title
list | over_18
list | post_content
stringlengths 0
9.37k
⌀ | C1
list | C2
list | C3
list |
|---|---|---|---|---|---|
[
"Why can't we put Cyanobacteria on planets to make them habitable?"
] |
[
false
] |
[deleted]
|
[
"Very broadly speaking, we can. I'd say there are three broad categories of issues with this idea:",
"We don't want to 'settle' a planet with our bacteria before we have an idea of whether there is pre-existing life. Knowing that there is life on another planet would be a huge discovery, and once you contaminate a planet with life from Earth, it is hard to prove that anything you find in the future isn't just something from that original contamination.",
"This planet in question might be very far away. How are we going to get cyanobacteria to that planet? And even if we did, how would ",
" get there to enjoy the fruits of its labor? ",
"Suitable temperature is just one of a number of variables that would be relevant to having happy cyanobacteria. They would need water, carbon dioxide, enough atmosphere to shield from radiation (and obviously enough to keep the carbon dioxide and newly formed oxygen around). ",
"I has the stoopids so if I'm missing something tell me!",
"I'd delete this part of your post. No one in ",
"/r/askscience",
" needs to place some sort of disclaimer on their question."
] |
[
"Cyanobacteria have been successfully grown in simulated-Martian conditions, so it's theoretically feasible, however with algae and cyanobacteria the problem is always scale and how things behave differently when scaled-up. A cyanobacteria colony grown in a jar does not necessarily indicate at all how it would grow ",
" regardless of how well you approximate conditions on other planets. Another reason we don't is cost; the cost of sending them to another planet, only to have nothing happen because they all die, is a pretty big gamble to take and a lot of work for nothing. But really it's the atmosphere that's the biggest problem for the reasons you describe."
] |
[
"We don't want to 'settle' a planet with our bacteria before we have an idea of whether there is pre-existing life.",
"To add one more point: it is (relatively) easy to introduce life to a planet. It is (relatively) difficult to eradicate life on a planet. Thus, if you aren't sure which you'd like to have, you'd rather be in the state (lifeless) that gives you the option of moving to either of the two possible states, rather than in the one (has life) that it's difficult to move away from."
] |
[
"If a males testicles are removed before puberty occurs does the male grow to be the size they would have been if the testicles were still there?"
] |
[
false
] |
To add to my question, would the removal of the testicles before puberty cause the person to be uninterested in sex after they would have otherwise gone through puberty?
|
[
"I can't quite say much with regards to humans, but as an owner of ferrets one of the interesting facts about them is all ferrets in, at least in Canada, legally must be Spayed/Neutered.",
"This has interesting side effects, as the operation is done when the ferret is very young. One effect that has been documented well is the ferrets go through significant changes in growth and behavior.",
"Young ferrets are far more social, friendly, curious, and less aggressive. As they mature normally, they become more food dominant, aggressive, and of course sexual with each other. Normal growing ferrets will become seclusive as well.",
"However, if Neutered/Spayed, they don't go through these changes nearly as much. These ferrets, which are called 'Sprites', will basically stay in their childlike phase (temper wise) for effectively forever.",
"They also don't grow as big, and stay social. Sprites are much more cuddly, they are perfectly fine cuddling together in piles (behavior normally only seen in baby ferrets), and they continue to be playful and non-aggressive for their entire life span.",
"Now, since Ferrets and Humans are both Mammals, I wouldn't be surprised if similar phenomena occur with us as well."
] |
[
"To the “uninterested in sex” question: I took a course called “Sex and Endocrinology” and one class we had a discussion about the ethics of whether sex offenders (rapists, molesters, etc.) should be required by law to take either a pill or injection to stop the synthesis of testosterone (T). As of right now they have a choice whether to take them or not (consent is required). For males: blocking, or inhibiting, T from being formed and reacting with receptors does decrease sexual desire, erections, and wet dreams (there are research articles about this, I’m not sure about the data on females), overall they feel less inclined to preform sexual acts. Therefore, removing the testicles and stoping a large amount of T production will most likely decrease sexual desire. If they are removed, injections of T can “replace” the testicles’ function, if so desired. ",
"Edit: there are many sex studies involving mice that are interesting and dives in much deeper on this subject. If you are interested, I suggest going to Google Scholar to find research articles about this. Have fun learning and discovering :)"
] |
[
"I am by no means an expert on this subject but I read in a book titled \"Mutants\" by Armand Leroi that \"Boys that are castrated before puberty grow up to be tall\"( page 199) and also discusses the Italian Castarti who where a troop of singing men that where castrated. The entire book is a fascinating read about deformity.",
""
] |
[
"Could an asteroid have an atmosphere?"
] |
[
false
] |
Can relatively small objects like asteroids have atmospheres, provided that they were massive enough to have the necessary gravitational pull to keep said atmosphere from escaping? Is there a lower limit to this? Could an object the size of a basketball have an atmosphere?
|
[
"If the gravity there isn't strong enough it'll just float away."
] |
[
"It is possible that the largest asteroid, Ceres, has a very sparse atmosphere. We will know more when the Dawn probe arrives. Most of the asteroids are too small to have an atmosphere. The second largest, Vesta, does not."
] |
[
"If Ceres doesn't have an atmosphere, could we provide one by, oh, I don't know, opening a cylinder of massive gas? (",
" 6 for example?)"
] |
[
"Biologists say that humans have 10x more bacteria in their body than human cells, but how can this number be possible?"
] |
[
false
] | null |
[
"Bacteria are much smaller than human cells, roughly 1/10th the diameter in size. Imagine a cantaloupe compared to a blueberry or a grape to get a rough idea of their relative sizes. There's a very large population of bacteria living in your gastrointestinal tract, which is where that 10x number usually comes from. By weight bacteria still only make up around 1-2% of your body mass."
] |
[
"If I remember correctly, roughly 30% of your excrement during a bowel movement is bacteria. But technically, that's not inside your body. Bacteria inside of your body is a serious infection. ",
"We are a flesh tube with a mouth at 1 end, an anus as the other. Food is never ",
" of us."
] |
[
"Well, a 10 cm sphere is 1000x larger than a 1 cm sphere, so I thought it fit pretty well as a rough comparison."
] |
[
"[Medicine] Is there a scientific reason why medical personnel will tell someone in a critical state to \"stay with me!\" or similar requests?"
] |
[
false
] |
You see this all the time in the movies, and I once talked to a guy i met at a pub who said he was a paramedic and told me that sometimes patients will just "let go" and die, and that you have to WANT to survive. I was wondering if there's any medical/scientific literature about this effect. Why ask a patient to "stay with me" or "stay awake"?
|
[
"On the whole, we really don't do this. In fact, we often do the opposite and actually put the patient to sleep. A critically injured individual arriving in the resuscitation room may be semi conscious, agitated, and unable to lie still for procedures or scans; worse they may not be able to protect their airway and be at risk of food going down the windpipe into the lungs. In these circumstances we will give a general anaesthetic as an emergency procedure, and keep the patient sedated while the resuscitation continues.",
"There may be a role for trying to keep someone awake before the patient arrives at the hospital on the basis that a conscious person is usually easier to manage than an unsconscious one. However, the factors that cause a critically ill patient to slip into a coma are things like bleeding into the brain, massive blood loss, low oxygen levels and the like. These are not problems that are readily reversed by verbal encouragement, however enthusiastic."
] |
[
"This question came up in a first aid class I recently took. The answer was that it was strictly to make it possible to observe symptoms.",
"Symptoms such as blurred vision, dizziness, nausea, loss of speech, and anything the patient might bring up can all be indicative of different problems and you can't diagnose them if the patient is passed out."
] |
[
"This is just my speculation, but I think that this is probably done more often \"in the field\" (outside of a hospital) than actually in the hospital.",
"I've reasoned that one reason it's done is to stimulate a patient and therefore generate more sympathetic tone (the part of your nervous system that kicks to give you the \"adrenaline rush\"), which will generate more hormones to keep the heart contracting well and blood pressure up. ",
"If you fall asleep, the sympathetic tone decreases and the reverse happens: your heart contracts less forcefully, it beats slower, and your blood pressure goes down.",
"In a critically ill patient, you generally need to keep the blood pressure up so that the organs (like the brain and heart) can receive adequate perfusion. If they don't get enough blood flow/perfusion, they'll fail and the patient will die.",
"Maybe I'm wrong, but it makes sense to me. What everyone else says makes sense too."
] |
[
"Is it possible to develop our night vision?"
] |
[
false
] |
Let's say, if someone is locked in a dark room during several months (with food & water), and then gets out, would his eyes be able to see in the dark at night? I read somewhere that when you stay a long time (months..) in the dark, it could take at least 1 day for your eyes to be able to see in bright light. Does it mean that your eyes can still see perfectly only at night, so that it's possible to develop your night vision? Maybe I'm totally wrong, I would like some thoughts/facts about it. Thank you!
|
[
"It is not that easy. While our eyes do in fact get used to seeing in dark places it won't be easy for them to see perfectly. We have a series of light sensitive cells inside our eyes. Some of them get \"burned out\" when looking at bright light, but they quickly heal when no longer exposed to light. This causes us to \"get used\" to dark places. While they may take even a day to get completely healed, there can be no further improvement in their work after that.",
"So long story short: not really."
] |
[
"Since mutation is COMPLETELY random, this could take antwhere from a single generation to millions of them. This is a common misconception that living in certain conditions will actually somehow affect the outcome of gene mutation, but the only thing it can change is how often can it happen."
] |
[
"Only if that advantage actually helps... If they're in a mansion filled with food and genitals, and nothing for them to fall to their death off of (or otherwise get harmed), then it wouldn't really change one way or another. Also, if the members of the group who can see better feed and protect the others, who do productive things around the base camp (not in my mansion example anymore), then there still wouldn't be any selective pressure.",
"Or I might be completely wrong. I'm a wild speculationologist, not a miracle worker!"
] |
[
"What are the solar eclipse glasses made from?"
] |
[
false
] |
They were reasonably priced, but in the UK not many people are bothering to stock them as it's only a partial eclipse. They're upwards of £40 now online, and there's no guarantee that they'll get here by Friday. I actually have some glasses of my own from the eclipse 15 years ago, as well as using a floppy disk which is opaque under normal circumstances. What are these things made from? I understand that looking at the sun unprotected is a stupid thing to do, but there must be a simple solution to make something filter out UV rays. Something simple that you can stick them in a pair of cardboard frames and sell them en masse for people to stare directly at the sun with.
|
[
"It is a very bad idea to try to improvise solar viewing filters. There are certain wavelengths in the NIR range that the lenses in your eye will focus but the rods/cones in your retina are not sensitive to. It is possible to do severe damage while looking at something that does not even seem overly bright."
] |
[
"It is possible to do severe damage while looking at something that does not even seem overly bright.",
"Comparable to not feeling exposure to gamma rays from radioactivity and hence not seeking safety before the vomiting sets in (and such)."
] |
[
"I've discovered that the silvery glasses are most likely made form Aluminised Mylar film, which reflects up to 98% of the light hitting it. £5 for a 1m x 1m square.",
"Someone must know what they're constructed from, because they're essentially plastic film and cardboard and definitely do not cost £5 to make. There's a closely guarded gimmick, and I want to find out what it is. Some people even say welding glasses are unsuitable, so expensive PPE equipment is trumed by these things you get free with astronomy magazines.",
"How could someone be able to measure UV radiation through a material?"
] |
[
"If I swallow a large piece of food, will I still digest all of it?"
] |
[
false
] |
I've have some idea how food moves around inside the body and some about the timeframes, but I've no idea of the capabilities and mechanics of the system. Are large pieces of food broken into smaller pieces chemically somehow and then digested? Or does digestion happen layer-by-layer, no matter the size of the object? If so, will it just continue until it's all gone?
|
[
"Digestion has a few phases. Your mouth begins the first part, where saliva breaks down starches. The stomach is next, which has two primary methods of digesting food: acid mostly kills bacteria, but does help to break down the structure of food. Pepsin is a very active digestive enzyme in the stomach that is activated by the acid. Primarily though, your stomach is a muscle, and churns the food to break it into pieces. Big chunks of food simply won't proceed out of the stomach after this: if you swallow a big piece of meat whole, it will slowly break apart in your stomach and won't move as a chunk into the intestines.",
"Your intestines are where the \"real\" digestion occurs. Bits of food (at this point called \"chyme\") are squirted through the pyloric sphincter into the intestine. Here is where we see real protein and fat digestion occur. Most nutrients are actually absorbed within the first foot of the intestine, fats take longer and are broken down and absorbed over the first few feet. The small intestine are where the primary enzymatic breakdown of food occurs; the stomach is mostly a preparatory step but is not a good environment for most protein activity (because it is so acidic)."
] |
[
"This is spot on. I'd highlight that digestion occurs both mechanically and chemically to break something down from the size of food you eat to the size of individual molecules that can be absorbed into the bloodstream and/or lymph.",
"Just mechanically breaking food into smaller pieces is not typically enough to enable it to pass into your body proper from the digestive tract. The chemical component of digestion helps to dissolve fats into the watery mixture, then breaks them down, along with complex carbohydrates and proteins, into simpler structures that can be absorbed."
] |
[
"This is a good question!",
"An educated guess is that it would take a bit more time to digest, and the extra calories would be stored as fats. The digestive system has evolved to eke as much nutrition out of food as it can.",
"If calorically useful food was expelled as waste, obesity would probably not exist, since the body would only take as much energy as needed. That said, the body doesn't do that: it takes whatever it can get and stores the reserve for when less is available."
] |
[
"What would happen if a GRB shot off and passed through a black holes event horizon."
] |
[
false
] |
If a GRB goes through an even horizon of a black hole, is it sucked away or can it go through?
|
[
"The event horizon is the absolute limit beyond which nothing can escape. Geometrically, there are no paths which leave from inside the event horizon. Gamma rays are just part of the electromagnetic spectrum and don't behave any differently from light in this case."
] |
[
"A gamma-ray burst is just a flash of very high energy light, and just like any other light (or anything else for that matter), it can only cross the event horizon in one direction. Once inside, it stays there."
] |
[
"Black holes don't suck. The radiation falls into the black hole or is lensed around it."
] |
[
"Can gravity be altered on specific objects?"
] |
[
false
] |
[deleted]
|
[
"By taking a reasonable guess at OP's level of understanding about gravity from their text, starting the conversation with Einstein's field equations would be at best useless and at worst damaging.",
"First you need to understand how gravity relates to mass. This rough concept doesn't change when moving to general relativity, so even if the mathematical expressions change, the intuition that was built up is still of value."
] |
[
"As the gravitational effect of an object is tied to its mass, you can only alter the forces by changing the mass. While not at fancy as some of the concepts you propose... consider trying to lift a gallon of milk: If you drink some of the milk, the remaining milk in the gallon container is easier to lift as the Earth is pulling on it with less intensity.",
"This is quantified by Newton's famous equation for gravitational force,",
"where F is the force acting on the mass m caused by the other mass M. The intensity of the force is then related to how close together they are and some constant we call G.",
"Conversely, using a ",
"torsion balance",
" you can measurably detect that smaller lead weights attract each other via gravity less than bigger lead weights."
] |
[
"Newton's equation only describes how \"gravity\" works. It does not describe the actual force and why it works as it does. Einstein got a lot closer to it and his equations take over in situations where Newton's don't work, such as describing the orbit of Mercury. ",
"But even that doesn't describe the \"force\". To answer the OP's question, is it possible to build a gravity shield or gravity generator, we don't know. ",
"If such a thing were discovered, it would be one of those, change the course of human history type of discoveries. "
] |
[
"The temperature outside is below freezing (~28 F) and it is raining. Why isn't it snowing?"
] |
[
false
] | null |
[
"I prefer visuals and a bit more science behind what type of precipitation to forecast during winter events.",
"This is a skew-t log P diagram",
" for a sleet event in Wilmington, Ohio on January 17, 2004. A weather balloon was launched and this shows the temperature, dewpoint temperature, and wind speed and direction as it ascends into the atmosphere. I highlighted some important lines. Red is temperature, green is dewpoint temperature and how they change as the balloon ascends in the atmosphere, light blue is a constant line where everything to the left is below freezing and everything to the right is above freezing. ",
"At the surface, the temperature is well below freezing at -5C whereas further up in the atmosphere we get an inversion. Normally temperature decreases as height increases but here the opposite is happening. Between the two yellow lines at about 950 meters above the ground and 1950 meters, the temperature is above freezing making a perfect melting layer of about 900 meters deep before the temperature drops below freezing again. The red and green lines are fairly close together showing a nice and saturated atmosphere perfect for precipitation. Further up in the atmosphere a region is highlighted between two dark blue lines showing where the prime area is for ice crystals to form and begin to grow as they descend.",
"The warmth and depth of the melting layer combined with the depth and temperature of the freezing layer below it play a major role in determining precipitation type. The warmer and deeper the melting layer, the more likely freezing rain is possible, especially if the temperature near the surface is just below freezing while in this example, the melting layer isn't too warm and the freezing layer below it is perfect for sleet. If a melting layer doesn't exist, than snow is the likely form of precipitation. ",
"More information is available from the ",
"NWS office of Louisville, KY",
" on forecasting precipitation types. Sorry I wrote this fairly quickly and this is a topic that easily takes a semester to cover. "
] |
[
"In all likelihood, it's not that cold where the rain is forming. Freezing rain frequently happens when there's a warm front - so warm air is aloft but the cold air is trapped near the surface. So the droplets start as pure liquid - then they fall through the cold layer, and become supercooled. They don't actually freeze until they hit the ground."
] |
[
"http://science.howstuffworks.com/nature/climate-weather/atmospheric/question302.htm"
] |
[
"Does E=mc^2 apply to dark matter/energy?"
] |
[
false
] |
In referencing the new Planck data, people keep citing that a certain percentage of our universe is dark matter, while another percentage is dark energy. If energy can be converted to mass by E=mc and at least some mass is matter, then how can dark energy and dark matter be quantified separately? Does the equation only work on "normal" matter?
|
[
"There appears to be a source of mass we cannot observe, other than that we don't know much about it. We know it is there from the \"extra\" gravity coming from what looks like empty space in galaxies. We call this \"dark\" matter simply because it does not interact with light.",
"The expansion of the universe as a whole seems to be speeding up, and we cannot account for where the energy for it to do so comes from. We call this \"dark\" energy.",
"These two things are not directly related."
] |
[
"If energy can be converted to mass by E=mc2 and at least some mass is matter, then how can dark energy and dark matter be quantified separately?",
"Energy cannot be ",
" to mass -- rather, mass is a ",
" of energy. All mass has energy.",
"What they are saying is, some percentage of the total energy of the universe is in the form of dark matter (which means, the rest mass of dark matter) -- about 25%-ish -- and some other percentage of the total energy is in the form of dark energy (the form of which is not yet known and is not observable, hence the \"dark\") -- about 70%-ish. The remaining 5% or so is in the form of ordinary matter (rest mass of ordinary matter).",
"Does the equation only work on \"normal\" matter?",
"No, the equation works on any form of matter. It is not the full equation however. The full equation is:",
" where p is the momentum",
"The shorter formula only applies for objects at rest. When an object is at rest, its momentum is zero, so the second half of the equation is zero, and it reduces to ",
"."
] |
[
"To expand on Moltencheese's comment:",
"We have a rough estimate of the amount of visible matter in the area of the universe we can observe. This also accounts for 'normal' energy",
"Based on its gravitational effects holding galaxies together, we can roughly estimate the amount of extra mass there is in the form of Dark Matter.",
"Based on the movement of galaxies away from each other continuing to increase, we can roughly estimate the amount of dark energy based on how much normal energy it would take to cause that acceleration.",
"As to E=MC",
" being true for these, yes, ",
" that we understand what's going on correctly. Dark Matter ",
" be an unknown effect of gravity at certain scales, and I am not certain what the current state of that hypothesis is. ",
"But we understand dark energy even less. Sure, we can measure its effects, but is it really an active energy in the sense that we mean energy? We don't really know, because we can't manipulate it at all. We are currently stuck passively observing its effects, and comparing to what we know of classical energy to measure its 'amount'. E=MC",
" may be an utterly meaningless relationship to what we call dark energy, as it could just not be represented by any of the terms above. But maybe DE can be counted as a 5th 'force', at which point E=MC",
" would be entirely accurate. We just don't know.",
"And the above is from my knowledge gleaned from laymen-friendly papers. Someone with a more esoteric knowledge might have more insight, or even contradict what I said."
] |
[
"Are non-ferrous metals affected by magnets or magnetic fields at all?"
] |
[
false
] |
I know the short answer is no, that only ferrous metals interact visually with magnets (i.e. paperclips being stuck to magnets). My question though is that are non-ferrous metals such as aluminum, copper, mercury, etc affected by magnetic fields at all? If so, what are the effects?
|
[
"I know that in certain minerals, they can be diamagnetic or paramagnetic, depending on electron states and compositions, but they very rarely hold an induced field, rather the electrons will align with an induced field, but immediately go back to having a more or less random alignment after the field is removed. \n\\not an expert in magnetism."
] |
[
"Diamagnetism and paramagnetism are still interactions, just at a much lower scale than ferromagnetism. ",
"Here's a frog being levitated in a strong magnetic field through diamagnetism.",
"Edit: also, note that it's not just iron that experiences ferromagnetism; nickel and cobalt also are ferromagnetic."
] |
[
"Wikipedia and Google will have the answer for you (as will your library), but I can sum it up a bit.",
"Diamagnetism - Applying an external magnetic field to something that is diamagnetic creates an opposing field within the material. Usually considered \"non-magnetic\".",
"Paramagnetism - Magnetic spins within the material have enough thermal energy to randomly change direction, thus creating a net magnetism of zero. Applying an external field to this will cause the spins to align but as soon as it is turned off, the spins go back to being random.",
"Superparamagnetism - Similar to paramagnetism, except that the spins are all lined up but they flip to the opposite direction faster than the time it takes to measure, so the average magnetization appears to be zero. Applying an external magnetic field generates magnetism (aligns the spins). It cannot hold the magnetism without the external field.",
"Ferromagnetism - Your standard magnetism. Spins are aligned without an external field and can hold the magnetism. Can be found in many materials, not just iron.",
"Ferrimagnetism - Very similar to ferromagnetism but the spins are not exactly aligned. Most are aligned but some are anti-aligned. Resulting field is less than what would be expected. Magnetite is a good example of this.",
"Antiferromagnetism - Neighboring spins are anti-aligned. Net magnetism is zero without an external field. Magnetism can be induced if there is a strong enough external field and energy put into the system.",
"Superparamagnetic, ferromagnetic, ferrimagnetic and antiferromagnetic materials will become paramagnetic above a specific temperature called the Currie Temperature (Néel Temperature for antiferromagnetism). ",
"The theory as to why these various magnetism come into existence is a little long and complicated to write out right now. I suggest pulling up a book or website about magnetism to really understand how neighboring spins can effect each other to create the magnetism you observe."
] |
[
"Why do we feel emotions more strongly in the chest?"
] |
[
false
] |
Or more specifically, the heart. For millennia, humans have associated loss, love, fear, grief and even rage with the heart. Why is that so? If the brain is the seat of consciousness, shouldn't we feel emotions more strongly in our heads? What gives?
|
[
"We don't actually know 100%, but the best theory seems to be that increased stress hormones cause some rapid changes to happen in the body. A wave of feedback floods the nervous system, raising heart rate, forcing the stomach and several 'less essential to immediate survival' organs to shut down. ",
"The vagus nerve",
" is a very large, complex network of pathways that wind all through the guts and chest. It appears to be a combination of the rapid change in heart rate, organ function and stimulation of the Vagus nerve that causes what our brain interprets as pain in the stomach/chest."
] |
[
"Finally, my time to shine!",
"Scientist here - I study the brain-heart connection and am using it to try and find some objective / 'uncheatable' ways to assess concussions. The vagus nerve does generally control parasympathetic states, however, the innervations to the heart and carotid artery monitor your blood pressure, and the CO2 levels in the body. ",
"The hippocampus and vagus outputs are strongly associated (you do most of your thinking in a parasympathetic state). Conversely, the amygdala can act as a primer for a sympathetic response. Research into sympathetic responses (in this case exercise) and blood pressure - blood flow regulation has shown a slight 'uncoupling' where the brain can no longer match blood flow and pressure beat-by-beat. ",
"Hence, when you are extremely emotional, it is thought that these same mechanisms are influencing your vagus' monitoring capacity (albeit in different ways). Thus you can feel you blood pressure regulation challenges, which are likely being driven by the combination of your deep sobbing breathes, mild head tilt challenges, etc."
] |
[
"Vagus is part of the parasympathethic system, which does the opposite of what you've said. Sympathetic system is responsible for increased heart rate, bowel movement and secretion inhibition and vasoconstriction, muscle vasodilation etc. ",
"It's true that all this happens in intense emotional states."
] |
[
"how is anxiety related to gerd?"
] |
[
false
] | null |
[
"Chronic conditions typically have a negative impact on a person's daily life as they have to constantly manage it. Reduced quality of life can easily lead to anxiety and depression. I don't think there's a lot of evidence that hyperacidity directly causes changes in the brain that would lead to anxiety."
] |
[
"It’s possible that changes in the gut flora contribute to mental disorders by causing chronic inflammatory activation of the immune system. I don’t know to what extent, if any, GERD affects the gut flora."
] |
[
"GERD is not the same as hyperacidity. GERD is the refluxing of gastric contents into the esophagus. Lowering the acidity of stomach contents can help to relieve things by making the stomach acid less irritating to the esophagus, but the root cause is the reflux itself.",
"Anything which increase gastric pressure like spicy food, or \"butterflies\" ie anxiety can increase that pressure and cause reflux.\nLaying down also allows gastric contents to move to the esophagus since it isn't fighting gravity.",
"Signs of GERD are: worse with some foods, worse laying down (some even sleep in sofa chairs)",
"This differs from gastric ulcers which are not affected by posture, and feel somewhat better after eating.",
"Drugs to promote gastric emptying and directly decrease reflux have had some problems, so most first line GERD treatment is to raise gastric pH."
] |
[
"Are baby teeth more susceptible to tooth decay than adult teeth?"
] |
[
false
] | null |
[
"Yep! Mostly because children don't really brush their teeth the proper way... Babies are susceptible to tooth decay because of drinking milk from bottles. Milk contains lactose which is a disaccharide derived from glucose and galactose and the bacterial plaque metabolizes it resulting in the accumulation of organic acids which demineralize the enamel. In this case, the teeth which are affected the most are the maxillary frontal incisors. "
] |
[
"wow thanks. how did you find this question?"
] |
[
"cool. So I'm guessing you're some bio genius?"
] |
[
"How do instincts work?"
] |
[
false
] |
I watched a documentary called The Queen of Trees which focused on the relationship of fig wasps and a fig tree. A wasp will lay eggs inside a fig, and when the eggs hatch the new wasps know to grab some pollen, head out and find another fig tree. How do they know what they are supposed to do? They couldn't have learned it because they have never seen another wasp collect pollen or find a suitable fig.
|
[
"Essentially, from what I understand, the wasps do not \"know\" to do this. Through the long evolutionary timeline, the wasps who laid their eggs in figs were the ones with a better chance of survival. In the same way, the young wasps who grabbed the pollen right out and went to the other fig trees also for whatever reason had a better chance of survival.",
"In the long run, the wasps who laid their eggs in apple or olive or pine trees tended to die out due any number of factors (predators, lack of food, climate) while those who chose the figs survived to fly another day. Over a very long time, the fig wasps were the only ones left and their offspring were also drawn to fig trees for one reason or another (color, smell, etc.) that has been engrained in their little wasp subconsciousness.",
"Those with more knowledge feel free to correct me. "
] |
[
"Instincts as you describe them are simply very complex interactions of lots of simple instructions. Take for example the instinct to open your eyes. It is easy to understand that one neural pathway exists that rewards any stimuli from the eyes, hence making you want to open your eyes. Let's make that instinct more advanced and say that the reward only occurs, or at least occurs more strongly, if the eye is looking at something brightly lit. Now assume that the brightly lit object must be oriented upwards (now we're involving the inner ear). Now assume that the reward will be greater for multiple bright objects separated by darkness. Now assume that the reward would be greater still if bright spots amidst darkness located above us that happen to be in a particular pattern give even greater rewards and dopamine release. Taking one simple pathway and layering on, and interacting with, many other pathways creates complex behavior. It's fascinating that some birds can be born and raised without ever seeing the night sky, yet as soon as they see the stars they have an urge to migrate in the correct direction. It's important to realize that instincts aren't just one set of instructions in a program that is mysteriously handed down. Instead they are a very specific and complex interplay of neural pathways. Imagine if no one ever taught you about sex, it was just you and someone of the opposite sex on an island. Eventually, just by following simple nerve impulses you'd figure out sex. Once you had sex you'd feel the reward that following instincts gives, but it's probably going to take you a few learning steps while your neural pathways honed in precisely."
] |
[
"It's a pretty good answer, but there need not be other populations of wasps trying other fruits. All that is required to get a species of wasps on the path to exhibiting this behavior is for one momma wasp from some population somewhere to select fig trees as there egg laying location instead of what that species normally uses.",
"That was step one. :) If you like, I can go through the hypothetical later steps"
] |
[
"For the Chemists and Chefs of /askscience. Does a certain range of heat cause butter to homogenize with water?"
] |
[
false
] |
Simmering my Rice-a-Roni, after sauteing the dry mixture, initially produced a noticeable sheen of oil droplets on the surface of the liquid. After a little heat and stirring the mixture seemed to homogenize. This cloudy state remained briefly until my future meal suddenly "sprang up" the oil beads across its surface once again followed shortly by a uniformly faster boil. Does the heat cause the mixture to homogenize briefly, or is some other interaction responsible for this result. Of note the stirring was brief and the oil separation seemed unrelated to the agitation, more immediately preceding the faster boil. I tried to take a quick video on my phone but the reaction was cycling more rapidly and the steam quickly condensed on the camera lens. A keen eye should be able to note the change if requested. Edit: Prepared with sweet cream, salted, butter; not margarine. Pitcher filtered water, and name brand Rice-a-Roni were used if that helps.
|
[
"Butter consists of butterfat, milk proteins and water. The butterfat is the fat from milk. This fat is a triglyceride which a molecule made up of a polar section the head, and a long tail that is nonpolar. The nonpolar tails are much larger, and nonpolar molecules don't dissolve in a polar molecules like water. So no."
] |
[
"Cook here since you asked. I don't know about the science of it but I can tell you that if you have two liquids that do not normally mix (e.g. oil and water) and you whisk or stir like mad, you will form what we call an emulsion (which may not be scientific name) which is an even mix of both. For example we would say mayonaise is an emulsion of egg yolk and oil (with a bit of vinegar, garlic etc to taste). An emulsion will last for only a short while until it naturally separates. Unless you purchase pre-made mayo in a jar, whch has who the hell knows what robot piss added to it, to make it last. ",
"edit We don't have ricearoni here. Pasta is easy to make. 1 egg yolk and 100g of flour, knead like crazy, plastic wrap it, put it the fridge for 30 minutes to firm up, roll it, cut it, cook it.",
"edit egg WITH yolk"
] |
[
"Interesting, there was certainly a delay between stirring and the separation of the oil and water. Speaking from my limited knowledge of chemistry liquids and gasses have very similar properties. Would the water being on the edge of reflux put the water/oil mixture into a state of excitement closer to a true gas and thus suspend the lipids in the water solution longer? "
] |
[
"Silly question from a non-science guy: Are there folks who actively research/test/explore what are already held to be rock-steady theories?"
] |
[
false
] |
[deleted]
|
[
"Sure.",
"Experiments are often repeated. Either as a teaching tool or because someone thinks they have a new angle/technique to test something or because equipment has gotten more sensitive and an experiment can be done to a greater degree of accuracy.",
"It is quite common for \"settled\" science to be re-tested."
] |
[
"That's a GREAT question, not a silly one.",
"I think there are two types of answers in physics:",
"What is the value of science if nobody cares about the results? If the results of one study are not used in another, it's pretty much worthless in the first place, no better than the answer to a trivia question. If the results have ",
" sort of relevance, similar experiments will be performed in the future and those results will be built upon. There are many well-known cases of scientific fraud. For example, Jan Hendrik Schoen published a number of fradulent results about a decade ago and was found out when other scientists tried to reproduce his experiments. A lower profile instance recently came up in my own research where interesting results were obtained in the literature but couldn't be replicated with modern equipment (nobody is accusing these guys of fraud -- they were making an indirect measurement and the data seems to speak for itself, but apparently they should have been more careful).",
"There are some people who try to measure physical constants as accurately as possible, to see if they're changing in time or space, or maybe for other reasons. NIST is one place where this gets done a lot.",
"But as for the way you've worded your initial question, if someone COULD come up with a way to disprove a law of thermodynamics, that certainly would have a huge impact on their career. So the incentive is certainly there for people to come up with groundbreaking experiments -- but the question is whether or not these things are actually likely to be demonstrated."
] |
[
"Science builds on itself. In order to make the next step, you need to repeat methods used for previous theories tons of times.",
"For example, I'm working on the receptor for a pathogen. The initial work in the field was done back in the 1950s, everyone in the field for the last 60 years has copied what worked in order to refine theories."
] |
[
"How much can our muscles \"memorize? And for how long?"
] |
[
false
] | null |
[
"Unfortunately not. Muscles don't have the capacity to store commands, but your brain is incredible at optimizing things that are common to your everyday life. ",
"Language, walking, holding a pen (or anything for that matter) are all learned skills and thus are not automatic skills, but your brain would have optimized them so well they feel automatic. although language isn't a motor skill, it is a process that can impede the 'automatic' recall of a motor skill, which is a demonstration that memory is not stored in the muscle. ",
"As an experiment, count the number of laps you can do around your living room/table at regular walking speed, then have a relative or friend ask you a simple list question and record the number of answers you provide.",
"When you combine both exercises, both your cognitive recall abilities and motor abilities will suffer (you will walk slower and take more time to answer).",
"When you create more complex actions, your brain will begin to group motions or actions together in order to remember it as a single action because there is a limit to the number of actions or items in a list/task your brain can remember (I think neurology refers to it as the rule of 7). That is, you can remember 7 + or - 2 items.",
"Incredibly, the brain doesn't differentiate between groups or single things, so 5 6 7 6 3 could be 5 numbers in a list of 5 or 56763 can be 5 numbers in a list of 1 with practice.",
"In a basketball shot, you can set - up, flex your hamstrings and dorsiflex your heel/foot, oppose the flex, extend your arms, flex your wrist and shoot for a 5- step action (or whatever) but with practice your brain will begin grouping actions...",
"Set - up now includes your initial flexion. You now begin to extend your arms during opposition, albeit slowly. Then you can release the ball. Your complex 5- step task is now a more optimized 3- step task, easier to remember and perform, but your brain is still ultimately responsible for the tasks, not your body due to motor grouping as crudely and generally described. "
] |
[
"You're right, I'd just like to point out that our memory for motion/actions is longer than our recall for factual knowledge. There is certainly a limit, and it can certainly be lost (ex. a stroke victim forgetting how to walk).",
"Musicians don't forget how to play after being away for a few months, it's quite common to pick up an instrument for the first time in a decade or two and begin playing (very common among those who are incarcerated). We don't forget how to ride a bike, athletes don't forget how to throw a ball, and typists don't forget how to use a keyboard."
] |
[
"I actually play guitar and the reason I was a bit skeptic about putting a date on was because it seems songs I really know, I don't forget. Some songs though, ones I'm not very comfortable with I can forget in months time. But that's probably because I haven't associated the song with motion but rather the factual knowledge of the tablature.",
"But still. Sometimes I can't recall a song at all until I pick a guitar up and start playing then it comes easily. Do you have any idea why that might be? Is it simply I have forgot everything about the song aside from the physical motions involved in playing it?"
] |
[
"Medicine - What actually happens to a patient when they are put under anesthesia?"
] |
[
false
] |
I'm just a curious high school student who is wondering what the science behind anesthesia is. Why is it that you don't feel pain when you're sleeping? ...or is it even a state of sleep? I really have no idea... Thanks for any explanations :)
|
[
"General anaesthesia is when you are \"under\", as opposed to local which blocks pain in a local area. Under general anaesthesia you aren't sleeping because during normal sleep you still respond to pain stimulus and will move about. So it is actually a medically induced coma. A combination of drugs are used to do different things depending on the requirement; analgesia (loss of response to pain), amnesia (loss of memory), immobility (loss of motor reflexes), sleep (loss of consciousness), skeletal muscle relaxation (paralysis). "
] |
[
"So in the case of analgesia, what is happening to the body that makes these responses to pain quit?"
] |
[
"There are many different types that work in different ways;",
"http://en.wikipedia.org/wiki/Analgesic",
"An old, common and powerful class is the ",
"opiods",
" which work by attaching to opioid receptors found in the brain, spinal cord, and gastrointestinal tract. When the drugs attach to certain opioid receptors, they block the transmission of pain messages to the brain."
] |
[
"\"For reasons even a chemist is hard-pressed to explain, ring shaped gasoline molecules are higher in octane\", is this still true ?"
] |
[
false
] |
I'm watching a Modern Marvels episode about gasoline, and they're on the bit explaining about hydrogen fracking, and this line stood out. This episode is probably 20 years old now, does it still hold true ? If so, why ?
|
[
"Well, I'm only an undergraduate ChemE student, and it may hinge upon the understanding of what is meant by \"octane\", but I feel like I can explain this pretty easily. ",
"First, definition: By octane, I assume you mean octane number, and I interpret octane number to be broadly how high the initial energy must be to ignite the fuel-air mixture. In other words, I'm interpreting it as something very similar to combustibility. ",
"Now, ring-shaped molecules are in general less ",
" than straight molecules. Volatility is how, very generally, how easily it is to evaporate a liquid. Cyclohexane (C6H12) has a melting point of around 6C, while straight hexane (C6H14) has a melting point below -90C, despite the fact that it's a actually a heavier molecule. The significantly higher melting point means it's much less volatile. In other words, this means straight hexane is a gas at a given temperature than cyclohexane.",
"You probably heard this from the show, but it's not actually the liquid that combusts, but the gas. By using something that's less volatile, you're able to bring it to higher pressures and temperatures before it reaches that critical point of ignition. Higher compression means higher efficiency. ",
"As for ",
" cyclohexane is less volatile, that's also easy enough to explain. It has to do with the intermolecular forces. Since they all are essentially the same bonds (C-C and C-H), there are no polarity differences. This means it's all in the geometry. ",
"Consider a bag of rubber bands, and then try to pick up a single rubber band. You inevitably will pull some of the others with you. Compare this to a box of sticks, where you can easily grab one and pull it out. The real version is more complicated (and my visualization is moderately exaggerated), but that's the gist of why cyclo-molecules are less volatile. "
] |
[
"That line doesn't make very much sense. Gasoline is a mixture of several molecules, mostly hydrocarbons of varying sizes and structures. One such hydrocarbon is octane, an 8 carbon linear chain. By definition octane is not and cannot be a ring. ",
"My guess is that they may be saying that ring structures found in gasoline can provide more energy, although this would not be true."
] |
[
"I love ",
", but their writing isn't always terribly...technical.",
"When the narrator says \"octane,\" what they are referring to is ",
" As I explained in a reply to another comment on this thread, ",
"[Octane rating] is based on a comparison to iso-octane and n-heptane. For example, 91 octane-rated gasoline will detonate at the same temperature and pressure as a mix of 91% iso-octane and 9% n-heptane. ",
"See ",
"https://en.wikipedia.org/wiki/Octane_rating",
".",
"Octane rating is a way of expressing how resistant a fuel is to spontaneous detonation (ignition before the spark plug ignites the fuel in a gasoline engine), which matters because high pressure engines are more efficient and have a better power-to-weight ratio than lower pressure engines, but they require more detonation-resistant fuel.",
"A stable molecule--one that has high activation energy--is more resistant to spontaneous detonation in air. Cyclical hydrocarbons are more stable because the ring shape forces electrons into a shield shape. Take a look at this page for more info: ",
"https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Map%3A_Organic_Chemistry_(McMurry)/Chapter_15%3A_Benzene_and_Aromaticity/15.02_Structure_and_Stability_of_Benzene",
"/Chapter_15%3A_Benzene_and_Aromaticity/15.02_Structure_and_Stability_of_Benzene)",
"This, and the theory behind detonation resistance in fuels, has been known since well before the second world war, so a chemist would not be \"hard pressed\" to explain this."
] |
[
"Could plants grow from the light of propane lanterns? Would the extra CO2 help growth?"
] |
[
false
] |
[deleted]
|
[
"Couple of other comments have hit on this, but a gas lamp is probably not going to output nearly the intensity of light needed for plant growth. I was using high intensity fluorescent bulbs in a make-shift chamber in a lab, and unless they were <24\" from the leaves, there wasn't enough photosynthetically-available radiation (PAR) to get any growth. ",
"It might be a good environment for mushrooms though!"
] |
[
"It may not be a good idea as 1059fmwmal points out, but would the plants actually grow?",
"This",
" contains a graph of visible-spectrum emissions of a propane flame.",
"This",
" has charts that show how plants, algae and their pigments respond to different wavelengths of light.",
"The propane flame is spectrally spiky, but the largest spike is near chlorophyll's peak absorption band. So a plant can efficiently use light from burning propane. I'm not sure if they'll like that spike in the near-ultraviolet but they can at least use the energy you're giving them.",
"Plants do like CO2, but only to a point. Plants get energy by making sugar and oxygen, but they also consume some of their own sugar using oxygen. The optimal level varies from plant to plant but will be around 1,000 ppm.",
"If I had to do this in a cave I'd constantly draw air in at one end and constantly blow it out at the other. Otherwise the temperature, CO2 and humidity will become unmanageable. My stealth grow-farm may be detected by the massive plume of hot air. If you have buttloads of propane then you could just make an electric generator and do indoor agriculture the normal way."
] |
[
"Using gas mantles this could be feasible. A standard 2 mantle camping lantern is around 800-1600 lumens, a 24 watt CFL for comparison is about 1600 lumens. The color temperature of a gas mantle is about 2800K by the red blue ratio alone, however, these mantles do not produce light by black body emission alone and in fact the green ratio is about 30% too high for a color match to 2800K. For comparison a warm white CFL is around 2700K and a daylight CFL is around 6500K. Higher color temperatures such as 6500K are ideal for vegetation becasue they provide more blue light so although ~2800K is redder than ideal it would probably still work.",
"All said though you would be better off running a small propane generator and using that to power some LEDs or CFLs to grow plants. ",
"http://en.wikipedia.org/wiki/Gas_mantle",
"\n",
"http://www.candlepowerforums.com/vb/showthread.php?180416-Coleman-propane-lantern-lumens&s=e5c7bb2716feb0e4375666d84ca97db0&p=2243557&viewfull=1#post2243557",
"\n",
"http://bulbcollector.com/forum/index.php?topic=1638.0;wap2",
"\n",
"http://en.wikipedia.org/wiki/Candoluminescence"
] |
[
"Why is an oversupply of electricity a problem?"
] |
[
false
] |
[deleted]
|
[
"There's no way to store power on the scale of national grids. There just isn't the technology to contain that much energy on a short term basis. Therefore, the grid is in a constant delicate balance where operators try to generate ",
" as much power as is needed at one particular moment. Too much or to little and the power you receive at a wall socket will be at the wrong spec, and some devices may not work correctly or at all."
] |
[
"If you burn 1 unit of fuel to produce 1 unit of electricity but you consume 0.75 units of electricity you have just wasted 0.25 units of fuel.",
"You charge your clients for consumed electricity so, you just lost money.",
"That's the simple economic perspective.",
"There is also the environmental which is that you produced 0.25 units of unneeded pollution and that you burnt .25 units of fuel which is cannot be replaces (non-renewable).",
"As Charyou-Tree pointed out, you can't really store the 0.25 units of excess electricity."
] |
[
"Well, we can do it practically with hydro, we just don't have enough of it relative to what we need. "
] |
[
"Is there an algorithm to compute \"truly\" random numbers?"
] |
[
false
] |
Reading through the on random number generation it talks about how pseudorandom number generators use a key value and perform a number of operations towards it to make it appear random. An algorithm that is deterministic must not be able to generate truly random data due to the fact the determinism must produce the same output for the same input at all times. So I guess my question really is, is there a known non-deterministic algorithm for generating truly random numbers?
|
[
"Theres no such thing as an algorithm for generating truly random numbers. To get randomness, you can't start from something that isn't random.",
"Therefore, generating truly random numbers has to stem from hardware, not software (",
"http://en.wikipedia.org/wiki/Hardware_random_number_generator",
"). For instance, from quantum mechanics, we know that fundamental processes are inherently probabilistic. So we can design hardware to translate that into random numbers."
] |
[
"To have random results you gotta have random inputs. In the end algorithms are sequences of instructions and so are always determinstics. As long as all the inputs are known, the result will be the same."
] |
[
"\"Anyone who considers arithmetical methods of producing random digits is, of course, in a state of sin.\"",
"-- John Von Neumann"
] |
[
"Why can we ignore the imaginary part of the simple harmonic motion displacement equation?"
] |
[
false
] |
If you derive the displacement of a mass on a spring from the first principles F = mx''(t) = -kx(t) then you get the equation x(t) = Acos(wt) + iBsin(wt) where A and B are real constants and w is the angular frequency (sqrt(k/m)). Why can we eliminate the second half of the equation? Is it ever used? My working for the derivation is as follows, there may be a mistake as google is fruitless: F = mx''(t) = -kx(t) x''(t) + kx(t)/m = 0 let x = e n e + k/m e = 0 n + k/m = 0 as e =/= 0 therefore n = +/- (-k/m) x(t) = c1e + c2e (Substituting w for (k/m) Applying Euler's identity: e = cos(wt) + isin(wt) x(t) = c1 + c2)cos(wt) + i(c1 - c2)sin(wt) x(t) = Acos(wt) + iBsin(wt)
|
[
"Once you get to the general solution you have to get the particular solution by applying the initial conditions. Say you know the position and velocity at t=0. This first means that A has to be equal to the initial displacement x(0). Looking at the derivative you have",
"X'(t=0) = iBw",
"So unless you have an \"imaginary\" initial velocity, which is an unphysical thing, B must be a function of 1/i, or in the case of 0 initial velocity, 0/i = 0.",
"In short, you'd need an imaginary displacement or velocity as an initial or boundary value for B to end up nonzero (or A to be imaginary)."
] |
[
"Have you taken a course in linear algebra? It will clear up a lot of your confusion, but we have two solutions:",
"y1 = e",
" , y2 = e",
"The solutions are called linearly independent (which for now means \"not constant multiples of each other\") and any other solution is a linear combination of these two solutions.",
"Can you verify for yourself that (y1 + y2)/2 = cos(wt) and (y1 - y2)/(2i) = sin(wt)?",
"Since cos(wt) and sin(wt) are formed as linear combinations of y1 and y2, that means cos(wt) and sin(wt) are also solutions to the differential equation. Furthermore, cos(wt) and sin(wt) are also linearly independent, which means that you can write the general solution as:",
"y = (c1)sin(wt) + (c2)cos(wt)",
"Many times, this form of the general solution is more useful than the exponential form because it is purely real-valued, with real coefficients.",
"So there is no \"discarding of solutions\".",
"But linear algebra is so cool and fascinating that I feel compelled to share this with you:",
"If you study physics, you are familiar with coordinate systems. The most familiar is the Cartesian coordinate system, and you know that there are a set of \"basis vectors\" (i, j, k). Every other vector in R",
" can be formed through linear combinations of these basis vectors.",
"Linear algebra extends these concepts to arbitrary \"vector spaces\" which are not necessarily R",
" . In this case, one vector space is the \"space of solutions to the differential equation\". Just like one defines basis vectors for R",
" , one can also define basis vectors for this solution space - the requirement is that there are enough of them (the solution space of a 2nd-order differential equation is 2-dimensional, which means you need 2 solutions), and that the basis vectors are all linearly independent. This means that e",
" and e",
" are basis vectors for the solution space.",
"But there is no unique set of basis vectors; in fact, cos(wt) and sin(wt) are also basis vectors for the same solution space. And any solution to the differential equation is a linear combination of the basis vectors... that's exactly what c1 and c2 tell you. Essentially, (c1, c2) is a coordinate in your solution space relative to the basis vectors!"
] |
[
"It's not that you just ",
" the imaginary part. A \"solution\" is valid only if it satisfies the original differential equation (which A cos(wt)+i B sin(wt) does) but also has to satisfy the initial/boundary conditions. If the initial conditions are all real, then B must be 0 to satisfy them. Physics don't need to come into play there, the math is all self consistent."
] |
[
"Do photons have radii?"
] |
[
false
] | null |
[
"Nope, they're point particles, like any other elementary particle."
] |
[
"What does that exactly mean? Does that mean protons, neutrons, and electrons also don’t have a radius? If they don’t, then how do we know they have mass? I know their mass comes from Quarks and gluons and iiirc the Higgs Boson, but how can they be a point with mass? (Not photons)"
] |
[
"Does that mean protons, neutrons, and electrons also don’t have a radius?",
"Protons and neutrons are composite particles, so they have nonzero size. But elementary particles are treated as pointlike in quantum field theories.",
"They can be treated as point particles but still have mass, there's no issue with that."
] |
[
"If a person is starving to death, is there a point in which food intake will not save the person?"
] |
[
false
] | null |
[
"Great question! I agree with Ag-E, if a person is literally starving to death, energy exertion related to energy intake is not the reason for mortality rather the body being unable to digest the food due to damage is the culprit. If a person is chronically undernourished, their body will start to use protein as the preferred fuel source (rather than fat but it is used as well) so it'll start breaking down muscles. One muscle that is affected by this is the heart and if your body starts consuming it to fuel itself, the heart's productivity decreases which makes it harder for it pump blood through out the body. But one thing that people often don't realize when it comes to people who are really starved and undernourished is that once they start eating again, it can be really dangerous. Something called refeeding syndrome can occur. What happens in refeeding syndrome is that the body has become accustomed to this state of starvation (so it is relying predominantly on fat and protein sources of fuel) that if it is refed too aggressively, glucose, potassium, phosphate and magnesium are quickly absorbed into the cells to replenish those stores which results in low serum levels of all of those nutrients (aka low levels circulating in the blood). And at this point basic biology kicks in, if you have a high concentration of these nutrients in the cells and a low concentration in blood, water will follow the nutrients into the cells to create equilibrium in the nutrient concentration which results in really fast water retention. But low serum electrolyte levels causes a whole mess of heart problems as well as respiratory problems. Often if a body is really underfed and refeeding syndrome occurs, it is harder to survive since your body is so weak.\nThanks for letting a dietetics student nerd out, sorry that its such a lengthy post!"
] |
[
"Yes, I think so though I don't know of any hard numbers. Also it's likely that it's not an issue of energy for absorption being greater than energy needed, but rather an issue of the body cannot absorb the food itself due to 'damage' (hypoplasia, really) to the digestive tract.",
"As to how intravenous nutrients would affect this, I don't know. A 'slurry' injected straight into the SI might help as well. "
] |
[
"Are there any known cases of a disorder in which the body started >doing this when it wasn't necessary? ",
"Type I diabetes. glucose sits out in the bloodstream but there isn't an uptake signal (insulin). so the body assumes it's starving, and some krebs cycle derivatives (where much of fat and protein get turned in sugar-type compounds) end up being used as fuel. patients presenting with diabetic ketoacidosis often have lost 10-20lbs prior to coming to the hospital-some of this is water weight but some isn't. ",
"some will end up with lipid levels that are ~50x the normal limit as their body tries to generate some manner of nutrition. I had a patient whose blood in a tube, after being left out for 5 minutes, separated into a 40% creamy top and then normal blood below. he had digested his fat and it was sitting in his bloodstream (and outside it too! covered in xanthomas). "
] |
[
"After watching a film at the cinema yesterday my vision was 'flickery' for short time afterwards. What could have caused this?"
] |
[
false
] | null |
[
"Please observe the subreddit ",
"guideline",
" - ",
"No asking or giving medical advice",
"and",
"Personal experience can not usually be explained scientifically with any confidence and will invite speculations/anecdotes."
] |
[
"Where do you suggest I ask this then?"
] |
[
"It is against Reddit's Terms of Service to provide medical advice, however, if you are just curious about your own personal experience, you may want to try out ",
"/r/askreddit",
" or ",
"/r/DAE",
"."
] |
[
"Would gaming glasses actually help your eyes or reduce eye fatigue during long gaming sessions? (Gunnar Glasses for example)"
] |
[
false
] | null |
[
"I just watched the ",
"\"Gunnar Technology\" video",
" on their webpage, and holy smokes they need a new pr/advertising team. FRACTYL?! I-FI? IonIK? I feel like I'm reading a marketing brochure for snowboards in the 90s.",
"The only thing that sounds plausible to me is eyestrain reduction, which, in their nauseating technobabble-with-lots-of-buzzwords-speak \"actually ",
" light ... and prefocuses that light [so your eyes don't have to work so hard]\", is exactly what the 5$ reading/computer glasses do from the rack at your local Walgreens/CVS do.",
"Filtering out specific wavelengths of harmful blue light is bogus - your eyes only have 3 cones in them anyway, so, their claims to the contrary... it really is just a yellow tint.",
"\"Ocular microclimate\", good god the marketingspeek doesn't end. Actually, I guess that's ~plausible(?). Perhaps the humidity of the air on the inside of the glasses really is significantly higher than on the outside and that makes your eyes happier. It would be interesting to see the inside/outside humidity measured on those gunnars (the video shows 49% humidity vs 66%), compared to that of cheap reading/computer glasses.",
"I would personally save your money, go to the drugstore, plop down 5$ on a pair of +1 dioptre reading glasses, which will provide you with exactly the same effect as the most likely only plausible effect the Gunnar's have, and if they don't work for you, keep the glasses, because you'll need them in your 40s or 50s anyway."
] |
[
"That's what's called \"confirmation bias\": in this case, your brain cannot accurately gague the eyestrain during a session with or without the glasses, so you assume that they must be doing something positive.",
"Personally, I'd be very interested in a rigorous paper on these glasses."
] |
[
"This was an awesome response- thank you! "
] |
[
"Would a tattoo with radio opaque dye work?"
] |
[
false
] |
Was looking at a clear radio opaque dye in the OR today (it was Omnipaque I think) and I got to wondering if a tattoo with it would be feasible. The dye only shows up under X-Ray and otherwise looks like water. Would it be possible to get an "invisible ink" tattoo in this way?
|
[
"Tattoo ink consists of ",
" and a ",
". The pigments are solid particles which are not absorbed by the body. The carrier is there to sterilize and to form a suspension making the tattoo process easier to practice.",
"If you injected a dye (dye = solution, not a solid pigment) one would expect the dye to eventually be absorbed and perhaps excreted by the body. That is the reason for using pigments...their size helps make them resistant to being absorbed.",
"All that said, the idea of tattoing with an X-ray visible colorless dye should provide an image under Xray for the length of time the dye persists in the skin. Considering the unknown health effects of having this dye in intimate contact with your tissues for who-knows-how-long, should give you pause before trying such a thing."
] |
[
"There are 2 kinds of commonly used radiopaque dyes used in medicine. Barium compounds are used in the GI tract and is a white, chalky liquid. It is safe in the GI tract, but it can cause severe inflammation if it gets into other tissues. This is why it's avoided if there is a good chance of immediate intestinal surgery. If it spills into the abdomen, it's very painful. It is however cheaper, so it's often used in veterinary medicine.",
"The other kind of dyes are iodinated. They can be clear and are used in the GI tract and can be injected into veins for other kinds of contrast studies. As far as I know, they do not cause a inflammatory reaction if they get out of the vein. (There are some drugs that are fine in the blood vessels, but cause damage if they get into the surrounding perivascular tissue. Thiopental, a veterinary anesthetic, is rarely used now due to this. Many chemo drugs are also caustic outside the veins.) As a guess, not a recommendation, it would likely be safe under the skin, but I can't be sure. As far as clearance from the body, most iodinated dyes are cleared from the blood by the kidneys. I don't know all the biology around tattoo dyes, but my guess is that if done correctly at the right depth, it would probably stay put in the skin, but that's an educated guess at best. I wouldn't do it without consulting a doctor, if at all.",
"Considering the fact that it would only be highly visible on radiographs, I don't know why someone would do this. Also, it could obscure important details on a radiograph if a person were to be injured in that area. I'm assuming this question is purely hypothetical."
] |
[
"It certainly would not be invisible on the skin normally. it would look like a faint white, patchy tattoo, or scar. Look at ",
"This",
" example of a UV ink tattoo for reference of what I mean. The tattoo process changes the skin enough that it will be noticeable in most environments even if done with \"transparent\" ink. ",
"As to the question of whether it would be radio opaque as a tattoo, probably for at least awhile, depending on what kind of longevity the product was designed for. but It most certainly would not be invisible to the naked eye. "
] |
[
"Is the water at the bottom of the ocean more \"condensed\"?"
] |
[
false
] |
Is the water in the deepest parts of the ocean more "condensed" due to the pressure? Also say you manage to get the water at the deepest parts of the ocean in a container, what happens to that container once you start bringing it back to the surface and open it? Does the water shoot out due to it no longer being under pressure, or does nothing happen and you just have a container of water?
|
[
"Water is not technically incompressible, but it doesn't compress much. Pressure increases ~20 bar per 100 meters of water depth, so on a ",
"scale like this one",
" you can see that the density changes (and thus volumetric changes for a constant mass) are relatively small, though you would also have to account for temperature, which will generally decrease with depth, but is not constant with depth because of currents and global circulation patterns in ocean water. Going for the most extreme example we have on Earth in terms of depth, water at the ",
"base of the Mariana Trench",
" compresses by just shy of 5% due to both the high pressure and low temperature."
] |
[
"Water is surprisingly incompressible. More or less like steel.",
"To answer the second part of your question, water contains dissolved gas, and so the water under great pressure at the bottom of the ocean can contain more gas than water under less pressure near the surface. As you bring up a container of water the pressure will drop, and although the water does not expand, the gases will come out of solution, like opening a can of carbonated soda. Therefore, if the container is not vented it is likely to explode."
] |
[
"I love this sub. Thanks, man"
] |
[
"Does Monty Hall Problem solution apply to Italian gameshow?"
] |
[
false
] |
Mathematicians of the internet, here's a question that's been bugging me for a while... So there is this famous gameshow in Italy: You get assigned one of 20 numbered boxes, that contain different money prizes ranging from 0,10€ to 500.000€. You don't know what's inside yours or any other box. During the whole show you basically call randomly the numbers of the other boxes you want the host to open and the prize they have inside is lost; slowly lowering the number of boxes, therefore prizes, left in the game. At the end of the game you are left with 3 (or 2, it depends... But let's say it's 3) boxes, maybe 2 containing a low prize and one containing a high one. You are then asked if you want to swap your box with any other and then open the 2 left, one by one. My question is: has the famous Monty Hall problem anything to do with this gameshow? Should you always swap trying to get the best prize? Thanks in advance! EDIT: spelling
|
[
"The key ingredient that makes switching best in Monty Hall is that the host removes a losing option. The host adds his own knowledge of which door is bad into the mix. Since this does not happen in this case, all the remaining boxes have the same odds of being the best box. So there will not be any benefit to switching."
] |
[
"Right, I wasn't really sure about it. Thanks a lot!"
] |
[
"In this game, the Monty Hall analysis does not apply and it does not matter whether you switch boxes at the end or not. You can not increase (or decrease) your expected winnings by switching. Your expected winning at the start is equal to the average of the 20 prizes; your expected winning at the end (when only 3 boxes remain) is the average of the three remaining prizes.",
"The game is equivalent to the following: first you randomly pick out one box B1 of the 20, then you pick two more: B2 and B3. You now know the prizes in the three boxes, let's say one high prize and two low ones, but you don't know which is which. Given that knowledge, should you switch from your box B1 to B2 or B3? The answer is: it doesn't matter, your chance of getting the high prize is 1/3 no matter what. ",
"The reason is that by initially picking B1, then B2 and B3, it's equally likely that B1 or B2 or B3 contains the biggest prize of the three, so the probability that either box has the highest prize is 1/3.",
"Now, the analysis for a person who decides to stick with B1 goes like this: the chance that B1 contains the high prize is 1/3; they didn't switch, so they'll win the high prize with probability 1/3.",
"The analysis for a person who decides to switch goes like this: if B1 contained the high prize (chance 1/3) and you switch, you'll end up with the low prize. If B1 contained the low prize (chance 2/3) and you switch, you'll get the high prize with probability 1/2. Altogether, you'll get the high prize with probability 1/3 * 0 + 2/3 * 1/2 = 1/3, just like the other person.",
"This problem is different than the Monty Hall problem: by randomly opening boxes yourself, you don't gain information about the location of the higher prizes in the remaining boxes. By contrast, Monty Hall, who is forced to open doors with low prizes only, thereby gives out some information about the location of the high prize.",
"EDIT: My analysis above assumed that you were allowed to pick the initial box randomly. I just reread the question, and it says that you get \"assigned\" the initial box. That opens the possibility that the producers of the show, who presumably know the location of the high prizes, deliberately assigned a low-prize box to you. Then you need to analyze the problem with game theory. If you want to maximize the worst-case outcome in the face of a hostile opponent, which is what ordinary game theory always does, then you should switch at the end. The reason is that the hostile producers could control the contents of your box, but not the contents of the other two remaining boxes."
] |
[
"Are claims made by supporters of a paleo diet actually valid claims supported by scientific evidence?"
] |
[
false
] |
I'm mostly talking about the idea that this is the way we should be eating because it was how the paleolithic man ate, and our biological evolution didn't have time to catch up to our change in sources of food once the settling, domestication of animals and all that began. I'm aware that this question was asked a few times already (maybe not completely the same question, but about the same topic), but the answers there aren't that straightforward. They also aren't very supported and don't seem to meet the quality of the answers we usually get these days. Also, I understand that it's probably a healthier diet than the average diet of a person living in a western country. I also understand there is probably little to no danger in practicing it. I'm just interested in the "scientific facts" used in support of it. EDIT: One other thing. This is not a question about following the diet. I'm not interested in following it. This is purely a question about the "scientific support" that the promoters like to use.
|
[
"The field of nutrition is far from being a scientifically rigorous one, hence the reason why you're not going to get a straightforward answer - because there is none as of yet.",
"The human body and its interaction with the fuel it consumes and how that affects health and robustness is complex and it's not simply a matter of 1 + 2 = 3.",
"We're working on best guesses and incomplete theories, of which paleo is one. I will say one thing - any diet that has arbitrary restrictions such as the paleo diet is not going to be the optimal human diet, but it may be a very good one."
] |
[
"And that vitamins have something to do with it, although we're not sure what."
] |
[
"There is a fair amount of scientifically rigorous evidence in the field of nutrition, but there is also a lot of gaps and unknowns.",
"Even if we knew everything about nutrition that there is to know, there is still the matter of gauging how it's going to effect a human's biology on a daily, hourly, etc. basis. A person is not the same person from a biochemical standpoint from day to day and minute to minute. You are constantly in a state of hormonal flux, among other things. This goes for men and women but doubly so for women due to their menstrual cycle.",
"A true \"optimal\" diet is likely to be so complex to calculate that it will be similar to the realm of weather prediction. Keep in mind also that it varies by the individual, and by the environment that the individual subjects themselves to and their various activities.",
"the only thing that we know \"for sure\" is that some amount of caloric restriction would help just about everyone who isn't already underweight.",
"By \"help\" I'm sure you mean the studies that have shown that caloric restriction leads to some increased longevity, yes? I'll give my same answer that I always do to that: I would rather live 80 years as a lion than 85 years as a lamb. Quality of life is IMO more important than pure maximization of longevity.",
"There are many interesting avenues of inquiry into the field of nutrition going on, many of them giving us a more complete picture of what's occurring. We're nowhere close to a comprehensive knowledge of this subject, but we're well on the path.",
"Let me say one more thing: there comes a point of diminishing returns when it comes to nutrition. Unless you're a bodybuilder, doing simple things like balancing your macros, minimizing processed garbage food, maximizing micronutrient-dense food choices such as broccoli, and getting adequate amounts of the 24 essential vitamins and minerals is going to go a long way towards sculpting a good diet."
] |
[
"My SO is wondering, if global warming is real, why is it snowing in our town in Louisiana for the first time in decades? She thinks this is an adequate disproval of climate change."
] |
[
false
] | null |
[
"Hi GusTheSquid thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"'Earth Sciences'"
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"For more information regarding this and similar issues, please see our ",
"guidelines",
"Earth sciences FAQ",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"How does matter come into existence?"
] |
[
false
] |
I once saw a simulation of fluctuation in quantum vacuum, in the video they explained that even in vacuum there is no absolute vacuum. So I got the idea of matter coming into existence and disappearing just as quick. What are these fluctuations? are they particles or is it energy? Is it neither or both?
|
[
"Right, but they have to be virtual particle/antiparticle pairs in order to satisfy various conservations laws.",
"\"Virtual\" and \"anti\" mean different things. They're not interchangeable."
] |
[
"Particle/antiparticle pairs can come in and out of existence for no reason at all. The reason is the time-energy uncertainty relation, which basically says energy can come from nothing as long as it doesn't \"live\" for very long."
] |
[
"There is a little bit of energy 'everywhere', you could think of it like the surface of a lake on a calm day. It looks flat but when you get up close you will notice it does jiggle a bit.",
"Saying 'a virtual pair is created and destroyed' is analogous to noting that occasionally the random movement of the lake surface will result in a little peak or trough, which 'dissipates' back into the lake immediately.",
"It is currently an unsolved problem",
" as to why this energy \"doesn't count\" as a source of gravity - calculations indicate that this energy ought to warp spacetime so much at the whole thing shrivels up in a blink of an eye. One theory is that the 'dark energy' is large and repulsive, and almost exactly cancels with the vacuum energy."
] |
[
"How can RNAs with internal loops be stable?"
] |
[
false
] |
[deleted]
|
[
"To answer your first question.\nThey way you imagine RNAs is not correct. They are not just floating around. The nucleus is not like a water balloon with some DNA, RNA and Protein mixed in. The nucleus is much closer to a gelatinous mix of densely packed DNA, RNA, proteins, nucleic acids, salts and some water. So the RNAs aren't really floating around not touching anything. ",
"Next the RNAs (or DNA for that matter) aren't \"naked\" they are coated with proteins. Proteins that protect the cap of the RNA, proteins that protect the tail, proteins that mark splice sites, proteins that signal the time and location the RNA should be used and so on. ",
"That being said sometimes there are unpaired bases exposed to the nucleus. Sometimes they make contact with other bases. But pairing isn't something that is very strong between ",
" pair of bases. Its the cumulative affinities of multiple base pairs in a row that result in strands of RNA binding to each other. The geometry of the RNA also plays a big part, so depending on how tight the loop region is, the likelihood that the bases in it can bind is affected.",
"As for palindromes, they tend to base pair to form the stem component of a stem-loop structure. They can be uneven, and often are. The affect on stability depends on how long the stem structure is, and what base pairs make it up."
] |
[
"Thank you so much! I'm taking biochemistry and this really helped! Couldn't stop thinking about it haha"
] |
[
"I might add that RNAs do have complex secondary (and higher order) structures, sometimes crucial for their roles. For example, internal ribosome binding site (IRB) is a fricking secondary structure which is recognised by proteins and binds a fricking ribosome into a middle of RNA.",
"As for unpaired loops binding to each other, that's one way to get tetiary RNA structure."
] |
[
"Is there any evidence that the strains of Covid prevalent in the US this summer tend to produce milder, shorter symptoms?"
] |
[
false
] |
The reports of the illness I read in 2020 were typically along the lines of "holy shit that was awful!" and this summer, I get much more muted reports. Does the large-scale data collected by public health reflect my own personal/anecdotal impression? Also, is there data providing any sign that rates of mortality, and chronic, post-infection complications are reduced this summer?
|
[
"First off, omicron, the dominant variant since Christmas, is certainly both more contagious and less deadly than prior versions. The current subvariants of omicron are likely of similar contagiousness and deadliness to the initial omicron strain from Christmas. Even so, severity of illness and deadliness is lower for anyone who has partial immunity from vaccination or from a prior illness with COVID. Since so many people have partial immunity through at least one of those mechanisms, overall severity and deadliness is lower now than it was during the winter. Plus, we have effective antivirals for those at high risk of severe illness/death, and finally have a strong supply of antivirals.",
"But part of it is also that we're accustomed to how horrible COVID ",
" ",
" (edited) even for vaccinated folk who aren't hospitalized. I have a vaccinated friend who got a 105 degree fever from COVID recently. I have other friends who had an illness worse than the worse flu of their life, but not bad enough to go to the hospital. Nobody cares too much if you lose your taste for a while, so long as it isn't gone for months.",
"",
"https://www.yalemedicine.org/news/5-things-to-know-omicron",
"https://www.nature.com/articles/d41586-022-01730-y"
] |
[
"Smell and taste can disappear and seemingly never return. It’s not clear whether these issues are permanent or just long lasting. Also, some variants can cause reinfection of those that have had even recent infections. New vaccines are on the horizon that target less mutagenic parts of the virus, and may be more effective against reinfection from future variants.",
"Finally, long COVID is real and some studies suggest a significant fraction of folks infected by the virus at least once will ultimately develop long term complications. Overall there just isn’t enough data yet about concerning symptoms such as neurological impairment."
] |
[
"In UK, losing taste and smell is now a low percentage for omicron and subvariants.\nSore throat and headaches are the biggest recorded symptoms over here.\nEven fever is no longer a main symptom",
"https://www.bbc.com/news/health-62161604"
] |
[
"How can you identify if an atom can make 5 or 6 bonds in a molecule?"
] |
[
false
] |
I'm an 11th grader and I'm really confused on which atoms can make more than 4 bonds. For example in the class work there's a question that asks the structure of xenon tetrafluoride and my chemistry teacher said it can go up to 12 electrons. I understand that hybridization has something to do with it, but my teacher didn't explain it well.
|
[
"There's no trivial way to determine whether a main group element will break the octet rule. I'm afraid you'll have to get comfortable with identifying common examples by practising questions. You can then work out their structures as you would any other simple molecule - by counting the electrons (even if more than 8) and then using VSEPR theory (",
"here",
"/03%3A_Simple_Bonding_Theory/3.02%3A_Valence_Shell_Electron-Pair_Repulsion) and ",
"here",
"). Generally speaking though, heavier main group central atoms will tend to break the octet rule when they are bound to strongly electronegative elements (such as fluorine).",
"Why is the octet rule broken?",
"The octet rule is useful but is flawed because inherently it's based on filling the atomic orbitals of the atoms. In reality, it is the formation of molecular orbitals (MO), via the combination of atomic orbitals from different atoms, that must be considered when trying to determine the structures and number of bonds within a molecule.",
"So to fully explain the formation of XeF4 or SF6 you have to build ",
"MO diagrams",
" by combining the atomic orbitals of the separate atoms. These MO diagrams provide us with information on the energetics and symmetries of the MOs and provide us with a more robust way of determining if the resulting molecule would be feasible.",
"Here's",
" the MO diagram for sulphur hexafluoride (SF6). Just by simply counting electrons, SF6 seems to break the octet rule on the central sulphur (12 electrons). This molecule is feasible though, because the MO diagram tells us that 4 of the electrons are actually found in non-bonding MOs which, when you run the calculations, are found almost entirely situated on the electronegative fluorine atoms in the molecule. The F atoms are happy with this because they are particularly electronegative. The other 8 electrons are found in four bonding MOs which are 'shared' among the S and 6 fluorine atoms. Note: SF6 actually has a bond order of four not the expected six! (XeF4 has a similar story)",
"In a way we've retrieved the octet rule (the MO diagram tells us that only 8 of the 12 electrons would be 'situated' on the central S) but the main take away from this is that we must consider what is happening across the entire molecule not just be counting electrons on central atoms and trying to form whole, directional covalent bonds."
] |
[
"Yes this is very true. Though most taught approximations in chemistry sort of get it right and provide some insight. d-orbital hybridisation is as good as saying “elements higher in the table break the octet rule” and provides you with no more information into the true mechanisms at play."
] |
[
"Thank you. Strange as the link works fine for me."
] |
[
"Are electric cars really more efficient?"
] |
[
false
] |
I understand that electrical engines are generally upwards of about 80% efficient. However combining mechanical losses, grid transmission losses and thermodynamic efficiencies/losses through current combined power generation methods does an electric car utilise the chemical energy produced through coal and other sources better than an average Internal Combustion engine does from petrol? Given most power generation is a continuous process without the issues of regular cold starting and extreme variances in output I'd expect the average efficiency would be closer to the thermodynamic limit from heat engines than an IC engine. But given the losses of de-localised energy production and (I assume) over-supply for instances of low demand would the electric car (on average) be more efficient and less taxing on the environment or are we just relocating the problem?
|
[
"does an electric car utilise the chemical energy produced through coal and other sources better than an average Internal Combustion engine does from petrol?",
"Yes. The greater size, and other efficiencies resulting from the fact that they were designed for the specific purpose of converting chemical energy into electrical energy makes power plants and electrical cars much more efficient than internal combustion engines.",
"There are economies of scale, there are also other ways that a power station can use residual heat. For example to preheat water before turning to steam.",
"In a conventional combustion engine the heat is just waste heat. ",
"According to the Electric Vehicle Association of Canada, or EVAC, even EVs recharged from coal-powered electric generators cut carbon emission roughly in half. ",
"Source",
"Edit: If you want some more detailed figures, you can see that a typical combustion engine car has an efficiency of 18-25% ",
"Source",
", and that a power plant has an efficiency of between 33 and 60% ",
"Source",
" and the entire electrical distribution system has a total loss of 6% ",
"Source",
" electric drive vehicles have on-board efficiency of around 80% ",
"Source"
] |
[
"One key note to consider is manufacturing energy. People forget to consider whats involved in manufacture of the car, Battery cells manufacturing, especially lithium is intensive even disposal has a impact with electric as cells may only last 5-10 years.",
"I like to remind people that a hybrid economy car that only lasts 5 years may have more environmental impact than a conventional car which lasts 10 years currently, this may change with higher production in the future.",
"My opinion as a automotive engineer is currently a lightweight diesel is the most efficient and has the least energy consumed in its life cycle for work given, therefore giving the least environmental impact. The problem is many compacts like this are getting extra features and luxury items adding mass, and this is one of the most foolish things we do today in society, haul extra mass in transit. ",
"I wonder why every day I haul a ton of steel back and forth to work. I do know the reason why, its because everyone else does and if one of them hits me I will need it, mass always wins in a collision with all other things even, but if we all changed to modern materials at the same time we would be a lot better off.",
"And this leads to the second argument, why do I need to drive somewhere every day to work? we should be working where we live, I wold gladly walk to work for my commute but financially it doesn't work for me right now.",
"And lastly this gets to the final problem, we need cities where people want to live where they work, and can afford it. its foolish to be commuting and I feel something wrong every time I do it. It adds stress, costs money, along with the environmental impact of it (I car pool at least). but this is the core mistake we have made as society and we need to fix it. The typical city as we know it is out of date and non sustainable and we need to update this, some countries are working on it but we have a long way to go. "
] |
[
"In a conventional combustion engine the heat is just waste heat.",
"If the car has a turbo, not ALL of the heat is wasted. But, most of it still is. :P",
"People just don't understand how incredibly wasteful cars are with their power.",
"Not only is the internal combustion itself very inefficient, but the drivetrain is very inefficient as well. Your automatic transmission alone is wasting 10-15% (or more in older cars) of the mechanical power that the engine actually manages to create.",
"Modern electric cars like the Tesla Model S have only a single gear and as a result, far less parasitic drive train loss."
] |
[
"If I were run through with a 20 micron needle, would I feel it?"
] |
[
false
] |
[deleted]
|
[
"While 20 microns is small (.02 mm) you would feel it if you where run through with it although it would mostly feel like a pinch. The reason for this is on the way through you the needle would still likely hit a nerve cluster somewhere. Now if the needle only punctured the surface of the skin it is less likely that you would feel it see ",
"here",
". For comparison a tattoo needle is .2 mm and up and medical shots are about 0.5-0.9mm in diameter. "
] |
[
"The biggest risk would be contamination of sterile environments. Even if the needle itself was sterile and you sterilized the skin surface prior to puncturing (like you do with normal injections) if you actually punched through the intestinal walls you could absolutely carry bacteria from the gut into the sterile abdominal area like the mesentery. The needle would likely do no structural damage (well I guess it could collapse a lung . . .). Any blood vessels or whatever punctured by a needle that small would be fixed pretty quickly."
] |
[
"Secondary question. If someone was to be completely run through with said needle, how much damage would it do? As in, say it went through his stomach/intestines/liver, what would happen?"
] |
[
"Why is it so hard (or impossible) to keep our hands steady?"
] |
[
false
] |
I mean, I don't have particularly shaky hands, but if I shine a laser pointer across the room, the dot isn't going to be stationary. Somewhat related (or maybe not), why is it so hard to control our bodies in general? For example: typos, mistakes when playing instruments, messing up inputs in games, etc. Would improved proprioception reduce error?
|
[
"When it comes to keeping limbs steady, the issue is due to the nervous system. You see, to keep your hand steady, you need to use muscular force to keep the hand up. The muscle flexes because the brain sends impulses down the nerves which excite the muscles and the muscles contract. This is a discrete phenomenon, muscle fibers contract many times a second. The stronger the force they need to provide, the more they vibrate. That's why it's hard to keep a steady hand with your arm all out in front or to the side but pretty easy when you just let it hang on your side.",
"You'll notice that as your arm gets progressively more tired, your hand starts to shake more and more. Your muscle fibers are basically switching between resting and flexing. The transition between the two is not always smooth but you can get better at it with practice and improved endurance."
] |
[
"I think a better ELI5 explanation would be:",
"Your muscles are made of many little muscle strands (like a rope is made up of small rope fibers). When you hold your hand up not all fibers are being used at the same time (for that you need to hold extra weight in your hand). When some of the fibers get tired, other fibers need to switch with them and this transition is not always well-timed, so your hand fidgets a little. This effect is bigger when more fibers are being used at the same time, i.e. when you hold something heavy.",
"Dude, I think we are converging"
] |
[
"If I can do short ELI5 explanation: Muscles have many small fibers, where their state is binary, either pulling, or relaxed. More force means more fibers pulling, but they always pull all the way or not at all. When you try to hold your hand up, these fibers contract and loosen few at a time making it jerk a little because the movement isn't smooth.",
"Not exactly accurate, but I think that would be unreasonable anyway for a ELI5",
"EDIT: Don't read this filth, SpaceEnthusiasts own ELI5 below me is way better."
] |
[
"Why do (many) humans and so many animals enjoy being pet/stroked?"
] |
[
false
] |
I tried posting this Q a while ago but the phrasing was a little garbled - sorry for repeat. I'm curious about what purpose petting/stroking serves. A lot of people (but of course not all) enjoy non-sexual caresses but also a lot of animals - on Reddit, of course, we see all kinds of dogs and cats and and . I'm also curious about why it carries across species - ie, why a dog or cat or bird might enjoy being pet by a human.
|
[
"The specifics involve us having a lot if sensory nerves that are only stimulated enough to really feel if they're triggered in sequence. Since those nerves are a few centimeters apart it takes a nice slow scratch or a stroke to trigger this. ",
"The general answer is that humans are extremely social colony animals that are descended from animals that groom each other for both hygiene and to reinforce social bonds. So we enjoy touching and being touched because that was a good way for us to maintain a strong social group and improve survival. ",
"And the really simple answer is because it feels good. "
] |
[
"Small alternative answer that covers some non-social behaviors:",
"Some animals use rubbing or brushing as a way to transfer their familiar scent to objects and friendly animals, as a way to locate their territory. Making rubbing feel good is a simple evolutionary mechanism to make them more likely to do it.",
"My point is that more generally, a behavior doesnt have to give a social benefit for an animal to enjoy petting. That animal just needs to have some other behavior in that area which is now evolutionarily made into a pleasure center.",
"Milking cows is another example. Cows don't socially milk each other...not in the grooming sense. They will however seek out humans to milk them. Has nothing to do with being social or grooming or humans for that matter. This is why cows are just fine being milked by a machine and why cats also rub against your furniture and not just you."
] |
[
"surely there's a reason we've evolved...",
"Remember that evolution has no goals or purpose. Things that are beneficial to reproduction are more likely to persist in a population, but that does not mean they always do, nor that every aspect of a creature must benefit it in some way."
] |
[
"Why doesn't it get twice as bright when I turn on a second lightbulb?"
] |
[
false
] | null |
[
"it does, in terms of energy, but you don't perceive it that way: humans see in logarithmic scale, which means if you want things to get twice as bright, you have to square the intensity! It allows to have a good contrast perception in dark or bright environments similarly."
] |
[
"The relation of brightness to intensity is not quite logarithmic - a logarithmic relation would be where the ratio of a just-discriminable change in intensity (ΔI) is a constant fraction of the background intensity (I). Instead, the ratio changes gradually over the range of intensities, being larger for small intensities and smaller for large intensities. over a large range this change is well-described by a power law, i.e. it's more like brightness is the square root of intensity than the logarithm (in fact what we usually see is a transition from one power to another as you go from very low to much higher intensities).",
"The case where ΔI/I is constant is referred to as 'Weber's law' or the 'Weber-Fechner law' but it doesn't actually apply to many (or any?) real perceptual cases. At large enough intensities, the change in the ratio of ΔI/I becomes so gradual that you can say that the perceptual relation is close to Weber's law - over small ranges at high intensities, you could say that for all intents and purposes the relation is logarithmic."
] |
[
"square the intensity",
"...or the ",
" of the intensity? Seems to me one would not \"square the intensity\", one would multiply the intensity by the square of the desired ratio, which would be 2",
" = 4."
] |
[
"Why do I sneeze when I look at something bright?"
] |
[
false
] |
[deleted]
|
[
"This is called the \"",
"Photic Sneeze Reflex",
"\" and it isn't 100% clear why it happens. Check out the wikipedia for more information. The theories on this largely boil down to - \"in some people, light signals are interpreted by the brain as nasal irritation, perhaps because some neuronal connections went awry.\" But that is pretty much just re-stating the observation in more sciencey sounding language... There isn't a definitively more satisfying answer that I could find. ",
"Interestingly, we can largely predict who will have this response, just by looking at people's DNA. \n",
"http://www.snpedia.com/index.php/Photic_sneeze_reflex",
"The company \"23andme\" was able to find a strong association between two particular SNP variants and the photic response. As an aside, I have it too, and 23andme figured that out! Pretty neat!"
] |
[
"I've seen speculation that photic sneezing and synesthesia are linked",
"http://typewriting.org/2003/08/23/synaesthesia_and_sun_sneezing/"
] |
[
"You could also look for information by searching the subreddit before you post."
] |
[
"What is the estimated total population of uncontacted peoples?"
] |
[
false
] |
The Wikipedia article ( ) gives some partial estimates. Many are listed as "unknown" so a total estimate won't be very presice, but even the order of magnitude would be intersteting. Is it thousands, tens of thousands?
|
[
"Survival International, a nonprofit rights group based out of London, has been quoted in the Washington Post as well as other publications that there are maybe 100 un-contacted tribes worldwide. No mention of population though.",
"Here is a link of current campaigns. ",
"http://www.survivalinternational.org/tribes"
] |
[
"Yes, but the word \"contact\" in this context has a different meaning than you are thinking. It's confusing, but when referencing indigenous peoples \"uncontacted\" really means \"without an established relationship with modern society.\" It also is applied only on an individual level, which causes strange statements, such as saying that half the members of a tribe are \"uncontacted\" while the other half are \"contacted.\" Many of the people listed in the wikipedia article have been studied ",
". Calling the Yanomami \"uncontacted\" is ludicrous by any conventional sense of the word. Not only have multiple anthropologists lived with them and then published books about them; ",
"Yanomami themselves have published books",
".",
"There are pretty much no people in the world today that actually are what you think of when you hear \"uncontacted.\""
] |
[
"Wouldn't taking a picture of them from an assumed aircraft with the people pointing to the camera be considered \"contact\"?"
] |
[
"How does the clitoris age?"
] |
[
false
] |
Both men and women have nocturnal tumescences, (erections) in their genitals while sleeping due to the lack of norepinephrine in the blood during REM sleep But as men get older NPT (nocturnal penile tumescences) decrese and if they ever reach full erectile dysfunction they stop completely My question now goes for women As women age, do they loose clitoral capacity? Can their clitoris still receive sexual stimulation and respond to it if they're 90 years old for example? Or 100 years? Do they ever stop getting nocturnal clitoral tumescences?
|
[
"Short answer is yes. Vaginal atrophy and dryness related to low estrogen plays a role in diminished sensitivity and ability to reach orgasm, as does reduced blood supply to the clitoris and lower vagina. Also, the clitoris is likely to be less sensitive than in earlier years, possibly due to reduced estrogen levels and changes in the vascular and nervous systems.",
"All of this may lead to reduction in the sensations and pleasure during lovemaking. It also can affect orgasm, which may be less intense, take longer to achieve, or rarely happen at all. ",
"More than just issues with the clitoris, a common condition referred to medically as \"dyspareunia,” increases with age. Dyspareunia is a condition where sex because painful. Vaginal thinning and dryness are the most common cause of dyspareunia in women over age 50. ",
"Just like their male counterparts, orgasm problems are more common in women over 45. Although medicine and research to counteract this seriously lags behind the efforts to treat erectile dysfunction. ",
"In a large nationwide survey about sexual behavior among older US adults, 23% of women ages 57 to 85 said they did not find sex pleasurable. Of these women, 64%—or 15% of women in the overall survey—said they were troubled by this lack of pleasure. Another large nationwide survey found that about 5% of US women have a problem achieving orgasm that causes them concern. In that survey, the rate of these problems with orgasm was higher among women ages 45 to 64 and those 65 or older (6% in both groups) than among women younger than 45 (3%).",
"Here are some sources if you want to read more. ",
"https://www.ncbi.nlm.nih.gov/m/pubmed/16422862/",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3349920/",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3008577/"
] |
[
"In a study on vaginal estrogen application, researchers found that local application of estrogen has been shown to relieve symptoms of atrophic vaginitis including dryness, irritation, itching and or dyspareunia. In addition, local estrogen therapy may have a favorable effect on sexuality, urinary tract infections, vaginal surgery, and incontinence. ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3252029/"
] |
[
"Does supplementing estrogen help with the difficulty orgasming? I know my mom got on it when she went through menopause and said positive things but I know anecdotal evidence is worthless."
] |
[
"How much better do batteries need to get in order to replace carbon fuels on ships and airplanes?"
] |
[
false
] |
From what I understand, the biggest producers of greenhouse gases outside of power plants tend to be the mechanisms of shipping, such as trucks, planes, and ships. A big barrier to shifting these transport systems away from carbon-based energy is that batteries can't produce the massive amounts of power needed to fuel these things over long distances with lots of mass. How much better does our battery technology have to be in order for such things to be able to switch to batteries, and why?
|
[
"For a back of the envelope comparison, the energy content per kg for various fuels can be found ",
"here",
". For gasoline, WP gives about 47 MJ/kg. ",
"The batteries in a toyota prius have specific energies along the lines of 0.12 MJ/kg. Even penalizing conventional fuels by noting that the energy efficiency is going to be (very optimistically) ~30% still gives many times more energy for the same mass of fuel. Battery charging efficiency is also quite poor, so maybe it's unfair to penalize the conventional fuels.",
"But roughly speaking you need to improve energy densities/specific energies by a factor of 20-50. Charging efficiency would also need to be addressed, otherwise you're still wasting a ton of energy generating all the electrical power to charge the batteries."
] |
[
"It does seem kind of low. I just ran the numbers given here ",
"http://en.wikipedia.org/wiki/Toyota_Prius#Battery",
"273.6 V * 6.5 Ah = 6.4 MJ for a battery back which weighs 53.3 kg",
"Probably the 53 kg figure includes the whole assembly rather than just the battery material itself"
] |
[
"short answer: about 5 times.",
"compare ",
"energy density",
"petrol 47 MJ/kg",
"Li/air battery 9 MJ/kg",
"with planes there could appear a few other problems as to turbines, which couldn't possibly be replaced by elecric motors due to the function of fuel with expanding gases."
] |
[
"Do any planets in the solar system, create tidal effects on the sun, similarly to the moon's effect of earth?"
] |
[
false
] | null |
[
"Yes, but it's very, ",
" small. ",
"The reason is that while the tidal force scales linearly with the forcing body's mass, it also scales inversely as the distance ",
".",
"Let's scale our units so that the ",
". In those relative units, the rest of the planets' tidal forces on the Sun shake out as...",
"In other words, ",
" (with Venus a close runner-up), and "
] |
[
"Tidal force is the derivative of gravitational force with respect to distance. It basically measures how fast the gravity field is changing in an area, or the difference in gravitational force between the near and far sides of an object. Since gravitational force varies with inverse square, tidal force varies with inverse cube of distance."
] |
[
"Tidal force is the derivative of gravitational force with respect to distance. It basically measures how fast the gravity field is changing in an area, or the difference in gravitational force between the near and far sides of an object. Since gravitational force varies with inverse square, tidal force varies with inverse cube of distance."
] |
[
"'Muamba was ..... dead for 78 minutes ...' How?"
] |
[
false
] |
How is it possible for someone to "die" for that long, and still have all his vitals in good shape after his heart was restarted? Wouldn't the brain be deprived of oxygen, as the blood will not be pumped in enough quantities, and die? The article Thank you
|
[
"It looks like he was given CPR by a trained professional, which will keep blood circulating and oxygenate the blood. The fact he was a trained athlete and in good overall shape probably didn't hurt either."
] |
[
"He's correct, it seems they were forcing oxygen into him while his heart remained silent. Thank ... the great doctors and EMT's that saved his life."
] |
[
"My second thought was that they also induced hypothermia to protect his brain function. I found some sources that mentioned it but not up to the usual standard of things I cite. It could have played a role though. ",
"http://www.soccerblog.com/2012/03/why-fabrice-muambas-plight-aff-1.htm",
"http://www.cartilagefreecaptain.com/2012/3/17/2880713/fabrice-muamba-condition-tottenham-bolton"
] |
[
"Is there any study comparing the effects of smoking on health between sedentary and active smokers?"
] |
[
false
] |
[deleted]
|
[
"Hello!",
"While smoke induced pathologies are not my area of expertise, I have many colleagues at my institution that study COPD. There was ",
"a study in the European Respiratory Journal",
" which suggests that exercise reduces many of the problematic changes that happen someone smokes. Things like how elastic your lungs are (which allows you to breath easily) and how scarred your lungs become. (Note: these studies are done in mice, a very common model for human disease)",
"Furthermore, many studies suggest that exercise helps reduce the craving to smoke. Less smoking + less damage from smoking = healthier body!",
"Feel free to ask follow up questions! -J"
] |
[
"The health problem caused by cigarette smoke cannot all be cured by a healthy lifestyle... The cancer part for example. Cigarette smoke induces cancer because it contains carcinogenic components. Which means a componant that can induce mutations in your DNA. However hard you work out, you won't be able to repair mutations incorporated in your DNA and once you have acquired all the necessary mutations the cell goes rogue and you have a cancer( really simplified) So maybe it lessens the lung and cardiac complications but should not lessen the cancer rates."
] |
[
"The health problem caused by cigarette smoke cannot all be cured by a healthy lifestyle... The cancer part for example. Cigarette smoke induces cancer because it contains carcinogenic components. Which means a componant that can induce mutations in your DNA. However hard you work out, you won't be able to repair mutations incorporated in your DNA and once you have acquired all the necessary mutations the cell goes rogue and you have a cancer( really simplified) So maybe it lessens the lung and cardiac complications but should not lessen the cancer rates."
] |
[
"What is the closest blackhole (stellar or larger) to Earth?"
] |
[
false
] |
I tried my google ninja skills but most of the information is a decade or older, and the then concensus candidate (V4641 Sgr) now has a disputed distance from us. So anyone here know what the current undisputed candidate is?
|
[
"The closest would be Cygnus X-1, which is ",
" a black hole, and it's about 8,000 light years away."
] |
[
"Easier to see if it's closer."
] |
[
"The black holes that we know about (or think we know about) are quite easy to see. They are part of x-ray binaries--the accrete matter from a companion star and shine brightly in the x-ray due to their accretion disk. ",
"The problem is knowing for sure that the object is a black hole and not some other compact object."
] |
[
"Does the earth physically grow?"
] |
[
false
] |
[deleted]
|
[
"the earth is losing more mass via gases blowing away than it is gaining from in falling dust and rock. ",
"So taking into account the gains and the losses, Dr Smith reckons the Earth is getting about 50,000 tonnes lighter a year.",
"http://www.bbc.co.uk/news/magazine-16787636",
"your belief in something does not make it so"
] |
[
"I agree with spthirtythree, but there is some accumulation of dust/rock from space, if that is what you are specifically curious about. As he says, however, it is more than offset by the loss of gasses."
] |
[
"No, the Earth does not grow. In fact, it has a slight net loss of mass over time, as atmospheric escape of hydrogen (and a little helium) is the biggest factor in the Earth's mass change."
] |
[
"How are we able to observe and measure the half-life for certain elements?"
] |
[
false
] |
For example, Carbon-14's half-life is between 5,000 and 6,000 years. How do we know this?
|
[
"Somebody asked the same question yesterday, so I'll tell the same joke. A cop pulls over a speeding motorist and says, \"Sir, you were going 90 miles an hour back there.\"",
"The surprised motorist retorts, \"But officer, I was never planning on going that far!\"",
"A half-life is an expression of a rate. You don't need to wait 6000 years to measure it. You can measure the rate of decay over any time period, in the same way the cop doesn't have to follow for 90 actual miles to determine that the car is going 90 miles an hour. "
] |
[
"It's best explained with an example.\nTake carbon 14. A 14g sample contains 6.02214179×10",
" atoms. Over one minute, you observe 1.378x10",
" atoms decay.",
"\nUsing fancy math, you know a half life means after n years, there is only half the amount left. ",
"This makes the function for how much stuff is left (original amount)",
"1/2",
"=(original amount)(1-1/2",
") = 1.378e14. ",
"We can factor out the original amount and get 1-1/2",
" = 1.378e14/6.022e23",
"This means 1-1/2",
" = 2.28953745e-10",
"Now we can say -1/2",
" = 2.28953745e-10 - 1",
"or 1/2",
" = 1 - 2.28953745e-10",
"Finally we can solve. Ln(1 - 2.28953745e-10)/Ln(1/2)= 1/525600n",
"Therefore n= 1/[525600Ln(1 - 2.28953745e-10)/Ln(1/2)] = 5759.998 years",
"I know this is probably not what you meant however I feel nobody else knows and certainly will not do the maths, even though they are a sole part of it."
] |
[
"You don't actually have to sit and wait for the entire process. You can watch carbon decay over, say, seconds, weeks, or years and infer from that. The process is an exponential function so we can fit to that. ",
"We know experimental values enough to justify the theoretical proofs (which we also have from physics and go waaaay over my head, sorry). ",
"Other elements (like deuterium, radioactive phosphorus, etc.) have shorter lifetimes on the order of microseconds to hours to days, so we actually have real data on the full process from other radioactive elements to back up theory. There's no reason to believe carbon13 is different from Hydrogen2 or Phosphorus35 (among dozens of others)",
"If you still don't believe that, carbon dating of known archeological/geological sites matches the expected age. ",
"I'm not a physicist, but you could probably isolate a known quantity of radioactive material and count the radiation. You would need only a very small fraction of time of how long a half-life is for that radioactive isotope to determine the rate at which it's decaying. "
] |
[
"Why is it that human brains are able to \"auto-pilot\" certain commands, such as play the piano, video games, sports etc... But when we start to think about it, we completely lose rhythm?"
] |
[
false
] |
Examples of this :
|
[
"I suspect this article is what you are interesting in.",
"In short, there are different parts of the brain that are responsible for reacting to novel stimuli and carrying out tasks of habit. Different parts of the brain can suppress the activities of others. Very roughly, the more parts of the brain are involved in dealing with a task, the more time it takes for them to reach a consensus and react. ",
"I suspect that \"consciously\" thinking about something sets up a conflict between the part of the brain that carries out habitual activities and the part of the brain responsible for higher thinking and novel reactions (see article above). This comes with a \"loss of groove\" as the various parts resolve conflicting signals. It is the cognitive equivalent of an overly attentive manager inserting himself into the workers' work to try things himself and ask questions, thus slowing everything down."
] |
[
"There are 4 stages of ability at any task:"
] |
[
"The first video is a classic case of \"fire together, wire together\" wherein you develop an automatic response to a stimulus (e.g. you see a right arrow you tap the right arrow button) so you can reliably execute a complex task at a speed which would not be possible if you were consciously thinking of each individual step/move. ",
"This stuff gets really interesting when you get past simple cue-response activities, like with a piano player during a really fast part of a song where they have tied together all the motor parts required for that activity into a \"motor program\" (analogous to a macro in excel for example) through practicing it and they get to a point where to execute that motor program at the speeds they want requires them to do the whole thing.\nThese and other neural strategies result in professionals being able to enter a state of \"flow\" or something more commonly known as \"being in the zone (chief)\" where a large repertoire of complex motor programs and responses to stimuli are seamlessly strung together.",
"source: masters level neuroscience class on the neural basis of behaviour",
"poppy New Yorker article about \"flow\": ",
"http://www.newyorker.com/magazine/2011/10/03/personal-best",
"edit: spacing"
] |
[
"What's the difference between an X-ray laser and a regular laser?"
] |
[
false
] |
Would there be any?
|
[
"The wavelength of light that comes out of an X-ray laser is in the tens of nanometers, versus in the hundreds of nanometers that comes out of a \"regular\" (i.e. visible wavelength) laser and versus the hundreds of millions of nanometers that came out of their fore bearer the maser (Microwave-aser).",
"But, at the end of the day, it's all light and all the same basic mechanism."
] |
[
"Interestingly enough, in astronomy we often think of \"maser\" as a \"molecular laser\", where the amplification comes from (e.g.) molecular lines in H2O. But yeah, the original form was \"microwave\""
] |
[
"Well the 21 cm line of molecular hydrogen is fairly snuggly in the middle of the microwave range anyways, so it's a little tomato, tomato (obviously this phrase doesn't work when typed... but you get my point)."
] |
[
"Why do the gold flakes in Smirnoff Gold neither float nor sink, but instead remain suspended in the liquid? Even if you move the bottle, they don't really move."
] |
[
false
] | null |
[
"The special thing about gold foil is that it can be made to be amazingly thin- sometimes descriptors like 1 atom thick get thrown around. That means the gold foil essentially has no weight. While gold is denser than lead and would sink very easily, with gold foil the resistance from the water dwarfs the force of gravity on the gold causing it to sink so slowly that it appears to be suspended.",
"An analog might be tissue paper in air- if you have a big block of tissue paper, it falls very quickly, but a single piece falls slowly. It's the same effect except the water has much stronger resistance than air. ",
"If you wait long enough without disturbing the bottle, the foil would settle on the bottom. "
] |
[
"Good thinking. This is, however, incorrect. Brownian motion of either the particle or liquid will be symmetric up or down, since the thermal fluctuations causing them are symmetric. Since there is still a net force (gravity) pulling down, the gold flakes will sink until they reach equilibrium at the bottom of the bottle.",
"Now, you may ask, \"but when the gold flakes are on the bottom of the flask, could brownian motion bump them back up into the bottle, keeping them from settling?\" This is possible, but highly highly unlikely. You can get a rough estimate of how likely an event is to occur due to thermal fluctuations by comparing the energy required to the quantity k_b * T; the product of the boltzmann constant and the temperature. This quantity is a rough estimate of how much energy you can get from thermal fluctuations at given temperature. At room temperature, this is 4.114 * 10",
" Joules. Say our gold flake weighs about 1 microgram, it would require 9.81*10",
" Joules to bump it up a millimiter, no where close to k_b * T. Therefore, it is very unlikely that a fluctuation will come along and bump up the flake.",
"Note that I'm doing a bit of handwaving here. This is mainly because the math gets complex pretty quickly. However, if anyone wants to get a better idea of how this stuff works, looking up Boltzmann distributions and partition functions are good places to start. Also, I hope that wasn't too much science-ese. If anything is confusing or poorly defined, please tell me.",
"Source: Graduate Student in Statistical Mechanics, working on non-equilibrium dynamics.",
"P.S. Someone else defined Brownian motion as the random motion of the molecules in the liquid bumping into an object. As a fine point, I would also like to mention that the object itself has the random motion inside it's molecules: anything at a temperature above absolute zero does. This is why I can neglect where the fluctuations are coming from in my analysis, since they'll all have the same energy."
] |
[
"Well, the brownian motion of the liquid migth keep the flakes from ever settling."
] |
[
"Re: Hydrogen Peroxide. Sometimes it reacts quickly and settles down, other times it creates a thick foam that sticks around for a while. What's going on here?"
] |
[
false
] |
[deleted]
|
[
"I'd say either temperature, old/new bottle, clean glassware"
] |
[
"With the same conditions (concentration, solvent, stirring)? I'd guess the cleanliness of your glassware is at fault, any bits of iron oxide or iodide will catalyze disproportionation.",
"Whats the reaction?"
] |
[
"Right. H2O2 eventually turns to water and oxygen gas if left unopened,"
] |
[
"Spore count using a Neubauer chamber calculation"
] |
[
false
] | null |
[
"So the concentration of spores in the diluted solution is",
"335 spores per 0.1mm",
"In the undiluted solution it is 500 times that",
"167,500 spores per 0.1mm",
"Converting to spores per cc gives 1.675x10",
"Given the concentration you can find the total for any volume using the equation",
"concentration=number/volume",
"total spores=(1.675x10",
")(400)=6.7x10"
] |
[
"First find how many spores you started with. How did you get 335? What does it represent? Then divide by 500."
] |
[
"335 is the number of spores counted in 1 square mm"
] |
[
"Are there any limits to what science can explain?"
] |
[
false
] |
[deleted]
|
[
"Here is the wikipedia article on ",
"the scientific method",
" which you should read over.",
"You've asked two different questions here:",
"Are there any limits to what science can explain?",
"Are there any questions science cannot answer?",
"The second one isn't really what science is about. There are lots of questions about \"why\" things happen which can't be answered, and either way it is not the right way of going about it.",
"Scientific researchers propose hypotheses as explanations of phenomena, and design experimental studies to test these hypotheses via predictions which can be derived from them.",
"Along these lines science can offer an explanation for everything that we can observe. What occurs within the event horizon of a black hole, what occurred before the big bang, what happens to human consciousness after death, have no interaction with the physical world and there is no way, and no point, in theorizing about them.",
"There are also some situations where we can form a hypotheses or theory about how something might occur/might have occurred, but it is difficult or impossible to design experiments to test it. For example how life on Earth began or how the universe will end. There are theories which might be more plausible than others based on evidence, but without more data there is no way to build more confident models.",
"Finally it can also be argued that although scientific theories can be used to very accurately predict results, they can never be 100% proven laws. The ",
"problem of induction",
" covers this but a simple pop-culture explanation is that we could all be in the matrix."
] |
[
"Yes, science is the ability to predict the outcome of an experiment based on previous measurements. If something is beyond our capacity to probe with a measurement, then it's outside of science right now. If future technology comes along that allows us to then measure such a thing, then it gets added to science. Science is best not thought of as a static book of facts that we're trying to read over time. It's an assembly of the sum of measureable knowledge we have about the universe."
] |
[
"Science attempts to observe and explain the facts of the universe. However, I would argue (though some may disagree) that it is beyond the realm of science to answer questions of value. In other words, science seeks to understand the origin of the universe but is not interested in providing any kind of philosophical rationale. Nor is science interested in/capable of determining whether or not a work of art is good or if your life has any meaning. Even though we may someday fully understand the neurochemical mechanisms and evolutionary prompts for the human creation of value, it is up to us to assign any significance to it. That's why people who say that either science or spirituality/philosophy must eliminate the other are naïve -- the two should stick to asking entirely different sets of questions."
] |
[
"Is it possible to create a computer that uses base 10 or base n for computing, without quantum mechanics?"
] |
[
false
] |
[deleted]
|
[
"Some of the earliest computers were ternary computers, and ternary has some ",
"attractive benefits",
" over binary in terms of number representation. These benefits are offset by the structural complications of such computers.",
"http://en.wikipedia.org/wiki/Ternary_computer"
] |
[
"Yes and no. We have no efficient means of storing things other than as charge, and charge only really allows for real-analog values and high-low binary.",
"We could always store things as \"base-ten\" by assigning 4 bits to every value, but there's no reason to do this.",
"Quantum computing has ",
" This is ENTIRELY differently."
] |
[
"It's relatively trivial to construct a processor that will work with any positive integer base you would like; just interpret different voltage values. Storage of values in bases other than 2 is trickier -- our main memory (RAM) tends to use capacitors and we'd have to be careful to allow them to store and read back ",
"base",
" levels of charge. Storage memory is even worse, reading and writing magnetic domains in, say, 10 different directions would be an engineering nightmare.",
"For the most part, a computer designed this way would be horribly inefficient because of the amount of error checking and correcting that would need to be carried out to read, for example, 10 different voltage values.",
"Further, many of our logical constructs (<, =, >, etc) are intrinsically boolean and therefore translating our algorithms from high level descriptions into machine code is relatively efficient. If we were using a decimal valued CPU we'd often be wasting the additional degrees of freedom unless there was some serious compiler optimization which piggybacked many computations into a single value."
] |
[
"Why does my phone camera show the heating elements on my stovetop to be a pink/purple colour when they appear red/orange to the eye?"
] |
[
false
] |
I imagine the camera is picking up the infrared light and shifting it to visible light, but my DSLR camera doesn't do this. What is special about a phone camera that makes it do this, and why the pinkish purple, which is at a part of the spectrum away from infrared?
|
[
"When the heat is shown as red to your eye, it is shown in 600 to 900 nm light also known as red. But there is a lot of light coming off in infra red 900nm and higher.\nThis infra red light is invisible but appears as violet to your camera. ",
"Tldr your camera is showing you light you can't see "
] |
[
"The actual sensor on your camera is sensitive to a wide range of wavelengths, and it can't actually tell the difference between blue vs. red vs. infrared light. So to produce a colored image, there's a ",
"Bayer filter",
" in front of the sensor, which only allows light of particular colors to reach each pixel. (The camera's software interpolates between adjacent subpixels to generate a full-color image.)",
"Now, a color filter is just a material that absorbs some wavelengths and not others. In particular, the pigments are selected to try to match the human eye's response to visible light as closely as possible. But they're not perfect, and they allow a bit of infrared through as well.",
"Presumably, the camera in your phone was made a lot more cheaply than your standalone camera, and so its filter is lower quality and lets more infrared through. And it just so happens that the pigments used in the green filter block more infrared than the red and blue filters, but nobody can really say ",
" without knowing their actual chemical composition."
] |
[
"When I was at uni we were using Infrared LEDs in circuits and we'd use our phone cameras to check if the LED was turning on - pretty handy"
] |
[
"Is the speed of sound directly proportional to density of the medium ? And if so, at how high density would sound travel faster than light ? If it's even possible."
] |
[
false
] |
[deleted]
|
[
"The speed of sound is inversely proportional to the square root of density of the medium (c~(1/sqrt(ρ) ) ), meaning the speed decreases with higher density.",
"However the speed increases with decreasing compressibility and as liquids and solids are much less compressible than in gases the speed of sound is much higher in solids (even though the density might be higher).",
"The medium with the highest speed of sound is probably be a neutron star with something up to 1% of light speed."
] |
[
"The medium with the highest speed of sound is any relativistic gas, with 58% of light speed."
] |
[
"Speed of sound is related to density, and can be shown through experiment.",
"Put a 100m railway line down, then have someone simultaneously shoot a gun in the air and strike the metal rod- a person at the far end will feel the rod move before they hear the gun.",
"Sound is a pressure wave, so its speed depends on several factors, including density and temperature of the material."
] |
[
"What is the white light people describe as they are dying?"
] |
[
false
] |
[deleted]
|
[
"Seeing bright light in the manner you describe has been correlated with loss of consciousness experiences from lack of blood flow to the brain / high carbon dioxide. This is actually a suspected contributor to most near death experience phenomena like outer body experiences and life flashing before your eyes.",
"Maybe a neuroscientist can give you a more detailed answer. But Brian Dunning did a really cool article on this near death experience stuff and it's well referenced. ",
"Here"
] |
[
"Thanks."
] |
[
"No one is quite sure. Wiki has a couple of studies into what causes it:",
"'Strassman advanced the theory that a massive release of DMT from the pineal gland prior to death or near-death was the cause of the near-death experience phenomenon.'",
"'Research released in 2010 by University of Maribor, Slovenia had put near-death experiences down to high levels of carbon dioxide in the blood altering the chemical balance of the brain and tricking it into 'seeing' things.'"
] |
[
"So, how does voltage actually work?"
] |
[
false
] |
Sorry if I come off as overly obtuse here, but I have been failing to grasp how this concept works for ages. I know that voltage is the 'potential difference across two points', but what does that actually ? What's the difference between electrons moving at 1v, 10amps, and 10v, 10 amps? What quality is it that they possess?
|
[
"Imagine pushing a cart down a road.",
" = how hard you push",
" = how rough the road is",
" = how fast you wind up going"
] |
[
"A great analogy is a watercourse, just exchange electric potential for gravitational. A river flows downhill because there is a potential difference, just as an electron moves in a wire because of an ",
" potential difference. The steeper the drop, the faster the river. ",
"Electron drift velocity is linearly dependent on velocity, so in your example, they'd be moving at 10x the velocity in the second case. (Don't confuse the velocity of the electrons for the rate the signal is propagated at.. that happens at the speed of light)"
] |
[
"And ",
" "
] |
[
"How does a multimeter measure current and voltage?"
] |
[
false
] | null |
[
"Historically, electric potential (voltage) and current (amps) were measured using induction.",
"Electricity induces magnetism in predictable ways. This principle is how your doorbell works. You can build an analog galvanometer (which is a coil in a magnetic field). When current runs through the coil, it induces magnetism, which interacts with the permanent magnetic field around it. This moves a needle, and you've measured amps. If you want to measure alternating current, you'll need to rectify the electricity so that it only moves in one direction (if you think about alternating current, you'll see why you need to do this).",
"Now, if you also want to measure volts, you can use the exact same device and drop a resistor in. Because the way induction works is so predictable, you can put resistance on the circuit to check potential. You can even use the same device to determine what that resistance is by introducing a known current that would rotate the coil all the way, and calibrating your device so that you can check how close it got.",
"So there you go - induction makes the multimeter work."
] |
[
"Analog meters use the ",
"D'Arsonval movement",
". Basically, in 1820, Hans Oersted noticed that a wire carrying current would deflect a compass needle."
] |
[
"You didn't actually answer how either of those devices measures volts or amps."
] |
[
"[Astrophysics] What evidence do scientists use to support the claim that the big bang caused our universe to emerge from a point smaller than a single atom?"
] |
[
false
] |
It's a wordy title, but that's all I'm asking. I hear this referenced often on scientific shows/movies/text books. How could scientists know that the universe emerged from a point smaller than a single atom?
|
[
"How could scientists know that the universe emerged from a point smaller than a single atom?",
"I don't know of any credible scientist who will say this. It is true that the early universe was very dense and, by extrapolation, the entire ",
" universe may have occupied a space smaller than an atom. However:"
] |
[
"When astronomers talk about the Universe that usually implies the visible Universe.",
"In the current paradigm of Physics, there are two leading models for describing the Universe. The Standard Model of particle physics and the Lambda Cold Dark Matter model. So a model for creating the Universe must be able to create the Universe using what these models give you and it must also be able to account for all other experiments (the Cosmic Microwave Background, observed elemental abundances, etc.). When this is done in the optimal way, you end up with a Universe that stars of in a single point of space. "
] |
[
"Well I most recently heard it from Neil deGrasse Tyson on the remake of Cosmos. I know he's very popular, but I don't know how credible his word is."
] |
[
"Is it unrealistic for a fighter to kick or punch with 1000 PSI in a fight?"
] |
[
false
] |
[deleted]
|
[
"Punching force for professional/Olympic boxers is usually between 500 and 1,000 lbs. For instance, on Sports Science, MMA fighter Houston Alexander generated around 800 lbs. force in a punch, and Rampage Jackson can deliver a 1,800 lb. punch. If you assume this is distributed over the face of an ungloved fist, you get around 80 - 280 psi.",
"Fighters can generate much more force in a kick. UFC light heavyweight champion Shogun Rua has recorded kicks of about 2750 lbs. of force. This force was distributed over the top of his foot and ankle, so the area is something like 6 in. x 2 in., yielding 230 psi pressure. Keep in mind these are average figures, and instantaneous, localized forces and pressures will vary.",
"So is 1,000 psi unrealistic? I hesitate to say \"unrealistic,\" but it's certainly quite a bit higher than what top fighters have recorded. Then again, these types of forces are usually not measured as pressure, but as force. The pressure could easily be manipulated to reach 1,000 psi by adding something that concentrates the force over a smaller area, like brass knuckles. And 250,000 psi isn't out of the question if you were to rig a nail to a fighter's fist. (Which alludes to why force is a more useful measure than pressure in this case.)",
"Edit: Added summary paragraph for clarification."
] |
[
"No trained person just throws their fist at a person's jaw like a projectile, as if they had tossed a ball. A proper punch's power comes from the rotation of the puncher's core and is extended through their arm into the fist. A large percentage of a punch's power comes from the ",
" if done properly, and can have well over a hundred pounds of mass behind it."
] |
[
"If a fist has a cross sectional area of four square inches and a mass of one pound, and the punch goes from 50 km/h to zero as it impacts the face over a distance of one inch, that is about 100 PSI. I estimated most of those numbers, it's not inconceivable that it's higher. I suppose if all of it was delivered through one knuckle the pressure would be much higher."
] |
[
"Is gasoline entirely homonegous? If I buy Venezuelan gas at Citgo, is it any different than gas from oil from Saudi Arabia or Texas? Or does the refining process remove all differences?"
] |
[
false
] | null |
[
"Just a small correction to this, the octane rating is based on how the fuel acts compared to a fuel that was composed of n-heptane and iso-octane. So if you octane rating is 80, the fuel would act the same way (in regards to knocking) as a fuel mixture of 20% n-heptane and 80% iso-octane. It does not necessarily mean the gasoline actually contains 80% iso-octane. This is how you can have octane numbers of 130 for example, this fuel is more resistant to knocking than pure iso-octane is."
] |
[
"I won’t go into the question of additives – each brand of gasoline has its own formulation and ",
"mix of additives",
" – these will obviously make the product at the pump different from one brand to the next, but it is a bit of a trite and trivial answer.",
"There are, however, some variations induced by the refining process. Some are deliberate. Gasoline is not a pure substance, but a mix of hydrocarbon chains of different lengths, say C4 to C12. For instance, regular will have less of the longer-chained hydrocarbons in the mix than super, so that’s a difference right there. This is what is meant by the octane rating - which indicates what proportion of your gasoline is made up of the eight-carbon molecule octane. Different batches will also have slight variations in the relative ratios of each specific molecule. Not huge, but measurable.",
"Then, there are stable isotope signatures. These are cool. Hydrocarbon deposits form with a certain initial ratio of carbon isotopes (C",
" to C",
" ); these will vary with local temperature conditions when the initial source organisms were alive and a few other processes during diagenesis and maturation - long story shorth: these signatures are different for deposits from different time periods (see, for instance: ",
"Fuex, A. N. (1977). The use of stable carbon isotopes in hydrocarbon exploration. Journal of Geochemical Exploration, 7, 155-188.",
"). These signatures are not affected much by the refining process, so, provided you do not mix material from different deposits during cracking, you should be able to distinguish gasoline produced from deposits with a different initial isotopic signature."
] |
[
"Since this is ",
"/r/askscience",
" you've gotten the chemical answers to your question but I'll add something about the market too. ",
"Gasoline is what's known as a fungible commodity, like non-organic whole milk. When one supplier has too much, it sells it as a generic product to another buyer. For example, if Exxon cooks too much gasoline then they will sell the \"leftovers\" to a different company. You might ask why they would give their competitors a supply, but the process of making gasoline is expensive, long, and complicated, and disposal so difficult, that they really only need to make pennies on the dollar to justify the sale. "
] |
[
"What can we make using the 6 elements in the /r/askscience logo?"
] |
[
false
] |
What sort of substance could we theoretically synthesize containing all (but not necessarily limited to) the elements in question: arsenic, potassium, scandium, iodine, neon and cerium? Slept through most of my high school chemistry, so if something exists in nature with those components, I'll take that too.
|
[
"Pretty much none. Neon is a noble gas which won't form compounds with much and definitely not with all of these at any reasonable energy. You might be able to squeeze everything but Ne onto some long molecule all as substituted atoms, but even that would be a stretch. The only compound that sticks out containing two of these is potassium iodide though I'm sure cerium/scandium iodide are kicking around and maybe a few arsenic compounds as well."
] |
[
"I see... because of its \"nobility\", Neon refuses to associate with the \"commoner\" elements. "
] |
[
"But goes off like a rocket when she parties with hydrogen"
] |
[
"If motion is relative, how do you determine which frame of reference experiences time dilation?"
] |
[
false
] | null |
[
"An observer will always measure time to pass at the same rate in their own inertial frame, and slower in other inertial frames.",
"You will observe the clock by the stop sign to tick slower than the one in your car.",
"Similarly, someone standing by the stop sign will observe the clock in your car to tick slower than the one next to the sign."
] |
[
"Thanks for the response; I'm sure you're correct, but let me explain my own thought experiment that seems paradoxical to me. Hopefully you can help me see where I'm not thinking correctly:",
"Okay, so in the above case with the stop sign and the moving car, if we timed how long it took for the car to move from point A to point B, which stop watch would record the lesser elapsed time? The one on the ground or the one in the car?",
"It seems like that would mean that from the cars perspective, time passes more slowly for the stop sign, so the the stop watch on the ground would record less time elapsed for the car to drive from point A to point B.",
"On the other hand, from the stop sign's perspective, time passes more slowly for the car, so the ",
" stop watch should record less time elapsed as the car moves from point A to point B.",
"They can't have both recorded less time than the other."
] |
[
"This is essentially a variation on the ",
"Twin Paradox",
"It's a very common gripe that people have when learning about special relativity"
] |
[
"What would happen if two gas giant type planets collided?"
] |
[
false
] |
So say something crazy happened with the Sun's gravitational pull, and Jupiter and Saturn collided. Being gas giants, how would that work? Would they destroy each other or would they merge to form a bigger gas giant?
|
[
"They would most likely merge. From the outside, the collision would look very \"soupy,\" for lack of a better word. They would appear to behave more like a thick fluid than anything else during the collision. "
] |
[
"Neptune and Uranus ARE gas giants."
] |
[
"Neptune and Uranus ARE gas giants."
] |
[
"How much faster/ stronger would wind be if trees and other obstacles weren't there to obstruct it?"
] |
[
false
] |
I know there are several variables such as geographic location. Also if there hasn't been a study regarding this, what are some of your best guesses and why?
|
[
"Near surface winds are strongly influenced by the thickness of the boundary layer at the base of the atmosphere. The effect of obstacles at the surface is characterized by the ",
"roughness length",
". If you removed the trees the wind at ground level would be faster but the quantitative increase would depend on what it was replaced with: cropland, grass, mud? "
] |
[
"There are areas of the world with very little ground cover. Salt flats, for instance, have near-constant, very-high winds. Hell, the Mojave, while not completely flat, has near-constant wind, though it wasn't very strong while I was there. Basically, the less trees and stuff you have, the faster wind will go. There is an upper limit due to friction with the ground and with itself, but yeah, it'd be very windy."
] |
[
"The most obstacle-free area you're going to encounter on the Earth has got to be the Ocean. If you're interested in wind, I suggest you read about the trade winds and westerlies and so on.\n",
"http://en.wikipedia.org/wiki/Trade_wind"
] |
[
"Are there any diseases that affect both plants and animals?"
] |
[
false
] |
If not are there any diseases that would be especially scary if animals could contract them?
|
[
" ",
", also known as the black bread mould, is one species amongst a small group of mould fungi that can parasitise both plants and animals. You've almost certainly seen it growing on old bits of bread and other foodstuffs you've forgotten about at the back of the refrigerator n' cupboard. Alongside growing on decaying food, it can also infect the tissues of living plants, and occasionally animals such as ourselves, causing ",
"zygomycosis",
". This can be fatal.",
" Cancer is also a disease universal to all multicellular life, though cancer in plants acts in a ",
" way to that in animals and it doesn't ",
" harm them. ",
"For background; cancer is basically a population of cells that's mutated in such a way that they've overcome the natural control on cell division and multiply uncontrollably. In animals, they divide, within fairly malleable tissue compared to plants, to such an extent the tumour eventually breaks through into the vascular system, at which point the cancer cells hitch a lift around the body in your blood, forming daughter tumours pretty much everywhere (known as metastasis) and, well, things aren't so peachy.",
"Plants lack an equivalent vascular system - the xylem and phloem they use to transport water and nutrients through their stems cannot pass large cells (plus, plant cells are rigid in structure, so couldn't get into them anyway). So cancer cells in plants - which crop up at a lower rate anyway compared to animals due to their low metabolic rates amongst other things - are stuck where they began, and only grow locally.",
"It's actually exceedingly common. If you look at any old tree, you'll notice a whole loada' lumpy galls n' burls - ",
"these are tumours",
". Indeed, some animals even take advantage of how tumours develop in plants to induce them on purpose for various reasons, such as gall wasps who induce 'em to provide shelter for their growing larvae. ",
"So yup, cancer in plants, particularly long-lived trees, is common but by no means much of a burden on their system and so they can proverbially shrug it off to a large extent. ",
"Erm, but anyway, aside from cancer and the odd opportunistic fungus, I can't think of anything else!",
" ",
" ",
" ",
" "
] |
[
"One controversial idea in my field: whether prions (infectious proteins) are taken up by plants, where they may be harbored and concentrated before later being consumed by the mammalian host, transmitting the agent.",
"The plants aren't specifically ",
" though they could still be considered ",
" with the prion. "
] |
[
"There are quite a few pathogens",
", scroll to Table 1. ",
"The short answer is yes, but a typical plant pathogen infecting humans is not that common, because pathogens usually establish a niche in a host where they like to live. Unless there is a good reason, like loss of its habitat/environment, pressure from a toxin/chemical, opportunity in a human host, plant pathogens usually like to stay with their niche host.",
"edit: grammar and typos"
] |
[
"Do noise canceling headphones harm your ears because it doubles the energy going into them?"
] |
[
false
] |
[deleted]
|
[
"Sound is a mechanical wave resulting from alternating compression and rarefaction of the medium it travels in. So when two waveforms cancel out, this means that mechanically, there is zero movement. So although on the outside it seems like they might add up, the motion of the air caused by the speaker in your headphones are synched so as to exactly cancel the noise. That is, the ambient noise moves the air one way and the speaker moves it right back to where it was, and all that before it hits your eardrum. So actually, if the noise cancellation is perfect, zero energy hits your eardrum. ",
"Cred: Currently taking engineering physics as part of mechanical engineering major"
] |
[
"Follow up question:\nWhat happens is destructive interference, right? I was wondering, what becomes of the energy in the two waves when they cancel each other out?"
] |
[
"You're probably curious about how it can be that the noise cancelling headphones emit noise, and yet they don't emit sound into the ear. The reason, as you guessed, is that the sounds cancel out in your eardrum, reducing the perceived sound. So that raises the question... Where did that energy go that the headphones emit? The answer is that the energy goes out in most directions except towards your ear. ",
"So the headphones effectively act with the ambient noise as a beamformer, sending slightly more noise in all directions except towards your ear.",
"Cred: I work building a sonar system. "
] |
[
"Is there any scientific validity to the technique of deep breathing as a cure to anxiety?"
] |
[
false
] |
Hi , I'm a long-time sufferer of anxiety. Popular 'wisdom' has told me that slow deep 'diaphragmatic' breathing is the best cure for this. Is there any kind of scientific evidence for this?
|
[
"Breathing deeply and steadily will reduce your heart rate and help relax constricted muscles in the chest and neck, reducing physical stress and helping to calm you down through lowering blood pressure. Additionally, breathing in such a way usually requires conscious effort and when a person focuses on their breathing, it also helps take the mind off of what is causing the feeling of anxiousness. "
] |
[
"I'm curious about how effective this is when the stressor that is making you anxious to begin with is your breathing."
] |
[
"When people begin to ",
"panic",
" they tend to start breathing faster and with less volume (shallow) which decreases oxygen intake (think brain) and decrease carbon dioxide output. These both chemically amplify the feelings of panic and so slow deep breathing is the best way to resolve at least this problem. Along with the already mentioned distraction and decrease in blood pressure it's the possibly the best thing you can do in a panic inducing situation."
] |
[
"Could a solar flare knock out consumer electronics without an antenna?"
] |
[
false
] |
This came up as the result of the most recent solar flare which is supposed to have a coronal mass ejection which will hit the earth, or so my mom said. She's convinced that she needs to wrap her laptop in tinfoil so that it will be shielded from the solar storms. I'm highly skeptical that a small laptop without major transistors will interact in a meaningful way with a solar flare hitting the magnetosphere, especially considering how short the antennae are on any given laptop. Can anyone say for certain if this (or any future) solar flare is cause for concern for consumer grade electronics? Assume its decoupled from the power grid at the time.
|
[
"I've been designing electronic circuits for 30 years. I'm not aware of any way for solar flares to damage electronic devices, except perhaps some sort of rare, fluke occurrence.",
"I think we get solar flares regularly, and I don't remember any case where TVs and radios were damaged on a widespread basis."
] |
[
"I can understand the idea where the mass of solar flare hits the magnetic field of the earth, causing a sharp electromagnetic spike, which is picked up by, say, the Wi Fi antenna on a laptop and burns out the computer.",
"I can see all that in theory, but I'm a but skeptical in practice. So far no one has confirmed it."
] |
[
"Yes, short answer: don't worry about it."
] |
[
"What is Between Galaxies?"
] |
[
false
] | null |
[
"In terms of stars - there are very few stars between galaxies. If you were half-way between the Milky Way and Andromeda, you would see a sky that was almost completely black. Galaxies are quite dim overall, so you can't really see them unless they're pretty close. That means you'd only see the few nearest galaxies. If you've seen Andromeda at night, you'd basically have a couple of those in the sky, and that's it.",
"There are rogue stars and planets between galaxies, but not very many. We have spotted some very high-velocity stars being thrown out of our galaxy. Close encounters between stars or between a star and a supermassive black hole can cause the star to get kicked out of the galaxy.",
"If you're in a galaxy cluster, where there's lots of galaxies in a small space, then there are a lot more of these intergalactic stars. The Milky Way is in a \"group\", which is a small and loose group of galaxies, but if you're in a \"cluster\", then there are a lot more galaxies in a smaller space, and they bump into each other more often. Their gravitational forces can rip stars off other galaxies, so you get a small but not insignificant amount of stars floating around in the cluster that aren't attached to any particular galaxy. We can detect this with telescopes - it's the \"intracluster light\". But I don't think you'd really be able to see it with the naked eye.",
"There is also a ",
" of gas between galaxies. About half of the \"baryonic\" mass of the universe (that is, the \"normal\" mass made out of atoms - we aren't counting dark matter) is actually in a million-degree super-thin gas that fills the spaces between galaxies. It's a lot of mass, but it's spread out over a huge amount of space, so the density is really really low - even lower than the gas within a galaxy - but it exists."
] |
[
"Well, we can see other galaxies from here, so their light has to cross the gap. As far as planets and things, that's harder to say. We determine the existence of exoplanets by the way they interfere with the light from luminous bodies.",
"The intergalactic space is so large that the probability of detecting a rogue planet out there is very very low. It's more likely that we would be looking at something else and a planet would trundle across like your roommate when your show is on. Even then, confirmation would be difficult because we would have to estimate it's procession and start looking at something else we expect it to cut in front of. Not an easy task.",
"Even with the light from other galaxies, it would be dark. Really dark. As an example of scale, our sun doesn't look much different from any other star when you get out toward Neptune's orbit. You would have a similar effect with the light crossing the gap when standing on the edge of the galaxy."
] |
[
"There might be tiny amounts of molecules within them, but we can more or less talk about a vacuum. Then there are some asteroids or planets that got kicked out of their galaxies.",
"There certainly is light. Otherwise we wouldn't see other galaxies"
] |
[
"How does a warm-blooded fish evolve?"
] |
[
false
] |
Maybe a week ago there was big news about the first discovered , the opah. Apparently limited, localized warm-bloodedness is not unheard of in fish, but how does a full-blooded fish like the opah evolve? Is there some kind known evolutionary history (is that the word?) that led to it? Also, what is it about the opah's niche that it and only it developed full warm-bloodedness?
|
[
"A couple things seem to be going on here. First, this fish isn't metabolically warm-blooded like mammals and birds, the heat comes from constant muscle contraction. That generates heat in any animal, it's just that this particular fish has a whole set of adaptations focused around trapping that heat in the body. Even so, it's only running 5c hotter than the surrounding environment.",
"I would not at all be surprised to learn that other related fish have or had similar adaptations, but there are only two fish in the genus and no other close relatives, so it may not be widespread. I bet there are some other warmblooded fish out there that have also simply escaped notice, though.",
"As to what about the niche makes this useful; these are open water active swimmers, and this adaptation may help keep them moving fast in cool waters. Off the top of my head, other instances of partial warmbloodedness in fish come from animals occupying similar habitats."
] |
[
"I'm pretty sure certain sharks, like Great Whites, have a similar system with their tail muscles. ",
"Thanks, Shark Week!"
] |
[
"Was just about to say this! I believe Great Whites, and others in the family too (like Salmon Sharks IIRC) are \"warm blooded fish\" as well, but again they aren't warm-blooded in the same sense that we are. Rather than being warned metabolically, they have \"heat exchangers\". Pretty amazing, really, and a good example of an adaptation for a given environment. "
] |
[
"Would a diabetic with 100% optimal injections see any symptoms?"
] |
[
false
] |
So if someone injected the right amount of insulin at all the right times would they see the symptoms of the disease such as nerve damage?
|
[
"Sorry, I don't have a real answer for you, but my endocrinology professor loved to tell us that no one knew how to administer insulin perfectly, because otherwise there would be no symptoms (hypoglycemia, etc) or long term effects of diabetes despite the insulin treatment.",
"Just my personal guess - there may be other factors going on that we don't know about when it comes to insulin injection. For example, natural insulin production involves the formation of a byproduct called C-peptide that gets released in equal quantities as insulin. Too lazy to go through my notes to find the source for this, but there's an idea that administering C-peptide along with insulin might be better than insulin alone because the C-peptide has other cellular effects (none of which I know)."
] |
[
"It depends. If you are talking about type 1 diabetes, the DCCT showed quite well that tight control of blood glucose with insulin prevented chronic complications. There's hope that the artificial pancreas, which monitors blood glucose and injects insulin and glucagon, might greatly improve euglycemia, however trials are still ongoing. ",
"With type 2 diabetes, the answer is probably no. It's much more complex and injecting insulin isn't as useful because the main problem is insulin resistance, not an absolute insulin deficiency. Trials such as UKPDS, VADT, ADVANCE, etc haven't been as successful as DCCT."
] |
[
"Just for the record, to my knowledge, no one is working on a true artificial pancreas. All such attempts are being made with external insulin pumps delivering insulin subcutaneously and monitoring interstitial fluid subcutaneously, both from external devices.",
"A true artificial pancreas would have to be implantable so that it could deliver insulin to a vein and monitor blood sugar.",
"As long as subcutaneous insulin delivery and monitoring are used, there will never be adequate control for calling anything an artificial pancreas. Insulin absorption will be too erratic as will the monitoring of interstitial fluid. These devices do not work, for example, in long car rides where the subcutaneous fluids are not moving and insulin is not being absorbed."
] |
[
"Has a computer ever done a mathematical proof?"
] |
[
false
] |
If not how far away from something like that are we? Could it be possible to have a computer brute force its way through a proof. Could you do supervised learning by feeding it lots of proofs until eventually it learns how to go about it?
|
[
"Sure. There are a few different categories of such things:",
"Computer-assisted computational proofs. The proof of the ",
"Four Color Theorem",
" is perhaps the best-known example of this; humans put together a framework to reduce the proof of the Theorem to a few thousand computations, then turned a computer loose on them.",
"Formal proof verification. In principle, every mathematical theorem should be provable by some finite sequence of statements of axioms and logical manipulations. Within certain constraints, this is a good job for a computer, and many software packages exist to perform this task.",
"Theorem generation. In principle, given sufficiently clever algorithms, a computer could generate not just proofs but whole new theorems (which is to say, new conjectures together with proofs of them). This is the most open-ended of the three, and by far the most challenging, but it has in fact been done. The example I'm familiar with is Dekov's \"The Machine for Questions and Answers\", which he evidently has used to cook up hundreds of theorems in Euclidean geometry, some of which may even be interesting."
] |
[
"Hell, ",
"computers have coauthored papers",
"."
] |
[
"A recent example of this is mentioned ",
"here",
", using Coq software to \"prove\" (verify) the Feit-Thompson Theorem."
] |
[
"Can a venomous animal be affected by its own venom if it were to enter its bloodstream?"
] |
[
false
] |
[deleted]
|
[
"Wow, 13 hours and no answers. I know for sure that venom is kept in special sacs to segregate it from the other organs, so I'm inclined to say \"yes\". (I don't normally provide layman speculation, but I guess it's better than nothing.)"
] |
[
"This is an interesting question actually, and still under debate. \nHowever, giving the precise wording of your question, I would have to say that yes the snake would be 'affected'. "
] |
[
"I too am curious. If a poisonous puffer fish for instance cut himself on a coral reef would it poison itself? Tetrodotoxin kills in seconds so I cant imagine an enzyme saving the fish in time."
] |
[
"Why do compressed air cans stop working and then regain a 'charge' after sitting for awhile?"
] |
[
false
] | null |
[
"There is also the significant temperature drop that occurs in the can. So the gas in the can at low temperatures reduces the pressure. As you increase the temp the pressure will increase in the can again allowing for more use. PV=NRT."
] |
[
"Compressed air comes in a can as a liquid with a high ",
"vapor pressure",
". As the liquid sits in the can, a portion of it evaporates until the gas equilibrates with the liquid at a pressure much higher than the atmospheric pressure. When you pull the trigger, this gas escapes to equilibrate the internal pressure of the can with the atmospheric pressure. Once the pressure in the can is equilibrated with the pressure outside the can, it will no longer blow air. Any further evaporation of the liquid with the trigger pulled immediately equilibrates with the pressure outside the can, and you can't build up a pressure differential. Letting it sit for awhile gives the liquid time to evaporate and equilibrate to the higher vapor pressure of the liquid, and then it's 'charged' again."
] |
[
"Boyle's Law: (p",
"Rs",
"p=pressure\nV=volume\nT=temperature\nm=mass\nRs=a gas constant",
"When you spray, the mass in your can decreases. That means that the right side of the equation is \"off\" wich means the left side needs to compensate. The pressure decreases, the volume stays the same which means the temperature must decrease as well to maintain the equation. If you wait a while after spraying, The can will start to absorb heat from the enviroment. When that happens, the T in the equation rises again, which must mean the p increases as well. So now you can spray again"
] |
[
"Do placebos effect some people more than others?"
] |
[
false
] |
I've seen many research papers that compare treatment effects to a placebo effect as a way of controlling for error. My question is, has there ever been meta-analyses type research conducted on these sorts of papers to determine if a placebo effect is just as likely to occur in any participant with regard to factors such as gender/age/race/educational level etc. i.e. Are men more likely to respond to a placebo then women, or vice versa? And other such questions
|
[
"Well, it's kind of specific, but yes; here's a recent paper that suggests that people with a certain genetic variant are more likely to experience a placebo effect for irritable bowel syndrome: ",
"http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0048135",
"Here's another study, this time for pain relief, that found another genetic variant: ",
"http://www.nature.com/mp/journal/vaop/ncurrent/abs/mp2013124a.html",
"Of course this doesn't address the original question regarding broad and easily identifiable classes of people. A handful of references suggest that gender doesn't play much of a role; beyond that, a quick search doesn't turn up anything."
] |
[
"I think generally it is expected that ",
"personality types",
" play a bigger role in placebo than gender, age or race. A huge chunk of placebo is you believing you are getting a real drug - so people that will tend to think that this is the case will tend to respond. Age/experience could play a role in specific forms of placebo treatment (e.g. this newfangled cell phone in your pocket will heal you). But generally, it's thought that your personality, more than your socioeconomic status, race and gender impact your response."
] |
[
"I don't recall the specific reference off hand, but a placebo that causes side effects can cause increased placebo response. This untoward effects can be cues to suggest that you are in fact receiving the active medication in a study and so enhance the placebo response."
] |
[
"Is there something like an \"immediate concentration overflow\"?"
] |
[
false
] |
I'm a math undergraduate, and when I learn mathematics, there are times where I try to "switch a button" inside my head in order to gather and connect much more information at a time. Now, this might seem kind of weird, but it actually works. Do you remember the first time ever you drank a big cup of coffee or something like that? That's the same feeling. I feel highly alert somehow, and it does seem to make me think much quicker. I cannot tell how I do it exactly though. A necessary condition for it is to move my eyes quickly from one site to another, and it feels like the emotions inside my stomach are flooding my whole body. Did you ever see those movies about geniuses and the way the information they connect is visualized? It feels the same for me, but only for a short amount of time. Because on the downside, this leads to an enormous amount of stress. Yesterday, after trying to do "it" for about half an hour, it took me about several hours to reduce this stress, it felt like I sat a whole day between children who constantly screamed at me. Plus, I quickly reach the point where I simply cannot concentrate any longer, it's like all the information given in the book simply hit against a wall in front of my head and all the "magic" disappears. It feels like an "immediate concentration overflow". Is there any explanation for what I experience from a scienific point of view? Is it just placebo? And what induces the stress to this enormous degree? If you need any further information, feel free to ask.
|
[
"You may be inducing your adrenaline in order to think as best as you can. Doing so burns calories fast and if you're not prepared, you can easily burn out much the same as if you were to sprint for 20 metres versus jog for 100 metres. You are able to focus instantly and get into a zone, but our minds are designed to be able to take in large amounts of information rather than specific information. "
] |
[
"What do you mean by the last sentence?"
] |
[
"Our brains aren't designed to laser focus onto something particular, such as being able to see telescopically or completely focus on calculating integers or something like that. Doing so would make us terrible predators. Our brains are constantly inputting balance, sight, sound, smells, tastes and more with each sense determining more than just that itself. For example, you aren't just looking at stuff, but you're having to distinguish depth and distance, colour, identifying items of interest or threats and all of that. If our brains were designed to only discern 5,000 shades of red and only hear a frequency of 24khz and only taste salt then we would be at a disadvantage but we'd do those things really well.",
"Essentially you're forcing your brain to do something it doesn't want to and isn't meant to do, so it wipes out easily, even short-circuiting somewhat. Think about it the same way that a CPU is programmed to handle many different types of instructions rather than just one. "
] |
[
"How does water pressure in a siphon change over its length?"
] |
[
false
] |
If I have two barrels, one full and one empty, and I run a hose from the bottom of the full barrel over the lips of the barrels to the bottom of the second barrel and start a siphon, is the water pressure in the siphoning hose the same throughout the length of the siphon?
|
[
"Chemical engineer here. No, the pressure in the siphoning hose is not the same throughout. Friction between the tube walls and the fluid creates a pressure gradient from one end of the tube to the other. When there is flow, there is a pressure gradient. This formula sums it up.",
"∆p/ρ + ∆(v2)/2α+g∆z +F = W"
] |
[
"I only have high school physics knowledge. But I am wondering if this would be an explanation, since I do not fully understand yours: ",
"The water in barrel A causes pressure (p=h",
"ρ). Since the air pressure on both sides is equal you do not have to take these into account. Now the water flow is caused by de pressure from the water, which pushes the water through the hose. Since (I believe) pressure is dependent on the volume, the extra volume of the hose (up to the point where the water is, or where you a measuring) would cause a lower pressure at that point than at the start of the hose. ",
"Is this a workable explanation or am I wrong here?"
] |
[
"I don't think I understood your explanation. However, it's not really the effect Pikachusesks is describing.",
"The friction between the tube walls and the fluid builds a very thin layer of slow-moving fluid near the walls. This is called the boundary layer. As you travel along the pipe, slower moving fluid also interacts with faster moving fluid in the center, and slows some of that center fluid down. This means the boundary layer grows (is thicker) as a function of length.",
"Furthermore, to maintain conservation of mass, the fluid at the center must move faster further down the pipe since it's essentially being choked through a smaller area, due to the growing boundary layer. Since water is essentially incompressible, Bernoulli's equation forces the pressure to change as this velocity changes, which means a pressure gradient in the axis of the pipe exists.",
"Now, this effect isn't always a very large one, but it exists. A fun thing to think about is that, for an infinitely long pipe, the centerline velocity of a fluid can become supersonic. Of course, the pressure drop would be excessive and would require a ridiculously powerful pump, but still."
] |
[
"Where does the energy come from in capillary action?"
] |
[
false
] |
involves a liquid travelling up a porous substrate, seemingly of its own traction. Where does the energy come from for this movement to occur? Should the substrate be considered an engine in the sense of energy transfer?
|
[
"The liquid that is drawn upwards is becoming bound (\"stuck\") to the substrate. Removing it from the substrate—by whatever means—requires at least as much energy as the gravitational potential energy that the fluid gained through the motion.",
"The motion is ultimately the result of electrostatic interactions between molecules. "
] |
[
"The energy is positional potential energy that's effectively been there due to the initial conditions at the beginning of the universe.",
"What you're asking is analogous to asking where the energy of a meteor falling from outer space came from. It came from it just existing far away from the earth then falling down into the earth's potential well.",
"Another analogy is asking where the energy in stars comes from. Solar energy comes from the potential energy associated with hydrogen atoms ",
".",
"Water, due to simply existing NOT in contact with the substrate, has potential energy. When it gets close enough to the substrate the water \"falls down\" the electrostatic potential energy well into contact with the substrate."
] |
[
"The Wikipedia entry didn't really explain it for me; it showed me the calculations that calculate the amount of energy involved, but it didn't really tell me where the energy ",
"."
] |
[
"Two of the same type of metals will bond together in space?"
] |
[
false
] |
Just got a interesting Snapple fact! Says that if two of the same type of metals touch in space they will bond together permanently! Why does this happen? And when it does how fast does it occur?
|
[
"It is called cold welding or vacuum welding. Richard Feynman explains it as such:\n\"The reason for this unexpected behavior is that when the atoms in contact are all of the same kind, there is no way for the atoms to “know” that they are in different pieces of copper. When there are other atoms, in the oxides and greases and more complicated thin surface layers of contaminants in between, the atoms “know” when they are not on the same part.\""
] |
[
"What's really neat is that you can even watch this process happen in real time. For example when you take two small crystalline chunks of a metal and you put them together, when they touch in the right geometry, they will simply snap together to form one solid crystal, ",
"as shown in this video",
" for two nanowires. As Feynman so nicely put it, from that point on as far as the electrons are concerned they only see one continuous network of atoms (the lattice) that they can zig-zag through. ",
"The trick to getting this welding to work is just that you need very clean and well-defined surfaces so that the atoms on the surface of each bit of metal can come into contact with each other. On Earth we can get there by using a high vacuum, as shown in the video. Doing the same thing in space is even easier since you automatically get an ultrahigh vacuum without even trying."
] |
[
"The ideal scenario for cold welding is that you have two atomically flat and crystalline pieces of the same material that come together into the right orientation. In that case, welding is easy as it requires very little change in the position of the atoms that come together. ",
"Once you get away from this ideal case, something has to give because you now have to rearrange the atoms for the weld to work well. For example, think of the structure of a typical polycrystalline material ",
"as shown in this cartoon",
". During the formation of the material the individual grains keep growing until they physically block other and become locked in place. Clearly you have no chance of two pieces of such a polycrystalline material having the right structure at the surface that the grains at the surface lining up nicely as happens for perfect single crystals. In practice you solve this problem in a very elegant way by simply jamming one piece on top of the other at high pressures. The pressure will disrupt the atoms in the grains at the surface until the interface rearranges enough to produce something that more or less resembles the bulk material."
] |
[
"How come liquid oxygen is magnetic where as liquid nitrogen isn't?"
] |
[
false
] | null |
[
"An oxygen oxygen bond has two unpaired electrons. Unpaired electrons are responsible for magnetism. A nitrogen nitrogen bond has no unpaired electrons (because the two electrons that are unpaired in oxygen oxygen don't exist in nitrogen nitrogen). You might want to look up Molecular Orbital theory."
] |
[
"I'd just add ",
"this graphic",
" since it illustrates what you're saying pretty clearly."
] |
[
"Could you explain the graph? I have no clue what those arrows mean :/"
] |
[
"Does a black hole have a definite mass?"
] |
[
false
] |
Also, does it have a shape?
|
[
"Yes, for example the black hole at the center of the milky way has a mass of roughly 4.1 million solar masses.",
"More difficult to answer, black holes have an event horizon, that is the limit from which no light or information can escape. In a sense, the event horizon is the border of the black hole. The event horizon is almost spherical (exactly spherical if the black hole is not rotating). Inside the black hole, however, there is a gravitational singularity (for obvious reasons there is no experimental evidence for anything inside the black hole). In another sense, this singularity could be viewed as the black hole. This singularity is either point shaped (non rotating black hole) or ring shaped (rotating black hole).",
"http://en.wikipedia.org/wiki/Black_hole"
] |
[
"A black hole has 3 measurable properties: mass, charge, and angular momentum. See ",
"the No-hair theorem",
".",
"If we think of the ",
"Event Horizon",
" as the boundary of a black hole, it is spherical for a non-rotating (no angular momentum) black hole and slightly oblate for a rotating black hole. The size of the event horizon is determined by the mass of the black hole."
] |
[
"This depends on how the black hole formed and what it ate after forming. Since there is conservation of momentum (angular momentum included) it would have spin roughly comparable to the star it formed from and then we can continue to extrapolate that anything that was captured and falls into the event horizon also may effect the spin but I think most people assume changes after birth are relatively minute compared to initial conditions.",
"Then again we are just now playing with the concepts of colliding blackholes which may do some fun stuff with spin."
] |
[
"When undersea mammals are born, is it a rave for them to surface to breathe?"
] |
[
false
] |
I'm in the shower and wondering if dolphins and whales are born deep enough under water they will suffocate from lack of oxygen. EDIT: Race, not rave. Don't think things get that crazy for fish. Mobile won't let me update the title. Sorry. EDIT 2: Hey everyone, this is getting big by my standards and I'm very happy with the wait it's going, the rave scene, the raping of fish, the numerous other questions being answered. Love it all. Im off to work and my phone is trippin out along with Reddit. I will try looking back and being a part of the comments, however I'll be building an engine so hands will be dirty. Someone asked me if my phone was waterproof, it is, but I have a non waterproof massive battery pack attatched on it making it into a bomb in the shower. Trying to be reincarnated as a dolphin to rape some fish.
|
[
"Pretty much, yes.",
"Like other live-birth animals, they are provided oxygenated blood while in the womb, but after birth, they need to start breathing, and baby whales (for example) cannot easily float or swim. The mother will lift the baby out of the water to take its first breath. If the baby is born too deep, or in rough waters, or if another whale is unable or unwilling to lift it, then they can/will drown before they get to the surface.",
"Sort of a source: ",
"http://www.dailymail.co.uk/news/article-1201860/First-breaths-newborn-whale-calf-captured-camera-Australian-coast.html"
] |
[
"I wonder if all the \"dolphin saves so and so\" stories are the case of a dolphin thinking \"that poor baby\" and helping out even when its a 37 year old man"
] |
[
"Yes. Dolphins instinctually save other mammals in distress, not just babies, but humans, dogs, and even other primates. This is because it is in their nature to help animals in distress (kind of like we do if we see a dog stuck in a river). ",
"EDIT: basically dolphins are good people. "
] |
[
"How discrete are the energy levels that electrons can occupy? If a photon of wavelength 800 nm was required to promote an electron, would a photon of 800.00001 nm suffice?"
] |
[
false
] |
Assuming that the electron is originally at ground state. I know that electrons can only exist in discrete energy levels, but what is the margin of error for the energy of a photon that an electron can absorb to be promoted?
|
[
"A similar question was ",
"recently asked",
". The answer is that states with finite lifetime do not have an infinitely precise energy. They have some width inversely proportional to the lifetime of the state."
] |
[
"Definitely not random. There are multiple ingredients that go into it, including the matrix element for the possible transition(s), the coupling constant(s) for the force(s) involved, some kinematic/phase space factors, etc."
] |
[
"Ok thanks! Are there any factors that determine the lifetime of states? Or is this spontaneous/random?"
] |
[
"G-force and Water"
] |
[
false
] |
If I was in one of those G-force simulators, and it was also filled with water (and obviously had an air supply), would I be able to withstand a much higher G-force than without the water? I would think that as I'm nearly the same density as water then the force I would feel would be negligible until very high G-forces.
|
[
"Buoyancy can offset the effects of G-force to an extent. The problem is that your body is not of uniform density. If you were of uniform density then yes, you could tolerate huge G-Forces when in a fluid of equal density.",
"As it is, the varying densities within your body lead to sheer forces.",
"As a non-medic - I believe detached retinas are common result of high forces even though the retina is in a fluid medium.",
"Even so - using buoyancy to withstand high acceleration is plausible if not frequently practical."
] |
[
"I understand your reasoning that the water will lower the pressure on the body by a larger surface area but the overall force will be the same, in your original comment you seemed to imply the bouyancy \"cancelled out\" the G-force making it possible to withstand any G-force you wanted."
] |
[
"From your wiki link, \"The accelerations that are not produced by gravity are termed proper accelerations, and it is only these that are measured in g-force units.\" ",
"I was not saying the acceleration is nullified by buoyancy I thought that you were implying that in the first comment."
] |
[
"How does data transmit through the air/WiFi?"
] |
[
false
] |
Moving through a wired system makes sense to me, but I never quite understood how that same action can happen in the air of my home. Feel free to go in depth. I understand quite a bit about telecommunications and computing. This is something I never personally researched, just "accepted." Also, do technologies like GPS and mobile networks (4G) work similarly? Or do they rely more on radio/etc frequencies?
|
[
"A quick brief on computer networking layers. Layer 1 (is the physical layer) is the lowest level and describes how it's physically possible to encode a sequence of 0s and 1s over a particular medium. Layer 2 (the link layer) assumes that you already have the physical layer sorted out and describes how you can reliably send information from one device to another device over a particular medium. On top of layer 2 are further layers describing how to route information between networks (layer 3) and how to get reliable transit that compensates for congestion and dropped packets and things (layer 4) and so on.",
"What you're asking about are the bottom two layers, layer 1 and layer 2.",
"Are you asking about layer 1? If you're just asking how it's possible to wirelessly transmit information from one device to another device, it's the same principle as radio (really the same principle since wireless communication was first invented in the 19th century). Every WiFi device (be it an access point or a laptop) is just a low-powered radio transceiver. Specifically, modern WiFi encodes binary data by using phase modulation (different symbols are encoded with discrete phase shifts). If it helps you visualize what's going on, you can pretend WiFi encodes binary data using frequency modulation instead (similar to FM radio, but with discrete frequency shifts) because that was a modulation scheme in the very first 802.11 standards.",
"Or are you asking about layer 2? Layer 2 deals with how WiFi devices ",
" their packets. With potentially thousands of devices all trying to communicate over the same medium, they need protocols to detect when they're interfering with other devices, when to back off, when to repeat, etc."
] |
[
"What allows the data to move to the correct point B? -- what prevents my desktop data from interfering with my phone's data?",
"Every request you make is made up of little packets of data. The router sends out a bunch of little packets and your computer pieces them all together. But how does the data know which computer to go it?",
"Every network enabled device has a unique ",
"MAC address",
". For each packet of data sent out, the packet says \"this is for the device with this MAC address!\" and the device with that address picks it up. As WiFi is a radio signal that all within hearing distance can pick up, all devices hear it and they discard packets not meant for them. Hackers can eavesdrop on this data and that is why it's important to have encrypted WiFi."
] |
[
"Thank you. This answer is very thorough. In regards to level 2, we have 4-6 devices connected to WiFi most times. Say they are all on N networks at 2.4 GHz. What allows the data to move to the correct point B? -- what prevents my desktop data from interfering with my phone's data?",
"Besides Wikipedia, what's a good resource to learn more about these things? A text/book, website, MOOC?"
] |
[
"Assuming a virtually lossless fiber optic cable, is there an upper limit to the amount of light (intensity) it can carry? If so, is it dependent on diameter?"
] |
[
false
] |
I'm toying with the idea of installing fiber optic lighting in my living room to pipe sunlight from outside to illuminate the room during the day, and I started wondering about how many fibers I would need. This in turn made me ponder how much light I could fit through a single fiber, and how well that would work.... I'd probably melt anything I could afford to buy, and I doubt I could achieve the necessary focusing, but I started thinking about theoretical maximums...
|
[
"I decided to do a quick google search, and apparently there is a limit in distance at least for sending information based on the dispersion of the signal, which is a problem in all waveguides I believe.",
"http://en.wikipedia.org/wiki/Multimode_distortion",
"You are asking about something else, but I thought it was interesting."
] |
[
"Indeed! I appreciate it. Have an upvote and an orangered."
] |
[
"If it's actually lossless and not just virtually lossless, then there is no upper limit. Such a thing doesn't exist of course, so there is a damage threshold. For continuous-wave input into large-area (multimode fibers with diameters >100 micrometer) silicon fibers, you can go to tens of Watt without causing damage."
] |
[
"What is the relationship between ORP (Reduction Potential) and the concentration of CL in a saltwater pool? We are pool ops in need of guidance!"
] |
[
false
] |
I am a pool manager and operation at health club with three warm saltwater pools and a saltwater spa. The other pool ops and I are constantly struggling with the correlation between the ORP probe readings on our controllers in the pump room and the hand readings we get from using reagents to test water samples. According to our director, when the ORP rises, the level of Free Chlorine in the pool. Having worked here for almost a year, I know this to be true 90% of the time. No one, however, has done any justice to explaining the relationship between ORP and Free CL. All I understand is that the measurement of the reduction potential has some sort of correlation to the production of new CL (ex: if the controllers read an ORP below our set point in one of the pools, the controller will call for chlorine production and the ORP rises). The situation gets particularly confusing when we use sodium thiosulfate to reduce the concentration of CL in the pools. More often than not, the ORP probe will cotinue to read corresponding to high free CL, even while the thio is neutralizing CL in the pool itself. Any brief explanations of the relationship between ORP and Free CL would help. Also, any previous experience with salt systems like this would be awesome to hear about. Thanks reddit!!
|
[
"The explanation lies in electrochemistry. Free Chlorine in a pool is dissolved bimolecular chlorine gas that is produced by the redox reaction of hypochlorite ion with chloride ion (as in Bleach). This FCL is very oxidizing; it sanitizes the pool by oxidizing organic species (like bacteria) to chlorocarbon compounds, which are commonly known as combined chlorine. An ORF device is just a potentiometer; it contains a Ag/AgCl half-cell. The device looks at the voltage that is produced between the Cl2 half-cell (which is just your pool) and the Ag/AgCl half-cell. By the Nernst equation, this half cell voltage is proportional (logarithmically) to the concentrations of Cl2(g) in your pool. Hence, by taking the voltage reading, which is generally around 800-1000 mV, we can use the Nernst equation to find Cl2(g) concentrations in the pool."
] |
[
"So, one further question. I'll be checking out the Nernst later today, but in the meantime, what about false readings when neutralizing free CL with sodium thiosulfate in salt water? Would the ORP probe continue to provide a reading that corresponds to high CL even after thiosulfate has been added because of its sodium component?"
] |
[
"I wasn't quite sure about this effect, but I will guess (so don't take my word for it). I know that thiosulfate is a reducing agent that reacts with bimolecular chlorine gas to give chloride anion and either tetrathionate or sulfate anions. It may be that local levels of Cl2(g) close to the ORP probe are unaffected for some time. You will probably need to mix and wait for some time to see results. "
] |
[
"Could one make a vaccine to train one's immune system to attack their own body?"
] |
[
false
] |
As opposed to markers of some virus or whatever. Have there been incidents of people getting an autoimmune disease from vaccination trials? (obligatory: this is unrelated to covid, though perhaps the soreness from the booster is encouraging this on my mind. Very pro-vaccine, I am just curious if such a thing is possible)
|
[
"The immune system has a built in mechanism that destroys cells that recognize self-antigen. This doesn't always work (see: autoimmune diseases), but most of the time it does.",
"In some conditions like Gullain-Barre Syndrome, something foreign (like a vaccine or a bacteria in undercooked turkey) can stimulate a confused immune system to attack self antigens. When people have GBS after a vaccine (which is rare but does happen) this is essentially what happens."
] |
[
"Yes, in fact these are used to combat various forms of cancer.",
"References are so thick you'll have to sort through them yourself:",
"https://pubmed.ncbi.nlm.nih.gov/?term=cancer%20vaccine&filter=pubt.review"
] |
[
"Feel like it's important to emphasize that GBS tends to be way worse with wild flu than with the vaccine"
] |
[
"How close did we estimate the gravity of the Moon and Mars before we sent probes there?"
] |
[
false
] |
When we got there, we could simply compare the weight of the probes there with their weights back on earth. But how accurately did we estimate their gravities before that physical evidence?
|
[
"Most mass estimates come from things orbiting that object. Mars has two moons, observe their distance and orbital period and you can get a very good estimate for their mass. Same for all the outer planets.",
"The Moon doesn't have any natural object orbiting it but its gravitational force on Earth is strong enough to be notable, so you can get a mass estimate from that.",
"Venus and Mercury are more difficult.",
"In the era of radar astronomy, where you can measure distances between planets with meter precision, you can also study the gravitational forces between the planets and the gravitational force of the planets on the Sun (making it move relative to the center of mass of the Solar System) - but that is a more modern development."
] |
[
"You can't get the mass of a body from its orbit, only the mass of the body it's orbiting."
] |
[
"You can't get the mass of a body from its orbit, only the mass of the body it's orbiting."
] |
[
"If helicopter propellors spin smoothly, why do they make percussive \"buh buh buh\" sounds instead of a more constant hum?"
] |
[
false
] | null |
[
"\"Rotor flap\" is the correct answer, but it's more complicated than that.",
"There are two main controls in a helicopter - cyclic pitch and collective pitch.",
"Cyclic pitch alters the blade's angle of attack depending on where the blade is in rotation. This is controlled by the joystick, and it's what controls tilt/roll in the helicopter - how it moves side to side or front to back.",
"Collective pitch alters the pitch over the entire rotor disk, and it's what controls the altitude and velocity. This is controlled by the collective pitch stick usually to the left of the pilot. Pull up on that stick and the entire rotor changes pitch, increasing lift, causing the helicopter to go up.",
"Combine inputs to both sticks by pushing forward on the cyclic joystick, and pulling up on the collective - and with the right mix of inputs the helicopter pitches forward and accelerates forward. The rotor disk tilts and \"pulls\" the helicopter forward kind of like an airplane propeller, but at the same time it's providing the lift to keep the helicopter up in the air.",
"When a helicopter rotor isn't under load, and the cyclic and collective blade pitches are neutral - the rotor simply hums and doesn't make that distinctive chopping sound.",
"The sound also depends on the rotor type and blade count. High performance helicopters often have four, five or more blades in the rotor, spin at higher RPMs and unless under severe load - they produce less of that distinctive chopping sound because they need less pitch to do the same lift/work.",
"Propellers on airplanes make the same sound but at higher frequencies since they have higher RPM, but smaller rotors."
] |
[
"The sound is created from the previous blade creating a vortex in the air as it spins, then the next blade hits this vortex creating the \"buh\" sound.",
"The reason why it's not humming is because they blades aren't spinning fast enough."
] |
[
"The tiniest bit I ever thought I knew about helicopters... just got put into perspective."
] |
[
"HIV mutation, why doesn't it mutate itself out of virulence?"
] |
[
false
] |
It is my understanding that retroviruses in general mutate very rapidly because they don't have the normal mechanisms for checking for errors in transcription (possibly wrong term, hope you get the point). What I would like to know is why if they mutate so quickly do they not mutate themselves into a form that is no longer a threat to human health. Specifically HIV. Is this because each time it replicates in a cell it produces so many copies that -some- are likely to still be active? How exactly does this work? Thanks in advance.
|
[
"Actually, there are a number of strains that are less deadly. HIV-1 and HIV-2 are fairly different, with HIV-1 being far more deadly and more infections. Among HIV-2 infections, you can split them down into groups that are labelled, I think, A through P. Some of these are known for causing specific problems, while others are known for being less likely to cause problems. I'm pulling most of this from memory, so I might be a teeny bit off.",
"Given enough time and enough hosts, HIV would probably mutate into a form that wasn't very deadly at all. Killing the host isn't a very effective means of survival, so most of the deadliest strains have killed themselves off."
] |
[
"Don't feel dumb, it's not common knowledge. In reality, most scientists don't even consider viruses alive. All that's really happening is a series of organized chemical reactions that result in more viruses. The only function a virus has is injecting genetic material into cell. There is literally nothing else that a virus is capable of doing"
] |
[
"There's nothing stopping it from happening, but many viruses replicate by a few steps",
"So the idea of a virus becoming non-virulecent is not impossible, but once it mutated, it would never reproduce. The mutation would never become sustainable."
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.