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9gke83 | How does the internet work? | Technology | explainlikeimfive | {
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"People with computers pay to be connected to the Internet. It's like TV, where you pay a company and they offer you different shows you can watch. The only difference is that the Internet is two-way. You not only get to watch things other people send, but you get to send things to other people. The addressing, like the phone system, assigns everybody a number. But, also like the phone system, there is a cross reference of names to numbers so that you can type \" URL_0 \" and the service will look up Google's number (172.217.8.14). This two-way system allows more functionality than TV, like shopping. On TV you see something you like and have to call a number to order it. On the Internet, you can just click on something to buy it. To provide more functionality, you need a more awesome device. The phone and TV are pretty dumb devices, but to use the Internet you need a web browser, usually some kind of computer (well, in reality almost everything is a computer, so this isn't much of a distinction)."
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9gm0mk | How does the Emergency Alert System work? What exactly happens when an emergency alert is sent out? | Technology | explainlikeimfive | {
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"* a US government agency (FEMA, National Weather Service, the president) decides to issue an alert * message is encoded into a special digital format called a SAME * the SAME is broadcast over designated frequencies to a handful of radio stations designated as primary recipients...they are required to have backup power and other features that will allow them to broadcast in an emergency * other radio and TV stations are required to monitor at least other stations, and relay alerts they receive * all stations that receive an alert relevant to their geographical region are required to broadcast it...radio station broadcast the characteristic tone plus message, TV stations can put some messages in a crawl * stations that fail to broadcast alerts or misuse them are fined...one station got fined for re-broadcasting the alert tone that was included in a movie * stations are required to test the alert system weekly * Canada and Mexico are integrated into the system and have similar laws governing them"
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9gmo3d | If condoms are still only 98% effective even when used perfectly, what is the “ineffective” 2% caused by? | None of the previous posts that I’ve found answer this exact question, and I’m not finding any good explanations on google. I’m not referring to the condom breaking because that would be an obvious failure. I’m asking if there are ways for sperm to get through even when used perfectly. | Technology | explainlikeimfive | {
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"A lot of this has to do with the way birth control uses percentages. It's not really 2%. The way you'd read it is for every 100 couples having sex over the course of a whole year, 2 of them using just this one particular form of birth control (and nothing else) will become pregnant. This is a lot less than 2% the way most people think of it, because the couples who did get pregnant had sex plenty of times and didn't get pregnant. & #x200B; As far as condoms, they can break. Most condom problems come from incorrect usage, so if you are saying \"used perfectly\" means \"always used correctly\" then it must come from breakage.",
"The 2% is for when it breaks, or isn't properly removed. You're supposed to hold it in place while you pull out (once finished, not every time). If you just pull out, it might stay behind and spill. This is usually referenced on the package itself",
"Nah it's more like a 99% effective but they just can't say 100% because there is a chance the condom breaks or a manufacturer defect. At least that's what I've heard"
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9gmuc7 | why did going outside with a Game Boy (not backlit) make it easier to see the screen, but going outside with a phone make it harder? | Technology | explainlikeimfive | {
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"Gameboy and calculator screens reflect light, just like how every other normal object works. Thus, just like any object, the more light you have shining on it, the better you can see it. Just like shining a light on a book makes it easier to read at night. Phone screens, on the other hand, *generate* light. Having outside light shining onto the phone screen kinda overpowers the phone's lights a bit, making it harder to see. Just like how having a ton of lights in the city overpowers the incoming starlight, making city nighttimes look black and starless. Edit; holy shit thanks for the updoots",
"The phone is designed so you can read the screen using the backlight, but in the presence of another light that's brighter than the phone (such as the Sun) the backlight can no longer do its job. Calculators, watches and older gameboys were designed without a backlight, so they have a reflective layer that is designed to rely on light from an outside source. That's why attachments could be used that shine a light on the screen to help you see. The original version of the GBA SP also used the same type of screen and had an integrated \"front light\" to allow you to play in the dark.",
"Gameboy devices used transflective displays, so they reflect light as well as emit it. The majority of phone screens are just transmissive (only generate light) URL_0 Phones don't use transflective displays because they're more expensive and produce lower quality colors",
"Game Boy screens were designed to reflect light. It's like how if you go into a dark room with a mirror, it will be hard to see. If you go into the sun, the mirror will reflect more light. Meanwhile, backlit screens on phones emit light. It's like how if you go into a dark room, the light will be the brightest thing, but if you go into the sun, it will appear washed out. The reason why this happens is because when it's dark, your pupils (eyes) open up to allow more light to enter. It matches the brightness of the brightest object, which is the screen you are looking at. When it's bright due to the sun, your pupils close up and allow less light to enter. This means very little light from the screen can get in and it seems dark by comparison. I think the Game Boy Advance SP (or one of them) used to allow users to toggle the backlight for this reason.",
"Gameboy and digital watches rely on light around you to see what's on the screen. The black pixels are there to keep light from going past and bouncing off the grey background back to your eyes. LCD phones rely on a lightbulb/tube/LED behind the screen glowing to show you what's on the screen. The bright sun makes it great for Gameboy and the black on grey LCD watches but the sun is brighter than those light bulb/tubes behind the LCD screens on phones so it gets washed out.",
"Gameboys, like many phones, use LCD screens. Without going into the technical details, all LCD screens need a light source shining from behind the display. There's two ways to do this: 1. Put a light globe (or fluorescent tube or LED) behind the screen (ie phones). Light comes out of the light globe, through the screen and into your eyes. 2. Put a mirror behind the screen (ie gameboy). Light goes into the screen from the sun or whatever, bounces off the mirror and then comes back through the screen into your eyes. When you go outside, it's really bright so your pupils contact and you can't see dim lights any more. LCD screens become too dim to read unless you increase the brightness of the back light. With a mirror as the backlight, this isn't a problem. In bright sun, more light is going in and reflecting off the mirror, meaning a brighter display. With an actual light source as the backlight, you need to actually make the light source behind the screen be brighter. Some phones do this automatically, but a lot don't. Those phones are hard to use in bright sunlight. Also, there are other types of screens that don't use backlighting, instead the screen itself glows. They have the same problem, when you go outside you can only see really bright objects, so your screen becomes unusable unless it knows to start glowing brighter.",
"Different screen tech. Reflective vs Transmissive. Gameboy used a passive reflective display, meaning it planned on selecticely bouncing ambient light to your eyes. Your phone is a transmissive display, which is designed only to use a backlight as its light source. The reflective screen is just like \"more light to use!\", While the phone's transmissive display is like \"damn, more light to compete with\".",
"I mean, your title even explains it; Gameboys weren't backlit and needed and external light source to be visible. Phones are the opposite so the inverse is true; they get less visible with more ambient light",
"New Phone screens have backlights behind the screen which does not reflect light. Whereas old LCD screens have reflective surfaces behind the screens.",
"When you turn off the device, what colour is the screen? well, the gameboy is a light grey LCD, and the phone is almost pitch black. Ok, and what about the reflection of the screen, is there much reflection? In the gameboy there is a reflection but it isn't as sharp as a phone screen, which almost looks like a black mirror. Now, when you're outside with the sun shining, the gameboy screen will reflect the light from under the coloured pixels, so imagine that light that \"comes\" from it is actually the same sunlight that reflect out of it will show the colour of the pixels. Your smartphone, on the other hand, has a black screen, so the sunlight won't reflect after they went in, behind the pixels, actually it'll reflect out of the front, showing you a mirror from your surrounding, and the colours of the pixels can only be shows from the smartphone's own backlight, which also isn't as bright as the sun seen from earth. So basically, one of these was engineered to work with outside light sources, while the other one was engineered to work despite of outside light sources."
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9gn42d | how do those copper joint sleeves work? Do they do anything that neoprene can't? | Technology | explainlikeimfive | {
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"There is no compelling scientific evidence that 'copper infused fabric' does anything particularly special. This includes claims of promoting healing, reducing pain, or minimizing illness."
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9go12l | How do sites know when you're using an ad block extension? | How do sites know that you're using an ad-blocker, and could they use the same process to show you an ad in a similar way to how ask you to shut the ad-block off in the pop-up? | Technology | explainlikeimfive | {
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"They typically do it by using an algorithm that baits the adblocker into blocking a honeypot and checking if the honeypot is still there. When the webpage loads, it loads a script that is blocked by the adblocker, then another script is loaded to check if the script is still there - if it's not it displays a message",
"The ads usually provide a callback function that allows the programmer to determine whether or not the ad loaded when the page loaded."
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9gotcq | How is an AC motor reversed? | I know that DC motors can be easily reversed by reversing the two terminals. However since AC is alternating, it doesn't have a polarity and therefore reversing the terminals will not make it rotate in reverse. | Technology | explainlikeimfive | {
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"If it is a three phase motor then you can change any two phases around (generally L2 and L3) to reverse the direction of the motor.",
"The question you should really be asking yourself is \"if DC has a constant polarity, how does it even spin a motor continuously in the first place?\" The answer is it doesn't. DC motors are a lie, unless you want to call a railgun a DC motor. All motors are AC, some just take a DC power supply and switch it to make AC locally. So what is a motor? It's two magnets trying to align. One of which is fixed, the other is attached to a rotor and allowed to rotate. One or both are electromagnets. So the first option is we stick a magnet on the rotor, and make the stator (non-moving magnet) a electromagnet. So we apply DC, and we get movement! But, depending on starting position, it does at most a half turn to align N to S, overshoots a little, then gets pulled back. We got a single half turn out of it at best. Not really a motor. But if we swap the DC connection direction it will turn back the other way, but then stop again. How do we get it to spin? AC. You either apply sinusoidal AC from the power grid and have it move at a fixed speed (brushless synchronous AC), or you get fancy electronics to take a DC supply use (electronic) switches to make a sqaured wave AC (brushless DC motor and drive). The magnet rotates to meet the electromagnet, but then the electromagnet swaps so the magnet needs to keep rotating to continually chase it. The motor is the same either way, it's just what's driving it that changes between brushless synchronous AC and brushless DC. How do you control direction though? Well, the brushless DC with a drive needs to be smart and know which way the rotor magnet is starting at, and then apply the current in the right way initially to get the desired turn. The brushless synchronous you don't, it's a complete crapshoot based on whether the AC voltage was positive or negative the instant you started it. Once motion starts, it will just keep going the way it was initially pushed. So how do you start this? Well truthfully I don't think anyone uses a one phase brushless synchronous motor. But to so it you need a starting winding. You wind a wire around the motor for a second electromagnet, but you offset it by a certain angle. So if you apply a DC current the first magnet will make the north pole at say the top, but the second will make it at 45 degrees to the left. Next you take a capacitor, and make a sub circuit from the main one passing through it. What a capacitor will do to AC is advance the current/delay the voltage. What this means is your current will spike first through the capacitor, then slight later in your main circuit. It's the same AC way, just advanced. What this means is your starting circuit will hit N at 45 degrees, then slightly after the main circuit will hit N at the top. We now have a preferred direction for the magnet to spin thanks to two phases, that is two slightly offset AC currents flowing through two slightly offset physical windings. To swap the preferred direction, you just reverse how you apply things between these two circuits. Alternatively, you get three phase power. That is our power grid already has three offset phases and industrial and commercial users get all three, household only get one. Each phase is already offset by a third of a cycle, we call them A, B, C usually. So A first peaks it's N at the top of the motor, then B peeks it's N a third of a cycle later at 120 degrees, and then finally C peeks its N at 240 degrees another third of a cycle later. And then we're back to A with N at the top a full spin later. To reverse this, we just swap any two wires. Rather than the magnet chasing A then B then C, we can make it chase A then C then B, spinning backwards. Next we could have a electromagnet on the rotor. How do we do this? We need brushes (hence why the other ones were called brushless), wire brushes that can run against the rotor to make electrical contact but still allow it to rotate. So we apply current to the spinning part, and it sits in a permanent magnet or electromagnetic stator. First if we have a permanent or electromagnet stator, and apply a DC current to the rotor what happens. Again, a half turn at best, that's it. What your standard DC motor (no drive, just hook it up to a battery and it spins) does is mechanically swap the DC to make sqaured wave AC. As the motor turns, right as N meets S, the contacts feeding the rotor current swap, flipping the rotor's N and S poles, making it spin back the other way, only to swap back again. To swap direction, you just swap the DC supply which simply reverses this operation. For AC, we typically apply DC to the rotor to give that a fixed magnet, and then have the same same starter winding or three phase windings as brushless. This is a brushed synchronous motor. Reversing is then the same as brushless, except we can also just swap the DC on the rotor. These motor are rare, but pretty much the entire power grid works on this kind of generator. Lastly, we can wirelessly transfer power to the rotor. This basically acts as a spinning transformer, AC in the stator induces AC current on the rotor. They are either three phase or one phase with a starter winding just like synchronous, and reverse the same by either swapping two of the three phases or the main and starter windings. The vast, vast majority of motors afe this kind, and most of the power consumed on the grid is by these motors. Electric cars often use these too, using electronics to make the AC from DC by making really, really fast AC sqaure waves that smooth out to look like slower, smooth AC.",
"Some AC motors have two windings one is called the primary and the other is the start winding. The start winding is fed via a capacitor which shifts the phase by 90 degrees. If you reverse the primary and start connections, the motor will spin in reverse."
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9goudu | How does a computer restart automatically, just because I clicked "restart" versus "shutdown"? | Essentially, the computer is shutting down. How, then, does the computer restart, without someone pushing the power button? | Technology | explainlikeimfive | {
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"Best way to explain it is, the power button doesn't turn things on, it sends a message to turn things on. When a computer shuts down and knows to restart, that message is already there, without the power button being involved."
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9gp9nt | Why is there no clean high quality footage of everyday life (like people walking through cities) in the 60s, 70s, or 80s when they already had film cameras back then with higher resolution than todays HD and even 4k cameras | Technology | explainlikeimfive | {
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"There is high quality footage; the Canadian Broadcasting Corporation, for instance, has a nice archive of that kind of thing. Those portable reel film recorders, on the other hand, and the sony handicams that followed them, aren't high quality, and the film tended to deteriorate rapidly.",
"There is lots of footage, but very little has been digitised or put on youtube. British Pathé has loads [70's London Fashion]( URL_0 ) for example.",
"There is [this]( URL_0 ) beautiful video from 1993 New York",
"Because those film cameras were *incredibly* expensive, not as user-friendly as the cameras we're used to now, and the entire process of film-making was just so arduous that most people never cared to do it. They were also, as a rule, very heavy and cumbersome to carry around. The fact that we're getting so much of our lives on video now has less to do with the fact that the quality is excellent and more to do with the fact that pretty much everyone carries a decent-quality camera around with them literally everywhere they go in their pocket, integrated into a device so multi-purposed that swiss army knives are jealous.",
"Probably because people weren’t so obsessed with recording everything back then?"
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9gsd48 | Why is a 4-digit code sufficient for banking purposes but not for most online accounts? | Technology | explainlikeimfive | {
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"Direct answer, they are not. Banks use 4-digit codes because it’s user friendly and was/is standard for legacy systems. However it doesn’t mean they are as unsafe as a 4-digit “password” on a website. That’s because for banking purposes usually a physical card is required, there are strict limits against brute force attacks and the damage will be owned by the customer. This distinction can be seen comparing internet banking and regular banking operations (card based).",
"I'm not really an expert on bank security, and I personally find the 4 digit pin outdated too, but there are more factors that you have to account for. Most important is probably that your bank is always in control of your account, and they are in direct contact with you as a person. Even if something happens, the bank should be able to reverse it, and they can afford to lock your account should something suspicious happen, because you can simply show up in person and identify yourself. Also, when doing physical things you require a card on top of your pin, and when doing online banking, you require a tan generator, with your card. If your card gets stolen, you can report and disable it.",
"A four digit code by itself is not secure. It's part of a greater security system. If I know your pin is 1234, that information alone is kind of useless. I also need your account information and maybe your debit card or a copy of it. It's a combination of something you know (the pin) and something you have (the card). Could there be a more secure pin, perhaps 15 digits? Of course. The problem is, when you design a system, you have to balance security with ease of use and whatever technology limitations existed when you designed that system. Keep in mind debit cards started to become common in the late 80s, early 1990s. Computers and networks weren't very fast back then. A lot of remote sites were connected via 300 bits per second modems. From memory, a certain stage coach bank used 1200 bits per second leased lines that was shared by all the tellers at smaller branches. Just transmitting the data on the back of the card, pin and transaction data took about 1-2 seconds, receiving took another second or so. Today that would occur in milliseconds.",
"Online, anyone can try to enter passwords all day long, so they need to be longer and more secure. If you manage to steal someone's debit card, you are only going to get 3 or 4 tries before the bank locks you out."
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9gti9a | Transistors, what they do, how they work, how they're used. | Technology | explainlikeimfive | {
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"Think of them as a valve. You have a flow through them, which you can turn on or off with another, much smaller flow. Now, how can we do so much with this: Well, there are two cases: analog and digital. **Analog:** You don't have to open or close the valve all the way. This means that you can use a small flow (a weak signal) to regulate a much larger flow (a strong signal). This, basically, is an amplifier. You use a weak audio signal to control a much larger current through the transistor, driving a set of loudspeakers. Of course, an audio amplifier is just an example, they are very useful in other applications as well. **Digital:** In this case, we only use the valve as an on or off. So, basically, we have a tiny, tine swithc which is operated by an electric signal. Now, you think, \"What's the use of that?\". Well, almost nothing. However, you can connect this with other switches. many of them, billions of them, creating a network (not network as in \"computer network\") of switches that can actually do things. By arranging them cleverly, you can set groups of them up as memory cells, you can add numbers in memory cells, you can move stuff between memory cells and so on. Do this cleverly enough, and you've got a computer. That's pretty useful.",
"The valve analogy is pretty good. I tell my students the following: The Syllogistic logic of Aristotle, which he developed in the fourth century BCE, provides most of the logical and mathematical foundation for computer science. It's all about reasoning based on truth or falseness. Imagine a switch like the light switch on the wall. Suppose we arbitrarily state that a switch in the off position means \"false\" and a switch in the on position means \"true\". We can now implement Aristotle's logic using wall light switches. Unfortunately, light switches on the wall cannot be turned on or off very quickly, and there are moving parts that wear out. Even though we could build a computer out of light switches, it would be very slow and it would break often. [Note: computers can be built from first principles in Minecraft: URL_0 ] Approximately 200 years ago, people started making computing machinery like adding machines out of mechanical parts like this URL_1 In the first half of the 20th century, people started using vacuum tubes in place of mechanical parts. Vacuum tubes are like lightbulbs that work as \"valves\" as others in this thread have described. These tubes can work as switches. They can change state very quickly (millions of times per second), so they can be used to make faster computing machines than mechanical parts. Unfortunately, the tubes burn out like lightbulbs, and they generate heat like lightbulbs, and they require a lot of space. Once you have a few tens of thousands of these tubes in a room, the room is full, the room gets too hot, and there is an approximately 100 percent chance that at least one tube is burned out. When the transistor was invented in 1947 at Bell Laboratories, nobody wasted a single moment wondering what to do with transistors. Transistors are switches that are tiny, can change state billions of times per second, give off very little heat, and they have no moving parts to wear out. With transistors, the same computing machines that used to fill a room can be built in a small box. As we make the transistors smaller and smaller, they get faster, give off less heat, and require less space. Now you can have 4 billion transistors in your iPhone and it can run on a battery for 8 hours while not burning your hand. All of the following can be used to make computing machines using modern versions of Aristotle's 2400 year old ideas: Mechanical Switch: - Change state thousands of times per second - Wear out - Large-ish - Cool Vacuum Tube: - Change state millions of times per second - Burn out - Large - Hot Transistor: - Change state billions of times per second - Don't burn out or wear out - Microscopic - Cool compared to most other things including the friction of mechanical switches"
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9gv1br | How do suppressors actually work? | Technology | explainlikeimfive | {
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"The bang of a gun going off is created by hot gases rapidly expanding at the end of the barrel, creating soundwaves in the air. You could imagine the inside of a suppressor like a \"maze\", in which the gases expand much slower, therefore not creating (as much) noise.",
"There are two main factors that cause a gun to make noise. The first is the sonic boom from moving faster than the speed of sound. The second is unburned gun powder emerging from the barrel, then exploding. Suppressors work by giving the unburned powder space in which to completely burn before the bullet leaves the suppressor. The baffles inside the suppressor give it multiple chambers in which to burn the powder. Unfortunately, suppressors don't really suppress the sonic boom, which is why you need subsonic ammunition to get the maximum effect of a suppressor. Edit: fun=gun thanks for the great comments though",
"When you shoot a gun, out of the barrel comes a bright flash and a bit of gas. And the bullet, of course. A suppressor is essentially a tin can with a few angled plates in it, which have holes in the centre for the bullet to pass through. The flash and the gas however, sorta get held up in all the angled plates, so you don't see a muzzle flash, and the smoke is also reduced. This does slightly reduce the bullet's velocity, giving it more drop, but it's minimal on modern suppressors. However, keep in mind that *real* suppresors are still deafeningly loud. Quieter than a normal barrel, sure, but they don't make guns silent like in movies and games."
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9h2baj | Why are the segments of a primary telescope mirror hexagonal in shape? | Technology | explainlikeimfive | {
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"Only 3 regular polygons can be used to tile a surface... Squares, triangles and hexagons. Hexagons probably are just the easiest to manage in terms an manufacturing and fragility."
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9h2lgf | What is the internal clock in gameboy advance games such as Pokèmon Emerald, and why did it cause so many problems when it eventually "went dry"? | Technology | explainlikeimfive | {
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"The night and day cycles were controlled by a small secondary battery in the cartridge and when it died the game no longer did night/day cycle. so berry harvesting and evolving espeon and umbreon couldn’t happen.",
"The internal clock is exactly that: a clock within the game cartridge, which tells the game what time it is. If the battery runs dry and can't run, then the game won't know that time has elapsed, which has adverse effects within the game. In extreme cases, losing the battery meant *losing your save file*, which can sometimes mean as many as five years of real-life progress."
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9h3yfz | Why do touchscreens stop working under excessive heat? | If I leave my phone under direct sunlight in a warm climate, the touchscreen will need to cool down before working. I thought touchscreens work using capacitative electro conduction, not heat sensors. So why would it not work? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"It's not that the touchscreens themselves stop working, but that the underlying phone CPU is slowing down due to thermal throttling. u/HatesAprilFools is right in that at least when we're cold they don't work so well [Here.]( URL_0 ) u/UltraPwnie, your phone doesn't use CPU power to cool the device, rather, it *doesn't* use CPU power in an effort to reduce the amount of heat produced in an effort to help the phone come down in temperature."
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9h57ik | How are physical data lines for the internet run all over the world, like overseas, etc. | Technology | explainlikeimfive | {
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"e6969a8"
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"text": [
"It's almost all optical fibers. People dig trenches and bury the fiber. Then when they get to the coast, they use special ships to plant fiber cables on the bottom of the ocean. They avoid the deepest bits, but there is thousands of miles of undersea optical cables. [This great map]( URL_0 ) on Wikipedia shows the most popular paths."
],
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"https://www.reddit.com/r/MapPorn/comments/73ekox/map_of_underwater_cables_that_supply_the_worlds/"
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9h7bjy | What is ARP Cache Poisoning? | Very basic knowledge of computers, networks and associated jargon, so very small words are appreciated. | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Every network device has a MAC address, it's just a number, and every network card is built with it's own unique number. When you connect to a network (like your home Network), your computer asks for an IP (an address on the internet). Unlike a MAC, IPs are made in such a way that you can narrow down where to send data based on just part of the address just like how mail says to Bob, 123 St, NY, NY, you can read it and send it to the NY office and let them figure out where in NY to send it, you don't actually need to find Bob's house on a map. Anyways, things in your home typically sort data just by MAC, they have a list of every MAC on your network (every computer in your home for example), and what wire it's connected through. Now people access stuff with IPs, so when you go online you need to first take the IP, then find what IP it needs to go to (your modem, to get to the internet), then you need to find the MAC of your modem, and then send the data to the MAC. The ARP cache is the list of IP to MAC mappings for all known devices on your network. The ARP protocol is used to allow other devices to tell you their MAC. ARP cache poisoning is a network attack where you just listen on the network for other people's IP and MAC, and then lie and use the ARP protocol to tell everyone actually you have that IP. This will typically cause all devices to then send data to you, even if it wasn't supposed to be destined to you, you then look at it and or change it, and then using your old list of MAC-IP mappings send it to the right destination. This means that you can connect on WiFi on a home Network and see the traffic destined for the internet, even for devices not on WiFi (so you can force wired devices to transmit their data over WiFi for you to see)."
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9h7da1 | How do ads know where I am? | (Insert place name here) man stuns doctors with this trick! | Technology | explainlikeimfive | {
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"text": [
"When you accept cookies you actually accept the site to let ot know your location (markes by an IP or some sort of Country-related link)"
],
"score": [
5
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9h8usx | It’s just as difficult to connect to a new Bluetooth device today as it was 10 years ago. Why has this technology seemingly not advanced over the years despite its use increasing dramatically? | Technology | explainlikeimfive | {
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"Bluetooth spec is crazy complex. The first version with all the profiles was 1500 pages. Plus it was written by phone companies who did not understand TCP networking but instead knew a lot about serial connections. So one of the base protocols is a full serial emulator. It’s really crazy. From the programming standpoint, Bluetooth is the hardest protocol I know of to implement.",
"The process itself is extremely simple. For something like say, a car or something, the bluetooth options may be hidden in some menus, but the actual connection process itself is extremely simple. Turn the device you're connecting to in pairing mode. Pair to the device. If applicable, enter the PIN displayed by the device. You are connected. Connection difficulties are generally the result of mega-cheap bluetooth chipsets. Your $15 bluetooth headphones might work perfectly fine. Or might be cranky pairing intermittently/always. As with anything else involving technology, quality of hardware, firmware, and software may vary. Do research before you buy."
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9h9dpc | Why hasn't the voice quality of phone calls improved? | Technology | explainlikeimfive | {
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"It's a legacy thing. IIRC, Plain Old Telephone Service (POTS) have 3 KHertz of bandwidth allocated. That's because back in the day, Bell Labs determined that was enough to provide an adequate voice telephone call. According to Wikipedia, POTS is \"restricted to a narrow frequency range of 300–3,300 Hz, called the voiceband, which is much less than the human hearing range of 20–20,000 Hz\". So still, a voice call being routed through the system gets that much bandwidth. It really wouldn't help if one provider increased it, since it would get cut down at any place in the system that still used the old 3 KHz (including in the phone's firmware itself). If everyone agreed to increase POTS bandwith to something like 8KHz or 10KHz, voice calls would have significantly better audio quality. But good luck getting that to happen.",
"It has! It's called HD Voice, and it's available now. So why haven't you experienced it? Well, in order for it to work, your phone has to support it, your phone company has to support it, and the party you are calling has to have a phone that supports it. And if that party is using a different carrier, then their carrier must also support it, *and* their carrier and yours have to have an agreement to connect calls between their networks at that level of quality. If any link in the chain (Your phone < > your carrier < > the interconnection between carriers < > their carrier < > their phone) does not support HD Voice calling, your call falls back to regular old voice channels.",
"Assuming you're talking about cell phones: Because there hasn't been enough consumer complaints/demands to make it happen. For most people, it's good enough. Besides the fact that less and less people even talk on the phone and instead rely totally on texting or some other form of internet messaging.",
"In South Africa voice quality has actually improved, in 2014 HD calling was introduced using the Adaptive Multi-Rate Wide band coding standard, this makes use of 3G/LTE networks but is not a data call like Skype or Viber, it is a normal phone call. It's pretty good and has become the norm in most locations. I guess it might be because in Southern Africa cellular calls are still a big deal for many people.",
"Sound transmission and quality has drastically improved! We can really work some fantastic magic with speakers and a microphone. But in regards to cell phones, 99% of consumers don't want the best. They just want \"good enough\". And \"good enough\" speakers/microphones take 90% less engineering and materials to manufacture.",
"As I wrote this out I got sort of side tracked and nostalgic, so take this with a grain of salt and don't go writing your doctoral theses on it. But as best I recall form living it, this is the history of call quality. & #x200B; We used to have POTS (Plain Old Telephone Service) AKA PSTN (Public Switched Telephone Network). The S in PSTN is interesting, because it means once your call was set up there was *literally* a copper connection going from your microphone to the listeners speaker. It was switched first by operators (the gals with the big earpiece and the connection that looked like it was form a guitar amp) Later computer switching - but you really did have a dedicated and unchanging copper path through how ever many miles and how ever many companies to the other end. Quality of the call was a big selling point, especially for long distance and companies [boasted]( URL_0 ) about how good it sounded. & #x200B; Also you had an analog connection. So in the same way old movie or picture film has more detail than low (or even sometimes high) res video, the call quality had more character to it as well. When the conversation dies down, you can still *hear* the room. The ambient sounds are full and have depth I can't describe, but you *knew* the line was open and still connected to the other end. & #x200B; So then we get cell phones. They sounded like tin plated crap. But having a phone the size of a brick in your car or strapped to your hip was pretty cool so we gave the quality a pass. & #x200B; Then the old copper systems got more expensive to fix and maintain and VOIP came along and gave us a way to share voice on the data (Internet) network. Big Savings guaranteed the Telcos would switch and because of cell phones we had been somewhat desensitized to crappy call quality - so VOIP took off. & #x200B; So it's not just that quality hasn't improved, It's actually gotten worse. & #x200B; Now here's another interesting bit (pun intended). VOIP systems break down sound into a binary data stream. It's no longer analog like it was with copper, it's now digital. So the deep and rich \"quiet sounds\" were replaced with actual nothing. Quiet rooms didn't' produce enough sound to transmit, so the system literally sent blank voice packets. Instead of hear the subtle ambiance of another part of the world there was simply nothing. So we made up sounds to fill the void - [Comfort Noise]( URL_1 ).",
"In the 80s and 90s, when making international calls there would be a few seconds of silence after you spoke until you heard a response. Now you can talk to anyone in the world anywhere and have a crystal clear conversation without any lag. Now, consider on a cell phone with a shitty connection (e.g. one bar). You can still make that phone call and the conversation will still happen. SOMETIMES it gets a bit chunky or breaks apart but those are often in the worst case when you lose service. So understand that while you don't need to hear the person in Dolby Atmos THX Surround sound, you are able to hear and understand the person in very adverse connections. This means all the advancements to telephony are mainly under the hood."
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9h9ekw | Why do you sometimes have to bend audio jacks to get them to work correctly? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Probably the wire inside the jack is broken. When you bend the jack you join the both sides of the wire and reconect it again . It will work until the wire get too far away or too broken to get reconected by bending again."
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9h9prn | How a website blocks me via cookies and is there a work around? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"How is the website blocking you? Can you delete the cookies for that website?",
"Usually if you're blocked it's by your IP address and not cookies. Unless it's a pay wall site, in which case you can pay for a subscription or use private/incognito browsing.",
"If you use incognito\\new private window (Chrome\\Firefox) mode on your browser each time you go to that page, it should delete the cookies when you close the window. That should allow you to repeatedly hit that site with no issues."
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9haehz | What is ray tracing and how is it different from rasterization? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Imagine that rasterization is like the pixels in a digital photo image. Ray tracing has more in common with how a photographer or cinematographer light a scene before taking an image than it does how you take the picture. It doesn't matter whether it's a digital camera, or a film camera, or a highly evolved primate with some water colors. Static light maps are a bit like faking the light in a scene by shooting it with very even lighting, and then using photoshop to make some parts brighter, and others darker, to try and replicate the way that light might bounce around the room. It's a trick like drawing an artificial shadow behind a person in a room with no shadows. Ray tracing would be like bringing real lights into the scene, and letting it reflect around bouncing off the walls, the subjects, and arriving from several directions from direct and indirect lighting, hard and soft lighting, all depending on the path the light took to reach what it's illuminating. Instead of spending extra work, trying to photoshop a realistic sun and sky and shadows around your photo, you simply use a real light . Less work, and it looks more realistic than trying to draw fake light by hand. Ray tracing is not a replacement for rasterization. Ray traced images may be rasterized or vectorized because it's not a rendering method. Ray tracing can be thought of as a way to light a scene. But because ray tracing has to measure the way rays of light bounce off an object and around a scene, for each and every pixel.....with millions of pixels...dozens of times a second....you can start to appreciate the amount of processing power that takes to render in real time."
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9hb479 | How do Hard-disc Drives (HDD) store data i.e. images compared to solid-state hard-drives (SSD)? | Looking for a layman's explanation please? My lecturer banged on about how HDD's 'read/write head aligns magnetisable domains in one direction for 1's and other for 0's' which literally makes no sense to my computer naive self. I do remember my dad recommending me to get a SSD instead because they're faster and slimmer. But I have no idea how these hard-drives 'physically' store the data and why solid-states are faster? Thanks peoples | Technology | explainlikeimfive | {
"a_id": [
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"Hard disks are magnetic. Compare to an audio cassette tape, where the magnetic tape just scrolls by the recording head, and the head magnetizes its 1's and 0's on the tape as it scrolls by, like this --- - ---- - ---- -- ---. Then you have VHS video tape, where the tape still moves by the head, but now the head spins at an angle, so the tape gets magnetized with lines of information (1's and 0's) like this ///////// with each spin of the head. So hard disks are actually disks, like LP records but magnetic instead of plastic indentations. And each hard disk enclosure has a stack of, like, 3, 4, or 5 of these disks, all welded to the same motor so they spin in unison. And the magnetic heads are on an arm that can swing across the surface of these disks, to reach any piece of information. So to write information the head magnetizes the surface of these disks with magnetic NORTH for 1, and magnetic SOUTH for 0. It's just like tape, but it's arranged on several disks. [Wikipedia article]( URL_1 ) explains it in full detail. Solid-State Drives (SSD) are electronic. The SSD has some memory chips inside, and the memory chips have transistors and really tiny capacitors that can actually store electricity. A few electrons are stored in the capacitor, and the transistor attached to it detects these electrons (via the electric field, basically), and responds with a 1 or a 0 (transistors in integrated circuits are, basically, on/off switches that are controlled by electricity rather than by a person flipping the switch). [Wikipedia article]( URL_0 ). So the SSD is faster because the information is stored with electricity, and electricity reacts basically at the speed of light (it's slower than that because the electronics does take some time to do its stuff, but the speed of light is the limit, more or less). Whereas hard drives HDD's are limited by physical constraints: how fast the motor is spinning, how fast the arm with the magnetic heads can swing a certain angle (with precision), etc. Think of an LP record vs. music on your phone; the phone can find your mpg song and play it almost instantly; the LP record you have to wait for it to spin up, then the needle-head has to move to the correct spot, lower itself, and then you can hear the song.",
"Imagine a hard drive as a giant field on switches. I can alter the state of any given switch, however, i have to walk between switches to read or alter the position of any given switch. Solid state drives are a bit harder to explain. There are no moving parts, and blocks of flash memory can be written to, and that data persists even without power."
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9hb87e | Why do graphics drivers push out updates so frequently? I don't *notice* anything different after an update, so what's happening under the hood? | Technology | explainlikeimfive | {
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"About 95% of the time, they are fixing bugs that they didn't find before because their testing is generally inadequate. The key thing they are striving for is getting a product to market as quickly as possible, and quality is not job #1. They want the quality to be just good enough that they don't get a bunch of bad reviews or too many returns. The rest of the time they are adding minor features that may not be noticeable, or even applicable to what you are doing. *Source*: I worked at nVidia for a while.",
"Simplified enormously, your graphics card has memory, and processors inside, and the graphics you see, especially in games, aren't \"loaded up\" like a video that's already made and just available for download, but the game actually creates the 3D environment that you see, and, more importantly, DEFORMS it when you change perspective or look around, and objects become obscured or visible based on what you're doing. So the processors are needed, to do all the mathematical deformations, so that your environment inside the game appears to be moving and reacting and having physics the way you'd expect. And all of these mathematical calculations can't work unless there's a \"standard\" - an agreement between the hardware makers (NVIDIA, ATI, etc.) and the software makers (game developers) about how things SHOULD work. That's what a \"driver\" does; it takes a command like \"draw me a sphere, made of water\" and translates it to \"processors number 1-23, work on drawing a sphere; processors 24-62, work on the transparency of water; processors 63-92, work on how light should be rendered when it passes through water\" and so on. So, new games come out all the time. And these new games want to draw new things in new ways all the time (graphics is a big deal in games). So NVIDIA and ATI periodically update their drivers to support these new games that \"push the envelope\" and basically change the supposed \"standard\" to where it's not agreed by all parties anymore. If you look at patch notes for a graphics driver update, you'll see it's mostly fixes intended to make these newer games work on the video card.",
"Graphics drivers these days don't just simply provide a generic OpenGL/Direct3D interface for the card & just let the games use the card as a resource. Graphics drivers are chock full of optimizations & bug fixes for different games, hardware & softwareconfigurations. If you look at the release notes for the most recent nVidia drivers, for example, you'll see that the highlights are: * Added support for RTX 2080 & 2080Ti cards * Provides the optimal gaming experience for Assassin’s Creed Odyssey, Forza Horizon 4, and FIFA 19 but the entire release notes are 36 pages long. In addition to those things you get: * new version of CUDA libraries * support for new raytracing libraries * new version of VULKAN libraries * OpenGL extensions for raytracing with RTX cards * SLI/3d profiles for a bunch of games * Experimental support for OpenCL 2.0 * new backwards compatibility code for DX10/DX11 games * New HDTV resizing code * dozens of specific bug-fixes ...and these sorts of things are constantly coming out. If the rate of releases bothers you & you're not having any problems, it's probably safe to stay with the WHQL versions of the drivers which come out far less frequently.",
"Its generally not a tech reason, its a almost always a pure **business** reason for *frequent* updates In ages past, software and driver updates were few and far between, so most gamers and computer folks thought they were being neglected on their high priced cards with minimal updates and support. Now they didn't need updates generally, because things move pretty slow and the drivers and software work extremely well in almost any condition, even forward looking, thats how they are made. But when an update came, it was a happy day, even if it did nothing. But, as competition in graphics cards increased, and prices rose, they got this idea to essentially \"fake\" they were providing amazing support and updates on a regular basis-- and the fans, and users utterly loved it, thinking they were getting WAY more than they paid for (again these cards are not cheap) i.e. \"OMG they update it every week so it always works right, instead of every 6 months!\" Its soooo worth it. In reality, these updates are generally extremely minor bugfixes and tweaks that don't effect but the tiniest rare outlier user configuration and do not need consistent frequent updates since they are so small and so rare they can be rolled up into a single update very infrequently. Its not a tech thing. It's pure business to placate the user that the company is doing something to help them game better. The placation of users by providing constant \"updates\" is a normal business practice in many industries, so that consumers don't get worried and riot and then start calling the company, and so on. Ever been at an airport and the plane's been delayed and they come on every 15 minutes to update you?! Nothing changed right? but you got an update -- this is **Exactly** the same."
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9hcgzb | what's the difference between an OLED screen and just a regular LED or LCD? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Yer not alone in askin', and kind strangers have explained: 1. [ELI5: What's an OLED display and how is it different than a regular LED one? ]( URL_6 ) ^(_22 comments_) 1. [ELI5: Difference between LED, AMOLED, LCD, and Retina Display? ]( URL_1 ) ^(_ > 100 comments_) 1. [ELI5: What do OLED screens do that make them an improvement over LCD screens? ]( URL_3 ) ^(_._) 1. [ELI5: Difference of LCD, OLED, and AMOLED that can be easily understood ]( URL_5 ) ^(_8 comments_) 1. [ELI5: What is the difference between LCD and LED displays? ]( URL_4 ) ^(_7 comments_) 1. [ELI5: What is OLED? ]( URL_0 ) ^(_6 comments_) 1. [ELI5: How do OLED work? ]( URL_2 ) ^(_2 comments_)",
"LCD has a white light behind, and acts like coloured cellophane. OLED is like a coloured light which can turn off."
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"https://np.reddit.com/r/explainlikeimfive/comments/2qofoo/eli5_what_is_oled/",
"https://np.reddit.com/r/explainlikeimfive/comments/7m57ks/eli5_difference_between_led_amoled_lcd_and_retina/",
"https://np.reddit.com/r/explainlikeimfive/comments/2khoxh/eli5_how_do_oled_work/",
"https://np.reddit.com/r/explainlikeimfive/comments/7dibzk/eli5_what_do_oled_screens_do_that_make_them_an/",
"https://np.reddit.com/r/explainlikeimfive/comments/8x2fr0/eli5_what_is_the_difference_between_lcd_and_led/",
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9hcitw | How can the FBI seize a website? | Technology | explainlikeimfive | {
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"text": [
"The website is stored on a server which is physically located somewhere. If it's located in the United States then the FBI can get a warrant to take possession of it (or at least the section of it that the website is on) to shut the service down. If it's located in another country then they have to cooperate with the local authorities and come up with an agreement to take the site down. In some cases the authorities in the other country won't cooperate because they don't care."
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9hd6vf | What causes computer storage to become 'corrupted (ie: external harddrives, flashdrives, etc), and need to be reformatted (erasing all that is on the drive) in order to be used? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Files can be corrupted for a lot of reasons. It typically happens when a file is left in a weird state where the system doesn't know how to read it anymore. A program might have broken or been interrupted partway through writing to the filesystem, a file could be damaged by a malicious program like a virus, or an old file might not be recognized after a system upgrade. However it gets in that state, the file is now basically dead code."
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9he6bn | How do hackers "inject" code into a webpage, like in the Newegg checkout process? | Technology | explainlikeimfive | {
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"text": [
"There are two main types of code injection vulnerabilities for websites: SQL injection and cross-site scripting (XSS). SQL is the language used to retrieve information from the database. In general queries are formatted like this: > SELECT [attributes] FROM [table name] WHERE [condition] For example if you search for \"hammer\" in a DIY catalog, it may look like this: > SELECT brand, name, price FROM tools WHERE type= \"hammer\" In this case, \"hammer\" is chosen by the user, and should be handled carefully. An attacker could write some SQL there, and create the following query: > SELECT brand, name, price FROM tools WHERE type = \"hammer AND SELECT password FROM passwords\" [Computerphile has a nice video explaining it]( URL_0 ) and also [an actual example]( URL_1 ). In a similar way, attackers can also inject scripts into HTML pages. If you rightclick on any webpage and select \"view page source\", you can find some < script > tags near the bottom indicating the beginning of a script. Scripts are very powerful, and serve a lot of purposes: animations, advertisement, data collection, ... . One place where script injection could be possible is in comments like these on Reddit. I'm typing this text, and Reddit pastes it into the web page. If I were an attacker and Reddit wasn't careful, your browser would interpret the < script > tag I used before as the start of a script, and start executing whatever follows. That's of course very dangerous, and Reddit needs to filter my comment before blindly pasting it into the page. I don't know what the Newegg exploit exactly is about, but it probably uses a variation of these. I'll look into it.",
"Everyone is explaining like you are 18, here's an explainlikeim5. Imagine you have a locked wooden box. A box full of information. Different sections of this box holds different data (this is your database). The box is wearing a disguise(webpage). This box understands a language (SQL). You can talk to the box using this. You can add/delete/edit/view the information in the box using this special language. The box can talk back to you and give you answers. It can change the content of itself depending on what you tell it to do. You talk to the box through different holes of its disguise. These holes let certain types of information in (text fields of the webpage). If the information you ask/input into these ports are of a certain criteria you are granted access to the information inside. Sometimes boxes aren't fully protected and let people say malicious instructions to the box. Sometimes the box allows this because it isn't setup in a way where it needs very specific instructions to work. Sometimes if you ask the box to do something when a certain condition is true, e.g. if 1 = 1 it will do it. 1 always equals 1. The box listens. You could tell the box to display sensitive data and/or delete it's valuable information. If a box is setup properly it's information will be hidden well and the holes will not let certain instructions through. It will only let in instructions it knows are safe"
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"https://www.youtube.com/watch?v=_jKylhJtPmI",
"https://www.youtube.com/watch?v=ciNHn38EyRc"
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|
9he98j | Wireless earphones disconnect when there is lightning | I was outside the gym waiting for my Uber when it was raining heavily and my earphones disconnects for a split second when there is lightning. What causes the disconnect? | Technology | explainlikeimfive | {
"a_id": [
"e6bmqt3"
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"text": [
"Lightning is a high-voltage electrical discharge, and your wireless earphones are basically miniaturized radio receivers; the lighting is far more powerful than the radio transmitter in your device, so the electromagnetic interference the lightning causes briefly overwhelms the radio signal from the transmitter."
],
"score": [
8
],
"text_urls": [
[]
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} | [
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"url"
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9herua | What in the world is RAID in Linux disk partitioning? | Technology | explainlikeimfive | {
"a_id": [
"e6b9e1r"
],
"text": [
"Redundant Array of Individual Drives Basically the same data is stored on 2 or more (redundant) drives, in case one fails the system keeps running, and you replace the failed drive"
],
"score": [
5
],
"text_urls": [
[]
]
} | [
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|
9hgga7 | Before a computer has code and input, how does somebody create the program to write the source code? | Technology | explainlikeimfive | {
"a_id": [
"e6bohqe",
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"e6bowqn"
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"text": [
"Today, you just use another computer for it. Like, you use your laptop to program an arduino, which is a tiny computer. The first computers had fixed programming and were programmed by physically changing the internal wiring. We're talking about room sized behemoths there. Later, you had input devices like switches on panels, and punched cards.",
"The first computers used mechanical systems ([Wikipedia]( URL_0 )). These used paper with holes in it (punch cards). The \"thinking\" is entirely done by mechanical levers and triggers, and the program is defined by the sequence of holes. Nowadays at the lowest levels, semiconductors are used to create transistors. These indicate the binary 1's and 0's on which all further programming levels are based.",
"The first real \"programs\" were built into the computer. Back then, a computer was purpose-built to do one thing and one thing only. If you wanted to reprogram it, you had to take it apart and rewire it. Later, someone had the bright idea to control the wires with data. This lead to the [Manchester Baby]( URL_0 ), the world's first stored-program computer. Programming it consisted of manually entering the programs using buttons and switches on the front. Later computers used punch cards for programming. You'd write a program by punching out holes in the card that corresponded to the binary code, and then feed the stack of cards into the machine. It wasn't until much later that you would write computer programs on other computers. By then, it was easy to use the current generation computer to write the software for the next generation."
],
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"https://en.wikipedia.org/wiki/Computer#First_computing_device"
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|
9hh6cx | How can smart electricity meters send the readings to the energy supplier without any SIM card or Wi-Fi access? | Technology | explainlikeimfive | {
"a_id": [
"e6bujy6",
"e6bugdn"
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"text": [
"There are many options, but you also need to consider that there are \"wires\" from the meter to the energy supplier. Not everything needs to use the phone network.",
"In the UK smart meters have a multi network, e-sim which when the unit is being installed, the installer uses the ‘installer’ menu to search for the strongest signal, then registers on the network using that sim."
],
"score": [
3,
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|
9hh6uc | How does my freezer know when to dump ice? | I always hear it drop ice, and refill with water. How does it not dump water into my ice box? | Technology | explainlikeimfive | {
"a_id": [
"e6bv7vs"
],
"text": [
"A tiny thermostat that touches the ice. Water fills in the cube tray and when the thermostat reads well below freezing it signals the motor to cycle and dump the ice."
],
"score": [
3
],
"text_urls": [
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9hhzwi | When you turn the volume all the way down on an electrical device, does it still make the sound? | For example, if you turn the volume down on your cell phone, does the device still make that sound but with no volume, or does it know not to even bother wasting resources thinking about it. | Technology | explainlikeimfive | {
"a_id": [
"e6c3aj0",
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"text": [
"On an oldschool electric device - like a walkman tape player - the sound is still produced, but the signal gets killed before it makes it to the headphone jack. For things with an operating system and software, like a phone, it depends on what you mean by \"make a sound,\" and it depends on the app being used. The app is aware of what the audio volume is set to. If the person who wrote the app was clever, they could do a check to see if the volume is set to \"mute,\" and if so, stop any part of the program which makes sound. This would save on memory and processor usage! However, there is no requirement to do so - the program is allowed to keep on sending music or game audio to the OS, saying \"please play this sound!\" The OS will simply ignore it if the system is on mute. I'm not sure if that counts as \"making the sound\" for your purposes.",
"A device with a physical volume knob, specifically a *potentiometer* based control, operates the same even if the knob is at zero. The knob adjusts a resistance which reduces signal by a variable amount, even down to zero. This type of control was common on early digital devices like CD players, and is still common on amplifiers or standalone speakers which accept (but are not sources of) audio. With something like a cell phone or computer, it would depend on the software. Windows vs. Mac and iOS vs. Android could handle this differently, and I don't know how each one works. But I do know if somebody provides an answer (i.e. current phones do continue playback, they just reduce the volume to zero) that would be subject to change as future devices (or even software updates) come along."
],
"score": [
30,
11
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"text_urls": [
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} | [
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9hjfnh | Why do pens behave this way when running out of ink? | Technology | explainlikeimfive | {
"a_id": [
"e6cfcdt"
],
"text": [
"The ball in the ball-point pen needs to roll to transfer the ink inside the pen to \"paint\" the outside surface. However, that ball can get jammed sometimes, possibly due to small particles flaking off the paper or solids/bubbles in the ink. In addition, when a pen runs low on ink, there is less ink \"pushing down\" to help transfer ink. A jammed ball-point can't transfer ink so your strokes end up blank as if it ran out ink. Starting your stroke on a new portion of paper gives enough grip to unjam the ball-point so that it writes again. Now, why does going over the same strokes not work? With your original stroke, the jammed ball-point smoothed the paper under it like a rolling pin. The smoothed paper doesn't have enough roughness to make the ball-point roll again. It slides instead of rolls so no ink transfers."
],
"score": [
6
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} | [
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|
9hm5px | How does a thumbprint sensor on a mobile device work, and why does it have to be recalibrated every once in a while? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Most fingerprint scanner are made of capacitive touch sensors, just like the ones on most touch screens. The simple explanation is that it's a bunch of capacitors, which are devices that can store small amounts of electrical charge. The capacitors are tiny, smaller than the ridge of a fingerprint. When you touch a capacitor, at least one this small, it changes how well the capacitor can hold a charge. Since a ridge on your finger makes direct contact it changes how much charge the capacitor can hold more than a valley on your fingerprint, which has a layer of air between it and your skin. The sensor then basically measures the difference in voltages across all of the sensors, and can tell which capacitors are in contact with your skin (ridges) and which have the layer of air between them (the valleys). It can use this to then construct a kind of image of what your fingerprint looks like. What it does with that image probably depends on the phone. Usually they look for significant features like where ridges and valleys intersect and tries to find matches for those, as opposed to making sure every ridge and every valley lines up with what it has stored since that would be computationally more work and also more prone to problems. Why do you have to recalibrate it? Well that depends on a lot of things. I've never had to recalibrate mine, but it could just be the equipment stops working properly, maybe the sensor is dirty, but you shouldn't have to redo it normally if everything works as intended."
],
"score": [
10
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|
9hmlpt | the difference between .com and .net, and why there are so many more .com websites than .net | Technology | explainlikeimfive | {
"a_id": [
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".com and .net are two of the original endings for Domains along with .org and .gov and .edu and .mil. In the beginning those endings all had their own specific purpose and some retain those even today. \".gov\" is limited to US government institutions, \".edu\" is for educational institution and \".mil\" is for the Us military. com, net and org originally were supposed to be similarly specific with .net for organizations having to do with networking and .org was supposed to be for non-profits while .com was for \"commercial\" i.e. for profit organizations. Those rules didn't last very long and .com, .org and .net became simple generic domain endings that everyone can use for any purpose. In some country-specific top level domains like .uk or .jp that original us setup gets mirrored in the 2nd level. So you have the equivalent of a .com ending in the . URL_1 ending in Japan and . URL_0 for uk government sites and so on.",
".com stands for commercial, for any business. .net is for a network entity, mostly businesses, but specialized ones (e.g. ISPs). So there are many more of the former than the latter. That's not enforced when registering a domain name, but most people choose .com, since that's what most people are used to seeing and typing. So if you want to find example corp, you'd be more likely to type URL_0 than URL_1 .",
"The reason that .com domains are more prominent is that when the web first started getting popular in the mid to late 90s, the first big websites had all been started when people still stuck to the convention of using .com for commercial websites. So people associated .com as being the only legitimate level domain if you want a popular website. .net domains were kind of second-tier. They even called the era the “dot com boom.”"
],
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6,
5
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[
"gov.uk",
"co.jp"
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"example.com",
"example.net"
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|
9hn0j8 | Why can cars get towed so easily? Don't parking brakes and steering wheel locks stop that kind of thing? | I always see video of cars just getting towed away, but doesn't that cause some sort of damage to the car? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"For the last half, there’s ways around things like that. Did a tow-away of an abandoned car.. front wheel drive but parking brake was on and didn’t have the keys. So I got into the car using my regular lockout tools, alarm went off but simply popped the hood and disconnected the battery then took the brake off and away I went. But mainly tow truck operators can lift the drive wheels off the ground with our wheel underlifts as usual and go. That’s with either the method I above, getting lucky and the brake already off, or we’re picking up a rear wheel drive car from the rear. If the steering is locked up sideways for example, and this also applies to 4x4/awd vehicles, either end can be picked up, then the remaining end put on dollies(those twin sets of 2 wheels you generally see on either side of a tow truck). TL;DR If time is a factor, either end of the vehicle can be picked up with the wheel underlift, and the opposite end put on dollies if that’s the case. That said, in some cases I would imagine the hardcore repo folk or those working in a rough neighbourhood for example.. the aim of the game is to just get the car away from its location safely and with minimal(if any) confrontation with the vehicle owner. Minor damage getting it from where it’s parked, to some side street out of sight in order to do the ideas listed above for example.. may be irrelevant but of course that’s circumstantial and/or at the discretion of the truck driver.",
"The main way you can really damage a car is by towing a 4x4 incorrectly - the transfer gearboxes really don't like it and will turn into scrap very very quickly.",
"Generally tow truck drivers know if a car is front or rear wheel drive, and will try and pick it up accordingly. Obviously there are some drivers who don't care and will pick up from whatever direction is easiest. In a front wheel drive car, when the car is in park, a little arm in the transmission stops the gears and therefore the front wheels from spinning. Opposite for rear wheel drive. So drivers will pick up whichever is the drive wheel. I think hand brake is generally on the rear wheels. In theory, a driver is supposed to use [go-jacks]( URL_1 ) to pull a car out of a parking spot and into the lane to get more room to put the [dollies]( URL_0 ) if necessary, or to hook up the correct side. Tow truck drivers for impound yards often don't care, and will do whatever is easiest for them."
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"https://www.truckntow.com/original-in-the-ditch-self-loading-speed-dollies-with-steel-wheels-1.html?prod_id=7631&utm_source=google_shopping&utm_medium=cse&utm_term=7631&gclid=Cj0KCQjwrZLdBRCmARIsAFBZllEWGU-ynPAqtkn4UOu7iNBWExBlGXOWP-4SrcGZy1b_jWtrUOa1BhwaAiNnEALw_wcB",
"https://www.amazon.com/Go-Jak-SuperSlick-Vehicles-500lbs-Individually/dp/B00P00YLUA"
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9ho0y0 | Why is it that modern body armor, like the kind used by the military and police, is very rarely of high enough strength to stop rounds from rifle caliber weapons? Especially in a military context, aren't rifle caliber weapons exceedingly common? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"When I was deployed we had armor with plates. They were rated to stop a round from an AK-47. But like with many things. The more times it gets hit the more it loses its structural integrity. Think of a brick wall and a sledgehammer. Sure, the brick wall maybe able to stop a few hits, but eventually the force is going to weaken it to the point of failure. You also have to consider mobility as well. The armor can’t be so thick and heavy that the person wearing can’t move either. It’s a balance that has to be reached. Too much weight and the soldiers may as well just make a Fox hole and fight from a secure position.",
"The speed of a rifle bullet is much more than a pistol. The amount of armor that would be required to stop a rifle bullet with the same effectiveness as a pistol round would be too heavy and bulky for the wearer to be able to do anything else effectively.",
"Disclaimer: I was in the navy almost 20 years ago, so I'm sure things have changed since. When I was on active duty, there were several ports er stopped in where our watch standers were required to wear flak jackets. We were told they were rated for frag and small-to-medium caliber pistol rounds--but not rifle bullets. When I got off watch the first time, I hit the publications to find out why. As it turns out, since WWII, upwards of 80% of casualties suffered by soldiers in combat were inflicted by fragments from explosive detonation, not bullets (frag grenades, land mines, artillery shells). At the same time, nearly all modern militaries practice a type of warfare called \"fire and maneuver.\" Well over 95% of bullets fired are never even intended to hit their target; they're used primarily to force the enemy to stay behind cover (called \"suppressive fire\") while the rest of the squad maneuvers into position for the kill. I understand that nowadays, soldiers' armor is issued with trauma plates, so clearly things have changed a bit."
],
"score": [
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5,
4
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|
9hpm0b | How does the anti-shoplifting system in a supermarket work? | Technology | explainlikeimfive | {
"a_id": [
"e6dn6df"
],
"text": [
"It’s these stuck on thing that have a slight magnetic field to them the get activated when you walk through the thing that beep."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
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|
9hqo9o | Differences between HTTP, HTTPS and HTTP2 | Technology | explainlikeimfive | {
"a_id": [
"e6drqxj",
"e6eejr0"
],
"text": [
"HTTP: Me: Hey google, are you there? Google: Yup. Me: What is “up dog”? Google: Nothing much. Me: Hey google, are you still there? Google: Yup. Me: What is “...”? Google: ... Me: Hey google, are you still there? Google: yup. Me: ... Google: ... ... HTTP2: Me: Hey google, are you there? Google: Yup. Me: What is “up dog”? Google: Nothing much. Me: What is “...”? Google: ... Me: ... Google: ... (I only ask “Hey google, are you there?” one time) HTTPS: The same kind of conversations occur, but me and google use the decoder rings we found in our cereal boxes so we can talk in code and no one else knows what we’re saying.",
"HTTP is... well, HTTP, your basic GET, POST, etc HTTPS the same protocol as HTTP but everything happens over encrypted secure connection. HTTP/2 adds ability to send multiple resources (pages,images,scripts,etc) over the same connection at the same time in parallel. It also allows server to push you resources that you didn't ask for, but it thinks you'll need."
],
"score": [
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|
9hsotg | Public Key Cryptography | So I was looking in r/personalfinance where it was posted that it is free to freeze your credit now. Someone made a comment that you wouldn't have to freeze your credit if you could verify your identity using Public Key Cryptography rather than just presenting simple identification numbers like SSN and facts about yourself like your birthday. To me, the best I know of verifying your identity is two factor identification (3?). My username, my password, my phone - must be me! How does Public Key Cryptography work and how might we implement it to secure our finances? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"The analogy is to imagine a special lock with 2 keys. Either key can lock the lock, but if you lock it with Key A, you need to use Key B to unlock it, and vice versa. You keep Key A to yourself, and give Key B to everyone you know. They all have their own locks like this, and they all give out their Key B to everyone. So I put a message in a box, and lock it with my lock and Key A, and use YOUR lock and Key B as well. Now anyone with my Key B can prove I locked the lock (by unlocking my lock), and you can open the lock to see my message with your Key A. My lock \"signs\" the message as being from me exclusively, and yours secures the message as being for you alone. The same thing happens with public-key cryptography. A message is encrypted with a function that has one key, and decrypted with the other. So if you encrypt it twice, once with my public key, once with your private one, only I can decrypt it, and I know it had to be from you exclusively. There are a number of uses beyond sending messages - one could use it to secure buy/sell orders to a brokerage, to prove that a request for credit is actually from a particular person, etc."
],
"score": [
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"text_urls": [
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} | [
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9hsu0y | Why do computer speakers emit staticky, Geiger counter-like sounds when you place a cell phone near them that's transmitting or receiving data? | Technology | explainlikeimfive | {
"a_id": [
"e6e8w5n"
],
"text": [
"phones use waves that are in the electromagnetic spectrum, your speakers use electromagnets to operate and produce sound. so when your phone transmits it interrupts the electromagnets in your speakers and activates them, making the sound you hear. your speakers think they are getting a signal to play, but the signal is just part of the phone's transmission that got picked up by the wires in your speaker who function like an antenna in this case. they will respond to anything that makes or interacts with a magnetic field. in turn, magnetic fields also interfere with your phone, a powerfull magnetic field will kill your signal."
],
"score": [
5
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"text_urls": [
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|
9htyd6 | How is electricity turned into a mechanical action? | I don't quite understand how, or at what point, that electricity makes something move in a motor. For example, making a robot's arm move up and down, how does electricity force a piece of metal to perform that action and put in force against gravity? If someone could explain this, it would be greatly appreciated! :) | Technology | explainlikeimfive | {
"a_id": [
"e6eh9ek"
],
"text": [
"Electrical current induces a magnetic field. If a ferrous metal is in that field a force will be exerted on it. I.e. place a ferrous core in a coil of current carrying wire and the core will experience the force and thus move the \"robots arm\""
],
"score": [
4
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9hu59l | Why do electric cars (except Tesla) have such a strange design compared with gasoline driven cars? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Part of it is practical, part of it is aesthetic. Electric cars don't require an engine bay like internal combustion cars do, so you don't need much front on them. Thus they can be designed prioritize other things like passenger space, weight, or aerodynamics without having that big piece sticking out. The other reason is that early adopters of modern EVs and hybrids tended to be environmentalists, who wanted the car to look different in order to make a statement. These cars tended to have a \"softer\" and \"friendlier\" design aesthetic to reflect their environmentally conscious philosophy, but that didn't resonate with the car buying public. Most people have in their head what a car \"should\" look like. Western audiences tend to prefer more \"aggressive\" styling. Take a look at the Nissan Leaf for example. Same car, but two completely different design philosophies between the 1st and 2nd generations.",
"Its because they dont actually want you to buy one. Their profit margins are much, much smaller on EVs than on internal combustion engine cars simply because its a newer technology. The Chevy Bolt, for example, is simply a car built to earn enough CARB credits to satisfy regulators. It is never advertised, and very few are actually built. Many dealers dont actually even have any in stock. Think about it, when is the last time you saw a commercial for an EV? Most commercials are for trucks, because the profit margin on trucks is higher than any other class of car. I think Tesla has somewhat forced their hand in a way, and now we are seeing normal looking EVs being announced because they are now losing sales. The Jaguar i-PACE, MB EQC, and Audi e-tron, and Porsche Taycan are all coming out soon and look like normal cars."
],
"score": [
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5
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|
9husep | How does encryption work and what makes it safe? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Encryption is about taking data, scrambling it up so no one else can read it, then unscrambling it at the other end For symmetric encryption we both have the same key. If your data is this [big Rubiks cube in a solved form]( URL_0 ) then the encryption key would be the instructions on how you scrambled it up. Since I also have the key I can just reverse the turns you made to get the original message back out, but someone without the key will spend quite a while trying to solve that rubiks cube. This also works for stuff you want to restrict to just yourself. If you encrypt your hard drive then the password you enter will be used to get the key that was used to encrypt the hard drive. The computer will then use that key to descramble the rubiks cube(hard drive) in real time as you need files off of it. If someone steals your computer or hard drive and doesn't have the password then all they have is a scrambled rubiks cube which will take them months to solve."
],
"score": [
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"text_urls": [
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|
9hvzg9 | How do movies make such realistic-looking fictional characters? | I'm talking about the likes of [Thanos]( URL_0 ) from Infinity War; these characters look so incredibly detailed and their movements and voicing so natural, that it's almost hard to imagine how they were made. Are they simply modelled in extremely detailed 3D? Are they computer-edited scenes of real people in heavy makeup? Why are video games so behind on character movements and face animations compared to these movie characters? | Technology | explainlikeimfive | {
"a_id": [
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"Videogames have the disadvantage of needing to be rendered in real-time. When you push a button you expect a response immediately, not *after* the hardware has made a ton of passes on lighting and shadows and all that. With a movie, time is on their side to render everything as it doesn't need to be 60 frames, on your screen, this very instant, and the hardware can do more work to make it more realistic even if it takes 60 seconds per frame rather than 60 frames per second to render. Also they generally (or at least used to) use whole farms of computers to do things like Pixar movies and other Full CG stuff. A single PlayStation 2 could do some impressive stuff for its time, but you would need tons of PS2s somehow all networked together to be able to work together to render something like Final Fantasy: The Spirits Within, which IIRC came out during the PS2's lifecycle.",
"In movies you use motion and face capture of real actors most of the time so you can create another face using there movement and voice. You can look hot they are captured URL_0 That in combination with a large special effect team that can look at the face and change how it move compared to a human face. So you need to preform all possible moment with a actor and find a way to stitch them together as you can constantly look at a character in a game but a movie will cut to another scene. So you could do a full motion but you would need to do more then in a move as the number of possible motion is a game is large compare to a simple fix script in a move. Doing it for a film is expensive but game would be more complex and you would need to do that for all characters. So it would be expensive. Another problem is the uncanny valley. look at URL_2 and notice that the human face look ok but the alien look good. The problem is that we know how human looks so we can see any imperfection. So a almost perfect human look worse then bad human imitation. The bad imitation is obvious not a human so we accept it. But the almost human face is intreprited as a human but there is somting wrong with them. So we like the bad face better A example is the Recreated Grand Moff Tarkin and princess Leia from Rogue One URL_1 Ships, androids and aliens look good but the human does not. So it is extremely hard to create good human faces that is what is common in games."
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9i1e8q | How do long exposure cameras work? More specifically, how do they layer the important parts of many images to make something look amazing? | Technology | explainlikeimfive | {
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"Long exposure is a technique for photography in dark places. The shutter remains open for longer, allowing the camera to pick up on more light waves from smaller light sources. I am less sure of how this has changed with digital photography, but with traditional, it gives the film more time to register light sources/reflections and burn their impression onto the film. Cameras perceive presence and absence of light, not importance of subject. Even digital cameras do long exposure by holding the shutter open and putting what happens on the other side into one image; layering isn’t going to do shit if it doesn’t have enough time to detect subtle light sources. This also means the camera has to be absolutely still — the longer the shutter is open, the more movement it also captures. You need some kind of camera stand and something to control the shutter from a distance because trying to do it with your hands, even just pushing a button, is going to make the camera wobble and the light sources will blur. A five minute exposure of the night sky will give you a really beautiful shot of the Milky Way. It will also show you the trail of any lit airplane that crossed the sky in those five minutes. If a car flashes its lights at the camera lens, the entire image will be ruined because no amount of restored darkness is going to un-flash the exposure."
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9i3q34 | Lag between two TVs in the same room on the same channel. | Technology | explainlikeimfive | {
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"It totally depends on what is feeding the TV and what settings the TV has. Modern TVs have lots of extra processing that can enhance the viewing experience, but that processing takes time. That's not a problem since everything is delayed the same amount (audio and video) so everything is in sync. However two TVs next to each other with different processing turned on might be slightly out of sync with each other. The more likely culprit is the use of satellite receivers. Each TV has it's own receiver and each receiver gets its signal from one or more dishes. However they each buffer their signal based on reception quality and each receiver may choose to buffer more or less data than another receiver. So now you can get two TVs that are identical, showing the same show but with multi-second delays."
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9i4494 | How did computers store dates that led to the Y2K problem | The usual explanation I've heard is that they only stored 2 digits to save space and this would lead to problems, but if you had stored them as characters that would be 1 byte per character and if you stored year as a single byte you'd have 256 years to worry about rollover. Did they try to pack both digits into 1 byte? 3 bits you get you 0-7 so to pack 0-10 you'd need 4 bits, so you'd either save zero or maybe 1 bit doing it that way. & #x200B; How were years stored in a way that saved space? | Technology | explainlikeimfive | {
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"The issue was a bit higher level than data types and storage and had to do with interpretation of date values. The whole \"2 digit years save space\" thing wasn't really that much of a thing. Most dates were stored in an epoch format - an integer representing the number of seconds that had elapsed since a predefined date (usually 1/1/1970 12:00AM) - so date values were the size of integers, programmatically speaking. However, dates were also sometimes stored as text, and/or program logic would calculate date differences or additions based on years being in the 20th century. Consequently, when a 2-digit year rolled over to \"00\", the question/concern would be that it would be calculated as 1900 and not 2000. Luckily, the problem turned out to be not as extensive as was feared. That being said, Y2K-related projects built me a nice house, so it was incredibly necessary those projects happened to make absolutely sure. ;)"
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9i48uw | Why did soldiers in the 18th century stand infront of each other, taking turns shooting at each other? | Technology | explainlikeimfive | {
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"Black powder muskets. The average infantry musket of the 18th century had a maximum effective range against a man-sized target of 50-75 yards. Maybe 125 yards against a large group of men. A very well trained soldier, in perfect conditions, could fire 3 shots a minute. Every shot produced a large cloud of thick smoke and a very loud noise. So in battle, your average trooper was completely ineffective alone. He couldn't fire fast enough, or hit reliably enough, to protect himself. And after 2 or 3 shots he'd be basically deaf and blind. If someone on a horse took interest in him he was dead meat. So, big groups of soldiers was the answer. A group of men can lay down a barrage of fire that may actually score a significant number of hits. When firing in ranks they can keep up a steady stream of gunfire, and when attacked at close range they can form an effective defense with massed bayonets. Close together, they can also stay organized. It's easy to stick with a tight group (especially when everyone is wearing bright uniforms that are easy to see, and waving big flags). TL;DR: * Alone musket dude: Totally screwed. * Big group of musket dudes: Effective fighting force.",
"They used firing line to maximize firepower. Back then they used muskets which took about a minute to reload so by setting up three lines they could fire every twenty seconds."
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9i5bqz | How does Captcha protect against bots? | Technology | explainlikeimfive | {
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"Recognizing patterns and shapes is an evolutionary trait that is strongly ingrained in human beings. It's one of the biggest reasons that we were able to become the dominate species on the planet. It's how we learned the seasons, and gained the ability to plan for an agricultural existence. It's also why we're prone to seeing conspiracies, or shapes in the stars, or a ton of other \"phenomena\". This means that we're a whole hell of a lot better at making out shapes than even the best AI could try to be. So you can chicken scratch some letters out, and a human being will be able to make it out while a computer will fail."
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9i5o5z | Why does touching the arc of my "plasma" lighter to a piece of metal turn off my computer monitors? | Technology | explainlikeimfive | {
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"EMP means \"electromagnetic pulse\". It is important to understand a phenomenon called \"induction\" in order to understand what an EMP does (and also it is important to understand most anything about electric devices in the modern world). When electricity flows through a conductor it forms a magnetic field around it, and when a conductor moves through a magnetic field it produces an electric current in the conductor. This is called \"induction\", where the magnetic field \"induces\" a current flow and vice versa as they are both aspects of the electromagnetic field. Plasma is a state of matter where the atoms are so energized that their negatively charged electrons are free to move about without being locked to the positively charged nuclei. Plasma therefore involves the movement of highly charged particles and therefore can produce strong magnetic fields. The quick movement of the the plasma can shake the fundamental electromagnetic field and form a pulse of magnetism that causes current in conductors. Many electronics, especially computers, contain delicate components which rely on subtle electric currents to perform their jobs. While protected behind resistors from excessive power from the wall or batteries, inducing a current in them out of thin air such as with a strong electromagnetic pulse can cause them to malfunction or even destroy such components. A relatively weak pulse such as with the lighter can perhaps make a monitor shut down temporarily, but very strong pulses can permanently destroy electronics which are not shielded against such damage.",
"So this lighter uses electric arc to light smokes? Literally inhaling straight off a ozone generator with a straw. I'd rather inhale butane than ozone. URL_0 URL_1"
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"https://en.wikipedia.org/wiki/Spark_gap#Health_hazards",
"https://www.epa.gov/indoor-air-quality-iaq/ozone-generators-are-sold-air-cleaners"
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9i5oto | How does the stealth technology work on stealth aircraft? How ‘invisible’ are these aircraft to sensors? Some examples being the B-2 Spirit, and F-117 Nighthawk. | Technology | explainlikeimfive | {
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"The stealth technology at present has two components. There is a coating of radar absorbing material (RAM) that prevents bounce back. This is the primary protection for the B2. There is also radar redirection by using finely angled surfaces to prevent a direct bounce back to the site. This is the primary protection for the F117. Both will be defeated if the range to the source is low enough. Additionally, tactics have evolved specifically to defeat these airframes, such as using airborne radars to beam and ground receivers to look for \"blank spots\".",
"Stealth aircraft often have the specifics of their technology kept secret as they provide strategic military advantages, so you are unlikely to get extremely precise information about such things. However the general idea is that such aircraft will either absorb or divert incoming radar waves so they cannot be detected by the radar receiver. In particular the F-117 uses its distinctive angular surfaces to direct radar waves up and away from aircraft or ground stations attempting to detect it. They also use secret materials which absorb radar waves to some extent. Quite how difficult they are to detect is difficult to determine but I have heard that such aircraft provide less radar return than a small bird.",
"One misunderstanding about stealth is that it either makes something \"invisible\" to radar or it doesn't...the point of stealth or Low Observability (LO) is to reduce the radius of detection. The entire point of stealth is to enable an aircraft to deliver weapons from ranges where the enemy can't detect them and threaten them Example A F-15 at 30,000 feet in the air can be detected by Radar X at 120 miles away A F-35 at 30,000 feet in the air can be detected by Radar X at 40 miles away So our F-15 is carrying weapons that can be launched against Radar X from only 80 miles away - thus the F-15 has to travel 40 miles inside the detection range, release weapons, then leave the engagement radius...so it's vulnerable to detection and attack for a while Our F-35 is carrying the same weapons, 80 mile engagement range, so it can get closer to the target, release weapons - which increases it's observability for a moment, then starts to evade, observability decreases again and it escapes with a much shorter time for Radar X to detect, classify and target the F-35",
"F-117A flew approx 2% of all sorties in the gulf war but accounted for some ridiculous amount of strategic targets destroyed (in excess of 20% I think) thanks to it’s goddamned near invisibility vs opposing tech of its day. Source: Am 35 but wrote a 20 page paper on military aircraft of the 20th century senior year of high school. Feel free to completely refute my claims. Edit: “near” not “bear”"
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9id3cz | Why does windows instantly verify a correct password on startup but take a few moments when my attempt was incorrect. | Technology | explainlikeimfive | {
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"To stop brute force cracking attempts. It doesn't inconvenience you to pause a moment, but totally invalidates tool-based attacks.",
"You let correct logins in because nobody wants to wait. You add a delay to incorrect ones so that people can brute force passwords and try to break into the system",
"When other answers use the term \"brute force\" they're referring to an attack by software that blindly tries every single combination of letters possible - one combination per attempt. I.e., it tries \"AAAAA\", then \"AAAAB\", \"AAAAC\", \"AAAAD\", and so on, though all the colossal number of possibilities, expecting to eventually hit on your password and gain entry into your account. There's no intelligence used to first try the most likely password (like \"password\", or \"Password123\"). That's why it's called a \"brute force\" method. It will take many thousands of attempts before the software stumbles across the combination of characters that you have in your password. If the computer that's under attack responds quickly to a failed password, this kind of attack may take only a few minutes or a couple of hours to find your password. That's a short enough time that no one may notice the attack. If the computer responds slowly, it will take days or weeks to try so many combinations, making this kind of attack more likely to be detected and less attractive to attackers."
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9idc64 | How did people sync their clocks / know what time it was (say, 1875) when things like catching a train required you to know the exact time? | Technology | explainlikeimfive | {
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"People would just plan to arrive early enough at the train station, synchronize with the grand central clock, then run some errands, patronize the numerous cafés, bars and restaurants on the other side of the street ... Actually not that different from us, we may know exactly when a plane will take off, but not exactly how much time we need to go through check-in and security, so we arrive early at the airport. The real issue was synchronizing clocks between stations and be able to know when a train will arrive. A lot of people came with many ideas to solve this increasingly crucial issue at the beginning of the 20th century. A guy working at the Bern patent office reviewed a lot of those and, probably out of boredom, end up proving that this is not possible ! (just speaking of the most general case, of course). His name was Albert Einstein.",
"You don't need to know the exact time to catch a train. You can miss a train by being late, but not by being early. The less sure you are about the time, the earlier you show up just to be safe. In a world of slow communication, there is little need to ordinary people to have synchronized clocks (navigation being an exception). If it takes 2 hours to walk to grandma's house, what difference does it make if our clocks are 15 minutes apart? When you have faster communication, it increases the need to have synchronized clocks, but it also provides the means for doing so.",
"Back then most people will have some king of time piece, towns and cities would normally have a central clock tower Or church. And from here trains/ telegram system. I would guess futher on the fringe, people would use high noon.",
"Since navagation at sea required accurate chronometers to determine longitude, a common method was a time ball. Situated on the heights above the harbor, it would rise soon before a set time (usually noon or 1pm), then drop precisely at the hour.",
"Time zones as we know them now didn't exist until the late 1800's. Before that each town was basically it's own time zone and the town clock was set according to when noon was in town, which was when the sun was highest in the sky. At that point even if you didn't know the exact time you could see where the sun was and have a good guess."
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9ii4vu | What is registered RAM and what is the difference to ECC RAM and regular desktop RAM | Are there any advantages I can have (if used in a regular gaming rig/office pc) or is it just any other ram but with a special treat? | Technology | explainlikeimfive | {
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"ECC RAM has Error Correcting Codes that it transmits along with the data. This let's it fix minor data corruption and spot major data corruption. This is useful for a mission critical system that will be running for months or years with no opportunity to reset Registered memory puts a set of registers (hence the name) between the RAM and the CPUs memory controller reducing the load. This let's the sticks be much higher density without overloading the memory controller. Unregistered DRAM tops out at 16 GB per stick today, registered DRAM can get up to 128 GB per stick. If you need obscene amounts of memory and don't care about the cost, registered memory is for you! Most consumer applications are price sensitive, non-critical applications that can tolerate the occasional memory error. For these, basic DRAM is the right choice. A gaming PC with registered ECC memory will just be reallllyyyyy expensive",
"ECC stands for Error Correcting Code. The RAM has extra bits in memory that it uses to compare what's being written to it, and make corrections if they don't match up. It's a little more complex than that and you can read about different methods on Wikipedia, but this is the gist of what it does. Error correcting is not important to home users, which is why it's almost never seen in desktops or laptops. For systems crunching a lot of data that needs to be accurate, like bank servers or scientific equipment. Registered (aka buffered) memory does a different task. It places an area of ultra fast memory between the system's CPU memory controller and the RAM itself. It takes some of the load off the memory controller. Generally this isn't an issue with desktops and laptops which usually support two or for sticks of RAM max. The controller isn't going to get bogged down. In servers with lots of ram modules, it can help maintain system stability."
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9ii6re | How can a speaker replicate such a wide variety of musical instruments and vocal sounds? | Technology | explainlikeimfive | {
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"They essentially perform the opposite function of our eardrums. Sound waves in the air cause our eardrums to vibrate, and that vibration is sensed and interpreted as sound by our brain. Speakers are the opposite: an electrical signal causes the speaker cone to vibrate, which causes vibrations in the air.",
"Sounds are just vibrations that can be represented (and stored) mathematically with numbers. To make them naturally, you do need specific instruments and vocals, but once you store that information, the numbers, you can recreate the sound via something that can flexibly generate any sort of vibration you need. To be more detailed, each individual note and sound is a single wave that can be represented mathematically by a simple equation. You can make more complex sounds by combining the waves together, like you can literally add the different equations up to make the graph for the combined soundwave. It's also important to mention that simple microphones and speakers do the same exact process, but in reverse of each other. Mics turn sound energy into electrical energy, where the electric signal represents the physical sound wave. Speakers can then be driven by this electricity (though often amplified) to generate a fairly accurate recreation of the original sound. Basically you're catching the essence of a sound, what makes that sound physically, and recreating it rather than how that sound was originally generated.",
"Sound is a vibration in the air. More specifically, it's a variation in air pressure. Every sound you hear, whether it's a single note from one instrument or the sound of an entire orchestra, is just air bouncing between higher pressure and lower pressure. It has a single value at any point in time, and if we had an instant-read barometer we could see it with our own eyes. When we record sound, we capture this varying pressure over time and store it somewhere. A microphone physically captures the air movement--think of it like a tiny sail being pushed back and forth--and converts it into something we can write somewhere. In the early days, we connected that sail to a needle that carved a groove into wax, like a seismograph. We can then reverse this process: take a needle and have it follow the groove, and push a speaker cone to recreate the vibration in the air. Nowadays we do this all electronically but the idea is exactly the same. So how can one value of pressure-over-time cause so many different sounds? That's because multiple sound waves add together. From a quick Google search: URL_0 Why instruments sound the way they do is a massive topic that I won't get into, but just know that two different instruments playing the same pitch sound different because their sounds are made up of different sets of waves added together. A violin playing 500Hz and a clarinet playing 500Hz both make a wave at 500Hz, but then the clarinet has a lot of 1500Hz, 2500Hz, etc. all added in, and a different set for the violin. Your brain doesn't hear all of the different frequencies separately, it collapses them all down into a single sound that we call \"the sound of a clarinet\". What's cool is that your brain has a really powerful audio processor built in, that can separate out all of the waves, group them together into instruments/voices, and allow you to pick out each sound. This is why you can understand someone talking even in a loud room with a lot of other conversations going on. Computers are still absolutely terrible at this."
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9ijm5b | What is happening when my phone displays that it has full 4G signal, but it clearly doesn't because it can't load anything? | Problem with the phone? Problem with the network? | Technology | explainlikeimfive | {
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"So how can you have 4G? Because your phone sends a message to the tower and says, \"Hey, I can talk in 4G, can you?\" And the tower goes ,\"Yes.\" Then the cellphone times how long that response took to come and measures how strong that signal is, and gives you some value that represents signal strength. What this doesn't tell you is, \"Hey tower, are you busy?\" And the tower responding, \"I'm up to my antenna in Instagram and porn, you're gonna have to wait.\" There is no measure of congestion. So you can speak the protocol, and the signal strength is good, but the tower can be servicing a lot of customers, say, if you're at a convention, or the tower's connection to the service provider could be far away, or limited in bandwidth, or shared and congested... And while signal strength could be good, there could be a lot of noise, resulting in a lot of lost and thus retransmitted communication. And it doesn't matter how many antennas are in your area. You see a tower with a shitload of white rectangles on it, so what? Don't forget that there is one and only one electromagnetic spectrum, that all cellphones of all makes share a very narrow slice of that, and all those cellphones all have to share - given some frequency spectrum, only one participant can be transmitting at a time. So if you think about it, the cellphone radio in your phone, right now, is picking up all communication from all other cellphones and the towers within range - it's just inspecting these packets and dropping them, \"Not for me...\" Same goes with WiFi/Bluetooth/cordless house phones (if they still exist)/baby monitors/microwaves - since they all use the same 2.4 GHz band. And none of these devices give a shit about each other - WiFi plays nice with other WiFi, but Bluetooth doesn't speak WiFi, and will just try to transmit over the \"noise\" in the background. Every single device within range that uses the same frequencies slows everyone down. And it doesn't matter if you're \"not on their network,\" because you're still on the same radio frequencies!",
"I think the best way to look at it is that signal =/= speed, but maximum speed. For example you have full signal and can have speeds UP to x, but because you're in the hills of nowhere the total speed you get is less than x.",
"Either/or/both/neither. There's an incredible amount of potential issues. 1. Signal strength might be good but quality is crap a la noise 2. Cell modem on your phone, drivers, operating system might be crapping out and/or struggling 3. If you say, hit your data cap for the month, your carrier may throttle you to super slow speeds. Some services might work okay but other, more media-rich pages or apps might not load fast at all 4. Carrier could be having problems on their end, either on the tower or something upstream 5. The backbone data network the carrier runs off of could be having problems 6. The specific service(s) you're using could be having issues And probably another dozen or two if I got creative."
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9ijqr6 | Why is it common for video game controllers to use abxy buttons instead of abcd or 1234? What's the origin of abxy? | Technology | explainlikeimfive | {
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"\"For the origins of the ABXY button scheme we must look back to the very beginning of additional buttons. When the Famicom (known as the Nintendo Entertainment System outside Japan) launched, it featured two primary buttons. While other companies labelled their (usually two) buttons with numbering such as 1 and 2 or I and II, Nintendo had instead used A and B. When the SNES was released in Japan in 1990 they added X and Y to the mix, and rotated it slightly. The format was now a diamond, with X, A, B, and Y all around, clockwise. This format became known as ABXY because of the obvious alphabetical order. But why X and Y? Why not C and D, the next most logical letters? The likely reason for this is future-proofing. Adding C and Z to the right of ABXY would not change the way games designed only for ABXY controlled, whereas if the controller had ABCD adding E and F and moving C up beside B would affect previous games, and having the buttons in ABECDF order would not make sense\" - URL_0",
"As a supplement to the other user's submission, it's also a fairly common practice in mathematics and programming to jump when using different axis. That explanation is a good one, and can also be thought of like this: a typical graph has an X- axis and a Y-axis, and if we populate the graph with data we might label those data as \"A\" or \"B\" or some other name. Making them \"Z\" and then something else isn't as helpful in compartmentalizing the information. So for a controller that started with \"A\" and \"B\", developers weren't sure exactly how many buttons we may eventually want or need (just as the other comment explains) and adding two more buttons to compliment the \"A\" and \"B\" buttons was seen like adding a new dimension to gameplay and not just new data points, so it is seen as more versatile. Again, it is helpful to think in pairs of triplets of variables, like A B and C, and X Y and Z, but not as helpful for us to try to remember 1 2 3 4 5 6 as six different data points and axis."
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9ijxxb | Some batteries can't be recharged while others can | Just bought some alkaline batteries and saw a label stating "Not rechargeable", but in my head I am thinking the battery has a charge already. Why shouldn't I recharge the battery? Surely a battery that comes in a fully charge state can be recharged? | Technology | explainlikeimfive | {
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"text": [
"Rechargeable batteries use a reversible chemical reaction to generate electricity, and are designed to be able to be recharged. Alkaline batteries (and other non-rechargeable types) use a chemical reactions that aren't meant to be reversible, and often have other differences to rechargeable batteries (e.g. higher voltage, longer operating life, cheaper to make).",
"Alkaline batteries *technically* can be recharged but they shouldn't be for safety reasons. Charging a battery with that chemistry creates gases and most consumer batteries aren't vented which means even if it doesn't explode, it'll very likely leak and ruin the charger or the device it's in. Implementing a vent system that wouldn't spill the contents while being used in any orientation wouldn't be practical when replacements are so cheap."
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9iknpt | How are ICBMs intercepted? | Technology | explainlikeimfive | {
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"text": [
"Generally, they're not. There are anti-ICBM technologies but generally speaking they are not super reliable, especially when you consider the potential damage a single nuclear-tipped missile could cause. There's a few different methods. Generally speaking it's best to hit them in the boost stage, when they're moving the slowest. By the time they're re-entering they're moving a lot faster, and modern ICBMs oftentimes have countermeasures or multiple warheads/re-entry vehicles. 1. Blow it up with another missile using explosives - might still be able to disable it if you don't directly hit it and just blow up near it, but if the ICBM has radioactive or biological components, you might spread that all over. Far, far better than hitting its target though. 2. Blow it up or disable it with a kinetic kill vehicle - basically hit it with a missile that doesn't have any explosives and destroy it with sheer kinetic energy. As you might imagine, it's pretty difficult and kind of like hitting a bullet with another bullet 3. Destroy or disable it with a laser - Lasers have relatively short range, require a large amount of power, and take some time to do their work. Large read that covers different types of systems both actual and in test, that operate at various stages of a missile's flight: URL_0",
"Seems difficult. You would have to shoot down the missile before it releases its payload. The ICBM doesn't just fly all the way to the target. It releases one or more vehicles containing the explosive - those are smaller and difficult to intercept. Luckily we have early warning radar which would give 15-30 minutes to launch a counter offensive, but I am not sure we could do it."
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"https://en.wikipedia.org/wiki/Missile_defense"
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9induu | What do computer scientists research in academia, as opposed to industry? | So I was just wondering this today after listening to a seminar from of my CS professor's about his AI research. The talk was fascinating and intelligent, but it also seemed like something that could easily be developed by a tech company for profit. Most professors of any type have a Ph.D. and they typically have teaching responsibilities, but how does their research differ from say, some of the AI research and development coming from Google? | Technology | explainlikeimfive | {
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"Most university researchers have research budgets because they wrote a research grant proposal to study something. They have papers to publish, and their research gives them things to write about, and their students topics to study. Most corporate research depends on the company's products. Product A needs feature B so there's someone doing research on \"can AI do B?\" Academic research is \"B might be possible with AI\".",
"A big part is trying to speed up or identify the ideal state of algorithms. For example, someone computer programs need to be run fast. Military programs that send rockets to destroy icbms need to identify the path of the rocket with minimal time so there are efforts to speed this up. A simplified example would be research on sorting a deck of cards. The way people often do by putting cards in order is called insertion sort and is not efficient if your deck of cards had 100000 cards. Insertion sort is take a card from the undort deck, and putting it where it belongs in the sorting deck. But the research may be looking for faster ways. They could try to come up with a quick way to sort things, even if you didn’t know how many cards and how many duplicates of each card there were in a deck of cards. This method is called quicksort and is efficient. Then, they could be interested if they have found an ideal sorting method. They could be trying to prove what the most efficient sorting method would be an compare to that. It turns out when sorting data that can be fit into buckets, quick sort isnideal. Quick sort is taking the first card in the deck, putting each card lower than it in one pile, and it an all the other cards in a second pile, and sorting those piles with the same technique until the whole deck is sorted. Doctorates in computer science are more focused on algorithms, efficiency, and speeding up processes. Doing so allows computers to run fast, implement this technology in a lot of ways, reduce battery usage. A more efficient algorithm on your phones operating system could allow it a longer battery life. A faster algorithm to improve satellite pictures could give the army better real time intel from drones. Solving complicated math problems such as the traveling salesman problem (p=np) could change the world as we know it. Figuring out a faster way for a computer to matrix multiplication could allow Google maps to find you a better route faster."
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9iq8vp | Why isn't anything being done about the massive amount of spam calls in America? | Technology | explainlikeimfive | {
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"text": [
"If caller ID is broken like jt is, it's not readily possible to associate a person behind an arbitrary phone number. Without substantial changes to the old telephone system, preventing spam calls becomes impossible.",
"Everyone makes money, so the only persons who want to to try to stop it are governments. These calls almost always come from overseas, and blocking all phone calls from a country is something that would cause problems between countries - so if those countries aren't serious about shutting down the operations (which are making lots of money in that country), there's not much that can be done."
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9iq8yv | Why is it so hard for machine translation to get English- > Russian right? | Technology | explainlikeimfive | {
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"Syntax varies from language to language , so it can be difficult for the AI to decipher what it is you're trying to say. For example: *\"My name is John\"*, in Irish is *\"John is ainm dom\"*, which literally translates to, *\"John is the name upon me\"*. So you can see with just that simple example, spread across a whole language, how difficult it must be to get it right.",
"Machine translations are based on a model that defines rules and language syntax for a given language. Essentially grammar rules you learn in school to speak English, such as a punctuation and order of words have to be implemented in that model. If the Russian model used was not programmed by a native speaker, assumptions may have been made leading to inaccurate translations. Most language rules aren't always hard and fast rules, so the generic model may fail to deal with certain exceptions in a language. Hence sometimes direct translations to languages like English to Russian aren't possible as it will offer a sequence of words not commonly used in russian. A more complex process would be needed to allow the translation to be culturally neutral. Most translation services allow you to provide better translations, if your proficient in the language to help improve it's own model. Natural speech data models can also be used to further enhance the reliability of the translation."
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9ithht | Not so long ago, everything chargeable needed an adapter; but these days almost everything is chargeable via USB. Why? | Technology | explainlikeimfive | {
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"text": [
"One contributing factor was that the European Union legislated that all phones must be chargeable via interchangeable USB plugs. When a lot of electronic gadgets were *forced* to have USB chargers, others followed because it was convenient for them too. Nearly every consumer has USB chargers in heir home already. Made for their locally used voltage level.",
"[You can thank the EU for that]( URL_1 ). They pushed for phone manufacturers to develop a common standard for all phones sold in the EU. It was a voluntary measure, but recently they've been considering [taking action to enforce it]( URL_0 )",
"USB stands for *universal* serial bus. It was designed in cooperation between many computer companies to be used for many different applications. Since it was present everywhere, it made sense for device manufacturers to make sure they were compatible with it."
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"https://www.reuters.com/article/us-eu-telecoms-charger/eu-regulators-to-study-need-for-action-on-common-mobile-phone-charger-idUSKBN1KR1WE",
"https://en.m.wikipedia.org/wiki/Common_external_power_supply"
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9iugli | how does mobile app traffic appear to admins on a monitored network compared to regular browser traffic? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"They're likely tracking via IP address and/or domain. Most mobile apps just make API calls over HTTP, so it looks just like web traffic. You're better off using data rather than Wi-fi.",
"Mobile traffic looks just like desktop traffic for a specific app (that is to say, if you load a webpage in a mobile browser vs a desktop browser, it pulls the same web page) And if there is a type of traffic that is not allowed (say, opening gambling sites, like aforementioned fantasy football) then it would be flagged and blocked just the same. Now, as for being caught, that depends on what the network admins are doing. For myself, I can see the device name, which often just says \"Android\" or \"Apple\" followed by some numbers, the MAC address (unique to your device) and IP address (assigned by my DHCP server) I could ban your device from the network if I caught it accessing forbidden sites (but we just use a filter to block access to gambling websites and don't care), but I can't know for sure it belongs to you unless you changed the device name to reflect your identity (like naming it \"hutdonuttuttut's android phone\") In a larger corporate network, you might be required to register your phone before you can have access through the WiFi (which works based on MAC address), in which case, your company should know that the device accessing that site belongs to you- but you would know if you got your phone registered on the network because you would have to have either submitted a request or signed on through a portal that asked for something to identify you, much like the portals used by hotels to limit access to the hotel WiFi to people who are guests will ask for a room number and the name on the reservation. --edit-- I just want to add, because I was checking our WiFi for other reasons, it looks like people's iPhones and iPads automatically append their first name from their profile to the phone name, so if \"your friend\" has an apple device, then the jig may be up for him. (on my network, 5 apple devices have a name appended as \"[user]s iPhone\", three are generically iPhone) Also, I forgot to mention, in a multi-access point system, the administrator usually can find out which access point you are connected through, which narrows down your physical location. If you're the only person with your particular first name who sits near the access point closest to your desk, and you have an iPhone or iPad, then it could be very easy to determine that you're the owner of the device."
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9ivhcr | How a DNS Sinkhole works? | I'm doing a project on the wannacry ransomware and have stumbled upon the question: How was it stopped? & #x200B; So I researched that, but it mentioned a DNS Sinkhole, and no matter how much I read about it I can't seem to find out what it means. Please explain to me how they work and how it stopped the ransomware! | Technology | explainlikeimfive | {
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"When you ask to connect to “ URL_0 ” you have to ask a DNS server “what’s the IP address of URL_0 ?” A normal DNS says “ URL_3 is at 151.101.1.140” and your computer connects to 151.101.1.140. A DNS sinkhole says “ URL_0 is at 0.0.0.0” or some other nonexistent address, and your computer tries to connect to 0.0.0.0 and fails because that’s not a real address. WannaCry was coded to turn itself off if DNS servers gave it any address for “ URL_2 ”. That domain didn’t exist, so DNS servers would have just said “I don’t know” when asked. A security researcher found the domain in the code, and tried registering it. So DNSs started giving out an address for it, and WannaCry turned itself off. (Specifically, WannaCry stops spreading / infecting new computers if the domain is sinkhole’d or registered. Already infected machines are still infected. Also, this only works for that version of WannaCry so it wouldn’t help if a new version without that kill-switch spread) Source: URL_1"
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"reddit.com",
"https://www.malwaretech.com/2017/05/how-to-accidentally-stop-a-global-cyber-attacks.html",
"iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com",
"Reddit.com"
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9iybvs | Why are videos often 29.97fps or 59.94fps instead of just 24/60? | Technology | explainlikeimfive | {
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"text": [
"Because NTSC was just a bit off in every regard Black and white TV consistent of just a brightness channel and ran at 30 frames per second. Color TV had to add a color channel on top of the existing brightness information, due to frequency dividers at the time they had to make the color subcarrier be 3.579545 MHz(5x7x9/(8x11)) and since they needed whole numbers for the dividers for horizontal refresh they ended up with ((5x7x9)/(8x11))x(2/455)=9/572 MHz=15,734 lines per second which on a 525 line screen is 29.97 frames per second (Bleh) NTSC picked up many weird quirks because it wanted to maintain full backwards compatibility with black and white televisions. You could pump a color tv signal into a black and white TV and it would look just fine, the downside was the standard got weird If you ever forget the name of the color tv standard or ever wonder why its weird, the mnemonic I was told was \"Never Twice Same Color\". It worked well enough with everything but wasn't great at anything.",
"In the beginning the television was 30 fps. When colour was introduced, the frame rate was dropped slightly to 29.97 fps in order to fit colour information into the signal without increasing bandwidth. URL_0"
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9iywvj | What is a generator in electricity? | Technology | explainlikeimfive | {
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"text": [
"It's like an *electron pump* that pushes electrons away from one end and toward the other end. This creates a *voltage* (electric pressure) which is then used to power the flow of electricity through wires and other things.",
"I majored in physics and it sounds like these answers are dancing around what is causing the current. First you need a wire. This supplies the electrons that will become a current. In order to make them move you need to have a moving magnetic field. A generator simply uses some fuel to turn a magnet. If the wire (electrons specifically inside the wire) is coiled and inside a continually changing magnetic field it creates an emf (or electromagnetic feild). And bam. Electricity. These forces are always tethered. Moving charged partials will in turn create magnetic fields. Hope this helps."
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9j31ey | Why does the longevity of a cell phone battery decrease over time? | Technology | explainlikeimfive | {
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"text": [
"Well you know what happens when you use a pencil right? Eventually you have to resharpen (charge) it. What happens when you do this? The pencil gets shorter. ie. its lifespan shortens. Why? You're using all the lead up slowly (electrolytes in a battery). Same way in a battery, as you use the electrolytes in the battery with each charge, some of them are no longer able to hold a charge, all the way until current can no longer flow and the battery is dead. EDIT: Some comments are rightly pointing out that not all batteries are liquid cells. This is correct. However the principal in my explanation is the same. Batteries that rely on chemical reactions never maintain 100% efficiency, so you lose some potential each time you reverse the reaction. Do this enough times, and eventually there's barely enough left to charge at all. It's a slow process, but the same in practical terms none the less.",
"Batteries function using a reversible chemical reaction. Each chemical reaction can never reach 100% yield. Each time the phone is discharged and recharged, it has a little less capacity each cycle until one day it becomes impractical to use.",
"Cellphone batteries these days are almost entirely based on using lithium and two different materials called electrodes. When you charge one of these batteries the lithium is \"pushed\" from one kind of electrode to the other. Now one set of electrodes has more electrons than it needs and the other set has less than it \"wants\". This is the electrical equivalent of picking something up, there is a potential now, but nothing is happening yet. When you connect a wire between electrodes the difference in electrons (the positive and negative charge) evens out and the lithium is \"pushed\" back the other way. In theory that process can happen over and over forever, but there are 3 things that can go wrong. There is a physical barrier between the electrodes, think of it like a net. It makes it so that the lithium isn't able to move back and forth easily. Over time that can wear out, get small breaks in it that allow lithium to move back and forth too easily. Another thing that can go wrong is the electrodes themselves can break down so they don't work as well anymore. One of the last things that can go wrong is that when a battery is over charged, gets too hot, or has something wrong inside of it physically a chemical reaction can happen that produces gas and can't be reversed by charging the battery. If you have ever seen a battery (or a phone) \"swell\", that is because there is now gas building up inside of the battery. When that happens even if the initial cause was a very small imperfection, the gas buildup generally breaks the battery more inside and it should no longer be used because if too much gas builds up the battery can \"pop\" and what is inside can be very flammable and toxic."
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9j71fm | How do phone trees know what number I pressed? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Each number has a tone (touch chord) assigned to it. The \"phone tree\" can tell the difference in the tone and route your call accordingly. With a little practice you can play Mary Had A Little Lamb pretty easily. Here's a link to the exact tones each number makes: & #x200B; [ URL_0 ]( URL_0 ) & #x200B;"
],
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"https://www.losdoggies.com/archives/1206"
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9j7qhn | How do random number generators work? | Technology | explainlikeimfive | {
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"text": [
"They start off with a seed value. Something like the current system time down to the millisecond is common. Starting with that value, an algorithm does a number of binary operations on it, creating a sequence of 1's and 0's that are then interpreted as a number to be returned by the generator. The process can be repeated to create more sequences and thus more numbers. These are called pseudo-random numbers, as if you feed the algorithm the exact same seed value, it will result in the exact same sequence of numbers. But a good algorithm will make the distribution of returned values evenly spread out and appear random enough for most practical purposes.",
"A trivial way of doing it is using modulo (remainder) multiplication with prime numbers. say p=5, q=7. The seed is a starting value, s=2. Then it uses the equation f(1) = s. f(n+1) = f(n) * p mod q. Using this iteratively will generate values: 2 (2 * 5) mod 7 = 10 mod 7 = 3 (3 * 5) mod 7 = 15 mod 7 = 1 (1 * 5) mod 7 = 5 mod 7 = 5 (5 * 5) mod 7 = 25 mod 7 = 4 (4 * 5) mod 7 = 20 mod 7 = 6 (6 * 5) mod 7 = 30 mod 7 = 2 So we've completed a loop of numbers. 1 to 6 (q-1) but they 'appear' random. Obviously the algorithm will use bigger numbers for p/q so it doesn't repeat so often. P/Q are secret to the algorithm but if you can find out what they are obviously you can calculate the next value. So not very secure. Newer algorithms will use a 'jitter' or some additional value (keypresses, interrupts, heat sensor etc) to do something more like (p * n + c) mod q."
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9j7vag | How do computers store audio? | I know how photos are stored. Every pixel has 3 values for red, green, and blue (some files have 4 adding transparency) but how does audio storage work? Is there an audio "pixel" that's just one unit of sound that has different values? | Technology | explainlikeimfive | {
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"> Is there an audio \"pixel\" that's just one unit of sound that has different values It's called a \"sample\" and it represents the position of a loudspeaker at some point of time. Most audio uses 44,100 or 48,000 samples per second of audio per channel. That's an awful lot of data, so its compressed. Most of the time they use \"perceptual codecs\" which are algorithms which mimic how your brain/ear work in order to find what data is least important and tosses it out. It's not as simple as tossing out a sample here and there, it has to do with manipulating the energy that those samples represents.",
"I want to add a few small things. The first is that most pictures aren't stored quite the way you talk about. What you're talking about is called a bitmap, and in a bitmap, you're right, every pixel is represented by three, typically 8 bit, numbers representing the RGB values (or if it's grayscale it's just one 8 bit number per pixel). The problem is, pictures can have millions of pixels, and if each one needed three bytes, a single picture would take up a LOT of space. So most pictures are actually stored as jpegs. Jpegs take the original RGB bitmap and convert it to a different color scheme: Cr (change in red), Cb (change in blue), and Y (the luminance or brightness). The conversion is straightforward and has all the same data. However, your eyes are much more sensitive to luminance than to color. So knowing this they basically cut out a chunk of the Cb and Cr data using some sorta complicated math I won't get into here. The result is that you lose some quality, but the image might take up a tenth as much memory without really looking much different at all to the human eye. For audio recording most people are right that your computer takes samples, often at or above 44,000 times per second (which is twice the upper range of human hearing), although modern ones sometimes go faster. However, instead of recording the straightforward 'height' of the wave they use what's called Delta-Sigma modulation, which, in a quick explanation, means they store the change in height between each sample instead of just the actual value of the sample. It's usually a bit cleaner without being much more expensive or difficult to set up."
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9j8fgt | How do photo restorations work? | I've always wondered how they work. Like how do they even know what it's supposed to look like! | Technology | explainlikeimfive | {
"a_id": [
"e6piron"
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"text": [
"Depends on how much the photo/painting is damaged or how much is left, or even of what needs to be done to it. In cases of restoring cracks you’re literally just drawing in the blanks with what you see around it. Kind of like fitting in puzzle pieces. A lot of it is done mathematically based on proportions if you’re piecing people back together (ie drawing in a missing chin/ shoulder, or if you’re doing something like opening someone’s eyes). In terms of clothing it helps to have a background in history and art to know what styles people were wearing at the time, or even how clothing folds so you can draw it in believably. It may not always be *exactly* like it originally was, but you try to get it close and make it look like it’s not drawn in and completely out of place. In super old photos like cabinet cards (the ones you see in flea markets on cardboard) or tin types (photos literally on metal) there’s special processes that exist that let you photograph them traditionally letting the detail “pop” out. You make copies and fix cracks/smudges, to be printed out on regular photographic paper later. Most of the time now these processes are done in Photoshop by professionals, but in the past they were hand drawn on the originals, or photographed, made copies of, and worked on the copies, since most people like to keep originals, or they’re too delicate to be touched and fiddledwith. Or, like tin types, there’s not much you can do. Not sure if I’m explaining this like a “professional” but your question is really broad. lol. Source: my mom is a fine artist and art conservator. I grew up at her feet in the darkroom. There’s a lot of examples and a bit of info on her site: URL_0"
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9j9vj9 | How does exactly does a game like Minecraft randomly generate a world without it being utter chaos? | Technology | explainlikeimfive | {
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"I have made procedural terrain generation as a project so I have some knowledge on this. A lot of the terrain generation is done by what's called noise. When you think noise, you probably would imagine something like this: URL_0 You've seen something like this in static TV screens. It looks like a completely random array of pixels, and is too chaotic to make a terrain out of. What you want is these kind of noise: URL_2 This still looks random, but it doesn't look chaotic; it has some order to it. Each pixel is coherent with its neighboring pixels. It doesn't suddenly go from completely black to completely white. Now imagine that this image is a top down view of the ground, and that the whiter pixels mean the ground at that point is higher. You've now created mountains out of bright spots, and valleys out of dark spots in the image. This is what you'd call a height map. The noise in that image is 2 dimensional (width and height). We can go further by creating a 3 dimensional noise like this: URL_1 If you dig the world in the shape of above 3 dimensional noise, you've now created a cave. Noises like these can also be used to determine where the ores and trees will be, or how deep the dirt is in a given point of ground in a non-chaotic looking manner.",
"Hey there. I am actually working on Minecraft world generation, so let me give you a quick rundown on how it works. First of all, Minecraft worlds are not created randomly, but procedurally. It means that we are using elements that appear to be random, but actually follow rules. I think the best way to show that is to decompose the world generation in steps and detail a bit what we are doing in each. + First, we need to know where the terrain is. For that, we use a noise map. It is basically a function that we can call with coordinates and which gives us back an altitude. If you call it with the same coordinates, you get the same result. The world seed changes what the function returns, but for a given seed, it will always be the same thing. For more information, URL_0 + The original terrain is just stone and air, so we fill things with water if we have air below a given altitude. + We determine the biome. This is done by following a set of rules. Imagine that each block is a pixel on a picture. We start with a really low resolution version of the picture, in black and white. We start zooming in and adding more color. At the end, the picture is the size of the world and every block has a \"color\" (or biome). + Next step is to carve the terrain for caves and canyons. For that, same thing, we apply a know carving method which starts at a given position and follow rules. All caves are carved in the same way in that the caves are following the same rules, but depending on where you start from and the world seed, you get different result. + We apply the top layer of the terrain depending on the biome. + We check what features a biome can have (trees, grass, etc) and we start applying them in order. Each feature has some randomization (trees can be small or big, leaves are not always at the same position), but this randomization is determined but the seed and the position. If there is a tree of a certain shape at a given position, it will always be this shape at this position for this seed. Features know roughtly about other features, so we can react to what was already placed and not have overlapping trees for example (unless there is a bug ;)) And that's it, in a short form. The take here is that the generation is not random. It follows rules. A tree is a tree, a cave is a cave. But the fact that the cave is turning right instead of left, or the fact that the tree is a big tree instead of a small tree is determined randomly based on the position and the seed. This randomness is deterministic. For a given set of position and seed, the result will always be the same. Cheers !",
"There’s most likely a code that the computer geneting the world has to follow. For example the code will make sure that the grass is on the top layer and that diamonds are deep in the ground. There are also usually certain algorithms used to keep things organized and seemingly random at the same time.",
"So you can use logic trees to somewhat dictate the way it's generated. It IS still at random however lets say one rule is grass must always come above dirt. Then extrapolate from there until you have made your logic tree. So grass will usually be on dirt which is usually on stone. So on."
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9ja80s | How exactly does DRM work in video games? | I've seen a lot of top level explanations for what DRM is for, but not really how it works. Somewhere in between clicking play in steam and the game actually starting there has to be some lock that opens. When I close the game, that lock has to be shut again. What is that lock doing? And why can't I just find the executables on my computer and bypass the whole thing? | Technology | explainlikeimfive | {
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"I'll answer this very vaguely before someone else elaborates. The DRM is built into the exe. You can't just find the exe and start it. Steam DRM is very basic. It is basically just verifying that the exe you have is legit. The exe is \"wrapped/encrypted\" And when you press launch in steam it \"unwraps\" the exe, making it launchable. There are a lot of different DRMs. One of the oldest is product keys. This is used as a basic primary DRM. Now we usually see online verification. This can be done in multiple ways. Ubisoft used to not give you the whole game. The last bit of game code actually downloaded while you played. And you had to have a valid connection to the server for this to work. Don't know if they still do this. There is also general online validation where your game has to contact a server to check that the installation is valid. Video DRM works by encrypting the video and then decrypting while you play it. HBO etc. do this. In short, DRM is not simply a lock. It's different ways to make sure that the game is legit. Be that constant online verification or product keys.",
"Well there's really a variety of different methods. The other thing to note is that most DRMs don't really work for long. You can finds all kinds of cracked games online, including plenty that had DRmM. Some early versions of DRM limited how many times something could be installed. They'd check with a server to see your license code was only used on a certain number of computers, and if you tried to install it on more than the allowed number the server would tell it not to follow through with the installation. This was for the most part a huge inconvenience though for regular paying customers, and was actually credited as being the reason Spore was the most pirated game the year it came out. Some might do other more consistent online checks. When the game boots up it might check that you're using a valid account to start it, and that your account is licensed to use the game. If it's a multiplayer game this is even easier. Even if you managed to get around that check by changing the game files, if you wanted to connect to play online the servers would just reject you since you weren't licensed to play the game. Others just use license keys. In older games the checking was done internally by algorithms built into the game. So people could replicate those algorithms and you could generate working codes without buying a copy of the game. Newer ones check with a server though so it's harder to generate codes that work from somewhere else. The short version is that they try and get you to connect to a server. If the game checks with a server, and all the verification is done by the server (unseen by you) then it's hard to get around. For multiplayer games, this really makes it hard to bypass. But, once you have the files on your computer, and you can run them, it usually doesn't take too long for people to figure out work arounds. The game might have other checks kind of hidden inside of it that make sure it hasn't been tampered with, but with enough effort a workaround pretty much always ends up being developed. However this is where a personal favorite of mine comes in. Some games have built in software tampering. If it suspects the game has been altered and that you're using an illegitimate copy it won't lock you out, but it will mess with you. Sometimes they might make unkillable enemies that block your path so you can play, but you can't progress very far. I know there were Pokemon games that would keep you from earning XP for your Pokemon, so after the first few battles you'd just be crushed. There was also a game I read about a while ago where you basically play as someone managing a game development studio. If the game thought you were using a pirated version whenever you tried to sell a virtual game inside the actual game, it would get pirated causing your virtual studio to lose a bunch of money and eventually go bankrupt, so it was unwinnable. People would then go post on the forums asking how to prevent their studio from going bankrupt thanks to pirating, which would ironically reveal to everyone else that they were using pirated versions."
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9jc8wd | why do some Windows programs ask you to give additional permission to run/install themselves etc.? Couldn't a malicious program just click the Yes confirmation anyway, and if not, why not? | Technology | explainlikeimfive | {
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"The UAC prompt (User Account Control, the window that asks Yes/No if you want to allow a program to elevate it's privileges) runs in the 'secure desktop'. The program which requested the elevated privileges has no way (without already having very high privileges) of interacting with that secure desktop. That's why the program can't just click Yes by itself - when that dialog box appears, you're seeing a secure desktop which is heavily locked down to the point where most non-kernel software can't interact with it in any way.",
"The progams don't ask you for permission to run, windows itself asks you if you want to give the program permission to run. So, for a malicious program: 1. You accidentally click on program / download something with the program in it and run it 2. Program, needing access to sensitive files/information, tells windows to give it the info 3. Windows asks you, the owner, for permission to let it give the programs that kind of info/access",
"ELI5. I'm selling/giving away cookies (software). You come and grab some. But before you can eat them, your mom(the OS) stops and askes very seriously \"do you trust u/dazza93?\". I can't tell your mom anything except the cookies' name. If you don't trust me your mom will take the cookies away (stop the program), for later if you trust me. You can tell your mom to throw the cookies away as well."
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9jhrch | IP addresses, subnet masks, default gateways | Technology | explainlikeimfive | {
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"An IP address is like an address for your house if you weren’t allowed to use words. So if you lived at 3, Pierre street, Paris, France, we might all agree that France has a code 192, Paris has a code 168, Pierre street has a code 0, and your house has a code 3. So I wanted to send you a letter I could just send it to your address using these codes, starting with the most significant number first. Your address would be 192.168.0.3 This is a really typical domestic network IP address... For there not to be confusion, it’s important that no two devices have the same address or, in the analogy of houses and posting letters, if two addresses are the same, the postman wouldn’t know where to take the letter. Now you’re home network probably isn’t very vast so it doesn’t need to be very complicated and doesn’t need all these layers of addressing, so everything on your network probably has the same three numbers. Your PC is 192.168.0.3, your phone is 192.168.0.4 etc etc. The subnet mask defines which devices can talk to each other by ‘masking’ parts of the network... For example, in the analogy above a subnet of 255.0.0.0 masks the first part of the address so you would only be able to send letters within France... 255.255.0.0, you can only send to addresses in Paris... 255.255.255.0 you can only send letters to houses on your street... The router gets a address too... let’s say it’s address is 192.168.0.1... this is the same as the ‘default gateway’ it has to be on the part of the network you can send letters to. And it’s where all the letters go that you send where the address is not found on your network. So let’s say you’re only allowed to send letters to to your street and you want to get a letter to Brazil at 179.68.235.154... this address doesn’t exist on your street, so it will be passed to the router at the default gateway address where, hopefully it can be passed on to the correct recipient. In reality, the router on your network is the bridge between your home network and the network that is the internet. It means that your home network can be addressed how ever you like without accidentally having the same address as everyone else’s devices on their home networks."
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9jk1hn | How does "barehanding" or "hothanding" work for power lines | I saw a thing about it in TIL, and I don't understand how it works. The explanation they use is that it's the same reason why birds don't get hurt, which I also don't understand. Thanks! [ URL_0 ]( URL_0 ) | Technology | explainlikeimfive | {
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"So hothanding or bare handing works because you haven't completed a circuit. Remember, electricity travels through the path of least resistance which would be the metal cable, not your hand. So since you are neither grounded (touching the ground) or touching the other cable (because a circuit has both a negative and a positive terminal) you do not complete a circuit and thus won't have any current running through you. If you want a safe experiment that uses a similar principle, take a 9 volt battery. Put your tongue on a single terminal, then put the tongue on only the other terminal... Nothing happens... Now let your tongue touch both terminals, suddenly the circuit is complete and your tongue will start to tingle from the electricity. Edit: specifically to the video, they wear a conductive suit such that if any current would hit them it would instead pass through the suit to a ground safely rather than passing through their body to the ground. If a current passes through your body you risk causing cardiac arrest (if DC) or ventricular fibrillation (AC). Both of which are potentially fatal (though VFib is generally easier to treat as a defibrillator actually stops your heart so your body can reset it... But if your heart is stopped then shocking it won't do anything)",
"Electricity is trying to move from higher potential to lower potential (volts). Let's say you shake a soda can, that pressure is high potential. So when you open the can, the soda comes violently shooting out onto the floor, right? But once it's on the floor it does... It does nothing, it just sits there, because it is at the same potential as the environment now. Hotwork is the same thing. If you're standing barefoot on the ground you're at 0 volts of potential, while the power line over you is at thousands of volts of potential. Given the opportunity, the power would run through that line to you because you would be a handy escape to lower potential. Hotwork involves using special non-conductive boom lifts, ladders, or even flying in on a helicopter. These are separating the worker from touching the ground (Earth is always 0 volts potential), and when they come near the wire they use a special stick to bond themselves to the wire, that clamp-looking thing that it arcs to. So now the worker himself is at whatever potential the power line is, 120,000 volts or whatever. At this point it is just very *very* important that the worker does not go near anything of a different potential, because now he's a shaken soda can, and going by a big metal tower staked into the ground (which makes it 0 volts potential) or even getting too close to a nearby power line that is only 50,000 volts, there is now a difference in potential and it'll flow through him to try to even that \"pressure\" out."
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9jmycc | What does the different sections of the 3.5mm headphone jack do? | Technology | explainlikeimfive | {
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"Not in right order but dependent on which headphones Mono head phones will have a left and right path with a ground (2 sections) Stereo has 3 sections left path right path and ground Headsets with mics have 4 sections left path and right path. Microphone and ground. Ground is always needed to make a conplete loop for electricity",
"For stereo headphones, you would expect to see three sections: * tip * ring * sleeve Generally, the tip is used to send the left audio channel and the ring is for the right channel. The sleeve is the ground, and is shared beneath the two channels. It's required to complete the electrical circuit and allow current to flow. Headsets that include a microphone have two rings instead of one, and mono headphones don't have a ring at all."
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9jrjc1 | How does Google Maps know to update bus routes? | Technology | explainlikeimfive | {
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"Many transit agencies, before or when they change routes (keep in mind route changes are usually planned months in advance), will publish a GTFS (general transit feed specification) data pack, which Google can quickly import to overlay on top of their maps, and/or replace timetables.",
"About 2 years before the first smart phone came on the market (2006), the General Transit Feed Specification (GTFS) was released by Google. About the same time, a few cities were adopting new rules about how they shared their data because of an initiative called Open Data. Transit agencies quickly discovered that if they shared their transit data with Google through GTFS, it became a free tool to help riders plan their trips and know the next predicted time a bus should arrive at a specific bus stop. When transit agencies also published this data as Open Data, route planning mobile apps could access it as well.",
"About 10 years ago Google was off. The bus times were off - sometimes by about 10 minutes. (Think about trying to get every bus, on every bus stop in the entire United States right.) & nbsp; Listen, I'm a progressive but technology isn't all evil. What Google and One Bus Away have achieved is nothing short of amazing. I know exactly when the bus is going to show up and if it's going to be delayed. & nbsp; A farmer in 1880 would not be able to comprehend this."
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9js9h4 | How do radios “tune” to a specific frequency? | Technology | explainlikeimfive | {
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"Imagine a water gun that shoots water in a straight line on to a wall with a hole in it. The gun cannot be moved at all and always shoots water at the same rate. The wall however, can be moved, and you can bring the hole closer or further away from the water jet. If the hole in the wall is far away from the water jet, the water will only hit the wall and splash everywhere, and it won’t make it to the other side. The closer the hole gets, the more tiny droplets of water will make it through the hole, but you won’t get a nice clean jet of water on the other side. However, if the gun and hole are perfectly aligned, the entire jet of water will go through the hole undisturbed. There are many water guns (radio stations) but only one hole (the radio itself). Moving the wall to match it to a specific water gun is what we call “tuning”.",
"Have you ever seen those hidden message or image pictures where there’s two or more colors overlaid and when you put on glasses with lenses the same shade as one of the colors it makes it so only the other colors stand out and now you can see the image? Well radio uses a carrier band signal at a much higher frequency. FM or frequency modulation takes and alters that frequency slightly based on the audio signal you want to transmit. Example: carrier is 1,000,000 (1 mega hertz) and you have someone talking at a much lower frequency (5,000 hertz) for a total of 1,005,000. But to “decode” it you need to tell your radio what the carrier band is. Without the carrier it doesn’t know if the audio is 5 hertz, five thousand , 15 thousand, etc etc."
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9jskzo | Could display cables (like HDMI) ever be replaced by a wireless alternative? | Technology | explainlikeimfive | {
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"There actually are some (kinda low quality and fairly expensive) “wireless HDMI” connectors out there already. There are also a few different designs that use Wi-Fi to communicate video/audio (a lot of smart TV’s can actually stream from a windows computer this way, personally I use it to stream my tv shows that were acquired in... somewhat less legal fashions). The big drawbacks with these just tend to be how fast the connection works and how sensitive it is to interference. A direct wire is almost always going to be better than a wireless connection, but given how fast technology is improving it’s certainly possible we could eventually reach the point where we connect wirelessly as the normal method.",
"Wireless links are used with in the professional broadcast and video world. They're usually referred to as \"microwave links\" and will be used when running a cable is not possible. [This product]( URL_0 ) can take a HDMI input. It compresses the video signal to h.264 as the uncompressed HDMI signal is too big to fit in the available bandwidth. So to answer your question, they can be but the signal must be lossy compressed so it's not as good as a wired link."
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9jsla0 | Trans Atlantic calls in the early 1900s | Watching darkest hour. I dont know why I never thought of it before. How did they talk on the phone trans Atlantic back then? I know it was only for the super elite and world leaders. It just seems to me that in those early days it had to be a hardwired grid. | Technology | explainlikeimfive | {
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"The earliest transatlantic cable was completed in 1858. So yes, it was a hardwired connection. But guess what? It still is! The vast majority of communication still occurs over landlines so you calls today go over such cables."
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9jsqkw | How does a game know what to load when you select a load to play? | Example: I just started playing the original Borderlands on my computer and noticed I had an old save from years ago, how does it save the entire world I had years ago for me to access at any second? | Technology | explainlikeimfive | {
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"Your saved game is a file that looks like > Player location - coordinate (1,2,3) > Inventory - Shotgun, 26 shells, and a stick of gum > Enemies - monster126 at coordinate (3,2,1), monster127 at coordinate (2,3,1) and so on and so forth with all the data about every little thing in the world.",
"You have a library full of books (game files) and you have a notepad that has a record of what books you're currently reading and what page you are at with them (your save). Whenever you want to read them, you go into the library and pick the books and go to the pages according to your notepad (loading the save). You don't make copies of books every time you read them (not saving the entire world). You just remember where you were and pick up the books from the library."
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9jtggd | Why is there an interference with bluetooth headsets whenever shredding documents? | Technology | explainlikeimfive | {
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"Put electricity of a certain frequency into metal of a certain shape and you get radio waves, like the radio waves that carry bluetooth. Put electricity of a certain frequency into metal wrapped around a core that can spin, and you get a motor, like the motor in your shredder. Since the motor has metal and electricity it will emit some radio waves, if it's designed poorly it will emit lots of random radio waves (essentially noise) at the same frequency as something else like your bluetooth headset. The headset can't \"hear\" the bluetooth signal over all the radio \"noise\" generated by the motor in your shredder."
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9jtolz | What is the difference between C, C#, C-- and C++ other than the fact that they are different languages? | I'm assuming for the most part that C#, C-- and C++ are based on C. But i have no idea how to code so I would like a detailed explanation on the difference between the four. As many people have stated, C-- is a language for compliers. It's a language, but it isn't used as often. | Technology | explainlikeimfive | {
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"Just to point something out here, you're basically asking to boil down 50 years of engineering into one post. I'm not going to talk about C-- because I don't know anything about it, and afaik it's not really used by anyone. Someone else can help you out with the history, but basically C++ was derived from C, and C# is only \"C-like\" in some of the syntax, kind of like how English is \"German-like\" or \"French-like.\" C and C++ are compiled languages. This means that the source code is converted to machine code (raw binary) before the program can be run. C# is an interpreted language. This means the source is translated on the fly into pre-compiled subroutines. C is a very small language, and a working C compiler is very simple to make (note - not a \"good\" compiler, just one that functions). C++ is an extremely dense language, and \"modern\" C++ doesn't look much like C code at all, but most C is valid C++, while very little C++ is valid C. C is more or less portable assembler language, meaning writing it is similar to how one would write the raw instructions provided by a processor manufacturer. It doesn't *look* like that, but if you understand how a processor works, C makes a lot of sense. Processors however have moved very far past the models that influenced the design of C. This has drawbacks in all languages, since most are influenced by C, but languages like C++ and C# have been able to provide different features that can in some cases better reflect modern systems. C is a \"procedural\" language, meaning a C program is a glorified list of instructions for the processor to execute. C++ and C# are \"object oriented\" languages, which means that instead of being just lists of instructions, they define \"objects\" of data and \"interfaces\" for how those objects interact. This is complex for a processor, but is a useful paradigm for large software systems. C and C++ are both \"close to the hardware\" meaning you can directly interact with the hardware. C#, being interpreted cannot. This means you can write \"bare metal\" (no operating system) programs in C/C++. C and C++ are commonly called \"systems\" programming languages. There isn't a good definition, but it usually means you can write the highest performance code possible using them, since there's nothing in the way. C is a small language, but this makes writing complex software very difficult. It's easy to pick up C, and it's a great language to build fundamentals on since it teaches you both how to write code and how a computer actually works. That's the basics. There's a lot of more stuff going on but it won't make sense if you don't understand basic programming concepts.",
"C was revolutionary language developed in the 70s, C++ came out in the 80s as an extension to C that added \"object oriented\" design features. The name is a play on the ++ operator in C which increments a variable. C-- I had to look up, it's certainly not widely used, and it's just another play on an operator. C# came later, it was developed by Microsoft primary to compete with the rising Java. The # is a play on the ++ being merged together at an angle, and while the language syntax is similar, it is quite different from the others. It is not directly backwards compatible the way C++ is to C, and it doesn't run directly on the machine, instead going through a virtual layer that handles a lot of busy work for the developer, this compromises performance but makes it easier to focus on features. C and C++ are primarily used for high performance tasks, such as running on embedded systems with limited power, or writing things like game engines or operating systems. C# is used at a higher level such as games, apps, websites, etc",
"I'm not sure how to explain the differences in coding languages in a simple way to someone who doesn't know how to code. The main difference is a concept called object oriented programming, as contrasted to procedural programming. Procedural programming is the most straight-forward way to think about programming. You have a list of things you want the computer to do, so you tell it to do those things, in order. Object-oriented programming doesn't focus on the tasks themselves, but on the elements of the tasks, and tries to section off pieces of the code into discrete chunks that are called \"objects\". An object has data (like numbers of words) and also methods (functions that do things with the data). Neither approach is universally better, but in some cases one is clearly better. C is the original language, and it's very basic. It was formed in the era of procedural programming. It has a kind of nascent support for objects, but it's not really fully there yet. C++ is the extension of C into object orientation. The extension is very natural and fits very well with the original syntax of C. The main differences are: the syntax to print statements to the screen is changed, the syntax to manage space in memory for storage is changed, and the standard library in C++ includes support for things like variable-length arrays called vector. Apart from that, the two are mostly compatible, and code written in C can usually be transferred to C++ without any edits. C# is similar to C++, but specific to Windows. I've never used it, so can't comment much on that one. I don't know what C-- is, but I guess it's an appropriate name for Objective-C, which is the Apple extension of C to object orientation. Objective-C is a hideous, horrible, frankenstein monster of a language, formed by almost literally duct-taping two completely different languages together and then never bothering to seam them up. Whereas C++ treats objects with the same syntax it uses for numbers and stuff, Objective-C has a completely different syntax for objects than the one it uses for numbers.",
"This is hard to answer because it's more complicated than you think. C-- is not something most people will find useful so we won't mention it. C is the basis, it was developed in the 70's by researchers at Bell laboratories. It's a fairly low level language, which means that it puts you closer to the hardware and manual memory management than higher level languages(python, JS, Ruby) will. C++ came about in the mid 80's and it's name is a bit of a programming joke. C++ is the same code to say C = C + 1. It took C added a ton of new features. It did not replace C. C# rolled around in 2000 and is a Microsoft brain child. It has a lot of implementations to keep it safe and is namely used in windows applications Hopefully this helps a bit."
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9jtv46 | Why do computers have a shutdown process instead of just cutting it's own power? | Technology | explainlikeimfive | {
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"For the same reason that people generally lie down before going to sleep instead of just falling over: To avoid damage. At any given time, a computer is running a lot of programs in the background, and they need to be safely closed before the computer shuts down. Many of them also save their state during their shutdown procedures, so they can resume where they were when the computer comes back on. These programs can be extremely important to the operation of the computer, and if things don't add up when it comes back on, the operating system itself won't run anymore."
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9jwyej | How has twitter closing off its API affected third party developers? | Technology | explainlikeimfive | {
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"I have no account or app, and I can no longer see the end linked by news sites. That's huge, as they don't directly post videos or pics on the news sites themselves. That has got to change!"
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9jygdc | OLED Displays: Samsung vs Apple | Technology | explainlikeimfive | {
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"Apple can toy with software and graphics a little but in the end they’re the same. Neither display really has any additional capability than the other. Apple also has 3D Touch Samsung doesn’t. But apple buys a Samsung screen and then calls it something retina and that makes it apple... and as the previous poster above stated, apples pays Samsung a lot for them."
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9k3d6w | How do Wire Transfer work? | I understand it's a means of digitally transferring money, but my economics and understanding of banks may be limited. As a wire transfer is digital, what happens to the paper money? Do banks just write IOU's in essence to each other? | Technology | explainlikeimfive | {
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"A wire transfer is when a bank transfers money to another bank on behalf of an account holder, for the other bank to then credit one of its account holders. And it is always done exclusively, so a payment is made to the other bank only for the amount in the wire transfer. On the other hand, ordinary ACH bank transfers are bundled and sent as one check. There is never any actual paper money exchanged and this is why anybody submitting a wire transfer has to have a money transmitter license and be audited to make sure they aren't just making up the money from thin air. Unless of course it's the Federal Reserve who can transfer newly minted money electronically to other banks instead of printing cash."
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9k3i0y | Why does the pitch of voices go up or down when you speed up or slow down a video? | Technology | explainlikeimfive | {
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"Pitch is based on the frequency of sound waves, or how often those waves hit your ear. When you speed up a video, the waves come faster; likewise, when you slow it down, they come slower. This has the same effect as a higher or lower pitch"
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9k3l5f | What makes a CPU well, a CPU? | Basically, what gives CPU their properties? | Technology | explainlikeimfive | {
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"A CPU can be considered a \"jack of all trades\" processor. It packs many functions under the hood to be able to do all sorts of things. At one time before graphics cards became pretty much standard for playing PC games, they even did the processing for that. A CPU can and in most situations has other chips helping it; a GPU will be doing the drawing of frames on a game, a sound chip will be decoding the sound data and outputting to the correct channels, etc. In pretty much every scenario the CPU is the \"man in charge\" on the motherboard though. But at the core of the question, it's all in the name Central Processing Unit. Pretty much could be whatever is the \"heart\" of a device, whether it's a chip that's mainly a DAC with some extras to control a display on a soundbar, a simple chip purpose-built to operate a modern washing machine, whatever. Those aren't CPUs in the strictest sense but might be called a CPU by someone for being the \"man in charge\" on their circuit boards."
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9k4q7r | How do computers turn a million yes and nos into a basic program? | At it's most basic level, I don't understand how you turn that input into complex programs. | Technology | explainlikeimfive | {
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"The order of the yes's and no's matters. Let's call yes (1) and no (0). A container that hold a 1 or 0 is a *bit*. Now let's make a rule that 4 bits in a row is a *nibble*. We could choose any number, but 4 is a good number. Now I'll make another rule. There's a way to turn a nibble into an integer. The value of a nibble *abcd*: a * 8 + b * 4 + c * 2 + d. So If want to write \"1\" as a nibble I write \"0001\", and 7 is \"0111\". (This is the *binary number system*.) **Key idea 1: we can turn a list of \"yes\" and \"no\" into numbers (integers).** Now I'm going to make another rule. There are triplets of nibbles. The first nibble we'll call the *opcode*. The next two nibbles we'll call *operands*. They are all still nibbles. Here's a triplet. The operand is in bold. **0001** 0001 0001 I know I'm making up a lot of rules, but I want another. If the operand is **0001** (1) that means *addition* and if it's **0010** (2) that means *subtraction*. Now you know that when I write **0001** 0001 0010 it means \"+\" 1 2 or, rearranging to the order we're familiar with, \"1+2\". We just wrote one line of a program for a computer that tells it to add two numbers together. **Key idea 2: we can make a program out of a list of numbers.** That doesn't tell us how to get an answer. In a computer, the opcode selects an operator, meaning it switches on a circuit that add two numbers, and then feeds the next two numbers into the circuit.",
"The most basic of basic programs is a light switch; it’s a simple on and off. If you add another light switch, depending on how you wire it, you can have the light react to 4 different scenarios Both switches off Both switches on One off one on The other off, the other on If you add a third switch, the number of options doubles again to 8 options. That’s binary, for every new switch, you double the options. 2-4-8-16-32-64-128... What can you do with all those options? Let’s say you now have 4 switches with their 16 possible outcomes...(all on one wall for reasons later) Add more lights? You don’t need 16 lighting options for one light, so you keep the first one as an on off. The other is positioned inside your deadbolt lock so that if you forget to turn the light off, locking your door turns it off too. But wait, what if your in the house and want to lock the door AND have the light on? Well, one switch could enable or disable the door switch. You can have it wired so that when the door is locked and the bypass switch is on, that switch turns the light on while also unlocking the safe to your gun. This is just wiring, nothing fancy. If you want some other safety measure in place, you could have a the last switch that only allows that to happen if you have it on. This way, the safe will only open if the safe switch is on, the door is locked, AND the light is on. You could have a different safe open with milkshake in it if the door is unlocked. Then another switch on the lock that turns on when it’s unlocked to push the door open, Then another on the door that pulls the tray out when that’s complete Then another that drops a straw in then shake This can go on and on given the space and mechanical skill to cook food, wash dishes etc. but there are certain things you have to initiate like flip the milkshake switch, or the laundry switch. Once you have everything on a set schedule, you can set everything up on Timer. If you have one day of the week where you do everything different, that can be another separate set of timers. Then one more timer switch that switches which set is used for one day after every 6. Now you have a fully automated house. That does everything you need for whichever day it is. That’s a computer running one program, or it can be thought of as 2 programs for the two different operations. Or you could say that each operation (dishes, milkshake) is a program. Not all that important. Remember, the timers are just on/off switches that are cycled through at a certain rate. Because a program will often execute extremely quickly, it’s not Doing anything out of order or simultaneous, it’s just fast forwarding the house of switches to super speed so that the dishes laundry and cooking seem to happen all at once. There are things that have to happen in order(milkshake making) and things that have to happen relative to one another(the timing between making a milkshake and doing laundry) and since it’s all been meticulously done in slow motion by you, speeding it up has the same effect. Computers can running each program as its own as long as it follows certain rules( the milkshakes program can run during laundry, but not before) Something that comes to mind is the computers ability to be programmed for all sorts of things when the hardware “wiring” stays the same. The connections aren’t physically changing inside the computer, only the allowable pathways. If you need a set of switches wired the way our house is, you COULD just wire it yourself with lines going everywhere and looping back, OR have a chip specially made that has all that wiring built in with only the external connections required. OR get a general chip and have it “programmed” Programming can takes all the physical connections in the chip and tells it which ones to use and which ones to not use by *possibly* having an on/off switch for each small function of the chip. Like a flash drive, the data is stored physically, so before the signal goes down a pathway, it has to go through the physical portion that we’ve turned on/off It turns on and off some pathways to match what our specialty chip would look like(or at least perform in the same way on all the inputs and outputs) I’m getting a bit out of my depth so I’ll stop there, please feel free to correct things.",
"Computers are very fast at thinking about things, but they can't think about abstract things like we do. They essentially understand two things, a yes and a no. The yes and no isn't like when you ask twenty questions and eventually it guesses right, but the yes and nos turn into a language. A certain combination of 0 and 1 will turn into a color or a shape. Humans can understand their language but it's very difficult, so we hire translators (software that converts programming languages to binary) to make the process faster. We write code for the computer in a programming language much closer to our own and we package that code up though a translator to make it legible to the computer.",
"I understand the basics the and or NAND nor logic gates. And I understand the software level stuff down to what and how an API interacts with hardware. However somewhere in between it's just magic. How programming code and machine code interact is just pure mysticism. What you need to do is learn about basic electronics and timing and power and amp circuits. This gives you an idea of how electrical signals can give you desired output. Then you scale that up a few thousand times and you have a CPU. And a CPU has an instruction set of commands or inputs and outputs. So eventually complex keystrokes on your keyboard are changed in to very long chains of 1s and 0s that turn on and off a whole long line of transistors and you get your results. So think of just one pixel on your monitor. First is that on or off. It checks with and see a 1 so on. Then it's got to do that millions of time for each pixel of each frame you see. And that's just the display, it's not even considering the mathematical computations made for the physics calculations a 3d game engine has to make. It's mind boggling how much happens, thats why it has to be magic.",
"So here’s something to remember: it’s Humans that give things meaning. Ink on paper is just that ink on paper. But when you look at it, all that shared meaning/understanding that you have with other humans makes the ink into words or sayings or images—but it’s just ink! Semiconductors and electricity are the same way. In if themselves they are meaningless—but you, the programmers, and the hardware designers all agreed upon shared meanings of things and that’s what made it seem magic. Your monitor has no idea what it’s projecting to you. None. It’s a meaningless array of lights lit up. And the lights are lit up based on otherwise meaningless changes in voltage. And those came from random bits of silicone holding charges. But because everyone assigned a meaning to every step and value, you see an image when you look at the screen! It’s very complex to get from the silicon to the screen, but it’s not magic—it’s just our ability to find meaning in things that have none. Why does this text convey any thought at all? Because we’ve all come to a shared understanding of language and text and ideas—and computers are the same way."
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9k4vs8 | How are electronics able to tell the exact battery level left in it? | Technology | explainlikeimfive | {
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"They're not. They're able to give you a guesstimate by measuring the voltage coming off the battery and interpolating between what the voltage started at and what voltage is required for the device to function. Battery%=100*(Vcurrent-Vmin)/(Vmax-Vmin) or something similar to that."
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9k70qx | Why do American and British (for one) television look so different? | American here...shows look so (for lack of a better term) blurry when I watch something on BBC and other sources from the area. | Technology | explainlikeimfive | {
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"It's simply down to different styles of editing and filming. Different cameras and settings affect how crisp the footage is and how much motion blur it has (that can also be done in editing). I've also noticed British shows tend to be more grey and American shows more colourful, likely as a result both of artistic choices in set and prop design and also colour grading (artificially altering the colours of recorded footage to be more or less vibrant, or even appear as other colours). Overall I think it's just choices by the crew of the show to have it look a certain way.",
"Another thing that has always confused me: I've watched so many British shows where the characters are saying it's night but its bright as daytime. Are our concepts of evening time different?",
"I also noticed that American shows play a lot of music throughout the episode, but the UK versions are much more quieter.",
"Brits have a different frame rate to the US In the UK, TV is broadcasted at 25 frames per second (this was called PAL) Whereas in the US, TV is at 29.97 frames per second (this was called NTSC) (PAL and NTSC are the formats of old colour TV broadcasts. The reason I refer to them here is because they were the formats that made TV localised) If you don’t know what frames per second means, here’s a quick explanation: Think of 1 whole second of a film. In the UK that second is made up of 25 different images, placed next to each other. In the US, 1 second of film will have 29.97 images to flick through. You don’t see these images jumping to the next because they move too fast for our brains to process. However if the frame rate is lower, let’s say 10 frames per second, you will be able to see most frames jump to the next depending on how much movement there is between those frames. The difference between 25 frames and 29 frames is really very subtle, but you can be sensitive to that difference. The blurriness you’re referring to might just be that you are so used to seeing 29 frames per second, that seeing 25 frames per second would come across as blurry. Source: makes films in london ELI5: The brits have less pictures in the TV. EDIT: This also works vice versa. Brits may think American TV looks blurry just because it’s filmed in a different frame rate.",
"The most obvious thing I notice in all American TV & film is the use of water on all cement surfaces to get that shiny look even under bridges and awnings. (I assume there's a cinematographic term but you know what I mean).",
"American shows are more \"polished\" and glamorous, with oftentimes better cinematography, and better groomed actors and actresses, giving an idealised, almost Hollywood-esque, synthetic feel to their shows. They avoid the themes of urban decay, poverty and the lower classes. The focus is on the wealthy classes who live in luxury suburbs or apartments (think Desperate Housewives, Sex and the City and such forth) British shows are more \"raw\", aiming for realism, the gritty, and such forth. The focus is usually on the working / lower classes (think Shameless, Skins and such forth).",
"Different interpolation and codecs for delivery. This has probably been answered, but United States and a few other places use NTSC where most European areas use PAL. NTSC uses 525 scan lines at 60Hz. PAL uses 625 scan lines at 50Hz. Scan lines are the artifacts you see when you try to videotape television. It’s pixels being drawn across the screen, a row at a time. Hz can be thought of as how many of those lines are redrawn before a frame is changed, more or less. When converting one signal to the other, scan lines either have to be removed, added, or scaled (image stretched), and the refresh rate for those lines has to be altered. This usually requires downgrading the image, in either case, to hide the artifacts the changeover inherently causes. This can sometimes make footage look blurry, noisy, or otherwise outdated on modern displays. If you want to see an example of an American movie converted from PAL (as it was the only format that still existed at the time the DVD was made), look at the DVD for “Don’t Tell Mom the Babysitter’s Dead” and compare it to DVD versions of other movies from the same year. In the intended regions, both video formats look crisp and modern. It’s in the conversion that information’s generally downgraded."
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9k9y00 | why a smartphone camera makes several flashes before taking the actual picture? | Technology | explainlikeimfive | {
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"Red eye reduction. The first flash causes people's iris to contract, making their pupils smaller so that less red light reflects back out from their retinas. That prevents the ugly red-eye effect in the picture."
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9k9znb | Why do disk based video games need to install to my console’s hard drive? | Technology | explainlikeimfive | {
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"You already answered your own question, it puts data onto your HDD (or SSD if newer consoles) because it's significantly faster than reading from optical media. That includes resources like textures and audio as well as the executable of the game. You need the disk to launch the game because otherwise you could buy a game, install it your on HDD, then sell the disc, but still be able to play the game. In other words, to prevent piracy.",
"> I understand that it helps load times Yes it does, tremendously. In addition, a lot of data on the disc will be stored in compressed formats, so when it installs to your hard drive, it uncompresses it so it can actually be used. The disk just acts as a convenient way to transport the data to your hard drive. Having the disc to launch is generally used as a copy protection method (and its a very old and tried and true method), its so you can't install the game then give or sell the disc to someone else who can do the same."
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