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n38tf9 | Why does a negative multiplied by a negative become a positive? | Mathematics | explainlikeimfive | {
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"For positive a and positive b a + (-a) = 0 (I think you don’t need an explanation why this is true) a(-b) + (-a)(-b) = 0 (-b) (multiply both sides by a negative number -b) -ab + (-a)(-b) = 0 (assume that positive times negative is negative) For this to be true (-a)(-b) must equal ab so if a negative times a positive is negative then a negative times a negative is positive You can multiply everything by b instead of -b to show that if a positive times a positive is positive then a negative times a positive is negative"
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n395w6 | Why do people and some animals involuntarily stretch when we’re tired or waking up? Is it the same reason as to why we yawn? | Biology | explainlikeimfive | {
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"It’s natural almost to the point of being impulse. It’s your bodies way of preparing for movement. If you’re waking up, it helps push blood flow to limbs in case you need to go chase gazelle. When you’re wanting to sleep, this is your bodies way of trying to keep you alert and ready for movement, like if an animal is about to hunt you in the dark."
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n3987p | so if we get sick & our immune system remembers what got us sick so we don’t get sick again, how come people with allergies still get allergies, how come people with allergies to peanuts just straight up perish | Biology | explainlikeimfive | {
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"Someone will probably do a better job than me, but an allergy is when that immune system goes haywire when it detects what is normally a benign thing. Your body thinks pollen, for example, is a threat like a virus or bacteria and goes overboard trying to kill it. It's a case of mistaken identity. I've never understood, though, why it seems there is no such thing as a mild peanut allergy. Seems like you're either fine with them or they kill you on contact.",
"An allergy is similar, but the immune system response gets out of hands or the immune system is oversensitive. For example pollen or food allergy. Like if you would use a sidewinder rocket against a crow or something. Also, the immune system detects a otherwise harmless substance such as pollen or contents of a peanut, and fights this foreign and potential harmful substance no matter what even if it would pose no threat",
"So sickness is illness invading the body from without, allergies are your body attacking itself from within. Histamines are to blame. Your body is literally damaging itself because it thinks the triggering allergant is much more harmful than it is. So long answer short, it's two different systems at work fighting germs and controlling histamine response."
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n39vy1 | Why does skin heal more slowly the older you get? | I'm turning 40 this year, and I'm noticing that the nicks and cuts I'm used to getting which have always healed really quickly are leaving more scars and lasting longer than they have in the past. Im outdoors active, and accrue more than a few cuts often on my lower legs. Is this a natural part of growing old, which is in line with my observations of my parents' skin as well, or am I not caring for my skin well? | Biology | explainlikeimfive | {
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"Think of your cells dividing as a printer making paper copies. A copy can only be as good as the original but usually you lose a bit of quality. Over time, the original document wears out and you're making copies of copies. Each copies need to be a certain quality level or else they're rejected. As you make more and more copies, the reject rate increases over time. Your dividing cells undergo a check to make sure they're copied properly. If they fail, they undergo planned cell suicide (apoptosis) and are recycled. As you age, a larger percentage of dividing cells fail the check because of DNA wearing out from copying, making it harder to increase the number of good cells to heal a wound.",
"As you've said, you are active outdoors. Meaning you probably get a bit of sun and sun is tough on our skin. This could have something to do with it. Also age has a lot to do with it, you're not old but your skin isn't 20 anymore and add sun exposure the health of your akin could be 5 to 10 years ahead of your actual age. Keep your skin moisturized and wear sun screen this will help preserve your skin health in the long run.",
"This may not be a factor but not knowing your health, diabetes can cause major slowing of healing, too, so I wanted to bring it up since it doesn’t seem to have been mentioned. If you know your blood sugar is good, then nevermind.",
"Your skin doesn't heal. It is connective tissue that stitch together places that have been damaged. The skin slowly grows back over the connective tissue in a process called remodeling. This is why you have scars and they slowly seem to go away. Lower legs often have poor blood flow. They are the furthest place away from your heart and require a lot of work to return the blood from against gravity. Think of your veins and arteries as highways. If they aren't well kept the traffic bringing healing supplies and removing damaged materials takes longer. I would see a doctor if the healing time is really noticably longer than it was in the past. There could be underlying events that could be caught and fixed before they become more severe.",
"Older than you, not in great shape but cuts still heal as fast as when I was 20. I cook a lot so every couple of months I get a fresh knife cut. Takes just a week to get past the bandage stage and another couple to finish healing. Could very well be diet, especially vitamin C and A. We eat a lot of foods rich in A, use citrus juice in meals and take multivitamins. Our diet is also rich in foods that provide iron, zinc and copper. Plus the RDA of proteins from mostly healthy sources (red meat is a once a week item if that. Chicken & fish are most common).",
"Think of our skin like a rubber band and just like a rubber band that’s 10 years old, it starts becoming brittle, stale, stiff, and difficult to return to its original state.",
"The turn over rate of cells is slower, there is less collagen and fat also. The older you get the more fragile the skin becomes especially if you are a smoker, have alot if sun exposure and genetics. When I worked in nursing homes and did home health care ; some very elderly residents/clients had skin so thin it would rip just by \"sticking\" to a surface since their sweat glands dont function normally. There are many factors as to why our skin changes as we age.",
"Completely anecdotal, but last year I noticed I was accumulating injuries faster than they were healing(moving is a bitch) and that improved when I started eating more gelatin (real jello) and taking a biotin supplement. This spring I started taking them again when I noticed the same thing happening and it seems to be working. You can get biotin gummies labeled as hair, skin & nails or sometimes just a \"beauty\"",
"One word Elasticity! For example Stem cells, for instance, are known to decrease substantially over time, with only a fraction as many present in the body in adulthood as during childhood. These play important roles in regenerating the cells and tissues that may be lost or damaged with a wound or injury. Of course this is not the only culprit, decreased decreased collagen in the skin means it loses some of its flexibility, and can more easily tear or break. Skin also tends to thin with age, along with a redistribution or change in subcutaneous fat layers. Circulation problems, caused by high blood pressure, diabetes, heart problems, vein disease, and related pathologies. In most cases, these conditions result in less complete circulation in the body, meaning nutrients and other vital substances are less effectively circulated and therefore less effectively available where they are needed for wound healing, skin and tissue health, and related purposes. These are just some examples of why our skin heals slower overtime. Also think about Diabetes, Clotting Disorders and also consider immunosuppressant drugs! These and other lifestyle factors all play a role as we age.😉",
"I always find that taking a vitamin E pill helps skin heal faster and helps nails and hair grow faster too."
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n3ah16 | What is mansplaining and is womansplaining a thing? | Also, are there other forms of "splaining", such as cultursplaining? | Other | explainlikeimfive | {
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"“Mansplaining” is the act of a male explaining a topic to a female on the assumption she wouldn’t already understand it simply because she’s a female - even if her position or role required her to. Women can “womansplain” as well in the other direction. In fact, most groups can “‘splain” really. The key ingredient to ‘splaining is condescension, and it seems males do it more than females - particularly higher up the social ladder. Hence “womansplaining” (while existing) is not much of a thing in practice."
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n3atew | Why does skin regrow on places it would never grow, for example an arm after a person has had an amputation? | Biology | explainlikeimfive | {
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"Assuming I understand your question correctly. It doesn't. They leave enough excess skin to cover the end of the amputation. Then as it heals, scar tissue forms where the stitches were."
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n3az6b | Why does a rechargable battery has a limited cycle/lifetime. | Technology | explainlikeimfive | {
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"It depends on what type it is. In some you accumulate crystal errors (lithium), others corrode (lead-acid) and so on"
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n3bj1a | Why are most cheap PCB’s and circuitry green colored | Technology | explainlikeimfive | {
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"Green was the coloration given to the conformal coating that covered the first fiberglass boards. There were also some other colors such as brown or orange, but green won out as the most recognizable and aesthetically pleasing default. But, it doesn’t really matter. It is just a dyed coating, it could be any color. These days they are green because people expect them to be green, no other reason.",
"Fab houses don't charge extra for green, and there is no extra wait time. So, the cheapest & fastest way of getting a PCB is to go with whatever they are tooled up for, which is green. Other colors, they might only produce once a week, depending on demand, so they charge a premium for the tooling change, and you may have to wait. Marketing folk on high end gear think it's worth the extra wait & cost to stand out from the crowd, but color has no impact on performance.",
"The green is from solder mask, it just gives it some aesthetic over boring beige. Solder mask is required to keep the solder from spreading for surface mount components, and they tossed in some dye. It became just kinda tradition from there. Of course like you said you can get other colors, and if you send in your own circuit design to a fab shop to make the boards for you they usually have a few colors to choose from. Internally at big circuit manufacturers they would sometimes use different colors for coding -- green is just a regular old board ready for sale while red was used for prototype boards that shouldn't be sold etc."
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n3c0ue | – if the idea of “complimentary colors” is that they cancel each other out and produce a grayscale color, how can there be different models (RGB, RYB, opponent process)? Wouldn’t there only be ONE correct model that would cancel the right two colors out? | Other | explainlikeimfive | {
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"The primary colors of light and the primary colors of pigment are different. The primary colors of light mixed together make white light. The primary colors of pigment mixed together make black pigment. They're different models because they're modeling different things.",
"Color theory is wildly complex the more you look into it. The short answer is that is that \"colors\" are human perceptions, and what we perceive is limited by the makeup of our eyes. Light comes in different wavelengths. X-rays, visible light, ultraviolet, etc, are all different wavelengths of light. The visible light spectrum can be broken down further into what we call colors, and is composed of the classic \"red orange yellow green blue indigo violet\" rainbow. To \"see\" light, you need a receptor that can respond to a specific wavelength. The key point here is that each receptor can only target *one* wavelength; you can have receptors that only pick up green light, receptors that only pick up red light, receptors that can only pick up certain wavelengths of x-rays, and so on. Human eyes contain three different types of cones, that can pick up blue, green, and red light respectively. So, we can only really \"see\" those three colors. All other colors we need to \"interpret\", by seeing a *mix* of blue, green, and red. For example, if you look at a sun-flower, it'll trigger the green cones and red cones in your eyes. When both the green cones and red cones are triggered in a specific ratio, we call the result \"yellow\", even though we don't actually have the ability to perceive \"real\" yellow wavelengths. In color theory, this means that we can mix green and red light to generate something that we perceive as yellow, even if, in reality, it's still just generating both green and red light at the same time. That's why pixels on your TV have only red, green, and blue lights; by mixing just those three, they can generate the vast majority of colors that humans are capable of perceiving. Things get even more complicated when we talk about mixing paints, because paints are somewhat the opposite of how pixels work. Pixels *emit* certain wavelengths of light, whereas paints work by *absorbing* every wavelength except the color you want. If you want a paint to look green, you need a material that'll absorb everything *except* green. That way, when you shine a light at it, all the other visible wavelengths will be absorbed, and only the green wavelengths will get bounced back, so that someone looking at it will \"see\" green. So, to summarize; color theory is wildly complex because the human eye is wildly complex. Complimentary colors are more of a graphic design tool rather than an underlying physical truth. Different models are used because things that emit light (like a pixel on a TV) and things that absorb light (like paint) behave very differently when mixed."
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n3d0m3 | How can a wart that i've had my whole life just dissapear. | So i've had this little guy since i was 5(20 now).He was quite big and ugly on my left hand and we've tried a lot of things to get rid of it,but nothing worked,it just stayed there. A few weeks ago,i've realized it's no longer on my hand,gone,without a trace so how does something i've had for 15 years just dissapear like that without me even noticing. | Biology | explainlikeimfive | {
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"Warts are caused by an infection with the human papilloma virus (HPV). The virus causes an excess amount of keratin, a hard protein, to develop in the top skin layer (epidermis). The extra keratin produces the rough, hard texture of a wart. Eventually, your immune system is able to defeat the virus and kill it off, meaning the wart will shrink and die. I had a wart that was the size of a large pea on my index finger for most of my teenage years, one day I noticed the wart shrivelling up, and it fell off permanently a few days later never to return."
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n3dt21 | How does the undo feature work in collaborative applications such as Google Docs? | Technology | explainlikeimfive | {
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"[Chuktropolis Welling Moran of UC San Diego]( URL_3 ) explains that different programs implement an undo feature in different ways. Recently, the undo button has evolved to accommodate collaborative text-editing systems, such as Google Docs. So what goes on under the hood? Before we learn about how a computer keeps track of undo, we must understand what a stack is. A stack is a way of storing data, where new data is added on top of old data, and the most recently added data will be removed first. This is analogous to a pile of books: the most recently added book will be on top, and it will be the first to be removed. Many implementations of undo use stacks. [Max Lynch,]( URL_0 ) the CEO of Ionic Foundation, describes the undo function as a stack of operations that the user has performed. In other words, it is the \"history\" of the actions the user has taken. Whenever the user does an action, we add the action to the undo stack. When the user wishes to undo something, each action is taken out of the undo stack. Think back to the pile of books but now imagine someone wants a book in the middle. They wouldn't want to topple the pile to get the book from the middle. Instead, they would remove each book off the top of the stack, undoing what they did, until they reach the book they need. Collaborative applications implement the undo feature in a more dynamic way using stacks. In the case of [Google Docs]( URL_2 ), the program keeps a copy of the document on each user’s computer, and sends each change a user makes to a central server. The central server then sends a signal to all of the other users to implement the change on their copy of the document. When someone undoes an action in Google Docs, the local stack of actions on that user’s computer removes the last action. Then, that change is sent to the central server, and the data on all copies of the document are updated to reflect the undo action. The main challenge that arises when implementing this is users making changes at the same time. This could cause a number of problems, including changes being applied to the document in the wrong order. To mitigate this, [Google Drive Blog]( URL_1 ) states that Google Docs implements a technique called operational transformation. In his academic [paper]( URL_4 ), Mandeep Kaur describes operational transformation as an algorithm that “transforms” the changes being received from others relative to each user’s document. This transformation is done so that the change can be completed without editing the rest of the document. The inner workings of this algorithm are very complex, but it essentially ensures that when users make simultaneous changes, these changes (including undo) happen in the correct order. TLDR: the undo function is a list of actions that is stored on the computer. When the user either clicks on the undo button or does “Ctrl + Z/Cmd + Z” on their keyboard, it removes the most recent action in the list. In collaborative applications, there is a local list of actions on each user’s computer which can be used to undo the latest action of the user. Processes such as Operational Transform apply these changes in a central server and merge actions to create simultaneous undo actions."
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n3e71i | Why does scar tissue sunburn more easily than normal skin? | I've noticed when I'm in the sun even with appropriate sunscreen areas that I've suffered injuries to in the past almost immediately become red, even though they do not have visible scars. | Biology | explainlikeimfive | {
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"Scar tissue differs from regular skim in a few ways, it's the same ingredients but it's built and layered differently because one is grown at a steady rate and scar tissue is an emergency response so develops differently. If the scars are lighter in color to your normal skin tone then we can see that this tissue has less melanin so will react differently to the sun. If the scars don't have hairs then you can tell how deep the wound was. (Deep enough to damage/remove the hair follicles) which might also mean the sweat glands are damaged meaning the skin is drier and less supple and more prone to burning. I'm sorry how I wrote this, I'm having brain fog lol I swear English is my first language but uhm I'm struggling to sentence rn lol Fun fact; severe scurvy (vit c defieciency) can cause old scars to reopen. Because scar tissue isn't ever done healing, skin is always replenishing itself and scurvy interrupts that process."
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n3eyhq | Why doctors can't just remove the pain nerves in an area with chronic pain? | So, there are pain nerves, right? Different from the movement nerves. Normally you want to have functional pain nerves so they can alert your brain to an injury. If someone has, say, arthritis, or a bad joint or bone injury 30 years ago that has long since healed, those nerves are just sounding the alarm 24/7 even though there's nothing to be done about it. So, since that pain isn't giving you any new information you can use to help take care of your body, and is actively impeding your life, why not just remove the pain nerves, or cut them off from the nervous system? They are useless at that point for actually reporting things that would impede the mechanical function of that area, so getting rid of them would be a net benefit. | Biology | explainlikeimfive | {
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"This is a thing, its called nerve ablation. Its just not a common treatment. The preferred treatment is called a nerve block and involves injecting a long lasting anesthetic into the nerve. Nerve block injections are cheap and can be done in an outpatient setting, regardless of what nerve is being targeted. On the other hand, nerve ablation is a reasonably complicated surgical procedure if its targeting a nerve in the peripheral nervous system and a very complicated, high risk procedure if its targeting a nerve in the central nervous system. Ablating a nerve in the peripheral nervous system isn't a permanent solution because the nerve will grow back after about a year. Nerve blocks don't last that long, but again they're much easier to do. Because of the high cost/complexity/risk of nerve ablation, its very rarely done and only then in very severe cases where nerve blocks haven't been effective.",
"Other users have given great answers but they've all missed something significant: Substantial pain processing happens in the central nervous system as well (and we can't remove that) AND that part of the nervous system becomes hyperactive, basically telling you that you're in pain (often severe pain) even with little or even zero painful input. An analogy might be stubbing your toe once; it probably hurts but it will go away. If you instead hit it with a hammer really hard 10 times over 10 days, you'll probably really change your behavior to deal with that toe. On the 11th day, you'll still be keenly aware of the damage done to your toe and it will still be extra sensitive, even if nothing happened to it that day. During long term chronic pain, your nervous system is constantly in that \"11th day\" pain state, where it's super sensitive to any type of stimulation. Source: I'm a chronic pain treatment researcher",
"Had ablation on the nerves in my lower lumbar after a bad car wreck. Literally a miracle cure for the pain!",
"Because removing the pain doesn't solve the problem. Take your arthritis example. Arthritis is literally deteriorating the joints. Taking the pain away doesn't stop the deterioration. You have to treat the disease, not just make the pain go away.",
"I suffered knee trauma 20 years ago...and I asked why it never stopped hurting even though it's long since healed. And they said something about nerves always firing signals...and there is nothing they can do. I just have to live with the pain. Sometimes I feel like cutting off my leg would be the better option. If I ever do get rich enough...I will seriously try to get someone to make my knee stop hurting. I mean, I'm used to the pain by now. But it feels...worse and worse as I age. And the weather changes make it such that some days my knee is soo stiff it's hard to walk on it at all. It'd be nice to find some relief. But I'm already resolved to the fact that it's always going to hurt.",
"I did have a portion of my nerve on my little toe removed along with a calcium build up. Night & day. I cannot feel anything in a small portion. This was over 20 years ago."
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n3fnep | Why do we grind our teeth in response to pain or pressure ? | Biology | explainlikeimfive | {
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"there could be numerous reasons, but one may be a coping mechanism to distract yourself. Think of it like when you're really stressed out and squeeze a stress ball as a result, the stressful stimulus exceeds the resources you have to cope and you subsequently feel the urge to \"take it out\" on something physically to momentarily distract yourself."
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n3fszh | How can jellyfish exist without vital organs? | Biology | explainlikeimfive | {
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"Like all non-complex-animal-organisms, they don't need them. They either have simpler systems that take care of the same things our organs do, or a particular need just isn't relevant to them. For example, jellyfish don't need specialized systems to breathe, because their flesh is so thin and absorbent that all of their cells can just take in oxygen from the water around them. They don't need a central brain, because just having a few nerves spread around their body is plenty enough to be a successful jellyfish. Extra brain would take extra power. Etc."
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n3h037 | If math is a such a definite subject with solid answers, how are there still unsolved math problems? How do people even come up with them? | Edit: y'all have given me a lot to think about. And I mean a lot, especially as someone who has failed more than one math class lmao. I appreciate the thoughtful responses! Edit 2: damn, I'm glad my offhanded question has sparked such genuine conversation. Thought I'd touch on a sentiment I've seen a lot: tons of people were wondering how I'd come to conclusions that would bring me to ask this question. I'm sure it's not just me, but at least in my experience vis-á-vis the shitty american public education/non math major college, math ain't taught very well. It's taught more as "you have these different shaped blocks, and they each have a firmly defined meaning and part of that meaning is what they can do to the other blocks. Therefore we know everything the blocks can do, or can at least theorize it" and less "the blocks can be held and put together in infinite ways and be applied to infinite things that have yet to be fully imagined or understood and we're still coming up with new blocks every now and then". Buuut now I know that thanks to reddit! | Mathematics | explainlikeimfive | {
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"A pattern you'll notice with a lot of the examples given in this thread: often times the trouble is with **infinity**. If you ask for example, does the Fibonacci sequence contain any square numbers besides 144 (12x12)? I can write out the first couple numbers in the sequence, or have a computer generate the first billion - and each one is trivial to check if it's a square - but it's fundamentally impossible to check ALL of them, because the sequence is infinite. The only way to solve such a thing is come up with a mathematical argument - a proof - that employs some clever logic to prove something about an infinite set. As a very simple example, consider the question, \"are there any even prime numbers besides 2?\". We can answer this by saying, *suppose there were such a number. Then since it's even, it can be divided by two - and since it can be divided by 2, it can't be a prime!* So we have proven something about ALL numbers, even though we never had to check them individually. A slightly harder problem in this vein, *is there a biggest prime number?* Problems like this arise all the time when mathematicians are just playing around - exploring patterns, asking questions, finding neat arguments that then lead to other natural questions. Some of the most famous unsolved problems are famous because, if we knew the answer, it would unlock truths about a lot of other related questions. (An example is the [\"P vs NP\" problem]( URL_0 ) in computer science). **EDIT**: Wow this blew up! Thanks everyone for the comments / awards.",
"There's a big difference between solving a math equation and solving a generalized math problem If you have 2 + X = 7 you can solve for X this one time and know that right here, right now, it must be 5 But the unsolved problems are wayyy harder than that. Fermat's Last Theorem was unsolved for a few hundred years it goes \"For any integer n > 2, the equation a^n + b^n = c^n has no integer solutions\" You're probably already familiar with the case of n=2, that's a^2 + b^2 = c^2 or Pythagoras's Theorem. But how do you prove that for n > 2 there are no integer solutions? You could try brute forcing it but what if it works out when n=51,437? You'd have to try literally every combination of numbers which is, by definition, infinite Its problems like these that you can't just set a computer to and crush through the numbers, you have to fall back onto the basic properties of math and other postulates and theorems to show that there is no way that any n > 2 results in a, b, and c all being integers. These are the hard ones that require people and hundreds of sheets of paper to prove.",
"My favorite unsolved problem, because it's so easy to understand, is the Collatz Conjecture. We have a game that goes like this: 1) Pick any number and check if it's even or odd. 2) a) If it's even, divide by 2 2) b) If it's odd, multiply by 3 and add 1 3) Take your new number and go to step 1. For example, if you start with 10: 10 - > 5 - > 16 - > 8 - > 4 - > 2 - > 1 - > 4 - > 2 - > 1... Starting with 10, you end up going to 1 and then getting stuck in a loop between 4, 2, and 1. If you start with 9, it takes 20 steps (and goes all the way up to 52 at one point), but it also goes to 1. The conjecture is: **Every positive whole number eventually reaches 1 when using this pattern.** To _disprove_ this, all you have to do is find some starting number that gets stuck in a different loop. We've tried that, though - we've tried every number up to 20 digits long, and they've _all_ hit the 4,2,1 loop. To _prove_ this is true, though, you'll need to come up with some creative insight about the way that numbers relate to each other.",
"Unsolved math problems aren't just difficult equations that you can solve with algebra. They are questions that require creativity to solve. A well known unsolved problem is the Goldbach Conjecture: prove that every even whole number over two is the sum of two prime numbers. People have been working on that one for 250 years.",
"Sometimes, even if there is a solid answer, we don't have the ability to get to it. Take Chess for example. What's the best move at the start? There has to be an answer, even if that answer is \"multiple opening moves lead to a draw/win\". However, we do not have the computing power to go through all the possible moves that could prove the answer to this question. That's an unsolved problem. We can come up with many of these very easily, just by asking \"given a set of rules, is a statement true?\" And if that question hadn't been asked and answered, then presto, you have just found an unsolved math problem.",
"You are thinking about math as the set of tools needed to solve a specific problem that has to do with numbers. That's an accurate description of the math that people are taught in school. However, when you are doing math in university (\"real math\", if you will), you understand that the scope of the subject is very different. One thing worth noting - most mathematicians will disagree on what even is a proper definition of mathematics. For what it's worth, I will give you my own definition: math is the process of deriving properties from axioms and definitions. In more ELI5 terms: math is about creating rules and definitions, and seeing what interesting consequences follow from those rules when applied to those definitions. If you think about it in these terms, then you can see how open ended the subject is. You can come up with your own definitions or rules, see how they fit in the existing rules or definitions that other people agree upon, and see if using your own stuff creates any interesting results. As an example of this happening in real life - mathematicians used to think that infinity was just an absolute concept. But Cantor showed that if you looked at two different infinite sets and tried to match their items one by one, you could come up with some sets that would have infinitely many \"unmatched\" items left over even after you ran out of items on the other side. So he came up with a definition for two different types of infinity, based on whether you could match items of different sets with one another without running out of items on either side. So then lots of questions crop up - can you find some properties that only one type of infinite sets have, but the other one doesn't? I hope this gives you a sense of how and why the subject is open ended - mathematicians can come up with interesting new definitions and ideas, and then as they apply existing rules to them there is a whole host of questions that crop up about what general statements can be made.",
"Here is a fun concept for you. Gödel's incompleteness theorems basically prove that there are things which are mathematically true which can never be proven to be true. What a concept! We know that there things where not only does no proof exist, but no proof can exist, despite them being true. Given this, there will always be things we can never prove to be true or false.",
"While you might think that this is a simple question because you don't understand math, you have actually just stumbled on one of the most incredible and complex mathematical topics to exist! See, back in the day, starting from some of the original Greek mathematicians, there was an idea of how to solve math problems. Not just one or two math problems, but all of them. The idea is that you start with a few base assumptions that you know are true but aren't really provable called axioms. A proof is then built up out of some combination of these axioms. The idea is that you could go through every combination of these axioms to find every possible proof out there and solve everything that can be solved. This concept is called completeness and was embraced by many, if not most, mathematicians. However, as recently as 1931, the mathematician Godel proved that mathematics was not complete. In other words, Godel's incompleteness theorem mathematically proves that you cannot prove everything that is true in mathematics. So not only are there still unsolved math problems, but there will always be unsolved math problems, even with infinite computing power. On a related note, soon after that, an impossible math problem was also found. It was proven that you cannot build a program to detect whether a program has an infinite loop in it!",
"One thing to consider is that all the math you've learned had to be discovered by people who came before you. At some points in the past, people knew how to do some geometry but hadn't figured out the quadratic formula, for example. We have a similar situation now. There are things we know already and things we'll discover in the future and things that will never be discovered.",
"The math most of the world learns and the math that academics studying math study are completely different maths. The vast, vast majority of us learn \"how\" math works. We learn the methods and formulas that explain the world around us, the ones we've known and understood for, for the most part, hundreds of years. It's what we need to navigate a 3 dimensional world with an economy. Sometimes we learn slightly newer fun tricks you can do with math, without really going deeper than the surface level of the trick. Academics are studying \"why\" math works. They look into the rules governing math and what it takes to break them, and what breaking the rules tells us about math. Unsolved problems in mathematics aren't the same as the algebra homework you forgot to do. They're things that either work or don't, and we're still trying to figure out *why.*",
"Somebody just asked the $64 bazillion question. I love this, and it's so far beyond ELI5 (and I'm late to the game) that I'd like to take a long-winded stab at it! Let's start with a simple example. \"What does 1 + 1 equal?\" You might emphatically say \"two!\" It's obvious, right? Not so fast! It turns out we have to define 1 (One) first. Like, philosophically. It might seem obvious what \"1\" is but we must remember that in all the time that the concept of \"1\" has existed, *most of the time the number 0 had not been conceptualized*. That point aside, we must now, if we wish to define \"1 + 1\", decide what \"+\" means. This is called an \"algebra\" and was philosophically pioneered by some brilliant folks quite a while ago. We *could* create an algebra wherein 1 + 1 = 5, and that's been done before. But it turns out that it's not very useful. It turns out that 1 + 1 = 2 is correct only because it *works* and is *proved* to work. Something like 50 pages of *Principia Mathematica* (a philosophical treatise) are dedicated just to establishing through logical proof that 1+1=2. So, please feel free to go read through that rigorously (I haven't done that myself, by the way, I just take its word for it). Now, that being said, next comes say, 2 + 2 = 4. Based on 1 + 1, can we prove that 4 is correct? How so? If we multiply all three numbers by 2, does everything work out? It does! That's cool! Can Pythagoras prove that a^2 + b^2 = c^2? Moreover can we say that a^n + b^n = c^n if and only if n = 2? At each branch, more questions come up, more proofs are needed, and more discoveries can be made. Algebras and Calculi have cropped up for various purposes. And here I am. I made it through Calc 2 and Linear Algebra, and when friends of mine have talked about their Doctorate theses I just smile and nod because I have no idea how n-polytopes tesselate in parabolic n-spaces. Or, for that matter, why 1+1=2",
"Surprised nobody has mentioned Goedel's incompleteness theorem: URL_0 It was established almost 100 years ago that there must be at least some mathematical theorems which are true but unprovable.",
"Just because a solid answer exists (which may not always be true) doesn’t mean we have the methods to find it or more importantly prove it. There are a lot of problems which are very easy to formulate but we don’t yet have the techniques to solve.",
"Your question could be replaced by \"if alphabet, vocabulary and grammar are so well defined, how are there new books written every year?\".",
"A great YouTube channel for starting to think about math in a more general way and appreciate the beauty in the field is 3Blue1Brown. Highly recommend.",
"Math is the study of what's true. You start with a few obvious things that you know are true, and from them you prove new things, which are also true. You can use those new truths to prove more things, and so on. It never stops, unless you want it to.",
"The best explanation I ever heard was this: Imagine you're brought into huge, dark mansion. It's impossible to see so you fumble around the main entrance before finding a light switch. Ah, ok. There is a hall before you that stretches off into darkness. You decide to open the first door you can see and begin searching this new room. More darkness. You carefully walk inside, trying to use the little light from outside that you can. You hit your knee on strange furniture, reach out into the blackness for anything to steady yourself on. After a long time, you find the switch and AH HA! The room looks almost how you imagined it in the dark. You keep doing this for hours, days, weeks... years. The mansion is unending. The rooms and branches of the mansions are like branches of mathematics. Many are already known, studied, and understood. You can continue to analyze these if you wish, but there are more rooms, more branches, that are barely understood. Some are still unknown. Good luck.",
"Generally speaking, most high-level math problems are proofs. Proofs are far less like finding solutions and more so like discovering the laws of mathematics itself. Solving one, depending on it's implications, is akin to discovering Newton's laws of physics. We don't tend to say we have solved a proof. Instead we prove it. Hence many are unsolved and are, for lack of a better word, hypothesis waiting to proved right.",
"Mathematics is a Hydra. Everytime we solve a problem, we see at least 2 new rising up from that.",
"The beauty of Math is that if it says something, you can trust it. Math doesn't lie and the biggest pre-requisite to being good at Math is to be able to handle it pointing out your lies ruthlessly. The downside of that is, it makes it difficult to say everything which might be true because we don't know if it is true yet. The most common example of this is Fermat's theorem, it was really easy to say, a lot of people assumed it to be true but nobody could say that it was true until we proved it, fair and square. Now, as to how are there still unsolved math problem, the answer are the damned 'for all' operators - the difference between propositional and predicate calculus. Propositional calculus is solved, but just adding the ability to say something for all elements in an infinite set is hard, really hard. In fact, for any Mathematical system, there will always be a proof which is beyond its capabilities, it's own correctness. (It's proof is beautiful! Have a look around if you are interested- URL_1 . Also URL_0 ) > How do people even come up with them? They dream stuff up. Imagine a full ass grown up man sitting on a table with a paper and a pencil and dreaming about higher dimensions. That is probably how most Math problems were born.",
"I asked that question in high school. My teacher was an amazing guy. His answer: To get it really right, you need 2 things. 1 The right answer and 2 the right question. We don't always know enough to know what we need to know. May not be the answer you for you, but he really made an impression on me that day. I still think of his class when I think about how far humanity still needs to go.",
"Different types of math can or cannot be \"solved\" completely. For example, calculating PI, which is half of the number of radii that could be fitted into the circumference of a circle, if the radii were squished out to the sides, can't be solved to perfect precision.(The answer isn't 3.0, it's 3.141 < a bunch of decimals > .) This would be an example of something that can be solved, but not completely. You can always be more correct with effort and time. & #x200B; On the other hand, calculating the number of apples in a bag if Percy the horse eats 2 is easy. a=apples p=percy's share x=how many apples we have x=a-p If we know percy ate 2 and we bought 10, x=10-2 therefor x=8 I think this is called \"discrete math\" but I'm no mathematician so I may be corrected on that. & #x200B; I hope this helps. Sorry if it doesn't.",
"I'd argue with the premise here that math is a definite subject with solid answers. At the more primary levels, it's true that you're learning a lot of basic algorithms that you can just follow to get \"the answer\". 9x6 is 54 -- that's a true statement you can learn and learn the general principle that makes it true, and you can then apply that to answer other similar questions in a way that's easily determined to be right or wrong. At the level that professional mathematicians are working (and therefore where you're dealing with open questions), this isn't what mathematics really is anymore. Math is the study of systems of principles and rules to determine how you can derive true statements from them. Let's take an example here. We know that there are rational numbers and irrational numbers. Rational numbers can be represented as a ratio of integers (like 3, 0.5, 0.33333..., which can be represented as 3/1, 1/2, and 1/3 respectively). Irrational numbers can't be. You can further assume that those integers cannot have any common factors, because if they do, you can just simplify the ratio. That is, while the rational number 4 can be represented as 32/8, 32 and 8 have 8 as a common factor and we can just divide both by 8 to get 4/1. Is the square root of 2 rational or irrational? The answer, one way or the other, is a fact. It's a defined solid answer. But you don't know whether the answer is yes or no. How would you figure that out? The famous proof that sqrt(2) is irrational goes roughly as follows. Assume sqrt(2) is rational. Therefore, there must exist integers p and q with no common factors such that sqrt(2) = p/q. Let's square both sides of this equation to get 2=p^(2)/q^(2) or 2q^2 = p^(2). Since p^2 equals 2 times something, p^2 must be even, which means p must be even. But if p is even, then p=2k for some k, and p^2 = (2k)^2 = 4k^(2), which means p is divisible by 4. Now for q. We have that 2q^(2) = p^(2), so q^2 = p^(2)/2. We have that p=4k for some integer k, so we can write this as q^2 = (4k)^(2)/2 = 16k^(2)/2 = 8k^(2). This tells us that q^2 must be even, because it equals 8 times something. Which means q must be even. But now I know that both p and q are even, which means both are divisible by two, and that violates my original assumption that I had sqrt(2) = p/q with no common factors between p and q. One of two things has happened here. Either I've made a mistake somewhere in my argument, at which point the entire conclusion is suspect, or else my assumption was invalid from the beginning, and there really can't exist those numbers p and q such that p/q = sqrt(2), making the idea that sqrt(2) is rational provably false. How does anyone know which of the two things has happened here? The answer is that math is full of this kind of thing, and the solution is that tons of other mathematicians pore over your arguments trying to find any mistake you might have made. Maybe I was wrong when I said that because p^2 is even, p must be even. Can you convince the rest of the mathematical world that I wasn't allowed to make that leap under the rules of the standard arithmetic system we all use? If so, then we'll all agree that my proof was invalid and we don't in fact know whether sqrt(2) is rational or not yet. But if enough people agree that they can't find any errors, then we all agree that I've solved the problem of determining whether sqrt(2) is rational -- it's not, and I've provided the proof of that fact. This is what mathematics really is. It's a bunch of people trying to build arguments to convince other knowledgeable people that they've come up with a way to answer a question that no one really knows the answer to yet. And that process is absolutely not just a set of easily defined facts like 9x6 = 54. It's a creative process. Nothing told the first greek a couple thousand years ago that he should start by assuming sqrt(2) = p/q. That was a leap that person took on the hunch that by exploring that idea, he could solve the open problem of whether the diagonal of a 1x1 square was a rational number or not. An open problem is one where no one has yet found the right creative leap to make that led to an argument the rest of the mathematical world can agree is a correct proof answering that problem one way or the other.",
"The same way you physically exist and are real and definite. Yet we know next to nothing about how humans evolved or why the universe exists.",
"You know how to walk right? When I tell you to move 5 steps forward and 2 to the left, you can manage. Now walk to the holy grail. You neither know the solution nor if there is one at all.",
"The unsolved math problems are often precisely because of the rules. Sometimes you have a hunch, like a certain pattern, but you're not sure if the pattern holds forever even if extreme conditions, and you can't proof it. That's an unsolved problem until someone finds a way to proof the pattern holds. A problem is only solved if there is rigorous proof for it so that it works in all cases.",
"Sometimes, what seems simple and clear in one context becomes difficult and muddied in an other. This change in context creates new problems to be solved. As an example, a paper that came out of my graduate work extended the idea of finding eigenvectors and eigenvalues to 8-dimension, using the octonions. In 3-dimensional space, eigenvectors and eigenvalues are well understood, as is the process of finding them. Moving to the octonions complicates algebra in basic ways, making the eigenvector and eigenvalue operations a new, more challenging problem. There are many examples like this, making for an endless list of things to learn.",
"“Unsolved math problems” would be better described as “unproven theories”. These theories need to be proven in order to be “solved”. Once it is proven/solved, then it absolutely is a “definite subject”, as *that* is the answer and the only correct answer. That correct proof can’t, obviously, be incorrect. This isn’t to say something can’t be proven in multiple ways, as they definitely can be. The reason these theories need to be proven is math builds on itself. Similar to how learning what multiplication is would be impossible without knowing addition. Or learning what powers are without knowing what multiplication is. It can’t just seem to be right — it has to be proven to be right.",
"In early 20th century, mathematicians tried to create a system to systematically prove any theorem, and compute any function (see Hilbert's problems). They were only able to come up with theorems which proves that the above tasks are **not** always possible. 1. Godel's incompleteness theorem- Not all theorems can have a proof. This means that even statements which are true may not have a proof (This is quite unintuitive, and also shook the mathematics at that time). 2. Turing computability theory- There are functions that can not be possibly computed/evaluated. Both these theorems are simplified, but capture the idea well in my opinion :) So to answer your question, mathematicians asked themselves the same question around 100 years ago and realised that it is not even possible to solve all problems!",
"Mathematics is at its root a philosophy. In its application it is a system of patterns that attempts to quantify, qualify and codify the patterns we observe in the world around us. So it is a pattern that seeks to explain patterns we think we see (it already sounds like a leaky sieve). The power of Math to explain things lie not only with the person applying the Math* but also in what they are observing and how the are observing. Conventional Math is weak when exploring the really small, the really big, the rally fast moving and probably a whole host of other things we have yet to discover. If a people choose not to apply Math to certain things or have yet to observe/discover a thing then that is reflected in the Math. *Ancient peoples mostly sought to describe that they had another child, killed another wolf, harvested another apple; and/or why this particular stitch is the same stitch as another; and/or ways of tying rope for different applications; and/or the fastest way/how to get from the cave to the waterhole; when to leave an area or plant a crop. This is reflected in our Math today. My point is that how Math is applied and what drives our discoveries is dependent on what is important to us, on how/what we think. Math is a reflection of our values, what we think we know and what we see. As our ability to observe and/or our knowledge base increases we come up with new Math to describe the world around us. As our values change how our Math is expressed may also change. Math isn't this bastion of truth, is it limited by the minds who create it, by the environment it seeks to describe and by the society that applies it.",
"Lots of answers have been given so far, but I'd like to share a bit about how we think of these problems to begin with. As an example I'll explain the context behind [Hilbert's 13th problem]( URL_0 ), because it's accessible to anyone with a high-school level of education. I'm sure you remember from school, learning the quadratic formula to find the roots of equations of the form ax^(2)+bx+c=0. From here, we can ask a harder question - what's the formula for equations of the form ax^(3)+bx^(2)+cx+d=0? This was solved in late medieval Italy, as was the case of the degree 4 (highest exponent is x^(4)) equation. The, for some centuries, it remained an open problem as to the formula for the degree 5 case. Enter Evariste Galois, a French mathematical genius living in the 1830s. If you think that rock stars live interesting lives, look into Galois - he'll give most of them a run for their money, and he beat the 27 club by most of a decade. Anyway, he invented a field of math called \"abstract algebra\", and used it to prove that there is no formula for degree 5 or larger equations in terms of addition, subtraction, multiplication, division and nth roots. An example of such an equation is x^(5)+x+7=0. So, how do we find the roots of degree 5 equations? Returning to x^(5)+x+7=0, we can define the [Bring radical]( URL_1 ) to be the root of that equation; that is, BR(7)^(5)+BR(7)+7=0, or more generally for any number *a*, BR(*a*)^(5)+BR(*a*)+*a*=0. This is part of a larger class of functions called \"algebraic functions\" - an algebraic function returns the root of a polynomial equation. It turns out that degree 6 equations can also be solved using a class of algebraic functions, called [Kampe de Feriet functions]( URL_2 ), which I am not qualified to speak about. The problem that I mentioned, Hilbert's 13th, which is still an open problem, is whether degree 7 equations can be solved in terms of algebraic functions of 2 variables. That is, if you know the roots of (say) x^(7)+*a*x+*b*=0 for some *a* and *b*, can you use that to solve any degree 7 equation?"
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n3hom4 | How do ball bearings work? | Physics | explainlikeimfive | {
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"Something needs to rotate and needs support. A ball bearing has the rotating part on the inside and the stationary support on the outside, with steel balls between them. Balls roll very easily so you aren't losing a lot of power to friction, and spheres are a strong shape so they can handle a decent load."
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n3hvbz | YouTubers usually use videogames' music as background for their videos. Does it mean that those songs aren't copyrighted? Why can those songs be used and videos be monetized, compared to other songs from famous artists? | Other | explainlikeimfive | {
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"In simple words, I think video game companies don't use YouTube-Takedown mechanisms because they would also take down videos of creators from which they get free advertising (let's plays, etc.). It may be not possible to separate those from the uploads of creators who are just using the video game music for other kinds of uploads. However, those songs are still copyrighted",
"> Does it mean that those songs aren't copyrighted? **No**, it does not! They most often *are* copyrighted, and the game developers don't have the right to *grant* the right to Youtubers or to Twitch streamers (or anyone) to broadcast their music. Youtubers and Twitch streamers have gotten in bunches of trouble lately over just this thing, and it's led to a rise in awareness among content creators and game developers. > Why can those songs be used and videos be monetized, compared to other songs from famous artists? Legally, they can't. But it's a question of enforcement: who goes and issues takedowns against the creators? Sometimes, people don't, and sometimes, people do."
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n3hzvg | How does seeing images in your head work? | Other | explainlikeimfive | {
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"Your eyes are photoreceptors. They receive sensory information but cannot process it. The information received from the eyes must be transmitted to the brain for interpretation. So it is your brain that makes the image. You can “see” the apple in your head because you remember an apple you have already seen. You may also be able to imagine one if it were described to you. In either case, your brain creates the image, not your eyes."
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n3ih0r | What's the main difference between ADD and ADHD? | I've always had a hard time paying attention, I know I don't have ADHD so I'm thinking it's just ADD, but I don't really know the difference. Could someone give me a simple explanation? | Other | explainlikeimfive | {
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"Nowadays, doctors don't tend to diagnose ADD. There is ADHD, which is split into 3 types: ADHD-Hyperactive: symptoms of impulsivity and some inattention, with a significant amount of hyperactivity. ADHD-Inattentive: impulsivity without the hyperactivity, predominantly inattention. I've heard it called \"hyperactive mind\". This is what used to be called ADD. ADHD-Combined: the most common subtype, elements of both inattention and hyperactivity.",
"Technically ADD isn't even a thing anymore, ADHD is split into three categories. Attention Deficit, Hyperactive, and Combined. So if you dont believe you fall into the hyperactive category you could also just be attention deficit. Hyperactivity isn't just bouncing off the walls energy all the time either though. I'm diagnosed combined type and I was never like that. However I constantly fidget and am quite restless which are both signs of Hyperactivity."
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n3iik8 | How linear are the planets in our solar system? | All space models used in school are always 1D that show the planets in a straight line. For simplicity sake it makes sense too look at it that way, however if we drew it in 2D how far off center would the other planets fall. Or do all planets more or less line up? If so what is the cause of this? Edit: thank you for the explanation. You are all great as always. | Physics | explainlikeimfive | {
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"The planets move around the Sun, at varying rates. So even though they line up (more or less) sometimes, they don't stay that way. Compare them with the hour, minute, and second hands of a clock. Sometimes they line up, but usually not.",
"So, they rotate at different angular velocities, so they can't be lined up all the time. However, they all lie more or less in one plane which is because before there were planets, we had a thing called \"protoplanetary disk\" - basically a disk of smaller objects orbiting the sun (I imagine it a little bit like the Saturn rings). This forms because (a) there is conservation of angular velocity, so the initial angular velocity of the system stays and (b) gravity pulls objects outside of the plane towards the plane, effectively forming a disk even if the initial distribution of objects wasn't. Finally, those objects combine to planets which retain an orbit in that plane or close to it. The deviation from this plane, called inclination, is no bigger than \\~7° (Mercury) for the planets in our solar system.",
"You can see the inclination for all planets here, all are within 10% of each other. URL_0 You are right though, gravity gives generally no reason for why all the planets have to be on the same plane. Things are a little more complicated than that and rely on a bit of geometry. The reason is that any other configuration is unstable. All planets have to orbit the sun, and if one planet had its inclination too high or too low, it would pass into the orbital plane of the other planets and the resulting close approaches would either collide the two objects or the close gravity would eventually pull them into the same plane. This was a lot more present in the early solar system when the solar system was just a bunch of gas and dust, but point is a disk is the only stable way everything can work."
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n3j1uk | How do Plasma Balls from Spencer's work? | What makes them congregate to a fixed point? Why do multiple touch points create multiple lines? | Physics | explainlikeimfive | {
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"If I recall correctly it works like this: the glass ball is a little bit conductive, so is the air and your hand. But all slightly different. So by holding something onto the glass, the Arc inside now has a different path to the outside. The limited conductivity of the glass prevents you from getting fried."
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n3j3i2 | How exactly does burning cds work especially when you do it from home? And why does a scratch affect how the cd reads the information? | Technology | explainlikeimfive | {
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"When CDs are pressed commercially, they actually punch tiny tiny holes in the gold foil, and those punches represent the information that becomes the music. When you burn a CD at home, you can’t punch holes, but the laser in the CD burner affects the foil and burns it and discolors it, so that it looks just like a hole to the CD player. A scratch in the plastic or in the foil destroys some of those holes, or it makes it harder for the laser to see them clearly.",
"A CD is made up of a reflective metallic film deposited on a transparent plastic substrate. A CD burner has a high intensity laser that can physically alter the properties of the metallic film, specfically change the phase of reflected light by etching microscopic grooves into the reflective metal film. A disk reader can later shine a low-power laser light on the rotating disk, then 'read' the phase of the reflected light, thus reconstructing whatever data was written on the disk. A superficial scratch that only penetrates the plastic substrate will simply cause the light to bounce off and reflect away from the reading head and thus corrupt the data. The data could still be salvageable, and the disk may still be repaired. A deeper scratch that reaches the metallic film will irreversibly corrupt the data because it will mess with the grooves created by the burning laser."
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n3jxbv | How is Wi-Fi "shared" to multiple devices? | With a wired connection, it seems pretty straightforward. Multiple devices are connected via multiple wires to a home router. With a Wi-fi connection, how do multiple devices connect to the home router. Is it like multiple devices are connected to a one large wire (that is the air)? | Technology | explainlikeimfive | {
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"Multiplexing. There are lots of different ways multiplexing can be accomplished, one example is time sharing. In other words, each device gets multiplexed for a certain time slot (often small enough time slots as to be imperceptible to us; it can be fractions of fractions of a second) in order to share the load of multiple connections at once."
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n3k4yx | how does binary work? I've had it explained to me twice at my current age and I didn't get it... | Technology | explainlikeimfive | {
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"Its just a base 2 number system. We have a base 10 number system 0-9, and when you reach the end of the system you add a digit and start over. 9, 10,11. Binary does the same thing, but you only count to 1. 0,1,10,11,100,101, etc."
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n3kyid | why does clay harden when heated instead of melting? | Chemistry | explainlikeimfive | {
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"Clay that can be easily sculpted is a bunch of extremely small rock/earth particles mixed with some water. The layer of water between all the particles helps them stick together even when you push and sculpt them. When a clay object dries out, you end up with particles which are just resting in a big pile without any water to hold them together, which is why air dried clay is really easy to break - there's nothing holding the particles together. During the firing process in a kiln, all the little particles in the clay fuse together (the easiest way to picture this is a bunch of spheres melting just a bit on their outer surface and then all those molten surfaces sticking together).",
"Some of it does melt! Clay is kind of like a rice crispy treat - there are some microscopic particles that don't melt (like the rice crispy cereal) and others that do melt (like the marshmallows and butter).",
"The same reason eggs don't melt...clay hardens at low temperature, but when you heat it up to high enough temperature without oxygen it will melt at about 1780C! Fun fact: stuff an egg in a vacuum and heat it up to about 825C and it will melt."
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n3l266 | If only a small percent of the Earth's water is drinkable, will we ever run out of drinking water? | Earth Science | explainlikeimfive | {
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"Run out completely? No. At least, not if we avoid polluting literally ever drinkable river and stream and pond. Outstrip the supply? That’s already happening in many places. A huge drought that made a shortage of drinking water is one of the main causes of the Syrian civil war. It’s even more noticeable in desert countries like UAE that have no real natural sources of water, so they have to desalinate sea water (an _incredibly_ expensive endeavor). On a smaller scale, there are huge aquifers in the Midwest that farms are emptying faster than they can fill, so many are investing in drought-tolerant crops that need less water to grow in the first place. So... no, but also we need to plan how we’re going to get that clean water to people that need it.",
"No because water evaporates then falls back as rain it replinishes what we use. The clouds over head come from water in the ocean.",
"Yes. If we continue to over-extract for mining, inefficient agriculture and so on while the population continues to grow, eventually there will not be enough to go around."
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n3l6vf | How Does a Computer Know Where a File Is after I Save It? | Technology | explainlikeimfive | {
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"A computer keeps track of files similarly to how we put papers in a folder and put the folders into a filing cabinet. On your operating system, like Windows or macOS, files are put in a folder, which can be placed in another folder and so on. [As Chris Hoffman explains on HowToGeek]( URL_0 ), the largest of all these folders is called the root folder. Everything on your computer is inside the root folder (or inside a folder inside the root folder), and it’s where the computer starts when it goes to navigate to a file. In another [HowToGeek article]( URL_1 ), Chriss Hoffman states that our operating system uses a file system to track all those folders and files. Before describing a file system, we need to understand how memory works. Memory can be thought of as a line of boxes. As Carried Annie explains on [Crash Course]( URL_3 ), each of these boxes represents a specific location in the physical memory of a computer, like a few magnets on a hard disk or a cell in a solid state drive. How memory is physically stored isn’t that important for us though, because our computer handles converting from imaginary boxes to memory locations. Most files are too big to fit in one box, so we need to break up the file into pieces small enough to fit in a single box and store all those pieces across many boxes. In his [public textbook on Linux]( URL_6 ), Lars Wirzenius explains that computers create a list of boxes that a file is stored in to track files that span multiple boxes. We call this list an inode and every file has its own inode. This isn’t the sole purpose of an inode, as inodes also store who created a file, when it was created, and other properties. Finally, each inode has a unique number, called an inode number. These inode numbers allow us to keep track of all the different inodes. Folders work differently on a file system level. As Remzi H. Arpaci-Dusseau explains in his [textbook on operating systems]( URL_5 ), What we call folders are actually a certain type of file called a directory and they have an inode of their own. These directories are similar to phone books. A directory is a list of inode numbers and names of the files they correspond to, just like how a phonebook is a list of phone numbers and names of people that they correspond to. For example, the documents directory would link inode #12352 to passwords.txt the same way a phonebook would link 911 to emergency services. Arpaci-Dusseau also explains that the crux of this system is that directories can contain another directory, which allows for the creation of subdirectories and a tree-like structure for all the files on the computer. In other words, directories tell us what inodes to look at and inodes tell us what boxes to look in to find the file. To go through an example, let’s say I have a “passwords.txt” file stored in the address “/Users/Bob/ Documents/password.txt.” To get to passwords.txt, the computer starts in the root folder and looks at the root directory inode to see what boxes it should look in to find the directory. Then, the computer goes to those boxes and reads the data of that directory to find the inode number for the Users folder and navigates to that folder. The computer then repeats this process until it gets to the Documents directory and locates the password.txt inode. Using this inode, the computer finds all the boxes passwords.txt stores its data in and loads the data from those boxes. For further information, please check out this [infographic ]( URL_2 )and [video]( URL_4 ) my friends and I made about file systems."
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n3lkjw | Why do certain ailments such as carpal tunnel, plantar fasciitis, or other diseases not simply recover over time assuming one is still healthy? | Biology | explainlikeimfive | {
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"Generally, with these sorts of ailments, the damage can be irreversible. Take arthritis, for example. Over time, the cartilage in your joints will wear down. Since the cartilage cannot grow back, no matter how otherwise healthy the individual may be, they will always have arthritis. There are medications and other remedies to make the pain less severe, but what’s gone is gone. It’s essentially the same idea as losing a limb - if your arm is cut off, you will not grow a new arm. Our bodies are simply incapable of repairing certain things."
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n3lm08 | Why does the skin on our hands tend to crack and become dry in very dry and low-humidity environments? | Biology | explainlikeimfive | {
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"Your skin isn't a perfect barrier to moisture. Just like your skin swells up with water until your hands become all wrinkly in a bath tub, moisture from your skin leaks out into the dry air in low humidity environments."
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n3lwhn | how does wind get inside of courtyards? | so i live in an apartment complex thats like, a square shape and theres a courtyard in the center with no access to outside of the building except for the top opening if that makes sense. im confused about the concept of wind blowing up and downc and not just side to side, but i can accept that. but is there any explanation for how wind goes all the way down into the courtyard and can still blow side to side inside of it with not horizontal access to the world around it??? | Earth Science | explainlikeimfive | {
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"Try to thank of it like water. The wind coming down is hitting something, making it splash in a different direction. This might make it feel like it's coming from the left instead of from above.",
"Convection currents. Basically, all natural wind is caused by convection currents, which is essentially the cyclic rising of warm air and sinking of cool air. This is especially true near oceans mainly due to the uneven heating speeds of water and land (have you ever noticed that coastal areas are windier?). Of course, wind doesn’t only happen in areas near bodies of water. Uneven heating is everywhere - different soils, different moisture levels, different elevations, and so on. So, even if your courtyard contains no water, there is still uneven heating and thus the currents continue."
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n3ma83 | how exactly is silicon programmed in Computer chips? | Like, who went, oh yea let me just put some electricity into this rock and make it think for me? I like to think I know my way around a computer but at the end of the day how do manufacturers go from metals and rocks to cpus? How do you make electricity make silicon think? Thanks! | Technology | explainlikeimfive | {
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"You don't make it think. It's a machine just like the ones that you more intuitively understand. The front gear on a bike pushes a chain that pushes the rear gear which pushes the ground. Similarly, the semiconductors in a computer is the same way. We found that by doping silicon, they would have specific properties when you apply electricity, much like how metal has specific properties when you apply force to it. Even then, we didn't use silicon as the first computer. Much earlier than that we had mechanical devices. You can look at mechanical calculators that function similarly to current day calculators, but they relied on a bunch of gears and whatnot. After that there were things like vacuum tubes and magnetic core memory. Only later did silicon chips become usable. Like any complex machine it's an iterative process where you come up with little pieces that do what you want (burn gas in a container to generate power, use a system of gears to magnify force) and put them together to get a big complicated machine (a car). So how do computer chips work? You can dope silicon to add certain other atoms into it and change its properties. There's a type that has more electrons than it wants (called N-type) and a type that has less electrons than it wants (called P-type). The interesting thing is that when you stick pieces of these together they behave in unusual ways. A piece of p-type next to an n-type makes a one way gate for electricity, called a \"diode\". Layering three of them together either PNP or NPN makes a transistor. It's like two diodes stuck together opposite ways, so electricity can't flow through. The catch is that if you apply voltage to the middle piece, it messes with the behavior of the material so that it allows electricity to flow all the way from one end to another. This makes it work like a switch. It's just that instead of flipping a physical switch like you have for your house lights, you're applying voltage to a wire. The important thing here is that you can turn voltage off and on a lot faster than flipping a physical switch, and you can use one switch to trigger another. By arranging these switches (transistors) in different ways you can get them to behave in all sorts of complicated ways, such as having them do math or play Mario Bros.",
"Premise is really simple: you have an item (semiconducting cell) that has 3 electrical contacts. You can pass current through contacts 1 and 2, and it conducts the circuit. You apply voltage to 3, and it stops conducting the circuit. This was first done with much larger items than the modern nanometer scale semiconductors, you could make a primitive semiconductor as large as your fist from pretty basic materials. From a large number of those semiconductors, you can construct a system which can complete certain logical operations given certain input. So.... when you just have a basic logical unit in a microchip, which is essentially a very large array of semiconductors, it's pretty useless on its own. you need the \"firmware\", which in its most basic state sets it up to be ready for general-purpose work. Then you can use it to read instructions from a program, and execute them, putting the result into an output buffer memory, from which you can extract it and deliver to the next component, like a display. Tldr: you have a very basic cell which can switch \"on\" to \"off\" and back based on how you push electrical current through them. Put a giant pile of them together, push current in a certain pattern, and you'll receive a different pattern in output. Set it up to manipulate your input patterns in different ways, and you got a computer.",
"* The most important breakthrough for computers was discovering that every kind of logic decision and every kind of math problem can be broken up into a very long series of yes or no questions. * Google \"George Boole\" if you want to know more about how that works. * After that, it was matter of getting a machine to make those yes or no decisions based on some sort of input from a user. * At first, this was done mechanically. * Google \"Charles Babbage\" to learn about that. * At the same time scientists were playing around by shoving electricity through every different sort of material they could find. * They found out that you can change the way certain metals behave when you apply cleverly apply electricity to them. * These are semiconductors. * They figured out you could turn them into little electrically controlled electricity gates. * That is, when you apply electricity to one side, we'll call it the front, nothing happens. * But if you also apply electricity to the another side, it will let the other electricity pass through. * Boom! You have a device that can make yes or no decisions."
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n3mhe1 | why do dish washers take 3+ hours to clean dishes but the washing machine and dryer takes less than 2 hours to clean clothes? shouldn’t clothes be more difficult to clean? | Technology | explainlikeimfive | {
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"Dish washers used to be faster. Recent regulations on the amount of electricity they can draw slowed them down. A big chunk of time is also the heated dry time. So they do both, wash and dry, in about the same time a load of laundry is washed and dried. Thing Explainer by Randall Munroe has some excellent diagrams and explanation of how both dishwashers and laundry machines work.",
"The washing machine was designed to allow the clothes to clean and dry themselves by rubbing together really fast and spinning them. The friction heats them and uses the soap efficiently. You can’t very well rub glass dishes together so you’ve gotta use powerful jets which pass over and through the dishes more than enough times to sanitize them and protect the company from a food borne illness lawsuit."
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n3mlcw | the difference between a theory and a hypothesis | Other | explainlikeimfive | {
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"A hypothesis is just an idea. It has some reasoning behind it, but it has not been tested to the full extend of a wider scientific community. A theory, in the scientific sense, is something that is paramount to fact. Is it possible to disprove? Sure. You could disprove evolution by finding a fossil that's too old or far too far away from where it should be. But nobody has.",
"A theory something that you BELIEVE is right, because it is backed up by something. A hypothesis is something you ASSUME is right, for experiments, or arguments."
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n3mmk4 | can a airplane pilot put the plane in autopilot the whole time they fly? | Technology | explainlikeimfive | {
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"At the very least, takeoffs would still be flown by hand, since (to my knowledge) many jet's autopilots won't engage unless you are on a somewhat stable heading and are closely trimmed (flight controls set so that minimal yoke/sidestick pressure is needed to maintain the current path) to your current flight path. Landings are also often flown by hand after a certain altitude, since automated landings can be very firm and not every runway and plane is certified for automated landings down to touchdown.",
"Airplanes today can be flown mostly on automatic with my Pilot father admitting that many airlines consider pilots to be glorified troubleshooters. You're there in the cockpit in case something goes wrong. Many pilots prefer to fly manually, mostly takeoffs and landings, because its good experience and a human can react faster and adapt better than the computer to many changing circumstances. But many airlines, particularly in the far east, disagree and insist that pilots push the auto-pilot button almost the second the airplane is airborne because they trust the computer more than their own pilots.",
"Yes, and no. Yes that most of flight is done by autopilot. No that take off, landing, and any emergency is handled by the human pilot currently"
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n3ntq9 | How do mRNA-based human therapeutics work? | Biology | explainlikeimfive | {
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"TLDR: They trick your body into making the harmless part of a virus that your body then reacts to and learns to defend itself against. Traditional vaccines often use a weakened or dead form of a virus to teach your immune system how to fight a particular disease. mRNA vaccines use a different method. Your body is injected with mRNA building blocks, the instructions on how to make a part of a virus. This mRNA enters your own cells tricking them to manufacture the associated proteins, or in current context the spike protein on the surface of COVID 19. Your body then reacts to that protein as foreign and attacks it with antibodies, while learning to identify and destroy those proteins if it encounters them again. This has the advantage that you don't need to inject people with a live virus, it's actually a rather ingenious way of teaching your immune system. This has the potential of helping us make vaccines much more quickly, because we can much more easily make the mRNA instructions from a known virus than modifying a virus and the mRNA is by definition likely to be harmless compared to a genetically modified virus. In addition to being highly effective, there also potentially less side effects and a quicker recovery time. Contrary to conspiracy theories the mRNA cannot enter the nucleus of the cell and therefore can't reprogram your DNA. mRNA vaccines have a alot of other potential applications as well as they could be used to tag cancer cells for example to teach your own immune system to destroy them. They could also be used for viruses like AIDS that is notoriously difficult to make a vaccine for because of what it targets.",
"Rather than make some compound and give people an injection of it, mRNA injections cause the body's cells to make the compound inside the cells.",
"mRNA is like a recipe card. Your cells can interpret this recipe card to make stuff. Proteins, specifically. Proteins are like little robots or machines that your cell uses to get things done. Move things around. Send signals. Everything, really. Your cells make their own recipe cards by reading out DNA. DNA is like a cookbook that is carefully preserved in a library that only few \"people\" in the cell have access to. It takes the right credentials to be allowed into the library and copy a recipe onto a recipe card. This is an important part of how cells control what happens inside them. The recipe cards are designed to be flimsy. They don't last very long inside the cell. Once they've been used a couple of times, they basically fall apart (helped along by the cell's own recipe card-degrading machines). This is also on purpose. You don't want the kitchen in your restaurant to constantly be churning out salmon quiches if only one customer ordered them. Similarly, the cell needs certain things to be made at certain times. If the same thing needs to be made again after its recipe card has degraded, the cell will just get a librarian to copy out a new recipe card. Now, the \"chefs\" inside the cell aren't very smart. They don't need to be. Normally they can rely on the librarians to give them the right recipe cards. Once they get a recipe card, they just make it, no questions asked. But this means we can hijack this system, if we can just smuggle a recipe card (piece of mRNA) into the cell. And that's what mRNA-based therapeutics do. Instead of the regular recipes, they smuggle in their own recipe card(s), to get the cell to make stuff that has some desired therapeutic function. For instance, in the case of mRNA vaccines, the recipe cards that get smuggled into your cells are for little pieces of virus. Your own cells then start making virus-pieces (not complete, dangerous viruses), and your immune system recognizes these pieces as a foreign invader. This allows your immune system to become familiar with these virus pieces, so that they are recognized faster when you get infected with the real virus."
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n3om1v | What's the difference between a 4/4 time signature and a 8/8 or 16/16 time signature? | Mathematics | explainlikeimfive | {
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"Time signatures are just a composer’s method of telling musicians how to best count the beat. In 4/4, most, but not always all, of the important stuff (drum beats, accented notes, chords) falls on the quarter note beat. 8/8 time says that there’s important stuff on the 4/4 off beats that makes it easier to count the eighth notes instead. For example 4/4 is nice for playing a 1 **2** 3 **4** sorta thing, but 8/8 is better for a **1** 2 3 **4** 5 6 7 **8** kinda pattern where it’s a lot easier to figure out how to play a song when you don’t have to remember which e & a’s to pay attention too.",
"Think of it like measuring cups. 1/4 cup would be the equivalent of a 4/4 time signature, you’d have four beats in X amount of time. Now imagine using a 1/8 cup in the same amount of time, that’s an 8/8 signature, it’s going to be double as fast with 8 beats in X amount of time"
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n3p9h8 | How does a evaporative cooler work? | I have always wondered how coolers work.I think they use evaporation to cool the air but I am not too sure about this.Can someone please explain? | Physics | explainlikeimfive | {
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"When you leave the shower and enter a cool room, you feel way colder when your skin is still wet, than later when it dries a little. That's because evaporation is endothermic, which is to say that for a droplet to evaporate, it \"sponges\" heat away from its environment. In this case, it's on your skin, so you're the environment it steals heat from. That's the basic idea - create a film of liquid and as it evaporates, it'll cool the surface it was on. [EDIT] I suck at Latin."
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n3ph4r | How come as a kid you get scared more easily. And then as a grown up you don't seem to find those same things scary at all. | For example certain movies aren't that scary could be nightmare fuel for little me. But now as a grown up I realise those movies aren't scary at all. | Biology | explainlikeimfive | {
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"As a kid you have a much narrower experience of what is and isn’t dangerous or scary, and much fewer options of what to do when you’re in a scary situation; mostly you’re hoping there’s an adult nearby who will hear you crying and come help you. Everything seems scarier in those circumstances."
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n3qndv | If white is a combination of all colours, do people with red/green colour-blindness perceive white differently? | Biology | explainlikeimfive | {
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"No they still see white as normal. In your eyes you have 2 different kinds of cells responsible for receiving light and sending it to the brain as neural impulses. The first type are know as \"rod cells\". These are the cells responsible for black and white colors, and every shade of gray in between. They also use that information to detect the \"brightness\" of the light. The other type of cell is known as a \"come cell\" and there are three subtypes of cones, for red, green, and blue light detection. Those with red/green colorblindness have genetic defects in bith of those cone cells causing the activation of one to be difficult to detect from the other. So any color with any amount of red or green pigmentation will activate both cells and the brain won't be able to interpret the difference very well."
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n3s5k9 | Why do we subconsciously hold so much tension in our bodies? | I constantly find myself clenching my jaw even if I just unclenched it. I’ve done some yoga where we focus on each part of the body and let go of all the tension little by little. So why are we holding all his tension? It causes headaches and I’m sure other pain. It doesn’t make any sense. | Biology | explainlikeimfive | {
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"Stress activates our fight or flight response, which causes our muscles to tense because tense muscles react more quickly, which means we can get away from any possible danger quicker. This was an evolutionary trait that allowed us to escape the dangers of the natural world better. In today's world, stress is less caused by things like an approaching predator and more caused by things like our jobs. Even though we don't need to jump out of the way of things, every day stress still makes our bodies tense because that's what they were trained to do over centuries of evolution.",
"It might be easier to understand it like this. Tension is a symptom and affect of stress. Much like when we frown when sad or droop our shoulder and posture, Stress has phsyically identifiable characteristics. The reason we hold tension unlike how stop frowning when no longer sad is that we often dont even notice we tensed in the first place or that we are still tense! Eventually the tension becomes a habit that we never learned to undo. This is why so many relaxation techniques involve checking different parts of your body for tension. As you get better at noticing the signs of stress youl get better at undoing the tension to! Also you might be stressed pretty often!",
"Not an actual answer to your question, but if you notice you hold so much tension in your body, you might want to investigate where it comes from. Some triggers can be avoided, but even if they can't it is usually helpful to understand it better. I can't really avoid work stress but just acknowledging that work gives me stress and thats okat helps me to unwind when I am not working. Also: moving is a better way to deal with stress than relaxing! It gives the fight/flight mode in your brain the idea that you already acted on the actual danger, helping to decrease the cortisol.",
"Woah…the bio exam I just took for Uni might actually pay off lol. First, here is some background on stress: Basically, in our bodies we produce hormones. There is a specific hormone called Cortisol which is responsible for LONG-term stress. The more you produce the more stressed you are. This is different from Epienephrine aka Adrenaline, which is your SHORT-term stress hormone, ie “fight or flight” (i noticed a lot of people were mentioning “fight or flight” but I wanted to explain the difference between the 2 hormones, because in your case I don’t think your body is in a “fight or flight” state). When epinephrine enters the bloodstream, it eventually wears off anywhere from minutes to a few hours, hence why it is short-term. Obviously, when stressed (especially long-term stress) your body has to have a way to deal with it, which is where your subconscious jaw clenching and things of that nature may stem from. You can always consult a doctor to get your Cortisol levels checked or any other hormones you’re worried about."
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n3sgln | Breaking the sound barrier | Ok. You know the videos of fighter jets breaking the sound barrier, and there is that big vapor cone that momentarily appears because of the pressure differential. My question is when the "Thrust SSC" broke the world land speed record, on 10-15-97, it achieved a speed of 1,228 km/h (763 mph) becoming the first land vehicle to officially break the sound barrier. There is video of this, but when it punches through, there is no vapor cone. WHY? | Physics | explainlikeimfive | {
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"The vapor cone is made up of water vapor. If the pressure and therefore the temperature of the air drops, you're making a mini cloud due to condensation if the temperature drops below the dew point. So the effect depends on how much moisture there is in the air and the air temperature. I believe the land speed record event was held on a dried out lake bed, so it would have been a very dry environment, and probably relatively warm.",
"The vaper cone is not directly related to the sound barrier. You can get a vaper cone at speeds far bellow the sound barrier, even at landing approach speeds which is the slowest part of a flight. The condensitaion you see is casued by low pressure right behind the main shockwave. All aircraft produce this shockwave and will therefore have a low pressure region behind it. But the strength is dependent on the speed of the aircraft. If you are flying in an area of high humidity and low temperature it does not take much lowered pressure to form the fog. You can often see this on the top of jumbojets and on their wingtips as they come inn for a landing. This is the same effect that causes the vapor cone. When Thrust SSC broke the sound barrier they did so at the Bonnavile salt flats in Utah. This is a very dry and hot area. In order to make the air there condense into fog you would have to dropp down the pressure extremely low. Even a car going faster then the speed of sound was not able to get the pressure that low. Another clue to the conditions is that there is no contrails from the jet engines either. It is of course obsured by the dust but you should still expect a distinct vapor cloud comming out the back. This is because the exhast from the jet engines have much higher humidity then the air comming into the engine which may caus the exhaust to condense if it is cold and humid. However this is not visible on the pictures either."
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n3tcqf | Why do house plants require so much maintenance and still die easily, where as their wild/outdoor family with no maintenance survives for decades? | Earth Science | explainlikeimfive | {
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"A few reasons! Rainwater is generally better than tap water as it contains more nitrates for plant nutrition. You might also get general detritus more commonly outside, contributing to soil health. Human watering habits are also usually inconsistent, and unless perfectly balanced pot plants don't have the combination of water retention and drainage that natural earth does, meaning the plants are usually under or over watered... Light levels inside are also usually inconsistent, not to mention low.",
"Survivor bias, as well as artificial selection. The plants that you see in the forest are a few dozen amongst tens of thousands that germinated. The fact that they survived is not an indication of the hardiness of the average individual in that species. Additionally, many domestic plants are artificially selected for traits that are not adaptive in terms of survival - having prettier foliage or nicer smelling flowers may come at the cost of hardiness and the ability to withstand changing conditions.",
"Plants that grow outdoors have the luxury of a huge root system which gives them a large buffer of water and neutrients. If you do not water an indoor plant for a few days it will use up all the water in its tiny pot and start drying up. Meanwhile if it have not rained for a few weeks there is still a lot of humidity deep in the ground for the plants roots to collect. Similarly if an indoor plant have used up the neutrients in the dirt you provided it you need to add the right amount of fertilizer to make sure it survives. Meanwhile the outdoor plant may be able to collect neutrients from several meters away using long roots. In addition the water flowing through the area will be constantly bringing and taking away neutrients so the plant have a constant fresh supply. Maybe the biggest trick you can do to make indoor plants last longer and make them easier to maintain is to give them large enough pots with lots of nice dirt to grow in."
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n3thnv | why every book seems to be a New York Times Best-Seller | Other | explainlikeimfive | {
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"It is not just one list. Instead the lists are grouped by category and format. And there is new lists every week. This means that there may be a hundred books which gets to the top of at least one of the lists every year. And several hundreds make it onto at least one list. So claiming to be a New Your Times Best Seller may bean that the book was the fourth most sold fiction book in a pocket format during the 42nd week of 2020. But that does not sound as impressive.",
"Because it's one of the easiest awards to manipulate. I know a gentleman that self-published a book, bought 15,000 copies himself, made the New York times bestseller list. There were some rules about how many physical copies had to be printed, but in total it cost him about $13,000 to be a New York times bestselling author and motivational speaker. Now he charges 10,000 per speaking engagement Super easy way to game the system to give yourself validity.",
"> why every book seems to be a New York Times Best-Seller It's simple survivorship bias. Any particular book you've heard of is more likely to be a NYT bestseller simply due to you *having heard about it*. [About 3 Million books get published every year, only 500 end up being NYT bestsellers]( URL_0 ).",
"Because they're the only ones that get the press coverage. I used to wonder this as well, but I think the better question is; why do I only ever hear about New York Times bestsellers, when hundreds of books come out every month.",
"Survivor bias? The only books that *you* see ads for are the ones that are New York Times best sellers",
"it used to mean something, when the best-seller list was just one (or two categories). but a few years back they decided to make separate lists for each category and now just being on any one of the lists is relatively easy to achieve. making \"best-selling cookbook\" or whatever of the week or month is probably rather easy compared to making the \"overall best-seller\" list for all categories.",
"Aside from what everyone has already posted about different lists and formats and timing, the \"best sellers\" are reported to the NYT by the merchants. So, let's say that some big-name brick-and-mortar shop buys too many of a certain title. They need to get interest in this title so they can move the merchandise. So they report that this title sold a bunch of copies, thereby placing it on the list, thereby drawing attention, so they can make their money. So basically, that book is a best seller because someone said it was a best seller. This of course doesn't apply to all books."
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n3ttrd | How did people start using currency? | I know that there are many other posts on this topic but all the replies are about why people made the change and not about how the change actually took place. Say I'm the ruler of a certain area, where people do different jobs and use the barter system. Since the barter system sucks, I want the people to use gold and silver as currency(gold and silver do not have any value yet). All the gold in the area is inside my treasury. Now how do I put the gold and the silver into circulation? One solution I can think of is exchanging the resources that people have for my new currency but that way I, at any given moment will have to keep either resources or currency, but in real life, both currency and resources exist in the market and the government keeps neither. Please give another solution or correct my solution in some way. P.S please point out my grammatical mistakes so that I can improve. | Economics | explainlikeimfive | {
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"In some areas that the British tool over, they wanted people to work in the fields so they offered to pay them 10 crowns a day for work, they also imposed a hut tax of 200 crowns per month, which if it wasn't paid the hut was burnt down. So imposing a tax obligation and then paying in currency is one way it happened.",
"You could look up 'Debt, the first 5000 years' by David Graeber for a complete answer. Basically, societies provided each member for their needs. The need for a medium of exchange arose when societies came across other societies and engaged in trade. 'Currency' is difficult to define without reference to a historical period or specific society (cocoa beans were currency, cows and gold were currency too)."
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n3v2fv | Why do corporations buy companies like AOL or Blockbuster when they're no longer successful and majority of consumers don't use them anymore? | Economics | explainlikeimfive | {
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"They might still have a lot of useful resources. E.g. Skilled employees, patents, customer data, copyrights, trademarks etc.",
"The current AOL is no longer primarily an ISP, but a media company that owns TechCrunch, Engadget, AutoBlog, used to own Huffington Post (sold to Buzzfeed a few months ago). Verizon bought it in hopes of building an online media platform by combining it with Yahoo but has decided to bail on that plan by selling off their AOL and Yahoo holdings.",
"In some cases, they are only interested in patents or copyrights the dying companies sit on. If there's nothing of value to gain, a company will usually not be bought out. I don't think Blockbuster did?",
"AOL and Yahoo no longer hold nearly the prestige or customer reach they used to, but that doesn’t mean they no longer generate revenue via all the holdings that come with them. Verizon’s media arm (which was largely AOL, Yahoo, and Verizon Advertising, which was sold to Apollo along with the other two) still generates nearly *$8 billion* per year in revenue."
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n3vbro | How do wireless chargers work? | Technology | explainlikeimfive | {
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"There are two metal spirals: one in your phone and one in the wireless charger. The one in your wiresless charger spins the electricity around the spiral, which creates a strong magnetic charge because electricity and magnetism are inseparable. Since the spiral in your phone is close enough, it causes a \"sympathetic\" electrical charge in your phones spiral, since the magnetic charge also makes an electrical charge. This is why they're pretty inefficient: they need to hop between a bunch of material and the transfer of electricity this way requires way more power that a traditional charger.",
"Magnetism is a field of electrical charge. When designed properly, a magnetic field can be used to cause electrical charge in another object. This can happen with, for example, spark plug wires for your car's engine. Improperly routed, or damaged, wires can cause an electrical charge in a nearby spark plug wire when the magnetic field collapses (they build and collapse every time the spark plug fires).",
"Well first, know that everything that has a moving electric current produces a magnetic field. That includes the wires in your phone, the neurons in your brain, and bolts of lightning during a storm. But also, a changing magnetic field produces an electric current. So knowing this, it would make sense we could figure out a way to send power from one object to another without connecting them by wire. So first, we take some wire, and we make a coil with it, [like this]( URL_2 ). This is called an inductor. However, since we want these to fit in phones and stuff, we'll make the coils flat, [like this]( URL_3 ). So now, we have our inductors. We'll attach one to the chip that controls the battery re-energizing process, and attach the other to a similar device that will detect when another inductor is in range, and allow power to flow through the coil. Now that we have everything set up, we'll set our phone down on the energizing pad. The system on the energizer and the one in the phone will both activate, and electricity will start flowing through our energizer inductor. As the electricity moves through the wires, a magnetic field curls around the wires in a certain way. Since there are so many turns to the coil, these curls add up, resulting in a big magnetic field [like this]( URL_0 ). The other coil is inside the range of this field, and that causes electricity to begin to flow through it. As long as electricity continues to flow through the first coil, the energy put into it will be transferred through the magnetic field, causing electricity to flow in the second coil, and your phone's batter will be re-energized. If you want to know more in detail about Induction, check out [SciShow on Youtube]( URL_1 )."
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n3vk02 | How does different configuration of neutrons, protons and electrons cause different properties of different atoms | I understand that because of different configurations of sub atomic particles there are different atoms, but I’m extremely curious to find out as to why . | Chemistry | explainlikeimfive | {
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"It's almost entirely down to the electrons, as these form the outer \"shell\" of the atom. When atoms interact chemically, they do so only with these outer shells, by e.g. exchanging electrons or sharing them, and thus making or breaking bonds, or entering into a solution, or what have you. Basically, anything that involves the protons and neutrons in the nucleus is not chemistry but nuclear physics. Nuclear physics deals with things like fission, fusion and radioactivity, but doesn't really have a bearing on the properties of materials as we experience them in our daily lives (unless you encounter a lot of radioactive materials in your life...). Now, the number of electrons that an electron has is tightly linked of course to the number of protons. So in an indirect sense, the protons have an effect on the atom's chemical properties. The protons are also providing the positive charge that keeps the electrons \"in orbit\". But it's the electrons that actually mediate the chemistry. Neutrons are just there as a kind of \"glue\" to keep the protons from repelling each other. Since protons have the same (positive) electric charge, there is a repulsive electromagnetic force between them. However, protons and neutrons also have nuclear forces between them that are attractive. So as long as you have enough neutrons mixed with the protons, these attractive nuclear forces can overcome the repulsive electromagnetic forces, and keep the nucleus together. Chemically neutrons do nothing."
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n3vy6t | Why is the loudest sound ever reported is considered to be the Krakatoa volcanic eruption, at 180 dB and could be directly heard 5,000km away but rocket launches regularly hits 200+ dB but are only heard within the vicinity of the ignition? | Physics | explainlikeimfive | {
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"200+ db doesn't really exist. At 194 db, the sound is so loud that it's creating vacuums between the sound waves. Any louder, and it isn't really a sound wave anymore, just a shock wave. Rocket launches can reach 165 db, but that's still fifteen decibels lower than Krakatoa. As to why Krakatoa was heard so far away, volcanoes are geological activity: the earth itself was producing the sound and helping it travel. Think of it like a phone on vibrate. If it vibrates in your hand, you can only hear it a few feet away. However, if you place the same phone on a table, you can clearly hear it from across the room. In the same way, a rocket engine suspended above the ground will not be heard from as far away as a volcano erupting within the earth. Edit: [Better explanation]( URL_0 )",
"Where did you get the 200dB? Google says they are 150dB when you're near. (And 200dB 100,000 times louder than 150dB)",
"It does not make sense to measure sound like this. That is why you get these strange numbers. The atmosphere is not able to support sounds of over about 180 dB because at that point you start creating complete vacuum. This is why lound noises like rocket launches sounds like they are recorded on a broken microphone, it is not the microphone that is broken but the air itself. So these numbers you are quoting can not possibly be recorded accuratly or even calucated after the fact because they just did not happen like that. So when comparing lound noises like volcano eruptions and rocket launches you have to take into account how large of a volume they can create that sound in. So you calculate a total energy output instead of a dB number. And the bigger the explosion, the more energy in it, the louder the sound will be at a fixed distance where the sound can actually be measured and make sense.",
"All of the top level answers I scrolled through here are missing the mark, even the ones pointing out that your rocket launch number is probably too large. Let's say that you're playing sound from a 1W speaker, that is, 1W of power is being transferred into some amount of air, from which it spreads out as it travels. But now lets imagine that we want to use 2W. There are two ways to do it! We can either vibrate the same amount of air twice as much, _or_ we can vibrate twice as much air the same amount! The power output of a volcano is _vastly_ larger than the power output of a rocket... kinda like a rocket is vastly more power than hopping up a curb. The trick is, the volcano is also much larger (many square kilometers of surface, as opposed to a couple of square meters of engine nozzle surface), so its enormous power is spread out enough (and the logrithmic nature of deciBels is counterintuitive enough) that the number doesn't really capture what's going on. When you take a reading of sound pressure levels, you only take the reading at a single point, and that tells you nothing about what the total output power was.",
"According to Wikipedia: The loudness of the blast heard 160 km (100 mi) from the volcano has been calculated to have been 180 dB. The pressure wave generated by the colossal third explosion radiated out from Krakatoa at 1,086 km/h (675 mph). The eruption is estimated to have reached 310 dB, loud enough to be heard 5,000 kilometers (3,100 mi) away. So that pretty much explains it. The 180 dB figure refers to a measurement 160 km (100 miles) away, but up close at it's peak, it'll have been 310 dB.",
"Decibels are a measure of sound at a specific distance. A so bd measured an inch or two from the source will have a much higher dB than the same thing measured a longer distance away. The pressure and frequency of a sound can cause it to travel farther and lose less volume over a distance. So some sounds can travel really far and some sounds can be very loud but not necessarily travel that far. Krakatoa had a lot of force behind it, so it was able to travel very far. At its source, it would have been much louder than those engines.",
"In addition to intensity there is frequency of noise. The tone or pitch, if you will. Very low pitched sounds travel much farther than high pitched sounds, regardless of decibel level. A rumbling caldera probably had some very low pitched sounds that travelled some extreme distances. I also find it dubious that the volcano was ONLY 180 db. Sound follows the inverse square law, so I’m curious what the sound at the source of eruption would have been.",
"nobody seems to have mentioned that the rocket launch facilities actually have sound reduction systems built in the facilities to reduce the shock waves generated by the launch URL_0",
"Sperm whales can produce 230db, except this sound amplitude can't exist in air, still pretty damp loud, they think they catch their prey by using auditory shock, a gunshot signal",
"Imagine a fire cracker in your hand. You light it. What happens? You burn your hand. Now light that same fire cracker and close your fist. What happens? Your wife will be opening all your ketchup bottles after. The rocket is on the surface. The volcanic eruption is coming from inside the earth.",
"The crack of a whip is pretty loud and fast enough to break the sound barrier but the overall energy is pretty tiny. Compare that to something the size of an exploding mountain and you can get a sense why a loud-as-shit rocket is still comparatively puny.",
"Decibels are logarithmic, meaning every 10 db increase translates into roughly ten times more intensity, and sounds approximately twice as loud to the human ear, which also perceives sound logarithmically.",
"Familiar with Newton's cradle? Those balls on strings hitting each other back and forth? Think of sound as kinetic energy. A molecule moves and hits another one, that then moves and hits another one etc...until one arrives in your ear and transfers that energy to your eardrum. The more distance there is between these molecules, the more energy is lost between each point in the chain. This bleeds away energy and reduce sound as it travels. No molecules, as in space? Sound can't travel. Air on the ground, sound can travel but energy is lost pretty fast due to air being thin and molecules spaced further apart. Under water, much closer together so less energy is lost and it can travel further. Same applies to the rock that the Earth itself largely consists of and that's why earthquakes can be picked up by seismometers far away. They're really just listening devices detecting those vibrations of molecules hitting the next one in the chain.",
"rockets go up to 170db but notnreally more iirc.Remember that décibel are logarithmic, so even a few db difference can be hundres or thousands more \"powerful\"",
"Rocket launch platforms spray huge amounts of water just before and during the blast to absorb the sound, otherwise the shock waves of sound generated would destroy the engines.",
"Why is it that people do not read other posts in a thread before adding their almost identical one?"
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n3w6n0 | Why does sleep deprivation after a certain point make me hyper? | Biology | explainlikeimfive | {
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"Brain gets too tired and goes a lil insane from being up too many consecutive hours. Practice good sleep hygiene by getting 7 hours of sleep at the same time every night. You can make this easier by practicing “bedtime rituals” some that you may already do like teeth brushing, picking out your tomorrow outfit, or reading. Do it at the same time every night and you’ll find it easy to fall asleep at that time with the ritual in about two weeks. Avoiding caffeine after 4 PM is a good idea but not necessarily a hard and fast rule. Also if you’re a teen, teens need 2 additional hours until about age 25 when the brain has fully matured. Brains like repetition, and self care rituals turn repetition into well being. Irregular sleep patterns can wreak havoc on your mental well being and often the first thing a psychiatrist will ask is “how have you been sleeping?” We still don’t fully understand sleep, but the brain can actually be more active during REM sleep than while one is awake. Brains are hella cool, yours is too, so you gotta take care of it by sleeping at regular times :)"
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n3x5sp | Why do specific things (even completely random things) start to appear in your life after you’ve heard of them the first time? | Other | explainlikeimfive | {
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"This is a very common occurrence. Baader-Meinhof Phenomenon (a.k.a. the Recency Bias or Frequency Illusion) The Baader-Meinhof Phenomenon, otherwise known as the frequency illusion or recency bias, is a situation where something you recently learned about suddenly seems to appear everywhere. Essentially, the objects you now see recently became more important to you or you just learned about them and now your brain notices it/them all over",
"Our brain is constantly filtering out irrelevant data. I bet you weren't thinking about your left big toe just now but you are now! See how that works? It's the same when you learn a new word or thing, it'll show up quickly in your day to day life.",
"It's the baader meinhof effect . From wiki Frequency illusion, also known as the Baader–Meinhof phenomenon, is a cognitive bias in which, after noticing something for the first time, there is a tendency to notice it more often, leading someone to believe that it has a high frequency (a form of selection bias).[1][2][3] It occurs when increased awareness of something creates the illusion that it is appearing more often.[4] Put plainly, the frequency illusion is when \"a concept or thing you just found out about suddenly seems to crop up everywhere.\"[5] The name \"Baader–Meinhof phenomenon\" was derived from a particular instance of frequency illusion in which the Baader–Meinhof Group was mentioned.[6] In this instance, it was noticed by a man named Terry Mullen, who in 1994 wrote a letter to a newspaper column in which he mentioned that he had first heard of the Baader–Meinhof Group, and shortly thereafter coincidentally came across the term from another source. After the story was published, various readers submitted letters detailing their own experiences of similar events, and the name \"Baader–Meinhof phenomenon\" was coined as a result.[5]",
"They don't start to appear. You start to notice them. It's a cognitive issue, not an issue with reality. It's known as the **Baader**–**Meinhof phenomenon.** It is basically a combination of two more fundamental biases: a cognitive bias where we pay attention to things that are more relevant or have special significant and disregard the rest, followed by a confirmation bias where we look for things that reinforce a specific belief and disregard things that don't follow that. So you learn about something, it's new and innovative, so now you recognize it when you see it (where before you didn't take notice of it). But since you never took notice of it before, you have no recollection of it ever being there, so you interpret this instead as it suddenly appearing; you don't consider that it was always there, unnoticed. Then you look for more instances this new thing, and you start finding it everywhere, but you don't account for all the times it was there and you just never noticed it. This leads to the false conclusion that this thing was never there, and only started appearing when you learned about it, when the reality is it was always there and you just never noticed it."
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n3xi6l | How does hypnotherapy work? | Biology | explainlikeimfive | {
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"Hypnosis causes a person to be more open to suggestion. Although hypnotherapy isn't total mind control like you might see in the movies, what it can do is put you in a state where you can allow the therapist to suggest ideas and courses of action that you might then implement. For example, if you're having anxiety, the hypnotherapist might induce a trance and then walk you through some mental motions that reduce anxiety, then suggest you try these motions any time you're feeling worked up. In this scenario, the trance does two things for you. First, it helps you pay attention to the therapist and follow along while they teach you the technique, and second, it will help remind you to try the technique when you become anxious. This can also help with behavior replacement. If you have a caffeine habit, the hypnotherapist might help you to mentally play up the bitterness of coffee and also how refreshing water can be. That way, if you get the urge to drink coffee, you will consider having water instead because it would seem more pleasant to you. Of course, once again, it isn't mind control, so if you didn't choose to play along with the hypnotic suggestions, you would just go back to your caffeine habit no problem. Hypnosis relies on a person's willingness to use it. It is a state you have the option to let others induce in you, and using that state, they can give you a push in a mental direction that you want to go in."
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n3y3yi | Why do bike tires need 90-110 PSI, while much heavier cars tires need only around ~35 PSI? | Physics | explainlikeimfive | {
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"Because the contact area is so different between the two vehicles. A bike's contact area with the ground is two tires, maybe an inch wide, over a length of maybe 4-6 inches. A car's contact area is probably about 6 inches square, per tire. So we're comparing a surface area of (1x6)x2 = 12 square inches with (6x6)x4 = 144 square inches. That's 12 times more area on a car's tires than a bike's tires, so the car's tires won't need as much pressure.",
"The important details when considering tyre pressure is weight and contact area. To get a firm tyre, you want to balance the pressure of the tyre against the pressure it exerts on the road. So with a road bike tyre, the weight of the bike and rider will be supported on two contact patches (1 per tyre) of perhaps 1cm wide, and maybe 4cm long - with a rider of 80kg plus a 10kg bike that means 50kg over an area of 4cm² = 12.5 kg/cm² (because I can work more easily in metric) Compare that to a car, where a VW Golf equivalent car may have a tyre width of 20.5cm wide, and 15cm long (though I am having trouble finding an actual number for this, so this is more of an estimate). A Golf weighs up to 1600kg, spread over 4 wheels - so 400kg over an area of 307cm² = 1.3 kg/cm² So this means to equal the weight of the car pushing down on the tyre, the bike will need ten times the pressure in the tyres to balance out. In reality the pressure isn't 10x more in a bike tyre, because there are other factors that influence the pressure you may want - such as balancing grip, efficiency and comfort. I will also admit my numbers may be slightly off as I did have to estimate quite a few, but it does work nicely as an example.",
"90 psi is predominantly road bicycles and mountain bikes can vary from 30 to 50. Of course you can adjust the pressure for the ride quality.",
"My truck has tires at 100psi. It's about weight and contact area. As others have said, PSI = pounds per square inch, and the force accumulates over the surface area. If you have a 12\" by 12\" plate in your hand and I magically exerted a downward pressure on that plate of 1psi, you'd feel a force of 144lbs. If I increased that to 35psi or 100psi you'd feel 5,040 and 14,400lbs of force respectively...on an object that's roughly the size of a sheet of paper. You can see that pressure adds up quickly over a surface area. In the case of a tire, that force is wrapped around the perimeter of the tire to balance itself out and keep it inflated, while the tire compound and belting are under heavy tension load. A bike tire at 100 psi has fewer square inches to develop force. A car tire has far more surface area and the resultant force of 35 psi is quite large. My truck tire is even larger than a car tire and it's at 100psi because my truck is massive and has a large towing capacity. The point here being that whatever portion of your car tire is currently touching the road has a force distributed over it that's equal to the weight on that tire. What you're balancing here is tire deflection. If I have a 100psi truck tire and inflate it to 35psi, it'll still hold my truck just fine, but the tire is a little squished down. If you look at one small \"pizza slice\" of tire from the rim out to the tread, as it rotates around it's one size, and then squished down when it goes over the road, and then stretches back out again. At higher speeds this squishing and stretching happens rapidly. Have you ever stretched a rubber band a bunch or some silly putty and then felt how warm it got? There's friction in the tire compound and it creates heat. Running underinflated tires causes them to heat unnecessarily from all the squishing and stretching, and if they're a little older they might already have small cracks in them and you're far more prone to blowouts. Tire pressures are determined by the strength of the compound, the surface area of the tire, the contact patch area with the ground, and the weight and speed of the intended vehicle. My offroad tires are *very* low pressure because I want as much contact patch area as possible. You're basically running on tires with a few puffs of air more than being flat. And they're great! But if you start driving at 90mph on those while towing a trailer, you'll blow them out. Similarly, if you have high pressure semi trailer tires and you try to offroad with them, your contact patch isn't nearly as good and you'll get stuck."
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n3yh6t | space-time continuum for a dummy, does it physically exist or is it just a mathematical model created to picturise gravity? | Physics | explainlikeimfive | {
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"When we use science to predict what will happen in the future, one of the things we are doing is making a model based on existing evidence. We can then use that model in a predictive way, or to infer other things that are likely to be true. There's something that \"physically exists\" that occupies the function of what the \"space-time continuum\" models. However, our knowledge is imperfect, even the really thoroughly verified stuff. When we have an idea and we want to test if it is useful to determine what is true, we first need the idea to be falsifiable. This means that there must be a test that exists that would, if a certain outcome happened, would prove that idea to be untrue. Then we need to run many such tests and see if the idea is ever proven untrue by one. If the idea is true, it will universally pass perfect tests of its verity. Of course, we rely on imperfect tests. This rabbit hole of near-misses on objectivity goes down forever (it's imperfect turtles, all the way down!). But the more we try and fail to disprove something, the closer to the truth it must be. The idea of the space time continuum has been refined over a long period by a lot of people who want to know if the series of ideas we group under the mantle of \"the space-time continuum\" are true or not. The short answer to your question is therefore that the idea of the space-time continuum fills a role like, \"There's definitely something happening! And we're very sure it works like this.\" But we're always going to have more to learn.",
"The answer to this really depends on your definition of \"physical existence.\" It's a lot less straightforward than you might think, and there's even disagreement in the scientific community. The concept of spacetime is certainly a mathematical construct. It's a framework that allows us to understand space and time in the context of special general relativity. So looking at it that way, it's just an abstraction; a theoretical framework. It isn't a thing that we can see or touch or hold. On the other hand, it has properties that are in accord with and predicted by the mathematical models we made to describe it. Our mathematical models of spacetime predict and describe real, measurable phenomenon that we \\*can\\* see. Does that mean it physically exists? The answer is kind of up to you.",
"We use models to explain things. We might hold up a ping pong ball and say, this is like the earth. We might then put a toothpick through the ping pong ball to show how the earth rotates. We might use a flashlight to represent the sun, and then tilt the toothpick to represent the poles, etc. Sometimes we use a two-dimensional model of a three-dimensional thing. For instance a drawing that shows a farm house in the foreground, a barn in the middle ground, and tiny cows in the background. We can also use a three-dimensional model to represent a four-dimensional thing like showing how a cube can unfold into six connected squares and then show eight cubes in a cross and explain that this is what a hyper-cube looks like when it is unfolded into three-dimensional space. How do these models relate to space time? Well space-time is a four-dimensional construct. it contains within it 3d of space and 1d of time. We can't easily represent 4d items to our 3d brains. We can \"prove\" that space time compresses and expands and works in relation to speed on any arbitrary reference point (General relativity / gravity) but we have a hard time explaining it because we don't have any \"good\" ways of visualizing it. Now \"does it exist or is it just math?\" is a really big question. Every PHYSICAL TEST we have come up with and every MATHEMATICAL TEST we have come up with say that our MODEL of relativity MATCHES what we can test for in REALITY. BUT is it \"REAL\" ??? Science can never say for certain that something is REAL. We can only come up with better and better models. For instance we used to accept that Newton's idea of Gravity was \"REAL\" because we had no tests that we could conduct that said it wasn't. Then we found some tests that showed newton's Model for how gravity work failed to take into account things moving near the speed of light. His model broke down there, but Einstein's model doesn't break down. In fact Einstein found the math first, and then we developed the physical tests much later. Is the current \"Theory\" or accepted law, about gravity 100% correct. No. It breaks down at the quantum level. So maybe there is a better model out there that will more more closely fit all aspects of reality. But is the model of gravity we have right now including space-time accepted as \"REAL\" for anything larger than the quantum scale? Yes."
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n3ywj6 | why can people eat hot foods (temperature wise) and not burn themselves but if they drop the same food on their skin get burned? | Biology | explainlikeimfive | {
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"Water has a high thermal capacity and the ability absorb heat. On a much larger scale, think about how water is used to put out fires. Since your mouth is wet, the moisture absorbs some of the heat from the food. This is why our mouths can tolerate hotter food/beverages than our fingers, for example.",
"If anyone says that you can't burn your mouth eating hot food, clearly they have never eaten fresh pizza."
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n410ck | in movies and tv you often see people having panic attacks hyper ventilating into a paper bag. Why do some hyper ventilate and is this an accurate portrayal of panic attacks? | Other | explainlikeimfive | {
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"The breathing in a paper bag is a method to counter the high oxygen concentration in your blood when hyperventilating. By breathing in a bag, the air you breath in is more rich in carbon dioxide and contains less oxygen, causing the levels in your body to return to normal. So it is an accurate portrayal of a common thing to do when having a panic attack, since it often goes paired with hyperventilation.",
"The paper bag thing isn't really a symptom of hey panic attack, but rather a folk medicine treatment for hyperventilating, and hyperventilating can often be a side effect of a panic attack. So for people with that side effect, it may help."
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n412lt | if the covid vaccine tells our cells to make specific proteins to counter the virus, what functionality would have our cells been doing prior to receive the vaccine? Can our cells do both its regular functions and the additional covid mrna? | Biology | explainlikeimfive | {
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"Cells make many proteins as part of their life cycle. If a cell needs basically anything to happen/be done, from metabolic conversion steps to structural support elements and compounds that can be excreted to damage invaders, there's individual proteins for all of it and cells are constantly making loads of them. Any given cell will be constructing hundreds to thousands of different proteins at any given time; the mRNA instructions from the vaccine add just one more to that workload. The difference this makes to the cell's capability to keep making whatever else it needs will be minimal at most, probably not even measurable. Note also that the protein encoded in the vaccine mRNA does not actually counter the virus by itself. It actually encodes a small part of the virus (completely harmless on its own), which your cells will produce and excrete. Patrolling cells of the immune system will then encounter the virus part, and prepare defenses that can be directed at anything that has that little virus part on it -- namely, the actual virus itself if you ever get exposed."
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n41us3 | Why does Adobe need to update their products so much? | Technology | explainlikeimfive | {
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"By adding features, optimizing performance and such, you potentially introduce new bugs into a program as a developer. A fixed bug can even cause new bugs to appear. It's a vicious cycle that never truly ends. Especially in very complex software like the Adobe Suite."
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n41ywk | Where are songs stored in the brain and why do they lay dormant for many years? | How can a song be in your brain just dormant then one morning 20 years later you find yourself singing it? | Biology | explainlikeimfive | {
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"Memories of songs are stored in the temporal lobe, with nerve connections to other parts of the brain involving your senses. If you randomly remember a song, something must have triggered that memory, possibly a sense that connects with a memory in your temporal lobe. (this is a very oversimplified explanation but I guess that's the point lol)"
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n42va8 | Why do both fusion and fission produce so much energy, when they are opposite reactions? Where does all the energy come from? | Physics | explainlikeimfive | {
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"In the case of fission, the energy was stored in the \"big and heavy\" atoms (uranium, plutonium, thorium) when an ancient star went supernova and created them by squeezing/compressing/packing other, lighter, elements together to form the fissile elements -- elements that now want to split apart and release that old supernova energy they have stored. On the other hand, fusion releases energy because the total mass of the resulting single atom is less than the mass of the two original atoms being smashed together. The leftover mass is released as energy. Fusion only releases energy for atoms in the periodic table of elements up to iron, though. Above iron, smashing atoms together *consumes* more energy than it creates. So, to get elements \"heavier\" (atomic mass on the periodic table of elements) than iron (such as uranium, plutonium, and thorium) you need a supernova with a *lot* of \"extra\" energy flying around to get them to fuse.",
"Because there is a value called \"binding energy/nucleon\" and that basically dictates that everything lighter than iron can fuse to release energy, and everything heavier than iron can fission to release energy. So you can get fission reactions from heavy elements like uranium and plutonium, and you can get fusion reactions from hydrogen and helium.",
"The simple answer is that any atoms lighter than iron on the periodic table can undergo fusion to produce energy, and anything heavier can undergo fission. Iron will do neither, it's the \"end product\" of both. This is because iron is the most \"efficient\" way to pack the nucleus of an atom. The energy comes from the mass of the particles involved. A proton and neutron measured separately are more massive than when bonded together. This difference in mass is released as energy.",
"The binding energy per particle in the nucleus depends on how many there are. Iron has the maximum binding energy and it is lower for atoms before and after it in the periodic table. So you can split apart heavy atom or combine light atomic and get energy out Its curves are not exactly smooth is lithium-6 can be used to create the lighter helium-4 and you get energy out. The curve [looks like this]( URL_0 ) Binding energy is the energy that is required to remove a particle from the nucleus. An analog is magnets. Magnets attract each other and you could extract the energy from one magnet moving towards another. If you just release them and hit each the kinetic energy will become heat. To separate them require energy, that is like the binding energy. So combining hydrogen to create helium is in a way like two magnets you put together. The produce of both require energy to split apart and the same amount of energy is released when you combine them,"
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n437l0 | Is the old narrative that girls mature faster than boys (mentally/emotionally) actually true? If so, what is the reason behind this? | Biology | explainlikeimfive | {
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"While definitely influenced by multiple things, girls hit puberty earlier than boys, and puberty cranks up the engine on every part of development, including mental/emotional maturity. This is why it’s not uncommon to see 5th grade girls who are taller than their boy classmates. Because of this delay, the boys in their grade always seem to be behind. They all catch up eventually, but it takes years. It gets more complicated, though, because “mature behavior” is a society thing (like controlling your impulses), but “mature development” is not. Testosterone tends to push boys into thrill-seekers with poor impulse control, and until that balances out later in life they’ll tend to act more immature by society’s standards, even if where they’re at is normal for their age. Huge caveat here that we’re talking population-level, and what’s true for some won’t necessarily be true for all. Broad ELI5 generalizations."
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n43in2 | that when a man pees on a pregnancy test and it comes back positive, it’s indicative of cancer? | Biology | explainlikeimfive | {
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"Sometimes, possibly. hCG isn't something typically found in the urine of males, although some tumors do produce it.",
"ELI5: yeah. If a woman pees on a pregnancy test and it’s positive, it’s because her pregnant self is making a hormone called hCG which helps the pregnancy along and the extra spills out of the kidneys and into the urine. If a man pees on a pregnancy test and it’s positive, it’s because he has a lot of hCG, too. But men shouldn’t have that, which means something is wrong. There’s different kinds of cancer, and while a lot of them just grow and grow out of control like weeds, some of them make a bunch of extra hormones and stuff because it’s a bunch of cells that have gone crazy. That’s why we think the man has cancer, and a specific hCG-making kind of cancer at that. But here’s the thing: it’s just that one kind that makes hCG, and just because a guy has a negative pregnancy test doesn’t mean he DOESN’T have cancer, just that he probably doesn’t have THAT cancer. Wash yourself daily and keep tabs on your body. If you feel lumps/bumps/pain/swelling around your boys, go to a doctor."
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n4468j | Why do the muscles that operate our heart and lungs not need to be stretched or get sore as opposed to something like our leg muscles that get sore easily and need to be stretched to avoid injury? | Biology | explainlikeimfive | {
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"Muscles don't actually stretch. The idea that stretching prevents injury by lengthening the muscle is a myth. In fact, there is some evidence that stretching before physical activity increases the chance of injury because stretching causes micro tears in the muscle. If your muscles actually stretched it would be bad. The length of your bones doesn't change so you'd have loose muscles that can't pull on the bones.",
"You don’t have to stretch your diaphragm before running because you regularly stretch it, and keep it warm, throughout the day with regular day to day activity. Additionally, its job is to pull the bottom of the lungs down, which lets you breathe in, which even during exercise isn’t all that hard. If it needs help, you’ve got all kinds of rib, neck, and even shoulder muscles to help. And if you push it hard enough? It’ll get sore just like any other muscle; ask anyone with COPD or asthma and they can tell you about that midsection discomfort when they’re having an attack. As for the heart - the difference here is *why* the muscles get sore. They generally get sore because of an acid they produce when you’re really working hard called lactic acid. That stuff builds up when your muscle’s mitochondria (*the powerhouse of the cell*) are firing on all cylinders but it’s not enough and you start making power in faster, dirtier, less-efficient ways. Heart cells though? Mitochondria for dayyyys. They’re good. They’re a V12 engine. So you can get heart pain for other reasons, like it’s not getting enough oxygen, but lactic acid buildup isn’t going to be an issue."
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n45tdk | Why do horses owned by people need their hooves trimmed, and why didn't horses need their hooves trimmed before humans tamed them? | Biology | explainlikeimfive | {
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"Horses owned by humans lead an easy life. Their wild brothers are constantly roaming on rocky ground, looking for a sprig of grass, and galloping over those rocks to get away from predators, or just for the joy of running. The constant activity of a wild horse wears down their hooves. Human-owned horses stand around all day, and when they do trot around a bit, they do it on manicured soft dirt that doesn't wear their hooves.",
"Former farrier here. Oh, and for those that don't know a farrier is basically a specialized blacksmith who who makes and puts on horseshoes. Although in this day and age not many people custom make shoes unless they are especially needed, they're usually just keg shoes you buy in bulk that you can shape as needed. As others have said it has to do with the wear of the hoof. Some domestic horses don't need their hooves trimmed at all because they roam around fairly large areas and they wear down naturally, but typically they do need to get trimmed after a while. Softer the ground the more they'll need it. But they're living on sandy or rocky ground it wears down the hoof a lot more. If you don't trim they'll start to crack and break and that can lead to fissures and other nasty problems. Edits to correct stupid speech to text errors.",
"Wild horses don't need their hooves trimmed because of the amount of running they do every day over a lot of different surfaces. (Dirt, rocks, etc.) But the horses people own have to have it done because they are just in their own little area, usually on soft ground that doesn't wear their hooves down.",
"Horses in captivity spend a lot less time walking. They often live in stalls or small flat pastures. Wild horses walk up to 20 miles a day and walk over all kinds of terrain which keeps their hooves worn down",
"Just going to add a bit more to the correct answers already posted regarding shoeing. (Barefoot farrier reporting). Diet has a role too. Domesticated horses are fed diets much higher in sugar (i.e. grains) which can actually effect the structural integrity of the hoof and cause severe issues that require shoes for the horse to remain comfortable. Worst case scenario the pedal bone (bone inside hoof) rotating down through the sole of the hoof. We call this laminitis or founder. Another fun syndrome of the hoof often requiring shoes is navicular disease which has a few reasons for coming about. In my experience it has been the conformation of the horse (selective breeding- looking at you halter bred quarter horses) that causes the degradation of the navicular bone and blood supply. (There are many other reasons for a horse to get navicular disease- this is just based off my experience). So in summary- we domesticated horses and changed their natural diet, exercise regime and physical build and thus they now often need specialised farriery and shoes to be comfortable doing to work we ask of them."
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n46gci | Why does listening to loud music I don't enjoy give me a headache but music I do enjoy doesn't? | Other | explainlikeimfive | {
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"Cause music you don’t enjoy is noise to you. Loud noises give you a headache. Music you enjoy is well… music you enjoy",
"Good question. Perhaps it’s the slight distress and feeling of dissatisfaction your brain is experiencing, and it’s response is to cause a headache to encourage itself to remove itself from that environment. It’s funny how our brain needs to convince itself to take certain action - or at least the idea of it is funny."
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n46mo5 | When we ‘lose’ our voice, like during a cold, what actually happens to our vocal cords? | Biology | explainlikeimfive | {
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"Generally when you lose your voice the reason is your vocal chords are inflammed. Inflammation = swelling. When the vocal chords are swollen they become a different shape & that alters the sound that they make (or don't make if it's bad enough) when you try to talk because the way they move the air is different.",
"Your vocal cords are part of the area your throat that’s infected with the cold bug, and they become inflamed. Know how when you get an ingrown hair somewhere and it becomes swollen, red, and painful? It’s like that. So because your vocal cords and the stuff around them swells (just a tiny bit), your voice changes. Even tiny changes to the size/shape of your cords can change it dramatically. They may even become unable to make a voice at all! That inflammation is also why it hurts to talk/swallow and why the back of your throat turns red (and why we make you stick your tongue out and say “ahhhh” - to get a good look back there)."
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n47n2o | what is the difference between drug-induced psychosis and any other non-psychotic experience that drugs can give you? If certain drugs make you see things that aren’t there, isn’t that technically psychosis? | Other | explainlikeimfive | {
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"Drug induced psychosis lasts longer than the time the drugs are in your system. Seeing stuff while on drugs isn't psychosis, its being on drugs. Psychosis is having visual and/or audible hallucinations that aren't triggered by outside chemicals.",
"Psychosis is characterized by losing touch with reality. I hallucinate sometimes and have since I was a kid, but I know what I’m hearing isn’t real and it doesn’t bother me. I can easily separate it from reality so it’s not a psychosis. I started a new drug a few months ago (anti-epileptic, not related to any mental issues) that gave me some auditory hallucinations. They were drug induced, but I knew it wasn’t real so it was not psychosis. Now when I accidentally took 5mg of a THC gummy instead of 2.5 and thought my coworker bill was breathing down my neck at work when every time I turned around he wasn’t even in the room, that could be considered drug induced psychosis. My perception of reality was altered and I couldn’t easily tell which stimuli was ‘real’."
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n47w61 | Did we discover Math, or invent Math? | We use math to describe the universe, but is it something natural that is inherent in the universe that we discovered, like gravity, or is it something man-made that we use to describe the universe, like language? | Mathematics | explainlikeimfive | {
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"This (formalism vs platonism) is a deep philosophical question about the nature of math, and there is no consensus one way or another.",
"Both, but starting with Inventing, as needed, to describe circumstances, starting with basic counting. And then some of it was discovered as things got more complicated, like the relations between certain numbers and certain objects or concepts, like Pi and circles!",
"The properties that we use math to describe were there regardless of whether we knew about them or not. Think about it like language, words. We can describe other planets, or laws of physics, or the color of something, and someone who speaks another language would use different words to explain the same thing. Regardless of /how/ they're described, you haven't changed anything about the fact that they were already there before any of us had the words for it."
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n481xu | Why can't we drink water from a river or wherever but basically any other animal can? | Biology | explainlikeimfive | {
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"Their gut biomes are used to drinking out of the river. Also depends on where you are drinking from there are certain bodies I’m sure you can drink out of without getting dysentery.",
"For the same reason a native of some random small town in Mexico can drink the tap water without issue but if you do you'll get to enjoy traveler's diarrhea. They are accustomed to the stuff in the water and their digestive and immune systems can handle it, whereas you are accustomed to clean, sanitized water and your system cannot handle dirty water. And yeah, you could get used to it eventually, provided you didn't catch something serious enough to kill you. But it would be a long, unpleasant acclimation process and the risk of dying from it would be non-zero."
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n485hg | Why does room temperature water taste warm while room temperature food tastes cold | Other | explainlikeimfive | {
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"It's a matter of expectations. You're feeling the same temperature in both cases, but you're comparing it to something different. It's like the way a chocolate bar that costs $10 is expensive, and a computer game that costs $10 is cheap."
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n48koq | How does the body know to get rid of a toxin? | Is it an immune response, or just a built-in control in the digestive system? I assume it's easily genes with instructions to literally flush it out as fast as possible, but I get the feeling there's more to it. | Biology | explainlikeimfive | {
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"\"Toxin\" is a reeeeally broad term. There are generally only two ways toxins can leave your body - through your GI tract (vomiting/pooping) or kidneys (peeing). So as for vomiting, if you eat something toxic, like spoiled food or a poison, it'll either immediately begin attacking the stomach to get into the body or small chemicals will absorb their way into the blood (either in the stomach or a little while later in the early small intestine). Either of these causes the brain to trigger the \"nausea\" mode, which is what leads to vomiting - a complex process which reverses the direction of *everything* in the GI tract up until where the small intestine ends, so even if a toxin has made it past the stomach, you can still vomit it out. But some toxin has made its way into the bloodstream. Thankfully, you have a *built in filter*. See the blood from your entire GI tract doesn't simply empty into general circulation, but rather all of it goes to the liver. The liver is an incredibly complex organ, but the gist of it is that there are rows upon rows upon rows of cells where the blood passes by and is sort of \"filtered\". The liver specializes in taking in chemicals that it either recognizes as normal body-waste or chemicals which don't belong to the body. Think of it like being a bouncer at a club booting out people who aren't on the guest list. There are a large number of special enzyme proteins which we've evolved to neutralize these. In neutralizing them, one of two things happens: the harmless/less harmful and now-definitely-able-to-dissolve-in-water chemical is released back into the blood stream or it's diverted into the system which makes bile. Bile is excreted into the small intestine where it's eventually pooped out, along with the toxin. One of several things bile does! If it's released into the blood stream, it's filtered out through the kidneys and urinated out. If it's a toxin that the immune system is equipped to deal with, those cells will use their chemical defenses, either neutralizing it there or taking it in themselves to the liver to be destroyed. If they can't, they'll wall it off from the body to the best of their ability by surrounding it with cells which adhere together forming a ball separating it from the body, eventually becoming scar tissue.",
"There is no single thing known as a “toxin”. There are a huge number of specific chemicals the body encounters/produces that can be toxic and the body knows how to manage/dispose of most of them. It either directly excretes them, or binds them to chemicals that can be excreted. Typical they are neutralized in the liver, and/or filtered out by the kidney. The idea your body needs special help riding itself of toxins in a marketing scam to sell you fake heath products. Eat a deathly diet, drink plenty of fluids, and if you are at all healthy, your body will do the right thing. Of course this is not carte blanc to consume and expose yourself to literally anything, but our bodies are remarkably good at keeping themselves in good working order if you give it half a chance. \\*Edited\\* to note there are a small number of toxins dealt with by the immune system with antibodies, but most are handled by the liver/kidneys. \\*Edited 2\\* to note some times the body will detect toxins in the digestive system and flush it all out from whichever end is closer. This results in a panicked trip to the toilet. Vomiting is done with muscle contractions, diarrhea is by adding water to the digestive system and putting the muscles into overdrive."
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n48s5t | why is ceramic useful as body armor when ceramic mugs shatter really easily? | As title suggests, just seems bizarre that a material that in everyday life seems quite fragile can stop a bullet... | Physics | explainlikeimfive | {
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"1) Material. The ceramic they use in mugs are often made of clay material, terracotta, porcelain, that kind of things. While ceramic armor are made of material like silicon carbide and such. Even if both are ceramic, they don't have the same proprieties. It's like comparing bronze to steel, both are metal, but that don't act the same way. 2) Size. Pottery are often thin, while ceramic armor can weight up to 8 pounds and their thickness is measured in inches. The more material you have the more it can survive stress. The same reason why a bullet will go straight through your windows at home, but will be stopped by an inch of glass. 3) You are right that ceramic seem fragile, but that doesn't really matter. When a bullet hit the ceramic it will shatter it into small pieces, but that's the point. All the force of the bullet will go through all those fractures and dissipate the force. The ceramic will be useless after that, but the job is done. Now well done ceramic plate is made like a sandwich with different material so that the ceramic plate don't get destroyed in one shot. They try to achieve a balance with different layer, so the ceramic shatter to dissipate the impact, but the shattering is limited by the other layer to a small area, so that the plate can survive more than one impact.",
"It shattering absorbs the energy , it it didnt then most of the energy would be transmitted to the thing behind the plate",
"Ceramic alone isn't enough. The way it works is a ceramic plate works in tandem with kevlar to stop the incoming round. First, the bullet hits the ceramic plate. Because the plate is so much harder than the bullet, the bullet immediately begins to deform and and rip apart under the stresses as it tumbles. Second, after the bullet has tumbled and torn apart and lost a lot of it's speed because of the plate, the kevlar layers behind the plate catch and slow down the fragments. The idea is the bullet at this point is moving much more slowly than it was before, and it's in smaller chunks. These slower chunks are easier for the kevlar to slow down. At this point the tensile strength of the kevlar brings the fragments to a complete stop by spreading the impact energy over a large area. It still hurts and feels like you've been hit with a baseball bat, but the combination of the two materials saves your life. Neither the kevlar nor the ceramic would be able to do it alone, but together they can compensate for each other's weaknesses."
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n49fjw | Why does the funnel of tornadoes shrink as it goes downward? | I'm not very smart, know this if you find the question too dumb. Thankyou. | Earth Science | explainlikeimfive | {
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"No, it's a perfectly valid question. Some funnels don't appreciably shrink downward: the EF4 that hit Greensburg KS was roughly evenly cylindrical all the way down. It has to do without how the air column is able to move the air and debris around it. As the funnel descends, it takes more and more energy to maintain it the farther from the cloud it extends, thus there is less kinetic energy - less air movement - at the bottom than the top."
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n49oir | If people need fire to be able to eat meat, how did cavemen consume food before discovering fire? Were cavemen vegetarians before the discovery of fire? | Other | explainlikeimfive | {
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"It's not that we need fire to be able to eat meat, but that cooking meat makes it safer for us. It makes us less likely to die or get sick from eating meat. Before cavemen discovered fire, they just had to take that risk.",
"You can eat meat raw. People do it all the time in the modern world. Cooking helps remove bacteria and makes it safer to eat the food, and many people prefer the taste. But raw meat is edible, and many of the issues you may face with eating FRESH raw meat are discomfort, not death."
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n49tch | Why is dental health so strongly dependent on brushing our teeth and flossing when our ancestors hundreds of years ago did not do the same? Did they have some separate mode of dental upkeep or were they just constantly losing teeth/have just awful mouth conditions? | Biology | explainlikeimfive | {
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"It depends on what time period you’re talking about. Hunter gatherers prior to the advent of agriculture tended to have very healthy teeth. This was the result of two primary factors: far less carbohydrates in their diet and a lot of grit i.e. sand, silt, etc. in the food. Their teeth tend to be heavily worn down, but otherwise healthy. In early agricultural societies dental health tends to be way worse as a result of lots more carbs/sugars in the diet, softer foods, and obviously no fluoride toothpaste. Now all that said, if you were in any preindustrial society and you developed a dental problem, it could become extremely serious and without doubt people were aware of this. Abscesses can form and basically rot out chunks of your jaw or even kill you. Based on observations of living and recent preindustrial societies, both agriculturalists and hunter gatherers likely used things like thorns and chewing sticks to clean their teeth regularly. Source: I’m an archaeologist",
"Mostly, it's that our ancestors didn't have access to anywhere near as much sugar as we have today. So because of that, most of our ancestors had less cavities than we do. But also, chronic dental pain was something we see lots of reports of in old texts and diaries. A lot of our ancestors who had dental problems, just had to suffer for the rest of their lives, or have painful procedures done by people without much knowledge of what they were doing.",
"The invention of stone milling of grain caused tremendous tooth wear because of tiny particles of stone in the flour. Societies with any kind of sewing/leather work had people with extra tooth wear from using teeth as a tool to help their work. On the positive side, diets low in sugar helped prevent basic decay. On the negative side, if your teeth failed in your 30s, then the rest of your life would be much less happy, and probably much shorter.",
"The latter. They were constantly losing teeth, and dying earlier (in some cases due to poor tooth hygiene). If your average life expectancy is \\~35 you're not nearly as worried about tooth longevity as if you live to \\~70. They also had diets that weren't as hard on their teeth as ours are (refined sugar is a relatively recent invention), but the biggest part is that their teeth were worse. Much much worse.",
"Evolution is only impacted by issues that affect your chances to procreate. By the time their dental health became a problem they already had plenty of offspring. Source: None really, so I might be totally wrong.",
"Both of your hypotheticals are true. Some societies had effective ways of cleaning their teeth, there's one thing they did in India and Arabic regions was find a specific twig from a certain species of plant called miswak they scraped food and plaque out. It broke in a convenient manner and had a tolerable taste, possibly some medicinal antiseptic properties too. Miswak are still used in modern times in those regions. Ancient peoples had very basic ideas of dental health, it was mainly a comfort thing, they didn't really make the connections to diet leading to cavites, so when food became more sweet and acidic you'd start seeing cavities. Dental issues are thought to have been issues related to diet or unmanaged tooth breakage. There a derth of archaeological evidence that if a tooth got bad enough to abcess it got pretty bad as ancient dentistry was not great. They probably lost teeth at a slightly higher rate than modern humans."
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n4amrg | How do we record sound and what separates a good microphone from a bad one. What makes a good microphone good? What parts actually decide this. | Technology | explainlikeimfive | {
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"Sound is a pressure wave moving through the air. A microphone converts that pressure wave into an electrical signal. It's essentially the reverse of a speaker. In a microphone there is a diaphragm attached to a metal coil, and the coil is set inside a magnetic field. The diaphragm vibrates according to the pressure of the sound wave, that vibration causes the coil to move, and the movement of the coil inside the magnetic field produces electricity. The 'size' and 'speed' of the electrical signal produced corresponds to the original sound wave. There are different types of microphones but that's the general idea for what's called a dynamic microphone. A condensor microphone is a refinement of the same idea but instead of a diaphragm moving a coil, the diaphragm itself is conductive and it's movement is converted into electricity via capacitance. What separates good from bad depends on what you need to do. In general you want a microphone that can accurately capture the frequency range of the sound at a sufficient volume level from a suitable direction and at a suitable distance. Some microphones pick up sound from a narrow angle, and others from a wide one. That's a whole other topic called cardiod patterns (because a graph of the microphones 'best working area' looks a bit like a heart). Some microphones need to withstand a lot of volume before they distort the recording and others need to be much more sensitive at low volume levels. That's one big difference between dynamic and condensor microphones. So then the parts that decide what's good depends on the particular application. But in general it's the sensitivity of the diaphragm (how well it moves according to the different sound frequencies) and the geometry of the diaphragm (what range of angles it can keep that sensitivity at an acceptable level). There's really no one answer. What if you want a microphone that works well from a distance and a wide area? Well then you're going to pick up all sort of sounds that you don't want. What if you want a microphone that works best when it's close to the sound source? Well you better hope the sound source doesn't move or hugely increases it's volume. Hopefully that's a useful answer."
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n4atlx | ; What was 'vertical hold' all about? | The image on the TV of my childhood would sometimes start to scroll up or down. You had to adjust a tiny knob to stabilise the image. Why. It no longer exists as a problem or solution. What changed? | Technology | explainlikeimfive | {
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"CRT TVs worked by shooting a beam of electrons at the screen to light up pixels, that beam would go from left to right, then drop down a row, left to right, drop down a row, and so on until it got to the bottom of the screen when it would pop back up The signal coming in was timed so that it provided each row in the time it would take the beam to cover the row and provided a moment of blackness at the end of the frame to let the beam get back up without mucking up the image During this blanking pulse there was a Vertical Sync pulse to let your TV know it was time to start a new frame, its hardware would try to pick this up and sync on it, but if the TV's internal reference gets too far off then it won't be able to sync on this signal so you have to fiddle with Vertical Hold until the Vertical Sync signal was back in the window the TV could lock onto.",
"Old TVs were made with analog components that weren't very accurate, and would change with time and temperature. Some of these components were used to create timers to decode the TV signal. If these timers drifted too far off what they should be, the TV wouldn't display the picture correctly anymore. So the user would have to adjust the circuit until the timing was close enough to being correct again. Once TVs moved to digital circuits internally, the timing could be super accurate, and no longer needed to be adjusted by the user. Now, analog signals aren't even broadcast anymore, so it's a completely obsolete issue.",
"They had a cathode ray tube (CRT) that fired electrons at a phosphorent screen in a specific sequence to create an image. The vertical and horizontal holds were minor calibrations to help sink that up. CRT's are not longer used in TV's.",
"Old tube tvs made a picture by shooting a beam of electrons onto the back of the screen. The beam was aimed by using electromagnets. This would steer the beam to scan from top to bottom and left to right very fast creating a picture. If the timing was off then the picture would begin to scroll. Later tube tvs could adjust themselves so vertical scrolling was less of a problem. Now it is no longer needed because we use lcd and led screens that refresh all the picture all at once in most cases.",
"With analog TV, you get a stream of information that your TV converts into a beam of electrons that it scans back and forth across the back-side screen of your television. It goes from one end to the other, horizontally, then moves down slightly, and repeats, until it reaches the bottom of the screen. The timing of this sweeping beam of electrons has to match the timing of the analog TV signal it is receiving it it will not draw the picture correctly. But these old TVs also did not have very precise controls, so provided the ability for users to manually adjust them. 'Vertical Hold' was one of these controls. Eventually analogy TVs became advanced enough that it could automatically make sure the timing of the electron stream matched that of the analogy signal, eliminating the need for horizontal or vertical hold. Digital signals eliminates the problem altogether, as it provides explicit pixel-by-pixel information about how to draw the image.",
"Analog TV depended on a vertical sync signal to mark the top of each video frame. Because the signal could suffer from interference, each TV also contained a pair of oscillator circuits (“phase-locked loops”) that “guessed” the timing of the next vertical and horizontal sync, to provide stability of the picture if that sync pulse was missed. If the “guess” is close enough to an actual sync pulse, the TV uses the sync pulse. Otherwise it substituted its own oscillator for the frame timing. The vertical (and horizontal) hold knobs provided fine adjustment of the oscillator timing, allowing you to match the oscillator’s frequency and phase to any actual TV signal. Without sync, frames could start drawing in the wrong place on the screen- you’d get a black bar between the bottom of one frame and the top of the next. Adjusting V-hold involved four steps- try both directions to see which direction slowed the “rolling”, then turn it so it stopped completely (matching the frequency of the sync pulses), then nudge it in one direction or the other until the top of the frame was at the top of the screen. The TV would “lock” back into the real sync pulse and you’d be all set. A last optional step was to “center” that adjustment a bit so it wasn’t right on the edge and wouldn’t lose sync as easily the next time an airplane flew overhead. Digital electronics meant a TV could do all this on its own without a knob.",
"Originally, as others explained, the picture was drawn on the screen line by line and the tv needed to know when to start over at the top left corner. It also had to know when to start each new scan line. So, there were two kinds of pulses that kept the tv drawing the picture on its screen the way the tv transmitter intended-one pulse to start a complete new screen, and a different, smaller pulse to start a new scan line. The vertical sync electronics detected when the tv signal had the little blip that indicated to start a new picture at the top left. The vertical hold adjustment changed how sensitive the vertical sync circuit was. It had to be in a certain range because otherwise it would see the new-scanline pulse a a new-screen pulse or else would randomly trigger on various parts of the signal. The vertical sync electronics would sometimes slightly change adjustment with temperature, age, etc and get to where the vertical hold stopped working right. The vertical hold adjustment was so the people watching the tv could fix it without having to call a repair tech. And yes, this is oversimplified and disregards a lot of stuff but this *is* ELI5 :-) Edit: I didn't answer why this became a non-issue First, electronics got better and the TV itself could auto-adjust the vertical sync. This was very common on TVs made in the last 10 or more years of analog television Second, newer ways of sending the picture weren't based on the line by line drawing of a screen but more of a 'send each new frame as a .gif and display it on the screen' approach"
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n4b36d | Overprescribing antibiotics has the potential to create superbugs by only killing most of an infection, leaving more resilient germs to reproduce. How come we don't have a similar problem when it comes to other methods of killing bacteria such as boiling contaminated water? | Biology | explainlikeimfive | {
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"Boiling kills the bacteria by denaturing the proteins that make it up. The key difference is that there isn’t going to be any significant difference in the range of temperatures the bacteria proteins can withstand. Imagine antibiotic resistance being like feeding progressively hotter peppers to a group of different people. Some will be able to withstand peppers more than others, and if they have children will probably inherit that resistance. Now imagine boiling water like taking that group of people and shooting them with a shotgun. Some of them might survive, but it probably has nothing at all to do with a natural resistance to shotguns (probably impossible anyway), and whatever fluke allowed them to survive probably won’t be heritable. Their children will be just as vulnerable to shotguns in the future.",
"Bacteria reproduce so quickly that a single bacteria that's resistent to a given chemical can recover very quickly from a cleaning. Alcohol and boiling water are different because the evoltions necessary to deal with those are impossible for bacteria. Larger creatures can consume alcohol beacuase we have livers capable of detoxing our blood, which a single celled lifeform could never do. Heat denatures the proteins that make up cells, and with the exception of extemophilic microbes, boiling any creature for long enough will kill it. Being able to withstand high temperatures is not as simple of an adaptation as being resistant to an antibiotic, so only much more complex microbes can do it."
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n4b4uf | How are news broadcasting companies alerted so quickly about serious crimes and other newsworthy material? | Other | explainlikeimfive | {
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"There’s an organization called the Associated Press (AP) that collects stories from news-gathering organizations worldwide and publishes them on what’s known as a “wire” service, which is an electronic real-time news feed. This was happening as early as 1914, when it used telegraph wires (hence the term “wire service”). News media companies subscribe to the AP wire service, which alerts them in real time when stories are published.",
"We have scanners, radios, multiple sources and all manner of methods of knowing what’s happening. The authorities most definitely do not have a duty to tell us. Most of us work hard to develop our sources, and there are regular citizens that will call in to inform if something is happening. To the extent that “caller advises” is a joke in most newsrooms because “caller” is very often very wrong. Also, if it’s newsworthy it may not be as “breaking” as you think it is. We often know hours or days in advance that something is going to happen; the media for the most part honors blackouts at the government’s request. If a high profile official is somewhere dangerous we aren’t going to report it. I’ve known of officials in a certain place while it was being reported they were on the other side of the world. A blackout was in place until the official could get to safety. This isn’t common, and might be during a hostage negotiation or war when it wouldn’t do for the enemy to know where someone actually was during a negotiation. In the case of well known people, we have some information already canned. So if a celebrity dies, for example, we don’t start from scratch. We have most of the information prepared already and just need the last details."
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n4bstb | how does anti-dandruff shampoo work? | Chemistry | explainlikeimfive | {
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"Dandruff is often cause by a fungus Malassezia globosa. In addition to the usual soap and other components, Anti-dandruff shampoo contains chemicals like zinc pyrithione (ZPT) which is a fungicide, and selenium sulphide to help treat flaking skin."
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n4cb31 | Why, when observing a drop of water or any sustance under a microscope, bacteria and microorganisms always move on a 2D plane? Weren't they suppose to move on a 3D space and we should see them changing their size because they move closer or further from the lens? | Edit: thanks to everyone that took the time to answer this! You were all very informative :) | Biology | explainlikeimfive | {
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"They would, if you didn't put a cover glass on he slide. But, you need to do this to keep them from vanishing completely. when they go out of the super-thin depth of field of the microscope.",
"Yes. And also, no. Because of lens focus complications. Microscope usage is defined by the “glass slide”. What ever is going to be observed is deliberately limited to a 2D plane so that the lens can focus once, and observation can then happen for prolonged periods of time. As proof that this often still doesn’t work as well as intended— take a look at microscopic photographs of bacteria, etc. You will see faded blurry shapes around the clear and sharp shapes. Those blurs are bacteria/etc. that are further/closer to the lens than the focus is currently calibrated for. Imagine the difficulty in trying to get more than one single bacteria in focus in a 1-inch deep liquid— never mind the difficulty keeping it in focus! To keep it in focus would require it so “swim” perfectly parallel to the lens. Highly unlikely.",
"[Check out this magnified photo of a ladybug.]( URL_0 ) Notice that the leaf gets blurrier the further away it is from the point of focus, even though the blurry parts are only millimetres away from the in focus parts. That's what happens when we focus on very small, up close objects. We can bring into sharp focus a certain depth away from the lens, but anything closer or further away quickly becomes blurry. Often slides under a microscope will place a thin plastic square over what they're viewing which compresses a 3D water droplet into something closer to 2D, but it still has depth. You can find things closer and further in that tiny almost flat space, but you need to adjust the focus to see them.",
"Microscopes do have planes of focus. Where things can be on top of/below other things. Anyone who does microscopy knows you constantly have to move the fine adjustment up & down to see the refractile nature of things. Like even within a single cell, you may need to move up and down to see the different organelles present. Also, when using a \"wet mount\" or some sort of fluid it's typical to coverslip it to a) create a more uniform layer and b) to keep the sample from contacting the objective lens."
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n4d3l3 | how does the body use energy? | When we eat, that food gets turned to energy the body can use. How does that work? I understand how gasoline is converted into energy for your car. Or how coal is burned to create steam and turn propellers for energy generation. But how does the body create energy from food and how is it being used? | Biology | explainlikeimfive | {
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"At the most simplified level I can explain coherently: Carbohydrates contain a molecule known as Glucose, which is the most basic form of sugar. Your body's cells absorb and burn Glucose. By breaking it apart, this releases the energy that was in those chemical bonds, letting your cells trap that energy in other bonds. Glucose + Oxygen + ADP + P --- > CO2 + Water + ATP. (This is actually the reason you need to constantly breathe oxygen and exhale extra CO2). The energy from the reaction gets temporarily stored in molecules like ATP. ATP is super versatile and can transport that energy to other places before breaking back down and releasing it. Most of life's function at a molecular level is just cycles of making bond - > doing work that breaks the bond - > making a fresh bond."
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n4dqet | LDAP (Lightweight Directory Access Protocol) | Technology | explainlikeimfive | {
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"In IT a directory service stores information about objects in a given organization. The organization does not matter, it could be a business, or your home network. Typical object types are users, computers, and groups. Objects have information associated with them stored as attributes. A user object has things like first names, last name, password, logon name, address, etc. Some attributes are required, some are optional, and some are automatically filled ( like date and time stamp of last password change.) LDAP is a standard protocol used by directory services to allow software to query information in the directory. An LDAP compliant directory service stores object information in a certain structure and uses standard attribute names for predefined purposes. They listen for connections on standard ports and support a standard syntax for performing queries. Say I am a software developer and I want to allow my customer to authenticate users with their standard network accounts, and I want to pull in information about the user for their profile in my applications, or I want to check against group memberships to see if they are authorized to access a certain part of the application. I can write my application to support LDAP, knowing pretty much all major companies use some kind of LDAP compliant directory service, such as Microsoft Active Directory, Red Hat Directory Server, or Amazon's directory service. I don't actually need to know which directory server they use, I just write my app to follow LDAP standards and it will be compatible at pretty much any company large enough to use something to manage user accounts in a centralized system. Edit: Thanks for the silver!"
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n4dyug | what makes ankle joints withstand age-related wear and tear, comparatively speaking? | Hip replacement surgeries are commonplace, especially due to age-related damage. But ankle joints don’t seem to suffer the same amount of damage / require replacing as much as either hips (or knees) do, despite being smaller and more delicate constructions. What in the construction of ankles makes them more resilient than other weight-bearing joints? | Biology | explainlikeimfive | {
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"The magic of the ankle biomechanics is more-so in the synergy it has with the foot than simply the ankle itself. The ankle-foot complex (AFC) is an extremely intricate & complex structure with a high concentration of bones and muscles, connected by very supportive and flexible Connective Tissue (Tendons, ligaments, fascia). With the AFC being the first load-Bearing system of the body, we expect these Connective tissues to be far more responsive and adaptable to the stressors imposed from our body and the changing terrain. While the hips may have stronger ligaments than the ankle, the ankle has an uncanny ability to adapt to the changing environment because of the foots ability to evenly distribute the load evenly before sending the force upstream. Summing this up, the Ankles ability to alter its compliance based on the terrain it’s interacting with may cause it be more resilient to the less compliant hip joint.",
"Total ankle arthroplasty, or replacement, does exist, but it's complex and nowhere near as sure-fire as hip and knee replacement. Ankles do pretty well with several hefty screws fusing the joint into one position. There is loss of movement, but it helps with pain. LOTS of people have a lot of foot and ankle pain and arthritis, it's a whole separate specialty of orthopedic surgery."
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n4gofg | How are fish so in sync when they school? | You see so many videos of fish who swim in schools and they all move almost perfectly at the same time it seems. And I know it’s part of their defense mechanism but I still don’t understand how they can be so in tune with each other to be able to look so cohesive. | Biology | explainlikeimfive | {
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"\"How are people in crowds so in sync with each other? They all move almost perfectly at the same time it seems.\" Or even, \"How are cars in traffic so in sync with each other? They all move almost perfectly at the same time it seems.\" It's the same thing. Each unit is following fairly simple instructions with basic goals, and complex flocking and clustering behavior develops from it. In the fish, those instructions and goals might be \"stay within 6in of 2 other fish, but don't get within 1 inch\" and \"If fish in front of me goes up, I will go straight\" with the goals being \"find food not eaten by other fish\" and \"Stay away from predator\"",
"As has already been stated, fish take into account the relative positions of their nearest neighbors to remain in a cohesive school. [Simulation studies]( URL_0 ) have shown that these complex-looking behaviors can be predicted with very simple rules (that is, stay close to your nearest neighbors). Also keep in mind that fish have senses that we do not, so this isn't based purely on sight. Most fish species have a \"lateral line\", which allows them to detect disturbances in the water based on motion."
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n4h4y9 | Why are some materials squishy, bendy, or more spesifically, malleable? | Physics | explainlikeimfive | {
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"There are many different specific reasons why a substance may be malleable. However, in general they all come to the ability for the atoms of that substance to move past each other without breaking the bond they have. One of the most interesting phenomena is the one you'll see in metals that can bend. We like to think of metals as one evenly spaced mass of atoms. However the truth is metals will form crystals within their structures. At the borders of these crystals there are bonds that are stretched and barely holding on. When you bend the metal, the force you are applying slides those crystals past one another, moving that stretched space along the mass of the metal until it reaches the edge. This is why if you bend a paperclip back and forth enough times you will snap it. You've accumulated enough of those stressed bonds at the edges that the mass can't hold together. Larger crystals in metal make less stressed bonds which makes that metal less malleable because the crystals can't slide past each other."
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n4hakl | How does lead turn you into an idiot? | Biology | explainlikeimfive | {
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"If you mean the metal, it binds to your red blood cells where hemoglobin would and reduces the amount of oxygen that is available not only to your brain but your entire body. URL_0 (I used to work at this program)"
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n4hht6 | How do government bonds work | Economics | explainlikeimfive | {
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"When the government needs to borrow money the Treasury sells the bonds to the Federal Reserve System. The FED then creates the money by simply increasing the balance in the government's account. The FED either holds the bonds on it's balance sheet or offers them in an auction where bidders, by invitation only, purchase the bonds. It's through this mechanism, called \"open market operations\", that the FED attempts to control interest rates."
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n4hrql | What is body dysmorphia? | Psychology | explainlikeimfive | {
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"Imagine that you have a brand new red Radio Flyer wagon. It is definitely a Radio Flyer wagon with four wheels and a handle. It is definitely brand new and in showroom condition. But when you look at the wagon, you see a rusted, dented, green colored, no-name wagon. It has four wheels and a handle, and it is definitely a wagon, but the wagon as you genuinely believe it exists does not look anything like the wagon everyone else sees. That’s basically how it works.",
"Dysmorphia itself means a part of the body being an abnormal shape. Body **dysmorphic** disorder is a mental condition where someone is obsessed with a perceived flaw that may not actually be there, or isn't nearly as severe as the perception is. It's a mental condition because, counterintuitively, the bodily flaw isn't the real problem. If the person gets cosmetic surgery to solve the problem, the dysmorphia just shifts to a different perceived flaw. [More info.]( URL_0 ) When talking about this disorder, it's often shortened to \"dysmorphia,\" to refer to the anxiety and obsession, not the body. This is not to be confused with gender **dysphoria**, which is an entirely different thing."
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n4hxpc | What defines the outside border of a star system? | Is it the sphere of influence of the stars in it? Something arbitrary? | Physics | explainlikeimfive | {
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"It depends on the context you are using the difinition in. And we have not been able to explore many star systems so we do not know which is most appropriate for everyone. The sphere of influence is a good definition which we know that we can apply to all star systems. However it may be very hard to measure and changes all the time based on the stars around it. The definitions we currently think is the best is either the edge of the magnetic field of a star or the outer edge of the solar winds. These are close together and gives a very useful boarder where everything within have mostly to do with the star system and everything outside have mostly to do with the galaxy. The problem is that we do not know if this fits for all star systems or if this is something that only fits our star system. We did not even know about this boarder until the Voyager spacecrafts went through it and confirmed its existance."
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n4jcnr | How exactly does aging of cells work and how come some organisms get to live really long lives and some age very fast? | Biology | explainlikeimfive | {
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"Cell aging happens because each time a cell divides there is a chance that the division doesn't happen perfectly and one of the resulting daughter cells has a flaw and doesn't function correctly. This mostly happens at the tail end of the DNA which is the last piece to split when your DNA replicates itself. At the end of your DNA is a tail made of something called Telomeres which are basically junk DNA which exists to try and prevent this DNA damage, but each time your cells divide some of the telomeres are sacrificed until eventually you have none left to prevent DNA damage. Then when your cells split the DNA is damaged and this shows up as aging. Eventually some critical cells are so damaged that they don't function well enough to keep you alive and you die. Different organisms have different ways of dealing with this problem. Some are more effective than others which is why we all live for different lengths."
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n4jlb0 | In Buddhism, how can one pursue enlightenment without being allowed to pursue things? | Other | explainlikeimfive | {
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"That's actually a very tricky question, and quite a lot of writing and thought in the Buddhist tradition has been devoted to exploring paradoxes of that kind. For one thing, it's a bit of an oversimplification to say you're 'not allowed' to pursue things in Buddhism. It's not quite so follow-the-rules as that; it's more like you're trying to cure yourself of the disease that makes you *want* to pursue things. If, in the course of curing that disease, you also happen to do some 'pursuing', it's not like everything is ruined. For another thing, the 'things' we're talking about pursuing, are usually thought of more as stuff related to the satisfaction of our ego's wants. Power, money, lifestyle, that kind of stuff. Enlightenment isn't really a 'thing' in the most simple reading. But not so fast! Like I alluded to, some Buddhist writers *have* asked the question: \"What if, even in seeking enlightenment, we're actually seeking to satisfy our ego? What if we just want to see ourselves as an enlightened, 'good' person?\" And from what I can tell, the most common answer is that this is inevitable sometimes - we're human and we will get caught up in our human patterns of thought - and that we simply try our best anyway. Edit: A teacher named Chögyam Trungpa wrote this: > Many people make the mistake of thinking that since ego is the root of suffering, the goal of spirituality must be to conquer and destroy ego. They struggle to eliminate ego’s heavy hand but that struggle is merely another expression of ego. We go around and around trying to improve ourselves through struggle, until we realize that ambition to improve ourselves is the problem. So the idea that enlightenment can become just another 'thing' we chase for the sake of ego grasping, is one that is taken very seriously.",
"Enlightenment is not a \"thing\" but a state of being, that can't be reached by pursuing things."
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n4kwcg | How did land get an 'owner'? | Other | explainlikeimfive | {
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"> Basically every piece of land nowadays is owned, either by private parties or by the government. Every piece of land is owned by a country *and* a private party. Land you buy from the government is still part of the country and laws still apply. > Can I just 'claim' land myself (rightfully)? maybe some that isn't used? Everyone can claim anything, the trick is to have enough power to enforce that claim and that is what governments and thier armies do. There is no international law about anything so whoever has the power to enforce thier claim \"owns\" the land.",
"Short answer - all borders are made up. Long answer - the first rule of the wild is, \"only the fittest survive\". A close second is, \"you only own that which you can defend\". It used to be that that meant defence thru violence or persuasions, but we've developed fairly sophisticated legal systems on top of that to aid such defenses. All legal borders are made up, but they are backed with substantial force.",
"To quote the great historian of our Era, Eddie Izzard, \"We stole countries with the cunning use of flags. Just sail around the world and stick a flag in. \"I claim India for Britain!\" They're going \"You can't claim us, we live here! Five hundred million of us!\" \"Do you have a flag? \"No...\" \"Well, if you don't have a flag, then you can't have a country. Those are the rules... that I just made up!\"",
"Ownership came about because we're essentially tribal animals. A lot of animals, particularly predators, have a \"range\" or \"territory\" that they live in. A wolf pack generally stays in a certain region and doesn't stray into the area frequented by another wolf pack unless it needs to. They assert their right over that territory by marking it, so other wolves can smell its edges and know a different pack has claimed that space. But if a bigger tougher wolf pack moves in, the previous pack can be driven away. Humans have taken this further. We have our own \"pack\", and within that, maybe our own \"closer family\", and we generally want a certain committed and guaranteed territory that we can be absolutely sure is ours. As society advanced, we developed legal systems to ensure there was no argument about who owned a specific piece of land. As long as you were a part of that society, it was clear that you were the person with rights to that land. And because land produced critical resources like food or stone or wood, land ownership became super important for the developing concepts of barter and money, and eventually centralized government. You owned that land unless a bigger, tougher government booted you out of it. And that remains true today. You can only \"claim\" land that isn't being used if the legal environment you're in allows you to, and you follow the legal process to claim that land. Otherwise, a bigger legally-endorsed organization or military force can just come along and say \"nah fam you don't own this\" and kick you out.",
"To quote Mao, political power flows from the barrel of a gun. Pretty much any small group of farmers could be raped/murdered/killed by even a small bandit force with horses and surprise. So they needed protection. The people doing the protection claimed the land as theirs. Eventually this went on for so long the laws were built by them to protect that right. Thus the joint ownership of land by private parry and state was born. In the English speaking world, this was William the conqueror in 1066. All property law in the English speaking world flows from what he set down."
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n4kwnp | Does light loose momentum after moving through object with higher refractive index or does after coming out that object it again travels at c | Physics | explainlikeimfive | {
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"Light doesn’t normally lose momentum when moving through a medium. If it did then it would still return to travelling at c afterwards because the momentum of a photon isn’t actually related to its velocity (which in a vacuum will always be c) but it’s energy. The energy of a photon is in turn related to its frequency/colour and so the momentum of a photon just depends on the frequency of light. Red photons carry less momentum than blue ones for example.",
"All EM (electromagnetic) waves travel at velocity c (speed of light) in a vacuum. Refractive material will cause EM waves to change energy, and* velocity and become different EM waves (i.e. shorter or longer wavelengths) such as infrared, radio, visible (all colors) ultraviolet, gamma, etc. Edit: sorry typoed a word, light certainly can and does slow down through a medium. E=pc is relevant here, p (momentum) changes as c and E change, also E=hf"
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n4lgzc | Our stomach acid can dissolve all types of food including food like cows stomach (tripe). How come our stomach acid is strong enough to dissolve tripe but not our own stomach tissue? | Biology | explainlikeimfive | {
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"because the tripe isn't producing mucus to protect itself like how our stomach is producing mucus to protect itself. If our stomach didn't have that mucus (for example due to overuse of drugs like aspirin or ibuprofen or because of infection by bugs like H. pylori), the acid would eat through the wall of our own stomach and cause an ulcer.",
"there's a protective gastric mucus lining that protects stomackes, the lining of tripe is scraped away before cooking/consumption",
"Besides our living stomach having a mucous lining protecting it, the tripe you eat has been cooked, usually for a very long time.",
"Because stomachs are machines. \"Why is it so much harder to catch up to someone in a functional car versus one that has been cubed at the junkyard?\" The stomach has to do a lot of active protection (it exudes mucous). Without that, it just dissolves like any other tissue.",
"Your stomach acid is strong enough to eat through your stomach but your stomach constantly produces a mucus lining that is resistant to the acid. People who suffer with acid reflux, will frequently burp/puke a little bit up and it will eventually eat through their lower esophagus. Their was an episode put out recently of Today i Found Out youtube that touches on a man who could eat metal without issue due to especially powerful acid that allowed him to digest metal and a stomach that overproduced mucus that allowed him to survive the stronger acid. He actually made money eating things normal people cant such as: glass, forks, a small aircraft."
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n4lo9s | How come Instagram is not removing bots? Is it so hard or they just don't care? | Other | explainlikeimfive | {
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"They have an incentive to \"not notice\" bots, because bots pump up user counts, and user counts affect stock price. They take some down, but really don't do much overall.",
"They don't care. Or rather they do care but you probably don't see it too much. There are very few bots posting many many messages, compared to the volume. Very few bots sending direct messages. I'm pretty sure they deal with those because they would create a bad experience for content creators and browsers. The main issue with bots when it comes to IG making money is that announcers know not as many people as expected will be real life people looking at their ads. But IG knows it, the announcer know it and this simply adjusts the price of ads to account for that. But for normal users that's just potential followers, likers, maybe some messages but that's about it, even if you know it might be fake, it's still mostly positive things. For influencers they don't even care if the followers are real or not, they just want to boost their numbers that everybody knows is boosted to some extent... IG can't sell followers so they don't really have any good reason to try and ban those, they're not making things too easy so that there is some kind of balance with enough real accounts but overall they probably even benefit from the bots.",
"Have u ever heard of \"the squeaky wheel gets the grease?\" It is kinda the same concept. Bots create issues. And people are curious by nature and now those people are downloading the app or visiting the site to see what's going on. Those downloads and site visit create revenue. It's all about the money. And tbh, most of those bots belong to major contributors or the site itself."
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n4lwl8 | Why does the time in which you sleep matter? | Biology | explainlikeimfive | {
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"It's of extreme importance because it regulates all your hormones accordingly. Irregular & inadequate sleep timings literally changes your brain network activities thereby changing the way you think in some sense. It destroys your concentration, focus & ability to perform at optimal settings. Always sleep on same time & atleast 8 hours. Timings of sleep should be as per your schedule & life. For example :- some people sleep at 10pm & some at 12am. Both should sleep 8 hours minimum. Some sleep at the morning 6am. Hehe. It doesn't matter. What matters is complete sleep. However, scientists say to sleep according to morning routine because of circadian rhythm of our body. Our body keeps exact time & exactly knows when Sun rises If we feed the data by scheduling our sleep according to sunrise & sunset timing. This goes back to hunter gatherer times & was a major factor on why humans were more effective in day than at night & thus the need of houses(shift from nomadic culture to settlements) to stay in at night. Sleep deprivation will lead you into more depressive states/episodes compared to a person who has a better sleep schedule. REM & Non-Rem sleep both of them are important. In 8 hours cycle the alpha & theta waves of your brain needs to be smoother & slower & consistent. If you're not sleeping properly or inadequately your waves pattern will be erratic & thus will lead to more instances where you forgot something like your keys or wallet etc.... **Read** Matthew Walker's - Why we Sleep? Watch documentary - Why we Sleep or importance of sleep something like that. I forgot the name of that documentary. LoL. Anyways, the book will blow your mind & you'll see something we consider as so insignificant & time waste is actually one of the fundamental basis of human biology. Edited just now.",
"There's actually quite a bit of evidence that hundreds of years ago we would actually split our nightly sleep in two--we'd still get around 8 hours total, but you'd wake up in the middle of the night for a couple of hours and chat (or do other things!) with your partner. Of course, at the time artificial light that could easily allow us to work, rest and play after dark didn't exist, and what \\*was\\* available was expensive, so going to bed at sundown and getting up with sunrise wasn't at all uncommon."
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n4lx76 | If we have DNA in all of our cells, how can Gene Cell therapy work without modifying all of our cells? | Biology | explainlikeimfive | {
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"This is why Gene Therapy is best used on an embryo rather than an adult. It's much easier to affect all the cells that way. For something like Cystic Fibrosis, the idea is that you can affect enough of the lung cells to alleviate the symptoms. You can breathe in the Gene Therapy medication, and it should then affect the cells that make up your lungs.",
"Not all diseases mean every cell in your body is affected. Take cancer, for example. If you have a tumor in your kidney, it's only the cells in the tumor whose genes need to be changed."
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n4m7hv | What is Entropy? | Physics | explainlikeimfive | {
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"Entropy is a measurement of disorder. A sand castle has low entropy. It is very ordered. A pile of sand has high entropy. It is very disordered (random). Think of it this way. There are a lot of different ways you can order sand into a pile. There aren't as many ways to order sand into a sand castle, so a sand castle is lower entropy (more ordered).",
"Entropy, in the layman sense is the trend from organization to chaos. Every field has its own definition of entropy. Entropy is a concept to describe the natural decay of a system or object. On the universal scale, entropy is the steady progression towards no movement at all in atoms. On the organism scale, it is the tendency for organs to deteriorate faster than they recover. The definition of entropy depends on context; the concept does not.",
"There's two things in the universe. One is \"matter\" - solids, liquids, gasses, plasma - atoms and molecules and stuff. The other is \"energy\" - heat, radiation, light, motion. There's some overlaps at the heart of things but in general, matter can become energy, and matter is affected by energy. Now usually, energy has a tendency to dissipate - bleed away or spread out - over time. If you pour a hot kettle of water into a cool full bathtub, the place where you pour gets hot, but then that heat swirls around and through the water and eventually it all becomes the same slightly-warmer temperature. Burn a stick and the chemical energy heats the air around it and then also slowly bleeds away. Entropy is what happens as energy becomes more spread out. An example is an old building starts to lose its integrity and collapses - potential energy in the tall building becomes kinetic energy as it collapses, and then the rubble continues to disintegrate over time. A star exploding and spreading its energy through space in a supernova is another. Eventually it's theorized that spreading energy around could result in the \"heat death of the universe\" when there really isn't any cluster of matter that's producing energy, and the universe is a cool consistent temperature. That's a super long way out though."
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n4mp3s | why does Alcohol kindling happen? | Also is there any way to prevent it? Would tapering prevent kindling ?, would this stop the kindling affect asssociated with binging benzos or alcohol? I know a lot about the neurotransmitters, but trying figure out why kindling seems to happen and if it’s possible to prevent when coming off of a substance that was used consistently. Does kindling also happen in Gaba B agonists ? | Biology | explainlikeimfive | {
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"So I lack the a lot of the technical expertise here I suppose, but I am a kindled 34 year old alcoholic. Tapering off of booze will ease your withdrawal symptoms and slowly “shrink” your receptors, but the kindling effect typically happens from REPEATED detoxing and return to abuse over time. At some point those receptors either don’t shrink anymore, the withdrawals ime get worse every time. There’s a lot of factors involved but when I was 25 and went on a run, I’d maybe feel ok after 3-4 days of detox after drinking for a month or two straight, often 15-20 drinks a day. Now, if I drink remotely close to that for two weeks (often less) I’m waking up with the shakes and all that. I do not know of the cross tolerance with benzos, obviously they are the gold standard for treating alcohol wd, and they still seem to work for me but I have never taken them recreationally (not my thing strangely enough considering the pharmacology) for more than a day or two, with no apparent wd or ill effects involved. So from what I understand, if you put your receptors and brain through repeated physical dependency and then withdrawal (causing those receptors to multiply and then shrink) they eventually will stop or become resistant to ever shrinking back to normal. So that means the next time you decide to drink, all of those receptors are activated and your body will become dependent much much faster. I’m sure the terminology and explanation was a bit off, but this is how it was explained by the doctor at the detox hospitol after my 9th time maybe. I had a seizure two years ago, just couldn’t get enough alcohol in me by the time I got to the detox. Doctor said I was kindled and showing symptoms most alcoholics do at the age of 50, after drinking for decades. Thankfully, my runs have gotten shorter and my sobriety lengths have gotten longer, been about two years at this point with very little desire to return. Took a loooong time though. Alcohol and benzo withdrawal are deadly and the wd are brutal. I have had poly drug addictions and by far the worst wd is alcohol imo. I have take. GABA drugs (like neurontin) abusively for weeks at high doses staggered throughout the day (more like 3 days on one or two off because it loses positive effects quickly) and had no wd. Very effective at helping ease wd in my opinion if taken correctly (read:abused) and I have used them to bridge the gap after a short run or help taper many many times, so there is definitely a correlation on how these chemicals are effecting those receptors and your brain. So, you can’t prevent physical dependence if you drink every day or very often to excess, but you can lessen withdrawal by tapering. You will be become kindled by repeatedly becoming dependent and then detoxing, and will definitely suffer more and much more quickly from dependency if you do. Sorry if this is all jumbled or not precise, just my experience so hope it helps."
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