title
list | over_18
list | post_content
stringlengths 0
9.37k
⌀ | C1
list | C2
list | C3
list |
|---|---|---|---|---|---|
[
"Okay, just recently finished Portal 2: Say you placed a portal in an Atmosphere-less Area and one in our atmosphere, how long would it take/ would it be possible, to have our air sucked out?"
] |
[
false
] | null |
[
"Well the need to correct things that are so unneccessary that my brain would filter them out before they reach the concious part of my mind is one thing, but calling your comment an answer is beyond the reach of my understanding. You understood what OP wanted did you? Probably even before you noticed he used the word \"sucking\" that only common folks use."
] |
[
"Air would not get sucked out...it would get blown out."
] |
[
"Does this actually matter? Nobody would say \"if you breathe, air gets blown into your lungs\" It's the same thing."
] |
[
"Do animals in the wild often get painful problems such as ear infections or kidney stones, and have to suffer for a long time as they cannot cure them?"
] |
[
false
] |
I ask because I was reading about 19th century surgical procedures, and how they were often so agonising / dangerous that people would only go as a last resort, I.e their suffering was so bad that they would undergo a lot to end it. It got me thinking, if creatures in the wild often get painful ailments then there must be a great deal of suffering going on without hope of end or treatment until death.
|
[
"They do. Fortunately many animals that run in groups will groom each other (monkeys birds cats dogs) And often that takes care of the infection or irritation. May species cross groom. Birds feed on ticks on the backs of Others animals for example. Others suffer with infestations and infections from wounds but most of those animals succumb to their wounds quickly as in the wild it is survival of the fittest. The Sick and dying become prey. ",
"It's a rough thing to dwell on but if you look at it like a natural process and a part of the circle of life (que Elton John) it puts it into better perspective. "
] |
[
"This partly answers my question, I.e that most animals will die from their injuries if not strong enough to outrun prey / find food so do not suffer for long periods. And as someone said below animals have shorter life expectancies anyway in the wild so don't suffer age related diseases as often.",
"But I guess what I'm still wondering is something like kidney stones, or toothache that will not necessarily cause them to be killed due to weakness or die from it, but will be very uncomfortable for potentially years. It seems like a bit of a design flaw that the body cannot naturally cope with some things or at least limit the amount of pain experienced. (Btw if animals don't get kidney stones just let me know)",
"Also what about clams and oysters with things like (not to sound facetious) an itch or something?"
] |
[
"Yes animals in the wild can suffer for extended amounts of time. It sucks but its the way it is. Unfortunately we weren't 'designed' in a way that makes us happy, we were 'designed' by evolution to optimise our chances of passing on our genes. If it were very common for a species to get bad kidney stones then they would probably evolve over time so that kidney stones are less common, but as long as particular painful problems are rare, or affect animals only in later life (after they have passed on their genes), there is not much selective pressure to rid the population of those issues. ",
"Also clams and oysters don't really have a proper brain as such, I doubt they can experience an itch in the same way that you or I can, but they can respond to stimuli to avoid things that are 'painful' or 'uncomfortable'."
] |
[
"Why can a single individual react so differently to drugs in the same family (i.e. Xanax vs Ativan, both benzodiazepines)? And why do different individuals experience just as much variance between drugs, but not the same experiences on the same drugs as other individuals?"
] |
[
false
] |
I hope I was coherent, but I'll give some examples to clarify. Individuals A and B have been prescribed both Xanax and Ativan. (A) reports that Xanax has had a stronger effect on their anxiety, while Ativan is too mild and ineffective. (B) reports that Ativan is stronger and more effective, while his Xanax is too mild. Assuming similar BMI, same sex, and same treatment method, why are the experiences so different?
|
[
"\"Tremendous amount of molecular variation from person to person\"",
"Great answer ",
" the distribution of different protein transporters and receptors varies greatly between 'types' of neurons. These compositions vary greatly between different areas of the brain. By the time we get to the scale of different individuals, the types of molecular tuning and mechanisms can be very differentiated, think like a molecular fingerprint within the nervous system. So any drug, which acts at the molecular level, is going to have vastly different efficacy or effect depending on this unique tuning, of the relevant target proteins/mechanisms.",
"All of this is, as said above, due to genetics or the effect of the environment on genetic expression, called epigenetic regulation. Examples of epigenetic factors include recent drug use, nutrition, exercise, and, from a developmental perspective, conditions in the womb like access to oxygen and protein precursors. In the end, the effect of a drug (as opposed to the safety or toxicity, which we hope is well researched) is largely unique to an individual. All this being said, your genes control brain development according to a 'plan', the well timed production of proteins and molecules, and so while there are differences that make individuals unique, brain areas share neuron 'types' that work in fairly consistent ways, and function in systems so that small molecular effects can be used to treat neurological disorders. ",
"First time poster!! Hope this is a useful answer and shows the complexity of thinking about neuroscience at the level of the individual!!"
] |
[
"And we've only just touched on metabolism! For a tablet of lorazepam or alprazolam (Ativan and Xanax) to get from the mouth to the brain, they have to go through the gut and liver. The two are modified by different hepatic enzymes. Alprazolam, like many drugs, is metabolized by cytochrome P450, specifically CYP3A4; lorazepam skips it altogether. As these enzymes can vary substantially from person to person, and be further affected by other drugs someone's taking, it's another source of variation. ",
"Lorazepam's indifference to the liver is actually quite handy, as we often need to use benzodiazepines to prevent alcohol withdrawal, and chronic heavy drinkers are not known for their healthy livers."
] |
[
"It all has to do with different Phenotypes and Genotypes.",
"The Genotype is the set of genes in our DNA that are responsible for a particular trait (such as the ability to metabolize a certain drug class).",
"The Phenotype is the physical characteristic/expression of said trait. ",
"For example, at the lab that I work at, the Gene CYP2D6 is ran under the panel that tests for drug classes that treat Cardiovascular and Mental Health. ",
"This is taken from Wikipedia:",
"Genotype/phenotype variability[edit]\nCYP2D6 shows the largest phenotypical variability among the CYPs, largely due to genetic polymorphism. The genotype accounts for normal, reduced, and non-existent CYP2D6 function in subjects. Pharmacogenomic tests are now available to identify patients with variations in the CYP2D6 allele and have been shown to have widespread use in clinical practice.[7] The CYP2D6 function in any particular subject may be described as one of the following:[8]",
"poor metabolizer – little or no CYP2D6 function",
"intermediate metabolizers – metabolize drugs at a rate somewhere between the poor and extensive metabolizers",
"extensive metabolizer – normal CYP2D6 function",
"ultrarapid metabolizer – multiple copies of the CYP2D6 gene are expressed, and therefore greater-than-normal CYP2D6 function.",
"Source: ",
"https://en.wikipedia.org/wiki/CYP2D6",
" and I work at a tox/genetics lab."
] |
[
"Why is a hen's egg 'egg-shaped', rather than being spherical or elliptical?"
] |
[
false
] | null |
[
"The egg never falls too far from the nest. And by that I mean, if you roll a sphere, it will keep rolling in that direction. If you roll an elliptical shaped object, it will roll in one direction, but only in a certain way. an egg shape is special though. if you roll an egg, it will roll in a circle pattern, and stay generally in the same area. Try it! This is very beneficial to a bird, who doesn't want their eggs rolling away, or out of the nest at all."
] |
[
"They are designed that way to exit the chicken easier, the wider end goes first and the muscles push the tapered end.",
"Additionally, the shape keeps the eggs from rolling around in the nest too easily, and provides quite a bit of structural support.",
"Had the egg been spherical, it would easily roll around and would not be as strong and easily broken during incubation."
] |
[
"To add to this, the eggs of some birds have an extremely pointed end (almost conical) to ensure they roll in a very tight circle. IIRC guillemots and cormorants are good examples of this. They lay their eggs on bare rock ledges on cliff faces. If the eggs were to roll more than 20-30 cms away they would fall over the edge and break."
] |
[
"How does the 'scan' function on car radios find stations?"
] |
[
false
] | null |
[
"There's something called the ",
"Signal to Noise Ratio",
", or SNR. Most ham radios have the ability to set the SNR threshold at which a frequency is stopped on during a scan. Sometimes this is referred to as ",
"sqelch",
"."
] |
[
"Simple energy detection. When you change the station, you change the frequency of a local oscillator, and the mixing of the radio signal from the antenna and the LO moves the signal to \"baseband,\" where it is filtered and demodulated. The scan feature automatically changes the LO in steps, and measures the energy output of the baseband filter to determine if a signal is present. "
] |
[
"It doesn't distinguish sounds/noise/static. It's done off of a measurement of the input power on the antenna.",
"Take a noise generator. Watch in awe as your radio scan stops on EVERY channel despite no carrier frequency"
] |
[
"If I can get a tan from a ball of fire 93 million miles away, can I also tan from a smaller campfire just a few feet away?"
] |
[
false
] | null |
[
"No, not really. In order to tan you don't just need a high total amount of electromagnetic radiation (i.e. visible, infrared, and ultraviolet light), but you also need radiation of the right type. Essentially all of the tanning caused by sunlight is caused by ultraviolet light and most permanent tanning is due specifically to so-called UVB radiation, which occurs at a wavelength of 320-290nm (see ",
"this diagram",
"). The reason you need UVB radiation is that this is the wavelength range when photons become energetic enough to cause ",
"direct DNA damage",
", which (in addition to making you susceptible to cancer) promotes a process called ",
"melanogesis",
", which results in the increased production of the biological dye melanin, which gives your skin a darker appearance. ",
"Coming back to the fire, the reason it would be awful as a light source for tanning is that its spectrum would have very little of the high energy component that could cause tanning. When hot object emits thermal radiation, they do so a specific profile, called the ",
"blackbody spectrum",
", which is determined by the temperature. As you can see from that graph, the hotter the temperature of the blackbody, the more its spectrum is shifted to higher energies. The sun, which can be treated as a black-body at 5500K, has a spectrum ",
"like this",
", which peaks in the visible, but has a strong shoulder in the UV (which is weakened by absorption the atmosphere of the Earth.) On the other hand, common fires usually burn at roughly 1300K and at that temperature, the component in the UV becomes vanishingly small, as shown ",
"here",
". This means you could stand enough to the flame to scorch your skin and you still wouldn't get enough UV light to cause significant tanning."
] |
[
"BTW, one can get a good tan from arc welding a few feet away (don't actually try this though), for the welding arc does give off a broad spectrum of light radiation. "
] |
[
"I was about to ask this, because I used a MIG welder for a few hours with just gloves and a tank top in my garage, the next day I thought my arms were going to melt. Worse than any sun induced burn I've ever had."
] |
[
"How is blood detected in stool?"
] |
[
false
] |
There is a satisfactory answer as to how the works. My question pertains specifically to the 'quantitative faecal immunochemistry' or qFIT test which is more advanced. It is now used in Britain's healthcare system to detect small amounts of haemoglobin in the stool (screening for early colorectal cancer). A basic description says it uses antibodies to detect red blood cells. source also mentions: HM-JACKarc combines the qualities of a state of the art automated analyser, a bespoke faecal collection device and dedicated, sensitive, latex agglutination reagents. Which antibodies does it target specifically? How does the machine in question actually work?
|
[
"FIT uses antibodies against human globin. So it still won't differentiate between where a GI bleed is, but it's more sensitive. So it's not looking for blood, but hemoglobin. The only one I've done in the US was a card test, so you look for the line like a pregnancy test. Designed for the point of care.",
"I hate the dang guaiac test too though."
] |
[
"FIT uses antibodies against human globin. So it still won't differentiate between where a GI bleed is, but it's more sensitive. So it's not looking for blood, but hemoglobin. The only one I've done in the US was a card test, so you look for the line like a pregnancy test. Designed for the point of care.",
"I hate the dang guaiac test too though."
] |
[
"Thank you! That's very interesting about the H-antigen. So with agglutination tests, do you fix antibodies to the latex beads, and then look at whether they stick together? (indicating that they have been cross-linked by the antigen of interest). I remember reading something like that in a biochemistry textbook.. How exactly do you detect the agglutination? And what does the 'analyzer' do?"
] |
[
"Would you die of starvation if you were stranded on an island with only celery to eat?"
] |
[
false
] | null |
[
"Quick and easy answer: Yes. Your body needs many things that it cannot synthesize, specifically a set of ",
"essential amino acids",
" ",
" ",
" ",
"If you aren't eating food that contains these amino acids, your body is going to stop being able to repair itself, create new cells, and a lot of other really important processes. There are many genetic diseases that cause the pathways that we metabolize these essential amino acids to dysfunction. ",
"Maple syrup urine dieases",
" is a great example. In this disease the body cannot process leucine, isoleucine, and valine (someone correct me if I have missed something here). This diseases has a twofold effect; these amino acids and their partially metabolized byproducts build up in the body ",
" because these cannot be metabolized the body is missing extremely important building blocks. To manage this, people with MSUD have to consume a diet low in these three amino acids and take specially formulated supplements of the metabolites their body cannot produce. ",
"This doesn't even address the other issues you'd face. Celery is lacking in essential vitamins and minerals. There also is not enough actual nutrition there to meet the body's requirements to create glucose which is the basis for adenosine triphosphate (ATP) which is the \"gasoline\" for your body. Without it your body would first turn to your fat to get the energy to run things, then turn to your muscles. ",
"In the scheme of things, I'm not sure which would hit you first, but either way it would be a really terrible way to go. At least you'd be in paradise while it happened. "
] |
[
"It's a personal opinion regarding that product. I think a move towards convenience and away from cooking and sharing meals as part of our culture has been a huge part of the obesity epidemic, and the increase in eating out and decrease in family-style meals is widely cited in obesity epidemiology. The same mindset that allows fast food to thrive ubiquitously is supported in the creation and purchase of this food product. Sure, eating that food would probably be better than fast food (disclaimer: I don't know of any third-party tests on the food), but I have seen professionally how a warped view of food (seeing it as a burden or seeing it as something you just have to complete, even if it's done poorly with unhealthy food) had lead to eating disorders and problems with weight regulation."
] |
[
"Did you really not read the first sentence of my comment?",
"There has been a synthesized single food that meets all of your needs..."
] |
[
"Do mirrors reflect only visible lights, or do they reflect light of other frequencies (if so then which types--x-ray, infrared, gamma, etc)?"
] |
[
false
] | null |
[
"Yes and no, a normal mirror reflects visible light and likely near IR and UV, but it's not optimized for anything past that. Mirrors can be made for most forms of light, though it gets far harder the smaller the wavelength gets, x ray mirrors have to be almost edge on to work well, much like how glass becomes more reflective when looked at from the side rather then straight on."
] |
[
"so can X-rays be transmitted through fiber optics?"
] |
[
"That's a very good question, and to be honest i don't have a clue, but i'd also like to know."
] |
[
"If I put a drop of blood on a litmus paper, will that test my pH levels?"
] |
[
false
] |
I'm doing a little home experiment. I know that if I put saliva or urine on litmus paper, it will tell me the pH level of that. Will this also work for blood? If no, why not? Thank you!
|
[
"Your blood pH is tightly regulated, and pH paper does not have the accuracy to differentiate between small changes - that is, assuming you can discern any colour change through the blood."
] |
[
"This.",
"Unless you're in the hospital, or on your way there, your pH is 7.35-7.45. Litmus paper isn't going to pick up on differences that subtle, and the blood will stain the paper, making it difficult to determine the reading, especially considering alkaline substances turn it blue, and blood is red, and blood is only very slightly alkaline."
] |
[
"ABG's as you've linked there are not something we do routinely on all patients. They're of use in critically ill patients, and trending of chronically ill patients with respiratory symptoms.",
"They're also of use in emergency situations as I get results considerably faster, and a decent idea of the patients electrolytes considerably faster than the lab. Otherwise, they're more risky, require specialized training, or personnel (lab techs and nurses do NOT draw ABG's) and remarkably painful.",
"Any way you chose to distill blood would modify the pH, rendering the procedure pointless to perform.",
"Nitrazine",
" is a more sensitive pH test, but nothing you can pick up and use at home will be sensitive enough to be of any use.",
"I'm also not sure why you're looking to test your blood pH, it will be between 7.35-7.45, nothing else is compatible with homeostasis for any length of time."
] |
[
"Why does a galaxy not form clusters of stars similar to planets?"
] |
[
false
] |
Assuming a spiral galaxy, why do we not see large groups of gravitationally bound stars orbiting the center like a planet? Instead we see spiral Arms, not spherical clumps.
|
[
"Galaxies do form ",
"star clusters!",
" There are two main types, open (like the ",
"Pleiades",
") and globular (like ",
"M 68",
"). However, these are on much smaller scales compared to the spiral arm. "
] |
[
"Makes sense. Then why do arms of the glaxy form instead of a disk? "
] |
[
"Well our solar system is a huge cloud of things orbiting, you just can't see them as they aren't large enough to be a star. And the galaxy does have black holes, star clusters, and denser areas, but again, you don't see this in pictures because the cloud of stars is so bright. The physics is also different because of the difference in scale and time it takes to orbit the center. Then you have dark matter to consider on these scales which makes everything move at the same speed regardless of distance from the center and probably results in fewer collisions than a scaled down galaxy would."
] |
[
"Spirits:A question about the aging of whisky."
] |
[
false
] |
[deleted]
|
[
"The ",
"sheer number of compounds",
" make it not feasible to do. Even if we have identified ",
" the compounds, it takes tremendous effort and energy to produce those via synthetic methods. Definitely not worth it, considering we have a ",
" well established method and an organism that does most of the work for us."
] |
[
"an organism that does most of the work for us.",
"If you're referring to yeast, they play no part in the aging of whiskey, the aging is what happens after distillation, in barrels, and is a result of compounds in the charred wood interacting with the spirit as it moves in and out of the wood from seasonal temperature changes over years, in the case of bourbons, or, in the case of other whiskeys, interactions between the wood, and the remnants of the spirit that had been aged in that barrel previously.",
"American bourbon uses new charred white oak barrels, they are used once, then sold to other distilleries, breweries and such, many Scotch distilleries love using once used American bourbon barrels for aging their, obviously inferior ;) , product. "
] |
[
"That's correct. Even though I initially meant yeast in the context of alcohol and all the metabolic products, the source of sugar, the aromatic compounds and esters, and even the wood are all from organisms who do the work for us. That is, we can analyze what's extracted from the wood as part of the aging process and do what OP suggests, but there's still an easier method."
] |
[
"Introducing: AskScience Quarterly, a new popular science magazine by the scientists of reddit!"
] |
[
false
] |
Hello everyone! We're happy to present, The moderator team at have put a lot of effort into a new popular science magazine written by scientists on reddit. The goal of this magazine is to explore interesting topics in current science research in a way that is reader accessible, but still contains technical details for those that are interested. The first issue clocks in at 16 illustrated pages and it's available in [several] free formats: (thanks , best quality ) (best quality, ) (for e-readers) (web browsing) (best quality) (thanks ) Here's a full table of contents for this issue: - - by Dr. William MK Connelly - - by Demetri Pananos We hope you enjoy reading. :) If you have questions, letters, concerns, leave them in the comments, message the moderators, or leave an email at the address in the magazine's contact's page. We'll have a mailbag for Issue 2 and print some of them! Edit: If you're interested in discussing the content of the issue, please head over to ! Edit2: reddit Gold buys you my love and affection.
|
[
"Hi, mods. Thanks for doing this! Graphic Designer here with a science degree and extensive experience in publication design. Not looking to trump your current designer. Willing to volunteer my service if you ever find yourself in a pickle. PM me.",
"Edit: Please don't interpret this as a shot at your current design. It is not. Sometimes it's hard to find people who value design as a real contribution; I want to help and it's the only thing I have to offer. "
] |
[
"I second getting more graphic design eyes on this project."
] |
[
"This is great! Any plans to add an index of sources for further reading? "
] |
[
"Is it possible for a concussion, especially an untreated one, to worsen the effects of certain conditions or disorders?"
] |
[
false
] |
I know this is going to be a really dumb question and I'm sorry if I sound like an anti vax mom by the end of it.Is it possible for a concussion to worsen the effects of, for example, my autism. I got concussed several years ago, about three months before I recieved my diagnosis, and never really got medical treatment for it, and I am curious as to whether it is possible that it worsened the symptoms? I'm aware it is developmental disorder, so I know I was born with it. I just remember the symptoms being worse since then? Or is it simply a case of I'm just more aware of it now, so it just seems worse, meanwhile it has always been the same?
|
[
"For an uncomplicated, mild head injury (i.e., nothing wrong on brain imaging), most kids and adolescents return to baseline functioning within a month. But there are a lot of factors that influence that recovery time. Preexisting developmental or neurological concerns (like ASD, ADHD, seizures) can push that window out. It is tricky to interpret though, because most studies don't look at how people were doing ",
", just comparing to see whether/when they get back to average. See ",
"here",
", for instance.",
"It's also worth pointing out that for many people with mild head injuries, there are a number of stressors that come with the initial injury: being unable to do enjoyable activities, falling behind in school/work, etc. Those stressors can ",
"exacerbate symptoms of depression and anxiety",
" that may have been pre-existing. Mood disorders like that ALSO ",
"lead to mild cognitive impairments",
". That makes a lot of people think that they have lingering cognitive complaints from the brain injury itself, even when the injury might have healed. ",
"With that said, you should always follow up with a doc if you have any concerns your recovery."
] |
[
"To add to this, there isn’t much “treatment” you can have done after a concussion beyond rest, avoiding stressful activity, and specific therapies for loss of function caused by the event like walking or neck injury rehab. Your brain heals itself from a minor head injury and we don’t have any pill or shot that I’m aware of that helps that process along, so it’s not like you missed out on a standard post-concussion treatment."
] |
[
"I'll try to check with a doc first chance I get, but I think I said it in another comment, but I'm still technically a minor, so itll be a bit hard. Thank you for answering, I appreciate it."
] |
[
"In string theory, is it known how long a string is? Does this question even make sense?"
] |
[
false
] |
More importantly, are strings thought to be actual physical objects that we could interact with if we had any way of operating on that sort of scale? Or it it just that the mathematical model of vibrations on a string is the closest thing we have to the relevant differential equations that is still something scientists can explain to laypeople?
|
[
"The length of the strings is believed to be close to the Planck length, about 1.6*10",
" meters."
] |
[
"It isn't theoretical. Quantum mechanics is a very physical science, however things that apply to real life don't apply on that minuscule a scale. Things like electrons \"teleporting\" around in their shells make no sense on a macroscopic (real-life-sized) scale, but they just happen in quantum mechanics. As the saying goes, if you use an analogy to explain something in quantum theory, you're wrong.",
"It should also be noted that I'm also in high school. However, I'm very interested in this sort of thing and have been learning about it for years."
] |
[
"No, the string is 1 dimensional as a point is zero dimensional and a surface is two dimensional.",
"It would be \"in\" the 11 dimensions of string theory... or however many they are at nowadays. You can have a one dimensional object in multiple dimensions.. for example a surface bending around in three dimensions. It's still a two dimensional surface, but it \"lives in\" three."
] |
[
"What is the purpose of Maggot Therapy?"
] |
[
false
] |
From what i saw in a youtube video it looked like someone had a hole in their foot or something and it looked pretty infected. Some doctors then put bunch of baby maggots into the wound and wrapped it up. The footage then fast-forwards to when they take off the bandage and it shows the maggots had multiplied and gotten much bigger and were living in the hole of the foot. What is the purpose of doing this? What exactly are they doing? In what cases is this used? Whats other info you could explain about it? Seems like a really interesting procedure, would be cool to know more about it.
|
[
"Its been a while since this question was asked so I doubt many people will see this, but as its about the only field I have some experience in I felt obliged to respond. I’ve been working with a University in researching aspects of maggot therapy and I’ve gained a bit of knowledge about how it works. So here’s my two cents worth.",
"Maggot therapy has a bit of a hard time being taken seriously as it is seen as some primitive medieval cure, sort of on a par with using leeches. It’s often seen as dirty because of their association with death and decay and many patients don’t like the idea of maggot crawling around their skin. Also, many clinicians don’t like handling them and applying them. Maggots have a serious image problem and, as a result, it is still often a treatment of last resort. Recent discoveries in the field, however, have shown that these guys can be pretty effective.",
"Maggot therapy is only used to treat infected, chronic wounds. Any wound can become chronic if it doesn't heal within a reasonable amount of time – this is usually because of some underlying condition that the patient has which prevents their body from going through the normal process of healing. This is common in diabetics, especially in their feet where ulcers develop and cannot heal due to poor blood circulation. Because the wound is exposed and unable to heal, it is at high risk of becoming infected with bacteria which kills the tissue inside the wound and results in necrosis. Necrosis is characterised by ",
"this yellow/black tissue",
" (called ‘slough’) inside the wound.",
"The presence of this necrotic slough is very dangerous as the bacteria can proliferate causing infection to spread to surrounding tissue. So, we need to get rid of the dead tissue to prevent further infection and to allow the wound to heal properly. This is where the maggots come in. ",
"Maggot therapy usually uses the larvae from a particular species of fly called Lucilia sericata (aka. The common greenbottle fly). This species is used because they are ‘necrophagous’ – they consume only dead (necrotic) tissue. Their digestive secretions are unable to break down living tissue which is ideal for us as they are able consume all the necrotic tissue inside the wound whilst leaving the living healthy tissue alone.",
"There are two ways that maggots can be applied. The first is the traditional ‘loose’ method where the maggots are applied directly to the wound and are then covered with various dressings. A new method that is sometimes used is where the maggots are sealed inside a permeable polythene bag, not unlike a teabag. This removes the risk of them escaping, makes the application and removal of the maggots much easier, and often eases patients fears of having maggots crawling on their skin as there is no way for them to get out.",
"The maggots can still feed through the bag as they break down the dead tissue through a process called ‘extracorporeal digestion’, meaning they digest their food outside of the body. The maggots release a cocktail of digestive secretions which breaks down the dead tissue into a liquid which they then consume. As the bag is permeable, the larval secretions and wound fluids can flow freely into and out of the bag and their feeding is not hindered. ",
"Pic",
"The application method used will depend on the characteristics of the wound. Smaller, shallower wounds would favour the bagged method, whilst larger, deeper wounds would favour the loose method.",
"Medicinal maggots are sterile so there is no risk of introducing any new pathogens to the wound. They are usually applied at a density of 5-10 maggots per cm². They are only a couple of millimetres in size when they are first applied, but they’re basically little eating machines and will grow many times larger as they feed on the dead tissue. They won’t have multiplied inside the wound as you suggested because they are still in their juvenile state, but it can certainly look like it because of how quickly they grow in size. They are usually left on a wound up to 4-5 days at which point they have finished feeding and so will have to be replaced if any necrotic tissue remains.",
"When they’ve finished, the larvae leave behind ",
"a nice, clean wound",
" that is free from infection, which, with some proper maintenance from clinicians, should eventually heal.",
"Maggot therapy has enjoyed a bit of a resurgence in recent years. Whilst its use was initially popular in the 1930s and 40s, it fell into obscurity after the discovery and mass-production of antibiotics such as penicillin. It then wasn’t until the 80s and 90s that people began to question how maggot therapy actually compared to other wound treatments, especially considering the rise of antibiotic resistance in some bacteria (eg. MRSA). The resulting studies found that maggot therapy was more effective in treating chronic wounds and since then the efficacy, simplicity, and low toxicity of maggot therapy has led to a greater acceptance by wound therapists.",
"Relatively little is still known about the therapy as it went unused for much of the 20th century, but this renewed interest has fueled a great deal of new research in the area. The advantage of using maggot therapy is not only in the removal of dead tissue, there is also evidence that they disinfect wounds by destroying bacteria, and that they actually stimulate wound healing by promoting the proliferation of new cells. All of these aspects are now being researched to try and uncover how exactly the maggot do what they do.",
"For some extra reading I’d recommend:",
"Maggot Therapy: a handbook of maggot-assisted wound healing. Fleishmass, Grassberger & Sherman",
"Maggot Therapy Takes Us Back to the Future of Wound Care: New and Improved Maggot Therapy for the 21st Century",
"Some more maggot videos:",
"http://www.youtube.com/watch?v=bAY7OKp6D7w",
"http://www.youtube.com/watch?v=OHR5WF5QKK4",
"http://www.youtube.com/watch?v=5QOJ_sMWF38",
"http://www.youtube.com/watch?v=6Xt6NWkgydM",
"I hope I've answered some of your questions. Feel free to ask if you have any more.",
"Edit. Spelling",
"Edit. This is getting much more attention than I expected. Thanks for the gold! Such a nice surprise."
] |
[
"Precisely this. The companies that produce the maggots have their own fly colonies that they collect the eggs from which consists of numerous cages containing 400-600 flies each. They are sustained on sugar and water alone but will only produce and lay eggs when given protein. This little quirk of nature allows the companies to control when the eggs are collected.",
"The fly's protein meals come in the form of pieces of fresh pigs liver which are placed into the cages when the eggs are required. The flies lay their eggs on the liver which are then removed. The eggs are scraped off the liver and are sterilised and from this moment on are kept in a completely sterile environment. The little maggot embryo inside the egg is naturally sterile anyway so when it hatches, as long as there is no contamination through the production process, they will remain so until they reach the patient.",
"The source given by HankyPankadin gives more information."
] |
[
"The fly eggs are disinfected prior to hatching, when the maggots are \"born\" or hatch they are kept in a perfectly sterile environment, free of bacteria, and can be disinfected again before they are introduced to the wound. ",
"Here is the source, page 28"
] |
[
"How do the 6 arms of a snowflake form symmetrically?"
] |
[
false
] |
I just watched this video that was posted by IFLS [ ] and it shows how a snowflake is formed. In the video you can see that the 6 arms of an individual snowflake form independently from each other yet they form the same general pattern. Considering how many different patterns snowflakes can form (supposedly no two snowflakes are the same) why do the 6 arms of a single snowflake look so similar?
|
[
"This is a great question. I asked this in a crystallography class, and the answer my prof gave was that the crystallization is deterministic but extremely dependent on the local thermodynamic conditions (temperature, humidity) so the arms of the same snowflake are likely to be identical compared to the arms of different snow flakes. Of course not all snowflakes grow with nice symmetry like this.",
"However in this video, the arms grow at different rates which would seem to refute this hypothesis because the changes in growth rate would change the local temperature and humidity conditions significantly.",
"Hopefully someone with another explanation comes along."
] |
[
"I believe the video is likely showing melting or sublimation of snowflakes in reverse."
] |
[
"That would make a lot of sense. I'm not sure if anyone has ever managed to make artificial snowflakes. However, it is relatively easy to catch them and put them under a microscope."
] |
[
"A friend of a friend linked me to this article as we were discussing flu vaccinations. Is this real science?"
] |
[
false
] | null |
[
"The flu vaccine is the best way to prevent getting the flu. The people on your facebook wall have no idea what they're talking about. You are correct that even healthy people can get the flu.",
"http://www.cdc.gov/flu/about/qa/flushot.htm#howeffective"
] |
[
"I think what people on facebook are alluding to is the general hystaria the industrialised world has towards getting sick. It has been proven that children who are 'sheltered' immune-system wise (ex: not allowed to eat dirt!) when they are young get sick more when they're older because their immune system isn't aware of what's out there. It doesn't really pertain to the flu much, except perhaps that you may get the flu less if you ate lots of bugs and dirt as a baby...",
"I cant find the actual article I read, but a the ",
"NY Times gives a good overview"
] |
[
"Give \"Dr.\" Mercola's ",
"Wiki page",
" a thorough read. He seems to be peddling the most popular mix of misinformation and expensive supplements that's been plaguing us since the 80s. ",
"Ben Goldacre in his ",
"Bad Science",
" gives a thorough rundown of the majority of such claims and judges them, to put it mildly, incompatible with evidence-based medicine.",
"It might seem like I'm attacking the man and not the idea, but I am firmly convinced that the information in Goldacre's book can save lives. As to the particular topic on hand, take a look at this ",
"Cochrane review of 50 reported influenza vaccine studies",
", notably \"Vaccination had a modest effect on time off work and had no effect on hospital admissions or complication rates.\". In fact, the Cochrane Collaboration does a tremendous job of, in their own words, \"preparing, maintaining and promoting the accessibility of systematic reviews of the effects of health care\"."
] |
[
"Could a black hole's event horizon be altered by the gravity of another black hole passing nearby?"
] |
[
false
] |
If it can change, what does that say about particles/energy in the space that the event horizon has retreated from? Have they escaped?
|
[
"The event horizon is a gravitational phenomenon and any changes in the event horizon itself will propagate at c."
] |
[
"Light can only orbit a black hole at 1.5 times the radius of the event horizon (in the case of a Schwarzschild black hole). This is called the ",
"photon sphere",
"."
] |
[
"Yes, nearby objects affect the shape of a Black Hole event horizon.",
"As for retrieving information, that's impossible. Keep in mind that the event horizon is a spatio-",
" boundary. It is a boundary in time as well as space. Things that have crossed the horizon aren't there anymore, so 'moving' the horizon (with respect to a distant observer) doesn't retrieve something that is beyond the horizon because that thing isn't there anymore. It's fallen into the hole, presumably extremely quickly."
] |
[
"Can we repair damaged nerves?"
] |
[
false
] |
If yes, which ones and how?
|
[
"Yes, nerves can be repaired. If nerves are severed, they can be stitched back together. If a larger piece is damaged, it may require a nerve graft, where the damaged area is removed and another nerve (from elsewhere in your body or from a cadaver) is stitched on to either side. However, this isn't like grafting a blood vessel where it just starts working. You're really making the tunnel that the nerve fibers within it are travelling through, and these need to regrow and reconnect. It's a slow process - about 1 mm a day, and therapy is usually needed to control discomfort and make sure nothing atrophies."
] |
[
"The graft itself isn't always made of nerve tissue. Neuroflex is ",
"an inert collagen tube",
" impregnated with chemical cofactors that stimulate nerve growth. The surgeon takes the dried tube out of the sterile pouch and rehydrates it in saline. The nerve endings are stitched into the tube and after the nerve endings grow into each other, the collagen matrix is reabsorbed by the body."
] |
[
"We can take nerves from dead bodies? Does it have the same limitations as donated organs? like “freshness”?"
] |
[
"Apparently if you could compress Mt. Everest into the space of a pin head it would create a black hole. Is this true?"
] |
[
false
] |
[deleted]
|
[
"What you are looking for is the Schwarzschild radius which is the size of the ball you would need to compress an object into for it to become a black hole. You can find the equation ",
"on wikipedia",
". The article even gives you an estimate of 9.46*10",
" nm for mount Everest. This is a lot smaller than a pinhead and we do not believe it's possible for such a small black hole to form."
] |
[
"Thats about 10",
" nm or 10",
" m or a picometer. For a sense of scale, the atomic radius of hydrogen is about 25 picometers (that is the radius of the electron orbitals around the nucleus, the nucleus itself is on the order of 10",
" m in diameter). So 25 of these black holes could be arranged across a hydrogen atom. That's pretty teeny."
] |
[
"9.46*10-4",
"Can you give an example of something that is this small? I have a hard time grasping this value."
] |
[
"How were the ancestors of modern birds able to survive the mass extinctions that killed off the dinosaurs?"
] |
[
false
] |
I know very little about the subject other than I kind of remember that the first sort of mammalian creatures were often able to survive by burrowing underground and/or having fur that kept them warm during the ice age. Is there any truth to this? How did birds survive?
|
[
"The theories on the Cretaceous extinction go hand in hand with how the birds survived. There's a number of adaptations the birds had that won them advantage over the circumstances scientists theorize killed off the dinosaurs. Although, we don't know ",
" how birds survived the extinction, here are some important theories/ adaptations to consider.",
"- Birds had a relatively large brain to body mass ratio and in this case birds were quite intelligent; more intelligent than most dinosaurs. Troodon was as big-brained and smart as a dinosaur could get, and even then they were extremely bird-like.",
": Birds are pretty small compared to their dinosaur cousins. This allows them to be more adaptable. Think about bacteria or insects which are extremely small compared to others animals and have existed far before the dinosaurs and/or survived longer. Small animals require less energy than larger animals, so birds could adapt to most habitats while large sauropods and big dinosaurs needed a certain habitat that has the right resources to maintain their size.",
": Birds have a vastly variable diet. Being omnivorous means an organism has larger selection of food available in the environment. Large dinosaurs were mainly specialized, an obvious example being the sauropods and the spinosaurids.",
": The effect of egg shape on the survival of the birds is still debated. Most theropods and dinosaurs simply buried their eggs, letting the environment discern its survival, while early birds sat on them for incubation. Perhaps this prolonged ",
" ",
"That's pretty much the gist of it. I think size is the best explanation for why they survived, but it's ultimately up to people to choose what they believe. Nonetheless, more research on the subject couldn't hurt."
] |
[
"http://www.smithsonianmag.com/science-nature/why-did-mammals-survive-when-dinosaurs-perished-63229592/",
"Probably similar to why mammals survived, a combination of small bodies and adaptable eating habits made them less likely to starve than large, specialized dinosaurs, as well as taking shelter in burrows during the brief searing heat that followed the asteroid impact."
] |
[
"Do you know if their ability to travel large distances is a considered to be a major factor? ",
"I would suppose the climate and food sources kept changing dramatically across different geographies across the years. Birds could move from one liveable location to the next and find food in new places as required. ",
"As the weather changed, land based animals could only move a few kilometres per day and could be stuck in a huge zone with horrible weather and / or no suitable food. So they'd be more likely to die off. "
] |
[
"Will a vacuum \"float\""
] |
[
false
] |
If I had a super strong lightweight container that had an almost complete vacuum inside would it rise in our atmosphere like a helium filled balloon?
|
[
"If the container was strong enough to contain the vacuum without collapsing, and light enough to mean the total volume displaced weighed less than the equivalent weight of surrounding air, yes."
] |
[
"This was answered yesterday. A total vacuum is only 16 percent more buoyant in air than helium, therefore, you'd need to be able to construct a container that was only 16 percent more heavy than an equivalent helium balloon. But yes, if you were able to do that, a vacuum container balloon would float. "
] |
[
"Possibly, but there's a lot of hype when it comes to nanofabricated materials - and the media which reports on it treats it like fairy dust. "
] |
[
"Trapping the suns light."
] |
[
false
] |
So if the sun emits particles/rays of light, why isn't it possible to "trap" these particle in a box? What makes them vanish, or do they simply decay over time? Even if they do, wouldn't they still exist for a brief period in this box?
|
[
"This is a general question about light, regardless of the source producing it (sun, candle, laser, etc.) Light spreads out as it propagates, becoming weaker in intensity because the same energy is spread over larger and larger areas. Light doesn't actually disappear unless it is absorbed by matter, in which case the energy it carries is converted into a different form (motion of particles for example).",
"It's definitely possible to trap light in a box or other type of resonator, just like sound can be contained in a resonant chamber (like an acoustic guitar body). In a resonator, waves propagate around the structure continuously. They don't decay unless they leak out of the resonator or are absorbed in the walls. For light, this has been achieved with a variety of different structures. Some of the best are made from micro-sized (~10",
" - 10",
" m) spheres in which the light is confined to circulate near the walls. However, these can still only confine the light for a short period of time (micro or nanoseconds). "
] |
[
"When light is absorbed by matter, is the entire sum of it's original energy that has spread over a larger area absorbed, or just the energy remaining?"
] |
[
"so, theoretically, if I get into a 6x6x6 box, and it is out in a field with bright sunlight, and it is closed shut, why is it darkened immediately? shouldn't there be light \"trapped\" inside?"
] |
[
"Are there any drugs that have stopped being used because the disease evolved total resistance to it?"
] |
[
false
] | null |
[
"There are many examples; here is one:",
"1-adamantylamine was once commonly used to treat influenza. Its target is the M2 pore protein of the virus. Over time, the gene for this protein mutated, and now practically all influenza virus is resistant.",
"From ",
"https://en.wikipedia.org/wiki/Amantadine",
"Amantadine is no longer recommended for treatment of influenza A infection. For the 2008/2009 flu season, the CDC found that 100% of seasonal H3N2 and 2009 pandemic flu samples tested have shown resistance to adamantanes. The CDC issued an alert to doctors to prescribe the neuraminidase inhibitors oseltamivir and zanamivir instead of amantadine and rimantadine for treatment of flu. A 2014 Cochrane review did not find benefit for the prevention or treatment of influenza A."
] |
[
"Yes, this is unfortunately quite common, and is an active area of research in both antibiotic and antiviral medications.",
"I'm a chemist and actually recently received funding from NIH directly related to this issue. One of the systems our lab studies is the Influenza A M2 protein. We study the structure and function of this protein along with its interactions with antiviral medications. ",
"The adamantane class of influenza antivirals (amantadine and rimantadine) are one of only two classes of FDA approved influenza antivirals (the other class being neuraminidase inhibitors such as oseltamivir AKA Tamiflu). This adamantane class of antivirals works by blocking the proton channel in the M2 protein. Proton conduction through this channel is necessary for the acidification of the endosome, a key step in the viral life cycle. Interrupting this acidification prevents the production of new viruses. ",
"In recent years, greater than 99% of circulating flu viruses are resistant to both amantadine and rimantadine; the CDC no longer recommends their use in the treatment of influenza infections.",
" This resistance has come about from certain mutations, such as the S31N mutation which affect the binding of amantadine and rimantadine to the influenza A M2 channel. My current study aims to better understand the proton conduction mechanism of this protein and to understand how the interactions of certain adamantane class drugs, which are still effective against these mutants, with the M2 protein differ from adamantane and rimantadine."
] |
[
"Yes. The name comes from the adamantyl group, see here: ",
"https://en.wikipedia.org/wiki/Adamantane",
"The \"adamantane\" name is derived from the Greek word for \"diamond\" since the adamantane structure has a similar arrangement to the diamond crystal structure."
] |
[
"How does human body excrete radioactive materials once they have been inhaled and/or ingested?"
] |
[
false
] |
For example, if a cigarette smoker would stop smoking today and we only take Po210 and Pb210 (those reside on tobacco) in consideration in the lungs, will the body eventually excrete these materials, some of them, or none at all?
|
[
"Stuff in the lungs isnt excreted, anything foreign, I can tell you ask a smoker of a few things over the years, you will end up coughing out.",
"I'm not aware if the radioactive elements build up to more risky levels compared to the day to day levels of other like elements in the body.",
"Just try to avoid russian cigarettes."
] |
[
"Radioactive elements get treated by the body much like 'regular' ones, and may end up being utilized in some cases (which is why radioactive jodium can be such a threat: the body stores it in the throat for later user because it doesn't treat it differently than 'healthy' jodium).",
"Sometimes, they disappear in ways regular waste disappears: we exhale them or extrude them in sweat, urine, or feces.",
"Other times, the element simply decays into something non-radioactive, which may then remain in the body for any amount of time.",
"I'm not aware of any mechanism for specifically removing radioactive elements, though."
] |
[
"What about the russian cigs?"
] |
[
"Are the isotopic abundances of Pb-206, -207, and -208 only attributed to the fact that they have decayed from their respective parents?"
] |
[
false
] |
I'm getting at the term "common Pb" and what, exactly, it refers to. I know common Pb is essentially Pb that is not the product of radioactive decay, but does that mean it's only referring to Pb-204? Or is there Pb-206, -207, and -208 that formed without radioactive decay? Or are 206, 207, and 208 only generated from radioactive decay, but they become "common" once they are essentially free from the system they were created in?
|
[
"Pb",
" was formed during the big bang",
"No it was not. The big bang only formed hydrogen, helium and traces of lithium. Everything beyond that comes from stars or stellar remnants.",
"\"Primordial\" means present when Earth formed. It has nothing to do with the big bang.",
"where as the other stable isotopes are formed from their parent isotopes.",
"Some of their nuclei are primordial as well. They just have additional nuclei from decays."
] |
[
"I understand his error...",
"Primordial Lead is a term used in geology to refer to the original 204Pb/Pb206 ratio that existed at the time of Earth's formation. ",
"Since we cannot access the Earth's primordial Lead ratio, no terrestrial rocks are that old, the standard 204Pb/206Pb ratio (0.10745) is taken from the Canyon Diabolo meteorite, specifically Lead in the mineral Triolite. It is assumed to closely match the Earth's primordial Lead ratio."
] |
[
"We have Pb-207 from:"
] |
[
"What is the maximum depth at which caves can form?"
] |
[
false
] |
I'm a physics student with next to none background about the earth sciences. I had the thought that if a cave is deep enough, the weight that you feel would be reduced as compared to the weight you feel up here, since the big chunk of rock on top of you would be exerting a gravitational force in the opposite direction of the ground. Although pictures like don't give me much hope for an interesting answer, I still want to to see what happens.
|
[
"I don't know too much about geoscience, but I'm going to guess that no. What you are suggesting is that this cave would have to be in the mantle at least a quarter of the earth approximately deep, if not more. ",
"However, since the cores are on average 3 times denser than the mantle, i think for it theoretically work, for you feel a difference, you would have to be st least in the lower mantle. ",
"Practically, due to the high pressures and heat, it would probably be near impossible to access"
] |
[
"When I thought about this I had no idea how thin the crust is in relation to the rest of the layers. I still think there might be some measurable difference, but nothing in the orders of magnitude that would cause any unusual phenomena.",
"Thank you for your help. "
] |
[
"Obviously its measurable, theoretically I cab calculate the gravitational attraction between me and an apple, or even me and Pluto. "
] |
[
"What’s the deal with the Sputnik V vaccine? How effective is it and why is it so controversial?"
] |
[
false
] |
Different countries are planning to use the vaccine, isn’t it dangerous if it wasn’t properly tested? How does it stack up with BionTech or Moderna for example? Edit: was->wasn’t
|
[
"The “Sputnik” COVID vaccine is a fairly standard approach to modern vaccines. It consists of the SARS-CoV-2 spike protein, in replication-defective recombinant adenoviruses. They used a slightly novel approach by using two different adenoviruses, human Ad26 and Ad5. ",
"This is a very generic approach. Replication-defective adenoviruses are very well understood and have been used in many different contexts in humans. One disadvantage is that the wild viruses are very common in humans and there’s widespread immunity to them, so there’s the potential that immunity will block the vaccine carrier. A Chinese COVID vaccine using Ad5 as a carrier found this may be a concern since responses were lower in Ad5-immune people. The AstraZeneca/Oxford vaccine uses a similar approach but uses a chimpanzee adenovirus that humans aren’t immune to, to avoid this problem. The Sputnik approach is to use two different adenoviruses instead. ",
"So it’s a pretty well understood approach, and what we’ve seen with COVID vaccines so far is that they aren’t a real challenge - it’s quite easy to get good, durable immunity against SARS-CoV-2 using many different approaches. ",
"The reason it’s controversial is that the Russians haven’t been at all forthcoming about the data. They’ve released some small scale data (",
"Safety and immunogenicity of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine in two formulations: two open, non-randomised phase 1/2 studies from Russia",
") but no large scale safety data. What’s more, the official announcements have seemed to jump directly from small trials to widespread deployment, without waiting for large Phase 3 trials. ",
"(Also, there were questions about the quality of the data in the Phase 1/2 trials, but I won’t get into that.)",
"There’s no particular reason to ",
" this to be anything but safe, but vaccines need to be tested. These vaccines ",
" undergoing Phase 3 clinical trials involving several tens of thousands of people:",
"The researchers launched clinical trials in June. On Aug. 11, President Vladimir V. Putin announced that a Russian health care regulator had approved the vaccine, renamed Sputnik V, before Phase 3 trials had even begun. Vaccine experts decried the move as risky, and Russia later walked back the announcement, saying that the approval was a “conditional registration certificate,” which would depend on positive results from Phase 3 trials. Those trials, initially planned for just 2,000 volunteers, were expanded to 40,000. In addition to Russia, volunteers were recruited in Belarus, the United Arab Emirates, and Venezuela. On Oct. 17, a Phase 2/3 trial was launched in India.",
"—",
"Coronavirus Vaccine Tracker",
"But there are also ethical questions about those trials:",
"Against this backdrop, the phase 3 trials of Sputnik V have already begun. However, the required 40 000 volunteers stirred a political and human rights debate. Some Russian media reports cite the Federation contemplating to roll out a mass vaccination programme for Sputnik V. The head of a trade union for physicians, Anastasia Vasilieva (The Doctors’ Alliance, Moscow), who exposed the flaws in Russia's COVID-19 numbers, questions the plans for mass vaccination and mandating volunteering as a “real sabotage”.",
"—",
"The arrival of Sputnik V",
"So bottom line, there’s nothing clearly ",
" with the vaccine, the principles are solid and well understood, but the overall political approach to this has left people concerned that the politics may have pushed the science instead of the other way around."
] |
[
"This is an incredibly balanced answer. Thank you for taking the time to write this"
] |
[
"Thank you for this. This is the best kind of internet."
] |
[
"How come we can see laser beams?"
] |
[
false
] |
Its light traveling in only one direction, how come it hits our eyes?
|
[
"Unless the beam were pointed into your eye, which I do not recommend, then that is correct. You can imagine taking your laser down to the individual photon level. In a vacuum, nothing will cause it to deflect towards your eye."
] |
[
"You are seeing the light that's scattering off air molecules, and potentially other stuff like dust in the air. This redirects the photons to your eyes."
] |
[
"Unless it was so powerful that the electric fields exceed the Schwinger field, then it will create electron positron pairs from the vacuum, and scatter from those."
] |
[
"If the human brain was a computer, how much RAM would it have?"
] |
[
false
] | null |
[
"The brain really doesn't function in a way directly analagous to a computer, it simply isn't possible to answer your question. It both processes and stores information in a very different way."
] |
[
"I think this analogy is too stretched. The conclusions are really only reasonable in an extremely limited set of comparisons, with the only real lesson being that computers work differently to brains.",
"the human brain would not have very much RAM, let alone processing power ",
"You can probably almost immediately recognise any one of many tens, if not hundreds of faces. Is all of the information necessary being kept in ram? How long would a computer take to do that task? How much memory would it need? I think it would compare poorly, especially if the task goes from a cold start - whereas you're probably as good at it just after waking up as in the middle of the day.",
"I don't think this really tells you very much, though, other than that the comparison is too strained to be really useful.",
"think of how long it takes to do complex math on a computer vs. a human",
"This doesn't really tell you that brains are bad at processing, it simply tells you that they don't work like computers. We could equally well note how the brain excels at complex analysis tasks such as abstract strategy games like Go, where computer processing power still doesn't rival what humans can manage. It isn't even clear whether this is a ram or processing task within the analogy. But either way, the computer's superior processing and ram fail to match whatever the human has in this analogy."
] |
[
"I think this analogy is too stretched. The conclusions are really only reasonable in an extremely limited set of comparisons, with the only real lesson being that computers work differently to brains.",
"the human brain would not have very much RAM, let alone processing power ",
"You can probably almost immediately recognise any one of many tens, if not hundreds of faces. Is all of the information necessary being kept in ram? How long would a computer take to do that task? How much memory would it need? I think it would compare poorly, especially if the task goes from a cold start - whereas you're probably as good at it just after waking up as in the middle of the day.",
"I don't think this really tells you very much, though, other than that the comparison is too strained to be really useful.",
"think of how long it takes to do complex math on a computer vs. a human",
"This doesn't really tell you that brains are bad at processing, it simply tells you that they don't work like computers. We could equally well note how the brain excels at complex analysis tasks such as abstract strategy games like Go, where computer processing power still doesn't rival what humans can manage. It isn't even clear whether this is a ram or processing task within the analogy. But either way, the computer's superior processing and ram fail to match whatever the human has in this analogy."
] |
[
"How do blood transfusions work?"
] |
[
false
] |
Since blood is made up of blood cells, those cells need an organism to live in don't they? Wouldn't the blood cells die when they have been away from the body a certain amount of time? [And if not, why not?]
|
[
"Yes they will die eventually. Blood transfusions are broken down into several parts (red blood cells, platelets, and plasma being the chief ones). Each has a different lifespan, and plasma can be frozen to prolong its lifespan. The others are refrigerated to extend their lifespan."
] |
[
"Yes, once separated into their components, blood products have a limited shelf life. Platelets last 5 days, while packed red blood cells can last anywhere from 21 to 42 days depending on the type of preservative used. Plasma, when frozen quickly after donation, called Fresh Frozen Plasma, can be stored for up to 1 year.",
"It is possible to freeze red blood cells combined with a glycerol preservative at -65C for up to 10 years. The process of deglycerolizing blood is expensive and time consuming, and you end up losing a good deal of red cells. However this is really only done in circumstances where there is need for special transfusions (super rare blood types)."
] |
[
"So if I donate blood, it has to be used before a certain time?"
] |
[
"Why can we only concentrate on one thing at a time?"
] |
[
false
] |
This has always kind of mystified me. Is "multitasking" a misnomer (as in singing and playing the guitar at the same time)? Or does that limitation of concentration only apply to certain parts of the brain (e.g. paying attention to two people speaking at once)? I wasn't sure whether to post this in askscience or askreddit, but I figured I'd get more of the answer I'm looking for here.
|
[
"Layman's thoughts:",
"The human brain is MASSIVELY parallel. At any given moment, you brain is carrying out hundreds processes, if not more (respiration, digestion, heart beat, etc.). Some you're aware of, some you're not. So, in that sense, you're always multitasking.",
"If you're referring to focusing your higher brain on more than one subject at a time, that's a different situation. However, the same thing still occurs. When you're thinking about anything, your brain is simultaneously searching through multiple parts of your memory concurrently as well as assessing the relevance of those memories in real time. So, you're definitely multitasking when you think about something.",
"If you go up another level, this multitasking still happens. For example, you can stir pasta with one hand and type a text with the other hand without thinking twice. This is not only dumping two entirely unrelated tasks on the motor cortex, it's also taxing the creative and language areas of the brain to compose the text.",
"There are definitely exceptions, though. You'd be pretty hard-pressed to find someone who could do multiple math problems at once. I guess that's just because we never needed that. Or maybe we just never had it in the gene pool.",
"The brain is cool."
] |
[
"StackOverflowException thrown\n"
] |
[
"In fact, filtering things out is what your brain does really well. This filtering mechanism is what's 'broken' in autistic kids (I have two) and means that their brains are overloaded all the time with too much information and it makes it hard for them to be touched (too much stimulus), be around others (too much audio stimulus), and a host of other problems related. It makes things very difficult to learn for them.",
"The best thinkers in history have tremendous concentration and focus. This is because all of their filters are working optimally."
] |
[
"How is glucose actually made in plants?"
] |
[
false
] |
From what i know, one of the products of photosynthesis is glucose but im still confused on how the plant actually makes the glucose. I have read about the calvin cycle but im still having trouble understanding how G3P is turned into glucose.
|
[
"The G3P produced from carbon fixation during the Calvin cycle can be used to produce glucose though a pathway called gluconeogenesis. It's actually a pathway we too are able to use. It's essentially a reverse of glycolysis, including many of the same enzymes. The main differences are a few points in the pathway (the \"irreversible\" steps in glycolysis) that require energy input and different enzymes than glycolysis."
] |
[
"After a portion of the glyceraldehyde-3-phosphate pool from photosynthesis is exported from the chloroplast to the cytosol, two molecules are combined to make one molecule of fructose 1,6-bisphosphate. This reaction occurs rapidly in both directions, but FBP is then dephosphorylated to fructose-6-phosphate, which is essentially a one-way reaction that sequesters the fixed carbon to the 6-carbon sugar pool. The main forms of non-structural carbohydrate storage in plants are sucrose (a disaccharide of glucose and fructose) and starch (a polysaccharide of glucose monomers), so part of the F6P pool is converted to glucose, then further partitioned into ADP-glucose for making starch and UDP-glucose for making sucrose, and part is combined with that UDP-glucose to make sucrose. And finally, both the FBP and F6P forms of fructose are intermediates in glycolysis, so they can be used directly for energy production."
] |
[
"The G3P produced from carbon fixation during the Calvin cycle can be used to produce glucose though a pathway called gluconeogenesis",
"This is a semantic point, but gluconeogenesis is the production of glucose from non-carbohydrate precursors. The conversion of G3P to F1,6BP is not a gluconeogenic process, and the subsequent conversion to glucose only uses the last two gluconeogenic enzymes. Unlike glycolysis and gluconeogenesis, no redox reactions occur, and no ATP is used or consumed."
] |
[
"Question about Galvanic Corrosion, Do the metals need to touch?"
] |
[
false
] |
From everything I have read about galvanic corrosion it always states 3 main things need to occur, 1. Dissimilar Metals 2. Exposure to an electrolyte 3. Direct contact between the metals. My question comes in on the 3rd point about direct contact. Say I have Stainless Steel 304, and 6061-T6 aluminum in a salt bath very close to one another, but not touching, does this mean that galvanic corrosion will not occur? Wouldn't the impurities in the salt water act as a conductor between the 2? Or do I have to have them touch each other, or via a wire? Thanks for your input, it’s been bothering me now for a while!
|
[
"Yes they need to touch, or you need to run some kind of electrical conductor from one to the other (that is not the electrolyte). The process works as a cycle, ions travel from one metal to the other one way through the electrolyte and the charges are balanced out by electrons traveling through the electric connection. If you remove the path for the electrons then you remove the ability for ion migration and the corrosion to happen."
] |
[
"That could be true, as long as there is a second path that can transfer electrons then corrosion has the chance of happening. I'm honestly not sure if air would make this possible though, to the best of my knowledge you need a couple orders of magnitude more voltage than you get from any two dissimilar metals. Unfortunately I don't have the actual expertise to say one way or the other but if you have any sources that say this is possible or not you should share them."
] |
[
"The electrolyte acts as one \"wire\". If there's not another path to complete the circuit, you get local static potential, and not a potential gradient — you get a traffic jam. The electrolyte will \"wedge in\" to any \"gaps\" unless physically restrained. Making a separate wire allows electrons to flow and breaks the traffic jam."
] |
[
"Does an aircraft throttling up aboard an aircraft carrier while strapped to a catapult increase the carriers velocity?"
] |
[
false
] | null |
[
"The throttling up does nothing...",
"The plane is clamped down and the engine is throttled up to high. The catapult assists the acceleration, it doesn't do all the work. The plane's engines would impart a small acceleration ship, but it would be like a bottle rocket taped to your car due to the massive size of the aircraft carrier."
] |
[
"Technically, yes. Is it significant? No, not really. Average weight of a supercarrier is about 70000 tons. Max thrust of an F15 is about 48000 lbf, so about a 1 to 3000 weight difference. About like a fly pushing on you. "
] |
[
"Yes, and it has been used to move carriers. In the 1950's the Navy occasionally used propellor driven planes pointed sideways to help turn carriers in tight quarters. It was called a pinwheel maneuver. The pilots and maintenance folks hated it because it was a severe strain on the engines. ",
"Edit: ",
"source"
] |
[
"Plastic Material for Rail Covers"
] |
[
false
] |
Hello , I am part of a group of students who were assigned to work on a hypothetical device to cover train tracks when they are not in use. The train tracks would be activated using electromagnets that will push the covers (located on either side of a single rail) closed when a train is not in close proximity. Seeing as they must be opened by electromagnets the material cannot be very heavy. And since they will be used for many miles the material has to be quite cheap, though we are only making a model. Basically what materials would make good rail covers in this situation? So far the only material I have chosen as an option is thin sheets of carbon steel, as it is the same material the tracks themselves are made from. However I wanted to consider a plastic as well, is there any specific plastic materials that you believe would be good for the job? Thank you in advance, TheScienceFan
|
[
"standard ABS generally doesn't stand up that well to exposure either - But you can get it made with additives that will help that. An ultra-high molecular weight PE should also be acceptable. You're going to be replacing the plastic components every few years regardless due to simple wear and erosion.",
"Has anyone considered fitting brushes to the front of the train itself to sweep the leaves away? This system seems gratuitously expensive for what should be a simple problem. It might even be cheaper in the long run to build a canopy over the tracks."
] |
[
"It is very expensive for such a problem, but unfortunately the leaves are wet and contain a sap-like liquid that makes the very sticky. When they stick on to the rail they cannot merely be brushed aside. Strong, perhaps wire brushes could be used, though these could scratch the rail, and if too strong could even cause rolling contact fatigue.",
"Sanding is pretty effective, but unfortunately it's not effective enough. This is quite hypothetical, personally I think erecting fences or nets would be more efficient and cost-effective."
] |
[
"What is the goal? To prevent corrosion of the rails?",
"If that's the case, you'd have to choose a metal lower than carbon steel on the ",
"galvanic series",
" in order to have the covers corrode preferentially to the rails. Given that the covers will corrode anyway, I fail to see the purpose of such a device.",
"You could use sheets of lucite (polycarbonate) or PVC, Most other plastics like Polyethylene or Polypropylene will decay pretty rapidly due to UV exposure. ",
"Given the mechanical and electrical complexity of a system which has to open and close a series of covers electromagnetically each time a train passes in order to mitigate the cost of occasionally replacing rails... I don't see the point."
] |
[
"Will the universe eventually decay into particles smaller than protons?"
] |
[
false
] |
I heard somewhere that protons do decay into quarks, but it takes longer than the universe has been in existence. Is there any truth to this? Given enough time, will there no longer be atoms?
|
[
"Proton decay has never been observed. There's at least one good theoretical reason to believe it cannot occur: baryon-number conservation. A proton is the lowest-energy baryon, so it's got nothing to decay ",
" It's already at the bottom of the hill.",
"But it's already known that baryon number isn't exactly conserved, so it's not a sure thing that protons are stable. It's possible to imagine some decay mode that turns a quark into a lepton, giving you something like a neutral pi meson and an antielectron plus a lot of momentum, something like that. But the lower bound on mean lifetime is on the order of 10",
" years or something like that — recalling that the universe is only 10",
" years old. So if protons ",
" decay in one of those modes, and that ",
" a valid mean lifetime estimate, then it's entirely reasonable that we may never observe it in the lifespan of our species."
] |
[
"What they mean by that is that if protons decay, they decay so slowly that we haven't been unable to detect any decays yet. They did an experiment to measure proton decay, and observed nothing, which proved wrong a model called Georgi-Glashow theory.",
"It wasn't until 2003 that we knew that Bismuth decayed; experiments showed that it had a half life of about 20 billion years."
] |
[
"From earlier today",
".",
"Also, quarks can't exist independently. They're always bound into particles with others. "
] |
[
"What does a \"star\" look like in the moments before it achieves fusion?"
] |
[
false
] | null |
[
"Stars are quite bright before the onset of fusion, due to the release of gravitational energy. They collapse from vast, rarefied molecular clouds in the interstellar medium when a density perturbation grows enough to induce ",
"free-fall",
". As they collapse, the gas particles heat up , increasing the gas pressure and causing the star to glow. When this pressure gets large enough to balance the gravitational pull, the star halts its collapse. However, the gas is hot and will emit light. As this light comes out, the star slowly cools and collapses further and further. This causes the central regions of the star to heat up, eventually becoming hot enough to fuse hydrogen.",
"So what does it look like? For an early star with the same mass as our sun, it will be quite bright, and will have a circum-stellar disc. Like this: ",
"http://mail.colonial.net/~hkaiter/astronomyimagesB/Protostar.jpg"
] |
[
"So how bright (magnitude) would the protostar appear in our sky if it were to take the sun's place?"
] |
[
"There would be little visual evidence of the moment that the first atoms begin fusing. Once fusion starts however, the star's internal structure rearranges: there is a different equilibrium state of the sun when you're heated by a core compared to the state when you're heated by contraction. You will see gradual changes in the surface luminosity as the star settles to hydrogen burning equilibrium (called the main sequence), but no sudden wave."
] |
[
"Would Mars be considered to be in \"Habital Zone\"?"
] |
[
false
] | null |
[
"Mars is considered to be just outside the habitable zone for our star",
"http://en.wikipedia.org/wiki/Habitable_zone",
"http://upload.wikimedia.org/wikipedia/commons/6/61/Habitable_zone_-_HZ.png",
"http://en.wikipedia.org/wiki/File:Estimated_extent_of_the_Solar_Systems_habitable_zone.png"
] |
[
"sure, with enough engineering and science anything is likely quite possible. "
] |
[
"Yeah, it seems that the atmosphere came from a runaway greenhouse effect, so perhaps a slightly more distant location, where the water could have remained liquid would have significantly aided Venus' development."
] |
[
"What would happen if you separated a fertilized human egg cell right after it split for the first time?"
] |
[
false
] | null |
[
"Does that mean you could do this infinitely?",
"For example, you take one cell from the original, then it splits and begins to make its own baby, you take one of those cells and do the same. Could this go on forever?"
] |
[
"Does that mean you could do this infinitely?",
"For example, you take one cell from the original, then it splits and begins to make its own baby, you take one of those cells and do the same. Could this go on forever?"
] |
[
"Yeah but only by a few hours or so which is basically nothing on the timescale of an entire pregnancy. "
] |
[
"How does music get burned onto a CD?"
] |
[
false
] |
The most I could find about this from researching on my own is that the sound gets translated into a binary code, which then gets "transcribed onto the cd." But what does this mean; is it actually microscopically etched onto the disc? Also, the place that I found the above information was yahoo answers, so I don't know how accurate it is. Edit: Thanks for the answers, everybody! Super informative, I appreciate it.
|
[
"At a high level, the audio is encoded using ",
"Pulse Code Modulation (PCM)",
". First you have to believe that anything we hear can be represented by a wave form (actually two wave forms in the case of a CD, because it stores both a left and right channel). PCM takes that wave form and chops it up into a bunch of different slices (44100 slices per second of audio, for CD audio). For each one of those slices, you store the y value of the wave form at that slice point (for CD audio, it stores a number in binary between -32768 and +32767). That's all you need to do to store digital audio!",
"To make CDs resistant to superficial scratches, the encoded audio is stored with some redundancy, specifically ",
"Reed Solomon error correction codes",
". For every 224 bits of audio data, 256 bits are actually written to the CD, to provide some redundancy. If some data cannot be read (because of a scratch on the CD), but enough redundant data can be read, your CD player will be able to reconstruct the missing data and play it back without you noticing anything's wrong.",
"As for the physical encoding of the data, that depends on whether your CD is pressed or \"burned\". Pressed CDs, like the ones people used to buy at record stores, have pits physically etched into the surface of the CD. The idea is that when a laser is shone onto the surface of the CD, the pits will not reflect the laser back. If light is reflected back, that's taken as a 0; if light is not reflected back, that's taken as a 1 (maybe I have this backwards).",
"For burned CDs, the kind you create on your PC at home, the CD burner is not physically etching anything. Rather, the surface of a CD-R is covered in a translucent dye. During burning, a high-powered laser is used to heat the dye so that it becomes dark and opaque, in certain spots. The end result should be effectively the same as a pressed CD: instead of pits we now have dark spots, but in either case, we have spots which either reflect laser light or don't reflect laser light, giving us our physical encoding of 0 and 1."
] |
[
"A minor correction, from ",
"wikipedia",
": ",
"The pits and lands themselves do not directly represent the zeros and ones of binary data. Instead, non-return-to-zero, inverted encoding is used: a change from pit to land or land to pit indicates a one, while no change indicates a series of zeros."
] |
[
"Interesting!"
] |
[
"Does a (solid shell type) Dyson Sphere have to rotate?"
] |
[
false
] | null |
[
"Astronomy"
] |
[
"Astronomy"
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"It is hypothetical or speculative in nature. We do not allow hypothetical questions because questions that cannot be confidently answered with any available data often invite non-scientific speculation. For more information regarding this and similar issues, please see our ",
"guidelines.",
"A good home for this question is our sister subreddit ",
"/r/AskScienceDiscussion",
" because of its open-ended or speculative nature. Please feel free to repost there!",
"Please see our ",
"guidelines",
".",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"What natural light would someone on the dark side of the moon experience, if any?"
] |
[
false
] |
Except for stars and other celestial objects. That's a given.
|
[
"What did you mean by the \"dark side of the moon\"? ",
"It can refer to two things:",
"The moon is ",
"tidally locked",
" to the earth. So it's only one side of the moon that faces the earth. We sometimes refer to the other side (the side that always faces the other side from the earth) as the \"dark side of the moon\", in reality it's better to refer to it as the ",
"far side of the moon",
".",
"If that's what you meant by \"dark side of the moon\", then the answer is that it gets about as much sun light as the side that's always facing the earth."
] |
[
"Just to clarify: the moon does ",
" pass through the Earth's shadow during every orbit. The orbit of the Moon is inclined with respect to the plane of the Earth and Sun (the ecliptic), by about 5 degree, which is usually enough to prevent the Moon from passing through the shadow.",
"Still, ",
"lunar eclipses",
" can occur during some geometries (when the Moon is both full, and passing through/near the line of nodes). Since this shadow does falls on the near side, your point that the far side receives slightly more sunlight is technically true. I just wanted to clarify that this shadowing isn't an extremely common occurrence."
] |
[
"Considering the Earth's shadow when it's between the Moon and the Sun the far side of the Moon gets slightly more sunlight than the Earth side does."
] |
[
"The halting problem as applied to the much sought after \"theory of everything\""
] |
[
false
] |
Sir Roger Penrose came to speak at my university today; in between the informal Q&A session and my preparatory reading up on his work, my mind wandered and I had an interesting thought. I'm not well acquainted with the topics relevant to this thought, so I welcome corrections. In any case, I'd be interested to hear opinions. Suppose that the entire state of the universe can be described at any point in time (this must be true; the universe itself is that description). Suppose that there is some system of rules or laws P (a "theory of everything") according to which the universe's state evolves. Suppose that we know P. A natural question would be, "according to P, will the universe end?" P could not possibly conclude that the universe will end; the end of the universe implies the end of any evolving state/program/&c and therefore P will be able to tell whether any evolving state would halt, and this would contradict the uncomputability of the halting problem. Therefore, either P will conclude that the universe will never end, or there is no such P, in which case we can't know whether the universe will end. I'm sure that I have an incomplete understanding of some of what I'm talking about and/or I have misformulated something. I haven't even really thought this through; I'm in a lecture right now. Thoughts?
|
[
"I don't see how that is relevant. "
] |
[
"I don't see how that is relevant. "
] |
[
"Collapse, everything getting sucked into one black hole, whatever you like. I'm afraid you'll have to explain to me how thus is relevant."
] |
[
"Could some diseases be eliminated through extreme quarantine?"
] |
[
false
] |
I may not understand how this works but my understanding is that for some diseases to exsist someone has to have it all the time. So if there was a disease that lasted about 2 weeks in a person and then could last for about 1 week on a surface could that disease be eliminated if each person in the world was quarantined for 4 weeks? I understand this would not be a feasible solution, I was just wondering.
|
[
"Sounds good in theory, as long as the disease didn't have some other reservoir. The term people often use for this is \"social distancing\"."
] |
[
"As mentioned, natural reservoirs can maintain a pathogen's existence outside the host, sometimes in a dormant or spore state. Many pathogens can act this way, and thus do not require at least one person to be sick all the time. "
] |
[
"I did some \"back of the envelope\" math on this. ",
"Earth has 148,940,000 square kilometers, divide that by 7 billion people and you get about 0.0213 square kilometers per person or about 5 acres. Possibly more since you wouldn't want to isolate infants or toddlers for that time. But yeah, this is not feasible."
] |
[
"Is The Universe The Same Age Everywhere?"
] |
[
false
] |
I tried asking this question before and got shot down and dismissed with some nasty comments. I think it may have been that I either didn't explain myself well enough or give a good example. I think I came across a good example that would explain what I'm getting at quickly and concisely. In the movie there was a planet they named "Miller's Planet" which was a water world that was in a stable orbit very close to the supermassive black hole they named . When they went down to that planet and then returned to their main ship, while only a few hours had passed for them, something like 23 years (I may be wrong about how many years) had passed at their main ship. This was because of the warp in space-time caused by Gargantua. Now, supposing that Miller's Planet had been in orbit around Gargantua for quite a while, say something like how long Earth has been around, 4.5 billion years, would the age of the universe be the same to a civilization that arose on a planet like Miller's as it is to us here on Earth? Which brings about the more fundamental question: is the universe the same age everywhere, if you were able to somehow take a consensus of numerous places in the universe simultaneously? Could other factors, such as space being created the universe, compress or stretch time so as to make notable differences in whole regions of the universe?
|
[
"A hypothetical story that might help:",
"Say we meet in a parking lot somewhere, and decide to agree the universe is X seconds old. We then walk off in opposite directions. We each carry atomic clocks with us. I climb a mountain for a week and bring my clock with me. You go on a vacation to the beach, and bring your clock with you. Then we meet up in the parking lot again. Now, our clocks disagree by a few nanoseconds. We can't agree on the age of the universe anymore.",
"This experiment has been done, and it works. ",
"https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment"
] |
[
"No, you never see your own clock change speed. You always experience 1 second as 1 second, and the world around you experiences time at a different rate.",
"The classic example is the twin paradox, if your twin stays on earth and you fly off at close to the speed of light, you might come back 10 years later to find that 50 years have passed since you left. So you will live longer than those people, but you won't live to be an older age or experience more time over the course of your life as you otherwise would."
] |
[
"No, you never see your own clock change speed. You always experience 1 second as 1 second, and the world around you experiences time at a different rate.",
"The classic example is the twin paradox, if your twin stays on earth and you fly off at close to the speed of light, you might come back 10 years later to find that 50 years have passed since you left. So you will live longer than those people, but you won't live to be an older age or experience more time over the course of your life as you otherwise would."
] |
[
"What are the physical, gravitational, resource, or magnetic limits on the size of a rail gun?"
] |
[
false
] |
[deleted]
|
[
"We have physical limits: no material is infinitely strong.",
"Stress is defined as force divided by cross-section area. The weight force is proportional to volume (assuming constant density and uniform shape), which is equal to cross-section area times length. The area cancels out in the division showing that stress is proportional to length.",
"Therefore, if the columns supporting your rail gun are tall enough to exceed the ",
"ultimate tensile strength",
" of their material then they are doomed to collapse under their own weight. This concept is known as \"length to rupture\", \"breaking length\" or ",
"specific strength",
". In the case of steel the (theoretical) maximum height of a uniform column could be 25 km. (Of course the actual number will be smaller in practice, especially if it is supporting a heavy rail gun on top of it)."
] |
[
"Further: would a coil gun be preferable?",
"First, contrary to what ",
"/u/katinla",
" said, a coil gun still experiences repulsive forces from its magnetic field. The field attempts to expand the coil. One of my undergraduate workshop problems was to figure out the force on a giant superconducting solenoid for grid-level storage; the force on the solenoid would have blown it apart. ",
"Second, a coil gun would not be better, because it needs to be switched on and off at very high speed. That's the kind of problem that gives power engineers nightmares. Or wet dreams. I'm not really sure. Anyway, its almost definitely probably way harder than making a railgun maybe."
] |
[
"It depends on your purposes. If you just want to shoot a projectile to a target it needn't be tall. If you want to launch an aircraft, missile or satellite, then you'll have to point upwards, and if the projectile can't withstand a very high acceleration then it has to be a big, long gun to reach the required speed."
] |
[
"Besides temperature, how would the density of air increase?"
] |
[
false
] | null |
[
"Sure, if you are putting in more molecules then the mass necessarily needs to go up, and if you constrain the volume of the cube then the density must increase. The pressure will go up (at constant T). ",
"We do this practically all the time when doing things like filling bike/car tires, you push in some air with the pump and the the tire will actually get heavier without changing volume much. Generally we look at the pressure change and ignore density as air isn't very massive even under a few atmospheres of pressure, but it happens all the same."
] |
[
"Taking this one step further.. in physical laws, if temperature increases, the density must decrease, since they are inversely proportional to one another. What would happen though if the case you just stated happened, but the temperature increased as well? This means we would have to nullify the laws of physics that we know, I understand, but could it be possible?"
] |
[
"The pressure would increase to balance things out assuming volume remains fixed."
] |
[
"Do fat people have more blood?"
] |
[
false
] | null |
[
"What kind of assumption or logic did you follow to ask such question?",
"Adult humans who have not recent experienced major loss of blood have between 4.7 and 5 litres of blood with females usually on the lower side of that range and males on the higher.",
"If you though that increased mass due to fatty tissue would cause increased need for blood that is not the case because when person gains weight no new fat cells are created, instead existing fat cells increase in size. Same goes for the muscles. Bodybuilders don't have more muscle cells than ordinary people, it is just that their cells are bigger."
] |
[
"thanks, i was watching walking dead, and when they had to do the blood transfusion, i thought that maybe a bigger guys would have more blood, obviously they don't. Kind of amazing that the same 5L of blood that powers a 150lb man powers a 350lb man..."
] |
[
"See ",
"here",
"."
] |
[
"Was there ever a time in the history of the earth where if an intelligent civilization had arisen and self-destructed, we would now see no evidence in the fossil record?"
] |
[
false
] |
I was wondering if some animal could have developed intelligence and produced civilizations. For instance, as far as I know the utah raptor could have evolved opposable thumbs, but since fossils are rare, we don't see such evidence in the fossil record. My immediate thought is that we could identify mineral anomalies, areas with abnormally large proportions of rare earth metals marking quarries or cities. Although fossilization is rare, perhaps it would be inevitable that something strange or mechanical survives. Self-destructive civilizations also give an interesting alternative explanation for mass extinction events. Some food for thought for the science fiction writers out here. EDIT: Hey folks, thanks for your comments. I see some fascinating responses.
|
[
"Personally from my studies of geologic processes, if the society was on an area of a tectonic plate that was subducting under another tectonic plate and the rate of motion was such that by present day the entire section where the civilization existed would be buried so deep that the heat and pressure would cause everything to melt then yes it is possible to have no evidence of the civilization. Keep in mind that most plates move on average 2-8cm a year. "
] |
[
"Looking first at the evolutionary line of Homo sapiens - realistically, no. Given the age of the archaeological records that we have for the Palaeolithic, and the fossil record we have for human evolution, it's difficult to identify a period where such a civilisation might have developed, flourished, and collapsed, without some evidence being found. You also need to remember, that while fossilisation of bones requires very precise conditions, one would expect that the material evidence for such a civilisation would be far more easily preserved than organic materials (such as bones).",
"Moving away from my own area of knowledge (i.e. archaeology), to consider the idea of another vertebrate species reaching sentience and developing complex societies; I would also think it unlikely from a biological point of view. In terms of evolution, you're talking about an entire species, and the evidence of that species' evolutionary line, becoming extinct with no record their existence surviving. Even in the most extreme self-annihilation scenarios imaginable, some people (Homo sapiens) would survive - even where their complex societies/civilisations did not. Although (obviously) lots of species have developed and become extinct, and presumably some have not survived in the fossil record, for such an evolutionary development to occur, on a scale large enough to develop a complex society, with no fossil record would be extraordinarily unlikely.",
"edit: I should say, the one manner in which I could see such a hypothesis being viable, would be if it were somehow confined to a very precise location that is now unreachable - such as Antarctica. Still incredibly unlikely, but I suppose it's not impossible "
] |
[
"Civilizations primarily form adjacent to water. This civilization could now be miles out into the ocean under many layers of silt."
] |
[
"Where does pee from your kidneys go when your bladder is completely full and hasn't been relieved?"
] |
[
false
] | null |
[
"Where does the sewage in your house go if there’s a blockage? It backs up into your house and makes a mess. Same with the kidneys. If there is something preventing your bladder from emptying, it will back up into your kidneys. It’s called hydronephrosis. ",
"hydronephrosis."
] |
[
"To add to this, in most healthy people the bladder can stretch quite a bit (up to a liter in some people). Urinary leakage can occur when the body's ability to keep the urinary sphincter closed is overcome by how full the bladder is. The body would much prefer embarrassing urine leaks than backing urine up into the kidney (which can cause kidney damage). ",
"Hydronephrosis/hydroureter more likely happens in people who cannot empty their bladders. For example in the event of nerve damage in the pelvic area or if there's a physical block with outflow as with a kidney stone."
] |
[
"I drink lots of black ice tea while working very focused on the computer half the night. While being distracted, you can easily ignore the short occasionally urge. Result is stretching of the bladder to ~1.25 liters until eventually you feel light pain in the kidneys telling you to finally take a toilet break.",
"Heaving a bursting full bladder does not trigger the urinary sphincter in the slightest way for me, you rather have a hard time applying pressure. I guess heavy laughing or fear of death is much more efficient in that regard :)",
"Never had any issues with it and am often perplexed when people go to the toilet every half an hour when drinking alcohol."
] |
[
"Does the acceleration due to gravity effect the frequency of a pendulum?"
] |
[
false
] |
I got into an debate with my physics professor about the effect of gravity on a simple pendulum. She claimed that gravity had no effect on the frequency, and only the length of the string suspending it. My response was that the motion of a pendulum is caused by the force of gravity pulling the object down towards the fulcrum, and that a pendulum in the absence of gravity would have a frequency of 0 since no force would be causing it to oscillate back and forth. It states in my textbook that the period of the pendulum depends on the acceleration of gravity, and the frequency is calculated by the equation 1/period, so my question is, how can frequency not depend on the acceleration due to gravity if the period does?
|
[
"Are you sure that is what your professor said? Your intuition is correct, as the ",
"frequency",
" (1/period) of a pendulum does depend on the gravitational acceleration. Perhaps she was talking about a different kind of pendulum, such as a pendulum that is constrained to move completely perpendicular to the direction of gravity."
] |
[
"Perhaps she meant that the weight or mass has no effect on the frequency?"
] |
[
"The question was ",
"\"The frequency of a pendulum depends on\"\na)Its mass",
"b)Its length",
"c)the acceleration due to gravity",
"d)all of these",
"e)two of these",
"I chose \"e\" and got it wrong. It was a poorly worded question in my opinion."
] |
[
"Coke VS Diet Coke VS Coke Zero. Let's settle this once and for all. Why exactly shouldn't we drink carbonated beverages, and what is the difference between these products?"
] |
[
false
] | null |
[
"I have to point out a few things, first. You guys just seem to be throwing out \"right\" and \"wrong\" without giving any reason or solid science. Let's deal with his own adult decision to drink diet Coke, and see how the health affects compare to regular Coke. ",
"Let's first look at the ingredients. ",
"Coke: Carbonated Water, ",
", Caramel Color, Phosphoric Acid, Natural Flavors and Caffeine. ",
"Diet Coke: Carbonated Water, Caramel Color, ",
", Phosphoric Acid, ",
", Natural Flavors, ",
", and Caffeine.",
"The bolded ingredients are the ones unique to either soda, but we won't talk about them all. The ingredients that are hot topic issues for the public are High Fructose Corn Syrup and aspartame. ",
"High Fructose Corn Syrup",
" is just a mixture of the most simple of sugars, fructose and glucose, and occur naturally in our diets. The issue with HFCS is that it's everywhere and in gratuitous amounts. Too much sugar == bad for the body, as most people know.",
"Aspartame",
" is a bit different. It's an artificial sweetener, and it's really gotten a bad rep. What data I can give you is that aspartame has been ",
"one of the most widely tested food additives since the 1970's",
", and it's been deemed safe over and over again. It is okay to drink in regular quantities. ",
"As far as caffeine goes, it depends on the person and their health at the moment, but IIRC if you stay within 200~300 mg or less a day, the average person will be fine [citation needed].",
"The biggest thing you have to worry about regarding Diet Soda is its acidity and how it can affect a person's teeth. As a side note, caffeine in soda was once considered a diuretic (something that dehydrates you), but the effects have been exaggerated and have since been corrected.",
"Now, I recall coming across an interesting paper on EBSCO Host about how drinkers of diet soda still have a higher chance of being obese. ",
"Here's",
" something that can explain it, but both of these sources admit that ",
". There is no conclusion stating that diet sodas themselves cause this trend; one idea is that people think to themselves, \"I'm saving all of these calories, so I can eat that entire package of Oreos!\"",
"So, personally? Where the data has lead me, and mind you this is ",
", diet soda is a better substitute so long as your teeth and caffeine consumption is good. You're not taking in the HFCS, and you are saving calories. ",
"If you want me to cite more sources, I can. That's all I have to say."
] |
[
"I'd be interested to read more on this teeth and acidity problem. Any references you can share?"
] |
[
"O. Sollböhmer, K.-P. May, M. Anders. \"Force microscopical investigation of human teeth in liquids\". Thin Solid Films. Volume 264, Issue 2, 15 August 1995, Pages 176–183",
"http://ge.tt/6H1NwXJ/v/0",
"No significant difference in material loss between sugar-free and traditional soda pops."
] |
[
"Could a loud outdoor concert create the necessary air turbulence for water droplets to coalesce and fall as rain?"
] |
[
false
] |
I was at Soundgarden concert in Toronto, standing in the rain, when the question was asked of me. According to the Wikipedia entry for : When air turbulence occurs, water droplets collide, producing larger droplets. As these larger water droplets descend, coalescence continues, so that drops become heavy enough to overcome air resistance and fall as rain. So, could a loud outdoor concert create the necessary air turbulence for water droplets to coalesce and fall as rain? Just to be clear, the situation I am asking about already has the necessary weather conditions for rain, it just hasn't coalesced enough for rain to fall.
|
[
"I don't think so. Are you talking about the vibrations in the air due to the volume of the sound at the concert vibrating the droplets in the air to move them around? Falling rain and drop coalescence is just the result of lots of air droplets colliding in the convection currents within a cloud. It's not really a matter of turbulence caused by something else, although the mixing within the cloud helps to get droplets to coalesce, and it's mainly a matter of the dew point.\nAlso, if there are suitable conditions for rain droplets to form at the altitude where the concert could have any effect on air turbulence at all, then it would have already been raining many meters above in that area where clouds form because it would be colder up there and more favorable for condensation. So the concert would have no effect on the weather, which originates many hundreds of meters above it.",
"I suppose if the concert was throwing up tiny particles of something in celebration, these hygroscopic nuclei would go into the air around the concert and \"seed\" that air to make it more favorable for droplet development without re-evaporation."
] |
[
"Theoretically it could if the conditions where right:",
"In terms of weather at ground level they would most likely be close to 100% humidity and 0 degrees C. Not ideal for an outdoor concert.",
"However using loudspeakers for cloud-seeding would be very inefficient, as speakers are very inefficient in transfering energy and the mechanical energy drops quadratically."
] |
[
"Not a scientist, but this is somewhat related and interesting: ",
"http://news.nationalgeographic.com/news/2010/06/100616-planes-change-weather-hole-punch-clouds-science/"
] |
[
"I am told it takes days to digest food. Why is it then that certain foods cause near instant reactions in the... digestion? I.e. spicy food emergencies, asparagus smell etc.?"
] |
[
false
] | null |
[
"The whole digestive process takes between 24 and 72 hours, but the digestive system is somewhat complicated, and not all foods and nutrients are digested at the same speed. Liquids generally are processed quicker than solids to take an example. You will also have noticed that alcohol certainly enters your blood stream much quicker than 72 hours, and once there it affects every cell in your body. The same is true for many medicines. ",
"Essentially the time it takes for things you digest to affect you depends very much on where in your digestive system it is absorbed or has an effect. Anti-acid medication can have a nearly instant effect when it enters the stomach. Absorption into the small intestine necessarily happens before absorption in the colon, as the former is position before the latter in the digestive system. ",
"Once a compound is in your blood it can spread through your body very rapidly. This is why intravenous injections can have so rapid effects. The medicine is carried with the blood throughout the body within seconds. "
] |
[
"Another question. When I eat I feel full immediately and I feel that my bloodsugar rises. However the times I have puked after eating all my food is still fairly undigested in my stomach. Why did I feel full and with a replenished bloodsugar level."
] |
[
"There is a lot going on with fullness that is related not to how much food you have eaten but to specific hormones such as leptin that make you feel full or satiated. Also, the feeling of \"fullness\" could simply be your stomach being full of food, it doesn't necessitate any digestion. "
] |
[
"Why did the Saturn V rocket only go to the moon, but Space X's smaller thrust rocket will go to Mars?"
] |
[
false
] |
I don't get how the Saturn V with it's nearly 8 million pounds of thrust only went to the moon and the Raptor with Space X is planning to go to Mars which according to Google is 33.9 million miles away compared to 250,000... Sure... you would just use gravity slingshotting... right? Is it something like, the heavier something is, the more thrust you need at first to get off Earth... The Mars thing from Space X is smaller than Saturn V payload?
|
[
"Rockets are complicated.",
"Saturn V is a three-stage rocket with 7.8 Mlbs, 1.2 Mlbs, and 0.2 Mlbs thrust. All three stages are used to insert into earth orbit with a significant amount of fuel left over for injecting into a trans-lunar orbit.",
"The SpaceX mars spacecraft is a two stage rocket with 29 to 31 Mlbs for the first stage and 7 Mlbs for the second stage. The second stage fuel is entirely used getting into earth orbit and then refilled in orbit before burning to get into a trans-martian orbit.",
"Points to answer your question:"
] |
[
"The Spacex stack is only more efficient than the first Saturn V stage. The second and third stages burned hydrogen in their J-2 engines which had better ISP than spacex's Raptors will have."
] |
[
"Holy crap. This is true? That moon rocket by the Russians had almost 10 million with 30 engines. Granted smaller. Not successful either due to complexity but. Yeah when I saw some videos I thought the thrust was significantly less. It was compared to the Space Shuttle main engines something like ~500,000lbs. I'll have to look at the plans again or something."
] |
[
"If a strand of hair starts growing gray, will that specific hair follicle only produce gray hairs in the future?"
] |
[
false
] | null |
[
"So, if a strand of hair starts growing gray, will that specific hair follicle only produce gray hairs in the future?"
] |
[
"So, if a strand of hair starts growing gray, will that specific hair follicle only produce gray hairs in the future?"
] |
[
"Dear AskScience denizens: anecdotes are not allowed and will be removed. Answers need to be based on peer-reviewed scientific research. ",
"Please read the sidebar and ",
"our guidelines",
" for more information."
] |
[
"Can we see what our genetic potential for different activities are?"
] |
[
false
] |
I was reading a quote from a book about rock climbers, With regard to tendon insertions, a slight shift in the location compared with normal provides additional leverage that gives a few lucky folks more grip strength (off the couch!) than others could achieve through years of training. Similarly, your innate ratio of fast-twitch to slow-twitch muscle fiber determines whether your natural aptitude tends toward high endurance, high strength, or neither. Finally, we each have unique hormone profiles (testosterone, cortisol, and so forth) that vary with age and sex, and this plays an underlying role in our response to training and recovery ability. And I was wondering If we actually have a way to test out these specific things and others, as well as maybe read DNA to see what activities a person is best at. I don't want to go throughout my entire life not knowing that I have the potential to become a great martial artist, or professional whatever, and that my brain works in a certain way that If I study or engage myself in a certain way I could have retained all information 33% better or that I could have the mental processes of a great inventor/theorist. You would think that in today's day and age you could go into a medical office or psychologist or neurologist or whatever and be tested for aptitude in different areas to help you reach your maximum potential.
|
[
"It's a long story, but no. We can't. At least not now. ",
"We only know what a fraction of the genome actually means in terms of phenotype (the visible manifestation of what your genome says you should be like.). ",
"However, the bigger issue is that phenotype is also significantly influenced by our environment. Grow up in a house hold that doesn't consume much sugar, and you'll have a dramatically reduced likelihood of obesity. Grow up in a house full of expert chess players, you'll have a better chance at becoming a grand master. ",
"Our genomes are very plastic, and your aptitude for a particular subject or skill may be equally environmental, as much as genomic. "
] |
[
"For a new question based on your comment, I hear all the time that our phenotype is significantly influenced by our environment, but is this only in development as a kid?",
"If from 0-21 years old you never played chess you would probably have a horrible chance of having the mind structure to be a chess master. ",
"But what if you started at 21 and played chess constantly for 5 years. Would that increase my chances of having the mind structure to be a chess master as much as it would if I spent 5 years in my developmental period as a kid? "
] |
[
"I don't think we can make those kinds of extrapolations yet - we're still really early on in understanding the mechanisms of how our genomics are modified by environment (mainly epigenetics, at this point), so it's next to impossible for me to comment on that."
] |
[
"How much of the sunlight, emitted from its birth untill now, is still travelling?"
] |
[
false
] |
How much of the sunlight, emitted from its birth untill now, is still travelling?
|
[
"How much of the sunlight, emitted from its birth untill now, is still travelling?",
"The ",
"sun is about 4.567 billion years old",
". Light emitted from the Sun will ",
"keep travelling until it hits something",
" and is absorbed. The surface area of any objects within a 4.567 billion light-year distance of the sun is absolutely tiny compared to the surface area of a sphere of 4.567 billion light-year radius, so almost all of the light ever emitted by the sun is still travelling.",
"So the short answer to your question ",
" is ... \"almost all of it\"."
] |
[
"but an obect near the sun has a large \"shadow\" on the surface of that sphere, and there are many things near the sun",
"True enough ... for teeny tiny values of \"large\". The closest object to the sun is Mercury, and it therefore would have the largest conical shadow behind it (away from the sun). Even this cone, the very largest shadow cone by far, would have an absolutely minuscule volume compared to the whole sphere.",
"Hence the conclusion ",
" stands.",
"{Edit} PS: The arithmetic for this:",
"Mercury, radius = 2,440,000 m",
"\nArea of Mercury facing sun = π * r",
" = 1.87 * 10",
" m",
" ",
"Mercury, Distance from Sun = 57,910,000,000 m",
"\nArea of sphere at Mercury's orbit distance = π * r",
" = 1.053 * 10",
" m",
" ",
"Therefore, percentage of volume of Mercury shadow cone compared to whole sphere ~= 1.77 * 10",
" %"
] |
[
"but an obect near the sun has a large \"shadow\" on the surface of that sphere, and there are many things near the sun"
] |
[
"How would you weigh (find the mass of) a helium balloon?"
] |
[
false
] |
Obviously scales won't work. Also this has to be an actual experimental method (no theoretical calculations). And is it possible to do it without damaging the balloon in any way?
|
[
"A helium balloon floats because its buoyancy force exceeds its gravitational force. Meaning that F_grav - F_boy is negative. (meaning that it pushes up)\nSo in equation form: F_net = m_balloon",
"V*g + m_weights * g",
"But if you tie some weights to the balloon until it is in perfect equilibrium (just enough to make the balloon and the weights float)\nthen you get: 0 = (m_balloon + m_weights)g - rho",
"g",
"This can then be rewritten into m_balloon + m_weights = rho*V ",
"Or: m_weights - rho*V = m_balloon",
"Meaning that if you weigh the weights that you used to balance the balloon and subtract the volume times the density of helium, you will be left with the weight of the balloon. ",
"Some balloon basics"
] |
[
"Synethos didn't assume you knew the density of helium, only the density of air. And you would indeed have to measure the volume of the balloon to use this approach, fortunately that is ",
"not difficult"
] |
[
"Thanks but what I don't know what the density or volume is? Say it's a mystery gas that isn't helium but is lighter than air, or a mixture of gases. "
] |
[
"We've all seen Ultra Ever Dry's substance repelling nano polymer - what would happen if you covered a boat in it?"
] |
[
false
] |
If the hull of a boat was coated in the polymer, would the boat sink in water? Would it float just as always? Would it float higher in the water? Inquiring minds need to know! Thanks in advance for any responses.
|
[
"The question I want answered is whether that coating would provide less resistance to water, enabling the boat to cut through the water more efficiently, kind of like wax does for a snowboard on snow. If there is a measurable effect, coud it affect things like fuel efficiency of a boat, or the dynamics of driving one?\nAt the very least, could that coating offer more protection for a hull, (from saltwater and marine life), with the end result being less cleaning and maintenance of said hull?"
] |
[
"Coatings like this are in development to reduce linear drag on boats, just like you suggest. The goal is fuel efficiency and long, thin boats like container ships would see the most benefit. Marine life is actually a major issue for coatings like this, as fouling of the coatings removes their hydrophobic quality and they are difficult to clean."
] |
[
"Not a great deal. The reason a boat floats is because its total volume (including the air in it) has a lower density than the water. Gravity pulls down the water as it is heavier than the boat including its air. (Of course if the boat fills with water this is no longer true and it will sink).",
"The nanoscale coating is just hydrophobic. I don't know its exact composition as they don't say so publicly for obvious commercial reasons. The coating is very good at repelling water.",
"All that would happen if you coated a boats hull in this polymer is that any water droplets that formed on its side or top would easily slide off. On its underside the water may even be protected from touching the actual normal surface of the boat because of the nanoscale coating and potentially some adsorbed air. There may be a tiny tiny buoyant effect because of any adsorbed gas but this is probably likely to be counteracted by the slight increase in mass caused by the tiny percentage increase in mass due to the polymer. ",
"The polymer has a very high opacity with a slight tinge.",
"Tl;dr. In short it would look almost identical in the water to before, maybe slightly whiter."
] |
[
"Why do certain things like coffee/beer taste weird when served at room temperature?"
] |
[
false
] | null |
[
"Many fats and other hydrophobic components have melting or softening points right at around 30 °C. The warmer drink gives them more mobility, and further promotes dissolution of flavor compounds. The molecules can diffuse to taste receptors instead of floating inert in suspension. Second, warmth causes aroma compounds to evaporate, so they end up in the nose. Much if not most of \"taste\" is actually smell/combination of taste and smell.",
"The mouthfeel is also different. Think of cold gravy or warm ice cream.",
"Beer is the opposite: the cold suppresses tasting bitter components and evaporation."
] |
[
"Hope this doesn't count as going off-topic, but you might be interested to know that traditional 'real ale' in the UK is served much closer to room temperature (generally around 10 C/55 F) and consequently the range of flavours is quite different to that of European and North American style beers."
] |
[
"Yeah, it means that Americans tend to complain about our warm beer when they come to the UK. ",
"For extra measure, real ale is not pasteurised or carbonated before being put into barrels - before being served, it is 'tapped', allowing air into the barrels, and is served either by gravity (the barrels are behind the bar and beer is poured out) or pumped out by hand. This also means that it needs to be served relatively quickly, i.e. within a few days, or it will go off. "
] |
[
"How does the body physically respond to different opioid medications that have very similar structures but a vast amount of different uses?"
] |
[
false
] |
Question pertaining how the body actually responds to these drugs and why the changes in their chemical structure is responsible for their vast uses. I understand that naloxone has a higher binding affinity to the opioid receptors but why doesn't the brain register this as a another opioid and continue the high? Same with methylnaltrexone which is used as a laxative for opioid induce constipation. They have the same chemical backbone and there is a small change in a carbon chain or two or a couple functional groups outside the backbone For reference structures. I read that the acetyl groups on heroin get cleaved when in the body to morphine which might be wrong
|
[
"Can you re-state your question in a bit of a more specific way?",
"I ",
" your question generally can begin to be answered by doing some research on the differences between agonists and antagonists. After that look into binding affinities. Then perhaps look into the effects of minor chemical changes on drugs.",
"For example, heroin (diacetylmorphine) has two acetyl groups as opposed to morphine's one. The addition of the second acetyl group makes the drug slightly more lipophilic and causes the drug to enter the brain more rapidly. This increases the perceived effects and causes the high from injection of heroin to be more rewarding than morphine. "
] |
[
"This commentor is correct. The main idea is to recognize that binding affinity and activity are completely distinct from one another. An agonist of the opioid receptor binds the receptor and induces the conformational change needed for activation, which an antagonist (like naloxone) binds to the site but does not cause a conformational change. This also prevents other agonists from binding and decreases their effect."
] |
[
"To add on to this, I think it is also important to note how the drugs are distributed. Like the parent mentioned, heroin is more lipophillic, which allows it to cross the blood brain barrier (BBB) more easily than regular morphine. From there, it can be converted into morphine and its conjugates, which activate opioid receptors in the brain to cause a \"high\". In comparison, methylnaltrexone cannot cross the BBB so you would not expect it to have considerable effects on the brain. Instead, it binds to opioid receptors in the gastrointestinal tract (which normally decrease motility = constipation) and \"deactivates\" them (= looser stools)."
] |
[
"Question about how solar systems developed: where did the first planets come from?"
] |
[
false
] |
Hi AskScience, I have a question that David Christian's recently posted "Big History" talk on TED brought up in my curiosity, but I'm not sure if I'm phrasing it well. He talks about the process of particles joining together to form extraterrestrial bodies. But, it seemed that massive stars formed before smaller bits and chunks of things like asteroids or even planets. My question is this: if there are only huge suns and tiny particles and atoms swirling around in the universe, wouldn't the stars' gravity be far too strong for any of those particles to escape or develop enough momentum to orbit? Was it a complete happenstance 99.9% ideal scenario, or am I just missing some bigger piece that would drive the formation of planets?
|
[
"I think your main confusion is in thinking that big things formed first. The formation of the Sun and planets was in essence simultaneous. The ",
"Wiki article on formation of the Solar System",
" is a good place to start."
] |
[
"Certainly a lot of material slowed down and hit the sun but what was left over formed the planets. No one is entirely sure how the planets formed but the general idea is there was a disk around the sun of dust which rotated and material collides and sticks together forming larger and larger bodies and eventually you get the planets and asteroids. Now a lot of material in that disk hit the sun because it slowed down too much in collisions but other material did not slow down and stayed in orbit."
] |
[
"In a lot of ways, you are correct. ",
"The sun represents 99.86% of the mass in the solar system, so almost all of the mass was captured by the sun's gravity.",
"While this was happening, a small fraction developed enough momentum escape and reach orbit, and amongst that matter, planets formed. 90% of the remaining matter formed Jupiter and Saturn, and 90% of what was left after than formed Uranus and Neptune.",
"And we got a goodly chunk of what was left. It wasn't exactly happenstance...there was a whole lot of matter in the early solar system, it is no surprise some slipped through the cracks. "
] |
[
"How are tumors able to grow random parts of our body within them?"
] |
[
false
] |
Thank you for any clarification!
|
[
"What do you mean? I assume you are talking about when cancerous cells are discovered somewhere in the body although they originate elsewhere. Occasionally cancerous cells can detach from the place they originally grew, and plant themselves elsewhere and grow there, e.g. cancerous cells from the breast being found in a lymph node."
] |
[
"I suspect the OP is referring to ",
"this",
" ",
"r/science",
" story (currently on the front page)."
] |
[
"Sorry, to clarify i mean I've seen pictures of tumors that are growing hair or teeth, I was just curious how that happens and why?"
] |
[
"How can a single particle have no temperature?"
] |
[
false
] |
I was reading Neil deGrasse Tyson Death by Black Hole when it says, "a single particle can't have a temperature because temperature is how fast all the particles of something are moving so a single particle can't have a temperature." The definition I understand but something having no temperature I can't understand.
|
[
"A single particle ",
" have temperature, but it's for reasons that aren't actually being discussed here. They're skirting around the answer, and frankly I'm kind of surprised; This is an 8-hour old question, someone should have pointed out what I'm about to.",
"Contrary to popular belief, temperature is ",
" the average kinetic energy of a group of particles. There's a lot of belief out there that it is, and in the case of an ideal gas (which of course is a simplified model as it is) that's mostly true. But that's the only time it is! Think about it a second, and you'll realize this is true. What are the ",
" of temperature? There are none; it's unitless! If it were really the average kinetic energy of whatever it'd have units of energy. Still don't buy it? Let me ask you this: I have an ice cube at 0 °C and a glass containing an equal mass of liquid water at 0 °C. Which particles have more kinetic energy? They're the same temperature. They should be the same, no?",
"So let's talk about what temperature really is. In the most basic, fundamental sense, temperature is an arrow, a thermodynamic arrow, that tells us which direction heat flows. And heat is the transfer of thermal energy between two systems. That's all temperature does, and that's why it has no units: We define centigrade as 0 at the freezing point of water and 100 at the boiling point of water (at 1 atm), but we could have easily have redefined it as 32 and 212 and called it fahrenheit, or 273.15 and 375.15 and called it kelvin. In fact, we have. But the scale of temperature is 100% arbitrary. We've settled on kelvin, scientifically, because it makes the math simpler and it's close to centigrade. If we really want to calculate temperature for degenerate systems like your single particle system we can actually do that, because it's relatively straightforward once you know the rigorous definition of temperature:",
"T = 1 / (dS/dE)",
"What the hell does that mean? Well it defines temperature as the inverse of of the derivative of the ",
" with respect to ",
". Of course that begs the question \"what the hell is the entropy?!?\". Well the entropy is the log of the number of states. With this definition, and defining the entropy S as the log (any base will do but let's make it base 10 to make the math easy) ",
", we can consider what happens when we add energy to your system of 1 particle. Then we should consider what happens when you add energy to a system of 2 particles because you need two particles to have a defined temperature.",
"OK so we have your singleton particle. Let's say it's in it's lowest possible energy state. That's not an approximation, but rather a recognition that temperature as I'm discussing it is ",
" temperature. It has energy equal to E",
" , the minimum ground state. We know that energy is conserved, and that there's only one particle in your system so there's exactly one state for your system, the lone particle in the ground state. The log of 1 is 0, so the entropy is 0. For the sake of simplicity we're going to pretend that E",
" is 0. It doesn't much matter, but when we get to a larger number of particles you'll see in a moment all we really care about are the energies above and beyond the lowest possible ground state.",
"Now let's add a unit of energy. The system now has that one particle, and since it's the only possible particle that can occupy a higher energy state (the particle is the system is the particle) then it's occupying a higher energy state, E",
" , the excited state. Since there's nothing else out there to take the energy from that particle it's still stuck with just the one state, where it's occupying the higher energy state E",
" , so your system ",
" only has one possible state. So the entropy is again the log of 1 which is 0. It should be obvious at this point no matter how much energy you add to this system there will only be one state, the lone particle having all the energy, so the entropy is a constant. The derivative of a constant is 0, thus the inverse of that is 1/0 which is undefined.",
". Because with one particle there is only one state and the entropy is constant, thus the derivative is 0, thus the inverse is divide by zero undefined.",
"But let's look at two particles now!",
"In the lowest possible state, E = 0, both particles are in the ground state. Thus, there's only one state and the entropy is 0. But in the ",
" energy level, E",
" , we have multiple states! (Finally!) We can have particle #1 at E",
" and #2 at 0, or the converse, particle #1 at 0 and particle #2 at E",
" ! That means the entropy is 2 and the log of that is 0.3. Since we're defining the energy E",
" as 1, the derivative going from E = 0 to E = 1 is now 0.3, and the inverse of that is 3.33. ",
" this is not the textbook calculus calculation of the derivative. But it should be immediately apparent, at least, that the derivative is nonzero thus the temperature is ",
" at that energy state. But let's go further: Let's give this system of particles E = 2 * E",
" = 2. Now we have three possible states: #1 at 0 and #2 at 2, #1 at 2 and #2 at 0, and both particles at 1. The entropy is log(3) = 0.47 and the derivative is .17 and the temperature is 5.88, at least according to our ham-handed calculation of the derivative of what is a discrete system that may or may not be differentiable. I think it probably is, but I'm a physics guy, not a math guy.",
"Now let's take a step back and remember why we have temperature. Temperature tells us the direction of the flow of heat energy from \"hot\" system to a \"cool\" system. Now let's see what happens when we take another system and put it in thermal contact with our two-particle system, when it has energy equal to E",
" .",
"The entropy before they're in contact is the same as just the entropy with the first system. There are three states for one system and just the one state for the other system. Put together they have 3 * 1 states which is still just 3 states. But what happens when they're in contact, when particles from the first system can pass their energy to particles in the second system? Well now we have many more states! We have 4 states where one particles has E = 2 energy, and another 6 states (hello combinatorial mathematics!) for the cases where two of the four particles have E = 1. That's 10 states.",
"Remember the second law of thermodynamics? One way to put it is: ",
". Putting these two systems in thermal contact means ",
" will flow from the more energetic system to the less energetic system because that's the path that leads to the most entropy!",
"The rest of the posts on the thread, at least most of them, aren't strictly speaking ",
", but the rigorous answer to why a singleton particle has no temperature is the quantum thermodynamic one. Of course this makes sense, once we realize that thermodynamics isn't ",
" a study of physics. The reason they also call thermo \"Statistical mechanics\" is that it's also the study of statistics, of the behavior of ",
".",
"Note, in this explanation I've made a variety of basic assumptions to make the math and the hand-waving easier to understand. For example that the second excited state of your particle has energy equal to ",
" that of the first excited state. It doesn't have to be that way, and often it isn't. Indeed, another assumption is that there even ",
" a second excited state! Consider some number of particles in a magnetic field. Each particle has ",
", right? A magnetic moment, right? Each one can either be ",
" or ",
", and depending on the magnetic moment one of these states will be at E = 0 and one will be at E = E",
" . But there's no E",
" in this case. I mention this example because when you read about scientists creating systems with \"negative temperature\" they're often using a system almost exactly like I'm describing.",
"Consider, for a moment, a system where 10 particles has energy equal to 9 * E",
" , where E",
" is the energy of a particle with spin \"up\", which we're going to say is oriented ",
" the magnetic field, thus is the higher energy state. There are ten states to that system, one where the first particle is spin down and the rest are up, one where the second particle is spin down and the rest are up, etc. etc. etc... Thus the entropy is log(10) = 1.",
"But what happens when you ",
" a unit of energy to that system? Well now you have ",
" states. The only case is where every particle is spin up , thus there's 1 state and the entropy is log (1) = 0.",
"So now when you add energy, the entropy ",
". That means the derivative is negative. And ",
" means that the temperature is likewise negative!"
] |
[
"Temperature is not a property of fundamental particles, like mass, charge, spin, etc. Temperature is a lot like pressure: it's a property that only makes sense on a ",
"macroscopic",
" level. In fact, pressure is a way better example to think about if you're confused. ",
"Think about this: if you have a gas, it has a pressure, right? This is defined by the amount of force per unit area it exerts on the things around/within it. The atmosphere, for example, exerts a pressure of about 14 pounds per square inch, or about 1 kg per square centimeter (this is assuming you are near sea-level; atmospheric pressure decreases the higher up you go). This is a quantity ",
"you can measure",
", and it seems as if all gasses have it.",
"But what's the pressure of a single oxygen molecule? If you think about it for a while, the obvious conclusion is that the question doesn't make sense! Pressure (like temperature) is a quantity that can only be measured if you have ",
" of the substance.",
"If you are interested in how temperature is defined specifically at an atomic level (and this part is going to get a little mathematical and esoteric), it is defined by the ",
"Maxwell-Boltzmann distribution",
", which is an equation that describes the ",
" that a certain particle in a certain substance with a certain temperature will be moving at a certain speed. If you only have one molecule, it only has one speed, which means that you really can't define its temperature.",
"Edit: added a link for \"macroscopic\", I realize that this might be an unfamiliar term for lots of people."
] |
[
"You can't just assume something has MB statistics, that's not how it works. MB distributions arise in some systems of a large number of constituants in some cases. In a metal at equilibrium, the electrons have Fermi-Dirac statistics. In a heterostructure they may well have a distribution nothing like FD, BE or MB. In non-equilibrium that could have any distribution. It makes no sense to look at a single particle/body and just decide it must secretly be part of one many-body distribution or another. It's like looking at a single grain of sand and saying \"this must clearly be the east-most tower of a sandcastle!\""
] |
[
"Any ideas on preventing \"monitor wobble\" on a CRT next to a stir plate?"
] |
[
false
] |
Is there any type of shielding option?
|
[
"Yes, no problem. Here are the solutions:",
"Move the monitor.",
"Move the plate.",
"Turn off the monitor.",
"Turn off the plate.",
"Replace the CRT monitor with an LCD panel.",
"Magnetic shields exist, but a suitable one would cost more than the combined cost of the monitor, the stir plate and the table they're sitting on.",
"Shielding against a low-frequency magnetic field is very difficult. Not impossible, but difficult. Ordinary metal shields, for example aluminum, won't have any effect at all at low frequencies."
] |
[
"In that case, get an LCD screen."
] |
[
"Thanks. Didn't know if there was an easy solution besides those five."
] |
[
"Iridium and similarly hard metals are difficult to machine due to extreme work hardening. Is \"grinding\" based machining also affected?"
] |
[
false
] |
I understand how drilling and traditional milling would be made essentially impossible due to rapid work hardening, but couldn't a "grinding" approach be used to get around this? Is there something I am not understanding about work hardening? Does work hardening affect materials at such a "small-scale" as sanding away tiny pieces of the material?
|
[
"Iridium can be machined, it's just a lot harder to do than other materials and there are much eaisier ways to form it. If you want to cut it with an endmill you are going to want a properly coated tool that has a hard coating capable of handling high temperatures - depending on your setup you might be able to do it with PCD or AlTiN tool. Most machinists would get pretty pissy if you tried to get them to run the job though, the tools just won't last that long and it will take a lot of babying, you might have to swap tools regularly before failure in the middle of a job, use very low speed/feeds, etc.",
"You can grind it, that's not a problem. Best way to cut it is probably EDM. Milling is only the \"worst\" option, not impossible. BTW grinding is not an ideal solution because the grinding tool will wear over time and it is hard to hold tolerances. Grinding can be done very precisely but will often use in-situ measuring machines to machine-measure the surface, which is costly but for example one of the best ways to form a complex lens."
] |
[
"I work with glass and ceramics a lot. A critical element is operating in a brittle mode. We're trying to crack the material evenly, to a specific depth. Each grinding operation should remove material while also imparting shallower cracks each time. Until eventually you use a polishing operation that doesn't create sub-surface damage. But with metals it's really difficult to grind in this matter without specific tools, speeds, and feeds. Which you mentioned above."
] |
[
"shallower",
"important qualifier there.",
"when you get to a point where a pass-over doesn't make shallower cracks, then you can't make the material any smoother because each pass-over will just look like the previous one."
] |
[
"What is it that actually makes air \"move\"? Is air stagnant and it's just the earths rotation or?"
] |
[
false
] | null |
[
"Just like air flies out a balloon, wind is air moving from a higher pressure zone (like the inside of the balloon) to a lower pressure zone (the outside).",
"The easiest way to create this difference is to heat parts of the Earth differently. Warmer air is less dense, which means there is lower pressure there. Cooler air from it's surroundings moves in and thus we see wind."
] |
[
"But the earths rotation itself does not move air.",
"The Coriolis force would beg to differ.",
"If you start a rotating planet out with no heat differences and no atmospheric motion other than a few random fluctuations, it will self-organize into jet streams, all thanks to the Coriolis force (which is caused entirely by the planet's rotation). There was a pretty ",
"ground-breaking paper in the 90s",
" showing this, and now encompasses a whole class of climate simulations known as a \"spin-ups\"."
] |
[
"But the earths rotation itself does not move air.",
"Sorry but this is completely incorrect. The earth's rotation is a leading force throughout most of the atmosphere, and away from boundary layers, balance between the Coriolis force and pressure gradient force are the leading terms affecting the motion of air parcels. Whenever the ",
"Rossby number",
" is less than 1 (which it is throughout most of the atmosphere), the earth's rotation is significant."
] |
[
"How did we treat cancer in the past (pre 1900) Did we even know about it?"
] |
[
false
] |
How did we go about dealing with cancer before radiation treatment. Did we even know that cancer is what was killing some people? When did we learn it was cancer causing the deaths?
|
[
"They knew about it. They had no real treatment other than to cut it out. They wouldn't discover it until it caused problems so usually too late. Leukemia is called white blood because that's how the person would die. So many defective white blood cells that the blood literally turned white. All they could really do was to give it a name. "
] |
[
"It's pretty simple... any cancer that produced an obvious tumor was easy to understand in terms of, \"Cut out the tumor\". Then, if that cancer was metastatic, or any form of cancer without an obvious tumor, you died. Period. ",
"You have to remember though, that the likelihood of most cancers increases with age, and for most of human history people died before cancer could kill them."
] |
[
"The average age at death was pretty low, but that's because of a high infant mortality rate. If you survived to adulthood you could expect to live into your sixties. That being said cancer still didn't kill very many of them because getting sick in your old age kills you much faster."
] |
[
"Could two genetically identical creatures be different species if they are not genetically linked? (Explanation in comments)"
] |
[
false
] | null |
[
"If the two creatures are 100% genetically identical, then they would be, from a molecular biologist's point of view, the same species."
] |
[
"No. There are good reasons to believe that once intrinsic reproductive isolation between two populations is complete (i.e. they cannot possibly produce fertile offspring), they almost certainly (i.e. with probability so close to 1 that it may as well be a rounding error) will not converge to reproductive compatibility further down the line.",
"There are certainly cases of populations starting to evolve reproductive isolation, but then reversing the process, as discussed ",
"here",
", but that, while super interesting, is different than what you're asking about."
] |
[
"Are there any example of this in nature? Different animals or organisms evolving separately yet being able to interbreed further down the line?"
] |
[
"Why are there shadows in electron microscopy? How are they different from shadows due to the absence of light?"
] |
[
false
] |
I just watched and noticed that there are both shadows and gloss where you'd expect them if it was made with a regular light capturing camera. Are these effects identical with shadows and gloss due to light (or the lack thereof) and if not, how are they different? Are there any differences in size, strength, specularity etc.? Is there an effect similar to iridescence? Or is this part of post-processing? In my research field, there are several examples of scientifical visualisations that create faux shadows in order to simulate spatiality, but to the best of my knowledge, electron microscopy isn't one of these technologies.
|
[
"There are two main types of detector for imaging on an SEM. Backscatter electron and secondary electron detection.",
"Backscatter electrons are the 'reflected' electrons that have scattered of atomic nucleus, the chance that an electron will backscatter is a function of the atomic mass, i.e. areas with higher average atomic mass appear brighter. In terms of shadows etc. Backscatter electrons behave in a similar way to light, in that they are the 'reflected' electrons. This causes shadows to behave the same as it would in light. ",
"Secondary electrons are quite different, and you need to be cautious in interpreting secondary electron images as you would a light image. The primary electron beam penetrates some distance into the material surface, scattering about, think of this causing a teardrop shaped volume under the material surface where there are ionising primary electrons in high concentration. These primary electrons cause low energy secondary electrons to be emitted. The secondary electron detector detects these low energy elections by using a low voltage electric field that isn't strong enough to effect the high energy primary and backscatter electrons. Because these secondary electrons are created in a teardrop volume under the surface, where the primary beam strikes near and edge or slope, some of that teardrop is exposed to the chamber, causing a much larger proportion of secondary electrons to escape and be detected. Additional, these low energy electrons follow a curved path causing odd illumination effects.",
"In essence, both modes can have shadows and glare, and these can be deceptively similar to light imaging, however, as in the secondary electron image you showed, the glare is likely caused by the angle of the surface and the shadow by the tool piece blocking the path to the secondary electron detector rather than indicating the source of illumination."
] |
[
"/u/bloodyTribology",
" is spot on. Both the backscattered and secondary electron detectors detect the intensity of electrons hitting their detector, and this is what's used the create the image. So it makes sense that if something is in the way, this will reduce the intensity of the electron beam, and the brightness of the image in that spot, creating something that looks like a shadow, for both types of detector/ mechanisms. I literally just studied this as part of second year of Materials Science, really interesting stuff! "
] |
[
"The warping in this case is caused by the drill bit being made of a material that is slightly ferromagnetic. The magnetism of the bit slightly warps the path of the primary electron beam as it passes by the edge, causing a skewing of the image. "
] |
[
"Why are do most medications have HCl in it?"
] |
[
false
] |
[deleted]
|
[
"First of all, many chemicals used as drugs contain a nitrogen atom. Not all nitrogen-containing chemicals are basic, but many are. Specifically molecules which contain the ",
" functionality are basic. Such molecules are prone to oxidize when exposed to air. In addition, some suffer from poor solubility in water, which is generally a problem -- good water solubility generally translates into better drug absorbtion.",
"For molecules containing the amine functionality, one solution to either or both these problems is to react the basic molecule with an acidic molecule, to make a salt. The acidic molecule is often (but not always) HCl, or hydrochloric acid. So, if you take one molecule of oxydocdone and one molecule of HCl, you form the oxycodone-HCl salt. The electron deficient H+ from the HCl is strongly attracted to the electron-rich nitrogen, and forms a positively charged portion of the molecule. The Cl- hangs around to balance the charge, so there is no net charge. (Of course, a bottle of positive charges or negative charges is generally called a battery, and you don't want to swallow that for a medication, so you want the Cl- to be there as well!)",
"The resulting molecule is less prone to air oxidation (more stable) and is also more water soluble, since it is more polar (and polar things tend to dissolve in water better than non-polar ones)...and makes a better medicine. "
] |
[
"I don't know what the pharmacological role of this is, but I can tell you that these formulations don't contain HCl molecules ",
". The 'hydrochloride' of a drug refers to the chloride salt of a protonated (usually) amine.",
"Let's take ammonia for example, NH3. When protonated it would form ammonium, NH4+, however one cannot get solid ammonium. If you add a couterion like chloride to it however, Cl-, we would get NH4Cl. In the pharmaceutical industry this is designated as NH3.HCl, and would be called 'ammonia hydrochloride'."
] |
[
"Other amine-bearing pharmaceuticals are (although more rarely) salts of other acids. One common example is ",
"sildenafil citrate",
" (more commonly known as \"Viagra\") which uses ",
"citric acid",
" instead of hydrochloric acid. This works better because sildenafil has multiple amines, and citric acid is a triprotic acid (generic formula: H₃A). ",
"The choice of acid used to make the salt is dependent on a few things, namely: (1) The counterion (Cl-) should be something safe for consumption, as in the case of both chloride and citrate. (2) Price - both HCl & citric acid are cheap! (3) The product should have a low solubility in some solvent, while contaminants have a high solubility, allowing easy separation of the product. etc... there are quite a few considerations in play. "
] |
[
"What percentage of genes are purely human?"
] |
[
false
] |
We share ≈96% of our genes with gorillas, ≈50% with bananas, so if we added all the specific shared genes what percentage is purely human?
|
[
"It’s hard to know for sure. We don’t have a solid count for how many genes humans have to start with because there is some discussion about what counts as a gene, and not all sequences that could be considered a gene have been fully studied. Out of the 20,000-25,000 genes in our genome, 23 have been identified only in humans and not in any other currently living animals. ",
"https://www.theatlantic.com/science/archive/2015/10/the-mystery-of-human-only-genes-and-why-theyre-a-bit-like-oreos/410206/"
] |
[
"Important to note that just because we have the genetic information doesn't mean it will be expressed to the same degree if at all. A lot of what we are like originates from what genes are suppressed more than from which unique ones we have."
] |
[
"There are maybe 6 genes that are only found in humans. That's about 0.002% of the human genome.\nBut the answer is more complicated than that. What makes us human is not just the genes but how they are regulated. We share 98-99% genes with chimps but when looked closely the genomes are all filled with structural rearrangements. This results in a very different regulatory system in both. So the actual similarity may be 60-70%."
] |
[
"What would be the impact of a substance that could radiate cold the same way most things radiate heat."
] |
[
false
] |
The way I understand it when something cools down it's because the heat has spread out to more atoms and gotten them moving, using up the energy of the source of the heat. Now i'm wondering what kind of impact a substance that could, instead of taking in the heat and speeding up it's molecule, slow down the molecules of of what comes into it's area of effect.
|
[
"You have a mistaken idea of thermodynamics. Very quickly, heat is thermal energy.",
"Temperature dictates which direction heat naturally wants to flow -- that is without applying external energy in the form of work (e.g., a refrigerator/heat pump), the net heat flow will always be from an object with a higher temperature to an object with a lower temperature. ",
"When you talk about something radiating photons in proportion to their temperature to the fourth power ( T",
" ) due to blackbody radiation."
] |
[
"Yes, for pedagogical reasons, I specifically neglected negative temperature (on a kelvin scale). Really it makes more sense to talk about inverse temperature β = 1/T = dS/dU where S is entropy, U is thermal energy and then heat flows from low beta to high beta. ",
"But negative temperature is extremely rare; you only really deal with it when you are in the lab dealing with weird things like lasers where you start with an unnatural state where adding random thermal energy reduces the entropy.",
"And I disagree with your substitution \"net heat flow will always be from an object with a higher ",
" ",
" to an object with a lower ",
" ",
"\". That's not true with energy in their. For example different objects have different internal energy at the same temperature. As a rough example the heat capacity of 1 kg of ice water is respectively 2.1 kJ/K; while a kg of solid gold has a heat capacity of 0.13 kJ/K. Thus, very roughly 1 kg of ice water at -1 C (~272 K) has an internal energy of ~600 kJ (actually heat capacity will change at different temperatures and they'll be some other phase transitions). Meanwhile, 1 kg of gold at 20C (293K ) will have an internal energy of ~40 kJ. Combining the two systems you will see the net heat transfer will be from the high temp (hot) gold system to the colder system ice (solid water), even though it starts with much more internal energy.",
"PS: Total blackbody power radiates is proportional to T",
" is just stefan-boltzmann law."
] |
[
"Yes, for pedagogical reasons, I specifically neglected negative temperature (on a kelvin scale). Really it makes more sense to talk about inverse temperature β = 1/T = dS/dU where S is entropy, U is thermal energy and then heat flows from low beta to high beta. ",
"But negative temperature is extremely rare; you only really deal with it when you are in the lab dealing with weird things like lasers where you start with an unnatural state where adding random thermal energy reduces the entropy.",
"And I disagree with your substitution \"net heat flow will always be from an object with a higher ",
" ",
" to an object with a lower ",
" ",
"\". That's not true with energy in their. For example different objects have different internal energy at the same temperature. As a rough example the heat capacity of 1 kg of ice water is respectively 2.1 kJ/K; while a kg of solid gold has a heat capacity of 0.13 kJ/K. Thus, very roughly 1 kg of ice water at -1 C (~272 K) has an internal energy of ~600 kJ (actually heat capacity will change at different temperatures and they'll be some other phase transitions). Meanwhile, 1 kg of gold at 20C (293K ) will have an internal energy of ~40 kJ. Combining the two systems you will see the net heat transfer will be from the high temp (hot) gold system to the colder system ice (solid water), even though it starts with much more internal energy.",
"PS: Total blackbody power radiates is proportional to T",
" is just stefan-boltzmann law."
] |
[
"In North America there are often invasive species from Asia, such as The Spotted Lantern Fly. Are there invasive and pesky species from North America on other continents?"
] |
[
false
] | null |
[
"How in the heck does a Whitetailed Deer pop up in NZ? And why haven't you shot them all yet, they are delicious."
] |
[
"You mean like Wapiti, Whitetailed Deer, trout, Canada geese, Gambusia, Rudd, Brown Bullhead Catfish, Lodgepole pine,, Pinus Radiata, mexican daisy(More Central/South America) ",
"That's just a quick skim of the list of invasive species in NZ, there are surely more that I missed."
] |
[
"Of course. From the top of the head, here are some invasive plant species in Europe that originate from North America: Ambrosia artemisiifolia (ragweed), Amorpha fruticosa (false indigo bush), Phytolacca americana (pokeweed), Robinia pseudoacacia (black locust), Erigeron annuus (daisy fleabane)...there are many more but these you can see literally everywhere"
] |
[
"Is there scientific evidence to support the old wives tale \"Red sky at night sailors delight, red sky in morning sailors take warning\"?"
] |
[
false
] |
If so, why does a red sky at night not mean bad weather, but the red sky in the morning does?
|
[
"Let me google that for you....",
"Red sky at night, sailors delight.\nWhen we see a red sky at night, this means that the setting sun is sending its light through a high concentration of dust particles. This usually indicates high pressure and stable air coming in from the west. Basically good weather will follow.",
"Red sky in morning, sailor’s warning.\nA red sunrise reflects the dust particles of a system that has just passed from the west. This indicates that a storm system may be moving to the east. If the morning sky is a deep fiery red, it means a high water content in the atmosphere. So, rain is on its way"
] |
[
"Because of the Coriolis effect, wind on the ocean generally travels in the same direction, and locally speaking, storms like to travel eastward."
] |
[
"well surely this all depends on where you are in the world, and what direction weather usually comes from etc."
] |
[
"Would it be feasible to create artificial \"mini-supernovas\" on Earth in order to synthesise elements that are scarce?"
] |
[
false
] | null |
[
"Supernovas do create most of the atoms heavier than iron.",
"Yes, it is feasible to create heavier elements, and we do this already in particle accelerators or by neutron capture in fission reactors. We've been creating plutonium this way since the Manhattan Project in the 1940s, because it doesn't occur naturally. In general, though, this is a very expensive way to produce small quantities of an element."
] |
[
"This is how we make isotopes for radiation therapy."
] |
[
"You mean nuclear fusion, super novas don't create the elements, they disperse them after they were already manufactured in the cores of stars.",
"Edit: I'm an idiot."
] |
[
"At what pH level (base and acid) would a substance be dangerous for human consumption?"
] |
[
false
] |
My friend asked me this question over email, and I did my best to answer. I would love to hear what thinks! I told her that the likelihood of the strong acid/base reaching the stomach was low, seeing as it would either burn the mouth/esophagus or saponify tissues before reaching the stomach. Though, no foods have the capability of doing this. (I gave her a bit more information than just that, but that's the gist.)
|
[
"Generally speaking, strong acids (pH<2) and some strong bases (pH>12) start to cause caustic damage to the esophagus and various linings of the tract. More information can be found ",
"here",
". If a food were quite basic, it would adversely affect the acidic environment of the stomach and most likely cause indigestion.",
"On a side note, much damage to tooth enamel comes from acidic sodas such as Coca-Cola, which has a standing pH of roughly 2.5"
] |
[
"Are you allowed to cheat and use tiny amounts of acids/bases, if so the sky is the limit. go for either ",
"magic acid",
" or any of the other super acids. In small ammounts it just becomes a game of consuming so little that only relatively useless molecules are BBQed"
] |
[
"Strong bases cause saponification of lipids, which is quite bad, worse than the effects of any comparably strong acid (say, pH 13 vs. 1). We regularly eat rather acid chemicals (lemon juice, vinegar), while we couldn't do that with bases."
] |
[
"Hyper saline lakes such as the Dead Sea have extra buoyancy. Would a boat have to be designed differently than for a normal lake, and how well would a normal boat work on a hyper saline lake?"
] |
[
false
] | null |
[
"you'd just have a lower water line with more of the boat sitting out of the water. in most cases it wouldn't make that much of a difference. an inch or two probably. in the case that the boat was sitting so high that it wasn't stable, you could just add weight, but that's highly unlikely. the difference made by the extra buoyancy likely isn't as much as the difference made by loading the boat to capacity with people. in short, unless it's a really small and top heavy boat, then it doesn't make a difference. if it is really small and top heavy, an extra 50 lb plate should do the trick. "
] |
[
"/u/MediocRedditor",
" gave an OK answer, but it's not complete.",
"There are two critical balance points to a boat: the ",
" (CoG) of the boat, and the ",
" (CoB). If the boat rotates in the water, this is the spot around which its mass will rotate. The CoB is not well defined, in the sense that it's different for, say, pitches (bow moving up and down, stern moving down and up) than for rolls (bow and stern stationary, boat rocking side to side). It's generally lowest for rolling motions.",
"For the boat to be stable in the water, the CoB has to be ",
" the CoG. That's what \"ballast\" is all about: you weight down the bottom of the boat to lower its CoG and make it more stable. Midsized sailboats are called \"keelboats\" because they generally have a large weight suspended some distance below the bottom of the main hull, to stabilize the boat by bringing the CoG down.",
"The deal is that, as the boat floats higher in the water, the CoB moves down compared to the boat and to its CoG. If the boat floats high enough, the CoB will drop below the CoG and the boat will become unstable.",
"This shouldn't be a big issue for most designs, which have plenty of distance between the CoB and CoG. Keelboats, especially, should be fine because they are hyper-stable -- the keel is some distance below the hull itself, so a couple of inches of buoyancy won't make much difference to normal stability, although it will allow the sailboat to roll slightly more in a stiff wind. But for light skiffs or for poorly designed boats or ships, the extra buoyancy could become a big deal."
] |
[
"Since the waterline is lower, would it be easier to row the boat because there would be less friction / a sharper prow?"
] |
[
"What is the current research on prions?"
] |
[
false
] |
For those of you haven't heard of , they're infectious proteins, and terribly interesting.
|
[
"http://scholar.google.ca/scholar?hl=en&q=prions&as_sdt=0,5&as_ylo=2011&as_vis=0"
] |
[
"Thanks, wasn't aware there was a google scholar search."
] |
[
"For biological/medical research, Pubmed.gov is the standard search engine. You might want to find review articles.",
"But what exactly were you trying to find about prions?"
] |
[
"Do the same areas of the brain 'light up' when we read a book versus listening to it?"
] |
[
false
] |
Inspired by made by from . I also have a follow up question: How does listening versus reading pertain to the permeance of memory. I understand that we all learn differently, but what I'm more interested is the 'storage of the data' (and I guess accessing the data too).
|
[
"When we view a picture, or a word in this case, there are visual regions of the brain that process this incoming sensory information. The same goes for auditory information, and the primary auditory and primary visual areas are separated in the brain. At this point different areas of the brain would be active when reading and listening to the book. ",
"However, current research is showing that things like semantic relationships can be shared by brain regions, and even the pattern of activity within this region. For example, one study showed that a computer algorithm trained to learn difference between the pattern of brain activity when participants viewed the written names of animals vs tools, could also tell the difference when tested on the brain activity when the participants listened to these names, and vice.versa (Akama et al. 2012). This suggests that some brain areas code for the concept of particular words, regardless of if the word is read or heard. ",
"Ref: ",
"http://www.ncbi.nlm.nih.gov/pubmed/22936912",
" "
] |
[
"Partly. We have different brain areas for auditory and visual sensory information. Language comprehension, however, is a specific part of the brain (Wernicke's area). So, in both cases you will probably have activity in Wernicke's area, and in the Occipital lobe (the back of the brain) when reading the book, and in the temporal lobe (more on the side of your brain) when listening to it."
] |
[
"For me,when I listen to an audio book,or read a book,it's like watching a movie in my head.Why would this be happening if I'm hearing the book rather than reading it?"
] |
[
"When an charged particle slows down, an electron for example, it radiates photons that have spin, where does the angular momentum come from?"
] |
[
false
] |
An electron can only spin up or down, from .5 to -.5 in steps of 1 How does it emit multiple photons while being decelerated from high speed? and where does that angular momentum come from, if it didn't come from the electron?
|
[
"The only way the electron can slow down is by interacting with something. The angular momentum comes from that interaction. "
] |
[
"The Bohr model is correct. It accurately predicts the energy levels of the hydrogen atom and the Rydberg formula. It's why he won a Nobel prize. ",
"The Schrodinger model is a more sophisticated model that contains al the results of the Bohr model. It describes \"shells\" of the Bohr model in terms of probabilistic distributions of the position of the electron around the atom. ",
"These probability clouds are likely what you're talking about when you say volumes. These clouds, which are associated with the probabilistic location of the electron, also have a quantized angular momentum associated with them."
] |
[
"Total angular momentum of an electron is the sum of its angular and orbital angular momentums. When it falls down to a lower orbit, orbital angular momentum of the electron decreases. "
] |
[
"Why can we only see light after it bounces off something or when it is at the source of the light? Why don't we see light energy as a sort of mist?"
] |
[
false
] |
What I mean here is like if you point a laser at a wall, you can see the dot, but not the beam of light going to or coming from the dot, making it only visible if powder or dust or smoke enters the beam. Why does light seem to be completely invisible while travelling through air? What changes when it bounces off a surface?
|
[
"The key point is the simple fact that you only see light that makes it to your eye. It can either come directly from the light source or bounce off the wall first. For the laser beam example, if you look directly in the beam you obviously see light. You also see light being bounced off the wall. But why should you see light in between? The light is focused as a beam going in one direction. While there is laser light going through that point, none of it is heading towards you. If however there is smoke or dust, then it scatters off the dust and part of it changes direction to point towards your eye. "
] |
[
"Imagine that you're Superman and you're blindfolded and somebody is shooting a machine gun.",
"If they shoot the bullets directly at you, then you can feel them hitting you. If they shoot them in some other direction, then you can't feel them hitting you. If they shoot them so that they ricochet off an object and hit you, then you can feel them hitting you.",
"Light is something like that. It's a bajillion little particles (oversimplifying here) called \"photons\". ",
"If they go into your eye, then you see them. If they don't go into your eye, then you don't see them. If they hit a wall or a tree or something and bounce off it and enter your eye, then you see them. ",
"That's pretty much it. "
] |
[
"Because the tiny particles of light have to actually hit your eyes. If they are all going in the same direction, and aren't pointing at your eyes, you can't see. Your eyes work by detecting photons hitting your retina. ",
"So it's not necessary for them to bounce of something to see them, but they have to literally be going in the direction of your eyeballs. When you see a laser going through a mist/dust, all those photons which are going in a single direction, get scattered into a giant amount of directions, some of which go into your eyes, some bounce of more mist and then into your eyes. The effect is that you can \"see\" the beam. What is really happening is light/photons are being scattered by the mist and some hit your eyes.",
"edit to add: It's not entirely accurate, but it's easiest in this context to think of light as little balls (photons). You only \"see\" when they hit your eyes. The balls don't emit any light on their own; they are the light. That is why they are \"invisible\" when they aren't going directly into your eyes."
] |
[
"Anti-choice talking point or point taken?"
] |
[
false
] |
A comment sends me looking for an expert response: "Adult stem cells (stem cells taken from a donor) are proven effective...fetal stem cells are not. In fact, in several cases using fetal stem cells, the patients have developed tumors. To use fetal stem cell research as a justification for abortion is assine and morally reprehensible." My instinct is that this has to be absolute bullshit, up there with "abortions cause breast cancer." But is there any truth to it, and is that a meaningful truth or just due to the lack of research with fetal stem cells?
|
[
"Fetal stem cells come from cord blood taken from living newborns. Or more properly, from the placenta, which is sort of … you know. Newborn-adjacent. Your friend is thinking of embryonic stem cells which, as I understand it, are indeed quite useful if you want to give someone a teratoma."
] |
[
"There are less sinister ways to attain embryonic stem cells. They can be taken from ",
"surplus embryos that were harvested for use in in vitro fertilization but never implanted",
". They can be used for awesome stem cells or basically discarded."
] |
[
"I was going to say the exact same thing, glad I read the comments before posting though"
] |
[
"Can the human ear adjust to volume?"
] |
[
false
] |
I’ve noticed that without changing the volume, I can go from barely hearing the tv to it being too loud. For example, I had to turn it to 15 (loud for our tv) to hear it at first, but after watching for a few minutes I was able to hear it fine at volume 3.
|
[
"Yes. Your brain will dampen constant levels of noise in an effort to make out important bits because it responds to ",
" in sound pressure levels. Sound Pressure Level refers to the acoustic pressure caused by vibration in a material propagating to nearby air molecules. SPL is its measurement, but the subjective “loudness” is what is important. Your ear works just like speakers and microphones in that it responds to pressure changes and the membrane of your inner ear must move in real time to determine what you are hearing. Your brain does the rest, giving way to understandable noise. How sensitive your hearing is is largely a function of the health of the tiny hairs called silica that line your inner ear. As the air travels further down the canal towards the center of the spiral it encounters these hairs with the ones near the ending responsible for lower and lower frequency responses (after all, lower pitches are longer wavelengths). This also means we lose our hearing first at the high frequencies because they get exposed to loud noises yet are there to pickup quiet ones. You can imagine what hearing damage can do to not just your ability to detect noise at all, but to allow enough data to get to your brain to determine what exactly you are hearing, where it’s coming from, and how loud it is; while the sensitivity to loudness dampens over time to the sensations of these hairs like any other sensation on the body."
] |
[
"Similar phenomenon occurs when one stands near a loudspeaker. It may seem unbearable at first, but gradually doesnt feel as loud. On mechanical level, this is controlled by the stapedius muscle in the middle ear. When it gets taught, the vibrations of ear ossicles dampen, and lesser vibrations are transferred from the tympanic membrane to oval window (which leads to inner ear, where follicles are), hence reducing the loudness we percieve. When it gets relaxed, the ossicles can vibrate more freely and we can hear the sound louder. I suspect there might be a cerebral mechanism to it too, but i believe it has greater role in helping us ignore sound than in controlling its loudness. \nEdit: decided to put a link to make it a little easier for anyone reading it ",
"https://en.m.wikipedia.org/wiki/Stapedius_muscle"
] |
[
"Yes it sure does, but is more important for sounds originating in pharynx and mouth, such as during chewing or swallowing"
] |
[
"Can Animals Have OCD?"
] |
[
false
] |
Have there ever been any documented cases of an animal showing similar traits of OCD? What about any other human disorders?
|
[
"Not really my area, but I just googled it and found this interesting ",
"article",
" on the neurological basis for OCD in animals. ",
"Here",
" is a news article where people observed mental illness like behavior in some Chimps. Animals experience emotions similar to humans and even dogs ",
"\"simle\"",
" when they are happy. "
] |
[
"Yes, dogs and cats can have OCD. It can manifest in over-grooming (such as licking, which can lead to inflammation of the skin), urinating, sucking, chewing, self-mutilation, hallucinations, or constantly chasing the tail. The last one sounds almost cute, but it really is somewhat heartbreaking to see a dog so anxious that he chases his tail and spins repeatedly to the point where he's wheezing and almost faint with exertion. Sometimes these conditions are treated with medication, such as Prozac."
] |
[
"My favorite animal from psychology is a Chimp who would read Cosmo, make tea & martinis and masturbate to human porn. ",
"http://en.wikipedia.org/wiki/Lucy_Temerlin"
] |
[
"How can DNA encode \"instinctive\" behaviour?"
] |
[
false
] |
When an animal shows behaviour we describe as instinctive, that is it was born "knowing" to do the behaviour, without training or learning, that knowledge has to come from it's DNA. But how can DNA do this?
|
[
"DNA codes for proteins. Proteins affects cell growth, migration, differentiation and control what other proteins will be expressed. Slowly you end up with an entire organism. Let's say it's a dog. That dog, with the help of expression, migration and differentiation control has develloped neuronal circuitry that has a specific response to a stimuli.",
"Example: Dog sniff something that is unhealthy for him. A molecule of that unhealthy stuff sticks to a receptor that is expressed in a particular olfactive cell. That cell is connected to a sensory neuron that, when activated connects to a circuit in the brain that will make the dog repulsed/disgusted. Dog does not eat and walks away. It's the first time ever he come in contact with this thing, but it knows he should not eat it. That's instinctive behaviour.",
"That whole circuit was formed and guided into place by the control of proteins, and proteins are made by DNA."
] |
[
"DNA codes for proteins",
"Not all DNA does. In fact only about 2% of DNA actually codes for proteins. Other regions include transposons (so called 'jumping' genes), others which serve important regulatory functions, as well as areas whose functions we're not entirely sure about. The point is that while the rest of the DNA was once thought of as 'junk' DNA because they did not directly code for proteins, today it is now very clear that they can be just as important in order to regulate transcription and translation and how the body responds to various biochemical signals as the proteins themselves.",
"Proteins are of course very important, however, as they are the molecular effectors that do the bulk of the work. For example in response to being pepper sprayed, your body elicits a lot of negative physiological effects that makes you want to shut your eyes and of course never encounter it again. The ingredient in pepper spray that causes this is capsaicin, which makes its way through the blood once you get sprayed and binds to the TRPV1 receptor in neurones and other parts of the CNS. The TRPV1 receptor is a protein and the binding of the ligand (the capsaicin) causes downstream signalling events, as the protein causes a response in other proteins and the entire cascade is what allows the various physiological effects to manifest."
] |
[
"You are right about the other regulatory functions of DNA. I didn't want to get into the details. I think though that for the layman, saying that DNA is a recipe for proteins and that proteins are tools to build, organize and maintain cellular prosseces and functions is an acceptable simplification."
] |
[
"Poisonous creatures: why do they live in warmer climates?"
] |
[
false
] |
As a Norwegian, we have like one species of snake which is poisonous and a couple of plants. None are lethal. Yet in other places such as Australia, or the different jungles, there seems to be hundreds if not thousands of fatal beings. Why is this the case?
|
[
"While I can't help you with your question, I can help you with your use of the word \"poisonous\". ",
"Poison is a toxic substance excreted by a living thing that is present in the tissues/skin and is usually used to deter predation",
"Venom is a toxic substance excreted by a living thing that is usually injected into prey/predators and can be used to either deter predation or help with hunting",
"Thus, toxic plants are poisonous, while deadly snakes are venomous."
] |
[
"Competition. Being poisonous is an advantage just as being able to survive the winter is an advantage. These are two different evolutionary strategies. Reasons for having less poisonous animals in the north may be due to the lower number of species ie less competition or that the extra energy going into poison is to much of a trade-off vs staying warm."
] |
[
"actually if the goal is survival doesn't less energy=more competition?"
] |
[
"Are there sounds that can be made by humans that aren't included in the alphabet of any language?"
] |
[
false
] |
What I mean is, is it possible that there are phonetical sounds that haven't been explored or covered in any alphabet around the world.
|
[
"There are some non-pulmonic sounds that aren't part of any languages inventory. Pulmonic ingressive sounds are especially rare, they occur in some dialects of Swedish. ",
"I can't of the top of my head think of a sound that isn't used in any language. "
] |
[
"There are lots of sounds you can make with your mouth that no language uses, of course. You can e.g. clack your teeth.",
"But if you're going for something more traditionally \"phonetic\", i.e. some sort of airstream mechanism and a configuration of velum, tongue, and lips, I can e.g. think of the linguolabial trill. Now ",
"linguolabial consonants",
" are made with the tongue and the upper lip. They can occasionally be found in natural languages. However, what is listed as \"linguolabial trill\" in the article is made with the ",
" lip, it's essentially a ",
"raspberry",
".",
"Now a \"true\" linguolabial trill is possible; instead of moving your tongue tip towards the alveolar ridge and making a trill there, you can actually move it all the way to your upper lip instead. It ",
"a) is entirely possible",
"b) uses a \"normal\" pulmonic egressive airstream",
"c) uses a place of articulation that can be found in languages",
"d) uses a common manner of articulation"
] |
[
"Usually the letters of a single language are quite vague. The pronounciation accepts multiple non-indetical sounds. This can code information about locale or subculture. It's easy to hear a japanese background persons r differing a lot form a westeners (because within japanese r and l are actually part of the same letter).",
"However for lingustics there have been made a kind of markup that is for the express purpose of having a way to mark down all kinds of quirky sounds in a non-language based way. Those that made it up / maintain it probably try to keep it very comprehensive. There are a whole bunch of words on what kind of mouth/throat trickery must be performed to come up with a particlar kind of sound.",
"For the more general kind of question parrots and such are pretty much abel to replicate any sound. While it is true our monkey relatives can't do vocal spheech mainly because their organs are not handy for those sounds, I do think human sound organs are not especially restricted. I would love to know wether there is qualitative differerence to the phonetic output and not just the anatomy of parrots and humans."
] |
[
"How do the center of planets/stars behave?"
] |
[
false
] |
Is the material in the center of planets and stars just held there by the pressure of everything above it. Is it "weightless" in the center of planets/stars? It seems counter initiative that there is more mass outside the very center point of a planet/star so shouldn't that gravity be pulling it apart all around and away from the center but at the same time all that mass is pulling itself inward because to an outside point there's more mass towards the center were the matter is being pulled and making that pressure that the center feels.
|
[
"Your intuition would be correct. The ",
"shell theorem",
" says that gravity from a hollow sphere of material will behave as follows: To someone inside of it, the gravity will cancel out. To someone outside of it, the gravity behaves in the same was as it would if all of the mass was concentrated at the center of the sphere. The result is that, if you imagine the planet as a bunch of concentric hollow spheres, you realize that as you dig deeper you find yourself inside of these spheres. This means that only the portion of the planet that is beneath you is pulling you down. When you reach the center of the planet, you are inside of every single sphere, and so you experience no gravity. If you were to hollow out the core of the planet, you would float around freely in this cavern."
] |
[
"\"If the body is a spherically symmetric shell (i.e., a hollow ball), no net gravitational force is exerted by the shell on any object inside, regardless of the object's location within the shell.\"",
"In other words, as long as you are inside of the shell, you will not experience a net force in any direction."
] |
[
"I believe for Earth and other planets this is isn't quitr true due to non uniform density. Theres a point between the outer core and mantle where accel due to gravity peaks about 10.5 m s",
" ",
"https://en.wikipedia.org/wiki/File:EarthGravityPREM.jpg"
] |
[
"Rosetta implications - other life forms in space?"
] |
[
false
] |
[deleted]
|
[
"Organic molecules have been detected in hundreds of different environments in space dating back to the detection of formaldehyde (H2CO) in 1969 in a variety of molecular clouds. Here, we can take \"organic molecule\" to mean anything with carbon, oxygen, and hydrogen. That is what the scientists and press releases from Rosetta are referring to when they say they have found \"organic molecules.\" As far I know, they've not been specific with which ones yet.",
"But I digress: even though formaldehyde is incredibly simple, we've detected far more complex organic molecules in sources in the interstellar medium (molecular clouds - the birthplaces of stars and solar systems). Things like hydrogen cyanide (HCN), methanol (CH3OH), water, acetic acid (CH3COOH), even glycolaldehyde, the simplest sugar-related molecule (CH2OCHO).",
"If you want to see a full list of these molecules, including where, when, and by whom they were detected (literature references!) you can find it at the ",
"Bibliography of Astromolecules",
" maintained at the ",
"www.astrochymist.org",
".",
"Now, that's just out in these clouds. What have we detected in meteorites? WAAAAY more.",
"Take the ",
"Murchison Meteorite",
", which fell in the late '60s, for example. It contains a slew of ",
"amino acids",
", literally the building-blocks of the proteins you and I are made of. And their isotopic composition gives definitive evidence that they are extraterrestrial in origin - meaning they were there before they fell to Earth! This and other samples have been found to contain dozens and dozens of different amino acids, sugars, and other life-essential \"organic molecules.\"",
"So, why are we excited by the possibility of there being \"organic molecules\" on Rosetta's comet? Well, because landing a probe on a comet and getting direct samples into a mass-spectrometer makes for a far more sensitive analysis than even our previous measurements of comets. The STARDUST mission detected glycine, the simplest amino acid, in samples returned to Earth from Comet Wild-2, but there was so little sample, it makes it very hard to detect anything else.",
"Here, we had hoped that the instruments on Philae and Rosetta, which wouldn't have to shoot the stuff back to Earth for analysis, would let us see things less abundant, but more complex, than glycine, and to determine isotopic ratios of things like water, CO, and CO2, which all have implications for where these things on Earth originally came from.",
"The presence of \"organic molecules\" does not in any way indicate the presence of life. Rather, as far as we know, the presence of these molecules is a ",
" for the presence of life. The molecules can form and react in a completely abiotic (lifeless) environment. But understanding how those reactions occur, and could LEAD to the formation of life, requires that we study them in all stages of their life cycles. We think the time they spend in comets may be an important step!",
"So, at least in my field, that's why we're excited that \"organic molecules\" were found on Rosetta's comet - it means that we might have the best chance yet to understand the chemical evolution of life-essential molecules in space! And yes, perhaps, learn something about the possibility of other life."
] |
[
"You probably don't want it. In space, it's commonly mixed with ",
"urea",
" (piss), ",
"ethyl formate",
" (raspberry/rum flavoring), and just straight up ethanol...",
"Along with a lot a lot of PAHs (",
"Polycylic Aromatic Hydrocarbons",
" - i.e. soot)."
] |
[
"Well, if you like to drink alcoholic bottled cancer, then yes, you could call it Space Liquor. "
] |
[
"Does the sensation of hunger come from the emptiness of our stomach or the lack of calories?"
] |
[
false
] |
[deleted]
|
[
"Motilin is a hormone released by M-cells in the stomach and upper duodenum of a fasting person. This hormone causes migrating motility complexes, a.k.a. peristalsis, to occur in the digestive tract in 90-minute intervals to ensure that the intestines are clear and ready to receive food."
] |
[
"The short answer is both, but the basic mechanism of action that each uses to stimulate hunger is related. One of the main players you'll read about in relation to regulation of food intake is ghrelin. Ghrelin is thought to stimulate hunger as circulating levels have been shown to increase before meals and decrease after. The exact mechanism for regulation of this hormone is not understood but is related to the nutritional state. So decreases in levels of blood glucose would cause an increase in ghrelin which acts in the hypothalamus and stimulate the desire to eat. ",
"I can't find literature that specifically says an empty stomach itself causes hunger. However, hormones normally released in response to the stimuli of eating (distention of the G.I. tract and increased concentration of amino acids, glucose, etc.) such as cholecystokinin and peptide YY that act to decrease hunger would be decreased when the stomach is empty. Hunger is a widely variable feeling that we all know ranges from \"yeah, I could eat\" to \"I'm literally starving\". As a side note, there are no less than twenty different compounds in the body related to regulation of hunger (anorexigenic / orexigenic)",
"Source: Hall, John E., and Arthur C. Guyton. Guyton and Hall Textbook of Medical Physiology. Philadelphia, PA: Saunders/Elsevier, 2011. Print. "
] |
[
"What causes that gurgling and rumbling feeling in your stomach when you're hungry? What's going on there?"
] |
[
"What is the most exotic element known?"
] |
[
false
] |
I just seen some stuff about anti matter and got to thinking. What is the most exotic element known to us? Bonus points if you can tell me a little bit about it. Chemistry has always been a sudo hobby of mine.
|
[
"Well, how do you define exoticness? The element with the highest atomic number we've currently discovered is Onganesson (Z = 118).",
"Some elements have some very exotic isotopes. For example, ones near or beyond the ",
"driplines",
".",
"You may not be aware, but hydrogen actually has 7 known isotopes, helium has 9, etc. Nuclear species at or beyond the neutron dripline have lifetimes around 10",
" seconds."
] |
[
"Every element has its own properties which makes it interesting in a way or another. They all have some \"exoticness\" if you allow the term. From hydrogen being the most common element in the universe to uranium with its incredibly long lifetime and to the many artificially made elements, which we do not find in nature.",
"There are currently 118 known elements, with most or all of them having known isotopes. Each of those has different physical, chemical properties. It's a lot of those.",
"Please tell me if I'm wrong, but you are basically asking for some mind-blowing facts about some random elements, right?"
] |
[
"Since your question is open to discussion you might open a ",
"r/AskReddit",
" thread in parallel to this one (with the \"Serious\" tag otherwise it's going to be weird).",
" ",
"I'll pick a cool one with ",
". We have a lot of Uranium on Earth, and all of it was produced by a supernova that happened long before our Sun even existed, i.e. more than 4.6 ",
"illion years ago. We know that because Uranium is so heavy it can only be produced by supernovae, and is in fact a direct evidence that long ago there was indeed a supernova that happened somewhere around us.",
"Uranium is unstable and decays into many other elements (radioactivity). But we still have a lot of it despite it being produced more than 4.6 billion years ago, which tells a lot on how long-lived it is. In fact, it is so long-lived that we can use it as a way to date stuff. Much like we can know how old objects are using Carbon 14, we can know how old our Sun is by looking at how much Uranium it contains. Same for many stars around.",
"I mentioned that Uranium decays into a lot of elements: ",
"here is the full decay chain",
". Basically, it keeps decaying into unstable elements until reaching Lead, which is stable. We have a lot of Lead in the Earth crust, thanks to the Uranium that used to be around. ",
"Uranium is radioactive, but the very long lifetime means that the number of decays per second (\"activity\") is small: you don't get bombed by a lot of particles and means you can stay around it for a while before having health risks. I have personally manipulated stuff around Uranium bars inside a nuclear reactor during a school project, but at the end of the day my dosimeter did not show a dose higher than natural radioactivity. I still would not recommend having a rod in your bedroom :)",
"I do not know if you have already weighted an object made out of Lead. It's heavy as hell, right? Well Uranium is even heavier. Which is why this element is used in some military applications (depleted uranium ammunition) : it's really dense, and due to its very long lifetime it's not very dangerous to have around for some time."
] |
[
"Steam as a solvent"
] |
[
false
] |
I know that supercritical steam can be used as a solvent, but does anyone know the effect on solubility of steam at different pressures and temperatures below the supercritical point?
|
[
"So, if your below the super critical point, your solubility should decrease as you are no longer acquiring liquid-like behavior, meaning that your losing how densely packed your system is (I'm assuming your dropping below the super critical point on the side of steam, rather than on the liquid side, otherwise you would reach the solubility properties of water quickly)"
] |
[
"Water's Phase Diagram",
"It's called a critical point (rather than a line) for a reason, particularly because it doesn't have a phase change associated with it, meaning that you dont see an abrupt change in it's propeties. This is what makes super critical fluids tricky, because they share both gaseous and liquid behaviors, and dont establish a phase boundary between the two. As this is the case, we would expect a gradated decrease in solubility(although probably relativelyt sharp decrease) as you went from supercritical fluid to steam. With boundries being determined by the maximum solubility of your supercritical fluid (something not to rough to look up), and with your minimum solubility being given by your gaseous state. But there would be no distinct \"drop\" as your not experiencing a phase change as you would normally describe it."
] |
[
"I know that solubility will decrease when steam is not super critical, I am wondering by how much, and does all the solubility go away at once, or does it gradually decrease as temp. and pressure decrease."
] |
[
"Exactly what is the process of determining a structure of a molecule using NMR?"
] |
[
false
] |
How does 1H NMR work? How do chemists go about finding out a completely unknown structure of a molecule they haven't seen before using just NMR?
|
[
"We use reference data and splitting patterns. The chemical shift of a particular proton is affected by its chemical environment and we have tables of the likely chemical shifts of protons in certain environments. For example, a CH",
" proton typically has a shift of 1ppm, but a CH",
" proton adjacent to -OH is likely to have a chemical shift of around 4ppm. Further, peak intensity can usually give the ratios of numbers of protons in particular environments - in the previous example the CH",
" peak and CH",
" peaks would have intensities in the ratio 3:2. Experience teaches you that when you see particular patterns of intensities at particular regions of the spectrum, you should expect certain functional groups.",
"The other big source of data in an NMR spectrum is the splitting pattern of a peak. This gives you information about what is near to a particular proton. So, chemical shift gives you an indication of what each proton's individual environment is, and the splitting pattern tells you how those individual environments are connected in the molecule. You've got a) the pieces and b) the way in which they're put together. Combining these bits of information (along with a bit of nous gained through experience) you can often completely assign structures from NMR results without having to use any other methods."
] |
[
"H1 NMR takes advantage of the spin states of (as the name suggests) hydrogen atoms. These atoms can have a spin quantum number of +1/2 or -1/2. Now under normal conditions these two states are degenerate (IE no determinable difference between the two), but the instance you put the hydrogen atoms in a magnetic field this is no longer true. A magnetic field causes one spin to be more energetically favorable than the other. Because of this energy difference you can now use electromagnetic radiation to flip the hydrogen spin states in the system.",
"Now the spin states alone aren't really enough to determine a molecule structure, but as it turns out based on where the hydrogen atoms are found on a molecule they experience different levels of shielding by neighboring groups. For instance if you have a huge electronegative atom such as oxygen attached to the hydrogen it is going to be experiencing a high degree of shielding. ",
"On the output spectrum this shielding corresponds to the signal peaks being ",
"shifted ",
" upfield. From this information it is possible to determine what kind of environment the hydrogen atoms are located in. Thus we can gain a lot of structural information about a molecule. In addition there is a peak splitting effect that you can take advantage of to figure out how many hydrogens are neighboring a given hydrogen. ",
"This can also be done on isotopes of carbon, fluorine, phosphorous, etc. Typically the most common ones are C-13 and H-1 since those are found in every organic molecule. The other atoms are more research field specific. ",
"If you have ever had an MRI you've actually been in an NMR machine. "
] |
[
"Check out ",
"this Youtube channel",
" for introductory videos on NMR.",
"NMR exploits the fact that some nuclei have a magnetic moment. By subjecting them to a large external magnetic field, it'll give rise to a population difference, where more of those magnetic moments prefer to point somewhere in the direction field rather than against. This results in a ",
". Magnetic moments precess when subjected to a magnetic field - this is called ",
"Larmor precession",
" - and by manipulating the net magnetization (through the use of radiofrequency pulses) and sampling the precession frequency, we can gather useful information.",
"In the simplest solution-state 1H-NMR, there are three pieces of information you can obtain from each peak: integration, ",
"chemical shift",
", and coupling constants. The integration of a peak tells you the relative proportions of protons that give rise to the signals. The chemical shift gives you a rough idea of the chemical environment of the protons - for example, alkane protons give peaks near the 1-3 ppm range, while aromatic protons have peaks near the 7-8 ppm range. Finally, the coupling constants tell you bonding information: protons in geminal (2 bonds away), vicinal (3 bonds away), and in some cases, 4 bonds away can give rise to splitting patterns in the peaks with the same coupling constants. This means you can match up those peaks and locate them - chemically - on the molecule. In addition, the coupling constants themselves also give further information on the chemical bonds between the protons - in an aromatic ring, for example, ortho-, meta-, and para- positions have their respective coupling constants. Furthermore, the ",
" of the peak will also tell you how many protons are involved in the coupling - one proton coupled to two identical protons will show a triplet.",
"When you move beyond the simplest 1D experiments, there are a number of other, more advanced experiments that can give you more information. For example, a correlation spectrum (COSY) can isolate the peaks that are coupled in a busy spectrum, while a Nuclear Overhauser effect spectrum (NOESY) can give ",
", rather than chemical, information of protons.",
"Edit: Added short background theory. It's difficult to summarize in short, but feel free to ask questions and I will gladly elaborate."
] |
[
"What properties make an object heat faster in a microwave?"
] |
[
false
] |
I have noticed that different plate materials will have very different reactions to being microwaved, as will different types of food. What properties make an object heat faster or slower in a microwave?
|
[
"This is 100% wrong, microwave photons have energies well below .001 eV nowhere near high enough to create free electrons from the PE effect.",
"Microwaves do not induct enough current to joule heat materials either so that is wrong.",
"Microwaves DO heat water molecules, but that is not the exclusive mechanism for heating things in microwave cavities. You can heat 100% dry materials as well if the material can couple with the microwave energy and begin heating through kinetic motion."
] |
[
"It has to do with the polarization of the molecules in the material. If they are strongly polar, then the EM waves from the microwave will have a strong effect. The polarity of water is the reason that it is heated by microwaves, not any resonance effect."
] |
[
"You are observing the dielectric properties of the various materials. Some materials like dry ice are transparent to microwaves and will not heat up in a microwave because it has low dielectric loss. Some ceramic plates and bowls have higher dielectric loss than others meaning they couple with the microwaves and begin to vibrate generating heat.",
"Metals reflect most of the microwaves but the surface layer can build a considerable charge creating sparks if the voltage is high enough to arc through air."
] |
[
"If precious metals and gems are found near impact craters, does that mean the moon is loaded with gold and diamonds?"
] |
[
false
] | null |
[
"Not really. The main issue is the composition of the moon. ",
"For instance, a lot of gold ",
"forms in the presence of water",
" (hydrothermal fluids). "
] |
[
"Diamonds are formed by carbon under immense pressure. That's it. That's all the equation needs... If carbon is under enough constant pressure for long enough the atoms will naturally align into a crystalline structure and form the diamonds we know. Yes it does need energy for the atoms to move, whether by heart or otherwise... But the point was that impacts create that heat and pressure required to form gems and crystals, and the moon was caused by a Mars sized planet impacting earth. So logically there should have been enough heat and pressure to create a ton of diamonds and other gems/precious metals that would be scattered on the moon..."
] |
[
"The leading theory on how gold in the Earths crust exists nowadays is by asteroid impacts in the late heavy bombardment era. If those are correct there should be gold on the moon. ",
"http://en.wikipedia.org/wiki/Gold#Occurrence",
"LCROSS detected gold in October 2009 during an impact test: ",
"http://www.pbs.org/newshour/rundown/its-confirmed-there-is-water/"
] |
[
"Another post read that we can achieve temperatures as low as 0.0000001 K in laboratories. At this temperature, can we view molecular reactions in real time?"
] |
[
false
] |
[deleted]
|
[
"Sort of. The technology to \"see\" molecules in the sense that we think of the word generally is too slow to watch things changing. Other techniques involving spectroscopy can observe things happening in real time (using very fast pulse lasers), but the results aren't meaningful if you're not familiar with spectroscopy. At ultralow temperatures a group managed to observe (spectroscopically) molecules changing from one type to another over the course of several seconds (",
"paper",
") which is akin to what you're talking about.",
"This",
" is a molecule rearranging itself as seen with an atomic force microscope. Those images take hours to make though. "
] |
[
"AFM really has nothing to do with light. It's not possible to image things that small conventionally with visible light. In a nutshell, AFM involves dragging an atomically sharp probe on a cantilever over a surface and measuring the deflection. In this case, non-contact AFM is used with a single CO molecule deposited on the end of the tip. In the constant height mode they used, the AFM tip is oscillated at the resonant frequency of the cantilever and scanned across the surface at at a constant height above the surface (not actually touching). Depending on whether the surface exerts a force (electrostatic, van der Waals, etc.) on the tip, the resonant frequency changes, producing the signal that is measured. So what you're seeing in the image is really a reflection of the local electron density. The paper says that the primary force that allows visualization of the bonds is Pauli repulsion.",
"So rather than being the equivalent of looking at a surface with one's eyes, AFM is akin to dragging a finger across a rough surface and feeling the topography."
] |
[
"In those images with atomic force microscopy, what data is being gathered? Is that actually light data or is it something else that was visually constructed using a computer?"
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.