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how did people in places like florida get ice before machines were made to make ice.
[ "Ice was harvested in cold climates such as New England during the winter time and stored in cold places such as caves, while being packed in insulation, such as saw dust. Ice could be stored year round in some locations.\n\nIce was then transported to warmer locations, such as Florida in ships, again using sawdust as insulation. Transit losses (ice melting) was very high.", "They had it shipped down from colder parts of the country, where it was gathered from the surface of lakes in the winter and stored in warehouses where it was packed in sawdust to insulate it so that it wouldn't melt as fast.", "Lake Michigan was the ice hun of north america. Upper class people had ice boxes. A deliveryman would deliver a block of ice and store it in your fridge and that's what kept your food cold." ]
Why do strobe lights cause seizures for certain people?
[ "The bright, flashing lights irritate the nerves of some people to the point of overexcitement, causing those nerves to send continuous signals to the brain. The brain can’t process it adequately, so it, in essence, shuts down and reboots." ]
Rainbow like waves on cellphone screens while using sunglasses
[ "ah so this is probably more suited to r/askscience, but I'll take my best guess as a former optical physicist.\n\nYour sunglasses have polarized lenses, which means only light that waves a certain way can get through them. But your screen also refreshes a certain way, so at certain angles, this refreshing could be visible through your sunglasses because the light will wave along those refresh lines. The lines are colored because there's three or four LEDs in every pixel so the screen displays (most) colors, but they might, again, refresh at different rates.\n\nand that's my best guess." ]
How do babies in the womb not get the negative affects of blood rushing to their head while being upside down for so long?
[ "Imagine being upside down in a pool. Not quite the same blood rush to the head, is it? A fetus is basically in a fluid filled sac.", "Babies don't have nearly as large a blood volume or distance between their head and the rest of their body, so the difference in pressure is much less compared with an adult human.", "Unborn babies are completely immersed in fluid. The lowest part of their bodies will have higher pressure but this will be exactly offset because the lower fluid will be at a correspondingly higher pressure too. Adults are used to having their legs at high pressure and their heads at lower pressure and it feels weird when you stand on your head to reverse the situation. Being immersed in water removes the effect because deeper water is at higher pressure.\n\nAnother point is that babies are simply much smaller, so the pressure difference is also much smaller.", "Babies are in a pressurized system and are usually pretty small while having their relatively gigantic mom’s plumbing. This makes the effect of gravity on their circulatory system pretty insignificant i would think", "They are usually only upside down for the last little while right before they catch the B train to V town." ]
glass slag and how it’s formed
[ "i'm assuming you're talking about slag glass because that's what google turned up (let me know if this isn't the case). Slag is a general term for impurities that come out of metal when it melts. Originally, slag glass was a glassy impurity (aka slag) that comes from smelting iron from raw ore. when you melt metals, various impurities separate out from the metal and are siphoned off. Later, slag glass stopped being made from ore run off and was made using multiple colors of glass to get the same effect." ]
How does electricity work?
[ "If you put all your Hot Wheels in a row on the coffee table or counter so they got from edge to edge, and then get just one more and push it in line so that it ends on the countertop/table, it'll push the one on the other end off. \n\nThat's how electricity moves. Metal is made of atoms, and atoms have electrons. The outside electrons in the atoms (called \"valence\") are the hot wheels lined up on your table. The outlet siupplies one more electron into the chain of atoms in the power cord, and out the other end falls an electron to be used by whatever work needs to be done.", "This is so dang broad, so I'll give you a real overview and you can ask for details. Electrons sit at the outer edge of atoms, and with sufficient force, they can jump between atoms. Conductors, such as copper, allow this with minimal force. Insulators, like runner, require a lot of force to do this. This force comes from the electrons around them - mainly on one side of them - repelling them since they are all negatively charged and like-charges repel. This leads to all of the electrons in a wire or other conductor having similar pressures, and not moving much until the wire is connected to something else that has lower electron pressures. These pressures are measured by voltage. Now, we can push on the electrons in one end of a wire, raising the pressure of the whole wire, and then extract that pressure from the other end of the wire. When this happens, the electrons flow from the high pressure to low pressure zones. This movement is current, measured in amps. The movement is impeded by obstructions, such as resistors, which slow the flow from high to low pressures. This is measured in ohms. This combination of movement and pressure is the total power moving in a system, and is measured in watts. This can be exploited in hundreds of different ways to do useful things for humanity. If you have any specific systems you want to know about, ask away!", "So electrons move easily in wires, and the electric field (from the battery) makes them want to flow from negative to positive. For them, doing that brings them to a lower potential, and the field exerts a force on them to do it anyways. From the collective action of difficult to comprehend numbers (think \\~10^(15) carriers/cm^(3)) of these electrons, you get a net current flow in the wire. The battery works because you effectively chemically separate negative and positive charges so that the only way to neutralize is to send charges through the circuit.\n\nOr, if you prefer (or were in my semi-conductor physics class), electricity is magic, and letting the magic smoke out of your semiconductors/resistors/diodes will cause the magic to stop flowing.\n\nEither way, I'm not going to pretend I understand everything (or much of anything) about electricity, but I passed 3 undergrad and one PhD courses about it, so I might have a leg to stand on." ]
Why can some plants live in water, but the same plant will die if it gets too much water?
[ "Plants use water to transport nutrients to the plant cells.\n\nThey evolved to do that optimally in the environment they exist.\n\nWhen subjected to other conditions it impairs their ability to function properly.", "Plant roots need three things: water, oxygen, and nutrients. Water and nutrients are fairly obvious, but plant cells use oxygen too...plants basically make food, store it, and then burn it for their own uses, while animals just do the burning part. Burning food for energy uses oxygen. Roots obviously aren't photosynthesizing because they don't get light, so they aren't making their own oxygen. \n\nSo, basically, roots need oxygen. Now, in a straight up glass of water they can get oxygen. Oxygen diffuses in the water at the open top of the glass, then circulates/diffuses downward to the roots. Because the water is open and pure, the oxygen gets to the roots, the roots stay happy and the plant stays happy (in aquaponics they often bubble air to the plant roots just to make sure they stay oxygenated). \n\nOk, but what happens if you overwater a plant in dirt? Well, the dirt turns to mud. Oxygen can't penetrate through the mud, because all the dirt particles keep water with fresh oxygen from circulating freely. And bacteria (and the roots) in the mud use up the oxygen that is present quickly. So the roots can't get oxygen and die. So does the plant, often.\n\nPlants adapted to living in marshy, muddy conditions have roots that can pipe oxygen down to where it's needed.", "Imagine you living in Africa at 50°C or at Arctic at -20°C. For you without clothes it would be very hard. But if you have several generation slowly accomodating and mutating, it will not be a big deal as if you suddenly move there and live there without clothes. Your skin would be darker in Africa, or you will grow hair everywhere in arctic." ]
How does the moon control the ocean waves?
[ "The moon does nothing to the waves themselves. Those are created by the wind. But it does change overall water levels through tides.\n\nGravity is stronger the closer you are to the source. Let's break this problem into three parts to simplify it.\n\n The surface of the Earth directly under the moon is closer that the middle. And this region is closer than the side opposite the moon. \n\nSo closest side feels strongest gravity, middle a middle amount, and the far side the weakest.\n\nWater is about to move, so it's going to pool up where it's tugged the most, underneath the moon.\n\nThe Earth gets tugged towards the moon too, which \"leaves behind\" water on the far side, which seems to sell and rise away from the surface.\n\nSo we get two bulges, one on the bear side, one in the far side. The Earth is also spinning, which changes what land masses are on the high and low zones as the day goes on.\n\nThe sun also creates tides, but smaller ones. When the sun and Moon line up we get stronger than usual \"spring\" tides, and when they are a at right angles we get weaker than normal \"neap\" tides. These happen monthly as the moon permits the Earth.", "Gravitational pull. When the moon lines up with the earth at a certain orientation it causes spring tides and neap tides. Neap tides occur twice a month and are your regular tides aka high and low tides. Spring tides occur only during a full moon or new moon \n\nSomeone smarter and with more time can elaborate. Or tell me I’m wrong" ]
Can you sweat underwater? Why?
[ "Sweating is your body’s way of cooling itself off. You body secrets swear which evaporates and Takes gets along in the process which cools you. You wouldn’t have any need of sweating underwater (or while wet) as the water itself would do the same job. \n\nBut you still sweat if you get hot enough. It’s an automatic process the body performs so if your body gets to the sweating threshold, you will sweat regardless of being in water or out. You just won’t notice it if you are in the water." ]
Is space infinite?
[ "There really isn’t a good answer to this without some speculation being involved. The universe as we know it is constantly expanding from what we believe is an event known as the “Big Bang”, which unleashed an incredible amount of energy and mass. To observe what’s beyond the universe you would need to move very fast for much longer than the average human lifespan. \n\n\nModern science estimates the speed of expansion or Hubble constant to be about 71.9 kilometers (44.7 miles) per second per megaparsec (one megaparsec equals about 3.3 million light-years). Assuming you could move faster than the expansion, and you lived long enough to reach the “edge”, you might find another universe or absolute nothingness. For all we know you’d find a tentacle monster that would fall in love with the human species if you’re a fan of Futurama.", "According to our current models and measurements, the universe is \"flat\". This means it stretches out to infinity in all directions and contains an infinite amount of matter. And it's *expanding*, in the sense that the scale/metric of space is constantly increasing (larger distances between objects). There is no boundary or edge. It never ends.\n\nThis means that the universe has always been infinitely large from the moment of the Big Bang. It's a bit of a misconception that the entire universe was once \"smaller than an atom\" (or along those lines), because that suggests the universe was somehow curved/closed in the past and had a measurable volume, and then later became flat & infinite. Which isn't correct. As far as we know, the universe was infinitely large from the moment of the Big Bang, and therefore Big Bang happened *everywhere*. \n\nHow is that even possible, you ask? How can infinity just manifest like that? Well we don't know, because our entire understanding of physics (matter, energy, space, time, etc) starts turning into gibberish as we get closer to the hypothetical moment of the Big Bang (T=0). The equations start spitting out nonsense and thus we call it a \"singularity\" - which is just a fancy way of saying \"???\".", "What we know for sure is that space is bigger than it was before, and it keeps getting bigger. Which *implies* that it was smaller at some point, and that it does have some quantifiable boundary. However since it's getting bigger at a rate faster than light, it might as well be infinite for us, because (with our current understanding of physics) we'll never be able to observe its \"edge\". The universe will simply grow apart too fast and at massive scales, until things are too far apart to even interact. That's one very credible theory, anyway.", "practically speaking, it doesn't really matter. \nSpace is big. Bigger than we will ever ever be able to document and explore it all. And it's expanding pretty fast. \n\n\nSo the question is a bit like asking is the internet infinite? \nOf course it isn't but also it'd be impossible to comprehend all the data that already exists and a lot of new data is made every second. So yes practically it is infinite." ]
How was triceratops mouth/beak optimized for eating enough jungle plants/grass to sustain its body weight?
[ "A combination of being exothermic (what they used to call cold-blooded) and just constantly eating.\n\nThere's not much specialized about their mouths/teeth except thst they can cut the plants and start digesting them quickly." ]
Vis a vis abortion, why is it so hard for doctors and biologists to pin down "where life begins?"
[ "This is an area where science/technology, religion and philosophy all have something to say. Therefore interpretations and definitions are contextual. \n\nIn certain respects, advances in scientific knowledge has made the issue even less clear. Science doesn't advance in a consistent way in all areas. In today's situation, there are more methods to keep a body functioning even with severe damage to many organs. However, science hasn't made much progress in defining consciousness or sentience in other than mostly abstract terms. \n\nA philosophy professor once gave this scenario (probably common). Say you went to bed one day and woke up to find that someone had connected you (medically) to another person (an adult, say). Someone leaves you a message that this person is sick and will almost certainly immediately die if they are disconnected from you within the next 7-8 months but if left connected, they have a good chance of surviving. You, on the other hand, are compromised and also stand a low (but not zero) chance of death due to this connection. Are you obligated ethically to maintain this connection? Would you support a law saying that anyone in this position is criminally responsible if they decided to disconnect?", "There's not really a scientific definition of sentient life. A human embryo, like all other cells, is alive. But at what point does the spirit inhabit it? Islam says the spirit is there when the heart beats. Christianity is silent on the issue, I think. Anyone know what the other religions say?" ]
Why is moving air (eg. wind) colder than stationary air?
[ "Not an expert but from my understanding...\n\nYou is hot. \n\nYou warm the air near you. \n\nAir near you now warm.\n\nNew Air moves into that airs place. \n\nNew air was not previously exposed to your hotness so is cooler in comparison to old air." ]
Why did Korea split into two countries during the Korean War, but not the U.S during the Civil War?
[ "Because during civil war the side that was against splitting won. During the Korean war neither side won and the war technically never ended. There have been many skirmishes at the DMZ since the Korean 1953, notably [in 1976](_URL_0_) where American soldiers were chopping down a tree in the DMZ and the North Koreans Army killed 2 Army officers with axes.", "Because the US civil war was one by one side and that side decided to keep the country intact. \n\nKorea was under Japanese rules until the end of WW2. At that point, there was a power vaccum and the peninsula didn't really have a government. The United Nation made the decision to have the URSS administer the territory that was under Japanese control up to the 38th parallel, and the US administer the territory below the 38th parallel. This was basically like in Germany where you had different part of it administer by the Soviet Union, US, France and UK. This was to give a temporary government to the place, make sure the military was disarm, make sure the peace treaty was enforced and help the local population form a new government. Obsviously the South made a capitalist system like the US and the North made a communist system like the Soviet.\n\n & #x200B;\n\nThe North attacked the south to unify Korea, the US protect their ally South Korea, push back the North Korea up to chinese territory and North Korea was finish. But North Korea had two ally in the region the Soviet and Communist China. The Soviet didn't want to intervene directly since this could create a nuclear war, but China could intervene while keeping it a conventionnel war. China also didn't want to have a ally of the US right at their border so they smashed into the US forces close to their border. Why the US receive such a beating is debatable, but they were push back close to the initial border of the 38th parallel until they were able to solidify their defense and a stalemate remained until a ceasefire was declared. We are still in that ceasefire since technically speaking at still at war with each other, they never signed a peace treaty.", "Largely it came down to the threat of the other parties involved. In the US civil war, distance was still a considerable concern, so entities that sympathized with either size were not able to project their influence to a massive degree. Also, IIRC there were other concerns going on in Europe at the time, largely due to concern that siding with one side or the other would cause concerns of rebellions elsewhere. As a result, while there were instances of helping out via funds and like-minded things, there was never a major commitment.\n\nWith the Korean wars, you had large entities that were basically using Korea as a pissing match with each other. While there was a ton of territory captures, liberation, and recaptures, neither of those big forces wanted to 100% to total war with the other. The US and associated forces could have levied total power and dominated the peninsula, except for the fact that the very close in size powers that were fighting on the side of Korea had much easier supply and deployment lines due to proximity. It simply would have cost way to much, both financially and in lives to fully levy influence on the peninsula and take the whole area. It also would have spiraled into not just a war with Korea, but a war with the USSR and China as well. This probably would have then turned into a nuclear war once one side started losing, and both sides recognized this. As a result, both sides eventually decided it simply wasn't worth it to continue pressing their advantages, and the Demilitarized zone was established, splitting the nation into 2.", "Because they are still at war. If they ever finish the war the winner will either divide up the country how they see fit or unify it under their leadership", "Because in the American civil war, the north won and forced the south to remain a part of the union. \n\nKorea split after WWII, before the Korean war. In the Korean war, North Korea tried to conquer South Korea and unite the country under its rule, but lost.", "North Korea was helped and protected by the ussr, while the South Korea was helped and protected by the USA.\nSince no one won and they both wanted to be allies with their protector (NK-Ussr and SK-USA) they never reunited" ]
Why hasn't the US gone Chip and Pin even though the infrastructure is in place?
[ "In the US you aren't responsible for credit card fraud regardless of why that fraud occurs. This is not the same in the EU. EU laws on cardholder liability vary from country to country, but in most countries you are liable for ~150 euros per transaction, unless you acted \"carelessly\" in which case your liability is unlimited.\n\nThis is why chip and pin is widespread in the EU: it provides an easy mechanism for banks and credit card companies to shift the liability of fraud onto you because if the fraudster has your pin then you are deemed to have acted carelessly - and there are many cases in which a fraudster could get your pin despite you not acting carelessly, meaning that you get stuck with the fraudulent bill through no fault of your own.\n\nThe pin itself adds almost no security - it only protects you in the extremely rare case where the card is stolen and you don't report it until a purchase has been made using a chip reader. \n\nIn the US, the pin doesn't change the liability status of a fraud case - the card issuer is 100% liable regardless of how \"careless\" the cardholder was.\n\nThere are, however, costs in switching over to a pin system. The first of those are on the part of card issuers who have to get all of their existing customers to switch over to using a pin. Although it may not seem like it, convincing people to switch over to something like that is horrendously expensive in terms of the educational materials you have to send out and additional customer service calls you have to take from people who are confused about the new system.\n\nThe second cost is paid for by those merchants who are used to taking a customer's card and charging them at a single, stationary point of sale station - ie restaurants - who now need to purchase an entirely new point of sale system. This is, again, horrifically expensive and not something that merchants are inclined to do - getting them to even roll out chip readers in the first place was a multiyear process and there are many that haven't switched over.\n\nSo in the US you have a situation in which chip and sign is the established norm and switching to chip and pin offers no meaningful benefit to anyone but is expensive." ]
How do colds happen?
[ "The common cold is simply a virus, specifically one of over 200 different strains of viruses. They spread through the air or by direct contact. Most symptoms are simply the body's immune response to the cold. Despite the name, there's little evidence that it's actually caused by cold weather.", "The main reason is a viral infection. Specifically, a group of viruses called Rhinovirii. \n\nMultiple factors determine how easy it is to get infected, the major ones being :\n\n1. Cold dry air makes the epithelium of your nose, and throat (airways) inflamed and more susceptible to infection by reducing natural mucus production and dehydrating the mucus.\n\n2. Cold temperatures reduce the effectuvity of the humoral immune system to fight of any infections that do occur, including the resident immune cells in your airways. \n\n3. Cold temperatures may also increase the viability of stray virus particles in the environment. \n\nThis means that we are much more likely to get colds during the winter than summer. The fact that it is called a 'cold' is an invention of the Western world who have large differences between summer and winter temperatures. People living in tropical climates also get 'colds' and their languages do not call it a 'cold'.", "A cold is your body’s response to the cold virus which is ever changing. The fever, sneezing, mucus are all bodily reactions as it tries to find and rid of the virus." ]
why do mushrooms naturally grow in a circle shape?
[ "Many types of fungi feed of plant matter buried in the ground. They form a vast network of roots, the so called [mycelium](_URL_0_). This network grows underground, absorbing all the nutrients, at at some point they use the stored up nutrients to grow above ground to spread their spores with the wind. So if you see a bunch of mushrooms clustered together, those things are all just like tips of a giant iceberg growing beneath the ground. This network will grow outward as long as there are more nutrients to be found.\n\nThe reason that they form these circles is that the mycelium dies off once there are no more nutrients in the soil. So while it grows outward, it dies off in the center. If the conditions are just right, it'll form a nearly perfect circle in the process." ]
In movies and TV shows, when actors and actresses snort a substance (cocaine, heroin, etc.) what are they really snorting?
[ "It depends on what they're doing with the substance. If it's just going to sit on a table or get cut into lines, they use a mixture of corn starch and baby powder. If it's going up a nose, they'll use powdered lactose instead (or vitamin B powder if they're lactose intolerant), and they might coat the inside of the straw with Vaseline (because the powder will stick to it instead of actually going up their nose). They'll use slightly different mixtures and add different innocuous powders to get different colors if they need different drugs.", "The real thing. Why would anybody snort some sugar or starch when you can get high and act more realistically? Plus nobody is checking that." ]
How are polar bears able to go months without food?
[ "Animals that hibernate build up fat reserves in the summer and then go into a state where they minimize how much quickly they use that up by remaining inactive, slowing their metabolism and lowering their body temperature. It's not limited to polar bears, many other bears do and also animals like hedgehogs, tortoises, lots of flying insects, bats, mice, squirrels to name a few.\n\nPolar bears are an extreme case as food is virtually unobtainable in the winter months so they would probably use more energy than they gain by foraging. Some other animals rouse up at times when the weather warms, more like is dozing than full sleep." ]
What is a geometrically safe container to prevent radioactive materials to reach criticality? I've been reading a lot about nucular accidents and there is often this phrase of a "geometrically safe" container popping up. What is it and how does the geometry of a container prevent criticality?
[ "You get chain reactions with nuclear reactions because radioactive material decaying can cause other radioactive material nearby to decay to. \n\nIn nuclear reactors you want the reaction to be just enough to keep going and give of some heat, but not more. With bombs you want them to really get worse exponentially fast and give of as much energy as possible in a very short time.\n\nWhen transporting stuff you ideally don't want it to explode or even keep heating itself.\n\nOne way to do this is to keep the mass down.\n\nanother way to do is is to distribute the mass so that it won't allow a chain reaction.\n\nYou can have the same amount of material in the form of of a solid sphere or a thin rod. a sphere is ideal because everything is close together. If an atom decays it has the best chances of getting other nearby atoms to decay to. In the shape of thin rod you have the same amount of material but much of it is much farther away an atom decaying in a rod has far fewer neighbors that it can get decay too.\n\nThe idea is to ensure that as much radiation as possible is wasted hitting something other than the rest of the radioactive material.", "Fissile material requires a \"critical mass\" to cause a criticality. One of the methods to prevent this critical mass is to have containers that can't hold a critical amount. \n\nFor example (I'm using made up numbers for ease); imagine the critical mass is 1kg. To prevent this occurring you could make sure all storage containers can only hold less than 1kg. That is, you can't physically fit 1kg of material into the container (imagine trying to fit 1 litre of fluid into a 0.5 litre bottle, you physically can't do it).\n\nSimilarly, the containers could have thick walls, such that when stacked together the fissile material has 2 wall thicknesses of separation; this would also be considered when designing geometrically safe containers.", "Basically something that divides up the material up and keeps individual portions separate, far enough away from each other that particles coming from random nuclear decays don't hit enough other atoms often enough to produce a chain reaction\n\nFor instance, packing it into a box (or worse a sphere) gives maximum chance of particles hitting other atoms. Long thin rods with space between them gives a lesser likelihood of that." ]
How do different animals age differently? What is the difference in their physiology that makes them age live longer/shorter lives than us?
[ "Heart beat speed is a common factor, faster heart beat tends to equal shorter life expectancy while slower heart beats equal longer life expectancy. I read this once so take with a grain of salt.", "There is a max amount of times that each of your cells can replicate (without mutations like cancer) “programmed into your dna” this number varies for different species", "Going for heart rate. For at least of 80% animals, there is some kind of agreement that after 1 or 2 billons of beats you will die. Its very rough number but it works generally." ]
why is it better to pre-heat the oven when cooking meat?
[ "If you need to cook for a long time, then it doesn't matter.\n\nIf you need to cook for a short, set amount of time, then it matters because each oven takes a different time to heat up, so the recipe would be inconsistent between different ovens unless you preheat them.", "> wouldn't it be better to just put it in when the oven is cold so it cooks more evenly?\n\nThis is the opposite of what happens. Ovens are preheated to avoid food being cooked unevenly. Putting food in a cold oven will cook the outside more than the inside.\n\nThis can cause the outside to get burnt.\n\nIt will also mean the food will look cooked when the inside is still cool, and for meat this means chance of food poisoning.", "If you put the meat in while the oven is cold, you *must* expose the meat to the series of temperatures the oven takes on while it pre-heats. Maybe you're OK with this, but there might be a culinary reason why you would prefer to expose the meat only to the final temperature of the oven. \n\nFor lean-ish meats like rib roasts, poultry breasts, and loins, most chefs think that it's best to cook them to a safe temperature as fast as possible to avoid moisture loss. This means you want to start the meat at a high temperature immediately, so pre-heating the oven is a good idea. \n\nFor meats with more fat and connective tissue, like rumps, bellies, and legs, you need a lot of time (regardless of cooking temperature) to break down the collagen and other tough parts of the meat. Chefs would recommend cooking these cuts \"low and slow\", which could include putting them in a pre-heating oven. You might get better results if you braise the meat in a wet environment like a pot filled with stock rather than baking in a dry environment like an oven tray.", "What do the instructions say on the animal?" ]
Heat tends to rise above colder air, but what happens when there is no gravity?
[ "When there is no gravity, the hot air will simply mix with the cold air until they reach the same temperature.\n\nThe long answer:\n\nCold air is denser, meaning that in a given volume of say 1 litre, there is more of air that can fit into 1 litre if it is cold, then if it is hot. So 1 litre of cold air weighs more that 1 litre of hot air. Since weight is the force exerted on mass by gravity, 1 litre of cold air weighs more than 1 litre of hot air, and it sinks. This reveals the misnomer 'hot air rises'... Its more like cold air will sink in hot air because it weighs more than the same volume of hot air. If there is no gravity, there is no sinking, so the cold air and hot air will simply mix and reach thermal equilibrium.", "Wam air is less dense so it moves up. In zero gravity, the thermodynamics itself will have major influence over other factors.\n\nSo if you are in room with cold walls, air will stratificate with hottest air in center of room and will be gradually cooler the closer you are to the walls...\n\nIn other case when you have hot walls, cold air will be in center of the room." ]
why do moths wait until the sun is down to be active, yet seem to spend all their waking hours around lamps?
[ "they normally use the moon to navigate and these lights just confuse them. It's not like they \"like\" or need the light to live." ]
How can someone make a fraudulent transaction just by knowing my Debit Card Number and CVV?
[ "i didn't need any Pin or anything to add my credit card to amazon, they might get suspicious if the name on the adress is not the same, but that's easy to change.", "In the United States, you can run a credit card using just your credit card number and CCV. PINs are only used for ATM/debit transactions, not transactions that use the Visa/MasterCard networks.\n\nSome online stores or gas stations use zip code or address information as another verification, but it's usually pretty easy to look that up if you also get someone's name.", "In many cases, using a PIN or password is an optional security step that the merchant processing the card sets up (at additional cost to them). But it is not generally a requirement, and there are plenty of merchants who will process a payment without that level of security. A thief who obtains your card info only needs to know of one of those merchants to do some damage, especially with a debit card, and they likely know of many. When I ran a small business just a few years ago, card no. plus CVV was all I needed to run a transaction through my on site terminal. Our on line payments required a higher level of security, but not our \"card present\" transactions.\n\n/Edited for typos", "In the UK these could be used to process an insecure payment (higher transaction fee) on a card machine. if they had the number of the first line of the address and the postcode/zipcode that would be a secure payment.....this is how payments are taken over the phone at a takeaway" ]
How snorted substances affect the brain without properly being ingested or injected
[ "Chemicals dissolve in the mucus which coats most of the surface in the nose/back of throat. It can diffuse through the cells and enter your bloodstream directly. Same thing when you put something under your tongue, like lsd.", "Substances pass across mucous membranes lining all our insides. Crushed aspirin under the tongue is recommended for heart attack first aid. Lots of medicines can be taken as suppositories in the rectal cavity. It's also how swallowed medicines in the stomach get into the blood stream so quickly after all, you don't need to wait hours for digestion for a painkiller to take effect.\n\nLots can even travel through the skin. Ibuprofen cream for sore joints and nicotine patches for example. We are not as impermeable as you might imagine!" ]
Why do gunshots sound so different at distance?
[ "The bang at the gun is from the explosion of propellant. \n\nThe snap downrange is the shockwave from the bullet going faster than sound. This sound is drowned out by the bang when you're closer to the gun. \n\nThere is also a whizzing sound as the bullet destabilizes or ricochets and starts to tumble. This is caused by the rapid change in air pressure as the bullet goes from aerodynamic point first to sideways into the air and back." ]
How can our brains distinguish between men with high voices and women with low voices? (Eg. Charlie Day vs. Emma Stone)
[ "Even if the pitch between a higher pitched male voice and a lower pitched female voice is the same, a male voice sounds different due to differences in the vocal tract and the resulting acoustic resonance. This is called a formant.\n\nHowever, it’s more difficult distinguishing between the two when this quality of the voice is being masked by distortion, such as when hearing the person’s voice through a walkie talkie.", "Expectations. \n\nI am a female with low voice, and people tell me what a lovely professional and soothing “radio” or “spokesperson” voice I have when they talk with me face to face. \n\nIf they don’t see me, I get called “Sir”.\n\nI get it just as often in person as over the phone, as long as they don’t see me. I can’t tell you how many tired cashiers call me “Sir” while scanning my purchases in, only to finally look at me to pay and add “omg MA’AM I am SO SORRY!” \n\nIt doesn’t help that I’m 5’10” and have broad shoulders, so a quick impression from peripheral vision doesn’t disagree with the mental “male” label from my voice. Then they turn and hey, big hips and bust too, whoops. It’s happened to me all my life (I was a fairly androgynous geeky kid before the bustline developed), I’m not offended.\n\n*but dang I would love one of those professional voiceover jobs practically everyone tells me I should get" ]
what is the science behind a seizure, including how it ends?
[ "There are lots of things that can trigger seizures (genetics, electrolytes, infections, etc.), but the key thing to keep in mind (no pun intended) is that neurons work through the flow of electrolytes which creates an electric charge. This charge can be communicated from one neuron to the next through neurotransmitters.\n\nLet's say that something causes irritation to the brain (it doesn't matter what, but let's assume someone has a brain bleed). That area becomes really inflamed, and this causes the neurons around it to become overstimulated. It also makes neurotransmitters that are normally confined to a synapse leek out into the rest of the brain. Now, you have neurons that are way too stimulated and extra neurotransmitters floating around which causes the rest of the neurons to start firing as well.\n\nAt the same time that this is happening, the normal processes that that brain relies on to slow or stop neurons from firing become overwhelmed, so neurons are over firing and also unable to stop firing.\n\nThe shaking that some people have during a seizure is just a symptom of this uncontrolled brain activity. (Remember - the brain tells the rest of the body to move, so if it's firing erratically because of a seizure, it can manifest in convulsive type movements).\n\nPeople who have genetic epilepsy usually have an issue where the channels that electrolytes move through in neurons are either over- or under-active, which has the same effect as above.\n\nIf they're not stopped by medications, they'll usually burn out on their own. After firing, neurons have something called a refractory period where they aren't able to fire again because they have to get their electrolytes back to normal, so over time, seizures usually slow down and stop on their own.\n\nHope this helps.", "A seizure is essentially your neurons firing off way too much so your brain starts doing weird things like having your muscles spasm or cramp." ]
How are no-confidence votes in the UK different before and after the Fixed-Term Parliments Act of 2011?
[ "Previously:\n\n* The PM could ask the Queen to dissolve Parliament at any time and hold new elections\n* If the government lost any \"important\" vote (a confidence motion or supply bill), it was *expected* the PM would do that\n\nNow:\n\n* The PM can't ask the Queen to dissolve Parliament at any time\n* The government can lose any and all votes, it doesn't mean there has to be a new election, unless...\n* Parliament passes \"This House has no confidence in HMG\" (with a simple majority, e.g. 326-323, or even 1-0 if nobody wants to vote).... and Parliament does not pass \"This House *has* confidence in HMG\" within 14 days\n* Parliament passes \"There shall be an early election\" with at least 2/3rds of all Parliamentarians in favour (e.g. at least 433 votes in favour)\n\n\nJohn Major's government lost an important vote, so Major tabled a vote of *confidence* the next day, to get his own party to agree his government was doing the right thing. That vote passed. If it had not passed, the newspapers would be like \"oooh....\" and Parliamentarians would be like \"what next?\" and he'd be expected to request a new election. Now, nothing would happen, like when May failed to pass her meaningful vote on Brexit. But then when the Opposition got their turn, they could choose to put in an explicit Vote Of No Confidence (as Labour did), and if it passed (which it didn't in March, but who knows in the future) there'd have to be elections.", "Before the Act, a PM could call an election at any time (technically, they could advise the Queen to call an election). It was generally understood that a PM who had lost the confidence of the house would resign or call an election, but nothing formally required them to do so. There was no specific rule for what a no confidence vote was. A PM could choose to treat any important vote as a no-confidence motion, effectively saying that they'd call an election if they lost the vote.\n\nThe Fixed-term Parliaments Act removed that power from the PM. Elections now happen in one of three ways:\n\n- automatically five years after the last one,\n- if MPs pass the specific motion \"that this House has no confidence in Her Majesty’s Government\" and 14 days pass without another vote reversing that (either for the same PM after a change of policy, or for a new PM who can command the confidence of the house),\n- if two-thirds of MPs vote for the specific motion \"that there shall be an early parliamentary general election\".\n\nThe PM can no longer decide that losing a vote on a specific policy should cause an election." ]
How Do Military Operations Get Named?
[ "I think I read somewhere it's a random generator. After all, if you're job is to think of cool names about \"the death ray fired at the sun\" you as a human may inadvertently reveal details of the project subconsciously, like Operation Ray-Ban, Operation Icarus, Operation SPF3000, Operation Lantern Archon. Etc...\n\nA computer prefilled with wordlists (usually with heroic or patriotic, sfw words) won't accidentally slip. A newly designed plunger for toilets may be Project Ovation, where as the Deathstar is deemed \"Operation Velvet\" since the computer doesn't know the difference between death stars and plungers. And the exclusion of NSFW language prevents the exact scenario of \"Your son died serving his country in Operation Buttmunch for the Shitstain campaign\"", "> I'd name an offensive something like Operation Buttmunch.\n\nAre you going to be the person that tells the wife of the dead serviceman that they died during Operation Buttmunch or other similarly titled name?\n\nCodenames are code names, but there are decorum points to prevent the above happening.", "Half the time, they're just random bullshit that has no meaning at all - the point of a codename is to hide the details of what's actually happening (eg - Jade Helm, Neptune Spear). The other half of the time, they're chosen for PR purposes to make the mission sound righteous/patriotic/etc (eg - Desert Storm, Enduring Freedom)." ]
How do scientists estimate the age of a very old animal ?
[ "The shark you're thinking of was a [greenland shark](_URL_4_), and was part of a study that looked at almost 30 individuals ([Nielsen et al. 2016](_URL_6_)). These researchers took samples from the lenses of the sharks' eyes to estimate their ages by measuring the types and amounts of carbon. The reason for using this particular tissue is because eye lenses pretty much never change once an animal is born, and so while other tissues can get renewed, eye lenses are the same age as the animal itself. To ELY5, most carbon is not radioactive (carbon-12), but occasionally, though both natural and human causes, radioactive carbon-14 is made. The amount of carbon-14 in the atmosphere changes over time, but we can study historical levels by looking at various recent fossils, ice cores, etc. The authors of this particular study used two strategies to estimate age based on carbon 14. First, there is a very easily measurable signature of higher carbon 14 in the atmosphere as a result of human nuclear testing in the 1960s. This is known as the \"[bomb pulse](_URL_3_)\", and it makes it easy to tell if a shark was born before or after 1960 at least. Then, for sharks that were older than this (which was almost all of them), the researchers used an [established dataset of carbon-14 values](_URL_7_) to estimate what time frame was most likely for the sharks to have been born in. Additionally, it helps a lot that these sharks grow continuously throughout their lives, so it's easy to roughly guess the age of a shark based on its size. The sharks in their sample form a [pretty nice curve](_URL_1_) showing the relationship between size and age. Though it should be noted that there is a pretty huge range on the oldest estimates (392 +- 120 years).\n\nIn contrast, measuring the age of the clam you're thinking of (an [ocean quahog named \"Ming\"](_URL_8_)) was much easier. Some clams grow faster or slower depending on the time of year which leads to [growth rings](_URL_5_) in their shells just like a tree. Carbon dating was also used as a separate method to double check this, and similarly agreed on this age within a couple years ([source](_URL_2_)). As a side note, this particular clam was actually discovered as part of a larger study ([Butler et al. 2012](_URL_0_)) that was looking for signatures of environmental change in clam shells going back over 1,000 years.", "Inside living beings are some sort of radioactive material. And those things have something called half-life. If the half-life is, let's say 100 years, then every 100 years half of the radioactive material is gone. After the next 100 years, the half of the half is gone and so on. Scientist can then say, based on how many of the radioactive material is left, how old the animal is.", "With a clam they usually go by size relative to the temerature of the water they were found in,same with lobsters and fish,for example if they were found in cold water things obviously grow slower so they would estimate the age that way,for cats and dogs and other furry animals there are other clues (grey fur,bone density,tooth color and gum health)....hope this helps" ]
Why are children viewed as more of a financial burden than they used to?
[ "The expenses that have outpaced inflation the most are those that children require. Health care, housing, education. It can cost tens of thousands just to have a pregnancy and delivery.", "Kids don't help increase the family income like they did when farming was less automated. Both my parents hoed rows of cotton, corn, beans, etc as children. They fed the animals, and in the fall picked cotton. Even though he lived on a farm, dad also worked at a full-service gas station before he was a teenager up until he left for college. All his earnings went to help the family.", "Any household that had like 8 - 10 kids back in the 1900 - 1950 era would absolutely have a stay at home mom whose sole job was to take care of the 8 - 10 kids.\n\nAfter the women's rights movement and after WW2 we saw women enter the workforce at close to equal amounts as men.\n\nAfter a few decades the economy has become such that only like the top 8 - 10% of wage earners can afford to have their spouses be home makers. Which means for all the rest of us, both parents have to work, which means day care.\n\nFor my two kids, daycare was $25/day, times two kids, times 20 days per month or $1000 per month. Somebody making minimum wage makes $7.25 x 40 x 4 or $1160 per month.\n\nIn short, children are viewed as a financial burden because they absolutely are. And I've only used daycare as an example... That doesn't feed or clothe or house them, and even then, that's just keeping them alive... wait until I tell you about the ballet lessons that cost $800 x 4 classes per year. Oh... and we'd like our kids to be able to snowboard with us... lets tack on another 4 - 6 grand. Piano lessons? Gymnastics? Any other activity? More money.\n\nWe estimate we spend about 14K per year per kid. With two kids we spend about as much as the poverty line just raising halfway decent kids.", "I think it would come down to the cost of education being a lot higher. \n\nSo when your grandmother was growing up, anything more than a gradeschool or highschool efucation was absolutley not neccesary to be succesful. For example, my great grandfather grew up and got an 8th grade education, left home and started working at chrystlers. He retired at like 45-50 im pretty sure. Had enough cash to live very comfortably until he died at 89.\n\nToday there arent any jobs that you could get with an 8th grade education and ever retire.\n\nSo the quality of education is much higher and therefore so is the cost. \n\nI would also argue that the quality of life is much higher than before for a child. But i think its more education.", "A couple of factors... \n\nPay hasn’t kept up with productivity, requiring more 2-income households. But this means childcare, which costs more for more kids. When mother stayed home, going from 2 to 4 kids didn’t cost as much as adding 2 more daycare bills at $1000/mo. per kid.\n\nLifestyles were cheaper. Homes didn’t cost as much relative to income, there weren’t cable TV, Internet, cell phone bills. And kids didn’t have sports leagues, piano class, and all the other activities people are expected to enroll kids in today.\n\nMiddle class jobs without degrees. More workers could achieve middle class pay without taking on tons of student loan debt that had to be paid back from their salary, reducing discretionary income.\n\nChildren were often expected to work, meaning they provided income to family rather than just added to expenses.", "Cost of living has increased massively since your great grandmother's time but there hasn't been an equivalent increase in wages. From healthcare, daily amenities right down to education. To get advancement, you need investment, which will drive up costs for consumers.\nThe \"have to have\" stuff isn't really necessary, it's just a product of the age old mentality of \"he/she has that, so I need it too\".\nRaising a kid like it was back then is nigh on impossible because of how much everything has changed. We are essentially living in a different world. To try and do something like that, the only way you'd have a decent chance is to isolate yourself from all of society.", "Part of this is society as a whole has changed versus just the issue of kids. Examples of what I mean.. In the days of your grandparents it was common to have gardens and farm animals. It was ok to make kids work these. It was common for every piece of clothes to be maintained and to be passed down. It was ok for kids to not go to school. All of this is replaced today with store bought food, clothes, and kids having to be 100% presentable for school. Malnurishment was common before WWII and was a driver of making schools provide lunches and of required school attendance.\n\nSecondly we have health care. In America this is a massive expense. Family insurance (not single adult or single + spouse but actual family) is easily $1k+ per month. This plus out of pocket expenses are frequently 25-50% of a families expenses. This grows for every child nowadays. Add to that the time off needed for each child. Most workplaces barely give enough time off to take care of 1 child let alone 10. At 2-3 kids most families have a stay at home parent. \n\nIn general this has lead to having kids being almost luxuries if you can truly afford them. Elsewise each additional child is (while loved) more of a burden than a benefit. People now think about giving each child the best they can and this is harder with more children.", "Father of two boys, 4 y o and 9 m o. Children are not as expensive as you might think. Time is. We don't have any family close so we have to rely on childminders and babysitters if we want to be functional members of society. That's a lot of money, especially if you work at night. I'm sure that growing up costs will ramp up, between activities, gear, etc, but so far so good\n\nOn a different note: many parents spend way too much money thinking their children need expensive clothes, new toys too often and mindblowing (and expensive) experiences all the time; now I get that it makes them feel like good parents and it's their right to do so and raise their kids however they like.\n\nIn my experience kids are not adults and don't understand value like we do. Buying an expensive onesie to be worn a couple months and then outgrown is a bad investment. Shoes are different, as they contribute to posture and health, but I find that charity shops are a great way to dress your kids and buy their toys too. I won't be buying anything expensive for my kids until they understand the value of it or if I know it'll be useful and last the long run. \n\nSome parents are also lazy or protective of their pre - parenthood lifestyle and prefer to throw money at stuff to entertain their children rather than spend time with them and coach, teach and sometimes micro manage them. Example: you don't need an expensive tablet to entertain your kid into silence while you're trying to have lunch in an expensive restaurant. You need to understand that you're a parent and the modern world is not designed to be friendly to you or your children (I wish it was) so you can't have that posh lunch unless you can leave your child with somebody else. I know it's not ideal but that's where we are at", "You used to be able to work children. \n\nThey would either go to the factories or work the farm/family business, just like the adults did. Only the smallest of children and the wealthy did not work. This was true until 1938 in the US with the Fair Labor Standards Act. \n\nYou also have wage stagnation and monetary inflation. Wages, in particular minimum wage, has not kept up inflation and the increased expectation of standard of living in the US. That means that a larger percentage of your money goes to caring for children. In particular the medical costs of just giving birth at a hospital can cost tens of thousands of dollars.", "You should read the Laura Ingalls Wilder books about her childhood. \n\nBesides what everybody else has said about children working for their keep, they got a lot less stuff. \n\nOne Christmas the kids got an orange, a penny, and a tin cup.\n\nEven adjusted for inflation I think an Xbox One is probably more expensive today.\n\nYou saved a lot of money on medical care too. In one of the books a young boy is screwing around during harvest time and ends up kicking a hornets nest and being extremely badly stung. The family wraps him in wet blankets, lays him on the porch and went back to bringing in the harvest." ]
How do tower crane counterweights keep from falling out?
[ "In the image you have linked you can clearly see the retaining bolts coming out of the sides, this stops them slipping through." ]
Why are male children more likely to inherit or surpass the height of their parents over their female siblings?
[ "Oestrogen closes your growth plates at the ends of your bones, so when girls hit puberty they stop growing shortly afterwards. Boys, who produce much less oestrogen keep growing for much longer and so can reach their full growth potential", "It’s genetics. A good rule of thumb is a boy will grow to be the average of his parents heights plus 5 inches and a girl minus 5 inches" ]
If your brain can remember memories from a very long time ago out of nowhere, why is it so hard to trigger your brain to remember things from as recent as yesterday?
[ "Our brain remembers different things very differently, and we have many different types of memory. Explicit memory is one of the two types of long-term memory that allows us to remember things like life-events and facts. This type of memory is conscious which means that you have to make a conscious effort to remember things. Mundane things from yesterday are usually not worth the effort to consciously remember them, so you just forget them. \n\nYou can sometimes recall them by remembering less mundane things like where you were, and why, and using your logic to figure out the rest.\n\nI'm no neuropsychologist, but I don't think we know quite yet why our brain acts like this.", "We have many types of memory, and the ways in which we recall events can vary greatly depending on the type of event and how long ago it happened, but the best answer I can give to your answer is neural pathways. Memories are connected to other memories, and to cues, which trigger them. The more a memory is integrated, or the more cues are associated with it, the easier it is to recall.\nYour trip to Disney Land when you were 8 is probably much better integrated, and better connected in your brain than what you had for lunch 3 days ago. There's a LOT im missing here, but that's the general gist of it", "We remember emotional events much more intensely than regular events, and are much more likely to be stored as long term memories. You are more likely to remember the details of a family reunion than last week’s trip to the grocery because you were experiencing more emotion at the reunion.\n\nCertain stimuli (ie songs, scents, familiar objects) may be tied with certain emotions and trigger a memory of a specific event or time period “out of nowhere”." ]
Why do we only ever see one side of the moon?
[ "The Moon spins once every month or so.\n\nIt also orbits around the Earth once every month or so. \n\nThe two periods are the same because the Moon is tidally locked to Earth, meaning the Earth's gravity pulled on the Moon until it stopped rotating relative to Earth. \n\nBonus fact: the Moon is doing a similar thing to Earth and had already extended the length of an Earth day to maybe twice what it used to be, but because it's so much smaller it'll probably be launched into interplanetary space - by the same interacting - before an Earth day is the same length as a Moon day/orbit." ]
Is that spinning circle of leaves that spins around a few times technically a tornado? Why does it happen?
[ "The way air moves can create a 'vortex' (like water spins as it goes down a plughole) the leaves actually make the vortex seeable. Vortexes of wind happen pretty often.", "They are not tornados, they are vortexes. But tornados are a form of vortexes.\n\nImagine taking a round object and rolling it between your hands. It is very easy, right? That's because the surface of the roll does not have to slide across your hands, just like a wheel. It would be much easier than if your hands are just brushing up against one another.\n\nVortexes are a bit similar to that: Imagine two fans blowing in opposite direction, but past one another. There is friction between the two airstreams: One pulls air in one direction, the other in the other direction. If this happens fast enough, the air inbetween will start rolling, similar to the round object between your hands, although a lot more complex.\n\nOn the ground, this happens quite often if wind brushes up against solid objects. Usually, you won't notice because air is invisible - but with smoke or leaves in the wind, you can see it.\n\n[Here is an image of a car in a wind channel](_URL_0_). The smoke tells you how the air stream is moving: At the top, the air is moving smoothly, but at the rear you can see that it twists around. That is because at that location, the air moving past the car encounters air that is trapped behind the car, causing it to twist around. Car designers will always try to avoid this, since it increases drag." ]
Why does the key of a song playing on a set earphones change when the earphones are at some distance from the ears?
[ "Higher frequencies get dampened harder over the same distance. \nAdditionally, you can only hear sound thats at least a certain loudness. \nHeadphones are low-power speakers and if you increase the distance high frequencies seem do drop out because the fall under that threshold. \nThe last thing to disappear if you increase distance is bass.", "it doesnt change the frequency of anything but it would dampen the higher ones which might for some reason make you hear it differently? key is for sure going to be the same though", "Different frequencies are able to travel different distances before diminishing greatly. When far away from a venue, you usually hear the bass sounds louder than the higher ones. There are several reasons for, but it has to do with higher frequencies being worse at spreading out.\n\nWhen the earphones are away from you, not all of the sounds from the song get to you - and you will get something that sounds differently. Sometimes, it might cause you to perceive the piece in a different key than it is, because some of the notes that play a big harmonic role in the song are missing." ]
Why are some soldiers wearing pixelated camouflage?
[ "Under certain conditions the pixelated/digital camo does a better job at breaking up the lines/outline/silhouette of the soldier. \n\nThe point of camouflage is not only to match the background colour of the soldier's environment, but also to break up any easily identifiable lines. If camo was colour matched to the surroundings but still in big stripes, the soldier would still stand out pretty good (depending on lighting conditions etc.)\n\nOld camo schemes were big hand designed \"splotches\". Good, but smaller more random splotches break up the pattern of the soldier, load carrying vest, gun/ammo etc. better. The newer digital patterns are even better.", "_URL_0_ here you can see how good it can be", "So in the early 2000’s, the Marines began moving over from BDU’s (the old green/black woodland pattern) to something called MARPAT. MARPAT was a pixelated pattern designed to blend more easily into the background and to distinguish Marines from other services. It came in two colors, though the desert-tan version has seen more use than the green version you typically see in-garrison.\n\nLike other Marine uniforms, everyone loved it and wanted their own version. The different service chiefs put out a call from vendors to design something specific to each branch, and after several years of expensive designs and testing, they got their wish. The Army came out with the ACU pattern which was a sort of digital-grey pattern, the Air Force came out with ABU, and the Navy went with the Type I blue pattern uniform before dropping that and going to the NWU tan/green uniform.\n\nHere’s the problem that came with everyone coming up with their own service-specific digital pattern uniforms: it cost a lot of money, and they mostly sucked at what they were supposed to do. The Army and Air Force uniforms blended in with absolutely nothing, and would quickly fade to a light-grey after too much use out in the field. The Navy Type I uniform was great at blending in with the ocean....which is exactly what you don’t want to do if you get tossed overboard from a boat. Also, they had a tendency to be explosively flammable. \n\nSo after a decade and a half of these uniforms, the Army and Air Force are now consolidating into the OCP pattern, which is a chunky tan/green/black camouflage pattern similar to the original BDU’s, but cut like the Army ACUs, The Navy, as I mentioned, is going with the NWU, and the Marines are doing their own thing and sticking with MARPAT.\n\nTLDR: The Marines made a functional and cool uniform, service chiefs from other branches got jealous and made crappy knockoffs.", "The human eye and brain is very good at detecting the shape or silhouette of an object, the color and movement. Camo tries to break up the outline and color of what a human should look like.\n\nIf you look at a forest or a bush. The shadows of the leaves and the sunlight breaking through create small patches of light and dark, similar to the pixelated dots on a camo shirt.\n\nAnd from a distance have those pixels not all blend together into a gray outline _URL_2_\n\nCompared to _URL_2_\n\nBy seeing the outline, aiming is easier.", "It's counter-intuitive, but the pixelated camo is better at making you disappear against a background than the more \"organic\" patterns.", "[Uniform History](_URL_3_) \n\nThis guy has a great YouTube channel for Uniforms. And has a good video on Canadian CADPAT. Which started the usage.", "So why do people in the navy wear blue camo? What are they trying to blend into? The water if they fall overboard?", "In some part, it’s because the camo looks cool. Originally the USMC issued digital camouflage uniforms to Marines because they deemed it to be effective in theatre; however, the Army also adopted this pattern because a general ‘wanted to look cooler than the Marines’ to increase recruitment.\n\nBut it’s also much more effective in certain situations than traditional blobs. This is because, for whatever reason, the eye rounds the corners of the pattern when viewing at distance - but the real kicker is that it takes inspiration from the surrounding environment and makes the pattern appear as if it’s the same shape as that. This is in contrast to traditional blobs, which look the same most of the time as your brain doesn’t need to do any of the ‘rounding’. \n\nIn reality, this doesn’t mean a whole lot as skirmishes are fought at distances where pattern is completely negligible these days - but digitised patterns still routinely perform better than their non digitised counterparts, and look cooler, so they’re here to stay.", "It is based on light transmission from the target to the rifle/gun. In bright light the straight lines between the pixilated patches become \"squiggly\" and an optical illusion occurs making the target/image \"boil\" thereby making the target more difficult to hit precisely. On a windy day you can literally judge the velocity and direction of wind by the slant of the lines on the target. To test this you can take a high powered telescope and look through it to a target with different geometric figures on it. Each one will transmit to your eye with a different total image. I straight up boil is the most difficult to judge.", "It's all about breaking up your silhouette and making it difficult for the enemy to effectively shoot where they think you are or aren't. Since Urban Combat is more of a thing nowadays there's less \"natural edges\" like leaves, twigs, grass. A great example of this is ship camouflage, they don't use colors to blend into their background because there isn't really anything to \"blend\" into. What they do is use large shapes that intersect and have hard edges to make it so that it's harder to tell where the ship starts and where it ends. Pretty ingenious.", "Pixelated camo looks blurry no matter how close so when far off it breaks up the shape of the soldier so he's harder to spot. You have to find solid lines to see the movement . Old school camo had solid lines even though they were is splotchy shapes. So you could still spot the splotches moving easier than the new digital.", "Not a direct answer, as there are many good answers already, but more of a fun fact.\n\nA big part of camouflage is to break up your silhouette, as mentioned. \n\nMany outdoorsmen wear flannels for this reason. The stripes, checkers, etc. break up your silhouette surprisingly well, especially considering how many animals are color blind.", "Trafitional Camoflague relies on colours that blend in and/or break up the object with patterns.\n\nDigital camouflage uses pixelation, pixel patterns are mostly ignored by the human eye when unmoving.\n\nCombine them together and you have a colour that blends in, a pattern that is broken up and a pattern that blurs and is ignored.", "if you look closely you'll notice that there a multiple pixel sizes in the camp. This serves to break up the definition of the body shape at different levels of resolution. Think \"Big squares blend in with big leaves, small squares blend in with small leaves\" a little simplistic but it's how it works.", "Digital camo is better under most circumstances and breaks up lines better on the body and is more versatile in different climates than splotched camo" ]
Why are Performance Enhancing Drugs in baseball treated much more harshly than in other sports such as football and basketball?
[ "They’re not, all leagues suspend player for significant amounts of time for use of PEDs. Baseball may suspend more games, but that’s because they have much longer season.", "Basically, to appease public opinion.\n\nBaseball was (arguably still is) rampant with PEDs for a pretty major part of its history... and while this made the game quite exciting with amazing plays, HRs, and players blowing out records and statistics that seemed unachieveable to ever do, it was also pretty clear that these people were cheating. The HR races of Mark McGwire and Sammy Sosa, and then Bonds was an amazing time to watch baseball... but everyone knew what has happening and their records will always be looked at with suspicion.\n\nEven congress got involved to question baseball about the rampant PED usage in the game and what they were gonna do about it. People were not happy. People across all walks of life, wealth, and so on. People were cheating... we know they're cheating, you know they're cheating, fix this.\n\nBaseball took a quite heavy handed approach to win back the fans favor. Although the actual amount of games suspended (as a % of overall games) is roughly the same as the NFL (baseball suspends 50 games about 30% of a season, NFL does 4-games, 25% of the season, thats pretty close). But a 50 game suspension is still enormous.\n\nIn other sports, while PEDs are present, they've never effected the game in the way of baseball and mostly has been at most a minor issue and dealt with as such. Boxing/MMA, cycling (the obvious one), and some Olympic sports are much more concerned than many of the standard pro sports.", "Baseball is one of the only sports that would be ruined if everyone juiced. Fastballs are already approaching speeds that make hitting them decision-less and more about pure luck on the hitter’s part and nobody wants to see a game with 25 solo homeruns (well... no one would want to see that after a while). The entire infield being on PEDs would be arbitrary if every pitch was a strike or a homerun, but the defence in hockey or baseketball would offset the other team’s offence if everyone was taking steroids. Football might get pretty boring if 80yd field-goals were possible i guess....", "Rules set out by MLB Association versus NBA versus NFL versus NHL might have players conform and abide to a particularly stricter set of rules when dealing with PEDs like steroids." ]
How does most peoples limbs grow the same length and size?
[ "Do you mean relative to other people or their own limbs?\n\nThere's an average intelligence, physical size, hand size, limb size, etc for humans. Generally people approach this mean. \n\nFor individuals, limbs actually vary slightly in length and size. One will almost always be smaller or larger than the other just not noticeably so.\n\nI don't know enough about the biological processes involved so hopefully someone else tackles this and I learn something too." ]
How Hong Kong could leave China?
[ "Outside of some type of armed conflict, there is little reason to believe China would willingly give Hong Kong independence. There certainly remains a possibility that HK remains in a type of state within a state situation that it is now, past the date its supposed to, but even then, China does not seem interested in continuing that solution past the point it has to.\n\nAs a bit more history. When the British turned HK back over to the Chinese, the reason they did it wasn't that the lease was expiring. The Brits could not give two shits about that. China literally threatened to go to war with the UK over it. The UK wasn't interested in a war with China, so instead the UK negotiated a fairly reasonable to them gradual changeover of HK to Chinese rule. Since then, its been a complicated situation as the changes occur and China is being less than nice with regards to HK and its people's demands.\n\nAs of now, there seems to be no interest from the international community to get involved in the HK-China relationship, as that would be direct rebuff to China and everyone wants to keep peace with China to keep trading.", "War china will attack if they attempt to leave already stated they haven't ruled out forcing Taiwan to submit by force.", "> how can Hong Kong leave china?\n\nSame way the US left the Britain; armed revolution.\n\n > But what about the world? Of course, there are some nations like the USA or the U.K that will stand up for Hong Kong and its people but if they do that's a 100% chance they will have to go to war with China.\n\nThe US and UK will do absolutely nothing. Hong Kong isn't worth the trouble.\n\n > Is there a way that Hong Kong could be its own nation peacefully or will it just end up being a diplomatic nightmare that could end with China doing whatever they want.\n\nNo, because China just doesn't work that way. Geopolitically, it **can't**.\n\nChina, historically, has only two states that it ever exists in; a strong nation with a centrally government that *dictates* control to individual areas, or complete anarchy where China is broken up into pieces. China cannot allow Hong Kong to leave, because then other parts (particularly the other cities in Southern China like Macau) will *also* leave. That region has always, historically, been the first part to secede from China in the event of trouble.\n\nGranted, there *are* things that the outside world can do to push things in a favorable direction, but they would likely lead to the breakup of China as a nation-state. Which would be very chaotic in the interim (particularly bad because China has 400 or so nuclear devices that someone would need to secure)." ]
In order for the US government and election system to be reformed, who all would have to act on it and approve of it? (Is it even a feasible hope for the voters?)
[ "Probably a referenda which is then enacted by legislated by Congress and signed off by the President." ]
How do GPS satellites and receivers compute our position without synchronous clocks between them?
[ "If you assume that the receiver have the exact same time as the transmitter then you would only need 3 satellites as you would be able to know the exact distance to each satellite alone just based on the difference in time. However the receiver does not have an accurate clock. But it is accurate enough to measure the time between the signals from two satellites. So it does not know its exact distance to a single satellite but it knows how much closer it is to one satellite then the other. This is why you need 4 satellites instead of 3. In practice 4 satellites is too few to get an accurate position and you need far more in different directions.", "The receiver has \"atomic time\" by constantly resetting itself based on the satellite signals it receives. \n\nIt receives 4-5 signals all of which can *only* overlap at a single point in 3D space. The receiver, knowing it's inaccurate, also knows that 4+ spheres can only overlap at a single point when given the \"correct\" (atomic) time. From there it can do some fancy math to figure what the correct time *must* be for all of those spheres to overlap at a single point, any other time must be wrong so it sets itself to the calculated \"correct\" time. \n\nIt then uses that correct time to perform the appropriate calculations against all the signals it received to figure out its location in relation to the satellites. \n\nSo essentially, because of how spheres relate in 3D space, the receiver is able to calculate the atomic time itself by calculating exactly where the spheres overlap (only the atomic time will cause all the signals to overlap at a single point).", "What's important is the delta between the times transmitted from the satellites. If I know that, then I know how much further away from one satellite than another I am. Given that I know where the satellites are (they're geosynchronous), each pair of satellite info generates a limited area where I could possibly be (the set of location points where dist(sat(a)) - dist(sat(b)) = dist(delta)). Adding the information of one more satellite generates three pairs, which narrows down the set of locations. A fourth satellite's information give us six sets of location points to compare. The point that's a member of all six subsets is where you are.", "Part of what sent by the GPS satellites is their time. GPS receivers can use this in their calculation to deal with the problem that the GPS clock is more accurate.... which is to say, the GPS signal tells the time, and the less accurate clock on the ground changes its time constantly to be in alignment with the accurate clock from GPS, which then allows them to perform the correct calculation as it now has the correct time (according to GPS)", "The GPS satellite transmits it's own location, and the time. The US military has base stations that update the satellites with their locations based on radio/radar telemetry daily or so. It's an actively managed system." ]
How do our bodies fix the mistakes that proteins/enzymes make every now and then?
[ "Most mistakes don't matter, but defective proteins have certain physical characteristics that cause them to be digested by other specialized enzymes.*\n\nMistakes in DNA replication are repaired using the complementary strand as a template (the older strand will have chemical modifications that distinguish it from the new one).\n\nSome mistakes cannot be repaired, and are widespread, so you just die.\n\n* Note added: As was pointed out, prion proteins are not degraded when mis-folded, and can induce the same characteristic configuration into other, correctly folded, prion proteins, even on other cells. They are exceptional in this regard, although not unique.", "If you’re talking about DNA, the body has a self-checking mechanism to make sure the DNA was copied correctly, if it wasn’t the body will kill the cell, if the cell stops responding to the body and starts reproduce itself, that’s cancer" ]
If we are supposed to eat meat, how come we have to clean it and cook it, but all other animals eat it raw?
[ "Humans do not have to cook meat. Sushi, Steak Tartar, Ceviche, are all food preparations that involve uncooked meat. What cooking meat, and other foods does is kill pathogens on the meat that can make us sick (a lot of animals get sick or die from food contamination). This is particularly important as we do not eat meat immediately after the kill like most predators do. Instead we keep it in refrigeration for days or even weeks (or longer) which increases the risk if eaten raw. \n\nCooking also partially breaks down the food making it easier to absorb the nutrient within the food. We spend less energy to get them.", "Cooking/cutting/pounding meat (and vegetables) means that we have to expend less time chewing, because cooked food is softer and easier to digest (so we also get more nutrients out of it). Spending less time chewing means our jaw muscles can be smaller, making more room for our brains. We can see when this change occurred in the fossil record, because anthogenic apes' brains grew as their jaw muscles shrank.\n\nNow that diseases have been passed back and forth between humans and farm animals for a few thousand years, making some of them more virulent and dangerous, it's also safer. But we can (and some people still do) eat organs and raw meat.\n\nSo taking all that in context, we were always omnivorous, meaning that there is no one human diet. Our bodies will adapt to what we choose to eat, and meat has been one of those things for millions of years.", "Humans actually don't have to cook our food and there are many meat dishes such as sushi and steak tartar, which are served raw. In general, however, food is cooked for health concerns. For instance there are several types of parasites and pathogenic bacteria that can be transmitted to humans by eating uncooked or poorly cooked meat. By cooking the meat properly, these organisms are killed. For most of us, these infections might make our lives a little unpleasant, but would probably not kill us. However, because such a high concern in modern western society is focused on quality of life, we choose to do whatever is necessary to limit any unnecessary unpleasantness. As far as other animals are concerned, the risk of contracting a potentially debilitating parasitic infection is a matter of everyday life. These animals don't really have a choice. While some individuals may feel under par as a result, we typically don't notice it. In their weakened state, they may also be more prone to predation and end up becoming someone elses dinner. If you've ever had a sick dog or cat, you notice that they hide their illnesses quite well, and typically a critical health condition is not spotted until it is too late to really do anything about it. In the wild these individuals would be the first ones to be hunted down.", "> If we are supposed to eat meat,\n\nThat is not the correct way to thing about it. Supposed to imply some intent behind it. We have evolved so that we eat meat. Cooking food on fire is older then the modern human species. Our ancestors perhaps as early as 2 million years ago cooked food because we can see changes in there physical structure. It is easier to eat cooked food the raw so the the shape of our jaws and skull changes. So we might be adapted to eat meat but that is not the same as supposed to. \n\nThere is evidence of control of fire 1 million years ago and hearths that is at least 790,000 years old. Biological modern humans are less the 300 000 years old. So cooking food is older the us as a species.\n\nSo humans have evolved in a environment where cooking existed and it is likely a important factor in out evolution. So we are in may ways adapted to eat cooked food. Cooked food is easier to eat and provide more energy because the heat break it down so we do not have to do it internally. No other animal is adapted to eat cooked food because not other animals have learned to control fire.\n\nSo we can eat uncooked food but is primary adapted to eat cooked food because it is more efficient.", "We don't have to clean/cook it, humans can eat it raw. However, we've discovered there are many types of bacteria and other nastiness which affects humans that is killed when we cook meat. It's easier to avoid getting sick by cooking all meat than running the risk of potential sickness by not cooking it. \n\nA good steak for example, can be seared on the outside to kill any bacteria that's contacted the surface but still cold/raw on the inside and be perfectly safe to eat. \n\nOther animals who primarily eat raw meats have different bacteria in their gut that can handle more types of bacteria than humans can, making raw meat generally safer for them than for humans." ]
Why is it that thinking about things to hard makes them harder to do without thinking? (Sleeping, swallowing)
[ "Your brain stores muscle memory in a series of neural connections that fire in a squence and are reinforced every time you do it correctly. \n\nThink of it like a path in the woods. Every time someone uses that path, it gets worn in better and it gets easier to go through the woods to get home. \n\nWhen you think about it too hard, you're not letting your brain trigger that sequence. You're telling your brain to do distinct actions as part of what you want to do. Which you are terrible at. \n\nSo instead of just following the path you try and force your way through the woods. It's slow and awkward and you usually don't end up where you want to be. \n\nSleep on the other hand has more to do with being relaxed. A long long time ago if you were stressed it was for good reason. Predators, rivals, food. So you wouldn't sleep because maybe that thing you're stressed about would kill you. \n\nWhen you lay in bed thinking \"just go to sleep.\" And you don't go to sleep, well that stresses you out. So now you think \"come on! If I don't sleep I'll be tired tomorrow!\" That stresses you out more. Your brain doesn't know you're stressed about wanting to sleep. It just knows stress is going on and that's bad so better stay awake to deal with it." ]
On boats & ships, how do propeller shafts remain watertight despite the friction caused by the propeller movement?
[ "The boats I'm familiar with, sailboats around 30 - 40 ft, it's not water tight. You should get about 1 drip every 30 seconds. You need a bit of water coming through to act as cooling. Then you have a bilge pump to pump the water back out.\n\nThe shaft goes through what is called a stuffing box. (_URL_0_). You have a fiber like flax, hemp or some type of rope and treat it with wax or oil and then pack it around the propellor shaft. You want it tight enough that water doesn't come through too fast, but loose enough th shaft can still spin and few drops of water keeps everything cool.", "Here are some longer answers and a few drawings:\n\n_URL_1_\n\nBasically, it is not 100% watertight, but with proper materials stabilizing the propeller tube and proper lubrication, the remaining amount of water coming through is small enough to be pumped out easily.", "Exact same method as your car's engine/transmission/rear axle/etc... \n\nThere's a rubber and steel gasket that seals against the spinning driveshaft and the surrounding housing. \n\nIn cars, a bit of air sneaks past the seal, goes through the oil and is burped through a breather at the top of the gearbox. \n\nIn boats, water sneaks past the seal and is pumped out on a regular basis.", "How does this work on submarines, do they just use the same stuffing boxes but engineered to the much higher pressures, or?", "Quick external source: _URL_2_\n\nGranted, that isn't a maritime application, but the concept is the same.\n\nThe short of it is that you have packing (somewhat flexible material) that is compressed around the shaft so that it maintains the seal.\n\nThat said, such seals do not necessarily need to be *perfectly* water-tight. They mostly just need to restrict flow enough that the bilge pumps can comfortably keep up.", "I used to be a mechanic on a submarine, the shaft seals leak. There is a catch-basin just under the shaft hull-penetration. A pump cycled on a regular basis to clear it out.\n\nThe tank it pumps into has to occasionally be pumped overboard, preferably when we are reasonably near the surface.\n\nThe Sturgeon class I was on had seven seals around the shaft to slow the leakage. The deeper we are, the faster it leaks.", "So, a little off topic, but you might also be interested in labyrinth seals: [_URL_4_](_URL_3_)", "Not exactly the same problem, but a related one: submersible pumps have to solve the same problem (turning a propellor/impeller underwater while keeping the motor part dry). The most common way they do it is to simply have the wire coils of the motor sealed off from the magnetic part of the impeller. Magnetic fields pass through the plastic and turn the impeller while there's no physical connection for water to pass. \n\nThis requires an electric motor, of course.", "Poorly. Boats are surprisingly leaky, so they have pumps that take any tresspassing water and chuck it overboard." ]
Why do directors not film scenes in the order in which they appear in the movie?
[ "In those two cases, if you film the climax of the movie first, you have time to do it right, and fix anything that may go wrong in the process.\n\nWait and do it last, you might have to delay the movie if any issues come up.\n\nAlso, cost and simplicity come into play. If you have a bunch of scenes in your movie that all occur in one spot, it makes sense to film them at the same time. Same thing if your actors are wearing the same clothes in different scenes.", "The equipment or sets might not be ready or available at the time, or it may simply be more convenient. For instance, let's say my movie has 3 locations, a diner, a park, and an office. I'd I do things in chronological order, I'd have to go back and forth between the 3 locations a bunch of times. Alternatively, I can film all my diner scenes in one go, office in one go, and the park scenes when I get permission from the City. \n\nMany sets, places, or studios only have a limited time to film, so you need to do all the scenes involving it in one go. There was my city park example, but other things are limited, too. Maybe one of your actors only has a few days to film, you need to get all that person's scenes filmed while you can. Equipment might only be available for a short time, as well as other things I can't think of.", "Why would they do that? If there are 4-5 scenes needed at the same set, they would just film that regardless whether the scene plays in the final movie. \n\nMovies have international scenes that might occur at various points in the movie. It makes no sense to fly in a film crew multiple times just to \"film in order\".\n\nLogistics and cost is a huge thing to manage when filming. The order of business is to arrange things to minimize them.", "* Making a movie involves a huge amount of scheduling things like:\n * Locations\n * Cast \n * Crew\n* The order in which scenes are filmed is mostly based on the best use of all those schedules. Maybe the location for the end of the movie is only available for a certain amount of time and so the production wants to use it right away in case they need to re-shoot. \n* If any locations or sets are used more than once it makes sense to shot all the scenes that use that location or set at the same time instead of settling everything up for a scene there, then taking all down, moving it, and then bringing it back and setting it up again.", "The most important reason is location availability. Some sets may be ready before others. Some may be outdoor locations or specific buildings or film lots, so there's gonna be a schedule based off the best times or when a film crew is allowed to film in said locations. Then once you're at the location, you'll want to film everything that happens in that location, regardless of when it happens in the film, that way its all done, you can move on and hopefully not worry about said location anymore. \n\nAnother (shorter) reason could be actor availability and scheduling. \n\nObtaining footage in chronological order wouldn't really make that huge of a difference in the long run among the many many wheels that are turning.", "We’ve got lots of good reasons so far but I haven’t seen this one yet: A big, important scene that has lots of special effects will take more time to render. You want to shoot those scenes early so the SFX folks will have time to do their work. This is especially true where preview trailers are concerned. The marketing team will want some of the big, dramatic SFX shots to put in the previews, so those shots need to be completed first.", "Easy answer? Avalibility. Filiming is a juggling act between dozens and dozens of people and places. You need to have all actors, stunts, sets, make up, costumes, and crew all good to go and sometimes people have other things, sometimes sets are hard to build or you only have a specific location at a specific time. Yeah filming in order would be cool but the juggling act rarely allows for it.", "You film in the order that gets you finished the quickest and is the cheapest. \n\nFor films with multiple locations, it doesn't make sense to film in chronological order since if the beginning and ending are in the same.place but the middle isnt. \n\nThen there are scenes that require certain equipment or certain actors, you want to get those all out of the way too in one go since you dont wanna rent equipment or pay people for idling." ]
How does a software input into a computer physically change a transistor
[ "Engineer here, this isn't 100% the entire story, but it's ELI5.\n\nSoftware input doesn't change the shape, state, or move or do anything physical to a transistor. A transistor is just another component whose shape and material will manipulate the flow of electricity in a specific and predictable way, just like any other component such as a resistor, inductor, or capacitor. What makes transistors so special is that they have three pins, where varying the power applied to one input can vary the amount of power that gets through from the other input.\n\nThese transistors can be arranged into units called logic gates, of which the most commonly used for commercial applications is the NAND gate. The way the NAND gate works is that it is always on (1) unless both inputs are on (1), in which case the gate turns off (0). By some clever methods, these NAND gates can be arranged to form any other logic gate.\n\nThese logic gates can then be arranged into something even larger, like an Arithmetic Logic Unit (ALU). Which takes inputs of high (1) and low (0) power on each individual wire and can do basic math like addition and subtraction and other things by assuming that the arrangement of these wires means a number.\n\nWhen someone writes software, they're writing a series of mathematical and logical operations that get put into a queue of sorts where they get fed into this big lump of logic gates in order.", "Input is made on a wire by turning a voltage on and off. (We call on 1 and we call off 0.) Transistors respond directly to voltage.", "* As far as the hardware is concerned, everything is a value in memory. \n* Software tells the processor what values to put in memory.\n* Software tells the processor where in memory to get values from. \n* Transistors are part of the hardware they just react to changes in voltage." ]
Why are baseball bats and cricket bats shaped the ways that they are?
[ "The cricket bat shape has evolved to be optimal for striking the ball when coming to you as it does from a bowler, and holding it as batsmen and women do. There is a \"sweet spot\" on a bat, more or less opposite the widest part (front to back) - hit a ball square on there and it will fly.... when you watch top batsmen, it's amazing how far and fast the ball travels when they barely seem to hit it with any force; just stroke at it and, catch it right, it will go....\n\n I presume the same goes for baseball bats." ]
Intel Optane memory
[ "Optane Memory is not RAM. Think of it as sorta booster for your Hard drive and ram interaction. But absolutely not RAM and you don't add them together. Optane memory is sorta more like a really fast SSD that works with your HDD to increase speed.\n\nThese lots of misleading ads on this claiming more memory and counting it as RAM (marketing!), but its all just nonsense. It is not a substitute for ram, its more of an addon to it.\n\n4GB of RAM is actually pretty budget build for a pc right now, thats an odd spec to have 4GB Ram and an optane memory. I'm guessing this has a traditional HDD, so in that case, the optane memory is really meant to speed up the HDD turning it into a hybrid SSD/HDD drive and give sexy specs, but be on a budget price, as SSDs and more RAM are going to be significantly more expensive than the HDD/Optane combo.\n\nIn the past, budget builds, since SSDs were really expensive, often contained Hybrid HDDs (a HDD which contains a small SSD as well) or you would get a seperate small SSD for the OS, and a HDD for data. As SSDs have decreased in price immensely though, this is falling out of favor except in more budget builds. However even in good builds there is room for an optane memory, but thats not what its use is here in your build", "No, it's not the same.\n\nSDRAM holds working data that the processor is actively using for calculations. The more it has, the more stuff you can have open and working at once; this gets assisted by the hard drive in most computers as most users are *really* only focusing on using 1 or 2 applications at a time in most cases, but your RAM is the practical limit on how much you can be doing at a time before you get slowdown.\n\nOptane memory is, from what I've read, a way to make your most critical files and applications available to read faster when you're using a lower-speed HDD to store data; it's essentially like having a 16gb SSD in the computer to load some stuff super fast, but it's not accessible to you really, the computer decides what goes there so it can load fast.\n\nBut at the end of the day, Optane memory isn't memory in the same sense that your RAM is.\n\nAdvertisers don't seem to care, and add the optane memory to the \"memory\" specs when advertising a computer, though. so pay attention to that.\n\n > What are the real world results of comparing say this type of spec to a computer with 8gb or 12gb of SDRAM.\n\nIt depends on a few other factors and usage, but by and large, the biggest thing that would stand out to me is that if I had a game that needed 8gb of RAM, something with 4gb of SDRAM and 16gb of Optane memory would not meet the bill, while something with 16gb of SDRAM would.\n\nIf you're just a regular user though, you will probably get better performance out of a computer with 8gb RAM and 16gb Optane than you would a computer with 16gb RAM, just due to quicker load times for applications.", "My understanding of Optane memory is it's not much different than a typical SSD. It's a bit faster due to newer technology but also in smaller amounts which makes it much cheaper. \n\nIt is NOT a replacement or supplement for RAM, it does not get added to your RAM amounts. 16GB of Optane and 4GB of SDRAM means you have 4 GB of SDRAM and 16GB of SSD-like storage space. \n\nOptane is designed for users who want SSD-like performance for their primary system, but don't want the high cost of replacing their HDD with a SSD. Instead, they use Optane + HDD, Optane stores the OS and maybe primary software they use to speed up those applications, but leaves all the big storage (videos, pictures, etc) on the slower, much larger, HDD which doesn't need fast access. \n\ntl;dr - For a normal business/home user, Optane is a cheaper alternative to SSDs, allowing them to keep the large storage of a HDD but speed up the OS and applications. For a power user who's buying a SSD anyway, Optane offers little to no benefit." ]
why do you have to avoid grapefruit while on so many medications?
[ "You have molecules (enzymes) in your body that break down medications and other molecules. There is one family of enzymes called the CYP3A family. Enzymes in this group are responsible for breaking down (metabolizing) more drugs than any other group of enzymes in your body. One of the components of grapefruit juice blocks these enzymes from working, which means the enzymes do not work to break down the medications and your body cannot get rid of the drug quickly enough. This can lead to medication build up in the body which can then lead to side effects or toxicity.", "Grapefruit blocks an enzyme that has an important role in metabolizing drugs. This can mean one of two things:\n\n1. the drug stays in your body too long - building up to levels that aren't cool.\n2. the drug doesn't enter the system in the way it is intended resulting the drug not doing the good thing it's supposed to do.", "Grapefruit juice inhibits CYP3A4, an enzyme involved in the metabolism of many drugs. Without that working at the normal level the drugs can build up to higher levels than desired and in essence lead to overdose." ]
Will it be possible in the near future to create laptops that are able to withstand severe heat?
[ "The problem is one of \"small.\" \n\nIn order to make the laptops as flat and light as possible, everything gets jammed together. Airflow suffers, and components run hotter.\n\nCompound this with components getting faster, which causes then to run hotter, too.\n\nBigger, bulkier laptops, or laptops without the highest-end components don't have these problems because they don't generate the heat on a confined space.\n\nLaptops exist with the highest-end components, and they don't overheat, but they're an inch thick and weigh a couple pounds.\n\nA better solution is to adjust your expectations of what a laptop is for, use one with less power for when you're away from the desk, and use a high-end desktop for the heavy work. Or offload all of those computer things you need to do to the cloud, leaving just displays and input for you laptop's chores.\n\nIf you want a desktop in a tiny package, hear is the price you pay. Well, money, too.\n\n*Heat is the price you pay... Also paying the price for not proofreading...", "I dont k ow where you are but I used \"ruggedized\" panasonis toughbooks in the desert years ago for work in temperaturs well over 100 f. They weren't the fastest by any means but they worked.", "I think it is more likely that laptop components will become more energy efficient than they currently are, as it would not only benefit heat dissipation but also battery autonomy. This is already becoming reality, as the newer chips being produced are becoming less and less energy demanding. For instance, a latest gen 6 core desktop processor currently draws 65W of power, we can expect a laptop part produced with the same technology to draw half or even less than that if clocked lower and maybe with a couple less cores." ]
why does some gum lose its flavor so fast?
[ "The flavors in gum have to be able to get released from the gum to have a taste. That means that they should bind better to spit than to the gum. Gum itself doesn't break down much from saliva. The flavor in gum lasts quite a bit longer than it used to.", "Basically, whatever chemical it is that gives the gum its flavor has to travel from inside the gum to your tongue, where your taste buds sense it before your saliva breaks it down, or force from chewing/swallowing/moving around in your mouth moves the chemical somewhere else. How long the flavor lasts comes from how much of that chemical is in the gum to begin with, and how long it takes for the natural components in your mouth to take it out of the gum, through your taste buds, and then away from your tongue.", "There’s a chemical called aspartame (or sucralose) that is basically a lab made sugar substitute. These sugars are able to have a sweeter and longer lasting taste than most other kinds of sugar. It isn’t very healthy for you, so some gums tend to leave it out, causing that gum to taste more bland than you’re used to, and to lose it’s flavor quickly", "2 things are happening, you are breaking down/off the flavour of the gum and your mouth is becoming familiar with the flavour." ]
How are animals like felines able to jump and leap insane distances? What makes humans unable to do the same?
[ "The design of the hind legs has a lot to do with it. \n\n\nAnimals like cats and deer walk on their rear toes. The \"heel\" is quite high off of the ground. So their rear legs have three major segments instead of two, giving them more power and range of motion. This leads to bigger jumps. \n\n\nAnd you also have to be able to land safely. Humans have to land on the same legs that they jumped with. Four legged animals jump with their rear legs, and land with their front. The front legs and their joints have evolved to be great shock absorbers. For example, the shoulder joint of a deer has an incredible range of motion, because there's no direct connection from the leg bone to the bones of the torso. It's all just connected by soft tissue.", "A cats body is better suited for being lean and agile, it was just created like that by evolution to behave so, humans legs aren't like cats, were much more stuff and strudy because of our evolution. When we were cave men we weren't jumping around trees or trying to pounce on our prey. TLDR: evolution and our genetics are just too different to behave like cats.", "[Square/Cube law.](_URL_0_)\n\nSimplest way I can say it: as something gets bigger on the outside (taller, longer, etc), it gets significantly **more** bigger on the inside (weight). It's the same reason that much larger animals (elephants, rhinos) can barely jump at all. \n\nYou can see the square-cube law at work in normal humans. An average 2-3 year old human will weigh about 30 pounds, and be roughly 3 feet tall. A full grown adult male will be around 6 feet tall, and roughly 180-200 pounds. Though these numbers will obviously vary from person to person, you can see the distinct trend. At double the height, a human weighs 6 times as much. \n\nBut to your point, you can see a similar trend the jumping capabilities of cats. An average house cat is 9 inches tall at the shoulder and weighs 10 pounds. They can jump 6 feet vertical. A average tiger is roughly 3 feet tall at the shoulder and weigh 500 pounds (though it varies a lot by gender and subspecies). They can jump 12 feet vertical.\n\nAt 4x the height, a tiger can only jump 2x the distance, because of the square cube law (and 500x the weight)", "Keyword: Hind legs/limbs\n\nCats and Dogs for example have a common back-leg feature called hind legs. Hind legs allow an animal to experience a greater range of motion in the leg, and therefore power when the legs become fully stretched during a jump.\n\nHumans would actually be able to jump higher if given hind legs, but usually four-legged animals have these." ]
When you stretch and hear little cracks in your back, what is actually taking place in the body?
[ "That sound is called cavitation. It's the same as cracking your knuckles OR is could be the realignment of misaligned bones/joints, OR if it's more of a crackle/pulling sound, it's the muscle fibers. 👍\n\nSource 15+yrs experience with a DC program and training over 1K DC interns.", "What you are hearing is the constant formation of bubbles in the joints that pop and form. These bubbles are made of a fluid called Sinovial Fluid, and acts effectively as oil for your gears so they can move and rotate smoothly." ]
What actually is a “gut feeling?”
[ "A gut feeling is that feeling that something is wrong without any obvious outside information, just your instincts.\n\nWhat it actually is, is your blood pressure raising due to the uncomfortable and unknown situation at hand. Your subconscious mind has calculated that the scenario isn't going to go well based on your past experiences, but you have no actual memory of the precise situation.", "Your gut feeling is your instinctual, sub conscious mind analyzing a situation presented to you, comparing it to past experiences, and warning your body and mind to the implications should whatever threatens to happen, actually happen. In case of an emergency, I always trust my gut feelings." ]
If water is non-conductive how does is short electronics
[ "*Pure* distilled water is non conductive. Most water however has impurities in it which are what conspire to make it conductive.", "Pure deionized water is non-conductive, however the rest of the water contains ions and minerals which makes it conductive. The ions in the water can transport the electrical charge and thus short electronics." ]
Why dont we raise space ships with balloons before using rocket engines to escape earths gravity?
[ "The physics are complex, but simply put, look at a Goodyear blimp. The blimp (the actual envelope containing the helium) is huge relative to the tiny cabin attached underneath. Now, replace the tiny cabin with a spaceship made of materials capable of sustaining atmospheric re-entry, fuel for the round-way trip, plus whatever gear and human payload is inside. The helium envelope would have to be so phenomenally huge to even be able to lift said spaceship that it would be totally impractical as a solution.", "The problem isn't getting up into space, that's the easy part. Lots of airplanes and blimps and things get up to those elevations. The problem is you need to go FAST. You see, rockets don't just go UP, if all you did was go up, and I mean straight up perpendicular to the ground right up to the ISS, as soon as you cut power, you'd fall right back down to Earth. You achieve orbit by going tangent to the surface of the Earth, and then accelerating. You end up going so fast, that you start outrunning the planet. They describe space as zero gravity, that's not true. Astronauts experience > 80% of Earth's gravitational field when in orbit. They're actually in FREE FALL toward the planet, except the planet keeps moving, and so they keep missing! That's why everything in space (at least in a space ship) seemingly floats.\n\n & #x200B;\n\nSo the goal, the hard part, is not getting up, it's perpetually falling toward the planet and missing, and that's why we need rockets that generate all that thrust, because the ISS alone is moving at 17,000 MPH, and if you want to achieve EVEN HIGHER orbits, you need to be going EVEN FASTER.", "I like your idea.\n\nGoing into orbit is not just flying straight up and then circling earth, it's actually flying sideways until you're fast enough to \"fall around earth\" and high enough to escape the atmosphere.\n\nA normal weather balloon can rise up to 38km high until it pops, so that would be the maximum height for our spacecraft-balloon. The ISS for example orbits earth at 400km, so the balloon would only cover a rather small percentage of the flight. On top of that, when the balloons pop, you're standing still. To accelerate into orbit at 28000km/h you would need ginormous engines and a very advanced stability control system to steer and rotate your rocket since you're lacking any inertia from the ground. This will be almost impossible.\n\nSadly it's more effective and easier to just start from the ground and get over with those pesky 38km when you've got to travel a total of 400...", "I wonder how much helium would be required to lift a shuttle or what-have-you to the edge of the atmosphere where the shuttle's can fire and take over. Plus the matter of timing it would be difficult I assume.", "Lifting the whole ship would need an enormous amount of helium and that would not be worth it (probably, didn't do the maths). Otherwise, using helium to speed it up wouldn't work, since helium doesn't rise fast. The rocket would go faster than the raising helium, which means the balloons would only cause more drag and would pop even sooner." ]
How can a Minecraft world be infinite ?
[ "They're not infinite, just unlimited. Only the parts of the world that you have seen are created, as you see them." ]
why are most (all?) green parties against nuclear power?
[ "This is a handy link-\n _URL_0_\n\nas to the potential negatives of nuclear power, I will summarise them for you though to save time.\n\n1. Implementing enough nuclear power plants in time to cut emissions before 2050 seems financially unviable\n2. Inherent error, human risk, design flaws even natural disasters\n3. Deters investment into actual, real, renewable energy\n\nI guess for the most part it's kind of just putting all your eggs into on basket again, the price and demand of uranium and radioactive substances would also surely go up, and I guess in the long term if trying to power the world off nuclear power, this would also involve giving untrusted countries access to isotopes.\n\nJust my two cents though, I could be wrong about it all.", "Because they dont understand nuclear power. Its clean it's safe and it's awesome. It's way less environmentally damaging than most other \"green\" energies. They just listen to the lobbyists who sell them the right message and never question it." ]
What is your body doing when you have a “gut feeling?”
[ "This was asked earlier today. Please search first." ]
In the photos you see of nebulas, galaxies etc. What exactly does the coloured smoky areas represent? Is it just light or something cooler?
[ "Those are clouds of gas. As a quick and dirty guide you can break then into three groups.\n\nRed ones are thicker regions of hydrogen that are warmed by nearby starts to glow a red color.\n\nBlue have dust in them and are reflecting light.\n\nDark ones can actually have larger dust grains, molecules of hydrocarbons etc. They are blocking most light from passing through.", "> Is it just light or something cooler?\n\nWhy not both??? \n\nThis is going to be a long answer. \n\nIn a nebula, the colours come from the glow of different ionised elements under different circumstances. Hydrogen is the most common element in nebulae and is found everywhere. There's also sulphur ions (sulphur that has lost one electron), found near the edges of nebulae, and oxygen ions (oxygen that has lost two electrons), found near hot stars. \n\nInteracting hydrogen emits red light. Sulphur ions also emit red light. And oxygen ions emit greenish light. \n\nNow, because hydrogen is so common throughout the nebula, and sulphur is common near the edges, if you just left the colours as they are the whole thing would just appear mostly red and bland. \n\nSo, the majority of images of nebulae actually use *colour mapping* to create more interesting images--that is, the colour normally emitted by an element is mapped to a different colour to make it more distinct. The red from hydrogen is assigned to appear green, the red from sulphur is left as red, and the green from oxygen is assigned to appear blue. You will notice that this matches the typical red-green-blue (RGB) breakdown used in the vast majority of modern screens and image processing. This particular method of mapping is called SHO (sulphur, hydrogen, oxygen--corresponding with red, green, blue); there are others, like HOS (where hydrogen is red, oxygen is green, and sulphur is blue) and SNH (sulphur is red, nitrogen is green, and hydrogen is blue), but SHO is by far the most common. \n\nThe result is some spectacularly colourful images in which the light emitted by various elements is more distinguished. \n\nNow for galaxies. Galaxies are a bit more straightforward because, well, they're made up of billions of stars and other light-emitting things, so as you might imagine most of the colour just comes from that. Blue spots in galaxies are areas with young, hot stars, which tend to glow blue because they're so hot (just like the flame from your kitchen stove). Yellow spots are older stars that burn yellow/orange (like our own Sun). Red spots are nebulae--as mentioned before, they're the red from dense clouds of hydrogen." ]
Why don't shoes last nearly as long as vehicle tires?
[ "First shoes impact the ground differently, tires roll, assuming properly aligned and balanced wheels. Shoes impact the ground and skid slightly that's why the heel or ball of the foot wears out faster.\n\nTires can be made of heavier rubber, heavy shoes like work boots or hiking boots are not always desirable. So they use lighter materials as a trade off.", "Tires are made of a special rubber that is enriched with sulfur to become \"a big round molecule\" that on top of that gets carbon to make it sturdier and stronger(because of the carbon tires are black and burn well) but shoes get different normally cheaper rubber and polymers that split into pieces easier. tires also are prepared to be on asphalt, but shoes have different types of surface that they are suitable for(you don't go with high heels in dirt) so it depends on the shoe, rubber and terrain." ]
What happens causes people to start making fast movements (tapping feet, fingers, pacing back and forth, etc..) when they're waiting, or just impatient, instead of just sitting or standing still?
[ "Our brain and nervous system are composed of modules that aren't necessarily in sync. Your higher functions understand \"we're at the airport so we need to wait\" but your lizard and mammalian brain areas are concerned with food, reproduction, exercise, so they send nonverbal signals like itches to make you shift around and avoid injury, repetitive movements to exercise and maintain temperature, stomach rumbling to signal hunger, yawns to signal sleepiness or boredom. \n\nObserve yourself when you do things, often you'll do something and then explain to yourself what you've done. An attractive person walks past, you look at them go and think \"I am looking at a hot person\" but what happened was your animal instincts made you look and your frontal lobes got the memo \"Hey, we're taking over the eyes and neck for this important bit of research\" afterwards. But your frontal lobes are where your personality lives and it likes to think it's in charge so it just rewrites history into \"Oh I like looking at nice bodies so I decided to do that\"\n\nBut if we actually wire you to a fmri machine we can track the impulse to do a thing and the moment when you \"decide to do a thing\" and there's usually a delay of up to a second (Actually up to 7 [now that I check](_URL_0_)\n). \n\nYour higher functions are more about suppressing things than actually deciding what to do, everyone gets intrusive thoughts like \"I could grab that cop's gun and shoot him!\", they're perfectly normal because your brain is constantly proposing actions and your frontal lobes are there to anticipate consequences \"No we'd get arrested and sent to the electric chair what the fuck is wrong with you\" so normally we just sit there, twitching a bit while various random impulses try to take the wheel." ]
Why do colors “clash?”
[ "I’m no scientist but I bet it has something to do with why certain music notes don’t sound good together. The “wobble” you hear when two notes clash is caused by the wavelength of those particular notes. Seeing how light is also a wave, it wouldn’t be unreasonable to assume that the two waves are clashing causing a displeasing visual, just as the notes caused a displeasing sound." ]
why did my body odor change moving from Florida to West Texas.
[ "You are what you eat. Literally. And, you sweat out what you eat and drink. \n\nDifferent location means different food, different minerals and such in the water, etc. You will notice these differences when you sweat them out, until they become your \"new normal\"" ]
Why do laser beams have "brighter dots"?
[ "The light is striking dust and other particulate matter in the air and therefore being scattered/reflected. Some gets reflected toward your eyes so you perceive those spots as brighter.", "these are called \"speckles\" and are typical for coherent light like lasers. \n\nThey are created by interference from irregularities within the beam, created from the irregularities of the surface where you observe the beam scattered (as you won't look directly into the beam).\n\nOften these speckles are unwanted, as they give a certain \"noise\" in the beam. Sometimes they are needed for certain applications where you need coherence, and sometimes they are actively exploited (those speckle patterns can act as a very sensitive sensor to the exact location of your laser beam to the scattering surface, say in a laser-based computer mouse)." ]
How does sunscreen work?
[ "The part of light that burns you is called UV, or ultraviolet light. You can't see it, but it's part of the light we get from the sun. Sunscreen reflects and scatters the UV rays or absorbs it instead of your skin absorbing it, depending on what the sunscreen is made of.", "Sunscreen is filled with little bits of stuff that are the right size and shape to block the type of light that causes sunburn.", "Sunscreen works by painting you over with a cream that absorbs UV rays. This works like looking through [a red/blue 3d glasses set](_URL_0_) does, only the color it filters you can't see. \n\nAfter a short time, the material fades off your skin, from exposure to surfaces, water, and natural shedding. \n\nWhen this happens, you need to apply more, or you can get burned. \n\nThink of it putting ice in your drink - it can only cool for so long before its run out of energy to absorb, then you need more or your drink gets warm.", "If you google pictures taken with ultraviolet light and sunscreen you can see how it is effectively opaque to those wavelengths. This provides a barrier between skin and the sun." ]
why is it that a lizard can jump off insane heights but not take any damage and be fine but if we scaled us down to the size of a lizard we'd die from that high of a fall?
[ "Lizards weigh less, so the impact when they land is a lot lower. If I fall, it's equivalent to a 100 pound person landing on me. If a 300 pound person falls, it's equivalent to a 300 pounds of person landing on them. The gecko just takes a few ounces of weight." ]
Body temperature what makes it 98.5 and how does it regulate it?
[ "Keeps warm by :\n\n- Hairs standing up on body to trap heat\n- shaking to generate heat\n- (shut down parts of the body - in extreme cases)\n\nKeeps cool by :\n\n- sweating ( a layer of sweat helps take heat away from the body which then transfers to the air around us ). Thus cooling the body." ]
How does Google maps estimate the quickest way to get somewhere even with traffic involved?
[ "Well, for starters, Google has all the maps and knows all the speed limits on (almost) all the roads. They can easily figure out that taking a freeway 10 miles @ 70 mph is faster than back roads for 7 miles @ 30 mph.\n\nGoogle then takes that data and augments it with three types of data:\n\n- Road condition data. Most cities report construction, accidents, road closures, etc., so Google can factor those into its estimations.\n\n- Real time traffic data. Every phone running Google maps is sending Google real time GPS location data (if they haven't opted out). Google can measure the distance traveled inbetween pings and estimate your speed, which gives it a good idea of traffic conditions (someone going 20 mph on a 70 mph road is clearly stuck in traffic).\n\n- Historical data. Thanks to point 2, Google can make reasonable guesses as to what traffic will look like at significant times. If a freeway always has traffic at rush hour, odds are it will have traffic at rush hour today.\n\nAdd those three pieces of data to the map data, and you can create pretty good real time estimations of speed, which translates directly to figuring out the best (i.e. fastest) route." ]
What's the difference between having undetectable levels of HIV and being cured?
[ "You have spotted the thing.\n\n & #x200B;\n\nFrom a functional perspective, if you are undetectable, you cannot pass on the virus to a HIV- person. The virus is no longer in your blood (but it can hide in other tissues which is why it comes back if you stop taking your ARV meds).\n\n & #x200B;\n\nWhile you are undetectable, there may possibly be strains of HIV you can catch that are medication resistant (these are talked about in stories about people who are on PrEP but still seroconverted), and of course being on those meds isn't a walk in the park. They can have some undesirable side effects." ]
How do celebrities, like OJ Simpson, who lose their fortunes still live seemingly lavish lifestyles?
[ "Because his income can't be touched.\n\nAs a former NFL player, OJ has a very large pension, and pensions can't be attached in civil lawsuits.", "By becoming judgement proof. \n\nIf you expect to be sued, you can liquidate the majority of your assets and then purchase the most expensive mansion you can outright buy in a state like Florida. That state's homestead exemption, which does not let a court force you to sell your primary residence to satisfy a civil lawsuit, is very strong. \n\nThe Florida homestead exemption is unlimited. Whether your homestead is worth $100,000 or $10 million, it is protected against the claims of creditors. Otherwise, you could be forced to sell or relinquish many assets, except those with protections, i.e. pensions, primary residence.\n\nIn Tennessee, for example, the homestead exemption is limited to just $5,000, an amount set in the 1800s to protect the family farm from creditors. It is largely useless now to protect assets from creditors.\n\nIn bankruptcy, the Florida homestead exemption allows a primary residence of unlimited value to be protected from creditors as long as the debtor has lived in Florida for 40 months or more, and the property is not larger than half an acre in a municipality or 160 acres elsewhere.\n\nOnce the creditor's case or the debtor's bankruptcy has been discharged, then you sell the residence and there is all your money again. If you own the property outright, you can often borrow against it and use those funds.\n\nHowever, fraudulent conveyance to avoid a judgement is illegal. Proving that crime requires 'intent,' which can be hard to judge. In most cases, you need to make these arraignments in advance, and certainly before you are subject to a lawsuit.\n\nRules vary by state, so definitely beware of advice from the Internet.", "If you're famous, you can often get a free ride or even get paid to show up at events or parties. Plus, rich and famous people have rich and famous friends. \n\n Shit, even some no name, not rich people can live a somewhat lavish lifestyle by knowing the right people. Look at Kato Kaelin." ]
Why does pressure build and/or maintain carbonation when you shake a sealed container of carbonated liquid?
[ "The pressure doesn't change. The amount of CO2 gas is constant in the container, as is the container volume and temperature, so the pressure is constant as well. What does change with shaking is that some of the undissolved CO2 at the top is forced into the liquid and forms pressurized bubbles. If the container is rapidly depressurized, the bubbles trapped in the liquid explosively expand and force liquid out of the container. \n\nIf you let the container sit for a while after shaking the bubbles will eventually rise to the surface and you won't get the same effect. When depresurized, the expanding bubbles at the surface won't displace nearly as much liquid as they would if they were inside the liquid.", "Carbonated liquid are liquids that have carbon dioxide dissolved into them. At high pressures the gas can be dissolved into a liquid, then when the pressure drops the gas slowly comes out of solution.\n\nThe rate at which the gas comes out of solution is sped up by the liquid being agitated. So shaking a bottle of soda is literally shacking the bubbles out. But the rate is also effected by the pressure, so if the bottle is sealed, the pressure in the bottle will increase as the gas comes out, which slows the rate the gas comes out, until it reaches an equilibrium point." ]
Can anyone explain, in simple terms, Einstein's theory that time is not absolute?
[ "Let's start with a ground rule:\n\nThe speed of light is always constant for everyone. That's been observed.\n\nNow, what follows from that? It follows that if you're at rest, light will move away from you at the speed of light, from your perspective. \n\nAnd that if you're moving at 99% of the speed of light, light will move away from you at the speed of light, from your perspective.\n\nHow is that possible? If light is always moving away from you at 100% of the speed of light, and you're already travelling at 99% of the speed of light, does that mean that to me (at rest), the light from your flashlight is moving at 199% of the speed of light?\n\nNo--because the speed of light is always constant. \n\nSo what's the solution? Time. In order for light to be moving away from you at the speed of light, but also for the speed of light to be what it is for me, there's only one solution: *time must be moving more slowly for you,* so that you experience the light moving away from you at normal speed.\n\nIt sounds counter-intuitive--but it's true, and we've verified it. There are two major ways we know that time is changing: first, we've actually put a clock up in orbit for a while, where it's moving really fast. And when the clock came back down, it read exactly as we would have expected if time was different--that is, it read *differently* than clocks that weren't in orbit.\n\nSecondly, there are some types of particles that are formed in high-energy collisions in the upper atmosphere. These particles have *extremely* short lifespans, but are moving very fast. Their lifespans are so short, in fact, that we should never be able to detect them down on the ground; the particles should be decaying before they reach our detectors down here.\n\nBut we find them. They're moving so fast that, from their perspective, time has slowed down. This means that they age slower from our perspective, and thus live long enough to reach the ground." ]
why have severe allergies for example peanut allergies that can lead to someone's, death not been bred out by natural selection in humans?
[ "Couple reasons. First is that allergies *appear* to be more common in the modern world. The going theory, as far as I've heard, is that our immune systems today are, for a lack of a better word, *bored*. Our environments are so much cleaner than they ever have been, and we have antibiotics and antivirals and antiseptics to do the bulk of the work getting rid of pathogens so our immune systems don't have much to do.\n\nWithout practice to recognize what is foreign and what is truly a threat, our immune systems are more prone to getting it wrong and overreact. None of this is conscious or anything, it's not like your white blood cells actually get bored. It's just that the complex mechanisms that create our immune system are pretty finely tuned for an environment that largely no longer exists so it goes a bit haywire.\n\nTuning is the other reason. The evolutionary pressure you're describing would push for people to have a less aggressive, less active immune system. That's fine and dandy for today, but modern humans are very young, evolutionarily speaking, even just among hominids - and that's modern humans, not modern hygiene and modern medicine! When you consider the ancient battles that have been going on between microbes and hosts trying to get rid of them (including other microbes) the fight has been going on for about as long as life has existed on Earth. For the vast, *vast* majority of that time, our ancestors had to fight off infections without any outside help. So for every person that died from intense allergies, many more died from an infection that their immune systems were not aggressive enough to fight off.\n\nUntil recently, natural selection was pushing us into an equilibrium of having an immune system that was *strong enough* to fight off infections without being so overly aggressive that it killed us, either from allergic reactions or auto-immune disorders. Well, technically it's still pushing us into an equilibrium, it's just that the equilibrium has shifted and evolution takes a very long time. And we're making it take longer because we keep rescuing people with epipens and CPR and other modern medical things. Darn that modern medicine, keeping people alive!^^^^^/s", "Because it isn't a simple gene. It is a combination of genes, as well as an environmental component.\n\nPeople without allergies have children with allergies. People with allergies have children without. Allergies can start off mild and over time develop into serious allergies. Or the opposite can happen, over time the allergy can become less severe", "Modern medicine has a huge effect on “natural selection” in humans. People with poor eyesight previously would have been unable to hunt for food and starved to death, producing less offspring than someone with good vision. Now, we give people glasses and they’re just as likely to survive and reproduce as someone with good vision. People with peanut allergies are given medicine so that they don’t die, and then they go on to reproduce. Natural selection doesn’t really apply to humans these days, as we have enabled people with shitty genes to survive and keep reproducing rather than die due to allergies, etc. \n\nDisclaimer: please don’t think that I support eugenics or anything," ]
Who and how do they pay for town,city and interstate lights?
[ "Generally the utility company tells the city approximately how many streetlights there are and as u/Callico_m pointed out, the city then pays the bill.\n\nThis is why reporting streetlights that are out to the town/city/village/whereverthefuckyoulive is important as you're still paying for it even when it's not working." ]
How is alcohol (mouthwash) removed from city water?
[ "Most city water is not made by reprocessing waste water. \n\nWaste water, containing mouthwash, goes to a sewage treatment plant. There are many processes that go on there, but at least one of them is bubbling air through the water with an open surface. Alcohol evaporates under these conditions, leaving only the water (a big ingredient in mouthwash) and dyes behind." ]
Does the sugar content in fruits rise as they ripen at home? Why do they get sweeter over time?
[ "Sugars can be broken into 3 main categories, mono-, di-, and poly- saccharides. \n\nMonosaccharides are ring shaped molecules made up of carbon, hydrogen, and oxygen. Our body gets energy from processing monosaccharides\n\nDisaccharides are two mono- attached together. Table sugar, called sucrose, is an example of this. \n\nPolysaccharides are chains of many monosaccharides linked together. Starch is an example here.\n\nNow, getting past all this terminology stuff\n\nUnripe fruits are starchy, and our body doesn't process starch as sweet in general. \n\nAs a fruit ripens, the starchy chains break down into smaller units. Our body does interpret these shorter units as sweet, so fruits taste sweeter over time\n\nTl;dr: the amount of sugar is the same, it's just in a different form we don't taste as being sweet" ]
If Earth is within the Milky Way Galaxy, why are we able to see the Milky Way Galaxy while standing on Earth?
[ "You aren’t seeing the entire thing, just a cross-section of it. The Milky Way looks like a dense band of stars encircling the Earth because it’s all around us. \n\nThink about it like this. We’re on a little boat, the S.S. Earth, in the middle of the ocean. If you look out the window, you can see the ocean, even if you’re on/in it. You can’t see the entire thing because you can’t get an external vantage point, but you can see part of it, and when you talk about it you’ll probably call it “the ocean” instead of “the local region of the ocean that we can see” because that’s simpler." ]
How are we able to determine if something technical “makes sense” or “seems right” when we have no prior knowledge on the subject?
[ "You draw on any experience you have with other things that might have something in common. Or it's just explained well enough to give you a basic understanding of how it works.", "This is a very, very good question, and also quite hard to answer - there's no really simple answer.\n\nWith any topic you're trying to make sense of, without really knowing anything about it, the only reliable way (that we know of) you can try to figure out whether you're heading in the right direction is to *test* your ideas/theories, so that the outcome tells you whether you were right.\n\nFor example, let's say you want to build a paper plane but you really know nothing about that, except you've seen actual airplanes from afar. So you know there's wings and a torso of sorts, and maybe some weird thing at the rear. So you build something a bit like that and test it - and it doesn't work. Now you can make small changes and test each one, and maybe they'll perform better so you know you're on the right track, or maybe they'll perform worse so you know you'll have to reconsider. Over time, you build up a more general idea of all these small findings and - hopefully - start getting proper paper planes.\n\nThe formal description of this is the scientific method, roughly: you design an experiment based on an idea of what might happen, you run the experiment, look at the results and see whether your idea was right, then try and figure out what that means for your next step (and what your next experiment should be). For instance, maybe you'd theorize that the length and angle of the plane's wings make a difference, so you build a few different ones and see whether their flight behaviour is different.\n\nIn practice, this can be a lot harder, because even if you experiment with many different wings, that's not gonna help you at all if some other crucial part of the plane is missing or not close enough to correct - for example, even if your wings are perfect, if they're not actually connected to each other in some way, you won't get that plane to fly. Of course with this super-simple example it seems very obvious that they should be connected, but many things are not so simple, and then if you have a combination of elements wrong, you'll be doing a *lot* of trial-and-error until you hit on a combination that simply gets you *started*... or you'll give up long before then.\n\nEven worse, there are many topics where it's hard to even design experiments. If you wanted to understand how nuclear fission works, you can't really test any of that yourself, right? And some natural phenomena are poorly understood by scientists even today, simply because nobody has figured out how to get down and dirty with them in experiments.\n\nSo, whenever circumstances conspire against you to prevent you from any actual testing, the only other option you really have is to rely on others to know more about it than you. This is where the idea of teaching comes from - an expert on something explains it to you - either in person or through a book or video. If the explanation makes enough sense to you, it will help you understand the basics so you can maybe start researching (or even experimenting with it) yourself. So, basically, someone else has done all the hard work already and you can build on that.\n\nThe big problem with that is that, as long as you don't have a way to do your own experiments, it's impossible to tell whether the thing they're teaching you is actually *true*. You can teach sensible-sounding lies just as easily as the truth. You can see this on both sides of a conspiracy theory: the person who came up with that conspiracy theory will call the \"conventional\" teachings a lie, and come up with their own explanation that, as far as the other side is concerned, is the *actual* lie.\n\nOnce again, the only way to be absolutely sure is to experiment yourself, and you need to have a fairly decent understanding of the scientific method and experiment design (and - gasp - statistics) to actually do this in a way that doesn't throw off your results. Since this isn't always possible, there will always be things you'll be taking on good faith.\n\nHow do you deal with that? Well, it helps keeping an open mind - this means understanding that what you've learned may be slightly wrong, or even completely wrong. It *doesn't* mean jumping at the next alternative explanation someone hands you, just because it's different. You'd be just as aware that this new explanation may be slightly wrong, or even completely wrong. Then, to not get too bogged down by all the uncertainty, you just go with whatever seems most practical to you, and hope for the best, and maybe at some point you'll be able to test some of the ideas yourself, or get even more perspectives on the thing you're looking at.\n\nThat's something I like to do to avoid getting too preoccupied with a single explanation: I look for as many different sources as possible. I also try to get an understanding of the reputation of each source - if I see some random person on the internet explain it in a way that conflicts with what all the experts say, they better have *really* good arguments and, ideally, a way to actually test their claims.\n\nThere are many ways to end up with a questionable understanding without ever noticing. Like I said, there is no simple answer. I hope this is helpful anyway.\n\nIf you want to look into the general principle in more detail, look up \"critical rationalism\"." ]
Why are teeth a part of the nervous system?
[ "Simple evolution. Look at human teeth as an evolved mammalian example.\n\nHumans are omnivores and throughout human evolution meat and found plants foods such as roots have been a large part of the human diet. Biting too hard into a bone or a small rock and breaking a tooth would seriously hamper nutrition intake for any omnivorous mammal. \n\nTeeth are by necessity part of the nervous system to protect them from damage." ]
How does scar cream work (does it even work)?
[ "It doesn't. Scars are fibrous tissue where the wound closed up under the skin without the skin cells covering it. They usually fade over time because skin will regenerate over it over time but that takes a long time. \n\nCreams say they make scars \"softer, smoother and less noticeable\" which basically mean they hydrate your skin and maybe have a small amount of make up. \n\nYou could get the same results with some lotion and some make up foundation.", "There's some evidence that massage can help to reduce the size of scarring. When you break the skin, the body panics and throws down a fibrin mesh and platelets at it to seal the whole ASAP. Over time, small injuries will be replaced with normal skin, whilst larger wounds will use the original seal as a base and therefore have different-looking skin over the wound - the scar.\n\nMassage in theory helps break down the scar and encourage the body to produce normal skin instead. However, it probably only works within 8 weeks or so of the original injury and will not complete eradicate the scar.\n\nScar creams therefore DO work, but you could rub any old shit into it - it's the rubbing that is efficacious." ]
Why do carbonated drinks exclusively use CO2 and not other gases?
[ "The short answer is that CO2 is the ideal gas for carbonation.\n\nFirst of all its cheap compared to more exotic things like Helium or Neon, and isn't flammable and toxic like Hydrogen or Petroleum gases.\n\nNitrogen for example is plentiful but it doesn't dissolve in water nearly as well as CO2 so it doesn't make bubbles.\n\nOxygen on the other hand does dissolve, but it would oxidize (ruin) the product." ]
Why are some trials completed with a jury while others are not?
[ "In the US you generally don't get a criminal jury trial if the maximum punishment for your crime is less than 6 months. If its more than 6 months, you have a *choice* to get a jury trial - you can opt out if you want and people typically do when there is a strong emotional component to the trial.\n\nWhen there is a strong emotional component to a trial - ie, the defendant is accused of raping a child - its normal to opt out of a jury trial because there is a sense that juries are much more likely to convict a person in those circumstances as they're more concerned about letting a guilty predator go than putting an innocent person in jail.\n\nIn civil trials - ie you sue someone - you aren't entitled to a jury below a certain dollar value, which varies from state to state. Above that dollar value either side can request a jury, but both sides can agree to opt out of it.\n\nWith civil trials you're much more likely to see a jury trial when there is a strong emotional component because Plaintiffs believe that juries give less reasoned, larger verdicts under those circumstances.\n\nAlso, most civil \"trials\" that result from a contract don't get a court trial at all, but instead go to arbitration. Arbitration is a private court system in which the case is heard solely by an arbitrator, who is usually retired judge. However, both sides have to agree to arbitrate. \n\nIn most other countries there is no right to a jury, or if there is its substantially more limited than what exists in the US.", "In addition to what others have said here, generally, in the U.S., you are only eligible for a jury trial in a civil case if it is for a cause of action that was recognized under common law in 1781 (the year of the adoption of the Constitution). For most, of not all other causes of action, there is no right to a jury trial.\n\nFor example, let’s say you sue someone for negligence, which is a cause of action recognized under common law. You could request a jury trial. However, let’s say you want to sue a state for negligence. Under common law, governments had sovereign immunity, and that immunity was only waived, by stature, much later. There is no right to a jury trial for that cause of action.\n\nThis answer could also get into the difference in issues of law and issues of equity. Courts, for the most part, can hear either. There is at least one state, though, that still maintains separate courts of law and courts of equity.", "In addition to what others have mentioned: There is something called a “summary judgment.” A full-blown trial normally disputes a fact. (Eg. The police say Bob robbed a store, but Bob says he was playing baseball at the time.) However, in some trials the facts are not in dispute. Everyone agrees on the same version of events, we just disagree on the application or phrasing of the law." ]
What does the term "passive agressive" actually mean?
[ "Think of a situation where someone could react really aggressively, like if I responded, “this sub is a terrible place for you to ask for the definition of a single term! Why didn’t you just google the term, idiot?!” But instead of saying that outright, I convey the same level of aggression, in a toned down way, to make myself appear more civil, when I’m really being just as big of a dick. For example, “while I’d love to do your research for you, I’m sure you could find the definition of a simple term like that, even at your level of intelligence.”", "You know how normal aggressiveness usually involves shouting, swearing, shaking fists, that kind of thing, right? Passive aggressiveness is anything that doesn't have any obvious signs like that but comes from the same place. It's all about avoiding direct confrontation (which normal aggressiveness is all about) but still pushing back in less obvious ways. Acting dumb, \"forgetting\" to do things, snide comments, that kind of thing." ]
How does soap get foamy?
[ "Soap is an example of a \"surfactant\": something that lowers the surface tension between two other materials. Normally, the surface of water (with air above it, so air is the second material) likes to keep a smooth surface (there are some fun ways to play with this, e.g. you can make a pin float on water).\n\nYou can make water foamy without soap, but you need a *lot* of energy (stirring very hard/fast with something that mixes water and air, like a milk frother). The more surfactant you add (e.g. soap), the easier it becomes, because the water will care less about returning to its smooth surface. The small surfaces of the bubbles also become more elastic, so that they pop much more slowly - in normal water they'll disappear almost immediately if you stop stirring, but the soap makes them more resilient. A somewhat extreme example is foam made from shaving soap and water (and air), where you mix everything with a special brush to create some very dense foam that can last for quite some time.\n\nThere are some other elements to foaming that I don't fully understand, but that's the basic idea." ]
Why do "weeds" grow so much more quickly and without any nurturing compared to plants/crops?
[ "We have carefully selected our crops to produce large yields. This is economically costly to the plant. Plants in nature don't produce yields like that because natural selection penalises that kind of economic investment. We ensure that it is beneficial for the plant through carefully removing competitors, inputs of fertilizer and water etc. \n\nA weed, on the other hand, has survived for generations of being unnaturally selected against. All the resources that a cropped plant puts into seeds/fruits etc, the weed will put into being hardy, being resistant to herbicides or pests, being difficult to uproot (ever tried to uproot a dandelion?). \n\nWeeds aren't just better at surviving because they haven't been weakened by human selection. They are tougher because *humans have unconsciously selected them for toughness*", "We choose plants to call \"food\" because they make a lot of the fruit or seed we want to eat. Plants that don't do that are \"weeds\". However, not making those fruits/seeds takes less energy.", "\"Weeds\" are hardy things that can grow anywhere - and usually do. Crops and flowers are more delicate things, and require TLC that weeds don't. Kind of like snake babies are ready to snek around immediately after birth, but human babies need care and feeding until they are 25 or so.", "Most of the plants we want, in our yard for example, are brought from other climates or regions making then more difficult to grow especially when you're looking for the most perfect document.\n\nWeeds on the other hand will usually be growing exactly where they grow best because wherever they are is where they're adapted to. There's also no concern for wether the weed is a quality weed or an ugly one. Plus humans tend to inflate the negatives around then so weeds would psychologically be more prominent than they are wether they actually are prominent or not.\n\nAs another commenter said, they also grow super easy and fast because they don't have fruits or nuts or in many cases even flowers to use energy on growing.\n\nTLDR: Weeds are generally native to the area, grow easily and fast and psychologically stand out more since they're a nuisance.", "If you really think about it, the only difference between a weed and a plant is whether or not you want it there.", "In addition to weeds being tough (as mentioned in other comments), they are also diverse. \n\nWhen you see clover growing in one location, thistles growing in a second, and quackgrass growing in a third, you call it \"weeds growing everywhere\", when each species actually has a (somewhat) restricted habitat.", "Fun fact: a lot of what we consider weeds are actually edible and high in various nutrients. The downside is that they usually outcompete other crops." ]
The Vagus Nerve; what exactly is it?
[ "The vagus nerve is a cranial nerve that runs from your brain, down into your chest and into your abdomen. It is a purely parasympathetic nerve, which means it can slow things down, like your heart rate, breathing and or help things along that happen best when you are relaxed, like gastric movement. People sometimes have it stimulated quickly and out of context, which can cause them to open their bowels (uncontrollably), drop their heart rate, which in turns drops their blood pressure and can cause them to faint. This quickly passes (seconds to minutes), and lying them down helps a lot. In terms of a ‘wellness’ nerve, the nerve is parasympathetic which is known as the “rest and digest” system, which might be where that comes from. However, the nerve is just a thing that our body utilises to help regulate things and keep us moving and pooping.", "Vagus nerve is one of 12 nerves that exits from the brain stem. It has many functions: It provides sensation to your throat area (on the inside) and is responsible for the gag reflex. It innervates your vocal cords. It innervates your lungs to constrict it and it innervates your heart to slow it down. It innervates your stomach and intestines to make em move food along. It also controls like 2/3rds of the large intestine to push food along there as well. \n\nAs you can tell, this is the major rest and digest nerve." ]
Does using internet on a flight really affect the plane’s instruments?
[ "The short answer is that it's possible, so don't.\n\nThe Mythbusters did an episode on this. What they found was older electronics had more of an effect than the newers ones.\n\nAlso that most modern airliners have shielding on the instrumentation to help protect them against this sort of thing. But on smaller and older planes there was a significant affect on the instrumentation.\n\nAirliners are tightly regulated for your safety, so when they say turn your phone off do it! Better safe in the air than not." ]
What is the difference between different educational degrees (MBA, GED, PhD, MD, doctorate, master’s, etc)
[ "MBA is a masters in bussiness administration\n\nGED shows that you have high school equivalent competence\n\nPhD is a doctorate in a subject, MD is a doctorate specific to medicine\n\nTypes of degrees one can get after high school are: Associates, bachelors, masters, doctorate. Each succesive degree requires additional schooling. Associates is usually two years, then 2 more for bachelors, then 1-2 more for masters. After that MD is 4 years, PhDs are often 5-7 years. Although MD doesnt require masters and PhDs often include a masters in those 5-7 years. Most engineers stop at bachelors, most computer science and bussiness people stop at Masters. The only reason you would do more schooling is to get a better paying job because you know more." ]
A tree can contain hundreds or thousand pounds of wood, Where all this come from ? Does it come from the ground ?
[ "It comes from the air! Plants use CO2 from the air to make things (photosynthesis), wood is 90% carbon and oxygen.", "Trees and other plants contains large amounts of carbon. They take up CO2 from the atmosphere through their leaves and break it up into carbon (C) and oxigen (O2) in a process callled photosynthesis.\n\n**Interesting fact:** There was a man from Belgium called Helmont who in the 1630's made an interesting experiment to figure out if what makes a tree grow comes from the soil itself. He put a willow (of known weight) into a pot of soil (also of known weight) and watered it for a few years. Then he took it out, and weighed both the soil and the tree. The tree had gained in weight, but the soil was more or less the same. Therefore, the stuff that made the wood had to come from somewhere else than the soil (i.e. the air).\n\nHere's a short [article](_URL_0_) and a [documentary](_URL_1_)." ]
What do the authorities do with the money that is found from high end drug dealers?
[ "What on earth makes you think that asset forfeiture only applies to \"high end drug dealers\"? There are cases where people have had [their homes seized after being caught selling $40 worth of drugs](_URL_4_), or because a visitor was caught with possession of small amounts of drugs.\n\nIn the USA, civil forfeiture laws allow the police to seize assets on suspicion of a crime, the victim doesn't need to be found guilty or even charged with any crime. This is literally legalised theft, since the police can, and do, simply say that they \"suspected\" the money or property was the result of drug crime, and the victim has to prove that it wasn't.\n\nThe authorities do whatever they want, since they write the laws. Some of them use it to fund the police, some of them use it as part of general revenue, some of them use it to buy [expensive and unnecessary military equipment](_URL_2_), buy sports cars, fund holidays in Hawaii, and even pay for slushy machines. I'm not kidding or exaggerating.\n\nSome of them give the money to prosecutors and police as a personal bonus. So before you ask questions about \"the authorities\", you need to specify which ones.\n\nIn the US, civil forfeiture is a lucrative money-making scam worth [literally billions of dollars](_URL_0_), and more than 80% of people whose assets are legally stolen are never charged with a crime, and most of the rest are charged with only minor offenses. In some places, the same people who receive the seized property get to decide whether or not it was \"drug related\". Remember, the victim of this legalised theft doesn't need to be found guilty or even charged with any crime, and most of them aren't. The police just need to say they suspect that it might have been the proceeds of drug crime.\n\nMore here:\n\n_URL_1_\n\n_URL_3_" ]
Time and where it stops.
[ "You understand time crossing times zones doesn't mean you are traveling through time right? Like, if you take a 6 hour flight eastward that crosses 6 times zones, you didn't travel 6 extra hours into the future, and if you take a 6 hour flight westward that crosses 6 time zones, you didn't go back in time 6 hours, it's just that the local time is different. You still spent 6 hours in the plane regardless of how many time zones you crossed or the difference in time between your place of origin and your destination. It's not future and past. It's always the present but just a different time at different places. That's how time zones work.\n\nAnway, the line you're referring to is the [international date line](_URL_0_), which runs through the middle of the Pacific Ocean. The International Date Line runs down the middle of the Pacific Ocean. If you cross the date line moving east, you subtract a day, whereas if you are moving west you add a day. For example, if today is Friday and we crossed the International Date line from west to east then it would be Thursday. If we went east to west it would be Saturday.", "The international date line is the \"earliest\" place a new day is accepted to start. If you cross it, you enter a different date.", "If your really confused about it, think about every time zone as plus or minus hours from utc time." ]
If the human body is constantly seeking homeostasis, and our ideal body temperature is near 98.6 Fahrenheit, why do most of us prefer external temperatures that are 20-30 degrees cooler?
[ "Because the human body generates a lot of heat so in order to maintain homeostasis it needs to be able to shed excess heat, a high external temperature make it difficult to shed this extra heat. - _URL_0_", "Your body produces heat. If the temperature of the air is the ideal body temperature, that would be the temperature of the outermost layer of skin (ideally). The body internally would heat up beyond that.\n\nAlso, the ideal body temperature is 37 Celcius.", "Because our body is constantly producing heat and is trying to maintain homeostasis. This means it has to dump the excess heat into the air and it does so most efficiently at around 70F. Go 10+ degrees lower and you start losing heat too rapidly so need to wear protective layers, go 10+ degrees warmer and you start to have difficulty dumping the heat into the air around you and you begin to sweat." ]
Can a body that currently needs 7-8 hrs of sleep get used to 6hrs of regular sleep?
[ "Yes. All you need to have are fixed times for sleeping. Get up every day, even weekends and holidays, at the same time. If you are still tired the first week that shouldn't be surprising. If you still are overly tired after a month, improve your overall sleep quality. For example get better pillows or sleep in a room without electronics whatsoever. I'm currently in a 5 1/2 h sleep schedule. And I feel a lot more rested then back in the day when I was sleeping 8+ hours", "Yes but it's really not good for you. You will notice consistent low energy levels. Low mood and also a short temper. I think it's about 4-5 hours minimum that you can get and function semi-normal. On a regular basis that is.", "Used to: yes. Work as well as with it's required amount of sleep: no.\n\nAt day time, your brain has to sort through a lot of new impressions and experiences and stores all that. When you sleep, your brain does maintenance work to sort through all this and to decide what to keep and what to toss. Some brains have a lot of maintenance workers who also work really fast, someone else's also work fast, but there are less. And then there are brains where much more time is needed to clean up. The fastest maintenance workers have their task completed in four hours. Those are very rare. The majority of brains have the workers sweep through all the alleys and corners in about eight hours. And some even need nine to ten to complete their task. \n\nWhen the owner of that brain is still growing, there is more to sort through from the day, and the maintenance is less experienced, so it might take even longer than that and over age, they might need less time. So your best amount of sleep varies over age. If you get less than that amount of sleep, the stuff just piles on and on and the workers cannot finish their job. The next day, you might feel groggy, this is because there is still stuff not collected in the streets and your daytime workers need to climb around that stuff. You will also notice that the workers did not have time to store away all your newly learned information, and this is why you are more forgetful.\n\nYou can find out the natural amount of time your brain's cleaning force needs by going to bed when tired, sleeping and waking up without an alarm clock over a few days. \n\nYour workers also work in shifts, called REM phases. Those phases last about 90 minutes and your body wakes up easiest between shifts. So if you often feel tired, you might be waking up inmidst of an ongoing shift. If your brain cannot concentrate solely on being cleaned, because for example, there is noise going on or light shining into your room, the workers become less efficient even interrupt their shifts, all leading to being more tired.\n\nYou cannot train your workers to \"be more\" or faster. You just have to work with what you've got, but understanding the work that is being done and how your body does it can help you feeling more refreshed in the same amount of time.", "Yes. It’s not entirely accurate to say that one needs 7-8 hours of sleep, except during adolescence when the brain is still developing. When one reaches adulthood (21+) the what matters more than quantity of sleep is quality of sleep. An average, healthy adult need only 5-6 hours of good quality sleep (deep REM sleep) each night. This would be better than 7-8 hours of average sleep. After a week or so of 6 hours a night, especially if one keeps a consistent schedule for sleep, one’s body will adjust naturally. Ask anyone who’s worked a 2nd job overnight or early morning; it still sucks to get less sleep but if the quality is good, you’re fine.", "The human body is very good at adapting. So it's entirely possible you could function on less sleep than is stated as ideal. \n\nSome people need less sleep as they get older and there's a ton of factors that should be considered such as diet, lifestyle and environment." ]
Why do towels absorb water?
[ "Water likes to stick to some things more than others. The amount of water that sticks to something is determined mainly by three factors: How much it wants to stick to that thing, the amount of surface area of that thing, and the amount that water wants to stick to the other thing (in the case of a beach towel, the other thing is you). Water is rather attracted to most things, including towel fibers. Towels have a lot of surface area due to their shaggy and fibrous nature, leading to them being able to attract and hold a lot of water." ]