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bkyrt7 | What is the Iron Dome, what does it do, and how does it work? | Technology | explainlikeimfive | {
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"Its an anti missile system. It uses radar to sense and track incoming missiles and then fires a missile at that missile to destroy it before it hits its target.",
"It's like a mosquito net. It doesn't show mosquitos inside. You're protected by a net which is in the shape of a dome. The net is imaginary And every time mosquitos come I've my defense system which will hunt the mosquitos down. The defense system is like small army for me. Each unit has a range which happens to be like a dome. They sent their anti mosquito missile and follows it and shoots it down before it enters my area."
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bl0t8k | Open vs Closed system? | I know that open systems can interact with other systems and closed does the opposite, but what does that really mean? Can you please give me an example. Thanks! Edit: In terms of computer systems (Information System Structure) | Technology | explainlikeimfive | {
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"**Open system:** Windows can be installed on pretty much any hardware, third party developers can make modifications to it (e.g., by making a computer game that runs on Windows), and Windows can interact with other types of operating systems (e.g., MacOS). **Closed system:** The US government develops a system to control the launch of nuclear weapons. They want it to only work on official hardware, they don't want anyone else to make any modifications to it, and they don't want it to interact with any other systems. These are relative terms. Linux is more open than Windows, which is more open than MacOS. As a bonus, **open source** means there is a license that says anyone can study, change, or distribute software for any purpose. It's the ultimate open system."
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bl16yf | Why smartphones don't have paper white screens so you can see them better in the sun? | Technology | explainlikeimfive | {
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"Paperwhite is a type of electronic ink screen that uses tiny magnetized balls to show pixels on the display. For reading, it is perfect. Text and black and white images display with a decent resolution and minimal issue, but it's next to worthless for video or color. Trying to make a phone with a Paperwhite display would limit the usefulness of the device to that of an early-model phone and eReader.",
"The sort of electronic ink screens have a few problems preventing them from general use. They way they work is by suspending white powder in tiny capsules of black oil (or the other way around) and using electric fields to move them forward or backwards. Because something is physically moving, there's a limit on how fast it can go. These screens really can't display video very well because of that, with a slow refresh rate. These screens also have issues with color. Color e-ink displays do exist, but they're much more complicated and expensive. Because there are physical capsules of oil, there's a limit on how small these capsules can be. So there's an issue of resolution too."
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bl55e2 | How come some motion capture suits have white balls on them and others have a bunch of black-and-white circles? | Technology | explainlikeimfive | {
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"Programmatically they are very similar. Circles are used, because a circle is a circle at any angle. Circles are easy to resolve in code, because each pixel just yields to the center based on pixel averaging. The top example looks to be creating an entire virtual environment, where the background will be created along with the foreground characters. Since nothing has a basis in reality, the big white dots are easier to locate against the green screen and black background. So it uses balls, because it is easier to use and have no impact on the final product. The second is an augmented reality, where the background will become part of the final product. Having white balls would block leaves and branches if they were external balls. Having them integrated into the suite, the character only can be replaced."
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bla1od | - How are blockbuster movies kept off the internet before disc/digital download release? | You would think in this day and age a computer hooked up at a movie theater by a mischievous employee could easily rip or piggyback off of various display cables. What stops this from happening? | Technology | explainlikeimfive | {
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"Back when I was a pirate in the 2000's it wasn't uncommon for me to have a copy of a movie before opening day. There's always a leak. Back then I found them on Usenet.",
"Well, they're not, but there are some techniques to try to prevent this. One is that screener copies (copies sent to reviewers or film festivals ahead of the premier by big studios) will have a watermark embedded in the video with some identifying information about who received that copy. Obviously it can still be leaked but the leaked version can be traced back to who leaked it, and that lets the studio know not to release early to that person in the future. There's [a new company]( URL_0 ) that's doing a similar thing but using blockchain technology to make each copy if the film unique and traceable. I don't really know how this works but it looks like it could potentially make this tech more affordable for small filmmakers."
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bla51l | Why is power over ethernet possible? | Technology | explainlikeimfive | {
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"Two main ways: 1. Simply take advantage of unused wires and send power over then. Ethernet cables have 8 wires organized into 4 pairs. At 100 Mbps, 2 pairs are unused. At 1 Gbps though, all 4 pairs are in use, so another method is needed. 2. Ethernet uses differential signaling. The exact voltages on the cables doesn't matter to the receiver, only the difference in voltage between both wires in a pair does. So to ethernet, 0 and 5V and 10 and 15V are exactly the same thing -- 5V of difference. Pairs are twisted together and the idea is that if say, some sort of interference induces an extra few volts into the signal, both wires will be equally affected, and the difference between them will remain the same. So POE runs one pair as 0/5V while the other as 48/53V. Then at the other side you can extract power from the difference between pairs. [See diagrams here]( URL_0 )"
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blqg45 | What's the difference between a Samsung "fast charging" plug and a standard iPhone one? Is there any science to it or is Samsung just trying to shoehorn my money into their pockets by limiting the amount of power its consuming? | Title says it, I have to lug around this bulky plug anywhere I want to have my phone charge faster than 22 hours for a full charge, while my girlfriend can plug her iPhone into pretty much any usb. Is there science behind it? Because it seems like the power source is the same. | Technology | explainlikeimfive | {
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"The power sources are not necessarily the same. Yes, they'll all provide 5V over the USB connection, but phone chargers are often limited to 1 Amp of current \"draw\" and tablet chargers/\"fast\" chargers will allow current and voltatges above the USB specification. The most common is 5V @ 2.1Amps, but the Samsung ones can take it up to 15V @ 2.1Amps. Look around, you should be able to find a reasonably sized charging plug (wall power - > USB) that will output 2.1 Amps. That should functionally be identical to a Samsung Fast Charger."
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blrkef | How can a secure wireless (or other) connection be established when the initial communication to establish it is not secure? | My basic understanding is this: two devices initiate communication, and agree on a secret code to keep others from listening in on their conversation. What's to stop everyone else from listening in while the secret code is established, allowing everyone to understand it? What am I missing here? | Technology | explainlikeimfive | {
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"Before we established a huge public key infrastructure, a protocol called the [Diffie-Hellman key exchange protocol]( URL_0 )was created which enables two parties to generate and secretly share a private key over a public channel which can be used to encrypt future communications. In a nutshell this protocol uses math to generate a key that would be very improbable to guess from just looking at the numbers exchanged but can be computed by both honest parties."
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blrryb | Why does sometimes a youtube video buffers in the middle forever and I have to reload the page and skip to that part to have it work? | Technology | explainlikeimfive | {
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"You are queued up waiting for something that isn't arriving. It's like being in the slow lane at the grocery store and deciding to jump to another checkout lane.",
"Your adblocker could be blocking an ad that is supposed to show up at that point among the other things mentioned."
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blsplu | Even before colonialism, why were European and Asian countries typically more advanced than African? | We hear all the time of European and Asian history with their technological advancements, is there any reason why these didn't happen on the African continent? I'm talking about pre 1800 Europe dividing up Africa and conquering and destroying everything. | Technology | explainlikeimfive | {
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"ELI5: Answer, your question is incorrect. History didn't happen that way. & #x200B; ELI20 Answer: So lets go over a few things. & #x200B; Pre-1500 West Africa was more advanced than Western Europe. The reason we know the name of Timbuktu to this day is because of how wealthy it was. The great library at Djenne is still being excavated to this day. It was the wealthiest and most military powerful empire in the Muslim world. & #x200B; That region experienced its own \"Fall of Rome\" level dark ages at just the wrong time. 1.) the famed Mansa Musa was the original scheming Vizier and convinced Abu Bakr II (I think it was the second) to take the massive Mali fleet and try to sail across the Atlantic in search of the new world. Yes this is pre-columbus but this wasn't that crazy. People knew there was land over there because there was a Bishopric in Greenland and they knew Markland (Labrador) existed and even had converted a handful of Native American's to Christianity in the thirteenth century (according to church records). Trade winds don't work that way, both waves (including the second one that Abu Bakr II personally lead were lost at sea. & #x200B; Mansa Musa then cemented his newly found reign by going on a lavish pilgrimage to Mecca and spending so much money that gold was devalued in Egypt for 7 years after his passing. Mali had more than half the western world's wealth but still needed a loan to get back. He figured no problem since they controlled all trans-sahara trade so he'd just raise prices on gold, slaves, and salt. Problem: Lacking a fleet the portugese started poking around and offering competition, LOWERING prices. Solution: Sell even more slaves. Send your client state of the Sonhai to go raid deeper inland then use your forces to raid and sack the Songhai and sell their wives and children as slaves on bulk. Problem: The sonhhai were the WARRIOR client state and ended up overthrowing Mali New Problem: The songhai were not skilled administrators and didn't know how to run their new empire Solution: Ask your friends in Morocco for help New Problem: Seeing they were weakened from their war, Morocco invades and wins. New New Problem: Morocco also has no idea how to govern a state this size and takes what isn't nailed down and retreats. & #x200B; West Africa becomes a bunch of dark ages shattered mini-nations. Still they have a tonne of wealth and make a new fortune selling slaves to Portugal which sets up shop (along with other Europeans). They keep Europe at bay until Britain industrializes and wants materials that African states have. This is one of the reasons Britain starts halting the Atlantic slave trade. Morals are nice, but money talks and crippling the Atlantic slave trade starves African states of funds and allows them to be conquered in the Scramble for Africa pretty much as soon as slavery is done with (the late 1800s). & #x200B; This is all a narrative account and there is a LOT of deeper nuance and timelines and alternate reasons and new context that make this even more complex. & #x200B; Think of this as the Bohr Atomic Model of African history, wrong, but accurate enough to get a grasp on more or less what is going on.",
"Ya. Agriculture. Basically most of africa is bad for farming, meaning people kept living hunter gatherer lifestyles. Europe however is good for farming, people got together in towns and cities, had easier lives and had more time to pool knowledge and resources, ending in technological developments. Thats the ELI5 version. Its also why when western nations arrived in new countries, they tended to wreck the populations with disease.",
"They really weren't until the Early Modern period, and even then not really if you include northern Africa. But Africa faced several issue that hampered the development of what we call \"high cultures\": * many places in Africa are pretty bad for agriculture as the continent lacks mountain ranges. A lack of mountain ranges leads to a lack of predictable rainfall, and without predictable rainfall you can't do agriculture. No agriculture means little to nor surplus, which means no cities, which means no goodies that urban socieities enjoy, like social and technological exchange * now you don't technically need agriculture to become a powerful empire (just ask anyone living on the Eurasian steppe from ca. -500 BCE to 1700 CE), but unfortunately for most of southern Africa horses just can't deal with the climate and parasites down there. So no raiding the rich trading cities on the coast for them. * still, where there was a secure supply of water, cultures sprang up. Mainly along the northern and eastern coast; along the Nile, Niger and Kongo; and on the African Great Lakes. However even the great rivers of Africa, excluding the Nile, have the problem of not being shippable. Which, again, can be explained by the large-scale geography of Africa. The continent is rather smooth compared the Eurasia which is getting crumped from multiple direction, thus leading to lower slopes, thus leading to slower moving rivers, thus leading to shallower streams. *Africa is also rather short on usable lumber. If you want to turn a tree into a house, you want that tree to be as straight as possible so that you can cut it into many nice and straight planks. There's a reason central Europe removed so many of it's mixed coniferous forests with coniferous monocultures. Pines and the like just shoot straight up into the sky, making them extremely easy to work with. African trees however largely look like [this]( URL_2 ) and [this]( URL_1 ) and [this]( URL_0 ) - good luck working with such winding trees. Though again, not a problem for northern Africa. In short, Africa is playing on hard mode. Still, we should not forget that the continent produced a person that casually ruined the economy of every city he visited by virtue of being the richest person in history (Mansa Musa I of Mali), had cities that were important cornerstones of the Indian Ocean Trade (Mogadishu, Mombasa, Zanzibar, Kilwa Kisiwani), and of course built the one wonder of the seven wonders of the ancient world that still stands (the pyramid complex at Gizah). > I'm talking about pre 1800 Europe dividing up Africa and conquering and destroying everything. Africa was divided in 1885 **In short:** Africa wasn't really any less advanced than the rest of Eurasia for most of history. But even in times it was, it was a result of Africa basically being hard-mode for civilization building.",
"Depends what period you're talking about. Egyptian civilization was pretty advanced for a long time. The Mali were pretty advanced for awhile. History is full of civilizations that rise past the others than fall behind for any number of reasons. If you're asking why African civilizations didn't invent gunpowder or something, it's a more cogent answer. But I think our notion of \"advanced\" has a lot of myths and frankly racism built into it. Not because we ourselves are racist but because we don't realize that our expectations and understanding come from racist sources. For example, the idea of the Native American \"Savage\" is very false. Europeans claimed natives were uncivilized and pointed to their lack of agriculture. Truth was, many abandoned their farms because they were fleeing diseases brought by Europeans. Central and South Americans also did indeed have large, stone cities and intricate knowledge of astronomy.",
"Rivers, mostly. African countries located around rivers were typically far more advanced than European and Asian ones (with Egypt being the obvious example but another one figured out how to do c-sections without killing the mother centuries before anyone in Europe or Asia), but compared to the size of the continent Africa has a tiny amount of rivers compared to Europe or Asia which drags down the average (and reducing local competition, which is why their weapon technology wasn't quite up to the task of repelling colonizers). All the areas without a river or other large source of all-year-round fresh water in a single fixed location didn't have the option of creating a fixed city for long enough to work out the technology (aqueducts, irrigation, mechanical wells) they'd need to create a fixed city."
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blsqjs | Why do some PC screens appear to inverse colors on the screen depending on the viewers angle? | For example, looking at a Lenovo Thinkpad from an angle about 45 degrees from parallel to the screen makes the image appear inverse without colors. | Technology | explainlikeimfive | {
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"This is caused mostly by the TN LCD's, or Twisted Nematic. These LCD's are cheap and energy efficient, but suffer from poor viewing angles due to way that it bends light through different filters to achieve different colors, or to block light. When you view the display at different angles, you can see past these filters and see the different colors that are supposed to be hidden. & #x200B; IPS and VA LCD's do not have this issue, though they can suffer from slightly more dim images at sharp angles.",
"A (possibly unrelated) fun fact: this also works for black and white film negatives. Look at them from the right angle, and the light bouncing off the emulsion makes it look white and you can see the positive image. I used this trick in the darkroom back in the day."
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blt4r1 | how does a heads up display, display the image sort of not as a reflection but far back floating in the air? | Class presentation soon and this is still black magic to me. | Technology | explainlikeimfive | {
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"I think the comments so far are missing what you are asking. HUDs are unique in that the imagery appears to be floating further out in front of you than a reflection like what you'd see in a car window. Mitary HUDs (and those red dot sights you see on some weapons) use something called a collimator to focus the image at a distance. By focusing the image further out, a pilot (or shooter) can align symbology or a reticle on distant objects. If you Google \"collimator\" you can read more about how they work. Simply reflecting something, like those cheap GPS \"HUDs\" doesn't focus the image further out, forcing you to shift your focus near and far."
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blt7tt | How are old recordings converted to new formats? | Once a song/video has been recorded and stored using particular technology, when a new form of storage develops, how is the content recreated into the new format? For instance, music in the 80s was stored in cassette tapes, then CD, then digitally (I might have missed a lot of steps). How would a recording on tape be transferred to a CD, how would it be transferred from a physical format to a file type? | Technology | explainlikeimfive | {
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"The studio mix down and mastering was recorded to a high quality format. In the past this was analogue tape. ie 2\" reel to reel tape This was then duplicated to the delivery medium. Ideally, when going to a newer delivery format, they go back to the highest quality version available. Sometimes it's the mastered version, sometimes the stereo mix (pre-mastering) and sometimes the studio multi-track."
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blu5wv | How do thief's use skimmed credit cards in person? | I recently had my credit card skimmed for the second time. While working it out with the bank, it was found that the skimmer used it in person rather than order things online. Given that I still have my credit card, how did he/she actually use my card in a store? Do they make their own cards or something? | Technology | explainlikeimfive | {
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"You can use a mag strip reader/encoder. They're dirt cheap and easy to get. The person who used it probably wasn't the same person who actually stole your numbers. Thankfully merchants see fraud as a cost of doing business and are pretty good about getting your money back.",
"They can scan your card and take all the info from it. It’s quite easy to replicate the card physically once you have that info. Think how quickly a hotel can make a new key card to get into a room. It’s the same type of technology to reproduce a decoy card swipe strip. Generally they won’t make a physical copy as it comes with increased risk while using it. Security cameras recording you, being found with the copied card on you, and the simple cost of producing a physical card keep most people from making physical copies."
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blvw1e | Why does Google Chrome need so much RAM to operate? | Technology | explainlikeimfive | {
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"It doesn't. It only seems to consume an inordinate amount of memory because it uses memory if it's available. If you have 2 computers with the exact same specs except for the RAM and loaded the same websites chrome will use more memory on the system with more memory to make it feel snappier. The other computer will max out it's memory and either store some information on the hard drive or wait until you activate a tab before it starts downloading information from the website.",
"Google chrome likes to claim how fast it is. One of the best ways to make a program fast, is to keep everything in ram. The other problem with google and many other tech startups, is the programmers working for the company are all younger. Younger programmers didn't grow up conserving ram. It's a lot like my parents were depression era kids and they conserved everything. I grew up programming on mainframes, where a meg of core cost as much as 676 brand new chevy malibu's of the same ere, so older programmers just learned to do more with less. Its hard to imagine an entire university computer science department could have functioned with just 32 megs of core and still had enough left over to sell time and make a profit. Wasteful is what it is."
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blzym0 | How do heart surgeons keep patients' blood pumping during surgery? | Like let's say a patient is getting a heart transplant How do they keep blood pumping through the body while the hearts are getting switched-out? Or even like a normal heart surgery like a coronary bypass. Do they meddle with the heart while it's still beating? | Technology | explainlikeimfive | {
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"There’s a special machine that pumps blood in place of the heart. It has to be set up with tubes placed in specific locations in the heart or major blood vessels. There’s a person called [a perfusionist]( URL_0 ) whose entire job is to run and monitor this machine.",
"They literally use a pump, it's amazing. The machine is hooked up to major arteries and veins and basically takes over the job of the heart (circulating and oxygenating blood). During surgery while Drs are working directly on the heart itself, they paralize the heart so it's still and they can work safely. (The heart moves *a lot* when it beats, it's like a fish in there), they restart the heart after they finish. There are different forms of heart lung bypass. My mom was on ECMO Extracorporeal- meaning 'outside the body', Membrane, Oxygenation...It allowed her heart and lungs to rest after valve repair by taking the work load off the lungs and heart. Basically two big ol garden hoses were attached at her groin (one for blood in, the other for blood out) and it goes into a machine where it's oxygenated and pumped back on thru."
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bm2d6k | Why do gloves, as an example, not work with the touchscreen on my smartphone, but a banana peel does? | Never quite understood this. | Technology | explainlikeimfive | {
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"The banana can conduct electricity as it contains water, the glove can’t. That’s why some gloves have little bits of wire woven into the tips of the fingers to allow electricity to flow.",
"Capacitive touch screens work by your finger sucking up some energy. The screen sees the energy change as a voltage drop. In order to activate it you need something that can draw a little bit of current from the screen. Metal works, but only if it’s attached to another energy sink, like your hand. Insulators do not work. Dunno about the banana. It must draw some current from the screen.",
"Touchscreens work by pumping electrons into the conductive plastic over the screen until no more will fit and they stop flowing. It's like blowing up a baloon until you reach it's limit and can not longer inflate it. A microchip can tell the electrons are flowing or not flowing by measuring the current of the wire they're flowing through. It's like how a Gatorade dispenser will slow to a trickle when the waterline gets near to the level of the spout. When the current gets near zero, they've stopped flowing because the electric pressure level of electrons packed into the screen is about the same level as the electrical pressure coming out of the battery. The screen is at its maximum *capacity* of electrons at this voltage. If the screen were larger, it would have the capacity to store more electrons. It would have a higher *capacitance*. So in theory, you could empty the extra electrons in the screen into the opposite end of the battery and pump them back in again — then measure how long it takes the screen to fill up or empty. It's capacitance is directly proportional to how long it takes to fill. Your body is capacitive too. When you touch a screen, you conduct electricity enough for some of the electrons to dump into you. You're so big compared to the screen, that the microchip notices that it takes **a lot** longer to fill and empty the screen with electrons. In fact, it never really fills up, when you touch it. That change in time to max capacity is how capacitive touch screens work. In order for other objects to trigger them, they must be conductive or capacitive. This explains why they work poorly when moist (water is capacitive), and why small metal tools that are isolated don't work."
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bm4upg | Why does a brand new computer go form lightning fast processing to the eventual slow and sluggish processing? | When you get a new computer, phone, or tablet, everything is fast. It boots up fast, it opens apps quickly, and programs run flawlessly. Eventually, the computer start having “hiccups” and slow downs, and after a few years it takes your OS a few minutes to boot up. If the computer is not bloated with software, viruses, and is otherwise “clean”, what exactly is breaking down in the hardware or software? | Technology | explainlikeimfive | {
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"> If the computer is not bloated with software, viruses, and is otherwise “clean”, what exactly is breaking down in the hardware or software? Nothing, computers don't \"slow down\". Not even hard drives to any appreciable degree. Two things happen instead, both are basically software bloat. \\#1. You install SW over time and don't uninstall it, or maybe you do uninstall it but it doesn't work right and you don't remove something. That results in SW installed that takes up disk space, maybe saved files for it that take up hard drive space. More importantly, many applications leave files for something else to process. So you installed AdobePDF reader, that installed a start menu icon (which must be loaded every time you click start), it installed a Desktop Icon (which must be loaded every time your desktop loads, it installed a PDF converter which acts as a printer, it gets loaded every time Windows looks at a printer (to generate that list of printers, and tell you if they are working). It installs a Word Plugin which must be loaded when Word is run, and it installs other things which cause the system to load portions of Adobe at various times. All of this takes space and resources, you might think I'm not using it, but Windows is loading it in case you do use it. That slows things down. \\#2. SW developers assume you have a modern computer. Windows releases new features, they add these features to their programs which takes more resources. They assume the average user has more memory before so they change their SW to keep more resources in memory, this reduces hard drive usage and makes the program faster at the expense of memory. If you don't have that extra memory this will actually make is slower. In the end, you'll find that if you installed exactly what your computer shipped with, it would be exactly as fast as when you bought it. But if you've ever tried it you'll find that all your SW is grossly out of date, so you update it, it adds new features which takes more resources, and that slows down your computer because it can't handle it. Over time as you install more things it just gets worse.",
"As stated by others, older computer get slower for multiple reasons. One of them is because the user, and automatic updates, have installed multiple newer software that require more resources than the computer was designed to handle. The operating system is generally the first culprit. I'll go as far as saying Microsoft is voluntarily pushing updates that will, as a side effect, slow down computers and contribute in making your hardware obsolete. When Microsoft released Windows 10, they pushed a \"free\" upgrade to millions of computers around the world, regardless of the hardware and sometimes against the best interest of the user. This resulted in millions of computer running slower than their factory configuration and eventually encouraged the user to prematurely upgrade to newer hardware in order to fully benefit from the Windows 10 experience. As a slide note, I recently found an old laptop of mine from 2003 at my parents house. I was curious to see if I could recover some old files and started the laptop. The hardware was outdated but the OS (an old version of Ubuntu Linux) was still relevant and responsive despite the years. It was an interesting to take a look at this time capsule.",
"This is a little too complicated to answer easily. . . Buuuut. . . What causes the slowness isn't actually anything related to it's processor. It is related to a different bottleneck, and that's your storage. A hard disk drive has always been compared to a file cabinet. Imagine that you are the OS, and you're getting all of the files you need from this cabinet to start working. At first, it's pretty easy because all the files are nice and organized and all in one place. After a while though, a file may end up having multiple parts in different places in your filing cabinet. Doesn't slow you down too much because it's just one file that's strewn about. Eventually nearly half of the files you need are strewn about and you have to dig through the entire filing cabinet each time just to find a single file. That's a process called disk fragmentation. Happens less and less these days though."
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bm6wva | how do solar panels convert heat to electricity. | Technology | explainlikeimfive | {
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"They don't convert heat to electricity, they convert light to electricity, and they do so by the [photoelectric effect]( URL_0 ). Basically, when a photon with enough energy hits the right kind of atom, it can knock an electron loose, which can then be used for electricity.",
"Solar cells convert light to electricity, not heat - that doesn't carry enough energy. In ELI5 terms, when a light particle (photon) hits the silicon cell, it knocks an electron out of place. The displaced electrons create a current that runs round the circuit and eventually the positively charged \"hole\" that was left where they were gets filled by another electron coming from the circuit."
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bm8azh | Molten Salt Nuclear Reactors | How do they work, and on what principles? | Technology | explainlikeimfive | {
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"Well, no one has answered yet... So I'll try to explain it: To put it simply. An MSR uses salt instead of water to transfer thermal energy. However, instead of having fuel rods like in traditional nuclear reactors, the uranium fuel is mixed in with the salt. This creates an inherently stable reactor, as when the heat increases, the salt expands and pushes into cooling tubes. Even if the reactor gets too hot, it cannot go into meltdown, since the materials are already molten. Edit: Water is still used to generate steam to run turbines, it's just that salt is used to directly extract the heat energy from the uranium fuel. Hopefully someone else who knows more about MSR's will find this post. But this is the basics of what I know about them."
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bm9n9k | how would pilots operating from carriers in ww2 navigate at sea when there are no reference points? | Im thinking flying some 100-150 miles one way then getting into some crazy dogfight and then flying back while your own carrier might be changing position. I know some planes had dedicated radio/navigation guy but also planes with just pilot were used (like wildcat or japanese zero) | Technology | explainlikeimfive | {
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"Everyone who was flying would have a magnetic compass, a watch, and navigational charts to let them figure out where they were. Regardless of if you had a navigational guy to do it for you or not, someone had to figure out the way to fly. If there is only one pilot then it was them who did it.",
"The US used the YE-ZB Navigation System. The YE omni-directional transmitter sent out a rotating signal with a single morse code letter every 30°. Because it was a narrow rotating beam, it was hard to use direction-finding equipment to trace the location. The ZB receiver would then pick up one of the 12 letters, indicating which 30° arc the aircraft was in. The letters changed every day. You could then have a general idea of the direction to fly. If you crossed into another arc, the letter changed and you knew to adjust course. Since it didn't require a directional antenna, it was much easier for single-seat aircraft to use. Unlike a directional antenna system, it was not possible to be on a reciprocal heading going away from the carrier. Since the signal was transmitted in the VHF band (246 Mhz), it was line-of-sight, and could not be received by enemy ships over the horizon. The torpedo bombers, who attacked at very low altitude, often didn't want to spend precious fuel climbing back to altitude, and could not pick up the signal until relatively close to the carrier.",
"> at sea > > no reference points This is incorrect. To add on to u/phage0070's comment, pilots would know where their carrier was headed, and they used [celestial navigation]( URL_0 ) along with instruments and reference points such as islands to find their way back.",
"Well first of all, you're incorrect in that there were no reference points. Planes have compasses and charts. It's not hard to figure out your position knowing your speed, heading, and elapsed time. Plenty of planes also had radio navigation systems. Navigation was certainly a challenge, but not an insurmountable one. & #x200B; A couple of different methods were used. The most common was simply having the planes fly to a per-arranged rendezvous point. The planes would sortie knowing where to meet their carrier before they left. This left the carriers with little flexibility though, because they couldn't change course or speed to avoid threats. If a rendezvous point couldn't be established or maintained, the carrier could radio it's position to the aircraft. This could be dangerous in combat though, since it would reveal the carrier's location to an enemy. Carriers could also use radio beacons. All US carriers were equipped at the start of the war with a device called the YE-ZB. This was a UHF transmitter which transmitted a Morse code letter denoting 15 degrees of a circle. If the pilot picked up a Morse \"M\" for instance and homed on it, then started picking up another letter, he would know he was moving an a tangential course in relation to the carrier; he would then turn and home on the strongest signal."
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bmeel6 | Why are main disks in our computer called C: by default and not A:? | Technology | explainlikeimfive | {
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"The a: and c: nomenclature come from IBM PC and MSDOS. In those early PC, there was one or two drives: floppy drives. They were the primary persistent memory. The first floppy drive was a:. The second one was b: Later on hard drives became an option and were thought of as an accessory after the main floppy drives, thus they were c:. Eventually the hard drive became the main drive in a PC, thus you’re most familiar with the c drive. Cd rom drives came later and are often d:. Dvd drives replaced them later and were still usually d:",
"Because technically back in the day floppy disk drives were booted to first. 5 1/4” and then 3.5”. It was common to boot from a disk drive first for certain applications and the BIOS boots FYI the drives starting with A:",
"A and B were the removable disk drives. It just became an industry standard to have A and B reserved for the two floppy drives.",
"PCs didn't always have hard drives. The original IBM PC that all modern PCs are descended from didn't have a hard-drive at all, it did have two open slots to install optional floppy drives though. Those two floppy drives would be A: and B: on the included Disk Operating System from Microsoft that was included with those PCs. Later model came with Harddrives and those were usually given the drive letter C: to avoid confusion. Nowadays floppy drives of any kind aren't really a thing anymore and in there is nothing preventing you from having a hard drive or network drive or an USB stick as A: or B:. In theory you could even try to put the disk windows lives on at A: Microsoft however is very reluctant to break backwards computability and assume that the users and developers using their software are not complete morons. Any program running under windows should look in som,e variable or other where the maindrive is instead of assuming it is C:, but MS doesn't feel comfortable assuming that the people using their OS won't assume stupid things. So C: for the main disk it still is. many years after that ceased to make sense. Windows is full of small design artifacts that have long since ceased to make sense, but that Microsoft keeps, because it doesn't trust users and developers not to do something stupid. You can't say that this approach is entirely wrong.",
"Wellllll..... Way, way back computers didn't come with a hard drive they came with a floppy drive which was a: then there were really lucky people who could afford 2 floppy drives a: and b:. Then the great c: drive came along....",
"'member floppy disks? 'member the rich kids with 720kb or 1.44mb while you wallowed in 360kb hell?",
"Even when the computer didn't have two floppy drives, the computer acted as it did. When you selected the B drive you got a message \"Please enter the disk for B:\" (or something similar, this all was a long time ago), and you swapped the disks. Then when the computer needed to access A again, you'd get the \"Please enter the disk for A:\" to tell you to swap the disks back. So, in all situations, C: was the first available drive letter for a hard disk.",
"As the other comments have already covered, A: and B: are for floppy disks. I wanted to make an additional add-on to several top-level comments at once: This question tells your age and also tells ours. Understand that we're not telling you of a time in history books; I'm not even 30 years old yet but my early-adopter father had a machine running MS-DOS that had one 5.25-inch floppy drive, two 3.5-inch floppy drives, and a hard drive. [This]( URL_1 ) is literally what the screen would look like when I would use his computer to navigate to the folder to play games as an 8-year-old. Because the hard drive had less than 20 megabytes of storage, I only had less than a dozen games actually installed—I had to pull out of a rolodex-like container the five-and-a-quarter floppy (which was actually floppy) to play [Outrun]( URL_2 ), or the three-and-a-half (which was stiff) to play [Tank Wars]( URL_0 ). Once you put the disk in and started up the game, you could usually take the disk out. The only reason some programs needed to keep it in during operation is because not all of the data would be loaded into RAM yet. However, much more commonly, you had several disks for big programs, and you'd literally be instructed by the computer screen to take the first disk out and put the second one in at times. This is *how* we could have computers that didn't rely on hard drives and worked mainly off of removable storage—we would always be loading programs into RAM each time we wanted to open a fullscreen adventure game or Corel WordPerfect. Computer cases today often don't even have slots for optical discs (CDs or DVDs), let alone the short-lived zip disk (a fat, stubby floppy disk). The only reason the computer I built had to have one was so I could use the CD to install the drivers for my motherboard's USB ports, which is probably no longer needed for any computer I'd build this year. However, so long as we continue to keep hard drives as our main storage to run programs from, it's likely that C: is here to stay. Which leads me to wonder if we're ever actually going to move away from local storage for programs and take advantage of always-connected cloud storage in the future, as the Chromebook is trying to push for."
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bmetbe | Why can’t we just go back to using whatever materials we used before plastic? | Technology | explainlikeimfive | {
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"The cost, really. All of the infrastructure of a our modern society is based on making, molding or using plastic goods. To change it we'd need to readjust... like everything... Theres a reason that we switched to plastics- they're durable, heat resistant and easy to turn into whatever you need. And think of the new/old industries that would need to step up. How many more sheep would we need to make woolen clothing if artificial fabrics weren't available anymore.",
"Dropping an [old glass shampoo bottle]( URL_0 ) in the shower is highly un-fun.",
"We think of plastic things as cheap, but plastic is a better choice for a lot of things. Think about your car and all the parts made with plastic, and then imagine all those things made with metal, glass, ceramic, wood, or leather. We can, of course, make those things but many would be more expensive, heavier, more fragile, poorer insulators, and/or have other negatives compared with the plastic version. The cost, in particular, would be a big factor.",
"Think it was metal mostly. I remember ice cube trays were a multi part metal contraption... Was kind of difficult removing the ice but I do miss it."
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bmf0kg | How does an air fryer works? | Technology | explainlikeimfive | {
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"text": [
"An “air fryer” is just another name for a table top sized convection oven. Instead of immersing your food in hot oil, the fryer blasts your food with superheated air."
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bmjcz4 | What gives an auto-tuned voice that distinctive sound? | Technology | explainlikeimfive | {
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"Think of autotune as a hypothetic lane assist in a car: You're supposed to be in the right lane, but actually driving with one wheel in the left lane. Autotune will move your car to the right so you're perfectly centered. Now if you atually move towards the left lane, autotune will realize that and pull you to the left until you're perfectly centered. On the dashboard, there's a dial that lets you adjust how aggressively it will pull you to the center of the lane. You can set it to 10, and it'll just give you a slight nudge. 1 will aggressively pull at your steering wheel instead. But the dial doesn't stop at 1, you can move it to 0 - which, instead of moving your car between lanes, teleports the car between lanes. So if you move the steering wheel to the left, you'll remain fixed on the right lane, and at some point you're instantly on the left lane. Instead of lane assist, it's of course pitch correction. But the idea is the same: The regular modes of autotune just make sure you hit the notes correctly, but they still sound more or less like an actual human voice. The \"0\" mode completely eliminates smooth transition of the pitch from one note to another, causing the robot-like sound effect now known as autotune."
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bmjui8 | Why people still buy iPhones even if Android phones are useable and cheap? | Technology | explainlikeimfive | {
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"text": [
"Lol you ready for this. You ain't ready for this. And I'll join by saying more users on reddit are android users."
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bml08j | Why does Excel slow down as a process continues | Let's say I am autofilling 10,000 rows of 1000 columns (10mil cells), as I sometimes do. The first 1000 rows go very fast, the next 1000 a bit slower, the next slower... Each row is slower than the one before. Rows 9000-10,000 take longer than the first 5000 rows do. | Technology | explainlikeimfive | {
"a_id": [
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"Software developer, & #x200B; Until we get a developer on the Excel team from Microsoft in here, it's hard to say precisely. What I do know is there's a scripting engine running on each cell, trying to detect formatting changes, or macros or expressions to execute. Every change requires evaluating the whole sheet, so the more cells you populate, the more work to be done as a consequence per cell. & #x200B; My wife is a data analyst and her entire industry lives and dies by Excel, because they're business people, not technical per se. What I do know from her is there are a few switches buried in Excel to turn off some of the auto-formatting and the scripting engine, which is particularly useful if you're just trying to initially populate a sheet, or if you're making big changes and would rather evaluate all your expressions at the end. At your scale, even less, I've seen her max out a 12-core processor. It really doesn't take much in Excel, because it's the wrong tool for the job - I don't know how much more plain it can be made... & #x200B; I think using excel beyond a couple hundred rows is stupid, for performance reasons. You would get much more performance if you used an SQL database. People talk a lot of shit about Access, but it is a desktop SQL database and is plenty up to the job for the scale of the task you're trying to accomplish. You don't need a full fledged enterprise server. A better tool still might be the R programming language, and maybe even in conjunction with a database.",
"Depends on what you're doing. If you're pasting formulas, the formulas in the existing cells are all recalculating every time a new cell is populated. Just set it to manual calculations. Paste in your stuff and hit the button to calculate so it only goes once."
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bmlbjp | Why are most laptops with a 4K display touch-screen? | Technology | explainlikeimfive | {
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"text": [
"Being 4k AND touchscreen is in no way related to each other technically. The feature of being 4k resolution is currently a \"premium\" feature. Most laptops that have this feature also have the \"premium\" feature of having a touchscreen. Think of buying a car with all the features, if it has a sunroof, it probably also has power windows.",
"4k displays aren't cheap. Therefore, any 4k laptops aren't going to be lower-end. Most midrange to high end laptops have touchscreens, as the market segment wiling to pay $800+ for a laptop generally can afford an extra ~$30 on a touchscreen and will be willing to pay it. Therefore, most 4k laptops will have touchscreens."
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bmpwkl | Why do the videos from the early 1900's look like they are being played at 2.5x speed? | Technology | explainlikeimfive | {
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"text": [
"The original hand cranked cameras like the pathé and the bell & Howell 2709 had what was called an 8:1 gear ratio, which meant for every 360 degree crank it would produce 8 frames. There was a song that cameramen would sing as they handcranked, which would result in about two revolutions per second - 16 frames. It would fluctuate, obviously, and sometimes cameramen would deliberately change their cranking speed depending on the scene. Projectors were also handcranked in the early days, and the projectionist would change his/her speed depending on the scene. With the advent of sound, the speed of recording /playback was deliberately changed to 24 frames per second to help with the fidelity of sound. A proper silent film should be played back at 16/18 frames per second, and some criterion versions were transferred that way.",
"Answer: I’m sure someone could explain in more detail but it comes down to frame rate. Movies were filmed at a lower frame rate, I think around 18 fps, and newer movies are filmed at around 24 FPS. So when you play old movies using modern technology the old film looks sped up."
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bmuc82 | How were maps made before the digital age? | Seems like an extraordinarily difficult concept that I can’t wrap my head around. How do they know what they’re drawing or how accurate their drawing is? It’s amazing that those old maps are even as accurate as they are. Cartographers are so cool. | Technology | explainlikeimfive | {
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"text": [
"[Surveying]( URL_2 ). - Take sticks with very carefully measured marks on them, and place them at various points. - Take a telescope-like optical instrument ([Theodolite]( URL_1 )) which can be adjusted vertically, horizontally, and also adjusted to focus at various distances, and which shows you precisely what adjustments you've made. Noting those adjustments tells you the distances and angles from the spot where you are measuring. - Focus it in on a specific marked point on one of the sticks. Write down the adjustments (measurements). - Repeat. A lot. - Take all those measurements that you've done and use math ([Trigonometry]( URL_0 ) and [Geometry]( URL_3 ) specifically) to do some calculations to get all the relevant real-life distances and angles between the places where the sticks were. (Having the right combination of angles and distances allows you to calculate the others, which in turn can help you calculate others.) - Scale all the measurements down by dividing by a chosen factor. - Put a dot on a piece of paper to represent the point where you measured from. - Use a combination of rulers, protractors, and compasses to reverse the process, plotting the scaled-down locations of the sticks from the point where you measured them and each other. - Connect the dots. - In the places that you didn't measure, write \"Here there be dragons!\" and draw your best guess of what a really scary dragon would look like, so that everyone will be too scared to go there and question you. Given decent instruments and enough time, you can make it about as accurate as you want. If you're rushed or your instruments aren't that good, it might not be that precise, but sometimes that's okay, it just needs to be good enough. You can get by with just sticks and string and some way to measure angles and distances if the area being measured is small enough. It's the same process, you're just making sure the string is taut enough and measuring based on chalk marks you made on it or something like that, and measuring angles with a protractor.",
"Basically they made giant protractors and rulers out of chains and smaller protractors. It's actually not that different in concept from how maps are made now when they need very high precision maps for construction that GPS really just can't match. You carefully measure distances and angles from some known point and you keep going from those additional points and then from those points and if you're very careful so your error is very small, you get a reasonable map."
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bmxj0s | why is direct sunlight bad for electronics? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Direct sunlight is bad for pretty much everything and almost always for the same reason: UV radiation breaks down matter. In the case of electronics, they will break down the protective layers of the circuit boards and eventually start digging into the copper tracks.",
"Because electronics heat up in the sun and the heat may damage batteries and circuits in the device."
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bmy6t8 | How do they clean dirty plastic / glasses etc. before recycling? | Technology | explainlikeimfive | {
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"text": [
"I think just melting them down into a molten glass burns off anything that would be on them"
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bmzeuw | Why is Google search web address so complicated? What's with all the complicated numbers and letters? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"URLs can't have certain characters in them, like quotation marks and spaces. When a website needs to use a URL that uses these characters, it replaces them with special sequences of allowed characters in their place. IIRC a quotation mark, for example, is replaced by %22%"
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bn1uth | Why isn’t everything solar powered? | I was gifted a solar powered watch 5 years ago. Never had to worry about swapping watch batteries. After the first solar powered item was made, why didn’t every piece of technology, equipment, gadget etc become solar powered when it was invented? Why aren’t more things being made solar powered moving forward? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"For large scale electronics solar power is nowhere near as efficient other sources of electricity."
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"score": [
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bn2021 | How a speed camera works on a multiple lane road? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Police cameras use radar guns to measure the speed of cars. Radar works be shooting radio waves at the target, and measuring the amount of shift caused by the Doppler effect on the radio waves to determine the speed of cars. The reason they work on multiple lane roads is that radar can be focused, just like a flash light, using mirrors, lenses, lasers, or blinders. The officer can then measure the speed of a car by pointing the gun at at."
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bn62cj | Why is ethernet faster than WiFi? | At my school campus when I speed test with ethernet on school computers I get 100mb/s but when I connect via wifi on my phone or laptop, it's only about 3 mb/s? | Technology | explainlikeimfive | {
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"Imagine taking to a friend face-to-face; in a quiet room; seated across from each other at a table. Now imagine talking from around a corner, in a crowded hallway; during a house party. In the first scenario, you and your friend understand what the other person says the first time, every time. In the second scenario, you keep having to yell, \"WHAT?!?\". Ethernet is like the first scenario. There is very little signal loss or noise. WiFi signals require a lot more resending because of noise and attenuation.",
"Ethernet is not a shared resource like wifi. When you plug into a port that cable is just for you and the switch on the other end. There is no possibility of collisions, and bi-directional communication (send and receive at the same time) is allowed which effectively doubles transmission rates. It's less noisy in an Ethernet cable, making it easier to send more data. You will see slowdown at the choke points if enough systems are using enough bandwidth. While a switch can have dozens on ports, normally a switch only has one connection which either goes to another switch or a router, normally a router. That single connection represents a chokepoint. However, this only matters if enough bandwidth is being used that you reach the maximum bandwitch of that connection. Wi-Fi is a shared resource. Only one system can transmit over a particular frequency at a time. Unlike Ethernet, collisions are possible, so Wi-Fi uses a method to help avoid collisions. If a collision occurs then whatever was sent is lost and needs to be resent. The air is a very noisy place, which makes it much more difficult to send data.",
"Plugging your phone in to chargd is faster than wirelessly charging it on a dock. Wites are just faster."
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bn6vjc | How did we code computer code and operating systems? | Technology | explainlikeimfive | {
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"Code is executed as binary machine instructions in memory. Ever since we stopped programming computers with wires, there has been a way to make a file, or a tape, or a ROM, or load core (Google \"core memory\"). Some ways were bad, manually transforming instructions to binary, or octal, or hex, and then punching them on a tape. The good ways involved taking text, originally one line per paper card, and feeding that text into a program that would give you the resulting binary. Then you put the binary on a boot store and start up the computer. This is still the way embedded computers are programmed, when it's important that they not make mistakes, bare machine programs without an OS."
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bn73wt | if corn has no nutritional value, then how did culture's in South America/Mexico thrive because of it? | Technology | explainlikeimfive | {
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"text": [
"It is not the case that corn has no nutritional value. In 100 grams of corn, there is 18.7 grams of carbohydrates, 1.35 grams of fat and 3.27 grams of protein, and a good quantity of vitamins B1, B3, B5 and phosphorus. URL_0"
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bn7tfx | What exactly is Data rot and why is storing electronic photos on a phone long term a bad idea? | Technology | explainlikeimfive | {
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"1. The storage media uses a physical process (electrical charge for a SSD, or magnetic moment on a HDD) to store the data. On the tiny physical scale that this happens at, external forces can over time disrupt the stored data. Atoms vibrating because they have heat, external electric or magnetic fields, cosmic rays, etc. Thus, if you don't refresh the state of the stored bits, they can eventually flip, and thus corrupt the data. If you refresh the bits too often (millions of re-write to the same physical location) it can get stuck or wear out, just like any other physical thing wears out, making the corruption easier or permanent. 2. There's a tonne of other components besides the storage layer that are between your software and the storage media. It's possible that anything in between can become damaged, making it hard or impossible to access part or all of the underlying data. And any time you copy data from one place to another you could encounter such damage, mutating what got copied. & #x200B; More robust storage formats take up more space to counter these corruptions through effectively redundant copies of the data. But they can only correct so much corruption before the original information is lost. & #x200B; Also, software moves on. Old formats become obsolete. Sometimes you just can't read the data anymore using any software that exists."
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bn8ejp | How is helium collected/made and put into tanks? | Technology | explainlikeimfive | {
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"text": [
"Helium is obtained through fractional distillation of natural gas. It occurs naturally in these deposits, so when the gas is extracted, the helium is separated out and stored. It's next to impossible to obtain it any other way.",
"We can't produce helium unfortunately, but we can separate it from natural gas deposits. Pumping it into tanks is a basically just a process of pushing a lot of in harder than it's trying to escape, so that you can stuff a large quantity in a small, cramped (pressurized) space."
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bnbp05 | How does the Internet work? | Technology | explainlikeimfive | {
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"text": [
"Your computer is connected to your modem. That modem is connected to whatever ISP distribution center that is in your city via cables. That Distribution center is connected to a bigger ISP with larger cables that connects different cities and regions together. That ISP connects with underwater cables across continents to other similar-sized ISP's in other nations. Then it just funnels down in reverse until you get to the other person."
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bnhlwp | Why can't phone screens be dimmed way more so that they are easier on our eyes when it's dark? | Technology | explainlikeimfive | {
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"text": [
"Do you have an iPhone? I can dim mine to where it’s hardy viewable even in darkness. Also, I saw a video not too long ago about a trick you can do to dim it even further."
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bnjqvf | How does noise cancelling work? | Technology | explainlikeimfive | {
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"Active noise cancelling works by the headphones having a microphone on the outside that detects environmental noise, and then speakers on the inside that play the opposite soundwave to cancel it out. Sound travels in waves with peaks and valleys, so if it hits another wave with directly opposite peaks and valleys they cancel eachother out.",
"Here's a [picture]( URL_0 ) for combining two sound waves. When the highs meet the lows, they cancel each other out; that flat line means silence. So, by combining one sound with its **\"opposite\"** sound, you won't hear anything. In noise-cancelling headphones, it has a microphone that listens for outside noises. Then, it produces the opposite sound to cancel it.",
"Sound is a compression wave. Basically something, like a speaker drum, pushes the air and the compression travels to the ear and we hear it. If you drive another speaker in the opposite direction you can cancel the wave and the air doesn’t move and you don’t hear anything. Noise cancelling systems have a microphone and speaker. The microphone records the sound and the speaker produces the opposite sound. Electronic circuits pass signals much faster then sound so if the speaker is closer to your ear than the microphone the timing works out.",
"Can this be done with other information carried on sine waves? Isn’t what we see similar insofar as it’s basically light? In other words, is sight cancelling something that we can do also?",
"Sound is vibrations. If two opposite vibrations hit each other, they can sort of cancel each other out. When I was a kid, I remember being at a friends house who owned a trampoline. To troll my friend, I would try to jump JUST at the right time to take the height out of his jump. This is exactly what happens with noise canceling headphones. Using mics they “listen” and play the exact opposite of that sound."
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bnjx1c | How do street lights know to turn colors when you pull up to an intersection? | Technology | explainlikeimfive | {
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"text": [
"There are sensors on the road. Have you ever seen [those circles covered in rubber?]( URL_0 ) Whenever you drive over them it let's the traffic light know there's a car there.",
"There are two mechanics. 1 is magnetic sensors buried under the crosswalks that tell when cars arrive. 2 is a light sensor attached to the overhanging pole. Although I think I may be wrong on this as I heard somewhere it only covers certain bandwiths for emergency vehicles"
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bnkcf9 | How can online games like first person shooters be so in sync across all users without hardly any delay? | Technology | explainlikeimfive | {
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"text": [
"Fast internet and faster servers. Human reaction times are on the order of 100ms or so. Ping time, which is round-trip packet flight time is often on the order of half that or so. Round trip is therefore on the order of human reaction if you give the server a little time to do stuff. Also, the server only sends back just enough to run the game. For example it may just send back Headshot and some points, and your client has to take care of the headshot animation, credit, sound and then tell the server when it's done because it's not really sync-critical.",
"There is a term \"tick\" - tick is an instance of updating and sending game session information to clients from dedicated server which hosts the game. Tickrate - amount of ticks per second. Most modern games have 20-100+ tickrate. Meaning each client receives data for all game objects each 50-10 milliseconds.Human reaction times from moment when something appears on screen to recognizing that something appeared on screen and starting doing appropriate action to this vary in between 200-400 milliseconds. So 1st thing is that game state updates faster than human reaction time. 2nd thing - whenever client prepares to render frame, it interpolates (finds out approximate) position of game object from last know object position, velocity and other info received on last tick.",
"Reaction time is not a factor. The answer is the games are synchronized by the server. Synchronization means collecting the disparate asynchronous actions from players and resolving them to single state. All the players are doing something a little different for small periods of time and see their own versions of events that will not end up being what the server decides happened. The way the server resolves conflicts is up to the designer. Usually they decide client-observed hits should count, which is why so often players feel like they were killed while behind walls or somehow both players kill each other simultaneously. In games without dedicated servers usually the host of the game just resolves conflicts by saying whatever the host saw happen, happened. This can be very frustrating for players who aren't the host. See: Halo 2/3.",
"You think there is no delay. But even if you would run server and both clients side by side on same machine you would see that there is delay. Not much. But enough to notice. Ofc everything comes down to implementation of prediction.",
"The computer you're playing on makes an educated guess as to where everybody else is and what they're doing. A server run by the games company collects messages describing which users have actually done what, and then sends these out to everyone playing. Your computer then updates it's educated guess with any new information (ie a rocket was just fired)."
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bnkmui | Do Wire Colors Matter? | Looking to build something and the guide for it contains color coded wires. Do I need to buy wires of various colors or are they all created equal? | Technology | explainlikeimfive | {
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"In terms of electrical capacity , all colors of the same thickness are equal. But, there are expectations about what wire colors mean. Usually red or black is hot, white is neutral and green is Earth ground. Are we talking power wiring or signal wiring?",
"As others have pointed out, using the same guage of wire is what matters electrically. However using the right color of wire gives important clues to people that may need to fix what you’ve done. In the case of a small personal project it helps to train yourself for when you are working on non-personal projects.",
"Technically it doesnt matter. But there is an accepted system. (This is for the US.) Hot colors: (120v/240v) Black, Red, Blue Hot Colors: (277v/480v) Brown, Orange, Yellow Neutral: (120v/240v) White Neutral: (277v/480v) Gray Ground: Green or Green w/Yellow stripe. There's also systems in place for low voltage wiring, but I'm unfamiliar with them. What you really need yo pay attention to is what ampacity/voltagr the wires are rated for and whether or not you need to take any deration into consideration.",
"Are you referring to ethernet cables? Romex for your house? Jumpers for a raspberry Pi project??",
"Excepting for different gauges of wire, they should be the same. The color is only on the outer sheath. Usually to help you identify which is which when facing a number of them.",
"For Rpi, the color doesn't matter in the sense of the function of carrying the signal. However, you will soon find that if you work over a few weeks and in a group, that keeping to some color system makes sense. Modules fail and oftentimes your project needs debugging during testing and you may have ideas to improve things after awhile. This is especially true if you're using proto boards. First priority is to use the same colors for the power lines. 3.3V and 5V mixups will damage some modules. Often, you'll daisy chain 3.3V and 5V and keeping them easily identified is good practice. Ground is another one. Then there are serial signals that daisy chain as well. Again making sure all these serial lines are color coded makes for easy debug. You will find more time spent (if you are new) figuring out \"what went wrong\" than actually building most semi-major projects in the first place."
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bnlurn | How do neural networks work? | Technology | explainlikeimfive | {
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"text": [
"Highly recommend the YouTube series from 3brown1blue on this topic. Visual explanation of this will always be better than just text in an comment. URL_0"
],
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bnmrvp | Why didn't vector graphic become mainstream rather than raster/pixel? | This is not exactly a PNG vs EPS argument. I've been working as a designer since four years now and since I work in print, the pixel data available on the net doesn't help much. I find myself converting stuff to vectors a lot of time. Apart from photos, everything else that could be vectorized is converted in my work. You can zoom in a million times and it still won't tear as it is not a matrix rather lines of equations to plot on an artboard. It is also way smaller than its pixel counterpart. Can someone explain why this didn't take off? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"The hardware that will ultimately display or print your work is pixel-based. This means that any vector-based solution requires additional processing before it can be used. This can also mean additional storage/transmission costs. Consider a CGI animated film. Handling it in pixel-based formed is somewhat expensive in terms of storage/transmission/processing. But it's completely prohibitive if you're working vector-based - you'd need a server farm and dedicated fiber to get anywhere near real-time.",
"In the late 80s - early 90s most graphics were vector based and came from ‘clip art’ libraries. Vector graphics need more memory/ processing power to display onscreen but use up less storage space. Maybe as storage space became less of an issue bitmaps became more popular as they could be easily be used on lower end machines."
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bno9f2 | Why are magnets not a problem for electronic devices anymore? | I remember in the 90's/00's you were not supposed to get magnets near electronic devices. All devices also had warning stickers regarding magnets. Today it seems not to be an issue anymore. Many devices have built in magnets, for example to attach a keyboard, charger etc. What has changed that made devices less sensitive to magnets? | Technology | explainlikeimfive | {
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"text": [
"Two main reasons. 1. Before LCD displays there were Cathode Ray Tube (CRT) displays. These used magnets to direct an electron beam towards the phosphorescent screen to create the image. Having a magnet near the monitor could magnetise the display, altering the beam's path thereby corrupting the display. Degaussing features were introduced to resolve this, but it was still possible for enough magnetic exposure to cause permanent damage. LCD displays don't use magnetism or electron beams so magnets aren't a problem. 2. Many older storage media, such as tape, floppy disks and hard disk drives, use magnetism to store the data. A magnet could corrupt the data. Nowadays we use flash-based storage like USB flash drives or Solid State Drives, which store an electric charge rather than magnetic alignment."
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bnqd7r | How do file compression work? Why can't we just infinitely compress a file inorder to make gb to kb? | Technology | explainlikeimfive | {
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"text": [
"Compression works a lot like shorthand. You make shortcuts and special “words” to represent certain sequences. As a super simple example, let’s say a file is 9 followed by 100 8’s. That file would be 101 bytes. But I could say any repeated sequence of numbers is always represented in my compressed file as “\\n\\*X” where n is the number of times character X is repeated. Now my file is 9\\100\\*8, which is 7 bytes. It can’t go to zero though, because the 9 and the 8 are unique and losing either one of them loses the distinctiveness of the file, and the number of 8’s matters, so we need at a minimum 3 bytes to represent the file. In other words, there is always a lower limit to compressed size. It gets more sophisticated, but that’s the jist.",
"If I compressed aardvark into \"a\", no one could work out I meant aardvark as there's no possible method to do so. But I can compress 0000011011000111 into 521233 and, understanding how I did it, it can be worked out. (5 lots of 0,etc)"
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bnugig | How did people wake up on time before alarm clocks were invented? | Technology | explainlikeimfive | {
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"text": [
"There used to be Knocker-Uppers who would go around waking people up. URL_0",
"Body clocks. From being a tradie for 5 years now I get up just before 6am for work. After doing that for a month my body just always wakes me up at around 5:30-6 every morning. It’s not hard to get into a rhythm of waking up around the same time everyday.",
"I don't think schedules were as hectic back in the day. People slept in the dark and worked in the daylight. Things weren't as punctual, i don't think."
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bnz9zb | Why did my friend always have to turn on channel 3 in order to play Nintendo 64? | Technology | explainlikeimfive | {
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"text": [
"I'm assuming you mean that your friend had an older style television and he would switch to Ch 3 to get the N64 to work. Not every TV came with composite inputs (think your red, white, yellow cable) and only had RF tuners (the port you plug your house antenna or rabbit ears into). You could buy a little box that converted the composite input to an RF signal which you could then manually tune into a channel on the TV.",
"On older TVs that had no other way to plug video sources (like a VCR or game console) into them, you had to use a device called an RF adapter to hijack one of the channels. You plugged it in between the TV and antenna. The channel usually could be selected between channel 3 or 4 in case your town had a TV station on one or the other which could cause interference. In other words there was a device that created a channel for the game to play on, and that was usually channel 3.",
"The adapter plugs into the co-ax cable and the signal from that adapter is in the same frequency as channel 3. Some adapters had 2 channel options. [like this]( URL_0 )"
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bo00o7 | Torrents. Could studios sabotage them if they actually wanted to? | Technology | explainlikeimfive | {
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"text": [
"They do try to overload a torrent with clients that you can't really connect to. I forget the term for it, flooding maybe, but essentially it stops people from downloading or reduces speed to a crawl. They can also submit bad files to the major sites so that people searching for a torrent may end up picking a bad torrent instead of a real one. You wouldn't realize it was bad until it had finished downloading. However these methods are pretty ineffective. Major sites have uploader rankings, torrent ratings and comments systems and probably also actively block bad content so it's fairly easy for the \"legit\" version to surface. If flooding is severe then people end up resubmitting the file under different names to create paths that aren't being poisoned, and its difficult for the company orchestrating the attacks to adapt to cover them all.",
"No. Each part of the torrent has provided along with a hash code of that part. If the hashes don't match (which happens if the part was modified), then the part is discarded and downloaded again. There are [other ways]( URL_0 ) of messing with torrents, for example simply by uploading a bad version in the first place.",
"You can't just insert your own data into existing torrents. Than every torrent would be riddled with virusses. They could upload there own faulty file, but that would be downvoted quickly and nobody would get it."
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bo01o8 | How does exposure allow a camera to see into space? | Whenever someone takes a photo of the sky and you can see stars and the galaxy, most people attribute it to a high or long enough exposure setting on their camera? How exactly does that work? | Technology | explainlikeimfive | {
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"text": [
"The reason we can't see stuff on the night sky as well as we would like to is not that they're invisible, it's just that there's so little of their light reaching us that they're indistinguishable from the backdrop. Long exposure on camera sort of gathers up all that dim light and sums it up - with long enough exposure and stable enough camera, you end up with a much clearer view of the night sky (or other cool effects, like tracks of the paths the stars take in the sky for really, really, really long exposure). Edit: I accidentally a word. I blame low blood caffeine content.",
"longer exposure, more light. The night sky is emitting very little visible light. & #x200B; Like a drip of water makes no puddle, but a lot of little drips make a large puddle. Long exposure allows lots of \"drips\" of light to enter the sensor on the camera (or film if it's a film camera)."
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bo0c4a | How come when you open task manager to close a slow program, the program will sometimes suddenly start working again as if nothing is wrong? | Technology | explainlikeimfive | {
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"text": [
"I hope someone who knows some in depth details on this can chime in, but the short version is: Opening the task manager by your standard ctrl+alt+delete is not like starting any other program. It's treated by Windows differently, and interrupts other functions for a moment - that's why it can work even when the OS is otherwise nonresponsive. Sometimes it's enough to give whatever was causing the hangup a push - it depends on a lot of variables and what was actually causing the application to stop responding.",
"When you trigger your computer’s task manager, it runs many background tasks including ones that tell programs to eliminate any cached/temp intensive data so computer can run more urgent tasks such as monitoring or killing tasks and/or cleaning/sorting ram/cpu threads. It acts as the teacher in a classroom full of students causing everyone to behave and not slack in a sense on running tasks and optimize their functions"
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bo0zks | Why is a poor signal strength bad and how, specifically, does it affect my conenction? | Technology | explainlikeimfive | {
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"text": [
"Think of it like you're trying to get water into your glass from a reservoir through a series of pipes. Your signal being weak is like the pipes not being big enough to handle all the water so only a little bit gets through to you, making it take longer for the glass to fill The internet is basically a delivery and retrieval system for lots of little packets of information, when your signal is weak it means the amount of information it can handle is low",
"Poor signal strength can be attributed to your ability to hear a sound. Think of your connection as someone trying to tell you a story, but they're yelling it out as loud as they can, and they need you to (sometimes) yell parts of the story back to them so they know you understand what they're saying. As you get further and further away from them they need to yell louder and louder to get their message through, but you're nowhere near as loud (because they are a cellphone tower and you are a cellphone). So because of this you cannot read parts of the story back to the sender, because you're having a hard time hearing them, or you cannot yell back loud enough to validate the story. TLDR; electromagnetic signal strength is like yelling at someone"
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bo2z0n | Why do PC's need fans or water cooling, and cell phones only need heat sinks? | There are games on mobile that seem to push phone limits hard. PC's do this, but have fan cooling or water cooling. How do cell phones play games like PUBG and Fortnite all the while just using heat sinks? | Technology | explainlikeimfive | {
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"text": [
"A cellphone running a game is running the game at settings that keep it within a certain thermal range, so you don't get a burnt hand, battery going pop, thermal shutdown etc & #x200B; It's quite possible to thrash a pc up to the point that it'll \"nope\" out on you due to thermals, but the amount of heat you can pour into the 'system' is far, far more due to airflow, massive heat sinks etc As a result, you can run the hardware harder and hotter e.g. tons of cores at almost 5GHz well over 60fps, 4k etc",
"Computer parts are way more powerful and power hungry than smartphones parts. & #x200B; A weaker, low end desktop processor, like Core i3 or Ryzen 3, produces a maximum of 65w of heat, while a High end Smartphone SoC, like the snapdragon 855, only 4.5w",
"A computer (or mobile phone) will turn almost all of the energy it draws from its power source into heat. In the process of turning the energy into heat, it also runs your game, but eventually most energy will result in heat. Your PC is plugged into the wall, where it can (and does) draw a lot of power. But more power means more heat, and more heat means more cooling or things start to melt. Your phone can only access its battery to run the game, which is a significantly weaker source of power. Hence it produces less heat and can get by with heat sinks."
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bo57vs | Holding Batteries | How come when I hold a AA battery and place a finger on either end I don't complete the circuit and get a zap? | Technology | explainlikeimfive | {
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"enc92dp"
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"text": [
"You do complete the circuit, and you do get a \"zap.\" It's just that the voltage is so low (1.5 volts) and your skin has high enough resistance that there is very little current, a zap too small to notice."
],
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10
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bodmrm | Why can a 20 minute video take 5 minutes to upload onto YouTube and then the same video, take 40 minutes uploading to Google Drive? | Technology | explainlikeimfive | {
"a_id": [
"enf50xn",
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"text": [
"This is a good question, considering Youtube is a subsidiary of Google and all. I can't believe it has anything to do with server speeds, Google probably has the fastest servers in the whole world. I don't upload to Youtube often, but I have noticed uploading to GDrive can take quite a while for larger files.",
"Probably because in general they don't need to provide infrastructure to speed up the process of uploading a spreadsheet at the same level they need for their users to speed up the process of uploading videos of a size rounding the Gigabytes. People mostly won't complain about upload speeds on gdrive because the common use is to upload and share ordinary files. If a file uploads in one or three seconds is not a too dramatic difference as to compare uploading a video for 15 or 45 minutes, even when in both cases the difference is 3 times."
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bohn24 | How do password managers know your password without actually knowing your password? | Technology | explainlikeimfive | {
"a_id": [
"engmtfq",
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"text": [
"Every single answer here is incorrect. They all explain how websites store passwords, not password managers. **PASSWORD MANAGERS DO NOT HASH PASSWORDS**. If they did, you will never be able to retrieve the passwords that you store in there. Instead, what they do is encrypt passwords to be stored with your master password (**simplification alert**: you actually encrypt it with a special decryption key which is related to your master password, but for simplicity's sake we'll assume passwords are encrypted/decrypted with your master password) Say you want to give something (your password) to someone for safekeeping (password manager) and you don't want them to see what you're storing. You put the data inside a strong box and lock it (encryption) and then hand it of to the person. So only you can open the box (decrypt the data) with the master key. When you want to retrieve a password from your password manager: Your password is first used as a verification to ensure that the server sends the encrypted data to the correct person (this part is like how regular websites use passwords to log you in with hashing and stuff). Then the encrypted data (box) is sent by the server which is then then decrypted (unlocked) with your password **on your device**. Remember, the client (software running on your phone/computer) will only send encrypted passwords to the password managers server. The server has no idea what it's receiving from your client. This is why it's important to choose password managers with open source clients which you can verify only sends encrypted data (Note this encryption is separate from the https encryption your browser/app does while communicating with the servers) Now that you retrieved your website password securely, it's just like entering it as if you remembered it. Here is where all the hashing mentioned in the other answer comes in So the master password serves 2 functions: authenticate you and allow you to decrypt the data. If you ever forgot your password, even if you managed you authenticate yourself to the service by contacting support, the best they can do is hand over a blob of useless encrypted data",
"You’re just missing a step. User creates account and enters a password. Password is irreversibly encrypted (hashed). Encrypted password is stored on server. When logging in, the password entered is also encrypted and compared to the stored encrypted password. So there’s only one way to get those to match, which is to hash a password identical to the one hashed and stored in the database."
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boht7i | What is a Processes Working Set? | Hello, working with Windows Powershell and i get with get-processes a WS value wich is the Working Set value. I have no clue what the value mean though... Can someone help me get that? thanks :) | Technology | explainlikeimfive | {
"a_id": [
"engglee"
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"text": [
"Think of it like $20 dollar bills in your pocket. Its a resource (pageable memory) that has been allocated and now quick and easy to use. If you run out, it’s gonna take some time/work to get it (hard page fault), kind of like doing another ATM transaction."
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bol96r | why does putting "www" before the address matter for some sites but not others? | Technology | explainlikeimfive | {
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"Originally, the world wide web was just a small part of the internet. The internet included the world wide web, but it also included FTP (file transfer protocol), e-mail (okay, we still have that), Usenet (bulletin boards), and more. So, if you buy a domain, say URL_4 , then you would put your webpage on URL_1 , and you would put your files on URL_2 , and your email address might be at mail. URL_4 . But as time progressed, the world wide web eclipsed much of those, so we figured it would be easier to type in URL_0 as opposed to www. URL_0 , and here we are!",
"That all depends on how the server and DNS record instructions are setup. You can tell a server hosting the website, my name is www. URL_0 , show this website. If you only tell the server, my name is URL_0 , the server has no idea what you are talking about. Same goes with websites where you enter www. URL_0 and you end up on URL_0 . That server automatically points you to the one without www. So if a website address is requiring you to put www in front of the address, the server and DNS instructions are not setup to serve the non-www domain ( URL_0 ) content. Being in the tech field, this makes me irritable when this happens. Simply because the right setup to allow a user to enter both a www and non-www address isn’t hard to do.",
"It just depends on how the servers are set up. Technically, [ URL_0 ](https:// URL_0 ) is the correct way. www refers to a specific host in the [ URL_5 ](https:// URL_5 ) domain. That's why there's things like [ URL_1 ](https:// URL_1 ) and [ URL_4 ]( URL_3 ) as well. Since everyone equates \"the internet\" with \"a website\", marketing folks have had their sysadmins tell their webservers to answer to [ URL_5 ](https:// URL_5 ) as well as URL_0 .",
"URL’s are read from right to left. When an address is something like URL_0 , first you access the “.com” server and look for “foo.” Then when you find out where that is, you go to “ URL_4 ” and look for the part that says “www.” So like, maps. URL_1 , images. URL_1 , those are all on “ URL_1 ” which is a part of the larger “.com” as a whole. www just means like “this part is the part where we keep the HTTP web pages and not the emails and telnet stuff and FTP and all the other stuff you can do with an internet domain.” It’s just like organizing your stuff into folders vs. leaving it all on the desktop or home screen; if they don’t want to set their domain up that way, they don’t have to.",
"The Internet works on IP addresses. The domain name system will translate a name people find easy to use (e.g. www. URL_0 ) into an IP address (e.g. 192.168.0.1). The owners of the domain can create as many names as they want (e.g. URL_0 , www. URL_0 , web. URL_0 , etc), point them all at the same address, and configure their web server to respond to any of those names."
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"google.com",
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[
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"mail.foo.com",
"https://www.foo.com",
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bomxhb | How are hard drives/sd cards/digital storage nearly doubling in storage capacity, while remaining roughly the same size, year over year? | Technology | explainlikeimfive | {
"a_id": [
"eni4tq5"
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"text": [
"Digital storage capacity has nearly everything to do with storage *density*, or the number of bits that can be stored per unit area. Imagine you have 100 light bulbs, and they can be switched on and off individually via a set of switches you have. Each bulb represents a bit of information (on/off). Say it takes up a square meter of space. You have 100 bits per m^2 in terms of storage density. Then, someone discovers that they can make the light bulbs a LOT smaller, half as small in fact, so instead of fitting 100 light bulbs per m^2, you can fit 400 light bulbs per m^2. Your storage density just went up four times! People keep finding new and novel ways to make the light bulb smaller, until eventually they can't figure out how to make them any smaller, so they try to find something new. Wow, LEDs are REALLY small, and they work kind of the same way as light bulbs. . . All of a sudden, you can fit 1,000,000 bits per m^2. This process of miniaturization is exactly what allows us to cram more bits into the same unit area. We use transistors that are incredibly tiny, on the order of 10nm, or ten *billionths* of a meter wide. If we can make that smaller, say 7nm, then we can cram more and more into the same area, increasing capacity without increasing the physical size of the object. Hard disks use magnetic fields, and as precision of the technology increases, the greater density we can achieve that way. If I can precisely measure a magnetic field that is say 2mm wide, and improve that to 1mm, I can store 4 times as many 1mm fields as 2mm fields. So as technology gets more and more precise, and tinier and tinier, we're able to store more and more information in the same area."
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bool78 | What are delegates and lambdas? | Technology | explainlikeimfive | {
"a_id": [
"enj2jau",
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"text": [
"I know this is ELI5 but I'm going to assume you have at least a tiny bit of programming knowledge. Literally day one stuff. A variable is a value with a name. For example: let MyVariable = 5 The name is `MyVariable` and the value is `5`. A function looks something like this: function MyFunction(a) { return a + 1 } The name of the function is `MyFunction`. Then there's another part of the function: `(a) { return a + 1 }`. You can kind of think of this as the \"value\" of the function. A lambda is simply a function value without a name. Just as you can think of the value `5` outside of the variable, you can think of the lambda `(a) = > a + 1` outside of the function (I switched up the syntax a little to match how lambdas usually look but it means exactly the same thing as the function code above). A delegate is a variable whose value is a lambda. So you could do something like this: let MyDelegate = (a) = > a + 1 let MyNewVariable = MyDelegate(5) // this will store a 6 in MyNewVariable Then you've got a nice handle for your lambda. You'll notice this is a lot like a function, since it's got a name. However, delegates are a little more flexible since you can set them based on other variables, change them, pass them as parameters, and all the other things you can do with variables. You can even pass them to other delegates! let MyNewDelegate = (a,b) = > a(a(b)) let YetAnotherVariable = MyNewDelegate(MyDelegate, 5) // this will set YetAnotherVariable to 7",
"I assume this is the case but you mean in programming, correct?"
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boouix | How does captcha work exactly and what is it supposed to accomplish? | Technology | explainlikeimfive | {
"a_id": [
"eniuam0",
"eniy8gg"
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"text": [
"Websites use captcha schemes to separate human users from simple computing users. Because humans can do some things easily while same task is harder on computer. At same time, new AI algorithms are solving what we're previously hard computing problems. As AIs grows in capability, captcha teams have to find new problems that are easy on humans but still hard on AI. Additionally REcaptcha is used to improve Optical Character Recognition algorithms so that printed books can be digitized easier. It's also used to gather datasets to train AI REcaptcha is funded by Google.",
"I read recently that bots are getting so good at captchas that they are designing them now for the human to fail but bots will get it right. URL_0"
],
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"text_urls": [
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"https://qz.com/1047988/amazon-amzn-has-a-new-captcha-that-youre-designed-to-fail/"
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|
boqfuq | Why does 24 FPS look fine for films and television, but looks terrible for video games? | Technology | explainlikeimfive | {
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"text": [
"Movie frames are formed by a camera with an aperture being open for a period of time. This means there is “motion blur” as things move across the frame while the shutter is open. In contrast the computer is calculating a single instant in time. There is no movement so everything is crisp and clear, but on the other hand changes between each frame are somewhat more abrupt than merging the ends of a blurred object’s path. So the lower frame rate actually has frames with more information in them as they capture a period of time, albeit blurred, while the computer’s frames are crisp snapshots without any movement information.",
"In addition to the other answers. In a game you're controlling the camera. So noticing the lower framerate is often noticing the delay between your hand moving the mouse and the camera angle changing. Which you might not have spotted if you were watching someone else play the game.",
"24fps isn't fine for anything. I hate seeing individual frames. I wish the various industries would go to 30fps minimum.",
"It's worth mentioning that movie theater projectors display at 72 Hz. This means each frame of the film is displayed 3 times before moving on to the next one. So when you go watch a movie at the theater you are seeing the film in 24 frames per second. TV sets, on the other hand, often display at 60 Hz. So when you watch a 24 fps film on TV you do get issues. This is why motion on TV can seem somewhat jerky compared to watching a film in a theater with a projector. More info on this can be found here: URL_0 EDIT: I should also add that some TV manufacturers have tried to deal with this with special settings. Some TVs has a 24 frames per second mode where the display shifts to refreshing in some interval of 24. This way you can have more fluid motion as the film will be in true 24 frames per second on the TV. There is also a completely unrelated technology called motion interpolation which artificially inserts frames into a film using an algorithm to bump up the 24fps film into 60 fps. This technology is very controversial because many films look unnatural and have sort of a \"soap opera\" effect when the motion interpolation does this artificial frame rate increase. Many directors and filmmakers have spoken out about how much they hate motion interpolation.",
"If you see a 24fps film panning across a scene, you notice the choppiness. That's why you don't see much panning from side to side in movies. Video games do have a lot of panning, whether it's 2d scrolling or strafing from side to side in first person view. You don't notice it *as much* if it's a fast action scene because the moving bits are different from frame to frame, and because the frames blur as the camera is capturing it. You don't get the blurring with video games since they're rendered instead of captured by a camera. Unless it's added by the developer, and the attempts I've seen have been pretty bad. Static talky bits are okay because it's basically a still image, and the frame rate doesn't make much difference."
],
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borni0 | How does somebody take a video first person view, but when they look in a mirror, they don’t see the camera? | Technology | explainlikeimfive | {
"a_id": [
"enjtvre",
"enju5b6"
],
"text": [
"Can you explain what you mean or provide an example? Mirror shots are usually filmed at specific angles to hide the camera, use sets with duplicate rooms on either side of a false mirror, or digitally erase the mirror in post.",
"I might not be the best person to answer this, but as no one else has & I used to make movies as a kid I might as well. There are a few techniques that I know of, a lot of people will use strategic angling to produce the effect. The other is to take 2 separate videos (one of the persons “reflection” and another of the original scene) and splice the two pieces of footage together. Or, a combination of both of those techniques."
],
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bory6j | How come you can power a radio exclusively via radio waves and we still have to charge our cell phones? | When I was a boy I built a crystal radio that fit into a tic tac box. This thing had no battery and ran a tiny little earpiece. Plans for these are available all over the net, I genuinely want to know why we aren’t using cell phone antennas to passively harness RF and rectify and recycle. If it’s possible to listen to broadcast radio without batteries why can’t that (even if it’s microvolts) be harnessed? How does the front end of the cell receiver circuit dissipate the unwanted frequencies? ELI5 reddit, and thanks! | Technology | explainlikeimfive | {
"a_id": [
"enjux98",
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"text": [
"Its a matter of scale. Your radio was able to function on just milliwatts of power, your phone has an ~11 Watt hour battery pack so if it lasts just 11 hours that means you're using about a watt of constant power. There just isn't enough random radio waves bouncing around to absorb to turn into a watt of power. You'd need to capture 100-1000x as much power as your little radio was catching and that power just isn't available out there.",
"A crystal radio only take fractions of a Watt (measured in the thousandths) to move a *very tiny* speaker. A cell phone can easily draw 5-10W when you're using it. We're talking about a ten thousandfold difference in the amount of power we need."
],
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bosr09 | Why can’t we text using bold, italics, or underlines? | Technology | explainlikeimfive | {
"a_id": [
"enk7jbi"
],
"text": [
"The SMS service standard simply doesn’t allow for “markup” as, for example, HTML does for the web. It was invented at a time when phones only had numeric buttons. You could just start using a markup standard but it would be confusing for the many older phones that didn’t understand and presented things like < b > to their users. The mobile networks could try to remove markup for old handsets but it would be problematic. Also, markup would be abused by spammers sending you huge, bold, red, flashing messages. Fonts with coloured characters, i.e., emoji, are already bad enough."
],
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6
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boywfi | How do people uncover vulnerable mistakes in chips or software? | Hi, you often read about how cyber/computer security experts uncovered a new vulnerability in chips or computer software. I theory, I often understand how they work, but they seem so specific that I cant imagine how people identify them and learn about them. E.g the famous Spectre or Meltdown. How does the process of identifying these vulnerabilities look like? Is it deliberate, or do people working on similar topics just discover a "weird" behaviour they decide to explore more? Thanks | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"There isn’t a set method to uncover vulnerabilities, people typically start with how they think something works. The guess could be right, or it could be wrong. Sometimes these implementations have side effects that either went unnoticed, or was decided to be rare enough to not bother fixing it. These side effects are considered vulnerabilities, but not all of them are the major “ground breaking” ones. But regardless, both types are found the same way, it just depends on what side effect you found.",
"Depends on exactly what they are breaking and what they want to do. But typically it's a mix of things. Most vulnerabilities are found by users who encounter problems (the program crashes for example), they report it (or the user is the developer themselves doing testing, so they report to themselves). The developers work on fixing the problem and then find that it crashes when you do this, but if you did X it would actually allow you to take control of the computer. That's a vulnerability. So they fix it and announce the vulnerability. Other cases you have people who want to activity break things and find vulnerabilities, they'll do this a few ways. They'll look for known problems, maybe the developers didn't think about it enough and it's actually a vulnerability. Another common method is just think about common problems and try to attack those problems, for example user input sanitizing is a big attack vector, they'll check all the inputs. To help with this sometimes they'll use attacks like fuzzing, which is where you write a program to use the application the right way, but then just randomly make errors in how you use it, ordinarily random errors should be returned with an error of some sort, but sometimes they find that there is a bus and it actually crashes, that can then be checked to see if it's a potential vulnerability. Stuff like Spectre and Meltdown were found by research groups, basically they are security researchers, they think of ways to make vulnerabilities, so other people understand the risk and can design their systems to avoid it. Seeing across a CPU to other processes via a timing attack has been known for a while as a way to attack systems, but nobody knew a way to actually implement it and it was kind of forgotten. The researchers brought up the old idea and rethought attacking it, and developed a method that actually works."
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bozf6c | How Does Google Pixel's Image Processing Software Work? | I got a Google Pixel 3a last night and am blown away by the camera's processing capabilities, especially with the Night Sight mode. I took a picture of the city from my balcony and it was unreal watching the software do its thing and sharpen the image, bring out the colors, etc. It looks almost as good as a picture I took on my DSLR. I get that there's some AI that intrinsically understands what it's looking at and how to optimize it, but how does this actually work? How does the software understand that it's looking at a view of a city and not of a person? | Technology | explainlikeimfive | {
"a_id": [
"ennvq2g"
],
"text": [
"Here's a [blog by Google]( URL_1 ) that explains how Night Sight works specifically. And here's [a more in-depth article]( URL_0 ) that is less ELI5. In summary: If the phone is still, and the subject isn't moving, the camera just has a longer exposure. If the phone is shaking or there is movement in the shot, the camera takes many short exposure photos and merges them together to create a brighter, better lit picture. AI can help with this process and general image processing. The idea is to take a bunch of pictures. Have a human correct the color manually. Then feed the unaltered photo into the AI and make it learn by using the corrected photos as comparison."
],
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"https://ai.googleblog.com/2018/11/night-sight-seeing-in-dark-on-pixel.html",
"https://www.blog.google/products/pixel/see-light-night-sight/"
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bozv3j | why is WPS insecure? | Apparently, Wi-Fi Protected Setup is so insecure that Android removed support in Android P, the reasoning being that a PIN is easily brute-forced. But in my understanding WPS is normally disabled, until you press the button on the router which gives you a window of a couple of minutes to pair your device. Unless you have someone in wifi range constantly monitoring your network and taking advantage of that window, it shouldn't add any attack surface. Am I missing something? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"the button doesn't turn WPS on, it turns on the broadcasting of the pin. you can brute force the pin whenever you want as long as WPS is enabled."
],
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5
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bp3bcf | How does voice recognition technology work? What do our phones, cars, Alexas, etc. do to allow them to hear and interpret what we say? | Technology | explainlikeimfive | {
"a_id": [
"enoivsy"
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"text": [
"What we perceive as \"sound\" is actually changes in air pressure. When something makes a sound, it causes vibrations in the air. These \"vibrations\" are made up of peaks (positive pressure) and troughs (negative pressure). Once the vibrations reach our ears, our ear drums push and pull in response to these peaks and troughs, and our brain interprets this as \"sound\". Microphones work in a similar fashion - they have an element inside them (it's different depending on the type of microphone) that responds to sound vibrations and converts them into electrical current. This current will travel through the cable the microphone it's connected to. The other end of the cable can be connected to an \"AD converter\" (analog-to-digital converter). The AD converter takes the electrical (i.e. analog) signal and converts it into digital format (1s and 0s) that computers can understand. Any electronic device that has voice recognition technology has a microphone and an AD converter in it, which allows the device to pick up what we're saying and convert it into digital format. You can teach software to look for patterns in the digital format and, once recognised, perform a certain action. The problem is that two voice commands will ever be identical. Everyone has different vocal cords and pronounces things differently, and the room/environment you're in will make everything sound different, even if just by a tiny bit. Even the same person will never be able to reproduce a 100% identical voice recording of something they've already done. It's impossible, there will always be variation. So, they get a lot of examples, to try and cover as many people as possible. Once you have thousands and thousands of samples of someone saying \"Hey Siri\", they can look for general patterns that are present in all of the different examples and teach the software to look out for that. Once the pattern is recognised it's quite simple - just program it to do X when the person says X, and Y when they say Y."
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bp5d5x | How does a digital thermometer measure the temperature? | Technology | explainlikeimfive | {
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"text": [
"There are a number of different types of electrical temperature sensor. One of the most common, robust and cheap is the thermistor which changes electrical resistance with temperature. That is used in a circuit which gives an output to drive the display depending on that resistance. Other types, more used in scientific rather than domestic equipment, include thermocouples which generate a voltage depending on their temperature and platinum filaments which again change resistance.",
"It uses something called a thermocouple. It’s basically two different metal wires joined together. The temperature causes small signals of electricity that is measured by a volt meter or the digital thermometer."
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bp5w8r | Why isn’t possible for all cars to move in unison when a red light turns green instead of seeing a green light and having to wait a few seconds before you can move? | Technology | explainlikeimfive | {
"a_id": [
"enoyno1"
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"text": [
"It's to do with the spaces between the cars. At the lights there's only a small gap, and if all the cars started together then the gap wouldn't grow and if someone hits the breaks there would be an accident. By waiting a second for the car in front to move, you create a safe gap between your car and the car in front."
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3
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bp6jf5 | How are computer parts manufactured to be so small? | This has genuinely confused me. How would you be able to manufacture something that is so small yet looks like it's so powerful? | Technology | explainlikeimfive | {
"a_id": [
"enpar0p"
],
"text": [
"Very very carefully! To be more serious, the smallest things that are manufactured in volume are \"Integrated Circuits\" (ICs). For example, microprocessors or Graphics Processing Units (GPUs) can contain billions of tiny transistors on a piece of silicon the size of your thumbnail. Each transistor is many many times smaller than the diameter of a human hair. There are a few key components of making something this small. One is \"photolithography\". The pattern you are trying to make on the silicon wafer (or a layer of something deposited on the silicon) is defined by shining light through a \"mask\". This mask has clear areas, and opaque areas. The light hits (or doesn't hit) the photoresist, a light sensitive layer deposited on top of the Si wafer. This changes its chemical properties, making it easier/harder to etch away (depending on the type of photoresist). This essentially allows one to re-create the mask's pattern or its negative in the photoresist, and thus on the materials on the wafer. To make really small things this way, you need to either have a very small mask to start with, you need to reduce the image down using lenses, or both. Modern IC manufacturing does both. The mask is made in a process similar to what I described, but of course there is no mask. There is a very transparent quartz glass coated with a metal like chrome, and that's coated with a photoresist. Instead of using a mask to expose the photoresist (or not), the image is written directly on the photoresist with an electron beam. This is a slow process, but once you are done you have a very valuable mask with tiny features. And to make those features even smaller when doing the photolithography process on the Si wafer, a very very good set of lenses is used to reduce the size of the mask image."
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10
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bp8dy8 | How do websites know to go to the mobile version on your phone even when you click a desktop link but don't know how to go to the desktop version on your desktop if you click a mobile link? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"When you send a request for a website, you send information about your device and what exactly you are after in the headers of a request. There is a header called \"user-agent\" this basically defines what device you are on. Mine for example says \"Mozilla/5.0 (Linux; Android 8.1.0; SM-T580) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.157 Safari/537.36\". Therefore websites know that my device is an android device, so they know to deliver the mobile version to my device.",
"There was a time where smartphones became suddenly big, but most big sites didn’t have a mobile version. The first iPhone was shown browsing the New York Times webpage by Steve Jobs which was not optimized for mobiles at all. Companies paid a lot of money to get mobile versions out which coexisted with the default desktop version. These versions usually have a different source code and a different feature set, which to this day frustrates users, who can’t find important stuff because the mobile site doesn’t support or show it properly. If you visit the domain URL_1 you are redirected to URL_0 if browser shows a certain device identifier (for mobile devices). Sometimes they just check for the viewport width and height (e.g load the mobile size if the width is < 768px). Nowadays such an approach is heavily discouraged. You usually develop mobile first and the design is responsive so that it automatically expands to bigger viewports. The main advantage is that you have only one code for all devices and don’t need to do twice the work in case of updates. Because > 50% of site traffic comes from mobile devices nowadays, google expect websites to be mobile first and punishes sites in the page ranking who are not mobile friendly.",
"First of all, it's not a matter of knowledge - your device tells the website whether it's a desktop or a phone (unless you specifically configured it to say otherwise). It's a design choice by whoever made the website. Often it's because the desktop site came first and is considered the \"default\", while the mobile site was added later. So the site assumes that if you clicked a link to the mobile site, that's the site you meant to enter, whether you are actually on a mobile device or not.",
"Basically html and JavaScript code that checks the resolution of your screen and other browser information to determine what device you are on. But on desktops they can emulate the mobile eviorment given the mobile link and you can also view the desktop version on a mobile if you say so on browser settings on some websites.",
"There are 2 methods for making a website work across different devices. The first involves the device (phone or desktop) telling the website what kind of device it is, and the website giving the user the specific version of the site that suits their device. The desktop and mobile versions are generally completely seperate codebases. This method was common when smartphones first became popular as it was a way for companies to give a mobile experience without having to redo their existing desktop website. These mobile sites often had domains like URL_0 The second method is called responsive design, and is overwhelmingly the standard approach today. It involves giving the same website to both phones and desktops, and letting the device decide on which styles to use based on a few factors but mostly screen size. To answer your question, I mentioned that in the first method the website decides which version to give to the user based on what device it is. People (developers) tend to expect users to enter the site from the desktop URL ( URL_1 or www. URL_1 ) so do this check when the user hits this URL and redirect the phone traffic as necessary. Unfortunately the developers may not anticipate desktop users to land on the URL_0 version so don’t bother adding the ‘check’ to this version. It really comes down to sloppy web development, but due to responsive design it’s becoming less of a problem."
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bp8m0j | . Is it possible to hack into a self driving car and change its destination or even reck it ? | Technology | explainlikeimfive | {
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"enq5mur",
"enpxt6b"
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"text": [
"This is the very thing that some cybersecurity researchers at Georgia Tech are investigating and the answer appears to be \"Yes\". Although there haven't been any large scale attacks on them and self-driving cars themselves have not been deployed on any mass scale researchers are finding plenty of problems with GPS spoofing and Collision Avoidance Systems that can be exploited.",
"Possibly. All self driving cars currently are experimental, so we don't know yet how easy it would be to spoof GPs signals to them."
],
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bp9arp | why does wikipedia need millions of dollars each year? Isn't it just a couple of servers running an open source script? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"First off the foundation receiving your donation is not Wikipedia, its Wikimedia, a larger parent organisation that operates a multitude of projects. The servers which run a site the size of Wikipedia are not the same as the server running your personal website, there will likely be a main server, with the size of it probably a physical tin, and backup failsafe, if not multiples of each. Next you have staffing costs, Wikimedia is the output of more than one person, constantly running script upgrades and the likes. So you have a tech team diligently keeping servers running, updating code to make sure it still looks nice and no one has accidentally cocked something up. Now you need HR, because you start employing people, theres legal issues so you start to need a legal team. Now you're paying lots of people, you need office space and equipment, so theres rent, and a facilities manager. All of a sudden your finances are getting complex so you hire an accountant. Now you raise funding, Wikipedia's direct running costs (staff, techs, space) was around $30m (2012 - figures). They consistently raise more than this and are sat on a nice comfy cash cushion. Wikipedia's last entry in 2012 stated net financial assets as $35m, and have since started using some of their surplus cash to invest in lobbying.",
"It's probably several hundred to a few thousand servers and several GBps of bandwidth we're talking about. They probably put up billions of pages a month. Storage for the databases, probably on the order of petabytes of data.... Not cheap. At all.",
"On the internet, data usage is a cost. You pay for flatrate availability of internet data to your home. But the service provider buys it for a fee that is related to how much data is actually sent in and out. Which means that the hoster of the Wikipedia servers, THEY get to pay some for every piece of data that leaves or goes into the servers. And...while you could be willing to do a lot of things for the common good and all that, the hosting provider may be willing to *not get a profit* from the site, but they are sure as hell not willing to host Wikipedia without making money and then *pay someone else to be allowed to send out the data*... In other words, there got to be some money involved. Some chains along the way are NOT willing to do this for free.",
"It's not just \"a couple of servers\". There are likely several tiers of servers acting as caches and redundancy. The speed of light is finite, and the speed of accessing data (from any tier of memory) is slow. By caching recently and frequently used data on servers near the users, the result is the experience you are used to: a quick service where you don't notice the other millions of users using the service at the same time. If you want to know exactly how slow the speed of light is, all you have to do is to find a server in Australia (assuming you're in say US or Europe for instance) which hasn't been accessed from outside Australia in a while. The server itself may be top notch, but accessing the content, will be sloooow. Now, the hardware is one thing, it's expensive, but relatively it's not the big cost. Having the hardware running requires electricity, and the electric companies (no matter how much they use wikipedia) won't keep Wikimedia's hardware running for free, because it's quite a lot of power and subsequently a lot of power sold. So, someone has to pay those bills - that someone wants his or her salary as well. Same for connecting all those servers to the internet. And then there are the developers getting rid of all bugs than come up along the way, and those developers who are currently working on the upcoming upgrades of the software. Then there is that hardware again, it doesn't keep itself running 24/7/365, even though the service is there 24/7/365. The systems need security patches, hardware break, the software it's running might stop responding as intended ... enter the sysadmins, and we have a bills to pay as well. And that's more or less before all other company administration (legal, HR, and what not). They need their workspace and have bills to pay as well. It takes resources to keep a global service running, no matter how \"simple\" the service might seem. A lot of resources ... and none of it is free.",
"The actual running costs are relatively tiny compared to their income. They employ quite a few expensive software developers building mostly-unrelated stuff; most of the money goes to wikimedia foundation projects which aren’t the main site."
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bp9as6 | Why do video streaming websites like YouTube choose to support 60 FPS only for 720p and above? | Technology | explainlikeimfive | {
"a_id": [
"enqa6nx"
],
"text": [
"The lower quality tiers are usually for people who have slow internet connection. 60fps would however need more data to be transferred so it'd be counter-intuitive to make the 480p and lower available with 60fps."
],
"score": [
4
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bpa7jx | how does the WhatsApp exploit bypass the sandbox restrictions by the OS | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"\"A buffer overflow occurs when a programming error allows more data to be written to a given area of memory than can actually be stored there,\" Rik Ferguson, the vice president of security research at the security-software firm Trend Micro, told Business Insider in an email. \"The extra data flows into adjacent storage, corrupting or overwriting the data previously held there, and can cause crashes, corruptions, or serve as an entry point for further intrusions.\" In the case of the WhatsApp attack, intruders exploited the buffer-overflow bug through the app's phone-call function to install spyware on smartphones without the phones' owners knowing, the Financial Times reported. The exploit would work even if the victim did not answer the call, the report said. From URL_0",
"There's two parts to this answer. First is, the WhatsApp exploit itself is just an exploit that abuses bugs in WhatsApp to allow the attacker to run whatever code they want with the same level of access as the WhatsApp itself (\"arbitrary code execution\" in the lingo). So, now that you found a way to run arbitrary code on your victim's phone, what do you do with that? The second step is that you find a vulnerability in how the sandbox itself is implemented , and exploit that vulnerability as a way to gain broader access to the phone. This is where Pegasus presumably comes into the equation. I can't find anything conclusive either, but it does seem that this would only affect older versions of iOS, yes. Android, or other versions of iOS, would presumably require a different exploit for this part."
],
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"http://www.businessinsider.com/whatsapp-spyware-hack-attack-vulnerability-explained-2019-5"
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|
bpew27 | Why did the look of movies get "clearer" in the 1990s? | Technology | explainlikeimfive | {
"a_id": [
"ensgfcm",
"enshuc5"
],
"text": [
"The quality of film has evolved over time. We've learned to make film that doesn't crush black as much. Early black and white movies don't look nearly as good as later black and white movies. The color process has evolved too, allowing far more nuanced shades of colors. But we've also learned how to make film with finer crystals, which makes for a smoother look and more detail even on the same size of film. I don't think the difference you're seeing between movies this relatively recent and this relatively close together has much to do with a noticeable advancement of technology, however. There are many many different types of film to film on. Even film by the same company can vary quite wildly in terms of color, contrast and grain. Choosing the right film for a project is an artistic decision. License to Kill is a movie where Timothy Dalton wanted to return the character of James Bond to be more grounded, believable, and ruthless. Closer to how he felt the character was developed in the books. For a Bond movie, it's extremely serious. It would make sense to pick a grainier type of film for a grittier movie. The World is Not Enough is a very campy movie that it doesn't take itself seriously. It wouldn't benefit from a gritty filming style.",
"I think you're just comparing different grade of filmstock. Look at 2001 for example, it came out in 1968 and it looks fantastic."
],
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bpj1st | How do printers work so accurately and fast? | Technology | explainlikeimfive | {
"a_id": [
"entxog0"
],
"text": [
"I don’t know what exactly you are looking for as an answer... They work accurately because the motor that controls the printing head works in very small increments (typically 96 positions per inch) and the ink injectors can inject extremely small quantities of ink. They work fast because the motor is fast."
],
"score": [
5
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bpkslw | How did humans all over come to know what parts of a plant are edible, toxic, and which ones serve as remedies for illnesses ? | Technology | explainlikeimfive | {
"a_id": [
"enudfmb",
"enus00k",
"envbcgs"
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"text": [
"Trial and error, and they were often wrong. Many traditional plant remedies are total nonsense, or even actively harmful, and tomatoes were widely thought to be poison by most of Europe for hundreds of years.",
"Humans didn’t just appear one day and have to learn these things. One day an animal was born that we class as a modern human but it’s mother wasn’t quite. My point is that that baby was taught just like we are and so were it’s ancestors going way way back, even before language. They all grew up knowing not to eat the mushrooms in that valley or the clams in spring because the knowledge was passed down from generation to generation. That and innate knowledge that eating foul-smelling or blue/oddly coloured food was bad.",
"Painful trial and error. If you are facing starvation, you will try to eat anything. Eventually, we figured out what works. Also, nature gives a lot of good hints. Part of the reason we have taste buds for bitter is many poisonous things in nature are bitter."
],
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bpmcx1 | Why do TV remote batteries last a lot longer than wireless video game controller batteries? | Even when the controller sits idle while I watch Netflix, the battery life is substantially less than a TV remote. | Technology | explainlikeimfive | {
"a_id": [
"enuy9pz",
"enx8zcx",
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],
"text": [
"You’re not constantly pushing all of the buttons on a tv remote for hours on end. Simply moving left on a joystick would constitute as always sending a signal. ...and that’s not even getting into controllers that vibrate.",
"TV remotes are passive, they only do something when you press a button. They also use infrared light signals, which are very power efficient. A normal TV remote is almost just like a toy with a bunch of lights. You press a button and a light flashes in a certain pattern. Video game console controllers are active and use less power efficient RF signals (Usually Bluetooth). They're constantly communicating with the console, even when you're not pressing any buttons. Basically, they send several 'Are you still there?' messages a second.",
"A TV remote sends a very low power, low-speed signal at most a few times an hour. A wireless controller has to stay in constant communication when in use, and because it is sending more data, it has to use more power."
],
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bppjlx | how can lightbulbs change color? | Technology | explainlikeimfive | {
"a_id": [
"enw3a0a"
],
"text": [
"The light source consists different color \"channels\". A controller can make combinations of these channels, leading to different colors. Similar to mixing paint to create more colors!"
],
"score": [
5
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|
bpqu7x | How do cameras at golfing events keep track of a golf ball after it's been hit when its moving so fast and so small? | Technology | explainlikeimfive | {
"a_id": [
"enwitok",
"enwtmyo",
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"text": [
"Typically they change the contrast in their viewfinder so the sky is white and the ball is black. That, and years of practice.",
"Now imagine doing it with cameras that used tubes to capture in SD resolution. Props to the cameramen of the 70’s and 80’s.",
"I heard a funny story(probably not true) that the military asked the PGA for the software they used to track golf balls so they could use it in their planes to track missiles and when the PGA said the cameramen did it by hand the military was baffled as to how they were so good.",
"Mostly practice, I used to film football games and had to keep track of the ball. But golf would require a lot more effort."
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bptgki | How was ice produced in the days before freezers in warmer climates? Was there any way to conserve foods/meats? | Technology | explainlikeimfive | {
"a_id": [
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"Ice was \"harvested\" from cold lakes, wrapped in insulated crates, and shipped to distant locations to keep food fresh in an \"icebox\".",
"salt was the main way meat would be stored so like salted pork. dehydration like jerky. pickling food like cabbage cucumbers and many more. and then we also grew and ate a lot more fall winter food that would keep longer like potatoes pumpkin squash can be kept for months in places like a cellar.",
"Before electricity, ice was farmed on lakes in the winter. Ice would be stored in building, covered with saw dust. The delivery wagons would haul the ice to homes, where it was put in ice boxes, which acted like a refrigerator. One statistic that will surprise you, before ww1, the annual ice harvest was more tonnage than rocks in the 3 great pyramids combined. Even in the early 50's, my mom and dad still had an ice box. The kept it on the back porch and drilled a hole in the side and let the water drain to the ground. Watch the old honeymooners tv show and they have [an icebox]( URL_0 ).",
"Did you mean \"preserve?\" & #x200B; Canning and salting were commonly used. Corned beef is a common modern-day version of salt-cured beef.",
"They sawed it out of the ice in the winter and put it in a shed. Huge blocks of this shit. They also buried food underground"
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bpw2m7 | why does the airport security make us take our electronic devices out of our bag during security scan? | Technology | explainlikeimfive | {
"a_id": [
"eny3cez"
],
"text": [
"Large screen devices like laptops or tablets will just look like blank squares on the x-ray scanner. So they won't be able to see if you're hiding something underneath it or not in your bag. Same reason why they make you take out *everything* from your pockets, even cigarette packs, when you do the Back Scatter machine."
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bpzlwt | Why does NASA have to wait until 2024 to land on the moon? | Why can’t we start that mission today? Don’t we have the knowledge from the Apollo missions to get us there? | Technology | explainlikeimfive | {
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"text": [
"We don't have any sort of rocket that can travel to the moon and back. We don't have a vehicle that can detach from that rocket and land on the moon. Takes a LOT of time and money to design and build those. Even 2024 seems way too soon. That's only five years. Plus, all the guys who worked on the Moon missions are long since retired or dead. We need to train all the current guys so they don't screw this up and get someone killed. The technology we used to go to the moon and back in the 1960's is all completely outdated and would be of no use. It's like someone saying they want to build a modern racecar by studying a Model T. Plus we have no astronauts who have trained for anything like that. It's not something you can learn as you go. Takes years of training because if something goes wrong, you don't have anyone but yourself to fix it. Plus even a delay of a few seconds in failing to react could spell your doom. Space is very unforgiving.",
"Knowing how to doesn't mean you have the machines to do so. Would you trust your life to a 50 year old space module? No...you'd build a new one. Want to find a factory to build one? Guess what....nobody is making them. So you gotta find engineers and machinists and software programmers and make sure certify it safe and to spec? Every single component like your life depended on it.",
"Knowledge, yes. Technologies and methods have potentially changed, though. They will also want to put together studies to be conducted to make it worthwhile to return, and they will want to test systems to make sure they are capable of fulfilling each leg of the journey prior to any launch. In this case, it *is* rocket science :\\",
"We have the knowledge and the design drawing for stuff that was used in the Apollo missions. What we do not have is the same manufacturing line and manufacturing teknologis that we had back in the 1960s. The development took years and part of that is to set up the production facilities. The way that we build stuff today is not the same as we did back the so some manufacturing metods that was used on Apollo is not used today. The documentation for exactly how things was manufactured is not that good and specific of how it was done it not that well documented. The plans and how to make it is not the same. You could likely recreate the Apollo program today in a few years if you got the money. The program costed adjusted for inflation in 2008 $163 billion and it would be even more today. The program today have a budget of $21 billion so the project is to do it fore less money and create a more advanced and capable lander but at a slower rate. It would cost billion so create the Apollo rockets and it is not cost efficient. A more recent example of restart a manufacturing line is for the F-22 here production was ended in 2011. The estimation is 2016 to restart the production os over $10 billion in 2018 [according to this]( URL_0 ). For that is a lot of manufacturing tool in storage but they do not exist for the Apollo program-"
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bpznw0 | Why do some devices and programs need to be rebooted/restarted when a new setting or update is applied to them? | Technology | explainlikeimfive | {
"a_id": [
"enzcdjs"
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"text": [
"If your operating system is like a running car, it would be dangerous to replace parts while the car is running. So you shut the car off. Replace the parts, then start it up again. Basically when your computer starts, it has a chance to replace files and do other things before anything else is started and needs those parts in the system."
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bq2hp1 | How did old hand-drawn animation achieve such consistent color? | Mainly wondering how they avoided discoloration or the presence of brushstrokes. Thanks! | Technology | explainlikeimfive | {
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"Speed and skill. Each pencil drawing by an animator was traced in ink on to a transparent sheet. Once the ink dried it was sent to painting where the paint was applied to the BACK of the transparent film. Each section of color had to be completed quickly while the paint was still very wet so it would show no brushstrokes or the cel was ruined, but going outside the lines would also ruin a cel, as even though it would not obscure the line, it would still show the color in the next section over. In the golden age of Disney the ink and paint department was a fleet women who's only job was to trace or paint. The inking girls were considered to be a higher caliber than the painting girls, as their work required a more steady hand, but the painting girls were amazing in their own right. One of the greatest accomplishments of that department was maintaining consistency in color and positioning on Snow White's blushed cheeks, which were done with *actual blush.* The effect was so time consuming it was never used again. They stuck to solid colors from then on out. Edit: I have been corrected below. The use of actual blush is an urban legend. The effect was achieved no less amazingly with a dye applied to each cel by a very talented woman from inking named Helen Ogger. See the post correcting me below for more detail.",
"Finally something I can answer! I have studied under a traditional animation cel-painter that worked on Disney and Bluth films, I can give some background. When studios wanted to get colors to always match up, there were whole groups of people that spend all day being color scientists. They do lots of research and science to make sure that the paint and colors are always the same by mixing chemicals and making sure to keep the recipe exact every time. When you are painting an animation cel, the technique is to let the blobs of wet paint skim across the plastic. Technically, the brush should never sweep across the surface of the cel to make a brushstroke, the brush is there mainly to push the blobs paint around. Think of it like you are pushing a drop of water softly across a tabletop, you run your brush against the surface of the drop to spread it gently until you finish filling the section you need. I'm not sure how to explain it more, it's a lot easier to do a demo but hopefully that helps!",
"There were whole departments dedicated to mixing the paints, doing nothing but ensuring every batch of colour matched every other. Cosgrove Hall had a pot of paint simply called \"DM's Nose\", used also for Duckula's tongue.",
"My godfather actually worked as a color specialist in a small animation studio in Lithuania during 80s. He told me the stories how he spent countless days mixing paint so it would be consistent. Writing down the exact numbers of how much of every color he used to create one or another shade of required color. Also he did mess up couple of times, just by adding couple drops more than needed. He said that in hand drawn animation it's VERY easy to notice even the slightest change in the shade of the colour when watching the final result",
"If I'm not mistaken, Adam Savage (Mythbusters, [ URL_1 ]( URL_0 ), former ILM) has discussed this before and recalled the days where he would have to paint the different layers on the cell and work out what colour it would be based on where it is on the stack. The further down, the more the colour changed, so they'd need to know how many layers the image was and then adjust each layer to colour correct for it.",
"The paint is paint- as long as you have it thick enough to be opaque, it looks the same if you apply extra anywhere. This was also necessary because it was layered over a background. Anything not opaque would be partially transparent when laid over the background. So it had to be opaque Keeping the paint look *identical* was a big thing. The backgrounds were often watercolor. It was not possible to anything other than scroll it around, it must be static. Because you can't repaint animation cells in watercolor with any consistency. Thus the Scooby Doo \"secret door\" or \"something hiding behind a bush\" being so obvious. If it opened or the bush shakes, that's animation so it has to be painted cells laid on a static watercolor background.",
"Unrelated to actual painting per se, but not every color on the cel was redrawn. They'd use layers much like Photoshop and sometimes just change the head that moved slightly while using the rest of the drawing/painting from the previous cel. It's also why lots of cartoon characters wore ties.",
"Excellent question, OP. Anecdotally, years ago (I'm in my 50's), I took a basic animation class taught by a guy who worked on Sleeping Beauty. He was the biggest ass I've ever met, and I don't think he actually did anything but tell (with obvious nostalgia) stories of the male Disney animators getting into friendly fistfights after work, playing pranks on each other, or making fun of any woman dumb enough to want to do what they did. In hindsight, I'm betting he had a very minor role and never got to see the inside of the studio again, which would explain why he never actually taught us anything.",
"I can’t speak for the golden age of hand drawn animation, but by the time I arrived in Los Angeles there was a shop called ‘Cartoon Color’ that sold animation supplies, including a spectrum of premixed colors that were renowned for their consistency. I believe the store—now closed—was in Culver City. There appears to be a moribund website associated with them as well.",
"RE the presence of brush strokes, they use a specific kind of acrylic paint that goes on very consistently. When I was really getting into sculpting I read about Cel-Vinyl paints that Kat Sapene (amazing sculpture painter) uses. Here's what she has to say about it: \"KS: I like to use animation cel-vinyl to paint my projects. It’s very similar to acrylic paints. But because it was meant to be used to paint animation cels (the individual frames that make up cartoons), the paint is very opaque. This means fewer layers of paint that need to be applied and therefore I don’t have to worry about paint buildup distorting the original sculpt. Aside from being opaque, cel-vinyl dries quickly, keeps its color over time, and is slightly flexible. The flexibility allows for handling without much chipping. And the paint is very versatile. It can be used for a wash, a dry brush, or even through an airbrush. I love it!\" ( URL_0 ) So I went to the manufacturer and got those paints! Sure enough they are extremely even and bold, and because they supplied the painting professionals their colors were always consistent. Edit: a words",
"Cel vinyl paint. It was all premixed and put into tubes, ready to be used by the colorists. so there was no need to mix colors when it was time to paint. that's where you would run into inconsistencies with paint color. There were no brush strokes in the color because for one, it was painted on the back of the cels so the camera, and you the viewer was really just seeing the underside of painting behind some thin plastic. Also cel vinyl had a thick, almost glue-like consistency so it flattened out quickly and evenly when painting. Artists didn't need the built up layers that oils or even acrylic needs to get rich, even color. I painted a lot of artwork with cel vinyl, just because of those qualities. It was the best! Sadly the only company that produced cel vinyl paint, Cartoon Colour Company just quietly went out of business a couple years ago.",
"Also the paint colors were available in slightly different variations to accommodate the layering of animation cels. If a character had a blue jacket for instance the blue would be Blue 0. And if you were going to animate just the characters arm. You would separate and animate the arm movements on a cel above the previous cel but if you used Jacket Blue 0 the top layered cel would shift the color of the blue layer beneath it when photographed. So you would paint the arm with a slightly different blue, a specially formulated Jacket Blue 1 to accommodate the slight color shift and in the final result the two Jacket Blue pigments would appear identical."
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bq3lm2 | why do diesel motors have a much more “heavy duty” sound than regular gas motors? | Technology | explainlikeimfive | {
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"Diesel engines have no spark plug. Compression alone causes diesel fuel to ignite. As a result the compression needed in a diesel engine is much higher than a gasoline engine. To handle the nigh pressure inside the engine they must be made much heavier than a gasoline engine and the fuel explosion sound that is made is louder.",
"Diesel engines don’t have spark plugs. They compress the gas to ignite it, meaning the pistons have to push harder, meaning more vibrations and rattle.",
"The compression ratio in a diesel engine is much higher than that of a gasoline engine. Regardless of engine size, that's why each cycle sounds \"louder.\" Somebody else explained it as a bomb (diesel) vs a fire (gas). That's a good analogy."
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bq4ohb | Why are laptop cameras are still so consistently low quality even though it's 2019? | Phone cameras despite having size constraints are always getting better every model. Even tablet cameras are still far superior than laptop cameras | Technology | explainlikeimfive | {
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"I'm no expert, far from it, but I'll hazard a guess that it's about cost to produce vs the use and saleability of the product. A laptop camera is generally only used for video calling, so you don't need image stabilization, HDR or 27 bazillion pixels. A relatively cheap and basic 1080p sensor is perfectly fine for what it's used for. Smartphones on the other hand are used much more as actual cameras. For this reason all those fancy features become useful and people will pay for them. Having something the competition doesn't makes your phone stand out in a saturated market and justifies the increased cost of manufacture and the higher retail price.",
"Most people dont actually use those cameras for photo taking but rather just for video chat purposes. Due to the limits of the internet your not gonna be getting great quality out of no matter what so why even bother putting a high quality camera in that's gonna raise the price? Phones are actually probably the main way people take pictures these days so it makes sense to give them good cameras.",
"When's the last time you needed a high quality image taken with your laptop camera? When's the last time you've taken a picture with your phone/tablet camera? Simply put, there is more demand for higher quality cameras on those devices than there is for on a laptop. One of the major differences between those devices is the quality of the camera and its post-processing software. A majority of people, when buying a laptop, probably do not know nor care about the quality of their laptop's camera, as they may never even use it."
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bqahi6 | NASA's permanent moon base; how will they handle the lower gravity? | I saw NASA's video about wanting to have a permanent moon base by 2024, but this made me wonder: How do we get around the lower gravity? People who work at this lunar base for years will eventually run into issues with their muscles and bones. Transporting people back and forth all the time to avoid this seems it would be far too costly, so I'm assuming people who work there will be staying for at least a year, if not more. What are some ways NASA could handle this? | Technology | explainlikeimfive | {
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"Well, Moon gravity is better than ISS gravity (= no gravity). On the ISS there have been many experiments that have found things that limit the damage from no gravity, and a one-year stay is common. No doubt, more would be needed on a Moon base. The whole purpose of a Moon Base is to conduct these experiments and figure things out when the safety of Earth in only 3-4 days away. We have to know these things before a Mars base is even something to be meaningfully considered. You can't just return from Mars whenever you want, because somebody got sick.",
"We actually don't really know for sure how bad low-gravity environments are. We know that *zero*-gravity environments aren't great in the long-term but we haven't been able to do any real testing of situations where you've got *some* gravity. We can speculate that it could cause long-term problems, but it's just one of many reasons why they want to put people on the Moon in the first place: to find out. Astronauts who spend months on the ISS do exercises to keep their bodies strong, and we can expect lunar astronauts to do the same. I would imagine that, at least at first, crew rotations would last for months and not years. With respect to travel time, going to the Moon isn't actually all that longer than going to the ISS...it's about three days versus about one day (you can't just launch directly to the ISS, you have to go up and then align your craft with the station)."
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bqdg1j | How do objects get the same amount of power from one port as it would from an extension cable that splits said port in 3 or 4, wouldn't it just cut the power in half or in quarters giving less power to the object? | Technology | explainlikeimfive | {
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"Most things don't use the entire amount of current that a breaker can deliver. Don't think of the power from an outlet like it's a set amount... The amount of power being delivered from the outlet depends on how much power is required by the things plugged into it. You only run into trouble if there's enough load on a single circuit to trip the breaker. And you'll see that happen if you're microwaving, using the toaster, and running a few other kitchen appliances at the same time",
"Current vs voltage. I'm going to use NZ values, US and Europe use different, and compare it to water. Your wall plug can deliver 240volts at 10 amps - let's call that a 240m high pipe and watertower that can flow at up to 10 gallons a second. Voltage is how much potential energy it has (240m of gravitational potential energy) amp/current is how fast it flows. What your power board does is magically divide that 10 gallons into up to 4 potential pipes (4 point plug) Plug your TV into one point - let's say 3 amps at 240 volts. The power board makes one pipe that can deliver 3 gallons per second, rest is still sitting there ready. Take note, the height of the pipe didn't change, only how much of the flow is being used, and only 3 gallons per second are flowing - rest is sitting there chillin. Let's plug in something else - a heater. High draw, let's call it 5 amps. Height hasn't changed, still delivering 240v, but now 8 gallons per second are being used. Now I want to plug in something else - my xbox is three amps. Oh no, now we're sitting at 11 gallons through a 10 gallon pipe!!! What happens? In short, the xbox pulls the water through faster than the pipe can handle. It's like blowing up a balloon too hard - your cheeks start to hurt as they are doing too much! The wires, board and stuff start to heat up. This makes it harder for the power to flow, the power gets pulled harder, repeat until something melts and the circuit breaks. Practically speaking, your fuses will blow before then - they detect too much water flowing and close. But a shit mulitboard, wiring or seized fuses happen - and fire."
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bqf89e | why usual purchases with a card need something memorable (PIN code), but online purchases have their secret code printed right on the card? | The way I understand, the usual (non-contactless) payment is a prime example of 2FA: you present your card, and then either sign or enter PIN code. First option ticks something you have (card) + something you are (the person who can white a signature matching the card's one), second - something you have (card) + something you know (PIN code). I get that online purchases can't match the signature - but why between PIN and CSC you'd pick the latter as a security measure? It reduces the security to single factor (if I steal a wallet I can spend all the money on the card until it's blocked, having the object is all I need), and doesn't even add any speed to the transaction. What's the benefit of CSC as the verification? | Technology | explainlikeimfive | {
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"This is something that is changing in the EU. They are going to add in 2 factor authentication for cards. For example one of the cards I have requires me to unlock my banking app using my pin or fingerprint and approve the transaction. Effectively requiring someone to steal and unlock your phone and card. Currently it's not uncommon for Visa or Mastercard to add a secondary check where you enter a password as part of the transaction."
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bqfkxo | how is this 'climbing a flat videoscreen' effect achieved? | Watching the Eurovision last night made me think of this entry from 2016 by Russia. Great song and the staging was fantastic. But can I hell figure out the 'climbing the wall' bit from about 1:40 in - it's a flat screen isn't it? But it can't be! Then what turns at 2:00? The screen? A second screen? A projection? Driving me mad! URL_0 Many thanks! | Technology | explainlikeimfive | {
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"The white wall isn't actually flat, there are platforms that poke out for him to stand on. Its been painted white in such a way as to appear as flat as possible to a camera or a distant viewer, and you'll notice they only do camera shots that face straight on to try and maintain the illusion of a flat white surface. They then make custom graphics which are projected onto the surface and the artist choreographs his dance to the graphics.",
"Great practical effects. Really pointless song, but great effects. It is probably just the projected image that is turning. And I suspect that at least some of the steps, hand holds and supports are items that lie flush with the screen normally, and are pushed forward from the screen when needed. Whatever i actually done, note that the camera is part of this performance - many of the tricks here are forced perspective, which requires the camera to be in exactly the right place, and zoom and pan in exactly the right ways."
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bqgg1e | Why is it that the first 10-20% of most IPhone battery’s are used up within the first 20-30 minutes while the last percent can sometimes last up to 15-20 minutes? | Technology | explainlikeimfive | {
"a_id": [
"eo4m5pn"
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"text": [
"Two things are happening. First, it is not easy to tell how charged a battery is. The only thing you can really tell from a battery is the voltage. From that, and previous study of the battery, software in the phone and the battery can estimate the remaining charge. Secondly, as the charge in the battery gets low, the phone switches of bits of functionality to make it last longer."
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bqgmqt | How are soda cans recycled when they have a plastic film inside them? | Technology | explainlikeimfive | {
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"eo4c3on"
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"text": [
"There are dozens of YouTube videos about that, but the basic process involves melting everything down and separating the aluminum from the not-aluminum. A technical term for undesirable matter in melting and smelting is *dross*."
],
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