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mraz5o | How does wireless connection bandwidth work, why does the speed differ so much from factors like connection quality compared to wired connections where it's pretty much a set speed? | When you use a wired connection the stability of the connection always stays the same, meaning the device knows when and how it will receive a signal. However, a, for example, WI-FI connection is very unstable compared to a wired, and the connection speed always differs during a period of time. I've always wondered, how does the receiving device know at what speed to expect to receive the incoming signal, and not lose chunks of data when the speed suddenly drops/rises? | Technology | explainlikeimfive | {
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"The speed is always the same (agreed upon before the transmission starts), but packets might have to be resend when something interferes with the transmission. That can be anything from a random other electrical device turning on to something conductive moving through the room. Or even just being too far away and other signals being \"louder\" than yours. Each packet is checked for correctness with a \"parity bit\" wich basically just says \"the last packet should be even/odd\" (or dividable by any number for better correction) so every packet read wrongly you simply repeat it wich slows the speed since more data is sent. You don't have those issues with cables simply because you can shield them (I.E. put a fine metal webbing between layers of insulation). That prevents outside signal from disrupting your transmission.",
"This is taking me back a few years, used to have to explain this sort of thing to customer all the time. The 2.4 ghz range that WiFi uses is used by a large number of other devices so they can interfere with your WiFi connection, the construction of your house can interfere with it, so many things can impact WiFi. If your device is capable of using 5ghz and your router is compatible, try swapping to that. It has a faster top speed, albeit a lower range, but there are way fewer devices also using it, so it will be impacted less by other devices causing interference. As an example, please of devices in the 2.4 ghz range: cordless phone handsets, baby monitors and the like. As /u/luckbot advised, the sending and receiving devices act as if they are at max speed, but it is the external factors that impact it. One thing worth considering is setting up WiFi extenders around the house if you are noticing a problem in a particular part of the house. I had one customer, many years ago, could not get WiFi in one side of the house. Turns out it was 2 old farm cottages that had been knocked through into one house and the old dividing wall between the 2 was full of big metal pins which was effectively acting as a Faraday cage. Set up a rouen on the other side of the wall as a WiFi access point and connected it with power line adaptors and got full coverage."
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mrb4ks | How does my computer know I removed the CPU and put it back in when it was turned off the whole time? | Technology | explainlikeimfive | {
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"I think it’s due to the coin battery in there to keep certain files and programs on the motherboard from getting erased when there is no power to the computer"
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mrbd21 | What really is Ethnic Stereotypes? | Other | explainlikeimfive | {
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"Assumptions about certain cultures or ethnic groups, usually negative. Failing to see groups as individuals, essentially tarring everyone of said group with the same brush, based on perceived qualities, maybe seeing 1 person from said group appearing in such a way and deciding that everyone is the same. E.g. the stereotype that black people are \"ghetto\". People who hold negative stereotypes may not actually personally know people from the group that they are judging and may have just seen poor representations on TV or in the media to draw their conclusions from. (P.S. I'm black so don't wish to offend anyone with my example by the way.)"
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mrbkz6 | what causes short-memory loss ? | Biology | explainlikeimfive | {
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"There is an area of your brain called the hippocampus which is responsible for converting short term memory into a more permanent memory. Short term memory loss can be caused by a dysfunction of your hippocampus.",
"It can be physical brain damage or due to psychological issues The centre of both is your Hippocampus, the part of the brain that deals with memory You can work on your Hippocampus to grow it/make it stronger after a physical blow or due to mental damage (Depression, alcoholism etc) however obviously the underlying issue should be dealt with first"
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mrbudy | Why do datamining leaks happen? | Technology | explainlikeimfive | {
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"> Why do datamining leaks happen? For the same reasons all security breaches happen - because people have a grudge against their employer, don't shred their documents properly, greedily click that link for the 10000€ bank transfer from Nigeria or think password managers are for chumps."
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mrc9ni | why does it take 10 000 hrs to be really good at something? | I always thought this was really weird. But why do we get really good at something once we spend around 10,000 hours on it? Does our brain just master the connections involved. I know we’re all different but is there an approximate time that we can spend on some thing to get regularly / avg person good at it. | Biology | explainlikeimfive | {
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"It’s just a very rough estimate of how many hours of practice *on average* proficient musicians have had. Some of them needed less time than others. Other skills might require less time to become proficient.",
"simply put, by doing the same thing over and over, you collect more and more data on what you're doing and how it works. And not only that but you also automate the movements and thought process that goes with it. You're basically shaping your brain to be more fit to the task, as it starts to become more a \"reflex\" or an \"habit\" than a \"thought process\". Think of writting for example. When you started to learn how to write, you had to think of the word, how it is spelled, how to write the letters (how they looks + how to draw them). And now, you are probably writting without thinking of it, because your brain automated all that thought process. Now, as for the time required to get good at something, it's not only a question of hours, but also a question of intensity, of how you work, the subject itself, the bases you already had,... the 10 000h is just an estimation."
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mre1jn | Can we create our own internet ? | Can we create a connection to the internet ourselves without having to use a cellular 3g/4g subscription / wifi subscription? | Technology | explainlikeimfive | {
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"The internet isn't a resource like wood or water that can be \"produced\". It's a connection to the rest of the computers/servers/sites on the network. It's a bit like, \"can we create our own, separate road network?\" Yes, you certainly can, but you'd need to build your own connections to each place that you go to. You'd need to ask your supermarket if they would let you build a separate road connection to their property, with a separate parking lot, just for your users. Same for the drug store, Amazon warehouse, and any other company/location you'd be interacting with. You'd need to get approval from the town/city/national governments to build your road system in parallel with (but not interacting with) their roads. It's not impossible to do it. But that's about the best argument that can be made: it's not physically impossible.",
"If you're willing to go through the process for gaining government approval to create your own infrastructure for data communications between customers and get enough people to use your network to make it worthwhile, i guess. That's a very steep mountain to climb",
"ISPs don't make the internet they connect you to it. If you want to have access to the internet you have to connect to it somehow. The easiest way is through a provider, because that is what they do, but you can connect to any computer connected to the internet and get your access to it routed through that computer. The ISP themselves connect to each other through a process called peering and they will do the same for you if you have enough computers that connect through you to the rest of the world. You can also use the protocols that the Internet works on and build your won separate network. Any two computer connected to each other via the Internet Protocol (IP) are in theory *an* internet, not just the Internet that everyone else uses.",
"URL_0 /r/darknetplan Folks have been working on a separate network for a while. What it really needs is users and content.",
"Yes. You can pay for a link, through the phone company, of install your own dark fibre, paying the city and utility costs, connecting your house to the nearest peering point. Then you can buy a cvrrier class router ($150K) to install at the peering point. You may need to pay peers for traffic, unless you connect a sizeable number of users. This is what ISPs and community broadband companies do.",
"The Internet is largely built on trust. No one really likes to admit it, but its true. Trust that no-one will fuck things up. And that makes people twitchy. Do the people you want to connect to trust that you are who you say you are? If so, in theory it boils down to a wire connected to a comms cabinet, connected to an exchange, connected to a data centre connected to everywhere else in the world. HOWEVER in the real world, almost everything is hosted by a depressingly small number of organisations. AWS hosts nearly half the WWW. Google took over Usenet many years ago. If you can't get to them, you can't do jack. And if they say \"no\" you're fucked. Setting up your own connection is possible, but unbelievably expensive, will require massive negotiations with major corporations and frankly really not worth it. Back in the 70's and 80's maybe. Not now.",
"There are several different questions you could be asking. I'll try to answer all of them. - *Can I connect to the Internet without paying somebody a monthly fee?* No. - *Can I connect to the Internet without using a radio?* Yes, but you'll still have to pay an ISP every month. If you don't want to use a 3g / 4g / 5g cellular connection, you can get Internet from a cable or DSL provider in most places. You still have to pay for this subscription. If you don't want to use Wifi, you can connect your device to your router with an [Ethernet cable]( URL_0 ) instead. Most desktop PC's and many laptops have built-in Ethernet connectors. You'll need an Ethernet adapter for your phone, tablet, etc. - *Can my friends and I create our own network?* Yes. You don't have to pay anyone a monthly subscription to connect computers together. (You still have to pay for parts and electricity, of course.) You can connect multiple computers together using Ethernet cables to connect them to a switch or router. You may need to make some simple changes to the OS or router's networking settings. You can even get rid of the cables if you use a Wifi router. The catch is that the computers have to be physically connected with Ethernet cables, or within a few dozen feet of a Wifi router. So for example, if you wanted to visit your friend's website, you'd need to have your friend physically bring a computer over to your house. Your friend would need to run their webserver software on that computer. You could visit the website running on the computer in your house. There's a lot of different server software these days. So you can create a network with websites, chat, downloads, and so on. All running on computers in your house. There would be no possibility of connecting to Reddit, Google, Facebook, and so on. Because those websites are running on computers you're not connected to, outside your house. If you wanted to connect your network to computers in different houses, you'd have to physically connect a wire between the houses. This might be feasible to do with your next-door neighbor if you're willing to spend a couple days digging a ditch, putting the cable in it, and figuring out how to safely drill a hole in the wall to get the cable inside each house. If you're talking about multiple friends in different locations, you'd have to get a bunch of government permits and pay millions of dollars to run a miles-long cable through a bunch of different properties you don't own.",
"You could setup a network of packet radio modems/computers via shortwave radio. Or You could setup a mesh network of XBee Pros connected to computers that have up to a two mile range each outdoors.",
"Yes. In fact most businesses do this and call it an intranet. Some hobbiests do it over radio waves with HAM radio or WiFi. & #x200B; All you need is a way for the computers to connect to each other. You just setup a little infrastructure and you have your own internet. Now the downside is that it can't access the rest of the internet so the only websites/etc available are those you're hosting on your private internet.",
"If you are asking about having a connection to the internet that does not require some sort of service that is already in place, then no, all connections to the internet that exists have to be done through some sort of existing connection. This connection allows access to the network of computers that the internet exists on. You do not necessarily need a \"subscription\" as there have been ways to \"hijack\" an existing connection, but again this is using an already in place connection."
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mrecr7 | What does it mean when someone dies of "natural causes" or "old age"? | Biology | explainlikeimfive | {
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"The DNA in your cells duplicates itself every time the cell divides. Unfortunately, this process is not perfect, and in particular, the \"ends\" of the DNA chain tend to not get copied properly. In order to avoid issues, there are \"useless\" strands called telomeres on the end of your DNA, so if the ends break off during duplication it doesn't damage anything vital. However, these telomeres only have a limited length and don't regenerate, so eventually there will come a point where the cell divides but the DNA in it suffers damage which causes the cell to die. As cells die and are not replaced the systems in your body start to break down, and eventually they can't sustain your life--you just die. This is dying of old age. Dying of \"natural causes\" can really mean any number of things that can kill people--e.g. a heart attack or a stroke is a \"natural cause\" even if it kills you before your time.",
"The various cells in a human body get progressively worse at performing their respective function with age. So at some point they can’t do their job well enough to keep the body alive anymore. That’s what “dying of old age” means. But in reality it’s usually cancer or cardiovascular disease that kills old people."
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mree9r | why do shoes disintegrate when left unworn (for extended period of time) and frequently wearing them actually prevents/delays disintegration? | Other | explainlikeimfive | {
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"I am assuming you are talking about leather shoes. The leather is a natural product, with time the atmosphere dries the leather out slowly (imagine like a piece of bread left on a counter top). The loss of moisture hardens the leather. When you use the shoes, you sweat into the them, this replaces some of the moisture, this is also why you should be polishing your shoes regularly. The polish helps to protect the leather with wax and other products to keep it in a good condition and supple.",
"For the soles decomposing, it's not so much being unworn that deteriorates them as time. The soles are sometimes made from crappy plastics that degrade",
"Ooh, I know this one (having had a head office job at a shoe company)! This is due to hydrolysis in Polyurethane outsoles! PU is made of specific molecules, a bit like making something out of Lego, but each building block is made of a bunch of individual Lego bricks. Water likes to steal atoms from the PU molecules, a bit like one of your friends coming over and taking every fifth Lego brick from something you’ve built. When enough bricks are stolen by your friend the structure falls apart. This is what happens in hydrolysis - water reacts with the polymers and breaks down the complex molecule.",
"Saltwater is a natural preservative. When you don't wear your shoes, they oxidize - a layer of deterioration forms and expands on surfaces, including the soles. Similar to rust, if the rust isn't removed, the metal is consumed. By wearing your shoes, oxidation is removed by friction and the sweat keeps the material supple.",
"It's just like dry rot from a tire. It's not the use or lack of that causes damage, its mainly what happens between these periods. if kept in a climate controlled environment it will easily last years. I still wear shoes from high school and that was 2010",
"Yep. Happened to me. Not “cheap” shoes. Nikes. Sat in the laundry room all winter. Tried to put them on in the spring and they fell apart, as if their glue had stopped working.",
"I assume you're talking about the soles falling off of running shoes. The synthetic materials used to bond the sole to the boot simply degrade and fall apart over time.",
"This happened to my girlfriend last month. Put on a pair of shoes that she hadn’t worn in years. We got in the car and went to the grocery store. At about aisle 2 I noticed some weird stuff on the floor. I thought to myself “damn this place cant even keep their floors clean”. Two aisles later she notices a trail of crumbled rubber following her around. By the time we left the rubber had fallen off and she shuffled to the car thoroughly embarrassed.",
"Thats a great question! I recently bought some booties on Posh app (they were brand new, never worn -forgotten in someones closet , i assume!) then when i wore them for the first time , the inside lining pretty much fell apart all over my socks! Ugh (cant tell anything wrong from the outside , but bcuz they were a lil too narrow on my wide toe base-was considering re-poshing them!) prolly cant now bcuz of it! Guess i will try and stretch them out , super cute!"
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mretf2 | What do they do with human bodies that nobody wants? | Lets say you live your whole life alone and isolated, one day you die and the only reason why somebody found you was because of the decaying smell. What do they do with your body? | Other | explainlikeimfive | {
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"Into the “Pauper’s Grave” you go. Cities maintain a cemetery for the unclaimed bodies that turn up. In large cities these can be considerable - NYC buries over 1000 unclaimed bodies on Hart Island every year.",
"There's a documentary on this subject available on YouTube - **A Certain Kind of Death**. Depressing, but very well done and interesting. Basically they'll first treat you like any other unexplained death- investigating the circumstances and deciding if you died naturally or not. If you did, then investigators will look into your background. They'll try to trace living relatives, friends, or anyone else who might know what your wishes were. If you left a will, great. If you already bought a grave plot or made burial arrangements, even better. The state will basically do its best to carry out your last wishes if they're known, or turn you over to a next of kin. If you die completely alone- no living family, no friends, no will, no arrangements, then in most cases you'll be cremated and your remains stored for a period of time (in case a next of kin appears) or interred in a communal grave with other unclaimed decedents. Your property will be sold at auction and the proceeds along with your financial assets used to pay off any outstanding debt you owed. Any remainder usually goes to the state.",
"Years ago I worked for a funeral home / agent. I participated in collecting a total of three deceased who lay dead in their homes for a while without anyone missing them. One of the homes looked like a bomb had gone off there, but the two others was so painfully tidy. I don’t know why that made such an impression on me. Maybe I imagined how they had spent years alone with nothing else to do but make sure everything was spotless and lined up."
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mrev4o | How does refrigeration work? And are their limitations in size both small and big? | Technology | explainlikeimfive | {
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"Basically, you have an easily liquefiable gas at the back of the fridge, typically some sort of halogenated carbon based molecule like a Freon (includes the greenhouse gas families CFCs and HFCs). Gases can change temperature fairly easily with pressure, and will decrease temperature as they expand, that’s why deodorant feels cold when you spray it. The refrigerant gas comes into contact with the inside of the fridge in a sealed system after passing through an expansion device, where it will then absorb energy from inside the fridge, cooling it down. It is then moved to the zigzag of pipes on the back of the fridge using a compressor, where it then heats up to a higher temperature since the pressure increases. The heat is bled off into the atmosphere, then the gas is depressurised again into the fridge, completing the cycle. There aren’t really any limitations per se, hence why you can have small drinks fridges, but it’s a lot more efficient at larger scales since you’re using less energy per volume of air to keep it cool because of the cube square law - volume increases faster than surface area. Surface area is a major factor in transferring heat, since it’s the boundary where heat can leave a system."
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mrf3ms | In computers, why do some files, even if they are the same size, take longer to be moved or deleted than others? | I noticed this when I deleted a 2 GB video file on my laptop today, which took less than 5 seconds. But when I deleted a separate folder that was smaller than 2 GB, it took way longer to get deleted. | Technology | explainlikeimfive | {
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"This has to do with the way computer usually handle such things as deleting or moving files. Normally when you delete a file, the computer does not actually delete the data itself. Instead it goes to a sort of index where it has a tabel that says where each part of a file is located on the storage device. You can think of it as going to the table of contents in a book and striking out the entry for a chapter and what page it is one. If you flip though the book you will still find the chapter, but if you only look at the table of contents it is gone. From that metaphor you can also see why striking out a single chapter that goes fro a hundred pages is faster than striking out 100 chapters that are only a page long each. Something similar happens if you rename or move a file around in the same drive. The file itself stays put you only mess with the entry in the table that says where what is. You can move a file that is hundred of gigabytes from one folder to another in almost no time, but moving a hundred tiny files takes a bit of more time.",
"The video file is one single file. So even though it's \"bigger\" at 2 GB, it's just one thing that the computer needs to pick up and drop in the recycle bin. The folder has *many* files. Even if the folder itself is smaller than 2 GB, the computer has to figure out how many files are in there, how big they are, then basically pick up and drop off each one individually to the recycling bin. Sort of like if you're moving into a new place and you've got one bed, and then you've got ten boxes that don't have too much stuff in them but they take up the same amount of space as the bed. You'll probably get that bed into the house in one trip, but it's going to take you multiple trips to take all those boxes in."
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mrfz4q | Why does turning my WiFi router on and off or turning airplane mode on and off on my phone make my internet speed faster? | Usually I do this whenever I get speeds under 1mbps, then after about 10 seconds my internet speed jumps to about 15mbps. It's quite slow but I live in a third world country so it's all I've got. | Other | explainlikeimfive | {
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"Do you have satellite internet? Or use a mobile hotspot? Those aren't fiber or even POTS speeds. If so, them more than likely when you are restarting your router, it's connecting to a closer sattelite; it should do this automatically but your router might have a bug preventing that. If you don't, then ignore the above; the longer you keep a router on, the more \"clutter\" there tends to be. Tasks can stall, data can \"misfire\" and back up in the memory, and bandwith space becomes more occupied. Also, your router will try to issue IP addresses to anything that connects to it, so if you have alot of devices that connect to that router (Xbox, phone, laptops, etc), that's likely adding to the slowdown. Restarting the router clears all that clutter out and lets it form fresh connections. Airplane mode is essentially a \"soft reset\" for phones in this regard, as it disconnects the phone from cell networks and data.",
"You probably have an old phone, an old router or lots of devices hooked up to your router/modem. Your phone is assigned numbers to identify it to the router modem and isp. When lots of devices are hooked up, the memory on the modem or router can get bloated. Disconnecting the wifi and reconnecting forces the modem and router to look up your connection, sorry if shaking it to the top of the list of you will. Some things to try: Turn off your router and modem. Forget the wifi on your phone and any other device that has the problem. Turn the modem back on, wait a minute, then turn the router back on, then reconnect your devices. If that doesn't work, contact your isp about a signal reset. This is particularly helpful with fiber and iphones. Ideally you would turn off your router, forget the wifi on your devices, turn on and off the modem, request a signal reset, then turn on the router and hook your phones back up. If that doesn't work the problem could be an old router. Check for firm ware updates, they may help. Consider doing a factory reset too. You can figure out if the problem is the router by hardwiring a computer to the modem and running a speed test and running it again by wifi."
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mrg46j | How can you die from stepping on a rusty nail? | Biology | explainlikeimfive | {
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"The nail punctures your skin and lets a soil bacteria called *Clostridium tetani* get deep into your body. Once there, it produces a toxin that interrupts muscle function and severe infection can kill you. The rust itself doesn’t do anything, but the wet and dirty conditions where you might find a rusty old nail may harbor the tetanus bacteria.",
"You get tetanus. Tetanus is a bacterial disease that ravages the body, and has about a 10% death rate with today's medicine (much higher before modern medicine). It causes all sorts of problems with the nervous system, causes muscle spasms that are strong and very painful (can even snap bones). If you get the tetanus vaccine after you step on the rusty nail, you'll be fine. Or if you've had it recently.",
"The same way you can die from any seemingly minor wound. You get infected, and that infection can kill you. Rusty nails are particular concerning because they are good environments to harbor the tetanus bacteria. Tetanus doesn't like oxygen, which means it isn't something we encounter on a regular basis, but the deep nooks and crannies of rusty items tend to be low-oxygen environments where tetanus can survive. The squishy insides of your foot also tend to be a low oxygen environment where the bacteria can survive. So if it manages to get in there it can become established. One its established the bacteria will make toxins that interfere with your muscles working properly, which cause a disease known as \"lockjaw\". Lockjaw is characterized by really bad muscle spasms, sometimes sever enough to break bones. These spasms can be fatal (something like 10% of tetanus infections are fatal), particularly if they prevent someone from breathing."
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mrgpla | why do computers sometimes make horrible buzzing sounds when crashing/locking up? | Just had this happen to me for the first time in a while and it always catches me off guard. To give my example, I was listening to music on my PC, and mid-song the PC completely locked up and a loud buzzing sound came through my headphones. I've had it happen in the past with other PCs and with game consoles as well, but why does it happen? | Technology | explainlikeimfive | {
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"The sound hardware in a PC is designed to work with as little interference from the CPU as possible. To that end, it's generally set up so it can play a chunk of audio from memory without interference--all the CPU needs to do is update the location the audio hardware is playing from every now and again. If the system has completely locked up and is no longer responding, the audio hardware will often just keep playing the last little bit of sound it was told to over and over again--depending how long that sound fragment was you might get an obviously repeated bit of music, or just a buzzing."
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mrgskc | Why do you take skin from an other place of your body to treat a burn wound? | Biology | explainlikeimfive | {
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"Because a wound which is created deliberately by a surgeon will heal much cleaner and neater than the random damage caused by a burn. It also makes sense to use the injured person's own skin for this purpose because there's obviously no chance of his body rejecting it as foreign material.",
"They’re used to replace areas where skin cannot grow back due to the damage and areas where scarring will be particularly bad. While the graft is a wound, it’s not a “new” wound. It’s a way of teaching the body to grow healthier skin in a damaged area where a wound already exists."
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mrgtr1 | As growing pains are a thing in adolescents, with bone, joint and muscle aches, why isn’t that pain also constantly present for infants and toddlers who are growing at a much faster rate with their bodies subject to greater developmental stresses? | Biology | explainlikeimfive | {
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"Babies and toddlers have the same growing pains for both their body and their developing minds. Their perception of the pain may be different from when they are older. In general, they will be more fussy and easily irritated, sleep and eat poorly, or just cry for no reason. For some babies and their unfortunate parents, these symptoms are not too different from the everyday experience.",
"who says they don't? Truth is they do experience growing pains, but seeing as they are infants, they usually express this through crying, being fussy, sleeping poorly, etc. and most adults overlook this because well.. infants do that a lot anyways.",
"Babies grow in spurts, sometimes growing multiple centimeters in a day! Then they have periods of stasis (no significant growth). In these growing periods they are VERY fussy. EDIT: \"Dr. Lampl measured thirty babies daily and found that babies grew between 0.5 and 1.65cm in one day, between two to twenty-eight days of no growth. These growth spurts changed their sleeping patterns, inciting tantrums as well as insatiable hunger. \" [ URL_0 ]( URL_0 )",
"There’s a documentary on Netflix called “Babies” where someone explains this. She did a case study where she would measure babies every day and ask the parents for any notable behaviors or what they did that day. She came to understand that babies grow one to two* centimeters in one day, not over time. The parents would report that the babies were particularly fussy or throwing tantrums on those days, so they actually do react. We just don’t always understand why since they can’t talk yet. Edit: *previously said several centimeters but it’s not quite that extreme. [Here’s a link]( URL_0 ) to the study if anyone is interested.",
"\"Growing pains\" have not been demonstrated to correlate with growth spurts. It is a term used to describe limb pain in children between around six and twelve, but the causes are still unknown and there is no link with body growth. So the premise of this question doesn't quite work.",
"I always assumed 'growing pains' was a euphemism for the emotional trauma of adolescence, not actual physical pain. Huh, well TIL.",
"This might be helpful. I have Ankylosing Spondylitis. Im my patient group, a lot of us had what doctors called “growing pains” but were actually misdiagnosed symptoms of juvenile arthritis, that after a while turned into full blown Ankylosing Spondylitis. So if your kid is complaining, take it seriously, the earlier the diagnosis the better. Edit: Thank you for all the upvotes, this was my first Reddit comment ever.",
"There actually isn't any proof that growing pains exist. There is no cause known for the mystery pains that kids/teens get. But the most common theory is that is from muscle overuse from the day",
"They say growing pains are present in kids and adolescents, but does anybody else still get the same pains in their shins despite being an adult? I get them way less frequently, but the pain is such a distinct feeling that I know it’s the same pain as “growing pains” I’ve had when younger (yes I know they’re not definitively linked to growing, I don’t think I’m getting any taller at this point lol). They never really went away, just happen way less frequently",
"Had to give my son Ibuprofen from the moment on that he could speak and identify the pain. His legs/knees will hurt and he will wake up and cry and just go ballistic. I think the first time he was able to make it clear to me it was growing pains was at around 2 years old. Tried everything we could but only Ibuprofen made him stop bawling and go back to sleep and it's the same these days 2 years later. He will often recognize the kind of pain before we go to bed and will request Ibuprofen. If I try to make make him sleep without it and it works he will wake up 2 hrs later screaming bloody murder until I give him some - 100% of the time so I know he's not even faking it. I had bad growing pains as a child and remember those nights and my mom never gave me any pain relief and I remember crying desperately and asking her to make it stop. She said the pediatrician never once told her to use pain meds for growing pains. I want it different for my son and not have him have to go through hours of pain. EDIT: Wow, people are so fast in assuming the worst from people on here... I take my kid to the doctor regularly - like every parent should. The pains are confirmed to be growing pains by our pediatrician. I am of course giving him Ibuprofen for kids - in kids doses. Are you guys even aware that Ibuprofen for babies exists? The Ibuprofen is what our doctor (and other doctors we have seen) recommends. You guys act like I stuff my kid with adult doses of Ibuprofen on a regular basis - which is not the case. I'm not dumb, I'm doing what the doctor tells me to do. My niece has had the same growing pains throughout hef childhood and always got Ibuprofen as well. I had to suffer through these pains without any meds and I am glad my kid doesn't have to. How tf am I supposed to get my boy addicted to Ibuprofen if he gets one does on like 6 nights a year for growing pains? He gets Ibuprofen for a fever - like our doctor recommends - and it says in the description that they can have it every 6 hrs for fever and pain. He has had a broken foot and guess what a different doctor from a specialized kids clinic gave us - Ibuprofen. I'm not gonna withhold recommended pain meds from my kid and make him suffer on purpose especially because I know how it feels. Oh and he never keeps on asking for it like a druggie, after events like those. He actually doesn't like taking it very much BUT he knows his own body and knows when it's growing pains and he needs it. Gee some people...",
"Growing pains aren’t actually a proven thing, as others have mentioned. But I would like to add that babies have a completely different pain sensation that you are probably familiar with. Babies nerves are super juvenile, and underdeveloped for the most part. A lot of their nerves don’t even have myelin sheaths yet (one of the reasons they can’t walk until they are 1-2). So it’s possible that babies don’t sense the “growing pains”, if they exist.",
"This is an interesting question. Although the name “growing pain” might be associated with literally pain from bones and muscles stretching out and getting larger and stronger... is is not that. We don’t actually *know* what that pain is. But a good hypothesis is that it comes from young children playing around and running too much, tiring their muscles and body parts and therefore making them feel pain from that ache. If this is true then... toddlers wouldn’t feel this pain since they barely move around. When they start doing so and exaggerate they are at the age where the known “Growing pain” starts",
"I'm so confused, I don't recall having growing pains as a kid. Did I forget about them or do some people not realize they're having them??",
"Maybe it is. They cry a LOT, and are cranky a LOT (esp into toddler phase), and maybe that's part of why. They don't speak at that age and they likely forget by the time they do so we don't really have any way of knowing.",
"I grew 8 inches in less than a year and have never experienced growing pains, I always assumed they weren't actually a thing",
"Is it normal that I never experienced that at all? I mean I read about it a lot on the internet but I didn't know that was a thing before lol.",
"Life is pain. We're a hot bag of raw nerves that basically only know how to react to stimuli. If you think about it, even the things called \"pleasure\" are just a temporary, momentary lessening of pain. Then it's right back to the horror.",
"You've never been around a baby/toddler who is completely fussy and pulls at their toes/legs/arms and just can't seem to be settled down for anything? That's basically the same thing. Adolecents can just say \"My feet are cramping\" so mom/dad/whoever can go \"okay here, this is what you do to fix the pain.\"",
"elasticity. think of it like you are in outer space in a sac of goo and you get squirted out into the elements and your gooey soft body is supercharged with mothers milk/necessary nutrients and your consciousness and senses are just beginning to fathom the space around you. by the age of adolescence whatever that vague term implies, you are more aware of your senses and your fluid goo body has begun to harden and that shit hurts. for some. others like myself only got the occasional debilitating back pain. others suffer worse.",
"Why do you think they cry and fuss so much?",
"growing pains aren't caused by growing. stress in adolescense actually causes the physical pain. it is a common misconception though.",
"“Growing pains” refers to the pains of navigating life as a young person, not something physical. If you feel pain just from growing, see a doctor.",
"All I can say is that I know nothing of growing pains, other than they were great for getting me out of playing winter sports at school (rugby and football which I absolutely hated) with a note from the doctor. The doc wrote me a sick note for the winter, excusing me from games lessons, after I told him my knee hurt but I wasn't clever enough to come up with how I'd hurt my knee and just old him it hurt and I don't know why. He wrote \"osteochondritis of the knee\" on my exemption certificate and I asked him what that was (it sounded pretty damned serious to me) and he said \"It means your knee hurts, probably growing pains\" and literally winked at me. I think he understood my game as I had told him I needed a note for school and we were playing rugby."
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mrgwj3 | How did old NES cartridge games save your game? | I mean the ones like The Legend of Zelda that saved your game without the use of passwords. How was your game saved on the cartridge? Did it work the same way as an old floppy disk? | Technology | explainlikeimfive | {
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"It saved on a small memory chip inside the cartridge. They had a small battery (much like, probably even identical to, the ones you find on computer motherboards). After a long enough period of time those batteries do die and you do lose saved progress and the ability to save until you replace the battery (particularly anything you save is lost as soon as you remove power).",
"They would typically have battery backed ram. Flash memory wasn't a thing yet, but RAM was. Specifically SRAM which stores data as different transistors being activated/deactivated. It looses data without power so there would be a coin cell on the board to keep your saves.",
"The cartridge has a RAM chip dedicated just for saving your game progress, and a little watch battery just to keep that RAM powered when the NES is turned off / the game is removed from the console. I forget which exact chip is the game-save RAM, but you can see the battery in this picture of a crystal-clear NES cartridge. It's the silver circle on the top left of the circuit board: /r/gaming/comments/5slkhc/ Fun fact: On the original NES consoles, you were warned to always hold the Reset button when turning off the console with a game that had save data. The original NES's Ricoh CPU didn't have any internal circuitry to make sure it powered off relatively gracefully, so random data could get written to random addresses when it powered off... including the game save RAM. Holding the Reset button would hold the CPU in a Reset state preventing this from happening.",
"Games that had non-password save options had a battery inside which allowed the cartridge to store the save data when the console is powered off. See a picture here: URL_0 This holds true for other cartridge-based systems like the SNES/N64, Sega Genesis, etc.",
"Cartridges in general were basically add-on computer parts, so they would come with RAM and disk memory and sometimes added processing power. The differences between graphics for example on the SNES level between launch games and games at the end wasn't just upgrades in development, the hardware in the cartridge was significantly upgraded as well.",
"> Did it work the same way as an old floppy disk? Actually, yes, just probably not the version you played. The first Zelda was released initially for the Japanese exclusive [Famicom Disk System]( URL_0 ), a floppy-based addon to the Famicom that allowed bigger games, cheaper production, and yes, saveable games. Previously gamers had to rely on passwords or a even a [clunky cassette tape addon]( URL_2 ) to save their games. You could even take a special disk to [kiosks]( URL_3 ) at some stores and download new games and extra content to it. 80s DLC! Gaming Historian has a [great overview of it]( URL_1 ). It never released abroad and cartridge tech improving with battery saves and greater capacity meant games like Zelda could be released to the foreign market on cartridge."
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mri81h | How do we retain memories when our brain cells are constantly being regenerated and replaced? | Biology | explainlikeimfive | {
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"Brain cells are not constantly being replaced. Neurons in the cerebral cortex, for example, are not replaced when they die. That's one of the things that makes brain cells different from skin cells.",
"Think of it like this.... our brains aren't just the cells within it, or that (simplicity sake) 1 cell equals 1 memory. Rather, it's a collection of noodles made of cells and the noodles can intersect other noodles. Each length of noodle is an imprint of a memory. Because the noodles are infinitely small and intersect each other, there is a near infinite possible 'paths' to follow to imprint a memory on it. So, individual cells that makes up a noodle can be replace adn the surrounding cells of the noodle can help fill in the gap of memory it has left (bio-error-correcting). Additionally, the noodles aren't just for memories, but how to move our bodies. To stick out yoru tonge might be one lenth of noodle. If you get brain damage and that tongue-sticking-out-noodle is broken/severed/missing-a-chunk, the brain can also re-route the path to make a new tongue-sticking-out-noodle that reuses existing good pieces of the previous noodle, or an entirely new noodle. so, the NeuroPathways of the brain is just a collection of noodles."
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mript7 | How the crypto market is an interesting investment and not just the next bubble, ready to burst. | Economics | explainlikeimfive | {
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"It can be both. In the 1990s, there was a .com bubble. That doesn't mean that websites in general were a bad investment, as given by the fact that we still have them today. There is just likely too much hype around it.",
"Just because something bursts doesn’t mean it’s not a good investment. Bitcoin surged in 2017 then fell for 2-3 years and now its back at an all time high. Also the underlying technology around crypto, blockchain is pretty revolutionary. I work in very traditional corporate finance and all the 70 year old boomers at my work are well read on blockchain, understanding hashes and double spending because they believe blockchain will completely change the finance industry.",
"The thing about bubbles is that, up until they burst, they're an investment opportunity. Knowing when that burst will happen is inherently impossible, since it takes so many factors to actually trigger the burst.",
"It can in theory be both simultaneously. The idea behind making money in the stock market is buying when prices are low and selling when prices are high. Will cryptocurrency crash? I’d say it’s almost inevitable, yes. The question is *when* it’ll crash. 2 weeks? 2 months? 2 decades? Nobody knows. Thing is, while people *think* it’s valuable, it is. As soon as everyone realizes how shaky and unusable it is it’ll crash, but that could take years or even decades. In the meantime, as it remains a fad, we see the value often skyrocketing. The risk comes from the fact that we don’t know when it’ll crash. If you time your investment right and get lucky, you can make a shitton of cash."
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mrjba3 | Why are PS4 and PS5 unable to read PS1 or PS2 discs? | They are clearly able to emulate the games based on the PS1 and PS2 games being available on the digital storefront. Edit: Thank you all for the informative replies. | Technology | explainlikeimfive | {
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"> Why are PS4 and PS5 unable to read PS1 or PS2 discs? For the same reason a VHS player isn't able to read an SD card. It's not built for that kind of application. The PS4's and PS5's drives are physically unable to read CDs, only Bluerays and DVDs.",
"PS1 and some PS2 disks are based on the CD standard. The drive in a PS4 (and I assume PS5) doesn't read CDs. Among other things it's only equipped with lasers for DVD (650nm) and Blu-ray (450nm).",
"Main reason: Different CPU architectures. Example: Moving to a completely different country and trying to read the news paper in their language with no prior lingual experience of that country. Imagine the code of the PS1 games being one language and the code of the PS5 games being another language.",
"Several reasons. But the main ones are quite simple. Fully emulating a console so it works with all discs would be difficult. Games they control can be modified to work (assuming they use emulation in the first place - they might be ports) They don't make any money from you if you use existing games.",
"CD, DVD and BluRay all use different lasers with different wavelengths. A lot of commercial players like the ones you get for computers or media players does come with multiple lasers that can read all disk formats. However PlayStation have chosen to save some cost by only including one laser. There are also some other differences in the tracking mechanism which makes them incompatible. They used the tracking of the grove in the CD to prevent illegal copying of the disks but this made the hardware a bit more complicated which they did not add to the later DVD and BluRay players in the later versions.",
"tldr; it's not worth the cost and headache to develop and support the functionality. To break it down further: 1. As disc technologies developed data was packed smaller and tighter to fit more onto the discs. Each one requires different lasers with different resolutions built into the drives to read the data. 2. As consoles developed the code or language behind them changed. To read and understand the code from an earlier model requires translation (the emulator). It's an oversimplification but you could compare it to if you only speak English and you want to talk to someone who only speaks Spanish you would need a translator of some kind in the middle to listen to one language, convert it to the other language, and back and forth. You need to find or build that translator (time and money), using it will consume resources (processing power, memory, heat), and it's very easy for an 'incomplete' translation to occur (bugs, bugs, bugs). 3. Support and development costs now go up with each increase in complexity of the above two. There are more people you need to pay, more hardware you have to buy, you have more possible points of failure, more software to debug and a pile of ancient games you're now stuck supporting long past their end of life, all for a dubious 'value' that realistically the vast majority of your consumers are going to ignore, or treat it as a curiosity. And you end up having to deal with somebody's mother on a Twitter tirade who finds a copy of Atlantis from the PS at a garage sale and wants it to work on their new PS5 so their toddler can play a game. 4. Margins are already slim on consoles, sometimes sold at a loss so the company can get them into as many peoples hands as possible on a bet they'll make up for that on the games. They need to show a profit or they go under. The money earned from the sale of those old games went bye-bye long ago, either in profits or development of new systems and new games. The added cost and risk don't make sense for the limited value the functionality is going to offer. It makes more sense to redevelop or remaster the popular games and sell them for a nominal fee for the people that are serious to about wanting to play it. They get a little money back to support the development and they can tighten their support focus considerably which makes for a much stronger product and a better experience for the consumer (ie. you and me).",
"They do this on purpose because they have something on the system called Playstation Now, which requires you to sign up for a monthly subscription in order to use it. It’s about making money, plain and simple.",
"They can, Sony just doesn't let you via software lock. They want you to pay for Playstation now"
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mrkerb | how do u pump water above 10 meters? | I have understood that 10 meters of height u create a perfect void, then how the machines can extract water from 150 meters ?? Sorry for my english, spanish is my mother language | Physics | explainlikeimfive | {
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"Two possible ways, 1) for large amounts of water you don't \"suck\" it from the top, you push it from the bottom. 2) for very small amounts of water you can use wicking where the water uses adhesion to travel up a rope or fiber."
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mrkg7z | What happens to the brain after a tumor is removed? Does the brain regenerate the lost space/damaged functions? | Biology | explainlikeimfive | {
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"No there is an empty hole where the brain matter was. Sometimes new paths can be formed but alot of times function and ability can be lost. Source: ex wife had a brain tumor that was removed and had to go for countless followup mris.",
"The brain does not regenerate, as the neuron cells that make it up do not multiply after a certain age. The remaining cells may create new connections to the surrounding cells, but those connections (called dentrites, who look like tree branches) do not go far. But function depends on the area that the tumor was located, besides the age of the person. The younger the brain, the easier it makes new connections to repurpose the functions of the lost area, as there are cases of young children having an entire half of the brain removed, with no significant problems to their mental development."
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mrkp30 | How does our skin keep our bones, organs etc. Inside us without tearing apart as we grow? | Biology | explainlikeimfive | {
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"The elasticity of the skin stretches and grows slowly over time as our bones expand and grow, as for it holding everything together, it’s the air pressure from the earths atmosphere that prevents our blood pressure from pushing outward too hard and making us explode (what happens in outer space without this air pressure, and why astronauts wear pressurized suits and also why airplanes are pressurized before elevating to heights with less air pressure, preventing headaches and loss of consciousness) Edit: Thanks for the award :3",
"Skin tears all the time. It can usually repair itself very well, though some women get \"stretch marks\" from rapid expansion during pregnancy. The tear-repair cycle it pretty fast, skin cells only live about 4 weeks.",
"Our body grows all at once, in a coordinated manner, so while our bones grow, the skin is also growing. Sometimes, when the hormones that makes us grow get in an overdrive (like in puberty, or when using hormone supplements) the skin may lag behind, which causes those dreaded stretch marks. Those stretch marks appear because the skin is made by many types of cells, some of them grant elasticity while others keep the strength and durability. So, the cells that are rich in fibers that hold the skin, while other cells dry up to make a hardened layer on top of those, outside of the body. When the body (here meaning bones and muscles) grow too quickly, the stretchy cells rich in fibers appear beneath the \"cracks\" in that hardened layer, like scars."
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mrks29 | In atom clocks, is Cesium used up to be refilled? | ELI5: In atom clocks, Cesium atoms used to calibrate an electronic oscillator, are they destroyed in the process? | Physics | explainlikeimfive | {
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"No, the atoms are not destroyed. Cesium-133 is the only kind of cesium that isn't unstable, so it will never go away by itself, and the measurement used to calibrate the second is something the atom already does all the time.",
"Cesium-133 is heated into a plasma. That plasma is turned into a beam of atoms. The atoms are in either state A or state B. They pass through a microwave resonator that flips them all to state B. After they leave the resonator, a magnet casts all atoms that are still in state A out of the stream. A detector counts the number of atoms it receives in state B, and a feedback loop tunes the resonator to the exact frequency that flips all the atoms to state B. For Cesium-133, that's precisely 9,192,631,770 oscillations per second."
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mrkuc0 | What is happening when water touches hot oil and why is there such a sudden movement in chemistry? | Chemistry | explainlikeimfive | {
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"There's no chemistry there, it's all physics. Oil is less dense than liquid water, so water will sink in oil. Boiling oil is much hotter than water's boiling point, so liquid water will quickly boil into steam. Creating steam underneath a bunch of hot oil is going to result in the steam quickly forcing it's way out of the oil, and causing a splash in the process.",
"The hot oil is well above 100c, so the water rapidly boils and turns to steam. The steam takes up a much greater volume so it displaces the hot oil above and around it, throwing the oil violently away.",
"Oil is lighter than water, so it likes to float to the top. Water boils at a lower temperature than oil, so that when it gets under the oil and against the hot pan, it turns into steam - an expanding gas."
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mrl3xz | Why will streaming services still suggest videos on their app that I have rejected 1000 times? | Technology | explainlikeimfive | {
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"As always, such algorithms are responding mainly to what has worked for them in the past, at least moreso than to top-down programming by their creators/owners. So, apparently on the 1001st time, other people have clicked.",
"It probably reevaluates the shows you have watched regularly and regenerates the list of shows you are likely to watch based on you previous views. There is no particular incentive not too show you something you rejected in the past, maybe another show will have changed your interest in the rejected show."
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mrlv3f | Why do we need so many different types of toothpaste. like whitening, cavity protection, and sensitivity. Why can’t 1 tooth paste do all of the above? | Biology | explainlikeimfive | {
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"It's all marketing. It's the same as splitting up all the TV channels you want to watch so the not a single cable package has them all. It forces you to buy more product.",
"Because our teeth, even though they are basically the same, they are slightly different. There's people allergic to some components, with more porous teeth, sensitive gums, ... You name it. I, for instance, can't use whitening toothpaste. It's too harsh on my teeth. But many are made of the same ingredients, just marketed differently."
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mrm7h4 | How Does Exercising a Vaccinated Arm Reduce Pain? | Biology | explainlikeimfive | {
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"text": [
"Vaccinations are injected inside the muscle, the fluid is pushing the fibers apart. This stretching of the fibers is the primary cause of the pain. Exercising the arm helps to push the fluid away from the initial site putting each muscle fiber under less stress. It also helps to increase the rate of absorption so that the muscle fibers are not displaced for as long."
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mrmo7y | Why Do Derivatives Matter? | As a calculus student, I’ve learned how to calculate derivatives and how they are the slope of the tangent line to a point on a graph. What my teachers have never explained, however, is why exactly derivatives matter? What are we doing with them? Why do we calculate them? (Mind you: I have extremely limited knowledge of physics, which is probably why I don’t know/can’t understand this) | Mathematics | explainlikeimfive | {
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"Derivatives are used all over science and engineering fields, a derivative measures how some variable changes with respect to another. For example velocity is the derivative of position with respect to time, and acceleration is the derivative of velocity with respect to time.",
"Derivatives are, basically, the rate at which something changes. For example, with covid, the daily new number of cases is the derivative of the cumulated number of cases. Whether this is high or low gives you information on how fast the disease is progressing. Same with daily change of people in hospital, which is kind of the derivative of the number of people currently hospitalized. If it's higher than zero, you have a positive rate and the disease is progressing. Understanding exponential functions, and their derivatives, is key to understand the dynamics of the epidemic, even for a laymen. It lets you understand why the situation progresses so fast between under control, and out of it. For a road, the derivative of the altitude with respect to the horizontal distance is the grade of the slope. This value must be within certain limits to be suitable for traffic. For an object, the derivative of the position with respect to time is its speed. The derivative of speed with respect to time is acceleration. This is particularly important in physics because acceleration is the known quantity, as it matches \"forces\" applied to the object (e.g. when in free fall, your acceleration is constant, due to gravity). Then, by applying the reverse relationship (called integration), you can compute where the object will be based on what forces are applied to it. For a layman, understanding the concept is mostly useful when looking at a graph, in particular understanding the relationship between graph showing rate of change of a value, versus a graph showing the value itself. For people going into scientific field, it's mostly useful because for so many quantities in life, their rate of change will be influenced by their current value. In other word, you can write equations that link functions and their derivatives. This is used to model exponential growth of bacterias or epidemic (e.g. the more bacterias you have, the more new bacterias they can create, which drives their growth rate), but also model electric and magnetic fields, any type of wave (oceanic, sound, light, how an antenna works, etc), and so many other models in physics. These equations, that link a function to the derivative of the function are called \"differential equations\", and are a fundamental tool for creating models and doing computations. These equations are more or less the reason why you learn about the sin and cos functions, the exp function, and even polynomial functions like x\\^n : these functions are used in many contexts because they are common solutions of differential equations."
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mrn8ej | Why do some screens on electronics capitalize all the letters except for the first one? | Like, a little screen that says “rEADY” on an oven. It happens a lot on alarm clock screens, or that kind of thing. I saw it in Better Call Saul when he’s taking Cinnabon’s out of the oven and I realized I’ve seen it a lot before. I have a picture but it’s not allowed to post here. | Technology | explainlikeimfive | {
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"It's not that they're capitalizing the first letter in particular... it's just that they're very limited insofar as how they can shape letters. They're really only meant for numbers. If you look closely at that type of display, it's made up of a bunch of lights in the shape of bars in very specific conditions, and a bar can only be turned on or off: - | | - | | _ So the only way they can form the letter R is in lowercase. If they tried to make the closest shape to an uppercase R it would just be an A. This type of display is called a [\"seven segment\" display]( URL_0 ), because it's made up of seven bars. For something that can do letters better, they would be better off using a fourteen- or [sixteen-segment display]( URL_1 ). Those have more lines, including diagonal ones, to allow them to shape letters much better."
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mrnyrt | How does a jeweller tell whether a gemstone is real or fake? | Other | explainlikeimfive | {
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"text": [
"It depends on the gem in question. Diamonds for example are REALLY good conductors of heat. Absurdly good compared to most other things that look like diamonds. So cheap \"diamond testers\" just try to measure that property. However there because there is one diamond look-alike that will fail the heat conductivity test (Moissanite), so better (more expensive) diamond testers use electrical conductivity to account for that.",
"Crystallography. Each type of gemstone will scatter light in a characteristic fashion. So they shine a light and see if the gem deflects the light in the proper way."
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mro5un | How can a planet survive so close to a blckhole where one hour spent on it is equal to seven years on earth? | Physics | explainlikeimfive | {
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"text": [
"It's unlikely that any such planet actually exists. There'd be no plausible mechanism for it to form there, and that close to a black hole orbits are quite short-lived. It's not impossible in principle, in the sense that a planet could physically hold together in such a position if the black hole were large enough, but *Interstellar* is taking some liberties with actual cosmology there."
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mro948 | What is depreciation recapture when you sell a home? | I was just reading [this thread]( URL_0 ) and people were advising against this person selling the house because they would have to pay depreciation recapture. What is that? I read a couple of articles trying to explain depreciation recapture, including one from the IRS, and I am probably more confused than I was before. The phrasing they use is above my head and I simply cannot follow it. Please explain to me as if I were actually five years old! | Economics | explainlikeimfive | {
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"A business pays tax based on its profits. So, you take the money gained, subtract the money lost, and what's left is the profit the business needs to pay taxes on. But sometimes, there are non-obvious ways of losing money. One is depreciation. Let's say you are company with some equipment, like a backhoe. Let's say the backhoe is worth $50,000. But, over time, the backhoe gets worn down. It gets rustier, parts fail, etc. Even if you maintain it well, it won't last forever. Let's say a typical backhoe lasts 10 years before it's junk. So, every year, the backhoe's value drops by 10%, or $5,000. So, when calculating how much money your business made each year, you are allowed to subtract $5,000 because that's how much the value of your backhoe decreased. Subtracting this makes your profit smaller, and thus you pay less taxes. Let's say after 5 years, you decide to sell the backhoe. The backhoe originally cost $50,000, and you've been telling the IRS that its value has been going down by $5,000 each year for 5 years, so that means the backhoe should now be worth $25,000. But, maybe you took good care of it, and find the right buyer, and you manage to sell it for $35,000. Now the IRS is like \"Hey, we've been giving you tax breaks assuming you've lost $25,000, but you really only lost $15,000. You shouldn't have gotten such big tax breaks!\" So you are required to make up the difference, and pay taxes like it only depreciated $15,000 (because that's what actually happened). So, in the linked case, the guy has been paying reduced taxes because the building he owned for business has been going down in value. However, if he sells it and it hasn't actually gone down in value, he'll have to pay those taxes he avoided previously, and that top comment is reminding him of this."
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mro9in | How are there only 7 days remaining to apply to be a moderator for? | Hi Everyone, **Applications will be closing on April 22nd, 2021** ELI5 is looking for new moderators. There is no pay. You can expect people to be rude to you. People will blame you personally for actions you take that are entirely in line with the subreddit rules. There is no personal glory, and you can't use your position to cross promote yourself, your personal projects, or your other subreddits. The only redeeming quality is that get help the community out, as a whole. If that sounds like a position you're interested in, we'd love to hear from you. Fill out this form: [ URL_0 ]( URL_2 ) If you have any questions before you apply, please put them in this thread. We don't know what kind of demand we'll have, so we can't promise an individual response for every applicant. I'll also use this thread as a brief opportunity to plug [/r/ideasforeli5]( URL_1 ), where any ideas for eli5 are presented directly to the moderators and for public discussion. (Obviously Rule 3 doesn't apply in this thread, the only real rules are try to stay mostly on topic and Rule 1 is never waived, so be nice!) Thank you | Other | explainlikeimfive | {
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"> There is no personal glory, and you can't use your position to cross promote yourself, your personal projects, or your other subreddits. > I'll also use this thread as a brief opportunity to plug /r/ideasforeli5, Ah, that makes sense.",
"Best of luck to whoever gets chosen. Seems like that can be very stressful."
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mrojby | Why does your mouth water when you’re about to vomit? | Biology | explainlikeimfive | {
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"text": [
"Your vomit contains really harsh acid. Your saliva can help to protect your mouth from this by basically forming a layer between your skin and the acid. As far as how it knows, your stomach has a ton of sensors in it that tell your brain something is wrong. As the brain gets a stronger and stronger signal it starts prepping the body (deep breaths, increased saliva, tensing of the abs, closing of the wind pipe). Eventually the signal crosses a threshold and you vomit."
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mroyg7 | What does it mean to have a housing market bubble? And what are the potential consequences of not addressing it? For context, take Canada's current market. | Economics | explainlikeimfive | {
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"A bubble first occurs when an asset (stocks/houses/gold e.t.c) starts to become more valuable. People see the trend in the value going up, so they want to invest in it. Investing is the simple act of buying the asset, holding it for a while, and then selling it once the value has increased. However the demand for people trying to buy the asset as an investment pushes the price up, which makes it a more attractive investment and up and up the price goes in a positive feedback loop. The issue is, eventually the price might stop going up. With houses, for example, there literally becomes a point when nobody can afford them. At that point, all the people invested try to sell their asset since there's no more money to be made. This causes the price to plummet incredibly fast since the market gets flooded with people trying to sell their asset before they lose money on it. Why is this an issue? Firstly, lots of people can lose huge amounts of money very fast. Money that was perhaps going to be a retirement fund, or a college fund. However, there's a particular issue with houses, and that is that a lot of houses are mortgaged, and you can really easily end up in a negative equity situation. This is where the outstanding amount on the mortgage is more than the value of the house. So now, not only have you lost a lot of money, but you can't move house because you can't sell your house for enough to pay off the loan. If you're on a repayment mortgage (where every month you pay off some of the mortgage and pay some interest), then while it sucks - financially its pretty similar to renting (except you can't move). However if you purchased a house as an investment on an interest only basis (this is a mortgage where only you pay the interest on the amount borrowed, and after x years you need to pay off the mortgage as a lump sum), then when the mortgage term expires you're screwed! Suddenly you owe a lump sum more than the value of the house. A lot of people may have to declare bankruptcy. Because of the sheer value of the houses, a large number of people declaring bankruptcy on large loans can have serious negative consequences on the economy. Edit: Houses are a bit funny, because in many ways they are bubble resistant. You can't really buy fractional houses, so you have to save/borrow the full amount before hand. This dampens the rate at which they can increase in value. Also, ultimately a lot of people just want to own their own home, and aren't in a rush to sell it even if financially that's the prudent thing to do. A house has an intrinsic value as somewhere to live and some land, and often buying costs the same or less than renting. So there is a genuine and significant demand for houses not as investments. However its entirety possible for the housing market to crash, as it has historically in various places. If you look at something like bitcoin, that's a classic bubble - it only has such a high value because other people are buying into it, and that's why the price is so volatile.",
"It means that houses are extremely overvalued and that it's only a matter of time before some factor causes prices to come crashing down. This is referred to as the bubble \"bursting\"."
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mrp8kv | How are "synthetic" versions of chemicals made? | I was looking at a wikipedia page about a particular chemical and it said something to the effect of "this was originally extracted from a fungus, but can now be made synthetically". What does that actually mean? I can conceptualise the process of extracting chemicals from organic materials, but when something is created synthetically the chemists do...what exactly? | Chemistry | explainlikeimfive | {
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"Consider a nice simple chemical - ethanol. We've known for thousands of years how to produce it biologically, by fermenting stuff, but that is what we call a batch process - you make up a big vessel of starter material, let it do it's thing, extract what you want, clean it out, distill etc. Not as fast as it could be. Instead, by knowledge of chemistry, we realised that we could produce the same ethanol by a synthetic route - hydration of ethene, a product from crude oil, as a continuous process - ingredients come in, react and come out without pausing at high speed and high purity.",
"take a bunch of reagents (starting material that’s similar to the final product) and mix them/sometimes subject them to specific conditions, the reagents will arrange themselves to match the end product’s exact chemical makeup. I’m a chem student so that’s probably a terrible way to explain it, someone will do a better job LOL",
"Chemists don't usually make things all the way from their constituent elements but use off the shelf chemicals that are made from other chemicals that are made from .... that are made from things that are or can be made from simple components. Ammonia is made from nitrogen in the atmosphere and hydrogen which can come from various sources. Salt water can be converted into sodium hydroxide and chlorine by electrical current. Sulfuric acid in steps from burning sulfur. A lot of organic materials are derived from the chemicals in crude oil because that is an easy source but those could be produced from more basic chemicals, although taking much more time and expense."
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mrp8zk | Why can't water burn? | Chemistry | explainlikeimfive | {
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"It doesn't burn because it already has. What we call burning is actually just a chemical reaction where something reacts with oxygen. Energy is released in the progress of burning which means that the materials left after something is burned are more stable than they were before burning and typically don't burn a second time. Water is basically burnt hydrogen as it's molecules have two hydrogen atoms bonded with an oxygen atom. Burnt hydrogen (water) doesn't like to burn again. To make something that has already been burned burnable again, you need to put energy into it to break the bonds between oxygen and some other atoms. In the case of water, you can force electricity through it which turns the water back to hydrogen and oxygen gases that can be burnt again. Edit: Fixed a typo and added last paragraph.",
"\"Burning\" means reacting with oxygen in the presence of heat. Water is a stable molecule - two hydrogen atoms and one oxygen atom. It can't react with oxygen, because it already has all the oxygen it needs."
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mrpky2 | How does frozen food sometimes “taste like a freezer”? | Chemistry | explainlikeimfive | {
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"text": [
"Freezer burn is a condition that occurs when frozen food has been damaged by dehydration and oxidation, due to air reaching the food. It is generally caused by food not being securely wrapped in air-tight packaging. Food is still safe to eat though but usually has that aftertaste you're talking about."
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mrplki | This might be stupid, but is sound louder on planets with thicker atmospheres than earth’s because there are more air molecules that carry the sound vibrations? If so, would it be vice versa for planets with thinner atmospheres than earth’s? | Earth Science | explainlikeimfive | {
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"text": [
"The amount of energy in the sound waves and therefore how loud the sound is remains the same no matter what the sound travels through. Different materials and different pressures does cause different impedances but this only matters when transfering the sound between materials with different impedance and not how loud the sounds are. What you do get with different pressures however is how loud the maximum volume can be. Sound is waves of varying pressure so it is possible that a sound wave creates vacuum or at least very close to a vacuum. And since you can not create pressures lower then vacuum the volume of the sound is sort of capped. This is the same thing that happens when you max out a microphone or speaker and you start getting that ugly cracking sound. You can hear the exact same sound during rocket launches when the sound generated by the rockets gets above what the pressures on Earth is able to carry. And with a lower pressure this would happen at lower volumes. For example you are able to carry human voices and similar sounds in the Martian atmosphere however and louder sounds like a hammer hitting a rock will sound muffled and broken because there is not enough pressure in the atmosphere to carry the sound.",
"Not exactly. The sounds will be higher pitched as the density decreases. You can also more efficiently impart energy into the air. For the same amount of energy actually imparted into the air the level of sound will be the same."
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mrqnxb | Why is it easier and faster to blink than it is to wink? | Biology | explainlikeimfive | {
"a_id": [
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"guny47w"
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"text": [
"Because blinking is an involuntary function of the body like breathing. When your body is programmed to do something automatically, it usually does it really well. Also you’re probably just not used to winking, if you practice it enough it will eventually become effortless to do so. Kinda uncool to practice looking cool but cool people do it all the time.",
"You instinctively blink on a near constant basis, so your muscle memory is on point. You've probably blinked like 2-5 times reading this so far and you didn't notice it. Now, we don't wink nearly as often as blinking, and we sure as heck don't do it naturally without thinking. So we have to physically put effort into the process. Therefore it's a lot harder for us to do compared to blinking."
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mrqpej | How do plants know they're in dirt? How are they able to know where to put down their roots? | Biology | explainlikeimfive | {
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"text": [
"Seeds that are dormant typically need to get wet in order for them to germinate. Once the coating around the seed (or seed coat... go figure) gets wet for a certain amount of time (depending on the species of plant this can be really quick or really long), a bunch of enzymes, hormones, and proteins get activated which signals the seed to begin germination. Soil / dirt is usually very moist. Even in the desert, eventually, there will be enough rain one day for any dormant seeds underneath the sand / soil / surface to begin the germination process. That's why it's recommended for gardeners to wet the topsoil once they plant new seeds / seedlings. The wet soil promotes growth! Now when it comes to their roots, the seed just uses gravity to determine the direction / orientation. If gravity is going down, that's where their roots will go. This is all controlled by different enzymes, hormones, and proteins.",
"Plants have a sense of gravitation (gravitropism), so the roots grow down and the green part up"
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mrr1an | If the Sahara desert used to be a jungle. Is there fossil fuels here? if not why | Earth Science | explainlikeimfive | {
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"text": [
"Having a bunch of vegetation in the past isn't enough. You need to 1) have a bunch of vegetation, 2) that gets buried and sealed in before it rots, 3) with a porous rock that can hold the oil, 4) with a sealed rock above that that can trap it. If any one of those things doesn't happen, you don't get an oil reservoir that we can actually recover fuel from. All that said, the Sahara has a ton of deposited limestone and other sedimentary rock so...maybe?",
"So the reason we have fossil fuels is that in the Carboniferous perious, from around 360 to around 300 million years ago, when trees first evolved, there wasn't anything that could eat them when they died, so they wouldnt decompose. So for roughly 50 million years, when trees died they just piled up, forming massively deep layers. This got covered up with clay and sediment and the weight of the rock and layers of trees compressed and slowly heated the trees without oxygen and they turned into fossil fuels, and the sediment above them turned to rock and we got the burried oil reserves that we find now. Sometime around 300 million years ago bacteria and fungi and later insects and termites evolved that could eat the trees, and so after that, no new fossil fuel reserves have been formed. Now there might be fossil fuels under the Sahara, that were formed during the carboniferous period, 300 million years ago. But the Sahara was a jungle only 6,000 years ago. All the trees that died rotted and were turned to dirt, and none of it was turned to fossil fuels."
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mrrqzb | Why are there ads on Cocomelon's YouTube channel? | Technology | explainlikeimfive | {
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"text": [
"You are allowed to show ads to kids, but they have to be kid friendly. I think YouTube got in trouble because they were showing targeted ads to kids and perhaps ads of a less than child friendly nature. YouTube is allowed to show non-target and child approved ads to children. If you think about, TV does this as well. When you watch a kid's channel, or child programming, they show commercials. However, the commercials are child friendly (usually they are toy commercials). You won't see too many liquor commercials or trailers for violent movies in the ads of a kid's show."
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mrrz4x | How did gameboys not only function in but actually need very bright external light in order to see the screen, but modern screens with built-in backlights are nearly impossible to use on bright sunny days? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Different technologies. The game it used reflected ambient light and filtered it through the crystal matrix; modern displays have a projected light from behind that gets filtered as it comes out towards your eyes. But not all displays are like that; eBook readers and my Garmin watch both work best with reflected ambient light.",
"The original Gameboy used what is called a [Transflective display]( URL_0 ). It has a regular LCD on top like most display today but on the backside, there is a layer that reflects light and let light through. It is like a two-way mirror but not specular have defused reflection like a white paper That makes it possible both to illuminate it from an external light source and from a backlight. A display that only uses back illumination is called a transmissive display, this is the common type. The advantage is that it works fin in direct sunlight and it will then use less power because no backlight is needed. The problem is that that if you do that the color will look a bit washed compare to a display that only is illuminated by a backlight. So unless you are it very bright sunlight a transmissive will look a lot better than a transflective display. Because the phone is mostly used out of direct sunlight they use a transflective display. n You can look at the difference the technology in [monochrome displays]( URL_3 ) and [color displays]( URL_2 ) and there is a quite clear difference. If you look at a [Gameboy display]( URL_1 ) it is quite clear that the display is not very good. There is not a lot of contrast in the display at all Translefective displays are used for applications where sunlight usage is a lot more important than good color reproduction. The monochrome variant is quite common and it what you see in for example wristwatches. I have a handheld Garmin Oregon 450 GPS with a color transflective display. It works perfectly in sunlight but the display looked washed out and I would not like to have it on my phone. You can compare it to the touch screen on the GPS. It has a resistive touch screen so it works by pressing anything to the screen so gloves are no limitation like on phones with a capacitive touch screen. It also works fins if it is wet and that is relevant for a device that is watertight and is used out when it rains The resistive is less precise and responsive. So I like the capacitive touch screen on the phone and the resistive touch screen on the GPS. & #x200B; So like almost everything else if there is one advantage there is often a disadvantage so you select the appropriate technology for the production. For a phone, it is a better color reproduction than it prioritized before usage in direct sunlight."
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mrsgvk | Does a battery weigh more when it’s completely charged vs discharged? | Technology | explainlikeimfive | {
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"Yes. Also interestingly, here's an easy way to test AA batteries for charge. If you drop a AA battery onto the flat (negative) end from a couple inches and it bounces, its dead. If it thuds, its charged.",
"Not in any meaningful way. A charged battery stores electricity in chemical bonds between atoms. The same atoms are left after it's discharged, they're just connected together in a different way. If you want to be really technical, energy has mass, E=mc^2. But the difference is so small it doesn't actually matter."
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mrshjd | housing/car bubble crashing? | What does it mean? What's this have to do with the 2008 recession? | Economics | explainlikeimfive | {
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"When you buy expensive things, you typically finance it. You'll put a fraction of the money as down payment (for houses it's an average of something like 7%) and pay interest on the rest that you've borrowed. When more people are buying than selling, prices rise in standard supply and demand economics - the price of houses rise. Lenders are competing for borrowers, so they get more competitive. 10% down, 5% down. 0% down. The interest rate for the borrowed percentage typically rises with the less money you contribute towards the purchase. Typically as you pay of a mortgage a significant amount that you pay each month pays interest on what you borrowed and a smaller part pays off towards what you borrowed - that last part is called premium. In simple terms, the more you can afford in interest, the more you can borrow, the bigger house you can get. Some people will get a mortgage where they only pay the interest. The amount borrowed is never reduced from premium payments. They believe that the value of the home will increase, they'll eventually sell, and they'll pocket the difference. Additionally, some mortgages have adjustable rates. You might owe 3% now, but that could move 0.15% every quarter up or down depending on the national average or whatever. Now, if buying suddenly stops - say, significant unemployment increase such as 2004 to 2008 impacts house purchase rates - house value drops. Those people paying only interest now can't sell their home for more than they bought it and also can't afford the difference. Bankrupt. Those people with adjustable rate mortgages - ARMs - could maybe afford 3% but can't afford the interest at 5.5%. On to of that, big banks were lying about the quality of the loans in loans bundles they're selling to other banks. These banks are getting stuck with dud loans after paying millions. Everything snowballs and major financial institutions go bankrupt, rippling across all sectors. These days, big banks *should be* far more wary, and many regulations put into place are still in effect to limit what happened in 08."
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mrtuxn | What is the difference between the types of radiation that cause cancer and the types of radiation used to treat cancer? | Other | explainlikeimfive | {
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"Below a certain intensity, ionizing radiation will damage your cells. Above a certain intensity, it will kill them. Damaged cells can mutate and become cancerous, which is why low-level, long-term irradiation from (for example) tanning beds or radioactive material poses such a threat. When radiation is used to treat cancer, it is actually being used to *kill* the cancerous cells in your body - they are living tissue, and can't multiply if they're dead. In this case, the radiation will be at a very high dose and directed to a very specific area so that it will cause as little damage to the surrounding healthy tissue as possible.",
"There is not much of a difference - it's the same type of energy being fed into your body. When they use it for medical treatment they tend to target specific parts of the body - if you have a tumor in your stomach somewhere then they're not gonna want to expose your legs and feet to radiation unnecessarily, to try to limit the area of damage. It is unfortunate but this also can cause damage to nearby parts of the body (skin and tissue damage, or even new cancer growths, but it's a risk they try to control).",
"Nothing is different about the radiation itself. The radiation is the same, but things like the intensity, and how targeted it is are different.",
"Radiation therapy uses x-rays, which are ionizing radiation thus increase risk of developing cancer. However, the risk is relatively low: 1. Radiation therapy is relatively brief, so overall there is little radiation outside the focused area, thus risk is not too high. 2. In the focused area, radiation is brief but intense. It is intense enough to kill cells, including healthy cells caught in the treatment area. Killing the healthy cells is actually good since it leaves them too dead to develop cancer. So, overall, we are talking about a low risk of cancer in the future, which is well worth not dying now to the cancer at hand.",
"First of all, you need to understand the basics of radiation. There are three main types: 1. Alpha particles 2. Beta particles 3. Gamma rays Alpha particles are just 2 protons and 2 neutrons. It is the same structure as the nucleus of a Helium atom (specifically Helium-4). This is the weakest of the radiation types and can be blocked by a sheet of paper, or even clothing and skin. It can really only harm you if it gets inside your body through inhalation or ingestion. Beta particles are simply high-energy electrons (or their anti-matter counterpart, positrons). They have a bit more energy than alpha particles and require a thin layer of lead or concrete to stop them. Gamma rays are high-energy photons... in other words, they are just light. Light starts to become ionizing once it gets into the ultraviolet range. Gamma rays are far more energetic. So much so that they would very likely pass through you as if you weren't even there. Very quickly, I will mention neutron radiation. Free neutrons are unstable and will decay in about 15 minutes. They are only produced by fission and fusion reactions. While they can be extremely harmful to us, the only way you would be exposed to them is by proximity to fission or fusion processes, in which case you've got much bigger problems than neutron radiation. Ok, so here's a fun little thought experiment--I will give you three cookies: one has a small quantity of alpha particles emitting substance baked inside, the second is made with beta particles, and the third is made with gamma rays. You have three options: eat the cookie, sit on the cookie, or throw the cookie out the window. BUT you can only use an option one time. So... what do you do? The correct answer is that you eat the cookie with gamma rays, sit on the cookie with alpha particles, and throw the beta particle cookie out the window. You see, just like a bullet, damage is done if your body absorbs the energy. So, if you eat the alpha particle cookie, you body will absorb 100% of that energy. If you eat the beta particle cookie, you will absorb about 50% of that energy (the rest will pass right through you). And the vast majority of gamma rays will exit your body as if you're not even there, so the energy absorption is very low. If you sit on the alpha particle cookie, you clothing and skin will block nearly 100% of the energy. With the beta particle cookie, however, your body will still absorb nearly 50% of the energy if you're sitting on it, so you want that one as far away from you as possible. As for radiation treatment, there are two general types: external and internet. External treatment uses high-energy photons in the form of x-rays (lower energy than gamma rays, so they will absorb a bit more into your body) which can be targeted to a specific tumor. However, as mention above, these high-energy photons will largely pass through the body without hitting anything, so you need a lot of them to get the job done. And, of course, they can and will damage any non-tumorous cells that are in the line of fire. For internal treatment, they identify which substances (usually some type of hormone) will bind to the cancer cells. Then, it's just a matter of mixing that substance with a small amount of a radioactive material that produces mostly alpha particles. Here again, other non-tumor cells will be destroyed in the process, but the goal is to destroy as many of the cancer cells while mitigating collateral damage to the the healthy cells. This also give you some insight into why the \"stage 4\" or metastasis phase of cancer is so often terminal. At the this point, the cancer cells have \"metastasized\" or spread throughout the body. If you were to try radiation treatment (or pretty much any other treatment) at this point, it would do more damage to the person than they could recover from, and still not get all of the cancer cells. I know this was pretty long, but hopefully it gives you a better understanding of radiation and how it works.",
"Radiation causes damage to DNA. There a genes that control the cell cycle and cell growth called oncogenes. If these genes get damaged, cells can keep dividing and dividing until you have a tumor. But most of the time radiation will just kill a cell or have no effect. If you get lots of radiation exposure over time, the chance of it damaging an oncogene goes up, so that's how radiation causes cancer. However very intense focused radiation can be used to kill tumors because it is so damaging to cells.",
"* Radiation is just a mechanism of transferring energy through a medium. Your heater radiates heat. Your TV radiates visible light. Uranium radiates alpha particles. That's all radiation. * Ionising radiation describes the types of radiation that can damage biological structures like cells or DNA. * Cancer is a group of diseases caused by faulty DNA. Faulty in just the right way that it causes the cell to stop functioning properly and replicate uncontrollably. Ionising radiation is one possible cause for that, but there are other causes. * Radiation therapy is the use of ionising radiation to kill cancer cells, with specific targeting and dosage to avoid damaging surrounding healthy cells. * It's possible that the same type of radiation that caused the cancer could be used to treat it, but that would purely be a coincidence. The fact that there are different causes of cancer, and different methods of treatment, make it fairly unlikely from a mathematical standpoint. * Also it's rarely as simple as getting cancer from one specific source or event. Usually it's a combination of multiple risk factors over many years, and using statistical probability to infer the primary cause. eg. we know that statistically, smoking increases the chance of lung cancer, but it's impossible to look at a specific case of lung cancer and definitively prove it was caused by smoking and nothing else. That's how cigarette companies got away with it for so long."
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mruc8l | How come humans are disgusted by the idea of eating food that's already been chewed by someone else but animals have no problem with it? | Biology | explainlikeimfive | {
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"We are aware that other humans can contain diseases that can be transmitted through saliva. Moreover, we prefer to eat well-presented food from a young age, so seeing something chewed can be unappetizing. For some people, this is also true when they see their own chewed food.",
"Because most humans have the luxury of turning their nose up at a pre-masticated meal. Animals know food is food and the best food is the food that’s right in front of you nom nom nom",
"Humans are aware of the bacteria/viruses that inhabit our mouths. Humans are also distrusting of how clean someone else's mouth may be.",
"Because we know about germs. And it's taught to us at from a young age not to eat after other people.",
"Disgust is learned emotion - we pick it up from our parents as toddlers. Toddlers - before their parents or guardians teach them better - are quite happy picking up and eating food off the ground, or eating snails from the garden or food that someone has taken a bite out of or picking food literally out of someone else's mouth.",
"Going out on a limb here... Disgust seems to be learned. If you learn / think something is disgusting, you will react disgusted when exposed to it. People can also unlearn or at least manage this emotion, otherwise young parents that absolutely cannot stand poo, would seriously struggle to care for their baby. It's also has a culture / society / group aspect to it, in that there may well be a group of people that would consider chewing food for, say an elderly person without teeth, perfectly acceptable, whilst for anyone you know, it may be totally disgusting."
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mrue2c | Why do turtles dance when sprayed with water? | Biology | explainlikeimfive | {
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"I just recently learned that turtles and tortoises have nerve endings in their shells. They can feel water and brushes on their shells and enjoy it a lot.",
"Turtles can feel their shells. You pouring water on them is both cooling them off in a hot environment which can be nice, but your also scratching their hard to reach areas. Most turtles usually don't like to be touched, but water is usually an exception for them."
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mrv7i7 | What's the difference between a mirror and a white surface if both reflect all light? | Physics | explainlikeimfive | {
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"Think about bouncing a rubber bouncy ball. If you bounce it on a smooth gymnasium floor, it is easy to bounce and catch because it bounces predictably. Now think about bouncing it on a parking lot. When it hits a small stone or a crack it bounce in an unpredictable way but it still bounces. A mirror bounce the light back in the same way it comes in - this is the smooth predictable bounce. White things bounce the light like a rough parking lot - the scattered light is out of order and no longer looks like an image."
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mrvouj | When getting immunized, how does the needle go through the skin so easily and painlessly? | This might be just me, this excludes the pain afterwards. | Biology | explainlikeimfive | {
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"Partially because it’s super sharp and partially because it’s really small. When it’s sharp, it slices a small hole rather than brute forcing one. That’s why mosquito bites don’t feel like somebody is stabbing you.",
"The needles are tiny, very sharp, and also cut at an angle like this |/ which allows them to puncture the skin smoothly, and ideally without hitting many nerve endings."
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mrvqr4 | -How can lava exist underwater? | Earth Science | explainlikeimfive | {
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"It's very hot. Of course the water around it will \"try\" to cool it down, but it will almost immediately vaporize, and leave the lava as liquid as it would be in air. Eventually it will cool down, but that process takes a lot of time."
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mrwwtn | Why do cells not get smaller when they divide? | Biology | explainlikeimfive | {
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"Well, they technically do, and they technically don’t. Before a cell splits, it produces everything it would need for a new cell. It definitely causes it to become larger. When it divides, it goes from double size to normal size again."
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mrxebv | why do a lot of people hate communists? | Other | explainlikeimfive | {
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"Since this is an ELI5, let’s see if this does the trick: Once upon a time there were two rich boys, one of them liked to look after others, the other one liked to look after himself. Soon enough the boy that looked after all the others got pretty popular, although every time it became harder and harder to look after everyone, and he started to think about how it would be easier if everyone just did as he said. The other boy, well he got richer, and his life looked so good that others around him benefitted from his wealth, making them also think that his was the way to go. At some point they couldn’t stop talking about how their way was better, and about how much the other was doing things wrong. Everyone started talking about it too. Tragically, the boy that liked to help others left, and nobody really picked up the work. It didn’t help that the other boy helped himself to whatever he wanted, whether he was “allowed” to have it or not. Eventually their friends developed their own version of what they knew, still thinking that the other was wrong. Some of the more enlightened of their friends decided not all was bad from the other side and merged some ideas. To this day, everyone is still talking about why the boy’s idea of helping everyone failed, but can’t really talk louder than the other boy who is still screaming about how his way is better, and more proactively sabotaging any attempt to diminish how much wealth he can take. Long story short: it’s because the propaganda machine that started trying to discredit communism and socialism is still very much running strong. Just in case anyone gets the idea that capitalists aren’t entitled to hoard all the wealth.",
"Especially in the US you can thank Joseph McCarthy and his [McCarthyism]( URL_0 ). He basically accused everyone critical of him to be a communist, using a lot of the methods he criticized in the government of the USSR (domestic espionage, secret blacklists, …) He was also very opposed to anything seen as \"Socialist\" like public health care, including the Polio vaccine or fluoridated water.",
"Well, you answered your own question: history-lessons... Those are given from the Western-perspective and communism isn't seen as a favorable theory. So people in the West (like me, I live in the Netherlands) grow up with a certain view on communism and if you don't gather more information yourself, that view will stick with you in the future. In the same way that Western conquerers from the past, creating colonies on other continents are seen as heroes. Whereas one could argue in the current timeframe that it was actually not that nice...",
"Communism gives the power to very few people who are then in control of the remaining population, taking decisions that would further the good of the 'community' or country. This leads to disregard for individuals, especially minorities, since everyone is supposed to follow the same status que. The oppression and the centralization of power historically lead to corruption and fascists tendencies, benefitting almost no one. That is why it's unpopular ^^. It is a neat idea, but impossible due to human nature. ( Too much power in one place with no checks and balances).",
"Someone needs to come in here and actually explain what the people who both understand communism and hate communism think. I’m not one of those people because I don’t know that much about communism. From what I have gathered, communism, and the theories of Marxism that communism follows, is essentially a theory that’s good on paper, but everybody who’s tried to implement it has ended up with a lot of death and suffering. So the people that hate it don’t want their lives, or their society in general, to have the death and suffering that communist places had. People who don’t want communism for these reasons may feel hate towards people that are communist."
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mrxgo8 | Why is space cold if there's no matter in it? | Physics | explainlikeimfive | {
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"In reality there isn't such a thing as \"cold\" just less hot. (Similar to how black is just no light) Heat is the movement of atoms and molecules. So if you have no matter, you can't have any heat.",
"Most answers here are plain wrong. Space being cold is entirely unrelated to it being mostly empty. Temperature is, informally, the average speed the molecules move at; the amount of said molecules is irrelevant. So, why is space cold? The main reason is that it is not; humans and the things around us are just pretty hot. The average temperature of the universe is much lower than Earth or the Sun might suggest. Those two are just exceptions, which we rely on to survive. But lets also talk about what happens if you would be dropped into space without protection from temperature (while somehow still being able to breath and not in vacuum). First, this depends on where \"space\" is supposed to be here: if I drop you \"near\" the sun in astronomical terms, lets say around Earth's orbit, then one side of you will actually heat up quite a bit due to the Sun. The other one will slowly cool down due to thermal radiation leaving your body (this also happens on the solar side of you, but is totally overwhelmed by the sun). In short, one side gets cooked, the other frozen, but slowly. If you are far away from the sun (say, Pluto), then both sides do not get much sunlight and cool the same. If somehow you have no protection from vacuum on your skin (yet do not die from lack of breathing), then another effect kicks in and cools you down much more rapidly: water evaporating. Just like wet skin or clothes on a hot day, water cools you when evaporating. However, in vacuum, water starts boiling already at 0°C! Thus your surface is more like a hot plate rather than just a bit warm, relatively speaking. Evaporation is extremely rapid under those conditions, untill the water gets down to 0°C (it actually starts freezing when left in vacuum, even in a chamber on earth that normally has room temperature). If you had a drop of water (or e.g. blood or any other liquid that mostly consists of it) on your skin, it would even look like water on your oven. But note that your skin substitutes for some pressure, i.e. holding blood and sweat in, thus making your insides not boil, only liquids that leave your body.",
"The movie-depiction of \"everything freezing to death in space\" in a second is not true. And yes, space aint cold - exactly because its so empty. So, Overheating is a far bigger issuein space, because that vaccum cant transmit heat easily, you cant get rid of the heat (on spacestations / -suits) energy easily.",
"Any matter in space will radiate away it's heat energy until it reaches a temperature a bit above absolute zero. So space isn't cold, it's just that the things in space tend to become cold over time.",
"I can’t give a thorough answer, but matter holds and conducts heat, which is why you can feel heat. For instance, part of the reason that earth is warm is because of the greenhouse gases creating a sort of bubble around earth that keeps the heat bouncing around inside, creating our atmosphere. Beyond that barrier everything is different and it gets very cold. Everything is open and flows freely. And back to the first thing, matter is what holds heat or energy. That’s why when the air is more humid, there is more water in there, it can feel hotter than it really is, because the water is such a great conductor of the heat. Likewise when it’s cold, which is why you sweat to cool off (as the water/sweat evaporates off you it pulls the energy with it). I’m sorry this is a very complicated answer, I hope someone else can provide a better one",
"Because you can expand the definition of \"cold\" and \"hot\" to include heat radiation. If you put something in space, it will radiate away its heat after a while, until it has a certain temperature that's very cold. You can do this at home easily: hold the back of your hand close to a hot cup of tea without touching it: you will feal the warmth. This warmth is not transmitted through the air, but through infrared radiation. Now take a chilled drink and hold the back of your hand close to it. You will feel the coldness of it. This is also not the air, but the \"absence\" of infrared radation coming from the drink, as well as the infrared radiation from your hand that takes away the heat. Since there's nothing in space to radiate heat onto you, you will radiate your heat away and become very very cold.",
"It's cold *because* there's very little matter to hold onto energy. Cold is just a lack of thermal energy.",
"Yea its a case of lack of molecules (hence space) heat dosnt transfer through a vacuum very well In the sunlight temps scorch in shaded non lit areas cold. Ironically the space station has more of a cooling problem than heating as the heat generated from the astronauts and electronics dosnt dissipate very well and large heat sinks are required to dissipate heat generated"
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mrxj4i | What is the neurology mechanism during drug intake ? | Chemistry | explainlikeimfive | {
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"That’s way too broad a question because different drugs have different mechanisms of acting on the body, but essentially drugs interact with endogenous (built in) signaling pathways in the body such as neurotransmitters and their receptors. To use one example, caffeine is shaped kind of like a neurotransmitter called adenosine that builds up throughout the day and acts on adenosine receptors to trigger sleepiness. Caffeine is shaped closely enough to fit in the receptors but not closely enough to actually activate them, so like a key that fits in the keyhole but can’t turn the lock, caffeine blocks adenosine from doing its thing, leading to us feeling more alert.",
"It really depends on the frug you're talking about. The addiction part is simply that it stimulates either the happiness receptors, or the receptors that launch the happiness molecule production. That causes your brain to get \"desensitized\" to the happiness molecule (either it gets used to \"too much\" of it, or it get used to be asked to produce it so regulary that it stop producing it as much as it used to for other things). Now, as I said, each drugs don't act in the same way than the others. THC and canabinoids activate 2 kinds of receptors that stimulate a lot of parts of your brain, including * the \"happiness molecule repection\" part of your brain making you feel temporary happy. * the memorization parts of your brain making it harder to remember stuff * the sensitivity parts of your brain making you feel numb LSD have a more funky effect. It connects sensory parts of your brain that shouldn't be connected (the vision and the hearing, the sensation and the taste,... that's why you have the cliché of people saying that they taste colours or things like that while they're high on LSD). So while your brain normally works like many \"tiny brains\", it now works like \"one giant brain\" which is not really normal nor good. It would also makes it harder to your brain to \"stop analysing\" things. Like, when you look at something, the raw picture is sent to an \"analysing\" part of your brain that will say \"okay, so two points and one line is a face\" making that :) seems like a smiling face. But on LSD, your brain overanalyse what it's exposed to and that cause the really colorfull fractal hallucination. Basically, your brain sees a face, and reanalyse it as a face, and reanalyse it as a face,... making you \"see\" multiple face, or a monstruous face, because your brain keeps analysing it over and over, making each details of the face more and more precise and big and excentric. Opioids makes the \"organ to brain pain transmission\" dull which is why they're used as painkillers. it also cause spasms in the sphincters."
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mrxvyh | Why did the BioNTech stock soar last year, but the Pfizer stock did not? | Economics | explainlikeimfive | {
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"BioNTech is much, much smaller than Pfizer, so the success of their vaccine increases their relative value far more than it did for Pfizer. BioNTech is also basically a startup, so their stock value is not based on earnings history but future earnings potential; the successful vaccine realizes a lot of that future potential."
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mryc56 | what are the differences between “ URL_0 ” and “ URL_1 ”? | Are there any advantages/disadvantages to using one over the other, or any functional differences between the two? | Technology | explainlikeimfive | {
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"\" URL_0 \" is a town. When you drive into town, someone asks where you're going. If you don't have a specific house in mind, then they send you to the town's default house, where they want all visitors to go. \" URL_0 /page\" is one specific house within that town. You're driving directly to that house because you know it's the one you want. \" URL_3 \" is a community within that town. When you drive into that smaller community, you're once again sent to the community's default house for visitors (which may be different than the town's default house). \" URL_2 \" is one specific house within that smaller community.",
"page. URL_0 and URL_0 are different *hostnames*. If you send messages to them, you could be talking to different computers, or the same computer. Depends on the DNS setup. The *path* (\"/page\") is how you ask that computer for different things among those it provides."
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mrypir | if all store bought bananas are clones, then how come they can vary so much in size? Some are absolutely huge whereas some are extremely tiny. If they are biological identical, shouldn’t they be of similar size? | Biology | explainlikeimfive | {
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"Take a set of identical twin humans (same DNA, like clones). Raise one with great food, comfy housing, regular exercise, and low stress. Raise the other one in a dark cage, feeding it a small plate once per day, never leaving the basement. It's guaranteed the well-reared twin ends up much taller and heavier than the famine twin. \"But they have the same genes, shouldn't they look and grow the same?\" But growth and development is the combination of genes *and environment*. In the same environment, yes they would! How does this apply to bananas? Different banana farms get different amounts of sun, of rain, of heat. They use different amounts of different fertilizers. They have different pests. Their growing seasons are of different lengths. Even within one farm (which are often on hills), one side of the field may be shadier or drier. One side of the *tree* may be shadier or drier. One side of *that single bunch* may be shadier or drier! All these factors and more affect how each banana lives up to its genetic \"potential\".",
"Environmental effects like sun exposure or humidity do play a huge role in how living beings develop.",
"Environmental factors, as others have said and explained. But also, the age at which they're harvested plays a part too. Leave em longer, they'll be bigger."
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mryqop | What makes a hard drive 'hard'? | Why would it be described like that? It's not like SSDs or optical media are particularly soft. | Technology | explainlikeimfive | {
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"Cause before you had floppy disks. Which, as the name inplies were floppy disks encased in a hard plastic box. Then came harddrives which are, you guessed it, harder disks.",
"What others have said it's basically right about floppy disks, however there is another factor... The actual recording media for \"floppy\" disks (12\" flexible all the way down to 3 1/4 hard shelled disks) was a thin plastic sheet. Hard disks use multiple metal disks. So, the actual physical disks inside were either flexible or solid.",
"Hard disk drives are hard when compared to floppy drives. Of course the floppy drives most people remember will be the 3 and 1⁄2-inch floppy disk which were encased in hard plastic. However the older 5 and 1⁄4 inch discs and even older 8 inch ones were indeed floppy and able to bend flex. In general it has little to do with the drives as you handle them but the disks insides. Floppys and similar had flexible disks while HDDs have hard platters inside them. If you ever opened up an old HDD you will have ended up with a broken drive and a cool magnet to play around with, but also some hard silvery looking disk that were stacked one over the other other inside the drive. These platters are what is meant when they say 'hard' compared to the floppy disc that you get when opening up the protective sleeve of a floppy disc."
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mryvnx | What muscles do we use when we force pee out faster? Are they the same in men and women? | Biology | explainlikeimfive | {
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"There are specific muscles around the bladder that is generally used. However a muscle needs leverage. So you can make them work better by increasing the pressure in your abdomen by using all the other muscles around your stomach. Even pushing down on your belly makes you pee faster. However some of these muscles help with breathing in a similar mechanism. So you may have to hold your breath to force the pee out.",
"Don’t know if it’s the same muscle, but women have the ability to stop their flow of pee pretty much immediately at any time, but most men have a much harder time.",
"Essentially, the detrusor (sp?) muscle that is connected to the bladder. When the bladder is being filled/full, the muscle is relaxed, and it can be engaged to put pressure on the bladder, and thus force the liquid out quicker. There may be more to it, but thats all I remember from Anatomy.",
"A few muscles, but particularly the detrusor (bladder muscle), the diaphragm (breathing muscles), and the abdominal wall muscles. Think of it this way - the more a balloon fills up with air, the faster and harder air leaves it. That's the bladder and the detrusor muscle. But what happens once it starts to deflate? The rate of air leaving the balloon slows down a bit. Increasing pelvic pressures by taking and holding a deep breath, as well as bearing down with the abdominal wall muscles (core) can increase the pressure in the bladder (squeezing the balloon). Strangely, we also have to relax the pelvic muscles to poop and pee. There is a form of urinary dysfunction in which someone finds it difficult to urinate but nothing is truly blocking urine, it's just that their pelvic muscles are so tight that they hamper the stream!"
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mrz1xl | Why should we have stored some spices and medicines in the dark? | Chemistry | explainlikeimfive | {
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"molecules that affect our body are usually very reactive molecule who are on a stable state only thanks to the fact that their \"less energic\" form requires a tiny push to be reached. That tiny push can come from heat, chemical reaction or light. That's why some alcohols, medecines and spices have to be kept in a dark and cold environment: so they don't get pushed to their less energic and unwanted form."
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mrz9tl | What does “carbon based life” actually mean? Are we made from carbon? | Biology | explainlikeimfive | {
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"biochemestry is based on carbon. In fact, a molecule is considered organic if there is an hydrogen linked to a carbon atom. Our whole biochemestry is based on a carbon structure (that allows linked atoms to be in a tetrahedric shape, a flat triangular shape or a linear shape, and up to a certain extent, it can also form hexagons and pentagons which gives really interesting chemical properties). There are no example of non-carbon based life IIRC, but theorically, nitrogen could have a similar role than carbon in a speculative biochemestry point of view. Silicion too, but it's unlikely as silicium is just a bigger carbon with, so it gets the advantages of carbon, but in a lesser extent. EDIT: ~~silicium~~ - > silicon",
"Pretty much, yep! The way atoms stay together is basically by holding hands. Carbon is able to hold hands with a lot of other atoms at the same time, which means you can make really complicated shapes with it! These complicated shapes are important for life. One reason is because they can hold a lot of energy. Carbohydrates - the stuff in bread, pasta etc - is able to give your body so much energy because it has lots of carbon in there making lots of connections. Those connections are what gives your body energy!",
"By mass, we're mainly made of oxygen, actually. This has implications for the long-term development of life like ours in the galaxy. But as to your actual question, carbon is the thing that makes up the central \"skeleton\" of the molecules that permit complex life as we know it- all the organic molecules are essentially frameworks of carbon atoms in various configurations with other stuff stuck to them providing specialist functions.",
"We are made of very complex molecules. Very few elements are able to make long chains of to make complex compounds of different sizes. Carbon is the element that allows us to have lots of different molecules of varying lengths, shapes and complexity."
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mrzoya | If eating fat slows down digestion, how come eating a lot of it causes diarrhea? | Biology | explainlikeimfive | {
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"Diarrhea is not so much the result of fast digestion. Its more of an “emergency flush out”. You dont digest very well if it comes out as diarrhea.",
"When you eat fat, your pancreas releases bile to help digest it. If you eat a huge amount of fat at once, you can give yourself pancreatitis. This is inflammation of the pancreas caused by the bile. Pancreatitis causes diarrhoea."
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mrzpdm | how can Homo sapiens and Neanderthal be different species but Neanderthal dna is common in modern day people | To my 5 year old knowledge I thought Neanderthals were different species but for us to have part of their dna that means they got jiggy together and created fertile off spring with Homo sapiens but when a donkey and a horse do it they make infertile offspring? Are we not like actual separate species? | Biology | explainlikeimfive | {
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"The way you are taught \"what is a species\" in school is a gross simplification In nature, organisms do not adhere to strict rules. The high school level 1 biology class definition of a species is sorta accurate for many animals, but there are many many exceptions. There are genuses that produce infertile hybrids, sure, but there's also things like \"ring species\" where geographically-adjacent species can each interbreed with their neighbor, but *not* the neighbor of their neighbor. And there are species in the process of diverging so there may be different populations that are becoming different sub-species Humans and Neanderthals have a lot of differences, but those differences did not extend to differences in reproduction.",
"Just like dogs are all members of the same species and yet the multiple breeds can procreate and create viable offspring. Neanderthal extinction would be the equivalent of specific breed’s extinction. Homo(sapien) Homo(neanderthalensis) Homo would be the genus which we share with them and others allowing us to mate with viable offspring being the product.",
"Modern Humans are Homo Sapiens Sapiens. Neanderthals were Homo Sapiens Neanderthalensis. We are basically subspecies of the same species, or more akin to the distinction between a wolf and a domesticated dog (possibly even between breeds of dogs)."
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mrzpu7 | In the context of programming, what does Return do? | I'm trying to pick up computer programming yet again, and I'm not really understanding the use of Return. What is it? How would you use it? | Technology | explainlikeimfive | {
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"It tells the thing that's interpreting or compiling your code that you want to exit the current function. If you just write 'return' that's all that will happen, but typically you can also follow this up with some values that you want the function to spit out, i.e. the output of the function. For instance, I could define this function (in python code): def PlusTwo(x): x+=2 return x And then if in a command terminal (or some other script/function) I say: \\ > y = PlusTwo(3) The resulting value of y will be 5. You'll often find return statements at the end of a function, but not necessarily. You can have different conditions under which you want the function to exit, with different outputs, and these might be found at different places in the function. However you nearly always find a return statement on the very last line of the function, because anything below that would be ignored. For instance, if I define a function like this: def PlusTwo(x): x+=2 return x x+=7 the last line will never actually be executed, and so this function still just adds 2 to the value of x. Some languages don't require return statements - you just have to specify in the function definition what variables are your output variables. And then whatever the values of those variables are when the function exits will be your output. MATLAB for instance works this way. But others, like C or python, do use return."
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ms0c41 | Why do bigger camera censors have more natural blur? | Technology | explainlikeimfive | {
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"It's more that there is a wider variety of lenses available on cameras that have large sensors, in particular lenses with large holes (apertures). Lenses with a large hole give the rays of light more opportunity to stray off course before they are focussed back onto the sensor. The stuff that isn't focussed is what causes the blur, ie they've got jumbled up with all the other rays of light. A small hole means all the rays of light go straight through and hit the sensor without much opportunity to mix and cause blur."
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ms158x | What are practical applications for prime numbers? | Mathematics | explainlikeimfive | {
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"Large prime numbers are essential to encryption, especially encrypted messages and information transmitted over the internet. Having two very large primes multiplied together is the basis of encryption keys. Computers struggle with prime factorization for very large numbers, and once those numbers reach a certain size, it takes even the most powerful computers years and years and years to work through a prime factorization algorithm in order to discover the basis of the encryption key being used.",
"Others have talked about computers, but prime numbers are practical in the natural world as well. Predators in nature tend to have population booms in regular cycles (between 2 to 10 years, depending on the predator). This means if you are prey looking to avoid getting eaten by a predator, you want your own population cycles to be out of sync with any predator's cycle. While it's impossible to avoid another's cycle completely, you can minimize it by implementing prime numbers. Cicada's are famous for having cycles based on prime numbers (13 and 17, specifically). Why is this helpful? Well, as stated above, most predators have a population boom every 2 - 10 years. So if you are a predator that has a boom every 2 years, then you boom on years 2, 4, 6, 8, 10, 12, etc... So let's say a brood of cicada's came about every 12 years. Well, they'd be susceptible to predators who boom every 2 years (since year 12 is one of their boom years). They'd also be susceptible to predators who boom every 3 years (3, 6, 9, 12...), 4 years (4, 8, 12...), and 6 years (6, 12...). This is because 12 is divisible by those intervals (2, 3, 4, and 6). So by having a prime number as their interval, they divide with no other number and will only coincide with other predators on long intervals. For example, a 13-year cicada will only arise alongside a 2-year predator every 26 years! (2x13) and won't coincide with any of the other predator's (because 26 is only divisible by 2 and 13).",
"Others have covered encryption, but your car likely has a prime number of lug nuts (5 or perhaps 7) to reduce vibration harmonics. Cars used 4 before, and those harmonics caused problems so today it's only low-speed cars with small wheels that go that way.",
"I will expand and clarify a bit about how prime numbers are used in encryption. The process of encrypting a message uses a key and some fancy math to turn that message into what looks like a bunch of random junk. However, the process can be reversed if the key is used. Without a key, you can still make guesses, as if you were trying every combination on a lock. Now imagine if you could make \"progress\" towards the right answer. Say the first digit of the combo lock clicked when you put it in the 4 position. Now you know the first digit is 4 and you can move on and solve the rest more easily. That's what encryption would look like if we didn't use prime numbers. Hackers could make progress towards solving the equation be using the factors of the numbers involved. We don't want that! We want hackers to have as much trouble as possible guessing our encryption keys. So essentially, prime numbers can be useful because of how hard they can be to find!",
"Your information is stored, at some point, on a computer server. That computer server almost certainly stores it on a thing called a RAID array. This is a bunch of disks and SSDs cleverly built so that if any one drive fails, the computer keeps on running and no data is lost. You just pop out the bad drive, pop in a new one, and it carries on running. These are used in pretty much every server, every business, every datacenter, every cloud service, anything that holds data. Even people's home media libraries are often stored on a RAID. RAID works because of clever mathematics that rely on a thing called a Galois field. To ELI5, this is just a way to store - let's say there are four drives - three numbers on four drives such that if any drive is lost you ALWAYS know what all three numbers were. Say you want to store the numbers 2, 4 and 6. I could do: Disk A: 2 Disk B: 4 Disk C: 6 Disk D: 12 (i.e. 2+4+6). Now take out any one of A, B, C or D. I can tell you what number is missing. B is broken? Then I know two of the numbers that survived are 2 and 6, and the other number must be 12 take away 2 take away 6 (i.e. 4). The problem here is that 12 is often \"larger\" than 2, 4 or 6 (one digit larger in this case!). Ideally we want them all the same size, for example all single-digits. And you can do that, using a Galois field. All that does is let us \"loop\" around, so that a single-digit number, plus a single-digit number will always give a single-digit number (aka modular arithmetic). But you can't just \"ignore\" the second digit, because in our example above you could have 4 or 14 or 24 or 34 or whatever and get the same answer in that case so which number were you actually asked to store? This is a very contrived example, so it would work in this instance, but it will not work in all instances to just \"ignore\" the tens-digit. But in a Galois field, it's designed so you don't run into that problem. And a Galois field, like encryption and all kinds of other computer science, is built upon prime numbers to make it work in the above manner. And those prime numbers just happen to arise because you want the property that numbers don't \"repeat\" their factors (i.e. you want a number which has only prime factors). So every single bit of data you store at work or in the cloud or your email account or the websites you visit - are all using prime numbers just to store that data safely.",
"There's another *potential* use that I don't think has been covered here. In theory, they can serve as a starting point for beginning communication with an intelligent alien species. The theory goes that if you encounter an alien species, you can establish a sense of mutual intelligence by transmitting a signal that consists of prime numbers: 1, 2, 3, 5, 7, 9, 11, 13, etc - you'd do it by flashes of light with gaps, or beeps like in morse code - whatever. Then you wait for a response. Ideally the aliens respond in kind - the same sequence - or reversed - or the next X numbers. This gives you a starting point. Numbers are universal (or should be) so you can start communicating other concepts to establish a base language. For instance you can start teaching each other your codes for things like addition, equality, subtraction, etc. Like - if you get the following signal where ?? means you haven't seen that code before: 1 ?? 1 ?? 2 1 ?? 2 ?? 3 2 ?? 3 ?? 5 3 ?? 5 ?? 8 You can deduce the following. The first ?? is +. The second ?? is =, AND, the aliens understand the Fibonacci sequence. It's of course never been tested, but its a theory..."
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ms1cyh | Is all of our universe... lit? Can you be hurtling through space and accidentally fly head first into a planet because oops you didn't have your headlights on? | Physics | explainlikeimfive | {
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"> Space ... is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space. > > \\- Douglas Adams, \"The Hitchhiker's Guide to the Galaxy\" The chances of something running into something else in space (other than the occasional hydrogen atom) is miniscule. That said, most of interstellar space is also quite dark. In deep space, nothing's going to be illuminated like you'd see on Earth. If anything, something large or very close by would only be visible as a silhouette against a the background star field of space (and, unless you're inside a galaxy, that star field is going to be very very very dim. For something the size of a planet, you might notice the gravitational pull of the planet long before you otherwise sense it (if you think to look for it). If not that, everything emits a tiny amount of radiation, so there's a very dim and invisible-to-the-naked-eye glow to everything, if you have the instrumentation to see it. If the object was, say, the size of a box truck, floating in deep space, you'd probably bump into it before you noticed it without with some sort of active scanning technology.",
"You know how in a lot of sci fi movies they pass through an asteroid field and the pilot has to maneuver the spaceship expertly to avoid colliding with the Asteroids? In real life, you can pretty much go through the Asteroid belt between Mars and Jupiter with your eyes closed and won't hit anything at all. In fact, you probably won't even _see_ an Asteroid unless you look through a nice telescope. Space is empty. _Really_ empty. Another way to think of it this: In about 4 billion years, Andromeda and Milky Way will collide with each other. Two galaxies with 500billion - 1 trillion stars _each_. The fascinating part? Even after the galaxies collide, pretty much none of the individual stars will hit _anything at all_.",
"It is extremely unlikely for you to collide with anything in space. There is a gigantic amount nothing out there. So it's far more likely to drift through a near empty abyss without collisions. But in the unlikely event that you do end up heading towards a planet you don't know about, you'd feel it's gravity long before you hit it. So that's a warning sign. As for whether you can see it? Almost everything emits infrared light, so you probably have devices in your space ship that can detect that light, even if your naked eye can't. Also if you are in a galaxy, which is where most planets are, there will be stars nearby that light it up.",
"It depends what you define as bright enough to be visible, and what means you're using to detect objects around you. There are rogue planets that travel through the galaxy, and have no star they orbit. These planets could be about the best candidate for the situation you describe, where I imagine you are wondering just how big of an object a human might not visually notice if only looking with the naked eye and no headlights. Keep in mind however that you'd not see the planet, but you'd definitely see the silhouette it blocks out between you and the starry background. So you would have to be pretty inattentive or moving at a pretty high velocity relative to the planet to not notice it approaching, blocking out more and more of the stars in front of you. So the candidate for what you'd run into would perhaps be much smaller. Or to run into something bigger, you'd need to find yourself located somewhere where much of the starry background is blocked by cold, dark matter. I have no idea if this is something that occurs commonly in the universe, but I wouldn't be surprised if some condensing clouds of gas could perhaps cool off (ie emit less light) and begin to compress...? All of this said, you'd have a very long wait ahead of you if you weren't actively searching for something to crash into. As other posts have said, there's a mind boggling amount of distance between objects in space. And since bright things like stars are in the parts of the universe with objects closer together, to get into your pitch black planet scenario, you'd be in a part of the universe with even more mind bogglingly large distances between objects. The chance of hitting something planet-sized is not zero, but it is vanishingly small.",
"Light permeates the entire observable universe, so technically everything is \"lit.\" But even in our own solar system, the objects in the Kuiper belt are very faint because light is governed by the inverse square law (light dims by distance squared). So, it would depend on what type of sensors you have, but objects in interstellar space and especially intergalactic spece would be very close to perfectly dark in the visible spectrum.",
"No. There are large voids between galaxies of nothingness for hundreds of thousands of light years. There is also void space within galaxies. I believe the term is \"Orphan planets\"; planets not attached to a star and just hurtle through space like a supermassive asteroid.",
"I think this was a great question. Its its interesting all the inferences In this response thread. I Inferred OP meant visible spectrum using their eyes (since they referenced headlights) others made no such inference. I also inferred they were asking for possibility not probability and others did not make those inferences. Tons of great, thoughtful, responses.",
"I feel like everyone who answered is hyper focused on a pretty poor understanding of what I assume your question was. It doesn't sound like you're asking about the likelihood of \"colliding with a planet.\" It sounds like you're asking about whether or not you'd be able to see a planet, or asteroid, or anything else, regardless of what your interaction with it was going to be? I don't have the answer for you, but I'm just hoping that, if this is more of what you meant (it seems pretty obvious to me that this is what the actual question was), maybe people will be able to see this and understand the question better.",
"If you were hurtling through the Milky Way, you would see basically the same view as our night sky, but all around you, and with many more/brighter stars (no light pollution from the ground to obscure them. It would be equally beautiful and terrifying, I think. But the Milky Way is a galaxy. Most of space is the in-between nothingness outside of galaxies. If you weren't near anything at all, the only \"stars\" you see would themselves be entire galaxies. You could ram into a planet. That's what an asteroid impact is...but in this case, you are the asteroid. If you were in a ship and had controls, I think we can also assume you will have sensors to see the planet coming. There are rogue planets that drift all alone, so sure, hypothetically we can say that if you have no sensors and are *extremely unlucky* you could randomly hit a planet. But this would also mean entering a galaxy first, and surely you would know you were at least doing that.",
"All of the universe is lit by starlight to some degree (at least in open space). The degree of light may vary wildly depending on where you are, from right next to a star to an intergalactic void, but it's all illuminated. As to whether you could run into an object without seeing it first, that would depend on how sensitive your observations are, how reflective the object is (it's albedo), and how well lit the area of space you're in is. A reflective object near a star (such as our moon) will be hard to miss, but a non reflective object in intergalactic space will be much harder to see.",
"Really good question because it requires multiple answers. 1) There's a **LOT** of space in space. So it's not likely to hit something except over really long periods of time (Billions of years). [Astrophysicist Dr. Becky - Likelihood of Stars to Collide]( URL_1 ) 2) There is actually a lot of rogue planets, asteroids, dust, and other materials out there that are very dark and so would be hard to detect with our current technology until you crash into them. [PBS Spacetime Dark Matter]( URL_5 ) 3) Technically, the vacuum of space is most likely the coldest thing in the universe at a chilly 2.73 K. So any real object made of atoms is warmer than that and so glows some light. This light can be infrared light that you might be familiar with from those glowing red heaters. You and I can't see that light, but your skin can feel it as warmth and we have scientific sensors that can see it. [Scishow Space Coolest Place in Outer Space]( URL_2 ) [PBS Spacetime Cosmic Microwave Background]( URL_3 ) 4) If you had a really bright headlight in front of your spacecraft, even if you were moving really fast up to high percentages of the speed of light (like 99%). The light you emit would still head away from you at the speed of light and so would illuminate objects ahead of you. Though you may not be able to correct your course in time to stop the crash. [VSauce Would headlights work at the speed of light?]( URL_0 ) [PBS Spacetime Speed of Light]( URL_4 ) Edit: Added video links",
"I mean the earth itself doesn't emit light right (I mean naturally speaking . If we had no electricity or volcanic activity)? It's a reflection of light from the sun that makes us visible. So another way to think of this question is are there planets that are so far removed from starlight that they don't reflect any?",
"I'll skip the \"would you actually hit anything\" as it's been covered, and focus on light. The universe is lit by starlight. Within our solar system we're super close to one star in particular: you'd be able to clearly see nearby objects thanks to sunlight, well out beyond the orbit of Pluto. In *deep* space, far away from any star but still within our galaxy, you'd still see starlight, just as you do on Earth in the nighttime. Many people who grew up in cities don't realize that starlight *is* bright enough to see by, if your eyes are adapted to it, but just barely. If you were unlucky enough to smash into a planet in galactic deep space -- and yes, there are [rogue planets]( URL_0 ) that aren't bound to stars -- it wouldn't be *completely* invisible. At the very least you could see its outline where it blocked the stars; at best you'd see it faintly lit up by starlight. If you were out *between galaxies*, there'd be no visible stars, just the faint smudges of distant galaxies. You can see some galaxies with the naked eye from Earth, but whether their light would be bright enough to see by, I don't know.",
"Mmmm. There are such things as rogue planets that don’t orbit a star. If all you had to detect things in your way were your eyes then yes. You could collide with a planet you didn’t see.",
"Think of it this way. At our point in space, any light reaching us is point light from the star's source. No \"reflected\" light is strong enough to reach us past a certain distance, just look how small Venus and Mars are in the sky. We see things in deep space far away when they block light from the stars. So to answer your question, if there is a star close enough to you, then everything is lit. If you are in deep space, then objects in space will cause dark spots as you move through. Theoretically, you could hit it if you were not paying attention.",
"You know how the moon has phases? Meaning one side is lit and one isn't? If you're flying toward a star, any planet or moon in your way will be dark to you.",
"I believe everything is “lit” it is never absolute zero anywhere in space (as far as I know), and anything that has heat is going to also produce light. So they will technically have light, but I mean a human eye can’t see it"
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ms1ez3 | What is the impact of browsers no longer accepting 3rd party cookies and Apple’s Intelligent Tracking Prevention? | I know it impacts advertisers ability to target, but would love a clearer explanation of how it works and the impact. | Technology | explainlikeimfive | {
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"An analogy: Every time you go anywhere in public, the shops you use, the buildings you enter, and the people you interact with put a coloured sticker with a number on you. It's just a sticker, it contains only a number, it's not \"private\". Say the baker always uses a green sticker, and he numbers based on the order you walked into his shop. And the butcher uses a purple sticker and he numbers based on a random number that he makes up. And the grocer uses a green sticker and he numbers based on how much you buy from him. Whatever. It doesn't matter. The butcher, the baker and grocer don't know what the other people's numbers mean, it's just a number. And when you get home, your arm is full of coloured stickers with numbers on. But it means that when you go out tomorrow, the butcher knows that you're #27, that you buy beef from him regularly and that yesterday you were interested in how to best cook steak. Not a problem. The grocer knows nothing about what the butcher's number means or what the butcher knows about you. The problem comes when the butcher, the baker and the grocer all employ a company to put those stickers on you, because they don't want to do it themselves. The company does it \"for free\" to them, and labels you with a pink sticker with a unique number. When the butcher asks and says that you have a pink number #35 on you, the company can tell him everything he'd normally store about you (because the company have recorded it for him). When you go to the grocer, he can also talk to the same company and ask them for everything he wanted to remember about pink #35. Still not a problem. But now that one company runs all the data collection for lots of people. So they can tell the butcher that you went to a rival butcher's last week because your pink #35 was spotted there. The butcher can ask for other information about pink #35, so he knows that you bought turkey gravy yesterday and maybe he can try to sell you a turkey today. And the company then sells that data about pink #35 to completely unrelated companies that you've never dealt with, say a clothing store, so they can suggest that if you're eating that much meat, maybe you should try a bigger size of jeans, and so on. The stickers are cookies. The company are data aggregators like Google ads, many tracking cookie and analytics firms, and the average website has something like 35 companies that put stickers on you where those stickers are shared with EVERYWHERE you go which uses that same company. Apple's (not new, unique or innovative) idea is to keep your arms covered so you only show the stickers you want to the companies that need them and when you go to the butchers they have to give you a new sticker from the company because you refuse to show them your previous ones, so they have no idea who you are. So they can't tie in that information about you from across the net, sell it, and use it in potentially nefarious ways. And occasionally, they'll take the stickers off you entirely because you haven't needed them in a while.",
"Here's a slightly deeper and wider explanation (ELI8): Let's talk apps first. Your Apple phone is given a unique ID in the factory. This number is unique to your phone like a license plate number or a Social Security or National ID number. If you open the Facebook App, the Facebook app reads your unique ID number and everything you do in Facebook App is reported back to Facebook with your unique ID. So, if your ID is 2399, Facebook App will tell Facebook say that 2399 is looking at puppy pictures. Now, if you click on an ad for a Puppy Game the app store will load the Puppy Game, and you install the Puppy Game. When you buy something in the Puppy Game, the Puppy Game tells Facebook: Hey, 2399 just spent money on the Puppy Game! Facebook now knows that 2399 really likes Puppies from information across multiple apps. Now, Apple doesn't like apps sharing info. So, instead of telling Facebook your ID is 2399 and telling Puppy Game your ID is 2399, it tells Facebook your ID is 5522 and it tells Puppy Game your ID is 999. Apple knows that 5522 is just an alias for 2399 and that 999 is just an alias for 2399. But to Puppy Game and Facebook apps, 5522 and 999 are different people! Now your data is more \"private\" in that two apps can't share info anymore. Of course, if you log into your Facebook account on both Facebook and Puppy Game, Facebook can now figure out that 5522 and 999 are the same person because you use the same email address and password on both apps and both apps tell Facebook. In browsers, the idea is similar except instead of Apple providing the ID for your browser, 3rd party sites leave a cookie (basically just a blob of data) on your browser, which acts as the 3rd party's ID for you. Every website that wants to can look at the cookie and send that cookie back to the website. If two cookies match, then the websites can tell you are the same person. Apple's tech will do the same thing as for the apps, which is that you can leave a cookie for your website, but Apple will choose the cookie, and you can only get the cookie for your website, and that cookie will be different for other websites so various websites can't tell you are the same person. Or the user can disallow cookies altogether. Of course, if you login to a different websites using your email address or Facebook Login, the different websites can tell you are the same person! So, Apple's move basically prevents websites from stealthily knowing you are the same person. There are many ways you can explicitly tell the site who you are without really know it.",
"The explanation by u/ledow is mostly correct. There are two things I’d like to add: - Privacy through aggregation - Consequences of eliminating cookies Google, Facebook, etc. are not in the business of selling your data. They’re in the business of selling ads. That might sound weird at first, but consider the fact that their defensible moat of technology and IP is contingent upon having *that* data. Why would you sell your resources instead of leveraging them towards selling your product? They offer targeted advertising, which might give information about those targeted through completed purchases and account creation, but that’s only once a user has made a decision to buy the product advertised. Eliminating cookies has led to a weird spot. Google’s Chrome is so incredibly popular that they can make changes without much repercussion, and the ones they’re going forward with are “pseudo-privacy” enhancements. They’re more so adjustments to make Google seem like good guys along with Apple, rather than exposing more of you to the internet than before. Before, you’d get unique identifiers attached to you at a website level, which Google would collect to track you across sites. Because it would take lots of collaboration across many, many sites to discern these identifiers, most people would default to just using Google’s in-house ad offering. This was good for your privacy in that, as mentioned above, Google sells ads *from* data rather than the data itself. The change coming is that instead of you having a *unique* identifier, you’re getting a *cohort* identifier. Chrome will have machine learning models built in which map your behaviors to pre-determined cohorts (the models are exported from supercomputer computations of data they already had on everyone, so there is no ML computation going on in chrome; it’s just matching your history to cohorts). For example, if you buy pet food and leather belts, you might be put in the pink35 group. To be clear, these cohorts are **tremendously** complex, are based off of thousands of features, and they’re too abstract for any human to discern. This might seem good for privacy since if you go around with pink35 on you, you’re going around with a tag shared by thousands of people. How could that not help privacy? The reason it doesn’t is that by having cohorts, it becomes quite reasonable to collaborate across sites to discern what these cohorts signify to some extent. You’ve reduced the quantity of identifiers significantly, especially when businesses inside an industry likely share cohort customers. It becomes even worse when there are now thousands of other people who act like you helping to fill in the gaps of what you likely do. Suppose I’m marked with pink35. Everyone else in pink35 is willing to buy without coupon codes or sales, so sellers adjust their sites to hide them from pink35 or to even increase prices. This is price discrimination and often occurs using geography or device screen size. However, with these cohorts, you can do it easier and more robustly. Google is saying “look how helpful I am” while causing a large mess. This analysis of cohorts came from Ben Thompson of Stratechery.",
"First u/ledow's analogy is spot on. It effectively prevents a lot of that creepy behavior when you browse an item at one site and suddenly the Internet is pushing ads for that class of thing on every web site you visit. Buy a lightning cable on Amazon, suddenly the sidebar in Reddit is filled with ads for lightning cables and iPhone accessories. For the most part, this is a good thing. So far, the only thing I've found is that it breaks some banking sites that use a third party for their online banking systems. My personal bank doesn't work with this turned on in Safari and I have to turn off the feature when using the bank.",
"Follow-on question: if cross-site and cross-app tracking becomes less viable, then advertisers don’t make as much money. How does that affect the economy of the web and the availability of “free” websites that make their money selling your data?",
"I do work in the field, and as of now the impact is not that noticeable. Sure, there are less people to target, but there are still enough people using chrome (not yet blocking 3rd party cookies), consenting to cookies or not updating their browsers. Those who know enough about tech to block 3rd party cookies probably also know enough to install adblockers anyway. But it is a huge topic for new business, as there are a lot of cookieless solutions, for example contextual targeting or geo-targeting which yield similar results. So yea, for users it is way better (as the top comment explains) and for advertisers there are just other ways. In my book it's a win-win or at least a win-slightlyinconvenienced."
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ms1u24 | Gills can absorb oxygen from an aqueous environment. Why can’t gills absorb oxygen from a non-aqueous environment? | Additionally, in the instances like salamanders that absorb oxygen through their skin is this the same function? | Biology | explainlikeimfive | {
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"They can, but they collapse and stick together when out of the water and as a result there's far far far less surface area for oxygen exchange exposed to the air than exposed to the water. If you could somehow keep gills fully open and exposed in air, they would likely work. Gills work in water because there is a huge amount of surface area presented to the water. Lungs don't need to present nearly as much surface area for the same amount of oxygen absorption because there's nearly 20 times the amount of oxygen in air as their is in water. Lungs avoid collapse by having lots and lots of tiny pockets that stay open in air, so there's plenty of surface area for gas exchange.",
"They still can as long as they are wet. Gills don't work that much different from lungs really, the big difference being that gill's dry out much more quickly. When you first pull a fish out of water, at first it is not suffocating. It actually has the opposite problem, and is dealing with too much oxygen, poisonous levels of oxygen. If a fish could keep its gills wet long enough, this would end up killing it. But instead of eventually the gills dry out and then it dies of suffocation.",
"Gills are like tiny little hairs made out of special meat that can pick up oxygen in the water. These meat hairs are better at picking up oxygen when they are in water. When they are in the air, they can still pick up oxygen, but they dry out really fast because they are so used to the water. Remember Spongebob when he went to visit sandy for the first time? He got really dry and started to crack. The same thing happens to the gills and they can't pick up oxygen as well anymore.",
"The thing is though, if you can keep your gills wet somehow, you can go in air just fine. Crayfish are a good example; the gills are located in the thorax - inside the body - so they have some control of humidity (plus the enclosed space helps), and also temperature to some extent by their location in sun/shade. This is how they colonize new areas: they go for a walk over land and look for new water bodies to live in. How far they can walk depends on species (some are better at it than others), but still, they have more distance before drying out than you may think.",
"The main issue is interface, which water provides in a much better way than anything else. Gills have the blood vessels all disposed in an array that allows the water to pass through, which in turn allows the oxygen to be captured by the oxygen-carrying molecules of the organism. Land crustaceans, like some crabs and woodlouses, also breathe through gills, secreting a liquid over the gills to capture the oxygen in the air Salamanders start their life with gills, some never lose them, and some develop lungs but still keep the skin as a breathing interface... but it needs to be always wet. More concisely, just about anything living needs water in some way to work (specially if involves proteins) , and breathing is such a case."
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ms2509 | I was just reading about modern submarines on Wikipedia such as the German type 212. Why are they capable of travelling faster submerged than surfaced? | I would have thought that the opposite was the case as less mass is pushing against the water while surfaced. | Physics | explainlikeimfive | {
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"There are a few factors slowing down submarines on the surface. Water does have surface tension which makes it harder to push through it on the surface then under water. You also end up pushing water upwards into the air creating a bow wave which will push on your hull. This bow wave will not be the same under water. You also get waves hitting the ship slowing them down. A trick to traveling faster on the surface is to cruise in semi-submerged mode. This is when they trim the boyancy so the submarine have almost no boyancy. This menas that most of the submarine is under water and only the top of the sail or even just the periscope is above the water. Something comparable is done with big container ships in that they have a huge bulb on the bow just bellow the waterline looking similar to a submarine bow. This will then break up the bow wave making it easier for the rest of the hull to follow.",
"The German type 212 is a submarine that uses hydrogen fuel cells to spend long stretches of time under water. This type of submarine along with nuclear powered submarines have a hull optimized for traveling fast under water. Older types of submarines that mostly use diesel and batteries don't spend as much time under water, because they can't and therefore have hulls more optimized for traveling while surfaced. If you optimize a submarine for going as fast as possible under water it will be slower above the surface. They often create huge waves along their side if they try to go fast while surfaced. Hydrodynamics are weird and counterintuitive and hard to compute, but generally something optimized for one sort of situation won't work as well in another type. Submarines like the 212 are designed for raveling underwater and this is how their hulls are optimized.",
"For boats its about how cleanly you can move through the water. The hull of modern submarines is optimized for underwater operations because they'll be spending weeks at a time submerged. Nice clean lines mean limited skin drag (which is going to be the big player here). On the surface they create a bow wake which eats up a lot of energy, modern cargo ships have the big bulbous bow to form the wave at just the right spot the reduce its effects at cruising speed and make it *just* the right length for the ship. Probably the most important part of the confusion here is power. A German Type VIIC U-boat (one of the most common) had two big diesels that could produce about 3,000 HP on the surface, but underwater it was restricted to about 740 horsepower from its weaker electric motors and batteries. It was this reduction in power that limited its submerged speed, not an increase in drag. Modern non-nuclear subs have far more powerful electric motors, and are often *always* electrically driven. On the Type 212 it seems that the propeller is *always* driven by the electric motor and that on the surface the diesel just serves as a generator so there is no huge drop in horsepower when they submerge so the mild reduction in drag results in an increase in speed, unlike the old U-boats where the massive drop in power outweighed the reduction in speed.",
"Once you get down in depth even a short distance, the propeller gets a better bite on the water. On the surface, the top 10% of the propeller might still be underwater, but it is just making a lot of turbulence.",
"A ship on the surface produces \"gravity waves\" in the surface of the water as it moves. These are basically what we normally think of as waves - bits of water going up and down. Mariners will talk about a \"bow wave\" and a \"wake\", also sometimes of \"wash\" which is water disturbed by the engine. The energy required to generate these waves is a significant factor in the drag on a surface ship. Also to be considered are frontal area drag, skin friction drag, and pressure wave generation. When a submarine is submerged it is not generating gravity waves. Being fully submerged changes the effects of the other factors but not enough to outweigh the saving made on the gravity waves. Therefore the boat moves more efficiently and the same motive power can move the boat faster."
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ms2qbi | If a Superfluid flows without any loss of kinetic energy, then how does it not violate the First Law of Thermodynamics? | Physics | explainlikeimfive | {
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"Because no energy is being created or destroyed. If you attempted to do any work with this system, to get any energy out of it, then it would indeed lose kinetic energy and be fully compliant with the First Law of Thermodynamics. It is a misconception that the First Law disallows perpetual motion. What it disallows being able to extract energy or work from a system perpetually. It is perfectly acceptable for a self-contained system to be in perpetual motion, but you will be unable to actually extract anything from it (and it remain perpetual).",
"If you have a superfluid on a half-pipe, and drop it down, it would go up the other side, and then back down, and back up to where it was dropped, and back and forth, with no frictional losses. This is just a reversible system, which is allowed by thermodynamics."
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ms3hq7 | Why does the second shampoo lather up so much more than the first? | Chemistry | explainlikeimfive | {
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"Typically oil and water will not mix. Hair can be filled with oil from your body, especially after a few days of not washing it. The purpose of soap is to help oil and water mix together so the water can wash it away. The first application of soap will have a lot of oil to work with. This will \"use up\" the soap and make it more difficult for it to form suds. Once you wash away the soap/oil mixture with water, the second application doesn't have much oil to mix with and easily forms suds. Try this out with something like lard and dish soap on your hands in a kitchen sink. Rinsing your hands off without soap (especially with cold water) will still leave them slimy with oil. Rinse once with soap and the oil will go away but the soap won't bubble that well, second time and you'll get more suds.",
"The dirt stops it from sudsing, the second one sudses because its already cleaned from the first shampoo. Suds arent really indicative of wether its cleaning or not, its an indication if how clean your hair already was.",
"I'm not educated in this area, but my hairdresser told me that shampoo is used to \"open the hair\" so that you easily get the dirt out while conditioner closes then up again, you've probably seen this on a commercial at some point. However, my theory about why the second round of shampoo lathers so much more than the first one is because most of the dirt, oil and fats are already gone from the hair, making it lather more. This also works if you get dirty / greasy hands and wash them two times, it always lathers more the second time."
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ms3n4j | What is the difference between a Ponzi scheme and dogecoin? | Economics | explainlikeimfive | {
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"In a Ponzi scheme, you sell *nothing* \\- you're pretending to sell an investment, but you're really just stealing people's money, moving it around to make some people *think* there's an investment out there, then stealing as much more as you can before skipping town. Dogecoin is a thing that you can buy. It exists. Whether or not it increases in value has nothing to do with it.",
"> Since there is no value to dogecoin besides what an investor is willing to give you for it, what's the difference? *That's* the difference. I invest in (e.g. buy) dogecoin, I pay whatever someone else is willing to sell for it. (I hope to buy it cheap). I later sell my dogecoin, and I get whatever someone else is willing to buy it for (I hope to sell high). That's all legit. With a Ponzi scheme the buying part is the same, but the selling part is the fraud. When I go to my Ponzi contact and collect on my investment I'm *not* getting the value based on what other people are willing to buy it for. The fraudster is artificially inflating the value by giving me *more* money than what other people have paid for it in the hopes I will then reinvest with more sums. Also, a Ponzi scheme involves a person whose goal is to use the artificial inflation to dupe people into investing more money which they then pocket and skip town. An element completely absent from simply crytopcurrency investment.",
"This applies to crypto currency in general, and there are serious economists who are skeptical of crypto currency for exactly this reason- since crypto isn't \"backed up\" by anything, like physical gold or the dollar being official currency of the US Government, it could easily wind up crashing and the value going to 0. There is, however, a real and useful function that crypto currency provides, which is to provide both a medium and a mechanism for exchange that is not under the control of a government authority, allows for anonymity, and is not inflationary. This is why crypto got off the ground in the first place- it fulfills a real-world need, which a Ponzi scheme does not. Whether crypto is in a massive bubble right now is the subject of a lot of intense debate, but it should be noted that some of your framing can apply to the US dollar as well- it has no value except what a merchant is willing to give you for it. The only difference is that the US Federal Government has laws that encourage people to use the dollar as the primary medium of exchange."
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ms4z8b | How come light reflects on windows during the night, but during the day it just passes right through? | In general when you look at a window during night, then the lights of your phone, TV, lamps reflect on the window making it kinda mirror like. But during the day it just phases right through and reflections are hard to see. Is this because of the massive amount of light or what? | Physics | explainlikeimfive | {
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"Light always reflects on Windows, you simply can't see it during the day because the amount of light coming in from the other side drowns out all/most of the reflected light. This is the same concept used for one way mirrors, which is simply a pane of glass treated to be very reflective, however these do only work if the interrogation room is brightly light, and the observation room is in gloom/darkness"
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ms59l3 | If pi is unlimited, how can we get exact values for areas/circumferences of circles? | E.g. how can we say that a circle has an area of 25.00cm^2 if pi is irrational?? How can a circle, a closed shape, have a limited area if pi is unlimited?? | Mathematics | explainlikeimfive | {
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"Those are purely theoretical values. The area of a circle, by deign of including an irrational number in its calculation, is also irrational. That’s why circles are often written in terms of pi, which is considered the exact value (e.g., 10pi in^2) Anything else is technically an approximation.",
"Rounding up numbers after a few digits offers all the accuracy we can typically ever need. Someone hopefully can chime in on the concept, especially as it relates to space flight. Eli5 - the difference between 3.14 and 3.14-to infinity isn’t much."
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ms5beq | how can photons and other elementary particles have 0 dimension yet comprise objects that are extended in 3 dimensions? | From my limited understanding of physics, it seems like since a photon has 0 dimension, it should reflect off 0% of the surface of an object, because its cross section that collided with the surface is 0 units wide. That would mean an infinite number of photons would be required to capture the features of any object at all, which seems absurd and impossible. | Physics | explainlikeimfive | {
"a_id": [
"guqnbqm"
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"text": [
"A photon acts like a wave, a particle, and a probability distribution (like an electron), meaning that it is not 0 dimensions. A photon has just enough force behind it that when a lot of photons are working together, they can propel objects (look into solar sails). From my understanding, photons are 1-dimension, in that they are a single point (not sphere) that expresses itself as a wave. Think \"How thick is a wave of sound?\" It doesn't have a thickness/volume, but it is present along its line. If you look into String Theory, it's main basis is that the universe is made of particles that aren't 3-dimensional. It is a \"string\" like a rubber band on a 2-d plain. When that band is \"twanged\" or shaken, it vibrates into a 3-dimension shape (smaller than quarks, which are what protons/etc are made of). The frequency of the \"twang\" is what is responsible for different particles being observed/formed. (This is ONE theory of the universe. When following String Theory, there are 10 (+ ?) dimensions.)"
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ms6h6q | Desalination by RO creates concentrated brine, which is then released into sea back. This causes environment problems. Why cant we use this brine for other process like salt harvesting etc, which requires brine? | Recently I watched these videos which explains the negative impact of releasing concentrated Brine produced from RO Desalination plants back into Ocean. 1. [ URL_2 ]( URL_3 ) 2. [ URL_0 ]( URL_1 ) This got me thinking why can't we use this brine in an commercial beneficial way, given that there are several industrial process that uses Brine as raw material. On top of my head I could think of Salt production, Caustic Soda production etc., Why is brine not used commercially? And what are the challenges and is there a solution? | Technology | explainlikeimfive | {
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"The challenge here is mostly that salt is ubiquitous and fairly worthless - $58/ton It takes a lot of energy to drive off *all* the water and produce rock salt, so the costs are higher than what can be recovered by selling the salt. The brine may have a few uses, but a large DeSal plant is producing brine at a much greater rate than you could realistically consume the salt locally."
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ms75wf | How do gaming headsets allow us to differentiate distance and location of noises, such as if footsteps are on the floor above or below you, or where and how far gunshots are coming from in a BR type game based on where you are standing and which way your camera is facing? | Technology | explainlikeimfive | {
"a_id": [
"guqrqsm",
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"text": [
"It's basically the same as how you do it normally. We can work out where sounds are coming from based on tiny differences in timing and level of sounds arriving at the two ears. There's also some filtering of sounds based on the shape of your ears and the position of the sound. The underlying idea for virtual audio is that you reproduce those tiny differences in the ears using a bunch of computer calculations. Really, it's not all that different from how VR headsets let you see in 3D. You see in 3D because of the differences that your two eyes see. In VR, the headset sends a slightly different picture to each eye to let you perceive depth etc. It doesn't matter how the signals get to your eyes or ears, whether they are arriving naturally or via a screen/earphone. The important thing is what the light/sound is like when it's *in* your eyes/ears. Source: hearing scientist with a PhD in sound localisation :) If you want to know more about how we work out where sounds are, I'll find a link to another thread :)",
"Technically it's not just the headsets that allowes this but also how the game is programmed. In games you have sound files or sound clips that are played based on a trigger, for example a footstep or a gunshot. Based on that sound clip and the location of you and the source of the sound different algorithms can change and affect the sound so you perceive it as being further away. Some games with tighter development budgets or with limited development teams might not have the resources to implement this type of sound design. This leads to some games having worse sound and making it really difficult to tell how close a sound source is or which direction it's coming from. In most games this doesn't really matter too much, but in first person shooters this can be really frustrating when it sounds like an enemy is just around the corner when he actually is on the other side of the building or 30-40m away."
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ms83qg | PoW (Proof of Work) vs. PoS (Proof of Stake) | Im just trying to understand if theres one that is superior and the details of how each works and the pros and cons of each within the crypto space | Technology | explainlikeimfive | {
"a_id": [
"gusbjx2"
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"text": [
"I can explain this. Bitcoin was the first practical system where a bunch of computers can agree on What's What, agree on the state of the data mutually rather than being told it by a leader. It does this by asking each computer on the network for its version of the data. But that raises a problem: someone could insert biased data favourable to themselves, spin up a million virtual machines, and have them all claim that's the state of the data. So Satoshi's solution was to add proof-of-work, computationally difficult puzzles that must be solved to have input regarding the state of the ledger: [Bitcoin: A Peer-to-Peer Electronic Cash System]( URL_1 ) said \"If the majority were based on one-IP-address-one-vote, it could be subverted by anyone able to allocate many IPs. Proof-of-work is essentially one-CPU-one-vote.\" Proof-of-work and proof-of-stake are two slow-down mechanisms designed to add friction to input on the state of the blockchain. You couldn't shout your own data over the other voices, because doing so requires more computers, more electricity, and that's expensive. There are problems with this slow-down mechanism, notably [Bitcoin's enormous energy consumption]( URL_0 ). So proof-of-stake aims to achieve the same thing, but instead of having to buy computers and electricity, you have to buy the cryptocurrency of the blockchain itself. It achieves the same ends, i.e. making it expensive to have input into the state of the ledger, and therefore prohibitively expensive to input malicious scurrilous data, but without the need to burn so much energy."
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"https://digiconomist.net/bitcoin-energy-consumption/",
"https://bitcoin.org/en/bitcoin-paper"
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ms86qr | What is Gödel's incompleteness theorem, and why is it so infamous in Mathematics? | Mathematics | explainlikeimfive | {
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"text": [
"There are actually two incompleteness theorems. They are in the realm of logic, which attempts to axiomatize mathematics. Both theorems are about *formal systems*, which you can think of a set of rules for inferring from axioms. Kind of like meta math in a way. The **first incompleteness theorem** says that all *consistent* (you can think of this as there are no contradictions) formal systems of mathematics that can carry out *Peano arithmetic* (just normal addition/multiplication, basically, with integers that are ordered) are *incomplete*. Here, incomplete means that there are statements you can formulate but you can't prove. The **second incompleteness theorem** says that no consistent formal systems of mathematics that can carry out Peano arithmetic can prove their own consistency. I don't think they are really \"infamous\", by the way—Gödel is very respected, and no serious mathematician thinks these theorems are wrong. But maybe they can be considered depressing or disheartening. The first theorem says that there are some mathematical questions we don't know the answer to and that we *can't* know the answer to! To mathematicians whose whole purpose is to get those answers, it seems horrifying. And the second theorem says that you can't really \"know for sure you're correct\" since the formal system can't prove its own consistency.",
"In math we have basic statements which are accepted as true called axioms. These are basically the fundamental ground rules of math. These, combined with rules of logic, allow us to deduce other, more complicated statements. For a while in mathematics there was a big push by a handful of mathematicians/logicians to try and root *everything* that you could possibly prove into as few axioms as possible. Basically they wanted to take nothing for granted if it could be avoided and, from those few axioms, prove everything that could be proved true. Stated more formally, they wanted a system that was both *complete* (everything that is actually true can be proved true) and *consistent* (nothing that is actually false can be proved true) Gödel proved that this was false. That any but the most rudimentary systems will either be incomplete (there is something that is true that the system can't prove true) or inconsistent (that there is something the system says is true but it actually isn't). It was infamous because it not only dashed the hopes of the top mathematicians at the time but it is somewhat counterintuitive to think that you can't reduce all of math to a handful of simple axioms and rules."
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ms9e0c | How do fruits like oranges and watermelons are made to grow seedless? | Other | explainlikeimfive | {
"a_id": [
"gur5y2e"
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"text": [
"Some fruits wont grow seeds if they’re not pollinated so farmers just cover the flowers. Oranges use this method. Some fruits won’t grow at all unless they’re pollinated, so farmers pollinate them with another closely related species to produce infertile hybrids that won’t produce seeds. Watermelons use this method. Some fruits won’t do either, and the seedless varieties are a single infertile mutant strain that has been cloned repeatedly. Bananas use this method - they’re all genetic clones of a single plant."
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ms9num | Why do all my jars with chili oil in them seem to leak, even when stored upright? | I love spicy sauces of all sorts, and they usually contain chili oil and/or chilis. Every time I pick up the jar, the oil has somehow climbed up through the cap seal, through the label and now all over my table/hands/everything. Why does this happen to these types of sauces but not the others? Edit: the jars are made of glass. | Other | explainlikeimfive | {
"a_id": [
"gurzl2g"
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"text": [
"When you pour out of the jar a little bit is probably getting caught around the rim, then as the jar sits for hours/days the oil creeps down and covers everything. A little bit of oil goes a long way! As another comment said, get jars with a proper pouring spout and wipe any excess oil off the rim after use."
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ms9q6b | Why are the chinese persecuting uyghurs? | Other | explainlikeimfive | {
"a_id": [
"gur82id"
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"text": [
"Racism, islamaphobia, etc Also the Uyghur culture is distinctly different than that of the rest of China, being geographically farther west as well as religiously being majority Muslim. The Chinese Communist Party wants to best control the nation by having everyone on the same page culturally. Meaning the distinct culture of the Uyghur population is a threat to that vision. Note how you said “the Chinese” and I said “the Chinese Communist Party.” You HAVE to make the distinction between the two. When we don’t make that distinction, it’s like you’re saying all Chinese people, or the whole nation of China, feel a certain way. This can make people’s racism and hatred against all Asians enhance, which in the USA we see has become an unbelievable problem as of late."
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ms9t0o | why does it take several months to reduce the fat in our body but just some days or weeks quickly to gain weight ? | Biology | explainlikeimfive | {
"a_id": [
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"text": [
"We evolved in times of scarcity, when it was often difficult to find enough food for survival, let alone health and comfort. In those conditions, being able to store excess calories and being slow to lose them when not needed led to increased survival in particularly bad conditions. We are the descendants of those whose bodies tended to hold onto extra calories longer. There's very little survival advantage o being able to shed weight quickly (for humans at least), but there's tremendous advantage to being able to carry around enough extra calories (a/k/a, fat) when times are tough. Congratulations - you've won the evolutionary lottery. Maybe in tens of thousands or hundreds of thousands of years, if we continue to evolve in times of abundance, we'll lose \"gain easily/lose with difficulty\" traits.",
"Because weight and fat are not as directly comparible as we like to think. If you were to measure yourself every hour, you would see significant weight shift across the day. Honestly, it is virtually impossible to gain a significant amount of weight in a day. Maybe some of those youtube channels that force feed themselves 30,000 calories A few reasons why things vary so much: * Water retention: salt intake, exercise, or other environmental factors will influence how much water your body retains. * How much 'extra' stuff you are processing on your last meal. * Short vs long term storage:. Newly digested food is stored in easily accessible sugars. If you eat beyond those reserves, you body stores excess as fat. Because of the chemistry behind this short term sugars are bound to 2x as many water molecules. This is why when you first go okn a diet, you see a fast drop followed by slow loss, and coming off a diet does the opposite. Remember, sugars are carbon based. Your body has only one way to get rid of that carbon is to breath it out as CO2",
"You feel very hungry when the levels of sugar in your body get low. And there are sugars and carbs in almost all the foods we eat regularly; sodas, sweetened beverages, anything with bread or pasta, etc., lots of carbs, lots of sugars. So your body is never forced to switch to the \"use the fat for energy\" method of survival, because it's just easier to use sugars for energy, and we eat so many sugars. Basically, look into the premises behind a [low carb diet]( URL_0 ), the whole idea is to reduce this sugar intake to force the body to switch to using its accumulated fat for energy. And the diet typically tries to trick the hunger away by advising to eat meat and vegetables (but not sugars or starches) \"until full\".",
"Most of what you can gain in a really short time scale (over a few days) is water. If you Jack up your food and salt consumption your body will retain a lot of water to deal with it. Long term sustained weight gain is limited by how much you can eat over what your body will burn. I guess there’s really no hard limit on how much you can eat whereas you can’t eat less than nothing. Therefore the fastest you can lose weight is limited by how many calories your body burns in a day. So even if you literally ate nothing, most people would find it pretty much impossible to lose more than a pound a day. And unless you are very large, that would require lots of exercise and literally no eating. Realistically a pound a week is ambitious. Since a pound of fat contains roughly 3500 calories of available energy, that would be roughly a calorie deficit of 500 calories a day. If your body burns 2000 calories per day, you could only eat 1500 which will make you pretty hungry. With hyper palatable junk food it is really easy to consistently eat more than 2500 calories per day making you gain weight faster than a pound a week."
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msafo8 | I feel like this is a dumb question but please be nice. I saw something about how women are dying in car accidents because features are made to cater to a man. How could this be fixed without creating the opposite problem? (Men dying because of cars made for women.) | Other | explainlikeimfive | {
"a_id": [
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"text": [
"Here is an actual report on the topic. The differences are not because crash systems are designed for men, its because the accidents women get into are more severe based on the type of accident and types of cars involved: URL_0",
"They could run two tests on cars - one with a female car crash model and one with a male car crash model. And then make safety features which fit both.",
"Car manufacturers can not create safety features for actual human people. Instead they make the safety features for the test models we have of humans. The problem is that these are all males. There was even an issue with safety devices in cars killing kids and infants which lead to the introduction of kids test models and any safety device that would damage these would fail the tests. So the car manufacturers changed the seatbelts and airbags to work better with kids. But nobody have thought much about the fact that females are also different from men and that the safety devices might not work properly with the different models. And by implementing more female test models and also of varying different sizes the car manufacturers will be forced to implement safety devices that can be adjusted for these and be safe for everyone to use.",
"Women who are small are at risk of being killed by a car's air bag in an accident because they have to move the seat so close to the steering wheel. They are also at increased risk of being decapitated by the seatbelt because it will often cut across their neck. There are fixes - the air bag it can be disabled but car dealerships are very uncooperative about doing this because they are frightened of litigation, even if the car owner is willing to sign a waiver. For the seatbelt there are various types of clips that can be attached to move it down and away from your neck, but they are generally a pain in the ass to use because they have to be adjusted all the time."
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"https://www.iihs.org/news/detail/vehicle-choice-crash-differences-help-explain-greater-injury-risks-for-women"
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msbjta | How do Volcanoes work? | I've been alway fascinated by volcanoes, but I've never been able to understand how they work. Can somebody help me? | Earth Science | explainlikeimfive | {
"a_id": [
"gurjwe1"
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"text": [
"Very simple explanation: lava underground is under a lot of pressure. Sometimes when the tectonic plates move, a weak point is created where the lava can push through, sometimes creating a volcano."
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msbpzh | Why does Icy Hot hurt so badly when it gets on your penis and testicles but doesn’t hurt when it’s put on the rest of your body? | I just don’t understand why Icy Hot (or anything similar) is so helpful and feels good when applied to skin that isn’t your private parts but absolutely burns like the dickens when it accidentally (or not so accidentally) comes in contact with your genitals. I feel like skin is skin and muscle is muscle in this sense so what’s the difference? | Biology | explainlikeimfive | {
"a_id": [
"gurmkon"
],
"text": [
"Your genitals are laden with nerves. This serves multiple purposes, chief among which, keeping them safe. This is literally the only way that you are going to create new life and procreate, which selective pressures have driven us to strive to do. So if your genitals feel like they are on fire, it because they are telling you there is danger and you need to act to resolve that danger. It's the same reason a kick to the groin hurts so much worse than a kick of equal force to the arm."
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msc2wl | When you swallow, how does the body know whether food should go down into the stomach and not the lungs? Is it possible to swallow something and have it go into your lungs instead? | Biology | explainlikeimfive | {
"a_id": [
"gurooss",
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"text": [
"You have a flap in the back of your tongue that folds when you swallow. Like a weird hatch that yoinks the food into your stomach. When water \"goes down the wrong tube\", the flap malfunctioned. *It also can activate your gag reflex, so careful exploring*",
"There's a flap, called the epiglotis, that closes off the airway to prevent this. The act of swallowing is what closes it. It is possible to accidentally get food and drink down into your lungs, and there's medical conditions that cause issues with that flap. So what happens to food and drink that you accidentally inhale? If it's not too large to get lodged and cause choking, you usually cough it up, otherwise it's absorbed back into the body or the body treats it as an infection."
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msdhnw | if atoms are mostly empty space, then is the vacuum of space the same kind of emptiness? Or are they different? | Also, how can atoms be solid and opaque if they are mostly nothingness? | Physics | explainlikeimfive | {
"a_id": [
"gurxwgc",
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"text": [
"It's more appropriate to say that atoms are mostly almost-empty space, with some areas of less-empty space. Remember, at that scale, particles don't hang out at specific points. They're fuzzy clouds distributed across regions of space, in the sense that they are more likely to be in some areas than others. It's true that atoms are much larger than the particles that make them up, but \"empty\"/\"not empty\" isn't a sharp distinction the universe actually makes. Even the deepest vacuum isn't totally \"empty\", it's full of the same fluctuating fields whose bumps we call \"particles\" (or to interpret this another way, particles are constantly appearing and disappearing even in high vacuum). An analogy here is that even a very calm ocean is moving and flowing, even though \"waves\" as distinct objects are mostly noticeable along the shoreline. Atoms aren't \"solid\" - that notion only makes sense for collections of atoms. It's better to say that atoms are kind of \"squishy\" (in the sense that one atom can't easily enter space very close to another), but that it takes quite a bit of force to squish them by very much. They're opaque because their electrons interact with light - remember, opaque doesn't mean \"physically blocks movement\", it means \"light can't pass through\". At that scale, light is \"as big as\" anything else.",
"When you get down to the size of atoms, concepts like \"space with matter in it\" and \"empty space\" kind of break down. We can sort of measure the \"sizes\" of electrons, and atomic nuclei, but it's also valid to think of them as single points in space that have certain properties, and whose charges affect a certain area of space. Two solid objects don't pass through each other because of repulsion between the electrons in both objects.* It's got nothing to do with objects that exist in 3 dimensions hitting each other physically. We do \"collide\" particles in particle accelerators, but it's more accurate to say that we shoot them close enough that they interact through fundamental forces. All basic collisions that we imagine, like a billiard ball hitting another, are Electromagnetic interactions. Light, likewise, does/doesn't pass through something because of how the atoms in the material interact with the photons (or light waves) hitting it. A pane of glass allows light to pass through it without changing its frequency (color) or scattering it because of its crystal structure - it doesn't have less \"stuff\" than an opaque sheet of paper. Atoms in glass may absorb and re-emit that light a bunch of times, but it's transparent to us because the light coming out still has mostly the same information as the light that went in. The paper just reflects (or absorbs and re-emits at a different frequency) most of the light hitting it, destroying whatever information the light had. So.... the idea of matter as stuff that exists in otherwise empty space is really something we perceive at our scale, and not really something fundamental about existence. Matter and energy aren't fundamentally different either, and most of the mass of your body comes from the energy holding your atoms together. Crazy, huh? *To push the electron clouds of the atoms in your skin into the electron clouds of the atoms in the floor you stand on would require the kind of force that creates neutron stars. On the other end, neutrinos stream through earth and your body by the trillions all the time, affecting nothing because they have no EM charge and just don't interact with your atoms."
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mseuk9 | What is the "silver squeeze"? | Economics | explainlikeimfive | {
"a_id": [
"gus7o41"
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"text": [
"The \"silver\" refers to the metal, while \"squeeze\" refers to a short squeeze. The basic idea is that commodities such as metals are sold in the same way as stock shares, and the idea of \"buy low, sell high\" holds. If you think silver is going to get more expensive then you buy now and sell at the higher price. If you think the price is going to drop you sell what you have... but what if you don't have any and want to make money anyway? What you do is something called \"shorting\". You borrow the silver from someone (for a fee) and sell it immediately at the current price. Then when it goes down in the future and you need to return the borrowed silver you buy it at the current price and return it. If you do this well the difference between what you sold it at and what you bought at is enough to cover the borrowing fee plus make a profit! Now the problem is that if you do such a \"short\" then you need to get silver to return what you borrowed. You *need* this silver, whatever the going rate is. If a bunch of people are needing this silver then those who have silver can \"squeeze\" the market by just holding onto what they have, refusing to sell. This will drive the price higher as the short contracts become due, making those who squeezed a bunch of money and losing those who shorted tons as well. With Covid a lot of people got nervous and started to buy up gold and silver. Now the scare is starting to taper off and the price was expected to fall back to normal, meaning lots of shorts were happening. Then the silver market started to get squeezed..."
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msgkkr | What is dynamic range in music? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"It's the difference between how loud and how soft a song gets. Does it stay just loud, does it just stay soft, or does it have changes in how loud or soft it is?"
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msgmfz | How can choosing pictures of certain objects (stop signs, cross walks, cars, etc.) prove that you are not a robot on websites? | It seems weird that to prove that I’m human I have to look for certain objects or check a box. Why is that? | Technology | explainlikeimfive | {
"a_id": [
"gusgoia",
"gusggwn",
"gusge5a"
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"text": [
"The choosing pictures isn't really to check if you're a robot, it instead helps with gathering masses of data for self driving vehicles. Whether you are a human was already decided in the background, depending on a lot of different factors that google doesn't wanna give out because otherwise botters could use that. Remember when it was words? Similar thing, one word was the check, the other for Google's digitalizing of books. Word and a house number? For google maps. Edit: some additional bits Captcha, the system that is used for checking whether you're human or not, stands for \"Completely Automated Public Turing test to tell Computers & Humans Apart\". And there are several ways to get around these, there are programs out there who are able to solve these tests successfully and seem human, but there have also been instances where humans have been paid to solve Captchas all day long.",
"Because how bots select images on those questions can be detected as automated by the website. People tend to wander with their mouse, and can pretty easily tell the difference between a traffic light and a street light at first glance. Bots tend to be predictably mechanical in the choices they make.",
"It less proves it so much as makes it highly likely. Humans have many millions of years of evolution behind highly advanced object recognition. Our brains being able to tell the difference between a tiger and a vaguely tiger-shaped rock is the difference between life and death. Computers can distinguish between objects too, but in order to do it with a high degree of accuracy (especially when you're not trying to compare apples to battleships) it requires a fairly high degree of training and computing power. Can computers choose the 3 images out of 9 that have a fire hydrant in them? Absolutely. Is it a deterrent to people trying to brute force websites when you're effectively multiplying the amount of time and/or computing power required by 100x or more? Yes."
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mshaje | Why shouldn't you mix your drinks? | Biology | explainlikeimfive | {
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"That advice is not based on anything scientific. The only thing that determines how drunk you get is the amount of alcohol that you consume. It doesn’t matter at all whether that alcohol is consumed via beer, wine, cocktails, or hard liquor.",
"The catchphrase people often use is ‘beer before liquor never been sicker, liquor before beer you’re in the clear.’ The thinking here is that because it (typically) will take a little while to drink a beer, you won’t ‘feel it’ right away. If you do shots of liquor before you feel it, you may overdrink because you aren’t feeling it yet. If you have liquor/shots first, you’ll feel them more rapidly, and then having a beer will ‘spread out’ the feeling so you won’t overdrink. All that being said, drinking in the ‘wrong’ order won’t necessarily make you sick, it’s more about learning your own boundaries with different types of alcohol."
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mshfme | Do scientists really know what the core of planets and stars are made of? | Earth Science | explainlikeimfive | {
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"We have a pretty good idea. Our knowledge of the Earth's core is based on a few pieces of information: - It must have a certain density, because Earth's mass and volume are known. - It must be made of relatively common elements, or there wouldn't be enough to form such a large object (the core is approximately as heavy as the Moon) - It must be highly electrically conductive, because Earth has a magnetic field. - It must be a pretty exact amount of \"springy\" because we can observe earthquake waves bouncing off of it. - It must be made of heavier stuff than the other components of Earth (in particular, the silicates that make up Earth's surface), because it sank to the bottom of the once-molten planet. The combination of these constraints makes us pretty confident that the Earth's core is mostly iron, with some nickel. Iron is common, heavy, conductive, and rigid enough to produce the properties we observe. ----- Stars, on the other hand, are constrained by our understanding of particle physics and the observed frequencies of the elements they produce in the cosmos. We know that stars are made almost entirely of hydrogen early in their lives, and produce other elements through fusion. This means that only elements producible through fusion should be common in stars, with heavier and hotter stars producing heavier elements (because it takes progressively more energy to cause fusion the higher up you go). This means that light and young stars, like our Sun, must have cores primarily of hydrogen with some helium produced by fusion. Heavier stars fuse heavier elements, up to carbon, oxygen, neon, silicon, sulfur, and ultimately iron (all of which are common elements in the Universe). And because heavier elements exist, we know that some process must produce them, and stars are the only plausible mechanism based on our current understanding of the universe. In fact, there are *two* processes: the s-process in the core of very large stars and the r-process that occurs during supernovas. Knowing how much of these elements are produced tells us a lot about the inner conditions inside stars, because we know how long they live and how fast elements are produced at certain temperatures and pressures. Actually, in one case, we discovered a new particle physics phenomenon because we knew it *had* to exist for stars to work the way we know that they do (and it turned out that [it does indeed exist]( URL_0 )). More recently, we've been able to observe supernovas directly, which has given us more information about these rarer and less-well-understood processes.",
"We have a really, really, really good idea. We're not gonna be 100% sure about the exact numbers, but we're gonna have a really good estimate. We use different wavelengths of light or xrays or radiowaves to measure how quickly they travel through different materials, which gives us a really good idea of how much of that material there is. We measure all those things on Earth and then approximate based on their gravity or atmosphere or whatever. If there is some unknown material, we won't be able to measure that. And because they're so far away, we might be off by 0.0000001% here or there, just based on the math."
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mshkr9 | How do hackers find holes? | When I see black hats exploiting gaps in security, I have to wonder, how the hell did someone find this? Is there an algorithm? I would think the white hats would have the algorithms too? Even in video games, how do they find such obscure holes in professional programming? | Technology | explainlikeimfive | {
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"\"Professional programmers\" make mistakes all the time, because there is far more need for people who can code even fairly badly than there are people who are good at it. Companies will sometimes spend tens of thousands of dollars in sourcing costs to find one mediocre software engineer. There are certainly common approaches. For example, it's a very bad idea to store users' passwords in a database, but tons of shoddily-written websites do. Many websites also have much more information exposed than you probably think, and hackers will poke at that information to try to find places where it exposes something it shouldn't. For programs on one's own computer, one can use a program that lets them just look at the computer's actual memory and watch when certain values change. If you pick up a health potion and the value at memory address 0x4a89b92d changes, well, that's probably where the game is storing your number of health potions. So you change the value at 0x4a89b92d to 99999999 and see if you get a bunch of potions. This is just a very basic summary. Finding weaknesses like this is a whole subfield of programming and engineering that tends to attract extremely smart and extremely technical people. There's a ton of security talks on YouTube that are relatively accessible and pretty interesting, if you want to know more!",
"Every time someone closes a security hole, a new one is found. Even at companies, who do security well and try to seal every known exploit, new vulnerabilities are constantly being found. Sometimes the company will find them before shipping the software. Some even have dedicated penetration teams. But sometimes they are found in the wild. You cannot underestimate the tenacity of those who want to exploit your software and the creative ways they think to do so. In many cases, companies don’t have dedicated security resources. Most programmers don’t learn much about security in school. Their job experiences won’t always teach them the right ways to do things. They may have never been in a high-risk environment and needed to think about security. All that adds up to plenty of attack vectors."
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mshqqq | A person passes over half of their genetic information to their child. The child then passes a quarter of that to their child. The proportion of the original person's DNA gets smaller with each subsequent generation, but does it ever reach a point where there's nothing left? | Biology | explainlikeimfive | {
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"It's complicated. So, the good news is, a small number of female genes will always be passed on down the female line. This is something called mitochondrial DNA. Sexual reproduction only applied to nuclear DNA - DNA contained in the nucleus. Mitochondrial DNA is not in the nucleus, it's in a separate part of the cell called the mitochondria, and you get all your mitochondria from your mother - they come with the pre-fertilised egg cell. So as long as each woman in a lineage has at least one daughter, that mitochondrial DNA will always be passed on down the generations. Sons won't pass on the mitochondrial DNA though cos sperm get rid of all their mitochondria just before launch. And because mitochondrial DNA is always passed on completely, every single human on earth can trace their lineage back to a single prehistoric human we called \"mitochondrial Eve\". The mitochondria of every human alive today are the same mitochondria as mitochondrial Eve, give or take the occasional random mutation. Similarly, men will always pass on their Y chromosome unchanged to male offspring. Y chromosomes are necessary to produce a male child, and they can only be gained from male DNA. The Y chromosome is integral to male-ness, on the genetic level. If you have one you're male and if you don't you're female, give or take the occasional developmental disorder. That Y chromosome is passed on to 50% of children on average, and any male child will have it. So as long as a male lineage keeps having sons, that Y chromosome will keep being passed on. And just like mitochondrial eve, that means that all human men alive today can trace their Y chromosome back to a single prehistoric male human called Y-chromosome Adam. Although for the record, despite their names, Mitochondrial Eve and Y-Chromosome Adam were separated by several thousand years, and were the result of two separate genetic bottleneck events on the human species (events where the available gene pool is drastically restricted). So no, it will never reach a point where they're *nothing* left, except in the case of fathers and daughters, as daughters don't pick up that Y chromosome and therefore will eventually end up having their X chromosomes diluted by endless generations of sexual reproduction. However, it's also a bit more complicated than that. Genes aren't inherited as just a direct proportion of the whole. Genes are packaged into things called chromosomes. We have 46 of them (arranged into pairs, like 1a 1b, 2a 2b and so on), and we pass 23, chosen by pair, on to each child. Any given chromosome has a 50% chance of being passed onto a child. That's not the same thing as 50% of one origin of DNA being passed on. It's theoretically possible for every single one of those 23 chromosomes you give to your child to end up in one of your grandchildren. It's also theoretically possible that none of those chromosomes end up in a grandchild. The chance is extraordinarily low (0.5^23) but it is still there. So, *on average* your grandchild will have 25% of your DNA, but any given grandchild could have as little as 0% of it or as much as 50% of it. Plus because chromosomes are packages, the minimum un-dilutable quantity is 1 chromosome. Once you get to that one chromosome point, it's just a straight 50/50 chance. That's not going to get halved again, it's just a 50% chance of having 2.17% of your DNA and a 50% chance of having 0% of your DNA. Of course, on average those children will have 1.09% of your DNA, but that's because half will have none and half will have 2.17%. There's also another thing called Crossing Over by which chromosomes exchange genes with their paired chromosome, but that makes this so complicated that it becomes hard to explain and the effect still ends up roughly the same anyway.",
"Yes, because DNA has a finite number of genes in it. Your full genome contains about 6 billion base pairs (the smallest unit of DNA information), meaning that on average there will be less than one left after at most an average of log2(6,000,000,000) = 32.4 generations, or about 800 years. This is slightly (well, okay, grossly) oversimplifying, because genes aren't passed *quite* independently of one another, but it's a good enough back-of-the-napkin estimate. This would imply that most people who lived before about 1200 AD have not passed any genes to modern humans (they may have living descendants, but none of them carry their genes). The main exceptions are the Y chromosome (you always inherit the same one from your dad if male, because he only has one to give) and mitochondrial DNA (you always inherit mitochondria from your mother). In those cases, aside from mutations, your genes will persist as long as you have male-line or female-line descendants.",
"Technically yes, but actually no. True, there is a finite number of genes in the genome, so at some point none of the original genes would remain. However, this will not happen for 2 reasons: 1. Number of humans is not doubling each generation. At some point, both parent of new children would be distantly related to the original person in question. 2. The original person is not the only carrier of a given copy of gene. At some point, his descendants, who \"lost\" original copy of the gene will have their children \"regain\" it from the other partner.",
"I'm a little confused by one thing regarding some of these explanations. So let's say that with each generation, the DNA passed from you is halved. What is the assumption then of where the other half comes from? Other people, yes? So far enough down the line it is assumed that my DNA is no longer passed on, but then whose is? When I pass DNA, it's not MY DNA, it's a combination of my parents who are a combination of their parents, etc. So even if in miniscule amounts, that would imply I must necessarily still have some DNA from every ancestor, ever. If I'm not mistaken someone pointed out that this is true with the X chromosome, through mitochondrial DNA but some people have neanderthal DNA and we've traced back to a common male ancestor some thousands of years back, so the same must be true of the Y chromosome as well. Therefore none of this is my DNA, or even my parents DNA, it's a recombination of DNA from the 'first population' of homo sapiens. Alternatively, it's all mine the moment I'm born and while I pass on my DNA, it stops being mine as soon as my child is born so no one ever passes DNA beyond one generation. No?"
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