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7belj4 | If We control our brains, and our brains control our bodies. Why can't we control our bodies? | Repost | explainlikeimfive | {
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"Because it is not useful to be able to manually control the beating of your heart. You always need your heart beating, so it is more efficient to just do it constantly, without conscious thought. Devoting a part of your brain to modifying the heart's behaviour manually would have been a waste of resources. Contrast this to breath control. Being able to not breathe in at a specific time *is* incredibly useful, for a creature that is unable to breathe in liquids but who sometimes finds themselves underwater. Being able to hold your breath is immensely useful, and mammals have acquired this adaptive trait long, long ago. And of course it still isn't 100% voluntary even if you try to assume direct control. Even if I say \"You are now manually breathing\" you can't just choose to stop breathing altogether - your body automatically starts breathing again before (or as) you pass out from lack of air."
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7bid2l | In the age of Google, why does this subreddit exist? | Repost | explainlikeimfive | {
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"The purpose of this sub is to provide simple explanations for things that may be too complex or otherwise difficult to wrap your mind around if you only relied on Google results. But sadly, many questions are posted with easily googleable answers but people are just lazy and want someone to tell them the answer.",
"Googling is a skill, and you have to know how to find what you're looking for. Out here, people know how to phrase things directly, instead of making you look for an answer. Even then, an answer that at least *seems* right. Ever wonder why people in IT can fix computer issues easily? They are adept googlers. They know what to look for.",
"depends. Sometimes it can take a while to find answers that make sense to you. I spend a lot of time in wikipedia-black holes of time. Some of the math/physics entries are bogged down with a lot of exacting tecno-talk and math equations. I often find myself dusting off parts of my brain that haven't been exercised in a while. I enjoy that stuff.....but not everyone wants to spend an hour trying to remember some terminology they learned many years ago just to answer a simple question. And trying to get a simple answer (that you trust) on some topics can be hard. Is global warming a hoax? Google it..... just try it - i did.....Donald Trump's twitter account came in the 2nd spot.... With the \"top 10\" that came up for you in your google search....do you now trust google to give you \"accurate\" information? or just the top 10 places they found the internet reading about that topic so they can sell targeted adds to your cookie tracked demographics.... now try URL_0 are your results different? yahoo? bing? screw it....ask reddit."
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7bio0v | Why does the moon sometimes look much bigger on some nights than on other? | Repost | explainlikeimfive | {
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"[It's an optical illusion.]( URL_0 ) This happens when the moon is near the horizon and you can see other things in the same field of vision. But when it's overhead it doesn't look as large.",
"There are two elements to this. * Perspective. When nearer the ground, you have a fixed point of reference relative to the moons size. By which I mean you have mountains, trees or buildings directly up against the moon in your vision which let you easily get a feel for its size. This makes it look a lot larger than it does when right up in the sky surrounded by nothing but black night sky. * The Moon's orbit (Supermoon) The moon doesn't orbit around the Earth in a perfect circle, it orbits in a slightly flattened circle, and the Earth isn't in the centre of that orbit anyway, not quite. Have a look at [this]( URL_0 ) image to see what I mean. There is a point where the Moon is closer to the Earth than it is anywhere else in its orbit, called the 'Perigee' on that map, and at that point the Moon will look up to 30% brighter, and almost 15% larger than it normally does. If you have a Supermoon situation combined with the moon being low towards the horizon, it'll look unusually huge compared to normal."
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7bjyki | Why did peppermint become the standard flavour for toothpaste and other things like that? | Repost | explainlikeimfive | {
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"A lot of reasons make it and its nearby variations like wintergreen or spearmint into popular flavourings in toothpaste and other breath-fresheners like gum or mints. In its earlier days, peppermint oil was easy to extract from natural easily-grown sources. It's associated with freshness. We've known about it for a very long time due to its ability to make a nice herbal tea, so when searching for something that would mask the chalkiness of otherwise-unflavoured toothpastes it was a natural hit. Its smell is associated with freshness and is excellent at masking or washing away the type of smells you get from not-quite-perfect oral hygiene, which is why it finds its way into a lot of desserts or dishes served as sides to strong food (e.g. yogourt-based sauces). And the \"cooling effect\" of the oil, which you can really feel if you get a massage involving it, makes your mouth feel cleaner than otherwise. Other flavourings such as clove oil, anise or cinnamon also work, but they're often stronger or unpleasant to more people so they're not as popular everywhere.",
"As a side note, peppermint has historically been used as a treatment for abdominal/digestive issues. I wouldn't doubt that was considered."
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7bkpkg | What makes spicy foods spicy? | Repost | explainlikeimfive | {
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"In most spicy foods, there is a chemical called Capsaicin, which is responsible for the spicy heat that comes off foods. It works in two ways: the first, is that it irritates, causing a slight pain sensation that activates nerves that otherwise aren't activated. The second is that it effects the temperature receptors on the tongue, TRPV1 (short for Transient Receptor Potential Vanilloid 1). It makes these receptors more sensitive to heat, essentially lowering the threshold that makes them send a signal to the brain indicating the mouth is \"hot.\" It's actually your own ambient mouth temperature that causes the heat, the Capsaicin just made the receptors more sensitive."
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7bkyv7 | body fat sensors on scales...how are they supposed to work? | Repost | explainlikeimfive | {
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"You enter your height and it knows your weight so it calculates your body mass index (BMI) to give you the inaccurate number that the BMI represents.",
"Usually bio-impedence. It passes a current through your body up one leg and down the other. From this it can measure the resistance of your body. As fat contains less water than fat the higher your body fat the higher the resistance. It uses this along with your weight and height to give a very rough estimate of body fat%. Note however that things like what you have eaten that day and how hydrated you our can cause big changes in the reading.",
"They measure the impedance of your body - URL_0"
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7bl529 | how cd disks store data | Repost | explainlikeimfive | {
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"It is an easier answer than you would think. CDs work exactly like records with two differences. 1) instead of translating waves they only have to care about an up or down position. 2) instead of a physical needle they use a laser. They are literally a long line of up and down positions (ones and zeros) that are wound in to a great big circle like a record with grooves so small you can’t see."
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7blm0n | Why is it that sitting for extended periods can cause blood clots but laying down sleeping for 6-8 hours a night doesn’t? | Repost | explainlikeimfive | {
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"When you sleep your blood does not have to flow upwards, your body is mostly straight and you are still moving alot in sleep. So If your leg is broken and you can't move a little your chance developing cloths is higher. That's why they give you shots in hospital every day. While sitting the legs aren't moved much, they are angled and the blood have to flow upwards.",
"In sitting your blood has to work against gravity to go back up. In lying everything is the same level and doesn’t have to work as hard to go to your feet and back. An extra fun fact: clots in your calves can go to your lungs and kill you that’s why it is important to prevent them",
"This is called a deep vein thrombosis and its more common after surgery, during travel, and in people who are at greater risk for it due to blood conditions and platelet count. The changes undergone in the body after having surgery can increase clotting and the chances of having a clot. This is made more likely by being more sedentary when recovering due to pain and mobility so it's important that people get up and walk at set schedules, even if it hurts. Patients are often given heparin injections to thin the blood after surgery, even going so far as to have patients self inject for days after being released from the hospital. Sitting for long periods isn't great for the body, but under normal conditions it isn't that bad. However when traveling for long periods of time, crammed into small and uncomfortable airline, train, or bus, seats, coupled with the seating position, circulation problems from seat design, and that at many times people are discouraged from getting out of their seat, people are more likely to develop them. Blood also tends to pool in the lower extremities when seated for long periods. Imagine a 20 hour flight to Australia in coach, where you can only get up and move around sparingly due to tightly packed seats. Outside of restroom breaks you might not get up at all. Laying down in bed doesn't put so much pressure on the thighs and cause blood to pool in the legs. It also doesn't affect circulation in any negative way unlike sitting. Standing still causes blood to pool in the lower limbs, however the action of walking helps with circulation and the muscle movements and motion help stimulate blood flow.",
"To answer this, we should first take a look first at the circulatory system’s method of flow. The blood comes out of the heart and into the aorta and arterial system. The arteries are much thicker because of their more robust tunica media layer. That’s basically a smooth muscle layer that handles the high pressure, and in the case of the arterioles (medium sized arteries), it changes tone to effect your blood pressure. Once the blood goes through the capillary level (where it moves more slowly to accommodate oxygen, CO2, and metabolite diffusion), it goes into the venous system to make its journey back to the heart and lungs. ***CUE Part where DVTs (deep vein thromboses) happen The venous system is composed of very floppy vessels with valves to help prevent backflow of blood. It has a much thinner tunica media and it depends on the contraction of skeletal muscle (the voluntary muscles you use to walk) near it to help with blood flow when flow fights gravity (returns to the heart). If blood isn’t moving fast enough, the clotting mechanisms kick in and you get a thrombus (fancy pants word for clot). When you’re sleeping, your legs are more or less at the phlebostatic axis (on a horizontal plane with your heart), meaning return flow is *much* easier because you aren’t fighting gravity to get that blood back up to the heart. When you sleep, your body moves a tiny bit to keep venous return flow going, but the gravity is your most influential variable. With the gravity being alleviated, you aren’t usually laying down long enough to make a difference. If you’re down for more than a day or two, we start to treat it a bit. *In the hospital, we use some anticoagulants (anti-clot meds) and powered compression devices to simulate skeletal muscle contraction. This is mostly because people are in bed for days at a time without a lot of motion while recovering. The tops of the beds also tilt up, so gravity makes an appearance again. This is why nurses put pillows under the knees or slightly elevate the legs (some nicer beds can do this) so the hips are the lowest part of the body (not with a straight knee as that actually inhibits flow as well—I’ll get into that at the bottom). Minimizing the effects of gravity helps the venous circulation even more than the compression machines by themselves. Quadriplegic people bound to wheelchairs often have tilt chairs because they get almost no skeletal muscle activity in their whole body. **Answer time/ TL;DR** When you’re sitting for prolonged periods, your skeletal muscle activity is low, but because you’re flighting gravity, your blood has a tendency to push into the venous walls and expand them (remember they’re floppy), causing a decrease in flow velocity due to a widened vessel. It’s like taking the sprayer nozzle off a garden hose. The change in diameter causes an inverse change with regards to flow even though the same amount of fluid is going through. When the blood is allowed to slow down like this, it causes an increased risk of clot. You may be wondering why a clot is so bad. It can break away and float to your lung, causing a Pulmonary Embolus (PE) and killing part of your lung. It could float to your brain and give you a massive stroke. It could also block your coronary circulation and give you a heart attack. All three of those can kill you. Getting up frequently on flights helps decrease the risk for clots. Couple that with compression socks/sleeves/tights (the leg is more at risk than the thigh and is the more important part for compression), and that usually reduces the risk of clot formation *dramatically*. Also to note, compression shorts aren’t a good idea because they prevent a backflow as the blood goes from the uncompressed leg to the compressed thigh. Distal is more important, so the compression should be greater there and should decrease as it gets more proximal to your body (distal = further from heart, proximal = closer). If you have clotting disorders, consult your physician before flying. If you’re on birth control or pregnant, it’s a good idea to get your PTT/INR checked regularly (clotting factors). This is purely educational and not a substitute for medical advice. *As promised: the straight knees thing! Straight knees actually cause the veins to bend a tight (but small) turn. Think of it as a kink in the garden hose that causes resistance in the vessel. When people pass out from standing with straight legs, this is why.* Hope this helped! I love physiology! Let me know if you have questions! Again, this is just for educational purposes. Please excuse any typos/autocorrects. I did this on my mobile. Edit: Yay Gold!!! Thank you so much kind stranger!!!! I’m stoked to figure out what it does 😁",
"I have a followup ELI5 - When people wear the compression socks to help with circulation, how does it not just cut off or restrict blood circulation to the feet? Are compression sleeves a good thing to wear in general if you sit for long periods of time? Does it actually help?",
"Sitting is not a \"natural\" position - we haven't been doing it for very long in evolutionary terms, so it can cause problems due to how our bodies are shaped. For most of human history, and still in very poor and ancient cultures, people would squat instead of sitting. We evolved buttocks because they store fat to burn when walking or running, not for padding to sit on. Lying down, however, *is* a natural posture for us that doesn't interfere as much with circulation.",
"How do people who are chronically confined to a wheelchair deal with this?",
"Well laying down for an extended period will eventually also lead to thrombosis. However sleeping usually does not trigger thrombosis because: 1. While you are sleeping you still sometimes move your legs, activating your muscle pumps and reducing the risk of thrombosis. 2. Blood does not have to flow upwards like in a supine position. And thrombosis after sitting for extended periods of time is usually in tight spaces (e.g. planes), where the veins are additionally compressed externally - this is also known as “economy class syndrome”.",
"See, I'm a hemophiliac, which means my blood is super shitty at clotting. That means I actually have an advantage when it comes to any task or activity that is sedentary for long periods of time! Can't build up a deadly blood clot if I can't can't clot to begin with! That pretty much makes me the Ubermensch of any office setting. I'm just going to sit here and smile at my screen smugly knowing that there's nothing anyone can say at this point to deliver any sort of come-uppance.",
"It can? Maybe happens less Often but thé Point being is that you need to move to lower it's risk. If you wake up, site for 8 hours and go to bed again you higher thé risk. Maybe also because blood lowers to the legs when sitting. More blood there with less pressure on it. Cloths can form more easily?",
"Neglecting the aspects of moving and such that everyone else is mentioning, Here's a basic principle. Pressure = Force/Area. The more area you have, the less force that area is subject to. Bloodclots are caused when the pressure forces the blood vessels closed, or prevent flow of blood. When you are sitting, the pressure(on just your butt area) on such a small area prevent blood from moving and therefore, you end up with blood clots. When you are sleeping, the pressure is distributed much more evenly. (more surface area, Your back, legs, head, etc.) Now to the sciency mathy parts. rounded to really nice even numbers just because i'm lazy, but its close enough. If you divide you butt are by weight. That comes out to the pressure you exert on the are. It averages out to something like 15mm hg (there's math behind this and i'm pulling number out of my butt.. literally :P ) Now we all know that flow needs a pressure difference in order to move. (gravity, pressure, concentration, etc) The pressure difference between the arteries and the venous system is just about 10 mmhg. So.. when you sit down, you exert 15 mmhg of additional pressure prevent blood flow to leave an area, and that's why you end up with blood clots. When sleeping, the area is more distributed, the pressure less, and less blood clots. Onto the Yes i know.. but what about... Bedsores. (yes.. certain areas carry more weight. If you don't end up moving, blood clots and flow issues. The LEGS MAN, What about the legs!!!! Her legs, and right where her legs meet her back. That - actually that whole area. That and - and above it. Gravity. Yes.. Gravity plays a part. Reminds me of a story...",
"Sitting doesn't cause blood clots by itself. The danger of a pulmonary embolism is when someone has an injury like a torn calf muscle and they go on say a long plane flight, a blood clot could grow larger than usual because of lack of movement and then break free, travelling to the heart and stopping blood flow causing a heart attack. Normally the blood clot never gets that big because with regular movement smaller bits will break free and get absorbed by the body. At least that's how it was explained to me by a doctor that was an expert witness in a legal case where I had to design the visual representation (animation and stills) for the jury. Dude was suing his doctor because he flew to Australia with a tennis injury and almost died because of a pulmonary embolism. Said his doctor didn't properly warn him to get up and walk around every so often to keep the blood clot from getting too big. Don't recall if he won or not, but that's why they say to get up and walk around on long flights, in case you have an injury that could cause a clot to grow while sitting for long periods. I have no idea if this is a danger while sleeping too, but I would think that with normal sleep movement it wouldn't be an issue since you're constantly changing positions while asleep.",
"Physiologist here: Blood tends to clot when it stagnates (i.e. isn't flowing very fast). Your heart pumps blood from it to the rest of the body under high pressure in arteries. By the time the blood reaches the distant parts of your body (e.g. fingers, toes) and passes through the capillary bed (small network of blood vessels that connect arteries and veins), there is very little blood pressure remaining - not enough, for example, to move blood from the feet to the heart when the blood is working against gravity (when you are standing or seated). Blood is mostly water (it's heavy) and it takes quite a bit of pressure to move it from your feet to your heart when you are sitting or standing - as your heart is located at least a meter or more above your feet. To help move blood back to the heart when you are sitting/standing, your veins have one-way valves in them. Muscles surrounding these veins contract, squeeze the vein, and the one-way valve ensures that blood in the vein only moves towards the heart. When you are normally sitting or standing, periodically moving your legs causes your leg muscles to contract, squeeze veins that run through/near them and help to pump blood back to the heart. When you're seated , your leg muscles are normally relaxed. Those leg muscles, therefore, aren't frequently contracting and relaxing as when you are standing/walking and shifting your feet; they aren't pumping a lot of blood back to the heart. Blood tends to pool in your feet/lower legs, and this can cause blood clots to form. When you're sleeping, you typically are lying down. Blood in your lower extremities is typically only a few centimeters lower than your heart. It doesn't, therefore, take much energy to get that blood back to the heart. The small amount of pressure in your veins is typically sufficient to push the blood from your lower extremities to your heart when you are lying down.",
"Is sitting down cross legged just as bad as sifting down normally?"
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7bo00y | If babies can't provide feedback to eye doctors, how do eye doctors know what type of specs to give them? | Repost | explainlikeimfive | {
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"They scan the retina through a machine. Since you have to look through the eyes lens to see the retina, that also gives plenty of information about the lens's properties. This works fine for adults too, and they'll often do it to get a ballpark estimation before you start trying different lenses. The thing is, adults are a bit more picky than a baby, and if something is a tiny bit out of focus it's gonna be annoying. The machine can't quite detect these small imperfections, and sometimes its just down to personal taste, so it's best to let people decide for themselves what looks best. Babies don't really care about these small differences.",
"I had this question, too. The eye doctor told me the instruments they use are able to tell what prescription a baby would require.",
"There is a family of \"automatic\" prescription checking machines. Most of them work on the same principle, you look at a high contrast panorama image, like a deeply colored hot air balloon in a light blue sky. The machine that projects the image also contains a camera that looks through the optics to sense the image on the back of your eyeball. The optics are varied, under computer control, changing their focus until the sensor detects a sharply formed image on the back of your eyeball. This optics adjustment measures the correction needed to make your eye focus at distance. Since children's eyes work the same way, they don't need to \"participate\"."
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7bq195 | Why do you get nauseous when you read in a car? | Repost | explainlikeimfive | {
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"Your brain doesn't like the discrepancy between what your eyes see and what your body feels. You have an organ in each ear that senses changes in acceleration. When you go around a corner in a car, you body senses this but if you're just looking at a book in the car, your eyes don't see this corner. According to your eyes, you're not in motion. Your brain can't account for both and it gets confused, making you nauseous. It's far less likely to happen on planes boats and trains since they mostly travel in straight lines."
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7bsjjb | Why are players from South Korea so dominant in video games? | Repost | explainlikeimfive | {
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"Not especially MOBAs. They dominate Starcraft BW and Starcraft II. They basically dominate any games they start investing real time on. They currently dominate what, SC, LoL, OW (the games I know of). I think it's mostly cultural. Asians = > Work hard, for yourself, your family + with all that eSport knowledge and background they have solid infrastructure around players.",
"There are many reasons: - the country is small but densely populated. Servers placed in Seoul can often provide players with pings < 10ms - essentially the same as in a LAN. For MOBAs this means that pro players get to practice EVERY DAY in the very environment they will play on stage in tournaments. At this level of play, having a ping of 50 or even 80 (which are common for many servers in EU or the US) is essentially like playing a different game. This makes their practice for tournaments less efficient. - Esports (competitive video games) have a long tradition in Korea. Because of that, they are much more accepted and viewed as \"legitimate\". People can actually envision having a career in the field. While in most other countries it is still viewed as a hobby and even pro players always have to keep their future in mind. - Because of that long tradition, Korea also has way more experience when it comes to training, coaching, etc. - for some reason Koreans are much more likely to play this kind of video game. Take League of Legends, the \"tiny\" Korea has roughly the same playerbase in that game as the much larger US and is comparable even to the entire EU. To summarize: - you have a huge pool of potentials - the environment/working conditions are better than in pretty much any other region - you have experienced coaches & infrastructure - \"soft skills\" like the fabled work ethics and more importantly the willingness to listen to elders (coaches) compared to many western players."
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7bsk8j | How does Google Maps navigation provide information regarding traffic, accidents etc. so fast and accurately? | Repost | explainlikeimfive | {
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"You might know that google is one of the driving forces behind the Android system for smartphones. They have all their services installed, and many people use those services including stuff like location based services. Now for that kind of service requires as you might guess, the current location of that person. One persons data can be used mostly for services for that one person, but google has access to many data points. Now imagine the google server sees 300 people traveling on a highway at normal speed. Well then you can already start doing some calculations with other informations you might know, like the average amount of android devices in an area to interpolate how much traffic there is. And then, those 300 data points suddenly all slow down while on the highway. There aren't that many possiblities why this could happen. If they speed up after a certain point, you can also start to pinpoint where the problem is. You can opt-out of those types of data-gathering, but many choose not to for one reason or another. Aslong as enough people send their data, they can use that data to calculate all sorts of useful stuff.",
"Google maps has access to data from every user of Google maps, Waze, and Android in addition to traffic reports put out by various agencies. That’s a lot of real-time data showing location, speed, traffic density."
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7bt08p | How do we get vitamin D from the sun? There's no vitamins in light so how does it work? | Repost | explainlikeimfive | {
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"The majority of animals produce Vitamin D (actually a group of compounds known as secosteroids) through photosynthesis, meaning synthesis through light exposure. The human body requires Vitamin D3 and D2 primarily. The precursor to Vitamin D3 is called 7-dehydrocholesterol, which the body can make on its own - when that chemical is exposed to sunlight, specifically UV light, in the skin, it undergoes photosynthesis to produce Vitamin D3."
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7bved3 | How auto-dimming rearview mirrors work | Repost | explainlikeimfive | {
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"Yarr! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: how do auto-dimming rearview mirrors work? ]( URL_0 ) 1. [ELI5: how do autodimming mirrors work? ]( URL_1 )"
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7bvpb9 | How is the sun able to burn for millions(?) of years? | Repost | explainlikeimfive | {
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"The sun doesn't burn it fuses atoms to release energy. At high enough pressure, like in the center of a star, two Hydrogen nuclei get squeezed into one to make a Helium nuclei. When this happens a small amount of matter is lost and turns into an enormous amount of energy (Einstein's equation Energy= mass times the speed of light^2). There is enough hydrogen fuel in the sun to keep it fusing for about 9 billion years.",
"The Sun burns about 6x10^(11) kgs of hydrogen every second. Luckily, the Sun has about 1.45x10^(30) kgs of hydrogen to burn. Thus, the Sun has enough hydrogen to live for about 2.4x10^(18) seconds, or about 76 billion years. Of course, the majority of that hydrogen will not be burned before the Sun dies, but the point is that compared to the size of the Sun, the amount of hydrogen burnt is minuscule. If you remove 6 L/sec from the world's oceans (The Amazon River discharges about 200 ML/sec), you'll be emptying the oceans at nearly the same rate that the sun is burning through its hydrogen reserves."
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7bxkwp | Why does using a scissor to put pressure along a ribbon cause it to curl up? | Repost | explainlikeimfive | {
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"dpll3ez"
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"text": [
"You actually cause an asymmetrical stretching of the material- The far side of the ribbon is being stretched more than the facing side, so it bends. URL_0"
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"https://www.scientificamerican.com/article/secret-of-ribbon-curling/"
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|
7c13zz | Why do we swing our arms back and forth as we walk? | Repost | explainlikeimfive | {
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"text": [
"Your arms naturally swing when walking. Not swinging your arms when walking engages your muscles and might not be as comfortable.",
"Because it balances our body to keep walking straight Here is a great article on wiki: URL_0"
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7c1oyt | Why does everything seem more quiet when it snows? | Repost | explainlikeimfive | {
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"Snow is a \"soft\" substance. It does not reflect sound waves well. When the sound vibrates the outer layer of the snow, the air pockets and the general weakness of a snow flake means that much of the energy is absorbed by deforming the snowflake. Since the sound you hear is the sum of the sound that comes directly to you and the sound that is reflected to you, covering the outside with a sound-absorbing substance greatly reduces the sound reflected to you.",
"Snowflakes have open space in their structure acting as a sound buffer. This reduces noise. Sound travels in waves and needs to vibrate the molecules in the solids, liquids or gasses to be transmitted. Sounds also travel faster in warmer conditions, so air temperature helps to slow down or speed up the waves, changing what is heard. If there are objects in the way, sound can be dampened, reducing what is heard. Snowflakes do just that! As snow begins to melt and change shape, sounds change yet again. When snow melts, the space in between each crystal is reduced as well as the buffering property, and the silence of a fresh snow goes away. In fact, as snow turns into ice, it can actually make sounds louder because it will reflect sound waves instead of absorbing them.",
"Snow contains a lot of air cavities, these trap sound waves and prevent some of the reflection. If you've seen those quiet rooms with foam cones on the walls, snow kind of operates in a similar manner."
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7c6qi0 | Why do paper towels become more transparent when they are wet? | Repost | explainlikeimfive | {
"a_id": [
"dpnnnyq"
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"text": [
"Refractive index matching. Paper is made up of cellulose fibers and air pockets. Air and cellulose have very different refractive indices, and light trends to scatter each time it encounters a refractive index change. Water is much closer in index to paper, so there is less scattering."
],
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|
7c8qrs | The financial crisis of 2008 | Repost | explainlikeimfive | {
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"text": [
"Disclaimer: I'm taking all of this straight out of The Big Short. It's worth watching - great movie and it's basically an ELI5 itself. Basically, there's a form of security that's, well, secured by mortgages. It's been around for decades, and basically consists of a bunch of mortgages bundled together. The reasoning is that everybody pays their mortgage, so it's \"safe\" to bet on it. But there's only so many homes in the world, and only so many mortgages to bundle together into mortgage-backed securities. They had previously only included mortgages from trustworthy people who had good credit, but now they've run out of those people. So, these mortgage-backed securities started including B rated loans, meaning less trustworthy people who might not pay them back. Some people got smart and realized this, and they started betting against the market. They assumed when the securities started consisting of mostly subprime mortgages, the bubble would burst. But that didn't happen at first, because the loans were still rated highly. Basically, the companies that accredit the mortgages were getting bribed/extorted by investment banks to issue A ratings for loans that were, frankly, crappy. We're talking stripper-in-miami-with-five-mortgages-takes-out-a-loan-to-buy-another-house kind of crappy. This kept things going for a while, but eventually these people were unable to pay back their mortgages and defaulted, and that's what caused the collapse."
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7c8wll | How do windmills work? | Repost | explainlikeimfive | {
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"text": [
"Windmills are giant mechanical 'pestle and mortar' devices. Wind pushes the rotors, which are angled, meaning the wind forces them to spin. The spinning rotors are connected to a series of gears, eventually leading to a giant 'pestle and mortar' type device. The giant 'pestle and mortar' device grinds with great force, allowing for the easy production of flour and other commodities."
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7cbe3j | Why do our Stomachs Rumble? | Repost | explainlikeimfive | {
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"text": [
"Fluids and gasses are moving about in a really foldy tube which contracts to move things around. It's pure mechanical noise of the process.",
"It's called peristalsis. Your intestines/stomach do this to move food through your digestive system. The rumbling happens because peristalsis occurs periodically even when there's no food in you, to make sure your stomach was totally emptied whenever you might eat something"
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7cd5g1 | . Why does alcohol make you pee? | Repost | explainlikeimfive | {
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"ADH (a hormone) is made by the hypothalamus (part of the brain) and stored in the kidneys. It tells the kidneys how much water to absorb. Alcohol inhibits ADH. Instead of the water being absorbed it goes to the bladder which makes you pee more often."
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7cdx53 | Why do some noises (like nails on a chalkboard) make us cringe? | Repost | explainlikeimfive | {
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"Best answer I have is the variation of the different frequencies you create when you scrape a plate/chalkboard, crush styrofoam, etc. It can trigger the unpleasant feeling for humans. The frequency is different for everyone (just like how most children can hear a dog whistle but adults can't) but it lies somewhere between 2,000-4,000 Hz."
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7ce5da | Where does dust come from? and what it is made of? | Repost | explainlikeimfive | {
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"text": [
"Depends where you are. In a home dust is mostly human skin. In a granary it's mostly wheat or corn or beans, seeds maybe sunflowers. Could be rye or barley.",
"It comes through the window It comes through the floor It comes through the roof and It comes through the door Dust is everywhere Sweep."
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7cffdn | How does fridges or freezers work? | Repost | explainlikeimfive | {
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"Have you ever held a can of compressed air while you pressed the trigger? The can gets really cold. When compressed gas is released the container cools. Imagine a loop of pipe. There is a very small valve on one side and a pump on the other. The pump pressurizes the coolant. The valve creates the same reaction of pressure being released. So the side where the pressure is released is cold, but the side with the pump is hot. That's why they put the hot pump on the outside (of the air conditioner or refrigerator). And the cold valve on the inside.",
"Imagine you have a collapsible container of some gas at room temperature, and you begin squeezing it. You're doing *work* on it, which means you're transferring *energy* into it. The only place that energy can go is into the temperature of the gas: i.e., it gets hotter. Now you let the outside air cool the container back down to room temperature. Then you relax your grip on the container and let it expand again. This time the gas is doing work on your hands, and the only place that energy can come from is the temperature of the gas -- so it gets *below* room temperature. In the fridge, a gas goes through a compressor to accomplish the first step. The high-temp gas then runs through tubes outside the fridge in back, where the air cools it. Then it goes through a small orifice, which accomplishes the second step; then it runs through tubes inside the fridge, picking up heat from the contents, and finally back to the compressor. Lather, rinse, repeat.",
"Engineering student currently taking thermodynamics. Fridges and freezers are what’s called thermopumps. Essentially, heat is the kinetic energy of atoms and molecules wizzing and vibrating. As long as a substance is above absolute 0, there is always heat within it. A thermopump sucks in the heat from a region (the inside of your fridge) and dissipates it in another (your kitchen). In nature, heat only moves from hot to cold regions, so how does a thermopump manages to do the opposite? We achieve this by having a refrigerant substance run through a system of tubes, the substance is choosen such that it can be vaporized and liquified easily. There are heat transfers that come with the phase changes (liquid to vapor and vice versa). Last bit of science we need to be aware of to understand the themopump is the fact that not only temperature can induce a phase change, pressure is equally important. In everyday life everything happens at 100kPa so we don’t notice it as much, but water will boil under 100C in high altitude where the pressure is lower. So our refrigerant can be boiled by simply changing the pressure. So now we can get a more applied idea of how the thermopump works. The refrigerant will start as a cold low pressure liquid (colder than the inside of your fridge) that will go through long winding tubes in the inside of your fridge, sucking out the heat to undergo a phase change, turning into vapor. Then enter the compressor, the part of your fridge that requires power, to raise the pressure and temperature of the vapor. It will then go through long winding tubes again, this time on the outside of fridge (your kitchen). The vapor will liquify and thus pouring alot of the heat it gathered earlier inside the fridge, into your kitchen. The high pressure hot liquid will then go through an expansion valve (which will essentially lower the pressure and temperature). Bringing us back to the low pressure cold liquid from the begining. Thus completing the refrigeration cycle. The pressure changes are done to change the phase change point of the refridgerant to the ambiant temperature of both regions. This can be reversed to heat up a home. These systems are more efficient than traditional electrical heaters because they use energy moving heat rather than just generating it. TL;DR: They move the heat inside your fridge/freezer to your kitchen by playing with the refrigerant’s pressure and temperature and phase changes.",
"When you compress air (Make a volume of air take up less space), you heat it up. This happens because all the energy is compressed into a smaller volume. When you decompress air, the opposite happens. This is charles law. So, they take a refrigerant, compress it a lot, then cool it off with room temperature air. They then decompress it and it becomes very cold. You can do this with regular air (nitrogen, oxygen, and carbon dioxide), but it doesn't work as well. Then they run air in the fridge across the cold heat exchanger, which warms the refrigerant up. Rinse Repeat. Air conditioners in your house and car work in the exact same way, but on a larger system."
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7cg90c | How do pills know where to go? | Repost | explainlikeimfive | {
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"They don't, they more or less just (in general) go everywhere in your body via the bloodstream. They just float around their bloodstream until their chemical composition happens to fit somewhere, and that's where they end up. Imagine a round peg going around your body. it will try to fit into every hole it comes across. Eventually it will find the round hole where it fits, but there might be a lot of other combinations it attempted in the meantime. This is among the reasons why Chemo therapy is so invasive, the chemicals being used don't know what are cancer cells and what are healthy cells. They more or less just attack everything with the strategy of killing the cancer before either it or the chemicals kill you."
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7cg9gx | How are receipes for Coca-Cola, KFC and others kept secret with so many people involved in production? | Repost | explainlikeimfive | {
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"compartmentalization, Have no one person know the whole recipe. KFC has the original recipe in a double locked safe with vials of the 11 herbs and spices, and 2 factories that mix them separately before being combined. Coke numbers its ingredients from 1 to 9 with 1 though 4 being publicly known whist 5 though 9 are unknown, there is also considerable speculation on what ingredient 7x is. That could be the main ingredient or just a publicity stunt to cause speculation on why it has the x.",
"Of *course* people know the ingredients in Coca-Cola. Anyone working on the shipping dock knows exactly what goes into the secret formula. Even the notorious \"7x\" ingredient has a whole procurement department who negotiates with suppliers and arranges its shipping. It's not the Manhattan Project over there. But the secret formula is more than a list of ingredients. For example, Coke has quite a bit of distilled orange oil in it. How hot and long you run the still has a huge impact on the drink's eventual flavor. Same thing goes for the coca extraction, and the nutmeg-cinnamon preparation--little changes in procedure can make a big difference. That's why Sam's Choice Cola always tastes a little off. It's the same ingredients, processed roughly the same way. But it's never quite the *same*. You'd have to rebuild Coke's entire production line and supply chain to make a true bottle of Coca-Cola. EDIT: But yeah, they almost certainly keep secret records about the *process* (for example, they would need a record of the ideal viscosity and PH of the orange oil distillate, in case the still breaks and they need to repair it back to original condition). I imagine very few people have access to the whole archive--ie, the quality control guy that verifies the orange oil blend probably has no idea about how to prepare the nutmeg mix. So somewhere in a safe, there is likely the information necessary to make a much better Coke knockoff. But it's a lot more complicated than the list of ingredients. It would be binders full of chemical analysis and procedural notes.",
"They aren’t actually secret. Many companies have already worked out what the recipes are. It’s the brand that can’t be replicated, and it’s the brand that people buy.",
"I worked at a Coca-Cola bottling plant during summers in high school. I was a Syrup Technician. (No joke, that was my actual title) The formula for making coke syrup is as follows: - Man sized barrel number 1 shipped in from a Caribbean factory - Man sized barrel number 2 shipped in from a completely different factory on a different island - 5000 gallons of corn syrup and water That's how its a secret. The barrels were from different places, unlabeled, except for \"#1\" & \"#2\", plain white plastic.",
"Even if someone knew the recipe, it wouldn't matter all that much. Of the ingredients, such as cinnamon, carry widely in taste and wildly effect the taste of composite flavor profiles like Coca-Cola when they are changed even a small amount. All ingredients in Coca-Cola are sourced a single way. You couldn't take the recipe and recreate it.",
"From my understanding every step along the way is compartmentalized. Just like when the us built the atom bomb during ww2. All the departments were working on its own part but not really understanding the whole. For instance kfc is not its own company but owned by a parent company thus when they buy the 11 secret herbs and spices from various distributors its hard to tell where its gonna go.",
"Compartmentalization, to try and prevent knowledge of the whole thing, and non disclosure agreements to keep employees from talking even to each other. Happens all the time in corporate environments."
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7cknz9 | Why is it that people like celebrities can admit to committing crimes in autobiographies but not be penalized? | Repost | explainlikeimfive | {
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"Same way people can talk about crime in a song, etc. It's not a confessional testifying under oath, so as far as anyone is concerned, it's fiction.",
"Most crimes have a statute of limitation. Such as 5 years for vandalizing a storefront. (Numbers pulled from butt) So you can freely admit something after a period of time without fear of being arrested."
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7cq6ed | The difference between race, ethnicity, and nationality. | Repost | explainlikeimfive | {
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"text": [
"Race is your skin color and other typical features of a group. Ethnicity is a combination of race and cultural heritage. Nationality is citizenship to a particular nation or state."
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7cu0fw | Why do we have dominant hands? | Repost | explainlikeimfive | {
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"Also, why is the herd dominant - side usually the right? Are there places in there world where left-handedness is the norm?",
"The best answer i've heard for this has to do with language. As humans developed language it was usually developed in one side of the brain (the left). Before this point there is no clear evidence that humans were right hand dominant. After this point we have evidence that most humans are right hand dominant. The left hemisphere of your brain also controls the right side of your body. The hypothesis is that your right hand (and foot) becoming dominant was a side effect of this side of the brain doing more processing. There is also evidence that people who process language on the right side of their brain tend to be left handed. As for people who process language on their left side of the brain and are left handed? I don't know.",
"In addition to OPs question does the same go for legs? I remember snowboarding for the first time and goofy was the only way. My right leg had to be in front. So what exactly causes that?"
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7cudtd | If technology is advancing exponentially, why is a new computer only marginally faster than my three year old computer? | Repost | explainlikeimfive | {
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"How are you measuring speed? Time it takes to boot up your system? Hard drive speed increased significantly between HDDs and SSDs but is largely on the same level between those. FPS in a game? That should have increased significantly. Time it takes to respond to your input? That is largely a peripheral issue with only minor improvements.",
"Probably because you're not buying the latest technology. For example, three years ago a cutting edge i7-5960X (at the time the \"fastest desktop CPU ever\") scores 15994 on cpubenchmark. The fastest current desktop CPU scores over 27000. That certainly isn't marginal. Comparing GPU's from the same period also shows a significant increase in speed. The reason your new computer is only marginally faster is because that's what the market wants. Most people don't want the latest technology at huge cost. They'd rather have cheap and cheerful that does the job.",
"It's disingenuous for anyone to claim \"tech is advancing exponentially.\" There's no single value for the quality of our technology, so all it really means is that the new stuff being made depends on the most recent discoveries also being present. The changes might be more significant/visible as AI continues to be integrated. I've already seen some crazy stuff it can do, and each incremental success contributes to the next.",
"The answer is that while speed was proceeding exponentially before, the rate of progress slowed down when they hit physics problems we could not easily solve. Space between the bits of the chips were getting so small that weird quantum mechanics was causing electrons to teleport and short circuit the device. The CPUs were running so fast they were practically melting unless you used liquids to cool them down. We sustained some speed increases by working with the stuff we had alot better, or just adding more of the stuff we already had. But until we solve those problems progress is going to be much slower. Once we solve those problems, or find a different way of doing things, we get exponential growth again. This happens with pretty much any technology. For example, compare a gun made in 1887, 1917, 1947, 1997 and 2017. 1887 - > 1917 HOLY SHIT IT NOW SHOOTS MULTIPLE TIMES 1917 - > 1947 HOLY SHIT IT'S LIKE A RIFLE AND A MACHINE GUN HAD A BABY 1947 - > 1997 Uhh, it's made of plastic I guess, oh and it's a bull pup now, thats kinda cool 1997- > 2017 There was a change?"
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7cushe | Why do we lose Appetite when we are anxious/Nervous? | Always happens and it would be awesome to dig a bit into the science of it as well. | Repost | explainlikeimfive | {
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"Much like the 'Fight or Flight' response related to real-world dangers and how we react to them, the brain has a hard time telling difference between a physical threat or a psychological one. Anxiety and Nervousness can be as frightening mentally as a dark alley way or a guy with a knife across the street. When your body goes into 'Fight or Flight' blood is moved away from the stomach and to areas where it might be used to run or fight, such as the legs or arms. Less activity in the abdominal region and an increase in adrenaline are some of the many causes to losing your appetite. TLDR- Your body is allocating bodily resources effectively for a threat it perceives to be real and life threatening, but is really just mental anguish that it cannot differentiate.",
"To tag on to OP's question, why do some of us do the opposite and stress eat?",
"To go along with other answer, your gut can also sometimes induce vomiting if you are under very heavy stress In order to free up even more resources for the fight or flight response. The sympathetic nervous system, I believe, is responsible for increased heart rate, faster breathing, and tightness in the gut in order to prepare you to respond to threats. Even though it may just be as simple as a math test. Our body releases the same stress hormone so we have the same reaction. Even though the stress we feel today is mostly social anxiety stress or such, we still react as though we are physically in danger and food can wait to digest later. Surviving now is more important than getting a bite to eat to our brain. Edit: changed reaxy to react. What the hell autocorrect",
"The exact response is determined by the type of anxiety or stress you’re feeling. Long term stress such as a final coming up/big event you have to get ready for are handled by the internal medulla of the kidney. This area produces a “compliment” to adrenaline called cortisol. Cortisol causes you to have a large craving for fats and carbs so that your body has energy reserves for when the big event occurs. It expects you to be in a big fight or have to run far, so it can turn the fat stores into energy. Thats why stress eating is such a problem. It’s natural and can’t truly be fixed The external kidney, the adrenal gland, produces adrenaline. Adrenaline acts to stim blood flow away from non-essential parts of your body to your lungs and heart so you can do things faster (important to note NOT LONGER). It primarily pulls it away from the gastro-intestinal region, the extremities, etc. This is why great cold medicine uses pseudoephedrine. This copy of adrenaline is made as an extended release to open airways so you can get more oxygen and counter that stuff nose",
"Anxiety is fun: The liver releases sugars and fats which flow into the blood stream to provide energy. Breathing becomes faster, providing more oxygen. Heart beats faster and blood pressure rises to make sure blood reaches the areas needed. Blood clotting mechanisms are activated in case of injury and bleeding. Muscles tighten, ready to run or fight. Saliva dries up and digestion stops so that more blood can be diverted to the muscles. Sweating increases to cool the body. Bowel and bladder muscles may become loose. Pupils in the eyes widen to let in more light and help clearer vision. All senses are heightened. Brain thinks of other things that could be a threat. Blood supply is diverted from the skin to reduce bleeding if injured.",
"for questions like this I find its always very helpful to adopt a \"primitive\" mindset. by this I mean lets think about this if we were living in caves in the year 10000BC what would make us nervous/anxious back then? a predator coming to eat us. under these conditions would it be useful to be distracted by a nagging sense of hunger? Nope. to effect the necessary changes we have the Sympathetic and Parasympathetic nervous system. Simply put; just equate sympathetic to \"fight or flight\" and parasympathetic to \"rest and digest\".",
"Your brain is so focused on whatever is going on in your head that it forgets about your stomach. Basically it's saying \"I'm hungry but I'll worry about that later because this shit's more important.\"",
"The stomach and intestines don’t need much blood when you’re ready to run. If they ain’t got blood they don’t need food.",
"Same reason you might have to poop when you're nervous. It's part of the fight or flight response. Your body might need to move, FAST - less weight can make that happen.",
"Also neurotransmitters which ordinarily are sympathetic, (speed up/stimulate) others area of the body such as the heart and noradrenaline, have a parasympathetic effect on the stomach and digestive organs! Slows down digestive tract and gastrin release when released!",
"To add to what everyone has been saying about fight or flight, I'll add a little bit of Neuroscience. Your stomach has a lot of neurons in it, therefore there's a lot of neurotransmitter action happening there. This is where our \"gut feeling\" comes from. When it comes to fight or flight, you're dealing with the transmitters epinephrine (adrenaline) and norepinephrine (noradrenaline). Norepinephrine acts first. It's function is to get the body ready for action. Specifically, in the digestive tract, it activates this thing called gastrointestinal motility, which, for the digestice tract, is the ability to move food down the tract. To recap, fight or flight is triggered then a transmitter called norepinephrine inhibits the digestion process and it can do this because the stomach has a lot of neurons. Okay, now why does this need to happen? Yes, part of it is that you have better shit to worry about in the moment but that just doesnt have to do with the presence of danger. Part of it is to counter the negative effects of adrenaline. Adrenaline is the thing that gives you an increased heart rate and a higher blood pressure when you are in a fight or flight situation (also helped by noradrenaline which releases glucose in your body) and when it's released, it increases stress and gives anxiety and in the stomach, it makes it rumbly. Noradrenaline comes in and controls this effect, which ends up as you not feeling hungry! Tada! Sources: a few psych/neuroscience classes and I have adrenal issues.",
"Follow up question: Why do I eat my weight in Doritos when I'm nervous?",
"A bookend question, why after your nerves calm do you have a sudden urge to poop?",
"When you're scared your body thinks you are in imminent, physical danger If you're in danger of death, you really don't need to digest any food inside of you, you have more important things to worry about Part of your body's response is to take blood away from your stomach and to the muscles in your arms and legs, since you will need to either run or fight",
"here is a physiological explanation for this. When your are frightened, anxious or nervous, your body increases the activity of the sympathetic nervous system. This makes your body ready to run if there were some sort of danger. Sympathetic activity includes - Increased heart rate and increased heart contractility to increase the amount of blood reaching your muscles - Increased blood shunting (taking blood away) from non important parts of the body in times of danger (such as the stomach, intestines, prefrontal cortex, kidneys etc) -Increased blood flow to the muscles and heart to react Anxiety is the result of chronic activation of this system which explains the seemingly permanent loss of appetite."
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7cvd2h | Why does moss/algae podaminantly grow on the north side of trees, houses etc. | Repost | explainlikeimfive | {
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"The sun rises in the east and sets in the West and Generally in the northern hemisphere the Sun comes out of the South so the north side of buildings, trees, etc. Is the only side that doesn't receive direct sunlight and is thus the most likely to grow moss. The lack of direct sunlight results in dew, rain etc drying up the slowest on this side letting the moss grow."
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7cz2j0 | - In moments of intense concentration... why do we poke our tongues out? | Repost | explainlikeimfive | {
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"When we focus on precise tasks, ideally you'd want to devote 'everything you've got' to finishing or performing them. Take painting for example, most of your focus is directed towards your hands and arms (Motor skills). Your body is always gathering information and reconstructing how, for example, the surface of a table feels, how cold or hot things are, and if you're upside down or right side up. A very important receptor is your *tongue*, which is one of the most densely populated bundles of receptors you've got. from a young age, you might have done this unconsciously yourself when focusing on a difficult or precise task. Essentially your tongue pokes out to prevent the sensations, tastes, and general feelings your tongue will send to your brain and disrupt your focus on other parts of the body. TLDR- In an effort to keep focus on a task, your body will unconsciously suspend some more prominent motor skills and sensations (In this example, the tongue) to prevent external stimuli from interfering with whatever you're currently focused on."
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7cz6lw | Why are scientists looking for water on other planets? It may be necessary for life here, but what makes us think other species need it too? | Repost | explainlikeimfive | {
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"We know what life looks like that requires water. We know the signs, we know it is possible, and it is something we can look for at a distance. Could there be an alien species out there that views water as acid and ammonia as clean air? Sure. But we have no idea if life can do that, and we have no idea what to look for if it does. So we go with what we know, at least until making planetfall onto distance planets is an option.",
"Currently Earth is the only reference for life we have, so our current searches for life are based on it."
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7d19n6 | Why does hitting your shin on something like a scooter or shopping cart hurt so much and for such a long time? | Repost | explainlikeimfive | {
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"Probably because it's a more direct hit on your bones. There's no (or very little) muscle there to absorb the hit."
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7d2qgd | What causes the tingling sensation known as 'pins and needles'? I know that it is a lack of blood flow in a part of the body, but why does that make it tingle? | Repost | explainlikeimfive | {
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"Contrary to popular belief, the pins and needles feeling isn't due to lack of blood flow to a body part. If that were true, my leg would have probably died due to lack of oxygen on the bus ride home. It's actually due to the fact that once you put pressure on a part of your body, you can actually cut off communication to that part from the point of pressure onwards. The pressure squeezes your nerve pathways so that they can't transmit sensations or receive orders from the brain as well as it should be. It's why your foot goes numb if you sit with one of your legs crossed, or if you're on a long cramped bus ride. Pins and needles occur after this connection with the brain is back to normal. It takes a while for your leg or whatever to get back in the full swing of things, and the pins and needles are just the sensations of that body part's nerves adjusting to the stronger connection it's getting."
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7d2s8o | What causes the feeling of Déjà-Vu? | Repost | explainlikeimfive | {
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"Sometimes something *really has* happened before. Like this question! :-) 1. [ELI5: What happens when we experience déjà vu? ]( URL_6 ) 1. [ELI5: Why do I sometimes experience Déjà Vu? ]( URL_4 ) 1. [ELI5: What is deja vu and how does it work? ]( URL_5 ) 1. [ELI5: Why do we sometimes feel Déjà Vu's ]( URL_2 ) 1. [ELI5: How exactly does Deja Vu happen, and is it abnormal to experience it daily? ]( URL_7 ) 1. [ELI5:Why do We Have Deja-Vu In Different amounts of Severeness? ]( URL_8 ) 1. [ELI5: Déjà vu ]( URL_3 ) 1. [ELI5: Why do people have Deja vu for things that clearly never happened? In other words, what happens in your brain when you experience deja vu? ]( URL_1 ) 1. [ELI5: Deja Vu. Why does it happen and How? ]( URL_0 )",
"Another analogy is that you brain sends a message to your ‘memory bank’ & then waits for the memory bank to confirm it has received it. Sometimes there is a delay in the memory bank sending the confirmation it has received the message, so the brain sends the message again & the memory bank gets double stimulation. It’s the confirmation from the second lot of stimulation that gives us the feeling of ‘I’ve seen this before.....’ Yes. Less than a millisecond ago, but because it didn’t get confirmed as stored the first time, you can’t remember where you’ve seen it"
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7d4h83 | How does a mental condition like stress or depression take a physical toll on ones body? | Repost | explainlikeimfive | {
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"Think of your body as a regular starship. Usually the crew goes on with its regular duties, on regular schedule and work efficiently. A lot of the stuff is boring stuff like routine maintenance, cleaning the ships, preparing meals etc. Then an alarm goes off. \"Under attack by Klingons!\" The crew now goes on high alert. The phasers are ready to be fired on command. The shields can be deployed in a split second. All life-support systems are checked to ensure that nothing goes wrong. But this comes at a price. They are now working on shorter sleep. All non-essential tasks get cut back. Trash accumulates, the meals served get simpler, regular maintenance is postponed. This lasts as long as the alert is on. But the alert never goes off, even when there is no threat. All that lack of maintenance comes back and things start breaking over time. Garbage accumulates. The crew makes mistakes due to lack of sleep. Stress is like a state of constant alert. In the short term, the body is able to do stuff it could not normally do. Pull an all-nighter for that exam- pfft. In the long run, everything that the body has been postponing addressing comes back to bite you, and the body suffers as a result."
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7d5l3g | Why do men go bald but most women don’t? | Repost | explainlikeimfive | {
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"**Dihydrotestosterone (DHT).** It's a more potent cousin of normal testosterone. It's a super hormone of sorts! And it has profound impact on the men. From the development of genitals to pubic/body hair to maintenance of prostate, etc. Sadly, as a side effect, it also causes pattern hair loss typically associated with men. Some men's hair follicles are more sensitive to it than others'. Some produce more DHT than others. And typically those people have higher likelihood to become bald. Women don't need DHT as much as men do. So, they produce far less. So, DHT is not the leading factor for their hair fall."
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7d8x4p | How exactly does lobotomy work and how does it affect the person after the procedure? | Repost | explainlikeimfive | {
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"Depends on what kind is performed. The \"ice pick\" one we've all heard of is very rudimentary and accesses the frontal lobe through the eye socket. It attempts to \"helpfully\" damage the frontal lobe to theoretically calm people with violent or volotile emotions. Mostly it just leaves them catatonic. Edit: I recently learned this from the book \"brain on fire\" about the author who struggled with encephalitis"
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7dbun3 | Why does social media sites like Facebook want you to use their app instead of the mobile website? | Repost | explainlikeimfive | {
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"text": [
"If you download and install their app they have a lot more data on you. If the service is free the product is you."
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7dcxmj | Why does an object traveling at the speed of light gain infinite mass | Repost | explainlikeimfive | {
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"Relativistic mass is an outdated concept. Many contemporary authors such as Taylor and Wheeler strongly argue against the concept of dynamic mass, and most modern textbooks actually avoid it. Taylor and Wheeler state [1] > The concept of \"relativistic mass\" is subject to misunderstanding. That's why we don't use it. First, it applies the name mass - belonging to the magnitude of a 4-vector - to a very different concept, the time component of a 4-vector. Second, it makes increase of energy of an object with velocity or momentum appear to be connected with some change in internal structure of the object. In reality, the increase of energy with velocity originates not in the object but in the geometric properties of spacetime itself. It is a lot more more useful to simply stick to rest mass and consider the increase in kinetic energy of a fast moving object. [1] E. F. Taylor, J. A. Wheeler (1992), Spacetime Physics"
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7dhq8o | why some people pass out when they see blood? | Repost | explainlikeimfive | {
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"This is caused by the vasovagal reflex/reaction/response. It's the same thing that can make you pass out from severe pain, fear, or being stuck in a stuffy, hot room. Normally this reflex helps maintain your blood pressure, but when it's triggered by emotional reactions it can \"run away\" without control. Super simply put, it's dropping your blood pressure until you pass out. Some people have a really strong fear of blood due to past experiences and/or lack of normal exposure to blood -- enough so to trigger this response uncontrollably."
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7eg9ra | How can almost every country in the world be in debt? Can't some of the debt cancel out? | Repost | explainlikeimfive | {
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"Countries borrow money from other countries **and** individuals. You can buy a bond from your country - meaning your country owes you money.",
"Alice borrows $1 from Bob. Bob borrows $1 from Claire. Claire borrows $1 from Alice. Everyone is in debt. If there is interest on the loans, then everyone owes more than they are owed.",
"It does cancel out. I think the word you mean is **deficit** not **debt**. I owe my brother Rick $20 for beers last night, which I'll pay him later. I also have some cash in the bank. I have a *debt*, but in total I have more money than I owe. I have a *surplus*. ... My friend Kevin owes $10k to the student loan company which he pays every month, but he only has $5k in the bank. Kevin has a *debt* that is more one than he has. Kevin has a *deficit*. ... My parents owe nothing and they own a house. They have *no debt*. They have more money than they owe. My parents have a *surplus*. ... Just because a country (or person) has a debt does not mean it [has a deficit]( URL_0 ).",
"Debt is simply money owed at a certain time. Countries issue bonds or make other agreements to pay others at a later date, so now they are in debt. They can’t pay it all off because right now isn’t the time all that money is due.",
"The money that is owed by governments is not necessarily owed to other governments. It is owed to all kinds of people--individuals, companies, and organizations that might be anywhere in the world. If you own a government bond, then part of that debt is owed to you."
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7ep8nm | How do ISPs work? Where do they get their internet? | Repost | explainlikeimfive | {
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"Think of it this way. The internet is like a postal network. The ISPs are the postal service. They coordinate all of the packages and make sure that they arrive at the right place, on time. The ISPs can also expand the road network to reach more customers. They can also widen existing roads so that more traffic can be handled. All of the different ISPs around the world work together just like most postal services around the world."
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7f1xbh | Shaken not stirred | Can anyone explain why or what would be the difference between a shaken drink or a stirred one. | Repost | explainlikeimfive | {
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"For drinks it's much more \"high class\" to have it stirred and not shaken as many think it dilutes the ice more if it's shaken... That's why it was always odd when James bond would say shaken on stirred... But honestly I've never tasted a difference between the two... It's just a weird thing like pinkies out and stuff like that",
"When you shake it, the ice breaks a little, melting faster, watering down the martini. Stirred could be seen as the more pretentious, upper class way of drinking it, and it could be part of James' desire to rebel against the posh world he finds himself in by having the more down to earth, \"rough and ready\" version of the drink. However, I do believe in the books he asks for it stirred, not shaken, but when making the first movie they decided it sounded better the other way around."
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7f35f9 | Why do you have to salt pasta water? Why isn't the pasta already salted? | Repost | explainlikeimfive | {
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"There are a few reasons not to add salt to the pasta dough itself. The most important that I know of is that adding salt to the dough slows down gluten production. Since pasta dough tends to be made quite quickly (unlike bread dough which is given time to rise) the addition of salt at the dough stage would result in a sloppy dough. It's easier form a manufacturing standpoint to leave the salt out at this stage and compensate later. A second reason is that pasta dough is usually made with only flour and egg - no water. Thus, there is little material for the salt to dissolve in and one tends to end up with grains of salt present in the dough. This provides an unappealing texture as well as potentially uneven flavor to the pasta. Perhaps this can be circumvented somewhat by pre-dissolving the salt in the egg mixture. Thirdly, it is good from a manufacturer's point of view to allow the consumer to season the pasta to their desired level of saltiness, both for health reasons and personal flavor preference. It also allows them to get a lower sodium measurement on the packaging."
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7f4ii7 | What exactly are the economic benefits behind Black Friday for companies and consumers? | Repost | explainlikeimfive | {
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"They’re goal is to get you in the store with the promise of a $150 50 inch 4K tv ( which they only have about 7 of) so you can then spend money on other things at the store.",
"They don't actually make a whole lot of money it's all about sales numbers, it actually cost him quite a bit in margins at the store level. But the idea is that you win the consumer over for the holidays so they spend the rest of their money there that you have marked up.",
"Many manufacturers have left over inventory and want to move all this product. Others just want you in the store, because you might buy other stuff (not on sale). There are tons of reasons to mark stuff down around the holidays, and black Friday grew into it's own holiday as a full day for shopping is good for all retailers."
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7fb2op | How do cellphones know what signal from what network to listen to? What is different about different networks' cell towers that a phone can decipher which one to listen to? | Repost | explainlikeimfive | {
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"text": [
"Your cell phone is basically a very fancy radio. For it to communicate with the tower it needs to know what frequencies to broadcast on. It has a SIM card that tells it what network you're subscribed to and which frequencies to broadcast over and receive."
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7fdex8 | why didn't medevil paintings have any perspective? | For example: [No perspective]( URL_2 ) [Nearly flat]( URL_0 ) [An attempt at creating perspective but it comes off as almost abstract]( URL_1 ) [Looks like they were going for realism, but still that darn perspective]( URL_3 ) Now I'm not bashing medieval artists (and I'm not a history buff so I could be pulling some of these from different points in time, I just hope they're all before the rennaisiance) but it strikes me as a bit odd that these people, who were in the profession of making art and probably had been for most of their lives, were leaving out such an important detail like figures getting smaller the further away they were. Maybe it was just the style at the time, maybe they were just designed to be easy to read on a mural as a story, maybe without glasses to enhance vision it didn't really matter if there wasn't a certain degree of detail, whichever way I've always wondered this, and the fact that as you go further back in time, you seem to get less and less perspective (think Egyptian art) Can anyone tell me if there are any theories or anything explaining this? | Repost | explainlikeimfive | {
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"Artists had not developed the technique of perspective until the beginning of the 15th century with Italian architect and artist Fillipo Brunelleschi. Medieval paintings don’t have perspective because it was not a “thing” yet. A lot of artists attempted to create it but didn’t really understand how to. Brunelleschi was the first to figure out linear perspective, or making two lines converge to make them appear to look more distant. Other artists then caught on, mimicking the technique.",
"> it strikes me as a bit odd that these people, who were in the profession of making art and probably had been for most of their lives, were leaving out such an important detail like figures getting smaller the further away they were. It is a one-two punch of being ignorant of the technique and not desiring to learn it, as the focus of the art wasn't the accurate reproduction of the scene or the human form but rather the spiritual or symbolic meaning behind the image. Baby Jesus for example didn't look like a real human child, but it may have been considered a virtue that he didn't appear as such because he was supposed to be different. There is also the matter of what defines \"good art\" in the view of the time. Was it perspective and proportion, or subtle shading and composition to draw the eye? Is symbolism or making sure the top of the table is parallel to the ground more important? The focus and meaning of art was different during that time which yielded images that may not be seen as good today.",
"I'm not an art historian but I did take an art history course which explained one reason why it was hard for artists to nail perspective. Before the invention of oil paints, most paintings were frescos. A fresco is color applied to a wet plaster wall or ceiling. Once the plaster dries, the work cannot be altered and the plaster dries quickly. Therefore the painting must be done rapidly, without too much attention paid to details like perspective. Another drawback to a fresco is that it must be done on the wall, which - depending on the wall - may limit the use of live subjects. This may mean the artist has to rely on memory or sketches of the scene. Paper wasn't even available until 1100 and was quite expensive once it did become available, so most preparatory drawings were done on wood, slate, or wax. These preparatory drawings tended to be reused by an artist for multiple paintings since they were difficult to produce. The advent and wide adoption of oil paint in the 15th century fixed these two problems. Oil painting allowed artists to work slowly and granted them the freedom to use canvas which is comparatively mobile. This meant they could actually be at a scene they were trying to illustrate and could take days or weeks to work instead of hours, so their subjects could really be studied and their paintings could be perfected. Also, by 1500, paper and graphite were widely available and sketching began to be considered a serious art. This probably also had some impact on artists as they refined their sketching skills which no doubt translates to better painting skills. Edit: I forgot to mention that with a fresco you cannot even fix a mistake by applying a second color over the first color. With oils, you can wait for the first color to dry and apply a new layer of paint. This plus the ability to work slow dramatically changed how painters worked."
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7fk0zl | How are mountain goats so nimble and sure footed? | Repost | explainlikeimfive | {
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"Part of the success of mountain goats is the design of their hoof. Think of them like a set of hands that are able to grab onto the mountain. They are less standing on the side of the mountain and more grabbing the side of the mountain. That said sometimes mistakes happen, and those mistakes help to guide the next generation.",
"Because the ones that aren't went **splat** on the side of a mountain and didn't get to make babies. The ones that survived had the best sense of balance, the best feet, and the best instincts for surviving.",
"Mountain goats have a rather bizarre foot structure, where they essentially balancing on thier toes and have a fatty cushion for their heel. They can also control their hoof split. Imagine a ballet dancer with no discomfort who can also wrap her toes around things. I've climbed fifty feet up a sheer rock face only to have one of these bastards run straight up to say hello. They can hug crimps that we can barely see. On top of that, they have a severe lack of the fear of heights. But they aren't perfect. Recently in my local news a goat jumped off a cliff and landed on a car. As they age, their weaknesses kill them. The ones with better balance and eyesight live much longer and have more offspring. They are built like linebackers. They have extreme control, and that helps them evade predators and reach food. Tl;dr study bodies, nimble feet."
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7fmt1c | Why do Tupperware (and some other plastics) get white spots after being washed in washing machine? | Repost | explainlikeimfive | {
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"The dishwasher (and microwave) can get too hot, melting the plastic, which causes this. To prevent, hand wash and don’t use in the microwave.",
"Everyone else is wrong. White spots on Tupperware are hard water deposits. Good luck preventing them, they are harmless though."
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7fn3t4 | Why are credit cards used so much these days and what are the benefits of it over a debit card? | Repost | explainlikeimfive | {
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"A lot of people seem to be giving you the same bad information you've likely already heard. Credit cards don't inherently equal debt, they are tools. Different cards are intended for different uses. Many people think of credit cards as a way to buy now, and pay over time. While you certainly can do that, you really shouldn't in most cases. There are two types of credit card users. Revolvers, and transactors. Revolvers spend money, and carry a balance, paying interest over time. This type of credit card use should be avoided except in circumstances where you may have no other choice. Transactors use credit cards for their normal spending, and pay them off in full every month. Many people aren't even aware of the fact that if you pay your statement balance in full every month, you don't pay any interest. Credit cards have 4 primary advantages: Rewards- Typically in the form of cash back, or travel points etc. Security- If your card is ever compromised, it's much easier to deal with the claim on credit than it is on debit. Benefits- Credit card companies also offer you some purchase benefits, such as extended warranties, free insurance in rental cars, matching sales prices after purchase, ticket concierge services, and more. Flexibility- Being able to purchase the things you need, and pay bills when they're due, and knowing you'll have a single payment on the same day every month makes it much easier to budget. It can help avoid a paycheck to paycheck lifestyle. It requires discipline to use credit cards and not accumulate debt, but the advantages are well worth it for those who can use them properly.",
"A credit card provides protections that you don't have with a debit card. For example, if your credit card is compromised, you simply dispute the charges, you are not actually out any real money. If your debit card is compromised the fraudulent charges aren't just on paper, the money is actually taken out of your account, so you then have to go through the whole dispute process to get your money back. In the meantime your account is locked and you have no access to your money, if there is any left.",
"* It's easier than carrying cash * It's _way_ easier than paying with a check * It's an easy way to track how much you're spending and where * As long as you pay off your balance in full each month, there's (generally) no additional cost * Having available credit in the form of a credit card boosts your credit score (provided you aren't carrying a huge balance). Paying it off (or at least the minimum payment) consistently each month builds a good credit history. Both are good things to have. * Credit cards often offer rewards, in the form of airline miles, points, cash back, etc. * Lesser known benefit: purchase protection/warranty extension. Credit card companies will often cover purchases for a limited time after the manufacturers warranty expires. I was able to get a tablet computer replaced 14 months after I bought it because I bought it on a credit card. As far as benefits over debit cards, as other people have eluded to the risk is higher with a debit card. If someone charges $1000 to your credit card, you have a $1000 charge on your card until your card issuer reverses it. If someone withdraws $1000 from your bank account, that money is gone until the bank replaces it. That means checks may start bouncing, you can't withdraw money, etc. Huge hassle. There are benefits to debit cards, however: * Using them (or misusing them) won't affect your credit score. It will affect your bank account, however. * Prices using debit cards can (sometimes) be lower. Swipe fees charged by banks to merchants are generally lower for debit. That savings is sometimes passed on to you. * If you can get a bank account, you can get a debit card. If you have bad or no credit, getting a credit card can be difficult: you may end up with higher fees, a lower credit limit, or you may be outright rejected. Tl;dr: Easier, less liability, more rewards. Just be smart about it."
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7frj2o | How can a piece of paper folded 103 times be larger than the observable universe? | Repost | explainlikeimfive | {
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"Exponential growth. Each fold doubles the thickness of the paper. If I gave you 1 penny today, and promised to give you twice as much money tomorrow, and twice as much the day after, and so on and so on, on day 30 I'm giving you over $5 million dollars. You can do the math on this yourself pretty easily though. Open the calculator on your computer, and type in 0.0039 (the thickness of a piece of paper). Press the Times button, and then the number 2, and press enter. Now press enter 102 more times. By the mid-50's your calculator will actually reach a point where it has to start using exponents, and by 60 you'll have surpassed the what the calculator is capable of.",
"And not to be pedantic, but wouldn't the stack of folded paper be *thicker* than the diameter of the observable universe, but it's *width* would be 1/2^103 times the size of the original width dimension, and it's length unchanged? The point being the *folded paper* won't be bigger than the observable universe; only one of it's principal dimensions (thickness).",
"When you fold something once, you make it 2x as thick. Fold it again, you make it 4x as thick. Fold it N times, you make it 2^N times as thick. 2^103 is a very, very, very large number. (Approximately 1 followed by 31 zeros.) So even if you are folding something very thin, if you were able to fold it that many times, it would become 10^31 times thicker.",
"It's math. Theoretical in that I think 10 times is about the most that's ever been achieved. More interesting to me has always been how big a piece of paper would have to be to start with, assuming it possible to be in a position to fold it 103 times. That's even simpler math but I've never gotten around to it.",
"As others have pointed, it's not physically possible. If it were, the surface area of the paper would also shrink by a factor of 2 each time. So you'd end up with more like one very, very, very thin rod that's longer than the observable universe. The long and short of it is, exponential growth is *very* fast. The difference between a single byte and a kibibyte is just 10 powers of 2. Same with going up to a mebibyte, gibibyte, tebibyte.. That's still \"only\" 40 powers of 2.",
"It's not so much an arbitrary number of folds, as it is an exponential increase in thickness. Imagine it took X folds of a single sheet to be taller than the empire state building. At X-1 (one away) it would only be half as tall. At X-2 it would only be 1/4 as tall. Another way to think about it is each fold doubles the height, thus the 20th fold creates the same increase in size as all of the 19 folds that came before, and the 100th fold creates the same increase as all the 99 folds before it. What is interesting is when it comes to the maximum size something can be, and the minimum size, our existence is quite a bit closer to the maximum, than the minimum. Like if you changed your size by a factor of 10, you could do this farm more times getting smaller, than you could getting larger."
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7frqkg | Holding onto nothing but paint, how can a praying mantis stay on the roof of a car traveling 60 mph and not get blown away? | Repost | explainlikeimfive | {
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"The micro surface of the paint, and the mantid’s legs, are both rough. Think like the legs of a hiking boot dug into rocky ground as you face the gale."
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7fv07s | how does one alphabetize kanji? | English for example has 26 letters in defined order and words or names can be sorted easily this way, for example, making directory for business employee or phone book, or dictionary for words. But in Asian countries like Japan, their name aren't spelled in letters but in kanji and there can be several thousand different symbols for words or names. How would a school sort student's name? Or how would a typical Japanese dictionary be sorted so they can quickly look up word? Not just Japan, but many Asian countries (China, Korea, etc) | Repost | explainlikeimfive | {
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"Korean doesn't fall into this category: it actually uses a real alphabet. Those characters that look like complicated Chinese-style logograms are actually syllable blocks, made up of (usually) two or three letters that represent sounds, and these letters have a fixed order (however, North Korea and South Korea use different alphabetical orders). For example, the writing system is called \"한글\". It's two syllables, and each syllable is read from left to right and from top to bottom. The individual letters are: * ㅎ = h * ㅏ = a * ㄴ = n * ㄱ = g * ㅡ = eu (sometimes transliterated \"ŭ\") * ㄹ = l -- so: \"hangeul\". No problem at all: \"ㅎ\" is 19th in the South Korean alphabet. Chinese ideograms, or kanji in Japanese, are more complicated. They're sorted by radical and stroke count. The \"radical\" is the part of the character that gives you a clue about the meaning of a word. For example, the character \"媽\" means \"mother\": the radical is on the left, \"女\" and means \"woman\". The rest of the character, \"馬\", gives a clue about the pronunciation. Its actual meaning is \"horse\", but in Mandarin Chinese it's pronounced \"mǎ\". This is *almost* the same as \"mā\", the word for \"mother\", so the whole character means: \"This is a word for a woman, and it sounds a bit like the word for a horse.\" There are a bit more than 200 radicals in Chinese, and they're sorted according to the number of strokes you need to write them. [Here's a list of the 214 radicals encoded in Unicode]( URL_0 ) -- notice how they get more complex the further down the list you go. So most dictionaries are arranged such that you first look up the radical, and then you look for the character you're searching for, again according to the number of strokes. If you want to look up \"媽\", for example, you need to first find \"女\", which is the 38th radical. You'll have a long list of characters that use that radical, again sorted from least strokes to most strokes -- you know that \"媽\", which needs 10 extra strokes, is going to be further down the list than \"奴\", which needs 2. [This is the list of characters that use the 38th radical]( URL_1 ) -- there are 681 in all.",
"There are three different kinds of character systems in use in East Asian languages, ones that represent simple sounds (alphabets), ones that represent whole syllables (syllabaries), and ones that represent concepts (logographic systems). They're treated differently, and the same language sometimes uses multiple sorts (for instance, written Japanese uses both the logographic kanji and the syllabaries hiragana and katakana). Alphabets and syllabaries typically just have a canonical ordering of the characters, and they're sorted lexicographically in the usual way. Logographic writing systems are really what you're asking about, though, and those have a couple different ways. The most common is the radical-and-stroke system. Each character is classified into groups based on what the \"primary\" component (known as a radical) is, and those radicals are then ordered. Within a single radical, characters are sorted by the number of lines (known as strokes) used in the character, from least to most. Within a group of characters with the same primary radical and number of strokes, ties are broken relatively arbitrarily (usually there's a convention for this). Another way is to sort them based on how they would be written in a different writing system that has a built-in sorting method. Some Japanese dictionaries and such are done this way, by sorting words based on how they'd be written in kana. Some languages that use CJK characters don't have such an option, though, since they don't have more than one writing system.",
"Korea has an alphabet song, just like English. Their is an order is 가 나 다, etc. So, names are ordered by their \"alphabet\" first symbol."
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7fw4gr | Why does hard physical activity sometimes cause you to throw-up? | Repost | explainlikeimfive | {
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"Basically, it's an evolved response. Intense exercise triggers the production of hormones like adrenaline. These hormones divert blood from the digestive system and to you muscles in order to provide your muscles with the oxygen and nutrients needed to perform. The lack of blood flow to your digestive system causes digestive disfunction like nausea and diarrhea. In a world where we are fleeing from predators, every bit of energy is needed to survive. Temporarily halting normal digestion to provide extra energy to your muscles can be the difference between life and death. Additionally, dehydration and over hydration (hyponatremia), both common in exercising individuals, can cause nausea."
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7fxzrg | Why do people get hiccups when they're drunk? | Repost | explainlikeimfive | {
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"Yo ho ho! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why do people hiccup when they are drunk? ]( URL_8 ) 1. [ELI5: Why do you get hiccups when you drink too much? ]( URL_3 ) 1. [ELI5: why are people more likely to get the hiccups when they're drunk? ]( URL_4 ) 1. [Why is having the hiccups associated with being drunk in film and television? ]( URL_7 ) 1. [ELI5 why do intoxicated characters in old cartoons get the hick ups? ]( URL_2 ) 1. [ELI5: Cold weather alcohol = hiccups. Why? ]( URL_5 ) 1. [ELI5: Why do people get the hiccups when drinking? ]( URL_1 ) 1. [ELI5: Why does alcohol cause hiccups? ]( URL_6 ) 1. [ELI5:Why do people hiccup when they've been drinking alcohol? ]( URL_0 )"
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"https://www.reddit.com/r/explainlikeimfive/comments/5ejdsg/eli5_why_do_people_get_the_hiccups_when_drinking/",
"https://www.reddit.com/r/explainlikeimfive/comments/34lp17/eli5_why_do_intoxicated_characters_in_old/",
"https://www.reddit.com/r/explainlikeimfive/comments/1ie0nx/eli5_why_do_you_get_hiccups_when_you_drink_too/",
"https://www.reddit.com/r/explainlikeimfive/comments/2mc2p5/eli5_why_are_people_more_likely_to_get_the/",
"https://www.reddit.com/r/explainlikeimfive/comments/5j72co/eli5_cold_weather_alcohol_hiccups_why/",
"https://www.reddit.com/r/explainlikeimfive/comments/4k2b8m/eli5_why_does_alcohol_cause_hiccups/",
"https://www.reddit.com/r/NoStupidQuestions/comments/2s2kz5/why_is_having_the_hiccups_associated_with_being/",
"https://www.reddit.com/r/explainlikeimfive/comments/367mlu/eli5_why_do_people_hiccup_when_they_are_drunk/"
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7fzkyr | Why do ice cubes in a drink not want to move no matter how much you rotate the cup? | Repost | explainlikeimfive | {
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"Friction and inertia. Ice floating in water has very little friction with glass. In fact, the water functions as a lubricant between the two. The ice has mass. Mass resist motion. By spinning the glass you are trying to move the ice by moving the water. Water doesn't have enough friction on its own to move the ice easily. Given enough time in one direction the ice will begin to spin. If you oscillate you cancel out all movement.",
"When you rotate a glass you generally do this at low speeds. The ice cubes will not rotate because the only method to transfer momentum at these low speeds is through friction, specifically shear stress in the fluid. This can be attributed to the \"stickiness\" of the liquid, and can be visualized if add something like soap to water. You will see as you rotate the glass the fluid near the glass edge moves at approximately the same speed as its surface, but towards the center there is virtually no movement. You can solve this using polar-cylindrical coordinates of the Navier-Stokes equations. Now, if you put a spoon into the glass and spin it, youll find that the ice cubes move much more easily. This is because the spoon induces advection. Advection can be thought of as bulk motion of the fluid, for example large vorticies you see behind airplanes or the turbulence you observe when you jump into a pool. Advection is dissipated through shear stress, which is described above and why these large vorticies eventually \"disappear\". Essentially, motion that induces advection induces higher pressure gradients, which in turn induce a larger force on near by bodies. TLDR: turning the glass does not induce advection, it induces viscus motion which is only appreciable at small scales of motion."
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7g50d0 | Why do balloons make such a loud noise when they pop? | Repost | explainlikeimfive | {
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"A balloon is essentially a vessel of compressed air. When the balloon pops, all of the air inside is released instantly and forms a pressure wave as it disperses to return to atmospheric pressure. You perceive the pressure wave as a loud noise when it strikes your ear drum.",
"Imagine you had a phone booth full of water somehow sitting on the surface of a calm lake, and suddenly its walls disappeared. The water would rush out of it and create a wave that shot out in all directions until the lake evened itself out again. This is similar to how all of the air squeezed up inside a balloon pushes out and creates a pressure wave that you can hear when it bursts and equalizes with the air around it. People are pointing out that the balloon pop itself isn't really all that loud, it's mostly the acoustics of the room around it. To understand this, imagine you have the same phone booth sitting at the middle of a circular swimming pool. When the water rushes out, the resulting wave will bounce off of the outer edge of the pool and rush back inwards. It can then combine with itself and cause even bigger waves! Where the water in the lake will soon just have a small wave spread over a large area, the pool water will still have really big waves for a while after as they bounce around and interact with each other. If you pop a balloon in an 'anechoic chamber' (basically like a pool whose walls absorb waves completely and don't let them bounce back) then you'll only hear that first smallish wave of pressure.",
"But bubbles don't make a loud sound when they pop?",
"Most of the answers I'm seeing are missing a key point. It's the tension. Here's a fun trick. Tape a section then stab the taped area. Quietly deflates. Edit: fixed a typo Edit again! Seems to be a lot of people under the impression I'm saying it isn't the pressure - it is. The point I'm making is that the tension is the root cause, it's why the pressure erupts. Without the tension, the pressure wouldn't erupt. Kind of like why plants are green - yes, it's because they reflect green light, but that only gives a small bit of the answer.",
"This might get buried but I have a related ELI5 question: why do latex balloons break into a bunch of pieces when popped instead of just letting air out of the puncture wound like other materials?",
"Here’s an example of a large balloon popping in slow motion. Tearing rubber snaps instantly. The tear doesn’t move through stable rubber, the moving rubber travels through the air faster than the speed of sound, creating anywhere from a very minor to a slightly bigger sonic boom. Video should start at 80 seconds in, slow motion is maybe 15 seconds later. URL_0",
"It doesnt. A balloon pop is actually quiet! What makes it loud is reflections and reverberation from the surroundings. Dont believe me? URL_0"
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7g5ex6 | How does google search work so quickly when there are so many web pages to search through? | Repost | explainlikeimfive | {
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"text": [
"Through the use of indexes. Just like a book might have an index of key words and what pages to find them; Google does the same thing electronically by creating an index of key words and what web pages to find them. It’s just that Google’s index is many orders of magnitude larger - which is made possible by computing power. The method in which Google creates its index and prioritizes which web pages (based on how often a key word shows up or how much traffic a site may get, etc.) is part of its ‘secret sauce’."
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7g9p73 | When documentaries are released that feature people doing highly illegal things (mainly drug selling/making), is there anything that prevents the police from obtaining their information from the journalists to arrest them? | Repost | explainlikeimfive | {
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"I know of some cases of people being arrested as a result of investigative journalism. For example, the TV program *60 Minutes* once did a feature about a man whose profession was to alter the odometers on cars, so that the cars would appear to have been driven fewer miles than they actually had been (thus enhancing their re-sale value). After the feature aired, the man was arrested. He foolishly had not tried to hide his identity. If journalists agree to hide someone's identity, however, they will generally be very insistent upon doing so, and for a very practical reason. If you cannot trust journalists to keep identities hidden, then many people will no longer be willing to grant interviews to journalists. There are cases of journalists who were ordered by a judge to reveal an identity and still refused to do so, even though they went to prison as a result. Many people who are engaged in illegal activities do want to present their point of view to the public. Also note that laws can change. Look at all the jurisdictions in which recreational use of marijuana is now legal. So just because something is illegal, does not mean that you cannot argue in favor of it."
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7gbn8r | Why does chewing mint gum make everything you drink feel like liquid nitrogen? | Repost | explainlikeimfive | {
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"Your mouth has receptors called TRPM8 that usually respond when there is low temperature in your mouth which tells your body \"Hey its cold!\". It does this by opening an ion channel and letting charged molecules flow through which creates an electric signal that goes your brain. Menthol or mint oil in mint gum can bind to these receptors, causing them to activate. This tells your brain \"Hey its cold!\" in your mouth when it really isn't. A similar mechanism exists for chillies, which is why they're \"Hot\". EDIT: Fixed name thanks /u/PM_ME_XBOX_MONEYCODE",
"I like to take advantage of this phenomenon; I often have refrigerator-cold water waiting after brushing my teeth or eating a mint!",
"It usually has nothing to do with the mint, most sugar free gum uses sugar alcohol (super sweet low calorie sweetener) to sweeten it. URL_0 “In addition to their sweetness, some sugar alcohols can produce a noticeable cooling sensation in the mouth when highly concentrated, for instance in sugar-free hard candy or chewing gum. This happens, for example, with the crystalline phase of sorbitol, erythritol, xylitol, mannitol, lactitol and maltitol. The cooling sensation is due to the dissolution of the sugar alcohol being an endothermic (heat-absorbing) reaction, one with a strong heat of solution.[11]”"
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7gcgxl | Why does microwaving food cause it to lose nutritional value compared to oven cooking? | Repost | explainlikeimfive | {
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"text": [
"Microwaves aren't magic. Food is not losing nutritional value by being microwaved - at least no more than if it were cooked in any other way. This is a myth."
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7gfu88 | why do French fries lose their crisp when microwaved? | Repost | explainlikeimfive | {
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"text": [
"Water in the potato turns to steam. Steam takes up much more space than the same number of particles of liquid water. So the pressure forces the steam out into the fried outer layer. When the outer layer cools, some of the steam condenses back to water."
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7gg6cd | The Freemasons | Repost | explainlikeimfive | {
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"text": [
"If you ignore all the assassin's creed/conspiratorial thinking, the Freemasons are just a fraternal organization. They're selective about who they let in and it's a conduit for networking between fellow Masons, and an excuse to do secret rituals and be 'in the know' about things that random plebians don't. Basically the adult equivalent of the cool kid's club. I did go to dinner at a Masonic lodge once and the food was outstanding"
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7gmyco | how batteries lose charge over time | Repost | explainlikeimfive | {
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"text": [
"First things first, you need to know how a battery works. Basically, two metals are submerged in an electrolyte solution, and separated from each other by something non-conductive. The electrolyte causes the metal to corrode, sort of how steel turns to rust. One wants to give off electrons in order to corrode, the other wants to take in electrons. Between the two, you can get a flow of electrons, which is electricity. Since they're separated by something non-conductive, they're only connected when you're using the battery. Like steel left in the rain, those metals are sitting in that electrolytic fluid. They naturally want to corrode. The process speeds up when you use the battery, but it's still happening when you're not. When charging a battery, you're basically reversing the process, using energy to break apart the corrosion on the metals so they can re-corrode when you need them to."
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7gyxzd | What is a Boltzmann Brain and do humans and other intelligent, self-aware organisms count as one? | Repost | explainlikeimfive | {
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"Say you had a box of marbles, seperated half blue and half red down the middle. Now we shake the box, what will happen? It will become more disorganized, obviously. Red and blue marbles will mix up as you shake it. Eventually, it will reach the point where the are completely mixed up, in equilibrium. Shaking more won't make any further large scale changes. Your headphones in your pocket are the same deal. Put them in nice and organized, walk around a bit, and they come out a tangled mess. What I just described is the second law of thermodynamics. Entropy increases, things become more chaotic and disorganized over time. Now, this law is just statistical though. There's no reason why a bunch of mixed up marbles couldn't seperate themselves as you shake, or why you couldn't put your headphones in your pocket tangled and then take them out nice and coiled. It's just very unlikely. If you considered every possible setup of the marbles in the box, there's way, way more than are disorganized than there is seperated. If you considered your headphones, there's many more ways they can be tangled than they can be nice and coiled. Now, imagine instead of a box of marbles we have a universe full of atoms. Now consider this: A bunch of atoms grouped up nicely into a galaxy, a nice planet around a star with the perfect conditions, and a few carbons atoms randomly self replicating molecules, and this resulting in trillions of very complex brains of conscious humans and animals all in the same place at the same time. Now consider this alternative: a soup of particles just randomly all over the place in equilibrium. Small changes happen all the time, but overall the universe is just the shaken up box of marbles and it looks more or less the same everywhere. Nothing special, organized, or complex going on, just a nothingness of chaos. Which is more likely? Well, possibly the second. So why are well all here? Maybe we're not. Consider the marbles again. Them all sorting themselves back out through shaking is so unlikely it will never happen. But a small little pocket of red marbles could certainly group up, that's not as unlikely. Maybe somewhere out there in that soup of random gas in equilibrium floating through a universe of nothing, a random bit of gas spontaneously becomes slightly organized and fakes a single consciousness. A single consciousness not made of atoms on earth as we (believe) we are, but one with the fake memories of all of what we perceive as existance now. It's certainly could be more likely than 7 billion of then alive right now on the same rock. That consciousness is a Boltzmann brain, a spontaneous consciousness popping out of small localized bit or organization in a universe in equilibrium. It's kinda like the \"everything is all just one true person's dream, and none of this is real\" type of deal, but the dreamer is a bunch of red marble atoms that randomly got together in a fully shaken up universe and formed their brain. So no, people and animals as they appear aren't Boltzmann brains. As we observe ourselves, we don't exist in a state of equilibrium, a fully mixed up box of marbles. We exist in a slightly mixed up box of marbles, and we feed off the nature of the organization of the environment to keep oursleves alive. Alive being a highly organized state. And in the process make the universe around us more disorganized, life makes a mess of chaos around itself to stay alive."
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7h94td | What is fire made of ? | Repost | explainlikeimfive | {
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"Fire is hot gas. That's all. In the case of a wood flame, it's hot carbon dioxide, carbon monoxide, and water vapor. Take wood which has carbon and hydrogen. Add oxygen + heat, and they recombine into CO2, H2O, CO + energy. The +energy adds more heat to the flame, keeping combustion going. Since Carbon Dioxide has lower potential energy than Carbon and Oxygen by themselves, if you combine them you get energy in the form of heat and chemical energy + a newly minted molecule of carbon monoxide. If you could capture an open flame in a glass vial and then measure whats inside of it, if it were from a wood fire you'd find carbon dioxide, carbon monoxide, oxygen (from incomplete combustion), water vapor, minerals like aluminum oxide (from minerals trapped in the wood) silica, and other minerals, and trace amounts of more exotic carbon compounds like waxes, tars, etc.",
"fire is flammable gas that is reacting with oxygen. when solid objects or fluids burn (paper, wood, oil, etc), the heat of the flame heats the object until it releases flammable gasses. fire is hot because the chemical bond between the atoms in the fuel and the oxygen contain more energy than the chemical bonds in the echaust gasses (usually carbon dioxide and water). the bright, red flame that is typical for candles, lighters or campfires is heated soot (small carbon particles), that is produced because there is not enough oxygen for an optimal burn process. the flame heats the soot and the soot starts emitting light. if you add more oxygen (like in a blowtorch), the flame gets hotter, but also paler and turns blue.",
"Fire is NOT a hot gas (no more than gas is a hot liquid anyway). Fire is a form of plasma, constituted of ionised atoms. URL_0",
"Gas. Solids and liquids don't really burn - they need to be in the gas phase. A flame is a mixture of gases. Take your common candle - the heat of the flame melts the wax, which is drawn up into the wick. It gets hot enough to vaporise into a gas, which is what you see burning. The colour of the flame is due to various types of atoms being 'excited' and their valence electrons oscillating from ground state to excited state, giving off various wavelengths of visible light."
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7h96re | What exactly is dust? Where does it come from and how the heck does it get everywhere regardless of what measures you take (e.g. covering things in plastic)? | Repost | explainlikeimfive | {
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"Soil, pollen and various other really fine particles which can be blown about by the slightest breeze, meaning that they can get almost everywhere.",
"The air isn't 100% clean. Microscopic particles are all around you at all times. You can see this by using a strong flashlight in a dark room. These particles consist of anything from human skin cells (which we shed daily), pollen, small human hair, microscopic space dust dust coming from space and even the roads around your house as cars break down the surface over time and that creates dust. All this enters your house when you walk inside, through vents or windows etc. and eventually settles.",
"I know that inside buildings a lot of dust is composed of small shed skin particles. I’m allergic to this specific form of “dust” and to dust mites who feed on it.",
"I've been on a ship with no land in sight for two months. We cleaned everyday top to bottom and there was always plenty of dust the next day.",
"Carried in to a building on people and their clothing, or entrained in air that infiltrates into the building. No normal buildings are air-tight, there is air moving in & an equal flow rate moving out, all the time. Carried in on air supplied intentionally for ventilation; clean room ventilation systems are complex and have several stages of filtration. Some places require you to wear a CSI disposable suit and shower on the way in. If you want to keep dust down, the answer is a positive pressure ventilation system, so that filtered air is supplied and more air leaks out than leaks in. There was a study done years ago ( I can't quote a source, I don't recall where I read it) examining various energy saving heating systems. Positive pressure ventilation with heat recovery was effective *IF* you included savings in cleaning labour (vacuum cleaning) and materials.",
"We actually gain dust from space as well. The Earth gets heavier every year because of it... I want to say 2 cm roughly per annum.",
"I'm more interested in how dust gets 'recycled' back into the environment. Something has to be getting rid of said dust or else our entire world would be one big dust bunny by now. Obviously we can physically combust it to transform it into gases, but what natural phenomena gets rid of it?",
"A huge amount of the dust in your bathroom is from toilet paper. Any room with cat litter box is going to quickly become covered in clay dust",
"Someone had asked one of my Science professors this specific question back in college. I believe that they said that it was the object breaking down. Objects simply break down over time and the result is dust.",
"While I was in bootcamp, no one had any other clothing except what the navy provided. I noticed that every spec of dust in our berthing was blue. We spent a lot of time sweeping and my intuition told me that \"if we sweep the same hall 3 times a day, at some point we'd just be sweeping clean hallways. NOPE! There was always this blue dust, it gathered together like tumbleweed. It was from all of our uniform items, the blue fabric rubbed off from so many of us peons that it gathered in large balls everywhere. It wasn't just new uniforms, because even 6 weeks into our stay we were still seeing no reduction in this blue fluff. It came from 100's of \"sailor's\" uniforms, like when the uniform rubs against itself, between the legs and arm pits.",
"It’s dead skin and dust mite faeces. They shit all over us and we shed our shit laden skin everywhere. Some things are best left unknown.",
"On top of the various terrestrial sources pointed out Earth also get a tiny amount of dust and tiny particles falling in from space. Estimated to about 60 tonnes worth every day. It would be a sizable heap if it all fell in one place but obviously it's spread very thinly across the whole planet so it's pretty much undetectable by the time it reach the ground (they estimate the amount by collecting samples from high altitude balloons and such).",
"Take a flashlight, and shine it in a dark room. Look at the beam and you'll see lots of floating particles. Some of it can be pollen, skin flakes, dirt/soot. Those particles will eventually settle on top of a nearby surface."
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7he2h1 | Why when were on the phone do we start to walk around aimlessly | Repost | explainlikeimfive | {
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"It's based on primal instincts. When we are on the phone we are distracted audibly (not listening to our surroundings). In our past generations this could possibly be dangerous because of predators. So subconsciously our brain likes to walk around and check the surroundings while our conscious mind is occupied."
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7hguy3 | Why can we pop our ears, and why can we hear much better when we pop them? | Repost | explainlikeimfive | {
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"You can hear things because there is a thin “drum” in your ear that sounds make vibrate. Your brain feels those vibrations and you experience it as sound. Air cannot go through that ear drum, just like a normal drum. Air gets to the other side through a different hole deep inside your head. The amount of air around you depends on how high up you are, the higher you are, the less air. If you go up or down quickly, the different hole that goes to the other side of the ear drum doesn’t let air through quickly enough, or at all if it gets clogged with goop, and the outside part of the drum (that you could see by looking in your ear) has a different amount of air pushing on it. Your brain knows how sounds work when both sides have the same amount of air, and gets confused when they have different amounts. When your ears pop, that is air moving into the inner part of your ear and making the pressure the same. Now you hear like normal again!",
"The ear drum needs air pressure on its two sides to be similar in order to vibrate when sound waves hit it. Behind each ear drum is the Eustachian tube that runs from the middle ear to the back of the throat. It is there to equalize the air pressure inside and outside the ear drum. You can feel the tension on the ear drum when it is stretched due to different air pressure inside and outside the ear. For example, when you go up in a plane or drive up a tall mountain, the outside of your ear has lower pressure but the inside of your ear still has sea-level pressure. Ear drum is stretched outward. Until you yawn, sneeze or otherwise open your Eustachian tube. Going under water more than six feet causes the same sensation, but here the outside pressure is higher that the middle ear pressure, stretching the ear drum inward. Most medical drawing illustrate the Eustachian tube as if it were a rigid pipe. It is more analogous to a sock, open when on your foot, but closed when lying on the floor. When you pinch your nose and blow (a \"Valsalva\" maneuver), you temporarily inflate the Eustachian tube, opening it up and allowing pressure inside and outside the ear to equilibrate. The Eustachian tubes can get clogged. Babies, like every other part of their body, have tiny Eustachian tubes that get blocked with mucus easily (during a common cold) ... that's why one is more likely to get ear infections when younger, less often when older, when the Eustachian is bigger and harder to clog. Although some adults have small Eustachian tubes just via bad luck."
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7hk208 | The game of cricket | Repost | explainlikeimfive | {
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"I'm going to assume you know how to play baseball, because I will use that sport as a comparison. In cricket, there is an outfield team and batting team just like in baseball. However, when a person is at bat, they keep hitting until they are out. Instead of three outs, there are ten. Also, in some types of matches, there are things called overs. An over is six pitches (iirc). The defending team switches bowlers (pitcher) every over. Anyways, some games have a limited amount of overs. So, even if the batsman doesn't get out, the attacking team retires once they reach the maximum amount of pitches. Innings work the same way, but can last for hours, even days. Depending on the type of game, they only play a couple of innings. A person can score multiple runs for each at bat. The bowler throws the ball to the batter and the batter tries to strike it. In cricket, the batsman can hit the ball in any direction, including behind him; there are no foul balls. When he hits the ball, he and another batsman (think of him as the next batter up), run between the wickets. Instead of running around four bases, think of it as the two of them running between 1st and home plate over and over again. Every time they make it across, that's a run. If the batsman hits the ball, and it rolls out of the filed, that's a called a four. It is four automatic points; it is similar to a ground rule double. If the ball is hit directly out of bounds, that's a six (six points); it is a home run. Getting the batter out is very similar to baseball. If the batter strikes to ball and it is caught in the air, that's an out. If the batters are running between wickets, but the defense team breaks the wicket before the batter is in the batting box, that's like tagging someone out at the base. If the bowlers throws the ball and it hits the wicket, that's like a strikeout, but only with a single strike. There are many more technical rules, but that is the gist of it."
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7hmd8m | How does “activated charcoal” work and why has it become so wildly popular in beauty/cosmetic products? | Repost | explainlikeimfive | {
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"\"Activated charcoal\" is carbon - which, you know, is what charcoal is made out of, mostly. They press it into smaller bits with more surface area. Carbon like that has a lot of porous area where chemical *adsorption* can occur. Adsorption is like absorption, kind of, in that your material is \"sucking up\" something from a liquid or gas. In the case of adsorption, atoms and molecules stick to the surface area of your material. Charcoal, particularly activated charcoal, has a *lot* of surface area, so it can adsorb a *lot* of stuff and it can do it quickly and efficiently, and also cheaply. ~~That's why they use charcoal to pump your stomach when you have alcohol poisoning. The carbon sucks up all the alcohol, then they remove the saturated carbon from your stomach, bringing the alcohol with it. What carbon remains to go through your digestive tract contains the alcohol so you can't absorb it into your blood.~~ [^^Or ^^not ^^maybe?]( URL_0 ) ^^I ^^dunno, ^^point ^^is ^^it ^^sucks ^^up ^^poisonous ^^stuff ^^in ^^your ^^stomach. It's also used in aquariums to suck up waste in the water so it can be removed when you change your filter. It's especially good at removing heavy metals, which are sometimes present in your water at concentrations that are not high enough to hurt you but high enough to hurt your livestock. Similarly, it's used in water purification systems (like your Brita filter) to similarly suck up some stuff in your tap water that you are trying to filter out. EDIT: And some gas masks, and industrial air pollution scrubbers, and a number of similar filtering applications. It's quite good at actually sucking up toxic chemicals. Just, you know...not out of your face. That tendency to suck up heavy metals has created a mystique about it, that it sucks up \"toxins\". If it can purify your water, why not purify your skin? It can suck up \"toxins\" out of your face! (Pro tip: it doesn't.) Edit: when they make you swallow charcoal for a pill overdose or swallowing poison, *it does nothing to the drugs or poison in your blood*. If you still have some left in your stomach, it soaks that up so that your OD or poisoning doesn't get any worse. What's in your blood is still there and has to be dealt with in other ways.",
"Serious question. Does activated charcoal brushing powder actually do shit? On amazon i always see before and after pictures. I figured your average joe would just upload two seperate images. But these people always have a single image divided up. Seems to professinal. Seems fake. Not buying it. Seems like its all a scam.",
"Take a piece of wood. Now heat it to very high temperatures in the absence of oxygen (no combustion) - this creates a very pure carbon, a charcoal. Now, expose this to an \"activating\" agent (like carbon dioxode) that creates a very porous structure that gives it a lot of surface area. The more area you have means you can adsorb (sort of like a sponge) more contaminants. Activating also alters the surface such that it is more attractive toward, specifically, organic compounds. Examples of organic compounds that would be of interest include oils and grime in your skin, tea/coffee stains on your teeth, and taste/odor compounds and organic contaminants in your drinking water (think fridge filter). Activated carbon is in the adsorbent family of treatment options. There are other options, but carbon is cheap and it can be sustainable if one uses resilient sources like bamboo or waste products such as coconut shell. A great invention would be turning waste plastic into activated carbon, something many are working on! *How much surface area? The amount of AC that fits in your palm (or half a banana, if you must) is equivalent in surface area to about five football fields.",
"Carbon is porous and acts like a filter that small tidbits will stick to. It doesn't actually do anything, for your skin, better than washing. The reason it's so popular in skin care is because of marketing.",
"Can anyone confirm if this actually works for beauty products? Mostly interested in the effectiveness of whitening your teeth with it? I always heard baking soda works but then my dentist told me it scratches your enamel (which doesn’t heal) because baking soda is too rough and not ground up finely enough. So then, what are the cons of charcoal teeth whitening, if it does work?",
"So, lots of comments asserting that activated charcoal doesn't actually adsorb toxins off the skin. 'Toxins' is, of course, a nebulous, sort of meaningless term in this context, so that doesn't surprise me. But does charcoal in a skin-care product really not adsorb things like the bacteria that can cause ance, or excess sebum and oil that can block pores and cause breakouts? In my own experience, some charcoal face-wash scrubs I've tried were quite potent at cleaning oily skin. Maybe even too strong.",
"Unlike a fine silica gel which attracts very polar oils and chemicals, charcoal (carbon) is very non polar and attracts very non-polar oils and chemicals to it, including some stains as well. Pharmaceutical companies use it while making certain drugs to make their pills more uniformly white since people would rather take a white pill than a tan or brown pill. For cosmetics I assume for cleaning purposes it adds a benefit of adhering to and eliminating certain otherwise stubborn lipids or oils that don't clean up well with soap and water; also maybe to eliminate the oil built up in natural creases in the skin crafting the illusion that someone looks younger due to their wrinkles being less prominent. Wanting to look younger is a thing right?",
"The charcoal serves to absorb toxins and stains but will not actually whiten your teeth. Teeth color comes from the color of “dentin” which is a layer underneath the surface of your teeth. Things like whitestrips will bleach/stain the dentin white. Almost everyone has naturally off-white/yellow natural teeth. Active charcoal will just get your teeth as “white” as your teeth naturally are, but won’t give you that Hollywood smile.",
"Taking charcoal pills regularly is very much NOT recommended outside of prescribed medical use. If you are on any kind of daily medication, activated charcoal can prevent your medication from being absorbed properly - antidepressants, birth control, antihistamines, etc, can all be rendered less effective by taking charcoal along with your prescribed dose of medication. Furthermore, taking activated charcoal internally has never been shown to provide any medical benefit as part of a daily routine, and can actually be harmful if taken with food as it may prevent essential nutrients from being absorbed. It's just another marketing fad selling you snake oil. Don't be fooled!",
"Activated Charcoal is porous and it attaches to other molecules. It is used to neutralized poisons in an Emergency room. The Efficacy on it's use everyday for hygienic reasons is most likely that it is has harmful effects. I would not purchase these products. Activated Charcoal would make other topical and internal medicines less effected.",
"Regular carbon (charcoal) has small nooks and crannies that capture impurities. Activated carbon is charcoal that has been crushed, soaked in acid and baked. This process makes the carbon bits smaller and the are now microscopic if not smaller nooks and crannies that can now capture even more impurities. Like a billion times more crevices and also captures smaller impurities. Not sure about it being in makeup though.",
"Activated charcoal: Its a marketing term for \"activated carbon\" which is a processed form of carbon thats more poreous than other forms of carbon, thus allowing certain thigns to be absorbed into it easier. What it is used for in cosmetics: It has been in use for hundreds of years and has become more available in modern times for use in hospitals etc. It can be used as a cleanser, mask, and many other products. Why is it popular: Marketing has rediscovered this term for use in cosmetics. People who don't know any better are paying a few extra dollars on something that is not necessarily more effective than other cleansers. People will buy anything that are marketed to make you look younger without really doing any solid research.",
"Is this why my whiskey says triple-filtered with active charcoal?",
"Is it okay to use charcoal toothpaste very sporadically? Like weeks before another use?",
"As a layman, where do i read stuff about what's really good for our health/skincare? is there a kind of honest ebook i could look up to? I highly sceptical of those product marketing or people claiming a particular compound is secret for everlasting beauty.",
"Wendy Zuckerman did a good show on this on [science vs]( URL_0 ). It has become wildly popular in beauty/cosmetic products because it's easy to make wild claims that are plausible-sounding enough to get people to part with their money. It is used medically to treat certain poisonings and overdoses following oral ingestion. If you can convince people that their self-perceived flaws are caused by something as intensely unlikable as \"toxins\", you can easily convince them to spend their money on your activated charcoal. It's benign enough not to hurt you, so why not? The reason it's effective for things it's *truly* effective for is that the process of \"activating\" it gives small particles a large surface area that allows it to absorb a much larger amount of contaminants than it would otherwise, so you can get away with using much smaller amounts."
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7hv1wu | why do so many stores in the U.S. sell things with a .99 at the back? E.g. 9.99, 1.99, 999. Why not just use 10.0, 2.00, 1000? | Repost | explainlikeimfive | {
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"It’s a technique used to make the average person think at a first glance that $1.99 is not $2 and is only $1. Sorry if this is explained bad, I heard this from my 7th grade teacher",
"This is a classic marketing trick that makes you think the item is cheaper than it actually. Your subconscious latches onto the first digit and your purchase seems more justified despite the almost insignificant change in price. Also in the U.S. the tax isn't included in the sales price so the total price is usually over the even price anyway (Ex: $10.08"
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7hx1a2 | how can a device be turned off for years, but when it's turned back on again it still knows the date? | Repost | explainlikeimfive | {
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"Electronic devices have a clock they use to keep time, and a battery to keep track of the time. So your PS4 knows what the time was last time it was on and how long it's been since then."
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7hzhud | how hacking works, since it seems to be misrepresented in most movies? | Repost | explainlikeimfive | {
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"Hacking refers to a wide variety of activities. You might as well be asking \"how theft works.\" Generally speaking: 1. You perform reconnaissance on the target. Gather as much information as you can. 2. You identify weaknesses or vulnerabilities. 3. You develop a pan of attack to exploit those weaknesses and vulnerabilities. 4. You execute the plan, taking measures to avoid notice or leave a trace. What is misrepresented is that a lot of hacking research. Imagine filming someone doing a book report for school. A lot of hacking involves less-than-technical methods. Such as social engineering and tried-and-true real-world techniques like dumpster diving. For parts of hacking that involves software much of it is automated. Most tools used don't have flashy interfaces, nor is a real-time back-and-forth battle of wits between a hacker and IT security.",
"I work for a computer security company and deal with this kinda stuff all day, so here's the short version. There's two ways to do it, essentially. Trick a human, or find a mistake in the way a machine works and take advantage of it. In the case of human tricking, this is phishing emails asking for usernames/passwords, \"hey download & run this totally-not-a-virus-thing please\", \"hi I'm bob from Microsoft please give me your password for a security check thanks\", and other such scams. Frequently, that works just fine. You can also just try logging into websites and other services and hope someone set their password to \"password.\" And yes, that frequently works just fine too! No enormous technical skills required! As for \"real\" hacking... a lot of websites, services etc rely on the same basic components. Linux & Windows are super-common, web server programs like Apache or Microsoft IIS... these tools are all working behind the scenes to power the modern web. So what someone does is gets their hands on one of these (not hard) and starts poking around to find an \"exploit.\" A good example of an exploit was the [heartbleed bug a few years ago, which xkcd made a comic explaining.]( URL_0 ) Basically, they discovered a bug that would make OpenSSL (a very common program) cough up too much information. Then, now that you KNOW about this exploit, you use it against real-world servers run by actual companies, in the hopes that one will unintentionally spit out somebody's password. Other exploits often let you run code when a server shouldn't be letting you run code. So you build a little package designed to get run by the exploit, and once that lil package gets to run, it sits and listens for you to give it more commands to run on the remote computer, letting you change passwords, access lists etc so you can login for real. And that'd be a type of virus! There's a lot to cybersecurity but hopefully this helps scratch the surface"
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7i45d5 | How was the internet made? Like how did they discover coding, etc? | Repost | explainlikeimfive | {
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"Computers predate the internet by several decades, but the origins of the internet can be traced back to a US Military project in the 1960's called Arpanet. They wanted to see if they could get computers to communicate with each other. The first data packet was sent from a computer at UCLA to one at Stanford in 1969. The technology that came out of Arpanet ultimately led to the commercial internet."
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7i4j0n | What is a stroke, and what causes it. | Repost | explainlikeimfive | {
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"Your brain requires an immense amount of oxygen and energy to continue functioning. And it requires it nearly continually. A stroke is a blockage of the blood flow to the brain. This results in the parts of the brain that the blood is flowing to to become negatively affected. Usually this is on one side of the brain or the other, which is why you see unequal movement or strength in one side of the body. As blood flow continues to be restricted, brain damage can occur, which is why responding to a stroke quickly is so important. Don't forget FAST! FACE (Ask the potential victim to smile, if it is uneven, that's the first sign) ARM (See if one arm is weaker than the other. The best way is to ask them to hold their arms in front of them and level. If they are unlevel, that's another sign.) SPEECH (If their speech is slurred, that might be the first sign you notice. If you're not sure, ask them to talk a bit.) TIME (If you think a stroke is possible, call emergency services right away. Better to be safe than sorry in a stroke.) There are a few other quick checks: Have them stick out their tongue straight forward. IS it uneven? If so, it's another sign. Also, you can have them cover one eye. If they say their vision is suddenly worse with one eye, it is another sign. Strokes don't just affect older people. I've lost two friends in the last year to cardiovascular disease, and both were under 40.",
"A stroke is when part of your brain has no blood circulation. This causes parts of your brain to die. Strokes can be caused by blood clots or other blockages blocking off the way of the blood flow or even bleeding in the brain (blood is just pooling around the brain instead of going where it needs to go)."
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7i8p53 | How does radiation kill cancer cells without mutating normal cells? | Repost | explainlikeimfive | {
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"They use gamma rays, which largely pass through the body. Then, they fire those rays in multiple bursts from multiple directions, each aimed at the tumor but from a different direction. This ensures, that only the tumor is hit multiple times, the rest of your body is only hit once. Thus, the amount of radiation absorbed by the tumor is much higher than that absorbed by healthy cells.",
"It doesn't. Radiation used to fight cancer is dosed high enough to kill all cells, cancerous or not. The idea is to concentrate it into areas where the cancer is rather than healthy areas."
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7i8sfs | Last night I woke up and was unable to move for a few seconds. It felt like something was holding me down. I couldn't even speak. Then a couple seconds latter I was completely fine. Is there a name and explanation for this phenomenon? | Repost | explainlikeimfive | {
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"dqwxk3u"
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"text": [
"Sleep paralysis is a temporary inability to move or speak that occurs when you're waking up or falling asleep. It's not harmful and should pass in a few seconds or minutes, but can be very frightening."
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9
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7ia59y | what exactly do antioxidants do? | Repost | explainlikeimfive | {
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"text": [
"Practically all cellular processes have a needed initiator and a consequential product. These cellular processes are chemical processes with a lot of variation going on. They don't also go perfectly. There accidental or uncontrolled products which can form a chemical product called a radical - a compound missing an electron. This is a HUGE issue, because compounds want to be stable, and missing an electron will make that compound react with whatever is closest to it, that fits some properties it likes. Its a little like, a product of one of these reactions is a firecracker that destroys a functioning unit in your cell when it touches it. Not good. These are called oxidized species - its just terminology. A way to remove this issue to is to add a reducing agent - a compound which will give up an electron, or even form a stable compound with an oxidized agent. You would like these to be safe to our cells regular function, and to interact with the radicals. If you can give your cells antioxidants, you can both prevent the destruction of a functional unit, and create a safety buffer so that if one does happen, it'll react with something not-critical. Thus, they are good for us because they protect our cells from the inevitable damage which happens due to the small chemical errors in our natural system. This allows the cells to live longer and not have any complications, improving our over-all health."
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7iabpj | Who decides when (for example) the Canadian dollar goes up and down in worth? And how does that work? | Repost | explainlikeimfive | {
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"text": [
"Foreign exchange markets. Let's pretend I have 100 USD and 100 CAD. At the moment I write this it's 100 CAD = 77.8 USD. If I wanted to have only USD, I am selling my 100 CAD to a foreign exchange service to receive 77.8 USD minus some sort of exchange service fee. Let's now pretend I have 100 billion USD and 100 billion CAD. Let's say I sold the 100 billion CAD. I would likely get significantly less than 77.8 billion USD, because the act of my selling this quantity of CAD for dollars has significantly increased supply of the canadian dollar while simultaneously increasing demand for US dollars. The exchange rate would move by a good amount, so that 100 CAD would be worth significantly less than 77.8 USD. That's how foreign exchange markets work - the relative demand of currencies. Why some currencies are in demand and not others is not something really answerable in a ELI5 way."
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7icdpo | What exactly happened during the Enron Scandal in 2002? | Repost | explainlikeimfive | {
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"In trying to make their oil company cool, they wanted to think of themselves as a trading firm. So they started doing things like trading energy or Internet traffic. Because of their mindset, all they cared about the cash on the books at the end of each quarter. In order to get cash on the books when they had none, they devised many accounting tricks to increase the cash on the books and decrease losses. Not in reality, just in reporting. For example, they would sell portions of loss making subsidiaries, where there was some weird rules like if they sold a tiny fraction of the subsidiary, then they won't be the owners and not have to report the losses. Something like sell 7% of a electric plant and not have to report loses of that. In addition, the would write down all potential gains in the first year of contract. Like if they had a contract in 1997 to provide water to a region for 7 years, they guessed your much money they would make from that over the seven years and book all the potential profits in the first year. Regardless if they ever made any money or profit, they didn't go back and revise down. So it looked like they made a lot of money. Back to the selling assets, their CFO, while CFO, started a hedge fund which would be the place that Enron would sell their fractions troubled assets. As CFO, he was able to negotiate both sides of the deal, and because Enron was desperate to unload losses from their sheets, they would sell at a very bad price for Enron, and a great price for the hedge fund. Many of the investors in the hedge fund were employees of Enron, or bankers who wanted to do business with Enron (the CFO would give them preferential treatment). Check out book and or documentary \"smartest guys in the room\"",
"They started hiding their losses in crazy accounting methods and then lost more and then did crazier accounting tricks.",
"The energy markets were deregulated. Essentially, what that means is that instead of there being fixed rules on power generation and sales, power could be bought and sold by speculators on a market. So essentially, what used to be a system where a power plant might sell energy to the grid at a fixed price, there was a constantly fluctuating price of energy being bought and sold. So at 8am maybe energy is only $0.12/kwh, but maybe at 8:30 it's now $0.25/kwh, and maybe for 3 minutes at 6:23pm it's $5/kwh. Electric companies have to pay the \"market rate\" to provide the power. Because buying and selling energy on a market used to be governed by rules, and now it was not, Enron could do all sorts of things to make money. They could lock all the power producers into markets they owned, forcing them to sell at the constantly changing rate to electric companies. So Enron could then make money on each little transaction, like a stock market might. But because there was no regulation, Enron could act like a buyer of energy and a deliverer of energy if it wanted. So Enron could make money by promising to buy natural gas at some rate (say $1), and then if the market went up, then they could sell it at $2, still paying the producer the agreed upon $1. What happened is that they started using fishy accounting practices. For example, if they were buying 1000 CCFs of natural gas at $1 today and next year selling it at $2, then they'd write on today's books that they made $1000, even though they never sold it next year. When next year rolls around, they have a problem if gas is still $1. Obviously, that can only last so long before it's discovered, but the guys at Enron were really pretty smart, and so they were making tons of money other ways, and also coming up with more creative ways to make it look like Enron was still making money on these contracts that seemed like they were worth more than they really were. The most creative of these was to create another company who was \"buying the loss\" which essentially allowed them to show that Enron was doing good, but this other company had all of those -$1 losses from the market not rising like it was promised. That company was hidden from all the investors, so it wasn't obvious that it was a part of Enron. Eventually, like all houses of cards, it was discovered that Enron didn't have all the money it claimed it did, and then it went bankrupt - but that disrupted companies who were buying their energy on their market (electricity, natural gas), which is why it turned into such a big deal. It was also difficult as Enron was a Fortune 500 company that would have been thought to be too large to fail so suddenly."
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7igb6i | Why has it been so difficult to unseat the big ticket sellers (like Ticketmaster) and start a new ticket system? | I feel like people have been hating on Ticketmaster since they existed, but I have never seen another company unseat them, or band/label change the way they sell tickets. I mean, we seen Uber disrupt the taxi system, which was once considered unchangeable. Any thoughts? | Repost | explainlikeimfive | {
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"What would you have to do to displace Ticketmaster? 1) Start a new company to serve the same market, this would require a significant capital investment. 2) Convince venues to break their highly profitable contracts with Ticketmaster - or at least switch to you as renewal time. This would require taking a smaller cut than Ticketmaster takes. 3) Convince consumers that your service doesn't have the same problems as Ticketmaster. You still can only sell the tickets allocated to you, so all those \"good seats\" the promoter and venue reserve for themselves aren't available for your customers. If you can't solve the \"didn't get the tickets I wanted\" problem, you're going to do it for a smaller fee?? 4) Demonstrate to the marketplace that you can sell tickets as fast as Ticketmaster, which will require quite a bit of IT. Your basic concept is to make a huge investment for less return and sell it at lower prices - that's not disruptive, it's going out of business. If you do well for a while, your investors are going to get a purchase option from Ticketmaster, and you're going to be sold out to them. Think about what you hate about Ticketmaster - it's not something that can be fixed because Ticketmaster is a very efficient company. People just like to complain that they can't get to sit down front.",
"Yo ho ho! Yer not alone in askin', and kind strangers have explained: 1. [ELI5 - How is it that Ticketmaster seems to have a total monopoly over all things tickets, or, why does it cost $18 to mail me tickets? ]( URL_3 ) 1. [ELI5: Ticketmaster ]( URL_1 ) 1. [ELI5: What necessary service do companies like TicektMaster provide? ]( URL_5 ) 1. [ELI5: Why isn't there a viable alternative to Ticketmaster? ]( URL_7 ) 1. [ELI5: Why do so many events sell tickets through ticketmaster instead of through their own website? ]( URL_0 ) 1. [ELI5: How does event ticketing work, i.e., What economic principles allow Ticketmaster to charge such high fees for such an easy task? ]( URL_8 ) 1. [ELI5: Why doesn't Ticketmaster have any real competition and why isn't it considered an illegal monopoly? ]( URL_2 ) 1. [ELI5: How is Ticketmaster able to avoid Monopoly laws? ]( URL_6 ) 1. [If everyone hates Ticketmaster, why doesn't it have any real competition? ]( URL_4 )",
"The [latest episode of Freakonomics Radio]( URL_0 ) speaks directly to this topic. I haven't listened to the whole thing yet, but the gist I've gotten so far is that Ticketmaster takes the brunt of the bad PR for charging fees, but sees very little of those fees. Also, there is the \"fact\" that live show ticket prices are SEVERELY under-priced. If you're interested in a real answer to this question I recommend listening to the podcast."
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"https://www.reddit.com/r/explainlikeimfive/comments/kq5ys/eli5_why_doesnt_ticketmaster_have_any_real/",
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7iggza | How do they decaffeinate coffee and tea? | Repost | explainlikeimfive | {
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"Yarr! Yer not alone in askin', and kind strangers have explained: 1. [How is the caffeine removed from decaffeinated tea and coffee? ]( URL_6 ) 1. [ELI5: How do they decaffeinate coffee and teas? ]( URL_2 ) 1. [ELI5: How do they take the caffeine out of tea and coffee to make decaffeinated versions? ]( URL_4 ) 1. [How do they make decaffeinated tea and coffee? ]( URL_3 ) 1. [ELI5: What is caffein and how can it be removed from coffee? ]( URL_8 ) 1. [ELI5: How is coffee decaffeinated? ]( URL_1 ) 1. [ELI5: How do they decaffeinate coffee? ]( URL_0 ) 1. [ELI5: How do you decaffeinate coffee. ]( URL_7 ) 1. [ELI5: How do they decaffeinate coffee? ]( URL_5 ) 1. [ELI5: Decaffeinated coffee ]( URL_9 )"
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"https://www.reddit.com/r/explainlikeimfive/comments/2nslza/eli5_how_do_they_decaffeinate_coffee_and_teas/",
"https://www.reddit.com/r/explainlikeimfive/comments/1v7f9y/how_do_they_make_decaffeinated_tea_and_coffee/",
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"https://www.reddit.com/r/explainlikeimfive/comments/5qhy0i/eli5_how_do_they_decaffeinate_coffee/",
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"https://www.reddit.com/r/explainlikeimfive/comments/2b289f/eli5_how_do_you_decaffeinate_coffee/",
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7ih6ch | Why do our noses run when we are outside when it is really cold? | Repost | explainlikeimfive | {
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"text": [
"I remember asking my parents this when I was little, and they said something like the nose is trying to keep itself warm and moist, because cold air is often dry, and when your nose gets really cold it can't tell if it's dry or not. I'd be interested to hear from the pros if that's the case or not."
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7ijqbj | Why does wind chill exist? | Repost | explainlikeimfive | {
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"Ever put a tea bag into water? Notice how the tea sticks close to the bag at first? But then you stir it and the tea goes everywhere. Same with body heat. It dissipates but stays close to you until the wind blows (especially under your clothes). The wind blows that heat away and therefore the temperature right next to your skin gets colder even though the temp of the air is the same"
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7ikquq | How does a car know how fast it’s going? | Repost | explainlikeimfive | {
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"Ahoy, matey! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: How does a car know how fast it's going? ]( URL_0 ) ^(_11 comments_) 1. [ELI5: How do cars know how fast they're going? ]( URL_3 ) ^(_16 comments_) 1. [ELI5: How do cars know how fast they are going? ]( URL_9 ) ^(_8 comments_) 1. [ELI5: how exactly does a car's speedometer work? ]( URL_6 ) ^(_7 comments_) 1. [ELI5: How does a speedometer know how fast you are traveling? ]( URL_7 ) ^(_4 comments_) 1. [ELI5: How does a car measure it's speed to show up in the speedometer? What happens if the car is replaced with wheels of different diameters? Does it matter? ]( URL_1 ) ^(_17 comments_) 1. [ELI5: How does car's speedometer & tachometer work? ]( URL_4 ) ^(_13 comments_) 1. [ELI5: How does a speedometer work? How are they able to adjust it to mph vs kmh? ]( URL_5 ) ^(_7 comments_) 1. [ELI5: How does a cars speedometer work? ]( URL_8 ) ^(_19 comments_) 1. [ELI5: How do speedometers work? ]( URL_2 ) ^(_5 comments_)"
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7ilwhu | Why do some people have better cold or heat tolerances than others? | Repost | explainlikeimfive | {
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"Because we're tougher. Nah it's a combination of a few things but weight, circulation and practice/familiarity are major factors. If you don't keep your heating on all the time you just get used to it"
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7imgg2 | Why did 20th century bombs dropped from aircraft usually made high-pitched, loud whistle-like sounds while falling? | Repost | explainlikeimfive | {
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"The whistles were purposefully attached to the bombs. Their purpose was to weaken enemy morale and to enhance the intimidation of dive-bombing. Look at the Stuka dive-bomber, a similar case. What other purpose did it's sirens have? As far as warning the target, it's too late to get to safety once you hear the whistle if you're not there already (bombs fall fast). Not all bombs were equipped with whistles, but they still all made noise as they fell due to air displacement (just not the famous whistling sound). This ( URL_0 ) page gives one example of bombs that were purposefully fitted with whistles.",
"Because it's terrifying - imagine being on the ground and hearing the whistle. You know that a bomb is coming, but there is no way you can see it, and even if you could working out which direction its moving would be impossible. The modern sniper rifles deployed in Iraq got a similar fearsome reputation because of their extreme range - you'd be minding your own business and a wall behind you explodes before you even hear the gunshot. Where did it come from? No idea. What can I use for protection? Nothing, the fucker goes through walls and sandbags."
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7in216 | What causes that feeling in joints that makes you want to crack your neck? Why is cracking your neck so satisfying and addicting? | Repost | explainlikeimfive | {
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"Yo ho ho! Yer not alone in askin', and kind strangers have explained: 1. [Why does cracking / popping your back feel so good? ]( URL_2 ) ^(_47 comments_) 1. [ELI5: Why does cracking your knuckles/back/neck feel good? ]( URL_1 ) ^(_29 comments_) 1. [ELI5: why does cracking your neck and fingers feel so good? ]( URL_8 ) ^(_4 comments_) 1. [ELI5: What cracking your neck actually does. ]( URL_0 ) ^(_2 comments_) 1. [ELI5: What happens when you pop your neck and is it dangerous to do to yourself? ]( URL_6 ) ^(_5 comments_) 1. [ELI5: What exactly happens when you \"pop\" your neck or any other body part? ]( URL_7 ) ^(_26 comments_) 1. [ELI5:What happens when I crack my neck/back, and why does it give me relief? ]( URL_5 ) ^(_2 comments_) 1. [ELI5: Why do we feel relief when we \"crack\" our knuckles/joints? ]( URL_3 ) ^(_20 comments_) 1. [ELI5:What happens when I crack my neck? Why does it feel better than just stretching? Is it harmful or helpful?? ]( URL_4 ) ^(_1 comment_)"
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7ip7ke | the difference between 4 Wheel Drive and All Wheel Drive. | Edit: I couldn’t find a simple answer for my question online so I went to reddit for the answer and you delivered! I was on a knowledge quest not a karma quest- I had no idea this would blow up. Woo magical internet points!!! | Repost | explainlikeimfive | {
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"4WD and AWD roughly do the same thing but in different ways, the car is proving power to all four of its wheels. The difference is how that power is divided between them. An all-wheel-drive car can allow each wheel to turn at a different rate, while a four-wheel-drive car generally has its wheel all turning at the same rate. This 4WD set up is better for offroad driving, but can cause problems in city driving, where the inside wheels need to turn slower around a corner than the outside wheels do. Because of this, a lot of 4WD cars are designed to be able to switch to rear-wheel drive when the 4WD is not needed. EDIT: RIP my inbox",
"This is actually a very complex question with a very complex answer but by the time you're done with this comment you will understand it as well as anyone. So buckle up, tape your eyelids open, and go brew a bucket of coffee. To begin you need to have a good idea of how a differential works and what it is. As usual in the car world, the best way to learn is to watch a video from the 1930's (really, it is, I swear). Namely [this one]( URL_0 ). You're back? Good. That's what we call an open differential. It's the most basic type of differential. When you get stuck in the snow or mud and one wheel spins like mad and one does nothing at all, that's because there's an open differential. A ***limited slip differential, or LSD***, is a differential that allows the wheels to only turn at a limited range of different rates. If one starts to spin too much faster than the other, the differential sends power to the other wheel. Some LSD's are clutch pack type, where the speed imbalance causes the spinning wheel to be braked against the inside of the differential housing using a clutch pack. You don't really need to know how that works mechanically, but understand the effect is the same as if you were to apply the brake on just that wheel (a thing some cars actually do- brake based torque vectoring, which we'll get into later.) Others are of the \"torsen\" type, which is short for \"torque sensing.\" It uses magic, I think, but if you're in a torsen equipped vehicle, and one wheel is spinning uselessly, you should try lightly applying the brakes, as this will cause the torsen differential to send power to the other wheel, using magic. Anyone who's watched my cousin Vinny could have probably skipped the last two paragraphs. A ***locking differential*** is an open differential which has the additional ability to be locked so that both wheels turn at the same rate no matter what (unless you try to use it on dry pavement, then it'll probably break). A ***viscious coupling*** uses a fluid coupling of some sort to distribute power between the wheels. Usually using a computer. Some viscious couplings are made of stacks of plates attached to the input and output shaft alternately, and by squeezing them closer together, the viscosity of a fluid causes power to be transmitted from the input to the output. Others can work like a torque converter in a transmission, where fluid is splashed by one plate onto another, pushing the second plate. [If you care to learn how torque converters work you can watch this old army video, but it's not really applicable here. Still well worth a watch]( URL_1 ) A ***wet clutch*** works a bit like brakes, but backwards. If you've ever driven a manual, you have an idea of how a clutch works, but a wet clutch is full of oil too, so it doesn't wear out and can handle continuous slipping. This may be used when you want to allow a computer to dole out power to each wheel individually as it chooses. If you watched the video above (you did, right? Right?), you know that the wheels have to turn at different rates on the driven axle, but you might not know they also need to turn at different rates between the front and the rear axle. So if we want to drive the front and rear wheels, we need a differential for the front wheels and a differential for the rear wheels as well as a differential between the front and rear axles. This is where things start to get really complicated and you'll see that 4wd and Awd are just marketing terms developed because it's easier than explaining the myriad of differences to non-enthusiasts. You've made it this far, so keep going. Let's start with 4 wheel drive. 4 wheel drive generally implies that there is a degree of selectability, and something's getting locked to something. Because of the need for each axle to turn independently, most 4 wheel drive systems are 2 wheel drive almost all the time. When you get stuck, you select 4 wheel drive, and you're out. This is done with the transfer case. Usually the transfer case will allow you to select 4 Hi, 4Lo, N, and 2Hi. 4Hi is for driving at speed in 4 wheel drive on a surface that will allow the wheels to slip, such as snow or gravel. 4Lo is for when you're stuck and you want to not be stuck, or you're crawling along in really rough terrain and you need torque, not speed. N is just neutral, and 2Hi is 2 wheel drive, high range, and is just what you'd normally use putting around town. Putting the car into anything but 2Hi on tarmac is a great way to make my day, because I'm a mechanic, and I like nice things. Because the axles need to turn independently and they can't, you go around a corner, get a nice loud crunch, and get to check if your AAA membership is still valid. Now some vehicles don't use a selectable transfer case like that. Instead the front differential is always driven. What you do is you lock the front wheels to the differential at the hubs, and unlock it when you don't want 4 wheel drive. But this generally requires getting out of the truck and that's not nice. Some cars do this on their own using a computer or mechanical system. So now you can send power to the front and rear axles. Most of the time this is great. But what if one wheel on each axle is on snow and the other is wedged up against a rock? You're still not going anywhere. Now you need locking differentials. Note that simply having 4 wheel drive doesn't mean you have locking differentials. See? Marketing mumbo jumbo. So that's 4 wheel drive. What about all wheel drive? Well, the system varies from car to car. Awd is a blanket term that means all of the wheels can be driven at some point or another. Note that in 4 wheel drive, power comes out of the engine, into the transmission, out of a driveshaft, into the transfer case, and then out into a front and rear driveshaft. All wheel drive may do that, or it may send the rear wheels power from the back of the transmission, and the front wheels power from the sides. It's truly a clusterfuck of variability. The most simple type of all wheel drive is an open differential for the front wheels, an open differential for the rear wheels, and an open differential to spilt the power between each axle. This is marginally more useful than 2 wheel drive, but only just. See, if even 1 wheel has no grip, you're not going anywhere. Unless the car has good brake based torque vectoring (that works, which is a crapshoot as well, as some cars have shitty brake based torque vectoring systems), in which case it brakes just the spinning wheel, forcing the power to flow to the other wheels. In any case, this electronical approach tends not to be quite so good as most mechanical ones, but better than some, so we'll keep going. The next most simple uses a locking center differential. This means normally the car has 3 open differentials, but when wheelspin is detected, or you push a button, the center differential locks, and now it works like 4 wheel drive with open differentials. This is actually pretty good. However it only really works if you're stopped. It can't safely engage while you're moving (or stuck, but with the wheels spinning). Part time all wheel drive means normally the rear wheels aren't connected to the engine at all, until they need to be. This is accomplished using a dry clutch (in which case it behaves like a locking center diff), or a wet clutch or viscious coupling. In the latter instances, the computer engages the rear driveshaft through the coupling, causing power to be sent back there. This is how most awd crossovers do it, like the crv. I'll save you some time and tell you it's generally garbage. With a wet clutch/viscous coupling, you've got regular, not brake based torque vectoring. Finally, you can have a limited slip or torsen limited slip center differential. This, I think, is the best bet for most people. Because of its mechanical nature you're not at the mercy of a computer programmed by someone who lives in the city and doesn't understand why people don't just take the train. It actually works. It's smoother, doesn't require any driver interaction or even driver attention, and it just works. Except torsen which might require you to apply a bit of brake. So the center differential is covered. Understand that every principle that can be applied to the center differential can also be applied to the front and rear differentials. In a perfect world, all three differentials would have computer controlled clutch packs capable of precisely sending a carefully selected amount of torque to each wheel. This is a thing in some cars. I believe it's the basis of acura's super handling awd (could be wrong, don't quóte me on that) and the Nissan gtr and a select few other cars. In a next to ideal world all 3 differentials would be torsen or lsd type differentials. This is fairly common. In the worst case you'd have 3 open differentials. In the rear world, all wheel drive systems can be found that are pretty much every variation of this, many with different systems for each axle, but now that you understand what each does and how it works in the real world, you can make pretty informed decisions if you do your research first. Understand that all wheel drive and 4 wheel drive are blanket terms and in order to get anything that's actually useful, you have to understand the actual mechanicals underlying the marketing term. Edit: thanks for the gold. Also, none of you are actually 5 years old. I hope. There are boobs on here, so you shouldn't be. If you want an explanation that doesn't explain the difference between 4wd and Awd, read someone else's concise and misleading explanation. The reason I have to go into so much detail is that the differences between \"4WD\" and \"AWD\" are highly nuanced. Both are made up terms, and originally awd basically meant \"shitty 4wd,\" but thats not the case anymore. If I can type this on a blackberry, you can read it.",
"Prettt simply put, AWD has a center differential which allows front and rear axles to rotate at different speeds. 4WD does not have this center diff so at all times 1 front and 1 rear wheel have to rotate at the same speed. Sometimes its how a manufacturer names it too. I know for a time at least the Jeep Cherokee could run in a full time 4WD mode which had an open center diff, putting it in part time 4WD mode would just lock that center diff.",
"Different manufacturers and people use the terms differently, but in general: 4WD = off-road cars. The 4WD system can be turned on/off by the driver so the car is only driving two wheels normally, but engages the other two for difficult conditions. When engaged, the front and rear axles are connected mechanically - there's no (or little) provision for different wheel speeds as you would experience when taking a turn in the road. AWD = normal/sport cars. All four wheels are driven at all times, with a differential in between to allow \"slippage\" when taking turns. This is better for road use, but not as good for difficult terrain.",
"This question is basically how to start a fight on auto/truck/offroad forums. While there's a consensus on 4WD, what function it provides and how's it's implemented, AWD is still not nearly as defined. Manufacturers will often implement it differently and the function is very different. Even to the point of implementing a Full-Time-4WD and then calling it AWD. You'll get 1 answer on 4WD and a dozen different answers for AWD.",
"These days 4WD means you can switch between 2wd and 4wd. AWD you don't have a choice. As far as what wheels get torque and when - that is more a matter of what differentials you have in the front and rear axles. LSD (limited slip) will allow wheels to slip a bit in tight low speed cornering - this helps with not destroying your tires in parking lots for AWD and 4WD systems Locking differentials are a different beast and will actually force front or real axles to spin the wheels at the same rate and time.",
"All-wheel drive is in some ways similar to the full-time 4WD system in that it also sends torque to all four wheels constantly. However, most modern AWD systems don't offer drivers the option to operate in two-wheel drive and, unlike the 4WD systems, the differential between the front and rear axles cannot be locked. [Source]( URL_0 )",
"Finnaly something I'm an expert at. 4WD 4x4 and All wheel drive, if we're talking about a car, are all the same. This terminology just determines how many wheels can put power from the engine to the ground. AKA \"driving wheel\" Lets run a few examples to make it clear 1: If i have a regular motorcycle, it is 1 wheel drive. But if I get one of those Dakar modified bikes, that have 2 wheel drive, it will be simultaneously 2WD, AWD and 2x2. All possible wheels have \"power\" Now a modern four by four like the jeep renegade, it is on demand 4WD. Power goes to the front wheels all the time, and when needed also goes to the rear wheels. The vehicle has 2WD and 4WD modes. When in 4WD it is also in 4x4 and AWD. See where I'm going with this? It's just a matter of semantics. If you get what the words really mean in practice, that's it. All those terms tell you is how many wheels in the particular vehicle are capable of driving. Now, for the nitty gritty: Every manufacturer likes to call their traction systems a fancy name, like Subaru with their symetrical all wheel drive, or Land Rover with therir Terrain Response, or Jeep with Terrain Select. There are also many types of all wheel drive, or four wheel drive, or four by four... you get the point. I'll just call it AWD from now on. Older vehicles will be rear wheel drive, with the option to turn AWD on. Most modern \"common\" awd vehicles will be normally FWD and switch to AWD on the fly when needed. Some vehicles you need to switch by hand, at the wheel, others have electronic engagement, while others there's just a clutch that couples the secondary axle. The famous Land Rover Defender is what is called Full Time AWD, where the vehicle always sends power to all four wheels, you don't have the option of turning AWD off. For those cases, there's a third differential between the front and rear axles to compensate for the wheel speed difference between axles. Anybody that tells you AWD must do this, 4WD must do that, 4x4 must do that other thing, is just wrong and has no idea what they are talking about. Source: Am fourth generation mechanic. Also Mechatronic Engineer, and worked for one of the 5 biggest car manufactures in the world, in the AWD deppartament. TLDR: AWD 4WD are the same, if you are referring to a car. It just serves the purpose of conveying the information of how many wheels are capable of powering that particular vehicle. edit: Even people that work in this field are confused by the terminology. That's why the real question should be: What Kind of AWD or 4WD or 4x4 do you have/want/need. Not the difference between these terms. Even manufacturers use different terms to describe the same thing.",
"4WD is typically selective (can be driven in 2WD or RWD) where AWD is always on. Typically 4WD uses a mechanical center differential with no slip (chain or gear drive) where AWD uses a viscous coupler (kind of like a wet clutch) where it can have some “slip” and direct power to front or rear as needed. Obviously very basic description but hope you get the idea.",
"The difference is in the relationship between the front differential and the back differential. All-wheel drives usually have a horizontal differential that transfers torque to the axle with most resistance, making it better for driving on roads. In a 4Wd both axles are supplied with the same torque at all times, making it better for off-road.",
"A truck that is capable of 4WD is usually a rear wheel drive vehicle for road driving until you lock the front diff. The front and rear diffs are usually locked harder than an AWD and will suffer on sealed surfaces for it. A Subarus diff (for instance) will have a baseline front and rear balance for power delivery. I.e. at 5% throttle it acts like a FWD, 20% throttle you'll get 10% of power to the rear wheels. When you floor it the distribution looks something like 60/40. The front and rear diffs are designed to be engaged at all times so can move to allow differential rotation. An AWD is supposed to be AWD at all times and is designed as such. A 4wd lets you choose how the powertrain operates based on your situation, and is not designed to be perpetually engaged. Hope that makes sense.",
"If you have more than 4 wheels, then AWD > 4WD! :-) It's about traction distribution, AWD is a type of 4WD that is on all the time, so usually changes traction distribution according to what use you are giving it.",
"While users like /u/krovek42 gave you a good technical description, understand that for some manufacturers, 4WD vs AWD is a marketing distinction, not a technical distinction. Ford uses 4WD when they market for off-road use and AWD when they market for all-weathr highway use. Let's look at the Escape and Edge: both use a front transaxle (FWD) equipped with a power take-off unit that connects to the rear driveshaft- > rear differential - > rear wheels. However, the Escape is marketed as 4WD since it still is marketed as a \"sport\" utility vehicle while the Edge is a crossover and gets an AWD designation.",
"4WD= All the wheels get turn at same speed AWD=power can be split/directed between front and back.",
"Generally speaking 4 Wheel drive sends equal amount of power at all times. All wheel drive is usually sending 80:20/70:30/60/40 to the front or back wheels. When the wheel recieving the most power starts to slip, the opposite end kicks in and the wheels are then divided at 50:50 until traction is regained, at which point it goes back to its original ratio.",
"I'm starting to hate r/EIL5. AWD means the tires can move at different speeds based on road conditions. 4WD means all tires are spinning, but at the same speed. This is good off road but bad on road. That's how I'd explain it to a 5 year old.",
"imagine if you had a car on a lift and tried to stop each wheel from moving: AWD: only one tire out of 4 moves 4WD: only one of the front and one of the rear moves There are different devices to change this, such as limited slip differentials, locking differentials, smart stuff like brakes helping.",
"There's no official difference, but 4WD generally refers to a system designed to work best off of paved roads and AWD generally refers to a system designed to work on paved roads. AWD, like an Audi, puts the power to the wheels with the most grip, and 4WD, like a Jeep, locks the wheels so they always spin at the same speed.",
"AWD is a marketing term originating with Subaru to differentiate its passenger car market from the larger 4WD market even though it’s the same thing. Since then AWD has been appropriated by other manufacturers in their non-off-road offerings. From a technical perspective, there are, at its core, very few differences, however AWD systems used in passenger cars often include torque splitting technology to provide more or less power to front or rear wheels (and side to side). Ultimately AWD is used to market on road use passenger vehicles while 4WD is used to market vehicles with off road purposes.",
"Edit: The top voted answer is now a better one. The top voted answer is incorrect, there is no difference. Just like there is no difference between a station wagon and an estate car. It's just two different names for the same thing. There are however many different versions of systems that drive on all four wheels and some are better than others for certain tasks. It's all a trade off between different use cases, price, weight, fuel economy etc. Nearly every car manufacturer puts a slight twist on their system and if you want to find what's best for you have to start learning about different types of all wheels drive systems and diffs etc.",
"If the car has 4 wheels, and they all drive, we have both 4 wheel drive and all wheel drive. A few decades ago, most 4 wheel drive vehicles were offroad or utility vehicles, so the term \"4WD\" came to be associated with such vehicles. When 4WD on passenger cars was getting more popular, the marketing department had to invent a new term to dissociate themself from the image of the offroad trucks; and so \"AWD\" was born. So, the only \"difference\" is one of marketing, not of engineering or technical detail. Other answers mention different types of differential but that is a different topic really. You can have various types of differential in cars marketed as \"AWD\" and in vehicles marketed as \"4WD\"."
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7ivpiw | If we can see through water how come when snow is frozen its pure white? | Repost | explainlikeimfive | {
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7iwaxj | Why are there so many types of screws? (Phillips, flathead, Allen, etc.) Why isn’t there a single, standardized type of fastener? | Repost | explainlikeimfive | {
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"As usual, there is a relevant XKCD... URL_0 Automod appeasement edit: At one point, there was only one type of screw. I'm no screwolologist, but it seems fair that the straight slot would've been that one type. Its ups were that it was easy to manufacture and it was easy to make a tool for it, but anybody who's used a straight-head knows it's a terrible, terrible screw head. So somebody set out to make a better one. I've no idea if I'm right, but I'm gonna guess it was a guy named Phillips. So he said, if one slot was ok, then two slots should be better! But anybody who's used a Phillips screw knows that they come with an appallingly low torque limit before you now have a conical-head screw that's impossible to do anything with. So somebody said straight heads suck, and phillips heads aren't much better, so I'll make one with some more meat in the tool and straight sides so rounding off and breaking tips wasn't such a concern. Thus, the Allen head was born. Except that allen/hex heads, below a certain size, are even easier to round out than Phillips heads were, and it's fucking impossible to get the hex key in there straight/to full depth in the fastener. So somebody said, that Allen guy was on the right track, but he didn't go far enough. So the Torx bit got invented. But then, people said that Torx was too complicated and it's impossible to tell the difference between a T25 and a T27 and oh my god why are there so many choices? So we went back to basics and saw if we couldn't improve on the Phillips design, which beyond its propensity to snap tips and round off fastener heads wasn't a *bad* design. So we got stuff like JIS, which is virtually identical to Phillips but designed to destroy your phillips bits, and Posidriv, which is the bane of my personal existence because they're designed to never, never strip while tightening (which they don't), but to always always strip immediately when removing (which they do). So that shit got real complicated and somebody said, guys, guys, you're making this too complicated, eh? What if we took an Allen, which is ok but has too small a load-bearing shoulder and too-great leverage angles, and simplified it, eh? And the Robertson (us Yanks call it a square bit) drive was born. And it was good. But somebody saw that the construction industry was using a messy hodgepodge of phillips and robertson screws and said, what if we combine them so construction people don't have to buy so many different bits? So now there's a combined R1/#2 phillips bit and screw. I guess that guy never got told about Torx bits, but hey, whatever. So now the construction industry is using an even messier hodgepodge of phillips, robertson, torx, and combi-drive bits. And then, electronics came along, and at some point electronics manufacturers decided that we lowly consumers couldn't be trusted/were too dumb to open their electronics, so anti-tamper bits had to be made, because everybody had tools to open the bits that were already around, for the most part. So they made those, starting with the Torx bits with the little posts in the middle, but it turns out those are pretty expensive to manufacture so they started making tri-wing screws, and those dove-tail head screws and the two-post screws and etc. etc. etc. because all the same shit that happened in the 10 paragraphs above happened in the anti-tamper-bit world all over again. Over time each industry sort of settled on certain screw type heads for certain applications, because as there was no \"perfect\" screw head each type had its strengths and weaknesses, and everybody is firmly entrenched in their own screw head system, and there is *very* little hope of ever unifying everybody, because there's a lot of money in it now. That doesn't stop people from trying, though - but since they don't understand the market dynamics and why there will never be such a thing as the one true screw head, all they do is just add yet another type to the mix, confusing everybody just that much more. Edit 2: well now my inbox is screwed, and it seems somebody has put an idea for a new screw head next to my name.",
"In addition to Skatingraccoon's answer, many companies develop their own screws or other methods of attachment for their products to make it harder for the consumer to repair the item on their own. A proprietary screw needs a proprietary screwdriver, and if the company that makes the screw doesn't sell the driver, then it means people have to go to the company for repairs, which allows the company to charge them more than it actually costs to fix the product. Nowadays, smartphones are growing more and more proprietary, and the reason is so that it is more difficult to fix a damaged phone. With some of Apple's earlier iPhones you can see the unique shape of the screw: ( URL_0 ) Although apple did not create the 5-point screw, when they made the iPhone 4s they recognized that it was a very uncommon fastener, so they have used it to make their iPhones ever since. As the industry is racing towards thinner phones with larger screens and smaller bezels, some manufacturers have removed external screws altogether. The Google Pixel for example, has no screws on the outside. The Samsung Galaxy S7 Edge is another phone without visible screws. This is achieved by using an adhesive to fasten the screen to the frame, which saves space, and makes self-repairs much harder than before. That's just the relation to smartphones though, in construction and industry there are many other applications for unique screws. A little-known fact about screws is that screws with more vertices and angles in the bit design grip the driver better. For example, if you had a screw that had a bit shaped like an octopus, that would give the drill bit 9 points to transfer energy into the screw (8 legs and the head). If you had a screw with a bit shaped like a snowflake, it would be even better. The problem with forcing a lot of vertices into the design of the screw/bit is that it becomes easier to break the screw/bit, and the time/cost of production increases. That's why there are so many kinds of screws, so that consumers can choose the right one based on what they're doing and what their budget is. Hope this helped!",
"Far more than you ever wanted to know: URL_0 Flathead screwdrivers suck, but they were something you could make with a hammer and anvil and forge. Philips (the real ones) were designed before power drivers with torque control were invented. There are a zillion modern designs to provide greater torque limits with reduced material (weight/space/size) that view standardization as an accomplice to theft. They are designed to be difficult to unscrew without the exactly correct driver, to deter theft.",
"Some things that determine the type of a screw head: * How hard it is (or was) to manufacture * Patents and copyrights * industry inertia * what tools the installer or maintainer will have * Whether the screw will be installed by a robot * How much force does the screw have to withstand * How much of the screw head can stick out of the surface * The size of the screw * other environmental factors (expected corrosion, paint, hard to reach etc)",
"Another angle people are not really covering. The world wasn’t always as it is today. Transportation of products was far more difficult and expensive. Things like screws, bolts, and fasteners are fairly cheap to make. People making more complex items would either make these fasteners themselves, or get them from someone local. Now expand that idea across the entire world. With information and products being shared more everyday, there is less variation. However habit is a strong motivator. If my manufacturing process is working smoothly, why change? In all honestly is surprising there are not more variations. On a side note, this expands to many things. Recently I took a truck driving job. I found it really odd how many different warehouses, even by the same company, have totally different procedures in the way they do logistics. Unless I’ve been to that exact warehouse before, I have no idea what policy’s and procedures they will have. What makes things even more complicated is that everyone assumes that things are done the same everywhere, so there’s an assumption I should know what to do. You’d think there’s one best way to do things, right?",
"The first screws had a simple slit. When automation began, the Phillips screw was invented because it is self centering. The sides are angled, so if the first machines applied to much torque, they would slip rather than break. When machines got torque limiters, there was no need for angled sides. Pozidrive (pz) screws were developed. They only have small angled slits to make them slip should too much torque get applied. Later came hex and torx screws. They do not slip anymore, so the torque gets transferred completely and they break without efficient torque limiting.",
"I know that each have their advantages and disadvantages in machining and construction, but specifically the \"Phillips\" head (AKA Cross-head) screw which is most common is often misused. 1. It has a notoriously low torque point, so it strips fairly easily. However, this is specifically needed with some industrial and automated applications, where engineers would rather have the screw strip at a certain torque applied by error rather than apply more torque and damage the item in question. 2. The Phillips is self-centering, so when an automated drill drive a screw in, all of the torque is evenly centered and distributed. Again, essential for some automated applications. So often the Phillips screw is used where higher torque would be helpful, but because of its availability and popularity it's often encountered in places where it's low torque become an unwelcome hassle. Not an engineer but that's the general point.",
"It has to do with application. A simple flat head or Phillips is mostly used to just do a simple fastening. Allen is more for fastening with more torque, let's say you're going to machine a part and are fastening to a fixture, you would feel more comfortable using Allen set screws so your part doesn't bounce around. Some of the other screws are more rare so someone doesn't come along and unscrew anything.",
"In short, because manufacturers and engineers are constantly improving and customizing products for their specific applications. Fasteners are the easiest thing to change when engineering a new product. It is easier to design a new fastener then scrap a good design because stock fasteners won't work. Thus, you have tons of different types of screws on the market. For a specific example, look at just machine screws. Originally, there were basically just slotted drive screws that you would drive with a Slotted or \"flat head\" screw drivers. The slotted driver would tend to slip out of the head so in the 1930's the Phillips screw and screw driver was invented. In both cases, they made a flat head for countersinking into the surface of a material, and a round head that stood proud of the material for use in hard materials that didn't easily countersink. Unfortunately, the Phillips drive can still slip and will tend to strip easily so at some point the Allen drive or internal hex drive was invented. That fastener was made with several head styles as well and was also made with a very strong alloy for high strength industrial applications. However, the internal hex drive can still strip in high torque applications so engineers improved on it with the development of the Torx drive (also called star drive, or six-lobe). As you can see, just the narrow application of machine threaded screws, we are already at dozens of combinations of heads and drives. Multiply that by several different materials that they can be made of (soft steel, alloy, stainless, brass), dozens platings and coatings, and dozens of different lengths for each combination and we have options in the thousands. Now there is a more recent issue of products being made with custom fasteners with obscure drives in order to make it harder for the consumer to service the items themselves. This is common in electronics and automotive applications. This has increased the number of different types of fasteners exponentially as well. Every type of bolt, wood screw, pin, and clip has gone through a similar progression and evolution.",
"Tech companies (for example) want their products to be really difficult to disassemble so you have to pay them to get a repair if it breaks.",
"When you're a robot or a human laying on your back with an automated driver and a fastener balanced on top of your bit, few things fit better than a 6-sized torx or perhaps a Robertson with shank. When you're a machinist and you have to countersink the bolt head in a smallish circular hole, Allens work best. This sometimes happens with complex whatsamajiggers that add another layer on top of the preexisting countersunk fastener. Phillips and slotted are legacy products.",
"Essentially for all the screw head types, you can make a statement like \"straight screw heads are easy to manufacture, but with power tools there is a strong tendency for the bit to slip out of the slot and mar the work surface.\" or \"Philips heads won't slip out under power and will cam out rather than over tighten, but they will strip easily making it difficult to remove. You have to push in while screwing out.\" or \"Robinson heads won't slip out, won't strip, and work well with a tortion clutch to prevent ovdrtightening. Too bad Robinson was stingy with his patents so no one supports his screw heads outside of Canada\", or similar \"this screw head is good for these reasons, but is bad for these other reasons.\" Picking one standard would work well for some things, but not others."
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7j0m1h | How do antidepressants work in the human brain? | Repost | explainlikeimfive | {
"a_id": [
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"text": [
"I'll just touch on the most common type of antidepressant, which are SSRIs, or \"selective serotonin reuptake inhibitors.\" Serotonin is a chemical transmitter that we understand to be important for regulating mood and other \"higher\" functions. It's released from neurons in certain parts of the brain, where it binds to neurons elsewhere and tells them to do things. Without getting too complicated, this brain activity helps make us feel \"normal,\" or not depressed. People with depression tend to have low stores of serotonin to release, or don't release as much as they should. The purpose of an SSRI is to make that available serotonin last longer. Naturally, the brain recovers serotonin that's been released, and recycles it for later. As the name implies, a \"reuptake inhibitor\" will stop the brain from recovering that serotonin, so it has more time to float around and do its job. **True ELI5 Answer:** If you imagine serotonin as kids running around being happy in a playground, SSRIs are equivalent to giving them snacks and water so they can play all day. That, or like slashing their parent's tires so they literally can't leave."
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7j6mry | Why are female breasts and boobs seen as so 'inappropriate' even if the woman if breastfeeding, but things much more out of the ordinary such as dismembered limbs and torture are PG13? | Repost | explainlikeimfive | {
"a_id": [
"dr40knk"
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"text": [
"Ahoy, matey! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: Why is porn more censored than violence ? ]( URL_5 ) ^(_9 comments_) 1. [ELI5: Why is Violence more tolerable than Sex in America? ]( URL_6 ) ^(_ > 100 comments_) 1. [ELI5: In movies, why is excessive violence/blood OK, but sexuality off-limits? ]( URL_3 ) ^(_19 comments_) 1. [Why is violence considered acceptable to show on american television but anything sexual isn't? ]( URL_7 ) ^(_5 comments_) 1. [ELI5: Why is violence more acceptable than nudity or sexual content in media? ]( URL_2 ) ^(_60 comments_) 1. [ELI5: Why is it appropriate for PG13 movies/shows to display extreme violence (such as mass murder, shootouts), but not appropriate to display any form of sexual affection (nudity, sex etc.)? ]( URL_1 ) ^(_ > 100 comments_) 1. [ELI5: Why do we shield children from sexual content, but not violent content? ]( URL_0 ) ^(_74 comments_) 1. [ELI5:Why are parents so afraid of nudity or sexual content? ]( URL_4 ) ^(_7 comments_)"
],
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"https://www.reddit.com/r/explainlikeimfive/comments/1yahp4/eli5_why_do_we_shield_children_from_sexual/",
"https://www.reddit.com/r/explainlikeimfive/comments/5uhr0x/eli5_why_is_it_appropriate_for_pg13_moviesshows/",
"https://www.reddit.com/r/explainlikeimfive/comments/34pg6o/eli5_why_is_violence_more_acceptable_than_nudity/",
"https://www.reddit.com/r/explainlikeimfive/comments/30arpa/eli5_in_movies_why_is_excessive_violenceblood_ok/",
"https://www.reddit.com/r/explainlikeimfive/comments/3zz2a4/eli5why_are_parents_so_afraid_of_nudity_or_sexual/",
"https://www.reddit.com/r/explainlikeimfive/comments/zk37g/eli5_why_is_porn_more_censored_than_violence/",
"https://www.reddit.com/r/explainlikeimfive/comments/3q25bp/eli5_why_is_violence_more_tolerable_than_sex_in/",
"https://www.reddit.com/r/NoStupidQuestions/comments/7e40cy/why_is_violence_considered_acceptable_to_show_on/"
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7j9st6 | How and why exactly does anxiety affect your whole body? (eg. digestive system, feeling cold, etc) | Repost | explainlikeimfive | {
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"dr4otxx",
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"Stress causes your adrenal glands to release adrenaline which causes a wide range of physical symptoms.",
"Anxiety evolved to deal with threats, so the body can respond accordingly. A lot of the physical symptoms are related to the hormones released to prepare your body to fight or flee. The reason you get digestive symptoms is because the hormones restrict blood flow to your digestive system, so there is more blood available for your muscles and other organs to use. Feeling cold is explained by blood vessels near your skin constricting to divert more blood to muscles and other important organs."
],
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