much different then that of a conventional nuclear explosion. Also it alerted us to the long reaching effects of EMP waves, that effectively killed sattelites in the viscinity, as well as shutting down Telephone communications, and knocking out streetlights on some of the hawaiian islands.",
"You can read more about it here on the Wiki",
"Further edit: ",
"Another wiki page For \"High Altitude Nuclear testing\"",
" explaining the differences in Detonation Height vs the EMP effect radius, including comparative pictures of range. Includes information about the russian Space test and the after effects of the emp wave caused.",
"Relevant ",
"follow-up",
" courtesy ",
"benjimusprime",
"I think that what we are getting at is the intuitive expectation of a nuke explosion. This discussion seems similar to the early expectation that rockets could not fly in space because they would not have an atmosphere to \"push\" off of. For example, from ",
"http://www.straightdope.com/columns/read/1846/how-do-rockets-work-in-the-vacuum-of-space",
" \"That Professor Goddard with his 'chair' in Clark College and the countenancing of the Smithsonian Institution does not know the relation of action to reaction, and of the need to have something better than a vacuum against which to react--to say that would be absurd. Of course, he only seems to lack the knowledge ladled out daily in high schools.\"",
"This discussion of need for kinetic \"shrapnel\" or a material to act against is not conceiving of the forces correctly. The energy and subsequent forces of the nuke exist unto themselves, and do not require combustion of air to \"explode.\" But they do interact in more complicated ways, like the EMP (awesome thread btw), and radiative heating, pressure waves, all sorts of interesting things. Also, it is completely forgivable that we do not have an \"intuitive\" expectation for things that happen in a vacuum because we do not ever inhabit a vacuum in our daily lives."
] |
[
"Excellent bot. For anyone reading this, I have to add that starfish prime invariably comes up in discussions of space nukes, and it always irritates me because even though it was detonated in a vacuum, it wasn't technically outside the atmosphere - it was well within the ionosphere and thus could interact with the Earth's magnetic field to produce an EMP. A nuke detonated away from Earth would not produce an EMP.",
"Even putting that issue aside, 400 km above Earth is not representative of a space nuclear explosion. Starfish prime was still at an altitude where a large fraction of the radiation would have been absorbed by the various layers of the atmosphere, having the effect of creating a shockwave and 'fireball'-like fireworks display. Again, a nuclear explosion far away from the atmosphere would create neither any discernible shockwave nor any fireball that could be seen with the naked eye."
] |
[
"Yes, this is correct. Starfish Prime is interesting but not a case study for what a nuclear detonation would look like in 'real' outer space.",
"From everything I've read, a nuclear detonation in the vacuum of space would look more or less like a flashbulb going off - a brilliant flash of light, and not much else. It's actually not ",
" great as a space weapon unless you detonate it very close to the target so radiation and thermal shock can do damage to the ship you're targeting. ProjectRHO is a fantastic site with lots of great information about this sort of thing: ",
"http://www.projectrho.com/public_html/rocket/spacegunconvent.php#nuke"
] |
[
"Why is there static on my radio whenever my cellphone is near?"
] |
[
false
] | null |
[
"Mobile phones communicate using radio waves. Analogue radio antenna, speaker cables, and other wires can act as antenna and pick up the radio waves transmitted by the phone, which produces an electrical signal, which you hear as noise on the attached speakers. The noise and bursts you hear is how the phone encodes and transmits data. With practice you can tell, say, an incoming phonecall from an incoming text message by listening to the interference before the phone actually goes off."
] |
[
"Is ",
"this",
" the noise you're talking about? It's the \"GSM noise.\" I'm not an expert in physics, broadcasting, or antennae so I'm going to stop talking here."
] |
[
"That is exactly it."
] |
[
"What causes the shape of ferrofluids introduced to a magnetic field?"
] |
[
false
] | null |
[
"Generally, the ferrofluid follows the pattern of the magnetic field itself, concentrating in areas of high field. The \"spike\" pattern is the result of ",
"normal-field instability",
", which occurs because the particles are more easily magnetized in air than \"inside,\" surrounded by other particles. Basically, the fluid is ",
" its surface area, rather than minimizing it (as most fluids we're familiar with do)--that's the energetically-favorable state. The Wikipedia page that you cited has a few good sources; I'm afraid I can't offer many good ones beyond what is available there."
] |
[
"I wrote the ",
"Ferrofluid#Normal-field instability",
" section. :) I tried to make it as vivid as possible. Does it need... more explanation? Simpler language?",
"Ninja edit: Maybe it needs a diagram?"
] |
[
"OH wow really? Yes a diagram would be phenomenal. Possibly an explanation that relates the simple laws of magnetic fields and relates them directly to the corrugations? Anyway, thanks for contributing to the world! Ahaha"
] |
[
"Are there any planets in the universe that are as big--or possibly bigger--than our sun?"
] |
[
false
] |
Furthermore, would they even be habitable due to the incredible force of gravity?
|
[
"No if they were the size of our sun they would be considered stars because they would presumably be fusing hydrogen in their core. If they weren't fusing hydrogen, they'd be considered a brown dwarf."
] |
[
"What do you mean by 'big', do you mean mass or radius? Anyway, the answer to both is no. If a were more massive than the sun, it would be a star. If had a mass comparable to the Earth or even Jupiter, but a radius larger than the sun, then the planet would not be stable and would collapse to something the size of a planet."
] |
[
"Wouldn't it be stable if the internal temperature were high enough? I'm thinking of a very low density gas giant held up by high temperatures. It wouldn't strictly be \"stable\" because it would gradually shrink as it radiated away heat, but the same is true of Jupiter."
] |
[
"How does a single propeller plane not roll?"
] |
[
false
] |
So, suppose an airplane with a single propeller spinning in a clockwise direction. So, by the conservation of angular momentum, the body of the plane must spin in anticlockwise direction. How do plane resist that and fly straight.
|
[
"The ailerons compensate for the propeller and engine torque with aerodynamic forces."
] |
[
"Yes. This is most notably seen on large single engine WW2 warbirds with their very powerful piston engines. They have very high engine torque that is tricky to compensate for as you throttle up or down."
] |
[
"It has to be noted, though, that the air resistance of the wings intrinsically counters the roll tendency to an extent. Even untrimmed, a usual GA plane won't go into a wild roll due to engine torque. There's also additional effects, like asymmetries in prop wash and asymmetric blade effects at higher angle of attack."
] |
[
"Does every cloud represent an area of lower air pressure than the air that surrounds it?"
] |
[
false
] |
I did some googling but couldn't find an answer to this specific question - if I see a cloud can I assume that that location in the atmosphere has a measurably lower pressure than the air surrounding it?
|
[
"Not necessarily pressure, but temperature. Clouds form when the ambient air temperature reaches the dew point, this is the temperature at which water condenses at to form a cloud. Low pressure systems tend to bring clouds with them but are not the direct cause."
] |
[
"I think you’re under the impression that density and pressure are related and on a very very small scale that may be true but in terms of the entire atmosphere, the pressure difference in a cloud vs the atmosphere is miniscule at best. Clouds will only form once the dew point is reached, pressure doesn’t play a big factor in that since pressure always decreases with height while temperature does not. It’s also possible for temperatures to be very cold without ever forming clouds due to a lack of moisture in the air. It is true that warmer air is less dense than cold air which gives it bouyancy and the ability to rise upwards, but cloud formation after that is reliant purely on temperature and moisture."
] |
[
"I guess I got focused on pressure since \"clouds\" that are man made (such as wingtip vortices, or the shock cones around trans / supersonic aircraft) are formed by the pressure differential... at least I think so, but now you've got me wondering if it's another misunderstanding lol. Thank you for responding, I appreciate it!"
] |
[
"Which would burn more calories by: running a mile, walking a mile, or are they the same?"
] |
[
false
] |
I think this may boil down to a biomechanics problem and is probably affected by running and walking form. If that's the case, you can assume the most energy-efficient walking and running form.
|
[
"Complicated question. The efficiency of muscles depend very much on the posture and the kind of movement and is not the same for running and walking. Although newer studies would be much more reliable, here is a 1976 paper talking about the exact thing. ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1283673/",
"The abstract is a good summary. Pasting it here for a quick go-through. ",
"The mechanical power spent to accelerate the limbs relative to the trunk in level walking and running, Ẇint, has been measured at various `constant' speeds (3-33 km/hr) with the cinematographic procedure used by Fenn (1930a) at high speeds of running.",
"The Ẇint increases approximately as the square of the speed of walking and running. For a given speed Ẇint is greater in walking than in running.",
"In walking above 3 km/hr, Ẇint is greater than the power spent to accelerate and lift the centre of mass of the body at each step, Ẇext(measured by Cavagna, Thys & Zamboni, 1976b). In running Ẇint < Ẇextup to about 20 km/hr, whereas at higher speeds Ẇint > Ẇext.",
"The total work done by the muscles was calculated as Wtot = ǀWintǀ + ǀWextǀ. Except that at the highest speeds of walking, the total work done per unit distance Wtot/km is greater in running than in walking.",
"The efficiency of positive work was measured from the ratio Wtot/Net energy expenditure: this is greater than 0·25 indicating that both in walking and in running the muscles utilize, during shortening, some energy stored during a previous phase of negative work (stretching).",
"In walking the efficiency reaches a maximum (0·35-0·40) at intermediate speeds, as may be expected from the properties of the contractile component of muscle. In running the efficiency increases steadily with speed (from 0·45 to 0·70-0·80) suggesting that positive work derives mainly from the passive recoil of muscle elastic elements and to a lesser extent from the active shortening of the contractile machinery. These findings are consistent with the different mechanics of the two exercises."
] |
[
"OTOH, when running you take longer strides, reducing the amount of 'accelerations'. "
] |
[
"Every step you take accelerates your leg and foot from zero (resting on the ground) to twice your velocity in order to get the foot in front of you, then decelerates the foot to rest it on the ground. If F=ma then the faster you go, the more force needed since the acceleration needed is greater by a factor of two. If more force requires more calories, then running should consume more calories than walking."
] |
[
"What is the etymology of the first four prefixes in organic chemistry?"
] |
[
false
] |
Meth-, Eth-, Prop-, But-, Pent-, Hex-...etc. Why dont the first four follow the numeral prefixes and where did they come from?
|
[
"The first alkanes, or rather, alkyl components, were named after where they were first isolated from. This is before we knew things like how many carbon atoms were in them, so a numbering scheme wouldn't have been possible.",
"\"Methyl\" comes from (EDIT: archaic \"methylene\", which is methanol) - which comes from (mistranslated) greek that roughly means alcohol from wood, because methanol was first isolated from fermented wood.",
"\"Ethyl\" comes from \"",
"ether",
"\" - which in the common chemistry parlance of the 1800s meant a liquid that evaporated readily at room temperature.",
"\"Propyl\" comes from \"",
"propionic acid",
"\" - the most basic, or first (protos) fatty (pion) acid discovered.",
"\"Butyl\" comes from \"",
"butyric acid",
"\" - which was first isolated from butter.",
"The longer carbon chains weren't named until the late 19th century, when better analytic techniques allowed characterization of how many carbon atoms were in each molecule, allowing for a more sensible naming scheme."
] |
[
"Methyl predates methanol (1840 vs. 1892), so the reverse is actually true. Methyl in turn comes from methylene (1835), which is where the wood connection comes in, with ",
" meaning wine and ",
" meaning wood being combined with the suffix ",
". "
] |
[
"This is etymologically true, but \"methylene\" isn't a separate chemical, it's a (modern) chemical group. The archaic use of \"methylene\" just refers to methanol, as the etymology implies."
] |
[
"Why are the majority of human beings right-handed? Why aren't we all just ambidextrous?"
] |
[
false
] |
I recently read that ~90% of humans are right-handed and that a similar ratio of right-handedness has been observed in apes. But why? Is/was there some evolutionary benefit or is it just a cultural practice? Why aren't we all 100% ambidextrous?
|
[
"Most theories have the start of the influence way too late in evolution to matter, ie ones that are a result of writing, or things based on teaching styles.",
"My favorite theory that seems to come early enough though is the Throwing Madonna theory, discussed ",
"here",
". It basically says that early in human evolution, female hunter gatherers would be more successful if they carried their infants in their left hands where the baby's proximity to the sound of the mother's beating heart would keep it calmer and quieter leading to more success in hunts. At this time our brains were developing rapidly due to inclusion of protein in our diets, so things leading to successful hunting (and just general survival from predators) would propagate (relatively) quickly.",
"An interesting follow-up question is why left handedness didn't evolve out entirely. "
] |
[
"Have they isolated a gene for left-handedness? If not then it may not have a genetic component which is why it hasn't disappeared."
] |
[
"I've never heard that theory before, so thanks! Seems like it could answer the question. ",
"As far as I'm aware, there's no specific gene for left-handedness but rather a combination of genes. For example, artists and creative personalities tend to have a higher ratio of left-handedness than the general population. Either way, whether it's a singular gene or combo of them that they're evidentially recessive."
] |
[
"When you get a limb amputated, specifically what happens to the veins and circulation?"
] |
[
false
] |
[deleted]
|
[
"Med student here",
"Let's take for example an amputated leg.\nThe lower leg is cut off, bleeds a lot, veins and arteries constrict to help stop the bleeding, blood starts to clot, the wound starts to heal and not very much actually changes (except you lost part of a limb, sorry).",
"You should know that the blood doesn't all go down to the foot and then all the way back up, surely a part takes that route, but a larger part doesn't reach the foot because along the way portions of the blood are used to supply the muscles, skin, other tissues of the leg and then goes to veins that for around 80% dive through muscles and tissue (through what's called in Latin \"venae perforantes\", perforating veins) to deep veins in the leg and then goes up to the rest of the circulation (femoral vein > external iliacal vein > communal iliacal vein > inferior vena cava > heart ...).",
"As you see, not much has to change. The majority of the blood going to your leg can take already existing routes.",
"What probably will change however, is how much blood flows to your leg. Less oxygenated blood is necessary, so through complex pathways for which you'd have to consult a specialist, the arteries feel less need to be as dilated as usual, and they'll shrink a bit.",
"That's in a nutshell what would happen for as far as I can tell after anatomy and venerology courses."
] |
[
"Basically they scar down. I've done a TMA before and basically we go in and then just cauterize the bleeding vessels until there's no more blood. If they're infected, then we do a delayed closure and just leave a flap."
] |
[
"Very helpful, thank you."
] |
[
"Is carrying a 100kg object on Mars harder than carrying a ~38kg object on earth?"
] |
[
false
] |
Since inertia is always based on mass - yet the 'weight' of an object is based on gravity - would it be more difficult to carry an object weighing 100kg on mars vs 38kg on earth - assuming both have the same physical dimensions of course. My initial thought is that although I can more easily lift the object, walking with it means fighting inertia - and fighting ~3x the inertia isn't going to be easy. or an alternate way of putting it: If I weighed 70kg could I really wear a 190kg space suit and walk completely normally expending the same amount of energy as on earth? Somewhat related question: Can I really jump off a 20ft high cliff on mars without too severe of a landing (assuming I can jump off about an 8ft drop on earth easily)? Obviously the nearly non-existent atmosphere of mars would have me accelerate a little faster, but I can't see it mattering that much on such a short drop.
|
[
"The term 'carry' is a bit ill defined from a physics perspective as it would depend very much on the path taken. If we compare two situations where we were pushing a 100kg rock on a skateboard on both Earth and Mars, one would have to do the same work against inertia in both cases.",
"So the works against inertia would be higher in my example, if you were pushing a 100 kg rock on a skateboard on Mars compares to a 38 kg rock on a skateboard on Earth. ",
"The work done against gravity would be the same in both cases.",
"So overall, more work would be done on Mars than on earth (assuming the same space suit worn in both cases) in carrying the rock."
] |
[
"Inertia only affects acceleration. On mars it would be slightly harder to start moving with the 100kg object. Once you are walking the objects inertia is irrelevant. Well it matters again when you stop. As for the difficulty of inertia when starting it's hard to say, given I've never tried. You walk at about 5km/h or 1.4m/s. Lets say it takes you half a second to get to that speed so that's an acceleration of 2.8m/s/s. With that the 38kg object on earth feels like a 11kg object pushing on you. Now the 100kg on mars will fell like a 29kg object pushing you, on earth. Note in using the mass kinda like a force so reference it to a Xkg object sitting on your chest. ",
"Edit: as for your falling question, i believe the drop on earth would be worse, assuming your heights actually work out to the same impact speed. Lets assume the ground of earth and mars is the same. This means that as long as your hitting it at the same speed you will stop in the same amount of time causing the same force. I really can't give you a quick number on a very short impulse like this so in picking the arbitrary number 30m/s/s or 3Gs. The impact on mars and earth will cause 3Gs if you hit at the same speed caused by whatever respective heights. Now on top of the 3Gs there is also your weight that's still on your legs. This means on earth your legs have to support 4Gs, but on mars its more like 3.3Gs. "
] |
[
"'Carry' meaning holding the entire object yourself without the use of wheels.\nFor an somewhat real-world example - grab 2 of those 18L water-cooler jugs (that's about 36kg) and walk 20 meters with them - it's very tiring, and walking like that requires very deliberate steps which seems to fight inertia a lot. Now grab 2 water cooler jug shaped chunks of aluminium on mars - they'll be nearly 100kg. Every time your foot falls it's going to have 3x the inertia behind it, but at 1/3rd the gravity would it matter?"
] |
[
"How do spiders spin up a really long horizontal web between two bushes?"
] |
[
false
] |
Whenever I’ve hiked along a trail and torn apart a spiders web, I’ve always wondered that to myself. Often times it’s just a single strand. How does a spider manage to cross two bushes with a web, seemingly building a bridge between them?
|
[
"Generally they let out a very light pilot strand that is allowed to blow in the wind. The spider can tell from vibrations in the strand if it has stuck itself to something far away. It then pulls on the strand to tighten it, and uses it as a catwalk to initiate construction of the remainder of the web.",
"See for instance this video: ",
"https://www.youtube.com/watch?v=JzdcCkvc_dY"
] |
[
"Oh don't worry, that's not what I'm talking about. The spider stands still, and just lets the silk strand wave in the wind. The spider doesn't move until the silk catches on something else.",
"Ok, now worry: spiders can totally fly. It's called \"ballooning\". Just search youtube for that and have fun."
] |
[
"Oh don't worry, that's not what I'm talking about. The spider stands still, and just lets the silk strand wave in the wind. The spider doesn't move until the silk catches on something else.",
"Ok, now worry: spiders can totally fly. It's called \"ballooning\". Just search youtube for that and have fun."
] |
[
"Is everything provable?"
] |
[
false
] | null |
[
"Consider this. Take your conjecture, and treat it as an axiom. The system may be trivial, and may not work, but your conjecture will certainly be provable.",
"The word proof is meaningless without an axiom system. The incompleteness theorem says that no sufficiently powerful axiom system can be complete. There are simple axiom systems in which everything true can be proved."
] |
[
"Yes you can, in fact people do all the time. Mathematics is not driven by experiments, but by arriving at conclusions from assumed axioms."
] |
[
"Yes you can, in fact people do all the time. Mathematics is not driven by experiments, but by arriving at conclusions from assumed axioms."
] |
[
"If Mercury's orbit was tidally locked, how cold would the dark side be?"
] |
[
false
] | null |
[
"There are permanently shadowed crater floors on Mercury at below 102K (-276 degrees farenheit)"
] |
[
"This is goddamned fascinating. Ok, so stupid question, how is this possible? I know there's no atmosphere, but how is it possible that the extreme heat doesn't effect the rest of the planet? I don't know shit about space."
] |
[
"I thought that Mercury had a very, very thin atmosphere. "
] |
[
"How long is the time delay with a live digital tv transmission?"
] |
[
false
] |
I have a cable Tivo box and when I change from a regular digital channel (say ESPN) to ESPN HD, I notice that the HD Channel is a few seconds behind. So my question is: how much behind, under normal circumstances, is the digital live tv broadcast? I am assuming that it involves a compression and decompression time, regardless if it is HD or not. Am I also right to assume that the old analog live broadcasts were not behind (ignoring speed of light issues)?
|
[
"As little as 1 second for ATSC broadcasts, but live programs sometimes add a few seconds of delay to avoid \"bloopers\". Cable and internet services add several more seconds. You're correct that in the analog days it was almost instantaneous. "
] |
[
"You're correct that in the analog days it was almost instantaneous. ",
"Or about 0.25 seconds for a satellite relay. To as low as 0.016 seconds for a coast to coast microwave link."
] |
[
"It can vary a lot. The regular channel is also \"behind,\" you just don't have anything else to compare it to. Every bit of equipment in the broadcast can add a delay - the machine that adds the captions, the one that mixes between cameras, and so on. Most of the delay comes from encoding for broadcast and decoding in your TV - both of these need to analyse multiple frames. Your TV itself might also add a few frames' delay for enhancements like noise reduction and motion smoothing.",
"Then you can more delays with live interviews, because the same encoding/decoding thing has to happen between the reporter and the studio, so you get those awkward pauses in conversation between the two locations.",
"Analogue broadcast chains could also add delays - and in fact sometimes the studio part of the chain might be digital, or might switch back and forth between analogue and digital, before it got to the analogue transmitter. Once it left the transmitter though, and assuming you were using an old-fashioned TV that didn't do any fancy processing, there was pretty much only the speed of light in play.",
"Sometimes you can see monitors displaying broadcast TV in the background of news channels and the like, and there's usually only a few seconds' delay.",
"One interesting additional source of delay comes with regional variations - here in the UK there are many different variations of BBC1 (SD) which show local news in different parts of the country, but otherwise show the same stuff. To avoid spikes in bandwidth caused by showing the same hard-to-compress pictures at the same time on each one, they all have their own delay, but again only of a few seconds."
] |
[
"Anyone that works in Ecology. Is an Ecology/Bio/something similar major required to get a job in the field?"
] |
[
false
] |
I'm a 3rd year physics + math major and my main plan was to teach, but I'm starting to get really interested in ecology. Is there a possibility of getting a job in ecology without a degree in it? I'm thinking of trying to talk to my bio professor who I chat with a lot to see if I could get into some research here as an undergrad. Sorry if this is the wrong subreddit. I tried but wasn't seeing much there.
|
[
"A job, not so much. Even if you were a ecology major, and undergraduate degree doesn't mean too much. You have to go to grad school to get a real job working in biology.",
"That being said, you should definitely take a few classes if you're interested but more importantly TRY TO FIND UNDERGRAD RESEARCH. It's the best way to get meaningful experience at this stage, and will help you in getting into grad school/job.",
"But don't let your undergraduate major limit you (especially since you're in math/physics). My PI has both her B.A. and Ph.D. in physics, but now she's a professor of neurobiology. If you want to do ecology, pursue it."
] |
[
"This isn't necessarily true, it depends on the kind of ecology work you do. Environmental management and protection and a lot of other \"practical\" areas have jobs for people with a B.A.",
"I would also recommend graduate school depending on what kind of ecology you are in to. I think there are a lot of things like biometrics and more computational sort of ecology programs that are actually becoming fairly popular and require a strong math background."
] |
[
"If you live in Canada, it really helps to speak French because a lot of the jobs are with the federal government."
] |
[
"If the ISS didn't move but just hovered at its present altitude, would it still be zero gravity there?"
] |
[
false
] | null |
[
"Short answer: gravity on the ISS is functionally equal to that on the surface of Earth. The ISS experiences zero g because it's constantly in free fall. \nIn Newtonian physics f =(G* m1* m2) / r",
"\nOnly the r changes is the scenario you suggest. The radius of Earth is ~6300 km, the ISS orbits at 400 km above the Earth. So 6300 squared vs 6700 squared has a bit of an impact but not a large amount. Instead of an acceleration of 9.81 m/s",
" it's 8.67 m/s"
] |
[
"There is no such thing as \"not moving\" in space (or in physics for that matter) if the ISS wasn't moving perpendicularly to gravity's pull it would be falling towards Earth. ",
"Maybe you meant what is it was geostationary (aka always above the same point of Earth) ? Then yes, astronauts would still experience zero g, because it would technically still be moving. "
] |
[
"There is no such thing as \"not moving\" in space (or in physics for that matter) if the ISS wasn't moving perpendicularly to gravity's pull it would be falling towards Earth.",
"I take the question to mean if it were held in place at the same altitude, but stationary relative to the ground below it. This could be done either with rockets (though none we currently have could keep it there for very long) or by attaching it to a space elevator (which we also do not yet have the technology to build).",
"In that case, gravity would be only a little less than on Earth's surface, about 0.9 g."
] |
[
"If you go off a huge jump riding something much heavier than yourself, like a ride-on lawnmower, or a bicycle made of cast iron, do you travel higher/farther than the thing you're riding on if you let go of it mid-flight?"
] |
[
false
] |
Does that object essentially serve as a catapult? I'm just trying to picture the two trajectories - of the person and of the object. Thanks!
|
[
"If there weren't any air, it would make no difference. However, the air resistance probably affects you more than it affects your cast iron bike. You'll travel less far if you let go."
] |
[
"Id like to add that as long as no additional energy is added to the system, its center of mass will land in the same spot as if it were still joined, even if it is in parts. So if you pushed the cart backwards, you would in turn go forwards to ensure that your center of mass stays the same trajectory."
] |
[
"That's incredible. I have a strong math/science background, but physics has always seemed so arbitrary to me, in the sense that there are many explanations that I could believe for how objects are supposed to act, so many explanations that just seem plausible. So it's cool when the correct explanation ends up being cooler that you expect it to be."
] |
[
"Why do shockwaves form at the leading and trailing edge of objects moving at supersonic speeds?"
] |
[
false
] |
I've just started to study shockwaves this year at university and we've been shown images of double-wedge aerofoils with leading edge and trailing edge shocks. I understand why shocks form but what I don't understand is why you have them at both edges. Is it just the flow coming off the upper and lower surface and hitting itself?
|
[
"the leading edge of the wedge produces an attached oblique shockwave that doesn't reduce the speed of the flow below Mach 1.0 if the freestream flow is supersonic.",
"Since the flow is still supersonic, passing over the corner in the center of the double wedge airfoil creates an expansion wave which increases the speed of the flow. The shock at the trailing edge is created as the flow is turned back into the direction of the freestream as if it hit a corner.",
"You would see similar phenomena with a flat plat at some non-zero angle of attack except you would have expansion waves on the upper leading edge and lower trailing edge. The diamond shape causes oblique waves at the leading and trailing edges at no angle of attack."
] |
[
"...uh. Can you explain that to me but dumber?"
] |
[
"Firs, understand that shockwaves are a discontinuity in a fluid flow. What this means is that whenever you have a shockwave, you are essentially witnessing a line in space across which fluid properties change suddenly. Continuum Mechanics says a shockwave is infinitesimally thin. Gas dynamics can prove the actual thickness is on the order of 10 atomic mean free path lengths. There is a reason for this thickness, but it is off topic so I'll answer in a follow up if anyone wants to know.",
"\nA shockwave must occur anyplace the fluid will slow down in a supersonic flow. Now, you have already cited two commonly known shock locations on an airfoil. The leading edge and the trailing edge. On a typical wedge airfoil, flow must slow down when it hits the upward sloped region at the front of the wedge, which begins at the trailing edge, speed up to go along the downward sloping back of the edge, and then slow down to the speed of the flow at infinity at the back of the airfoil, which is the trailing edge shock. The increase of speed transitioning from the front of the wedge to the back of the wedge requires that the fluid be accelerated through a Prandtl expansion wave.",
"\nFor a simple understanding, this should be enough. Anytime the flow must be decelerated, it requires a shock. Anytime it must be accelerated, it requires an expansion wave.",
"\nNow we get into some more meat. Why is there a shock at all?",
"Let's start with the math. You might have studied the differences between parabolic, elliptical, and hyperbolic PDEs in the past. If you have not, then here is a simple description: Elliptical PDEs allow information to travel everywhere in the solution space. Essentially, if there is a disturbance anywhere in the spatial plane, it affects every other location in the solution space. Hyperbolic PDEs do not allow for this. A disturbance somewhere in the solution space will travel to only certain regions. (This is very simplified.) Effectively, this is the difference between subsonic and supersonic fluid flows. At M=1, the fluid flow transitions from an elliptical PDE to a hyperbolic PDE (M=1 is parabolic). With this transition, disturbances, such as the inclusion of an airfoil, will not be felt everywhere in space. This description is given to help you try to tie the physical occurrences to mathematical phenomenons you might have studied. Now let's move on to more physically why a shock wave occurs.",
"\nInformation moves through a fluid at the speed of sound. This can change locally, but that isn't relevant at the moment. If you take any fluid out there at all and make a disturbance in it, it will cause that information to be sent out as a wave throughout the rest of the fluid, to accelerate them in whatever way it will. In other words, if you have a fluid flow and suddenly insert an airfoil into it, the a wave traveling at the speed of sound will emanate from the location you just placed the airfoil at and through the rest of the fluid. This will cause fluid to speed up, slow down, change directions, sometimes even just negligibly, in reaction to the airfoils, but only after that wave reaches them. Now what happens if the fluid itself is moving at the speed of sound (M=1). The information can't get upstream in the fluid flow. In fact, what happens is the information that the airfoil is there (transmitted by infinitesimal pressure waves) is fighting to get upstream to the rest of the fluid and just can't make it. Thus, the fluid hits the front of the airfoil and very, very suddenly slows down (this is the shock wave). It slows down, at least according to continuum mechanics, instantly. This causes the pressure to increase across the shock. Then, when the fluid gets to the top of the airfoil and encounters the downward sloped back of the wedge, it has room to expand and accelerate. Now, though, the expansion wave is not infinitesimal in thickness. It has a finite size in fact. Finally, the fluid hits the back of the airfoil and has to do two things. 1) it has to change directions again to be in the same direction as the flow at infinity, and 2) it has to slow down to be at the same speed as the flow at infinity. Both of these require a shock wave. ",
"I have heard the analogy that the fluid can't get out of the way fast enough used to describe shock waves before. It doesn't really do justice to what is occurring though. The fluid doesn't have the information that the airfoil is there until it is inside the shock wave. At this point the fluid has 10 mean free paths to decelerate.",
"\nThis is a lot of information that I have only gone into very briefly due to the nature of this forum. If there are any followups or expansions you would like please let me know. ",
"edit: I misspoke on the trailing edge condition. Pretty severely too. The fluid behind the trailing edge shock need not be in the same direction or the same velocity as the fluid at infinity from the airfoil. What is necessary is that the fluid coming off of the top portion of the airfoil be in the same direction as the fluid coming off of the bottom of the airfoil, and that the two sections of fluid flow have the same pressure. The shocks on the top and bottom of the wedge at the trailing edge are set such that these 2 conditions are met. The fluid will eventually end at the fluid conditions at infinity, but that transition occurs far from the airfoil. Sorry about that."
] |
[
"Is it possible to shake a certain distance of air (maybe with a sound wave or other method) so that it could disrupt the stability of a flying drone?"
] |
[
false
] |
[deleted]
|
[
"While I'm not sure if this is even remotely practical, the underlying physics makes me think it might at least be plausible. ",
"For one, every object has a resonant frequency. If you drive an oscillation in the object at that frequency the amplitude of oscillation gets big (e.g., a child on a swing has a specific rate they need to be pushed at, otherwise you're just shaking the chains and they won't go anywhere).",
"Mechnical resonance is a known engineering problem - skyscapers are often designed with damping systems in place. Without them, they could collapse like ",
"the Tacoma Narrows bridge, which was destroyed when strong winds drove a resonance and caused it to collapse.",
"So, in principle, you could excite a resonance with sound by providing a tone at the resonant frequency, and I see no reason why this couldn't be weaponized against a drone. ",
"The difficulty with sound is that it spreads out and gets attenuated by air. There's not much to be done about attenuation, but if you used an ",
"elliptic reflector you could, in principle, refocus your sound at your target.",
" Perhaps you'd need a laser range-finder and a fancy mechanical setup that adjusts the curvature of your reflector, but it should be possible. ",
"You'd want to use a tone whose wavelength is comparable to the length scale of the drone - somewhere in the neighorbood 10 cm. That corresponds to a frequency of about 34 Hz, that's near the lower thereshold of human hearing, which is good because bass carries. This frequency won't be attenuated much by the air. ",
"The hardest part is going to be generating a sound of sufficiently high amplitude. Sound is notorious for carrying an abyssmally tiny amount of energy - if I remember correctly, I once calculated that it would take a year of screaming at the top of your lungs to heat a cup of coffee. ",
"Given the engineering hurdles required for this to realized, I doubt it will get funding any time soon. It seems much easier to just shoot it down, ",
"or send another drone after it with a net."
] |
[
"Static air cannon?",
"I have a small toy one that will send a solo cup flying from across the room. \nI've seen truck bed mounted ones knock over stacks of hay bales. I'm betting that would take out a drone. ",
"I don't know if that fits your description but it would work. "
] |
[
"Mechanically breaking the drone with sound seems too impractical. Surely there is a way to screw with its accelerometer and make it crash.",
"Low frequency sound would shake it and cause a lot of noise. If you knew the PID coefficients you might be able to build a custom sound profile to make it overcorrect. ",
"Jamming the radio is probably the best solution but its not as much fun to dream about. ",
"Btw how do the radios communicate commands? PWM? A repeater with variable delay could shorten the pulse gap and screw with the controls. I guess that's just fancy jamming though. "
] |
[
"How is quantitative easing fundamentally different from inflation?"
] |
[
false
] | null |
[
"Quantitative Easing means the central bank creates new money, and distributes the new money out to people (by buying assets from them at market price). It increases the 'liquidity' in the economy, there is more cash and fewer assets.",
"Inflation means the amount that the prices of goods and services increases by. ",
"Inflation and QE are linked but they are not the same thing. ",
"Inflation depends on the aggregate behaviour of millions of people making decisions about what they buy and sell and at what price, what pay rises employers can afford for their employees, what taxes are added to prices, supply of raw materials etc. One factor in this mix is how much cash people have to spend, but it is far from the only factor.",
"It is entirely possible for a central bank to print more money, and for prices to go down. This has happened in Japan, for example."
] |
[
"If you think of money like you do anything else in a marketplace, you understand that it has a price, a supply, and a demand. The price is the value of the money - how much stuff can you exchange it for. Inflation is a decrease in the price of money - one dollar can't be exchanged for as much stuff as before. When the Fed engages in QE, it increases the supply of money. If the demand for money remains constant, this will result in a decrease in the price of money, aka inflation. ",
"In financial crises and periods of economic uncertainty, the demand for money tends to increase, resulting in deflation or an increase in the price of money. In other words, people are scared so they hide their money under their mattress. QE counteracts this by increasing the money supply."
] |
[
"Also keep in mind the assets that are being purchased are financial instruments issued by the banks that are buying them back. It's as though they're maturing their bonds \"early\", meaning the main benefactors are firms that hold lots of government bonds--most often banks. ",
"Increasing the money supply can cause inflation if there's no growth, but if you suspect the reason banks aren't loaning isn't because the economy is weak but just because they have a shitload of bad assets and aren't lending normally, you can give the banks a shot in the arm by paying out early on their treasury bonds. Since the economy on the ground isn't suffering from anything other than not enough loans, you don't jerk price levels around like you would from dumping money into a no-growth economy."
] |
[
"Is there any evidence to suggest that any living creature has exited the earth's atmosphere before modern science made it reasonably accessible?"
] |
[
false
] | null |
[
"Much of the debris from the ",
"Chicxulub impact",
", believed to be responsible for the ",
"Cretaceous-Paleogene extinction event",
", was ejected into space, probably carrying microbial life with it. Most of it fell back to earth along ballistic trajectories, but mathematical models of the impact indicate that some material ",
"probably escaped the Earth-Moon system",
"."
] |
[
"There was never confirmation of microbes on Mars, or being ejected from Mars. "
] |
[
"There was never confirmation of microbes on Mars, or being ejected from Mars. "
] |
[
"How do they build highways in loose sand?"
] |
[
false
] |
My question is basically only what is in the title, I am trying to find out how paved roads in the desert are made. Normally, constructors lay down a subbase on the subgrade (which in this case is sand) then a base course over that and then the pavement. The subgrade is supposed to hold the whole weight of the road, how do they solve this in the desert?
|
[
"Well it is possible because of a foundation technique known as pile foundation.",
"Piles are basically circular concrete columns that have been reinforced under the ground. There are two types of pile available",
"End bearing pile",
"Friction pile.",
"End bearing pile is the pile which transfers load to the strong soil. And friction pile distributes the load due to friction. In desert sand is available till a long depth so mainly friction pile is used."
] |
[
"So it's like the ones they use for tall buildings in desert? Is this what they use in the MENA countries for example? ",
"Just to see if I imagine it right, they put the friction (or end bearing where possible) piles in the sand and then build a new foundation on that (like the floor of a building) and then layer the road on it?"
] |
[
"I think you have a misconception how a desert looks. It's not just loose sand, desert terrain goes from loose sand to hard ground. Only about 20% is the dune filled sandy type usually depicted as desert. In most you'll find solid foundations where you can build roads like everywhere else."
] |
[
"Is all radiated heat in the form of infrared radiation?"
] |
[
false
] | null |
[
"No, thermal radiation ranges over the entire electromagnetic spectrum. The peak of the black-body curve at room temperature lies inside the infrared region, which is why people tend to associated infrared radiation with thermal radiation."
] |
[
"So, the technical term is \"Blackbody Radiation.\" This is Electromagnetic radiation that is given off by all objects warmer than absolute zero.....so, all objects.",
"The wavelengths given off are a continuous spectrum, but there is a frequency where the peak intensity occurs, as well as a minimum wavelength cutoff, beyond which there is no emission.",
"These all depend on temperature. As temperature increases, the rate of energy loss increases according to the fourth power of temperature. As temperature increases, the peak wavelength gets shorter and shorter. as does the cutoff frequency.",
"For objects on the range of ordinary temps on earth, the peak tends to be in long wavelength infrared. Heat things to around 700 deg. C. and the peak wavelength gets down into the visible range, i.e. red hot."
] |
[
"Heat as we feel it is in thermal violations of the molecules of our body. Lots of different types of electromagnetic radiation can cause molecules to vibrate. Objects around room temperature tend to emit infrared radiation, but as you heat up objects they emit other types a lot, visible and ultraviolet especially. You can see this with heated up metal, which looks red typically. That visible light can heat you up as well."
] |
[
"Could one have some immune cells removed, exposed to a pathogen, then re-inserted back into their body?"
] |
[
false
] |
If it is too difficult or impossible to make an injected version of a vaccine, is this method possible? Does this method already exist? Would it be too expensive to do this on a population scale? Could you possibly remove B cells, T cells, leukocytes, etc from an individual and have them fight a disease in vitro?
|
[
"People in this thread are heavily misinformed and/or speculating beyond the science as far as constraints are involved. This can be done, and has been done, and is being done to combat disease today. ",
"Provenge",
" is an FDA approved anti-prostate cancer immunotherapeutic drug that is derived from the haematopoeitic cells of patients. ",
"How the process works is roughly this: you take blood and cycle it through a cell sorting machine to take out the ",
" - white blood cells. You purify this fraction down to a sample mainly containing Antigen Presenting Cells. These APCs are then exposed in vitro to PAP - a very common metastatic prostate cancer antigen. They endocytose the antigen, process it and present it on their surface receptor complexes. These cells are then stimulated to activate via addition of GMCSF - a cellular signalling factor usually produced by your Helper T cells (TH2 to be specific). The combination of these signals, antigen + GMCSF, is enough to create an activated population of APCs that are then re-introduced into patients. ",
"The patients are now able to mount an immune response against PAP displaying cells - the cancer cells, and patient health outcomes improve, extending lifespan from 4-6 months in clinical trials. ",
"Needless to say, there is a huge amount of research into how to replicate this process and its clinical success in other pathological milieus. ",
"Primary research for further background:",
"http://www.sciencedirect.com/science/article/pii/S030228381101133X",
"http://www.sciencedirect.com/science/article/pii/S0022534711038511",
"http://www.sciencedirect.com/science/article/pii/S0378512211001502"
] |
[
"Good point, I had been restricting my thinking to antigen presentation happening outside the body as well."
] |
[
"Even if you could, what would be the point? I mean, why go to all the trouble of isolating something as complicated as the human immune system to make antibodies outside the body and then re-introduce them when you could just inactivate a virus and let your immune system do the work in vivo?"
] |
[
"We are able to freeze embryos and bring them back to life. Why are we unable to do the same with fully grown humans?"
] |
[
false
] | null |
[
"The main problem with cryogenics is that when we freeze things, crystals form. These crystals are what kills the organism upon unfreezing by lysing cells. In smaller subjects, we can introduce whats called a cryoprotectant, which slows the ",
" of cooling reducing the size and number of crystals formed. It is easy to bathe a few cells (embryo) in cryoprotectant, but getting it everywhere in a human body short of switching out the person's blood is impossible (and even then, switching out someone's blood with cryoprotectant would kill them)."
] |
[
"In theory I suppose it could be possible, but it's very very unlikely to happen soon. Blood is a very complex fluid, replacing it with another that performs a different action is a very difficult thing to do."
] |
[
"In theory I suppose it could be possible, but it's very very unlikely to happen soon. Blood is a very complex fluid, replacing it with another that performs a different action is a very difficult thing to do."
] |
[
"I it possible to continuously accelerate at the same rate (relative to an observer on the object) without reaching the speed of light?"
] |
[
false
] |
Lets say that and object was accelerating at a constant rate, say 10m/s/s, and there was an observer on the object. Would it be possible for the object to appear to keep its constant acceleration from the perspective of the observer on the object but appear to have its acceleration slow down as it approached the speed of light from the perspective of an observer not on the object?
|
[
"You can move with constant (and nonzero) proper acceleration and you will never reach c."
] |
[
"According to relativistic kinematics, yes this is what will happen if you accelerate with a constant force. However in reality it is not usually feasible to apply a constant force forever, because that requires an energy source and a propellant. One option is to use a Bussard Ramjet, which absorbs interstellar hydrogen, ignites nuclear fusion with it, and propels it out the back. There was a ",
"paper recently",
" looking at whether such a spaceship could accelerate forever, which found that it could provided there was no internal friction that slowed down the gas before it was expelled."
] |
[
"The rapidity will increase without bound."
] |
[
"Are there wildfires in the Amazon?"
] |
[
false
] |
I was just watching , and they were [showing clips of fly over sections of the Amazon rainforest]( Ignoring the source/wording/topic of that show (I am not intending to argue about the source, you'll get the gist of what I'm asking if it's on mute while you're watching). When I was watching that "fly over the rainforest" part, seeing those images, I was expecting it to look a bit more like the , or , where there's obvious damage to the forest from wildfires, and new fires each year. I am specifically trying to understand why the Amazon doesn't appear to be as affected by fire as the California and BC mountains/forests/rainforests. I tried researching before asking you guys, but all I am able to find is very targeted, specific articles , claiming that Amazon rainforests are earnestly fireproof on their own, but due to human interference they're now catching fire as well. Is this just because there aren't as many people in the Amazon so it's not as common for it to affect populations, and therefore not reported on as frequently? Are all of the wildfires down the West coast of Canada and the US caused by humans, and due to fewer humans residing in the Amazon it's not as common? Is this because of the types of trees that grow on the different climates being more or less resilient to fire? : I really appreciate if anyone could help explain this for me. Please and thanks in advance!!
|
[
"It's mostly due to the weather conditions. Fires thrive and grow in hot, dry conditions. The West coast is often very dry and quite hot at this time of year. Comparatively, the Amazon, being a rainforest is much more wet and humid which greatly reduces fire activity.",
"Humidity actually has such a huge effect on fire that a decent set of garden sprinklers has a realistic chance of saving a structure in a wildfire. The sprinklers increase the humidity, and wet things down, locally reducing fire intensity and also protecting things from embers.",
"As far as causes go, it's probably about the same mix. The two fires I know about in the Pacific Northwest at the moment were both caused by lightning this year.",
"Source: lived through a major wildfire in 2015, and was part of the team that established the site defences."
] |
[
"Forests burn because they do. They've been around for a lot longer than we humans have been around and living amongst them. In precontact times, several First Nations would use fire to maintain the health of the forests in their area through what amounts to prescribed burns.",
"While the trees can be reasonably fire resistant, though, everything else in the forest isn't. Smaller trees, bushes, grasses, dead trees. Fire can be a cleansing force.",
"As far as the young trees, the fire acts as a natural culling, thinning out the weaker and younger trees, leaving behind the larger/healthier specimens. That said, fire often isn't completely destructive. In the fire I went through in 2015, it's quite amazing as to what survived and what didn't, both when it comes to natural things (trees/bushes) and man-made stuff. You'd have burned out strands of trees, with two that are still alive. On the man made side of things, we lost an overlook at a waterfall to the fire, but a plastic and paper detour sign 6 feet away was undamaged.",
"It helped though that we had 20+ farm sprinklers, able to fire 2000 gallons per minute over our 20acre site."
] |
[
"I'm both thankful and disappointed in this response - thankful that you explained it, but disappointed because I was hoping for a much more complex and interesting explanation... (Sorry if I'm being unclear, I am not disappointed in ",
" response!)",
"Thanks so much for taking the time to reply, and I hope you have a fantastic weekend!"
] |
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