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a8sdho | why do batteries have a smaller carbon footprint than fossil fuels? | Technology | explainlikeimfive | {
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"Because you can generate power from Hydro-electric, Solar, Geothermal, Wind, Tidal, and Nuclear power and use that electricity to recharge the battery. Even with coal or diesel powerplants the power generated in them is much more efficient and therefore charging off of them is lower in emissions than running a combustion engine is.",
"Batteries aren't an energy source; they are a method of storing and transporting energy. It's hard to compare batteries to fossil fuels since fossil fuels are both the energy source and the energy transport mechanism."
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a8uqov | Why hasn't anybody created a new "YouTube" | Technology | explainlikeimfive | {
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"There are plenty of video streaming services - Vimeo, Streamable, Dailymotion. YouTube is simply more popular.",
"Vimeo..but its more professional artsy videos on that site..the community is not as toxic as youtube..also its more quality videos than youtube..",
"Maybe because it's not easy? Just imagine how much space you need just to store the videos. Then you need a well working site. Then a way to make money from it because it's not cheap either to begin with.... etc"
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a8v4yt | Why do many web pages seem to first load once, then disappear / realign and take another couple of seconds before they are actually done? | Technology | explainlikeimfive | {
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"Bad website design. This is something that people making websites should know about, and that is relatively easy to make not happen. But many website designers choose not to care about it when they're making websites, so they don't stop it from happening. Often it's because they store \"what the website content is\" and \"what the website looks like\" in a way that stops the computer from knowing what the website should look like until after it's already had a go at drawing the website, so it has to throw it away and try again. Other times, the website itself contains instructions (written in a language called \"JavaScript\") to change what the website content or look is after the website has been loaded, which has the same effect of making the computer have to throw its drawing away and start again with things in different places. See: New Reddit.",
"Hey there! I built websites for a living for about 7 years. There are a couple reasons this can happen, but the simplest explanation is that every website is made up of several different parts, and those parts can finish loading at different times. The main \"parts\" of a website are: * The static layout/HTML, which includes any pictures/text/layouts that are *always* on the website * The dynamic content (like blog posts, inventory on sales pages, or videos/pictures on gallery pages), which usually doesn't appear until the behavior/JS (below) is finished loading * The formatting/CSS, which takes all of the content described above and arranges it to look pretty * The behavior/JS, which allows the website to animate, load dynamic content, and perform other programmatic tasks as you interact with the site Most web browsers (Chrome, Firefox, etc.) are designed to start showing a website as soon as it has *anything* ready to show, even if there is a bunch of stuff still loading. Because of this, it is very common to see the not-fully-loaded version of a website for a second or two before everything finishes loading. When one part of a website is loaded, but the rest of the site hasn't finished loading yet, you can get some bizarre-looking results. For instance a website without CSS will often look like a boring, broken, black-and-white-and-blue page (example: [Amazon homepage with missing CSS]( URL_1 )). A lot of websites \\[wisely\\] don't start running any of their interactivity/animation code until the entire site has finished loading, which means a website that relies heavily on javascript might look funky before the initial startup code has been called (example: [Neopets before (bottom) and after (top) javascript loads]( URL_0 )). A lot of websites try to \"hide\" their partially-loaded site with \"hide everything\" code that runs as soon as it loads, then \"show everything\" code that runs once *everything* has finished loading. The problem is that sometimes, the \"hide everything\" code doesn't load/run until after you've already gotten a peek at some of the partially-loaded website. So on your end, you see: * The website starts to load, and you see the partially-loaded website * The \"hide everything\" code runs, turning the website blank momentarily * The website finishes loading while the website is hidden * The \"show everything\" code runs, and you're finally shown the finished website The most common solution to this problem is to use inline styling to make the page *start* invisible, and not become visible until after everything has fully loaded. The problem with this solution is that if the page never fully loads, or if the user has javascript disabled, the website never displays. It *is* possible to get around these issues with clever code and some inline styling. You've probably noticed that Google's homepage is remarkably consistent when loading across multiple devices and slow connections. But this is usually a low priority for web developers, who are mostly concerned with how the website looks and functions once fully loaded, across multiple devices.",
"The 'first load' of the web page is the actual load. The server generates the page, and sends it over to your browser which then displays it. Once your browser is done loading the web page it then starts executing the javascript commands defined in the \"onLoad\" attribute of the document. If a web page uses Javascript to change it's font, layout and/or styling, it will then cause things to be changed accordingly - which is what you experience as a 'second load'. As for why specific webpages do use Javascript to change their look like that - I honestly don't really know.",
"Depends on the page, but the general answer is that websites are composed of resources which download at different speeds, and so as resources finish downloading they pop into the page. This can be images bumping content around them. Css applying styles such as heights and width of elements. Or JS loading late and modifying the page elements. The most common culrpit is images since they are slow and large."
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a8xfe7 | Why does AM radio sound like crap compared to FM? | Technology | explainlikeimfive | {
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"I've seen it explained like this in the past: Radio waves are just light that you can't see. Imagine you can see this light now all of a sudden. FM gives your radio receiver information by changing the \"color\" of the light. AM gives this information by changing the \"brightness\" of the light. If you're a receiver looking at this light from across a forest, obscured by the trees, only letting a few rays of light past; it is a lot easier to see the change in color (FM) than the change in brightness (AM) This really blew up! Thanks for the kindness everyone 😊 Edit: What I said yesterday can apply to radio wave obstruction but it appears I've missed part of the story. AM and FM waves also are different in that each one has a different sized \"block\" where information can be stored. Make two separate waves with your legos. One wave should be made out of larger bricks. This wave with larger bricks is FM. Because the bricks are larger on FM you can fit more sounds into each block, giving you a better sounding noise. Hope that helps kiddo!",
"You write a code on a rubberband. AM: Your code looks like long or small vertical lines. The lengt of the line determines the message. FM: The code is a bunch of vertical lines of equal length, BUT the spacing is different. Now stretch the rubberband, eventually the AM will start to look the same, just a bunch of lines of nearly equal length OR all the smaller lines disappear. The FM is more stretched out, BUT the spacing is equally strecthed. ~~The data of AM deterorates faster than FM.~~ Edit: The data of AM does not deterorate faster, but it distorts faster. While FM does deterorate faster, it has less distortion. Also as other people mention, AM has less bandwidth compared to FM.",
"The main reason is bandwidth, which is the same reason 320kbit/s MP3s sound better than 96kbit/sec MP3s, and why typical music files sound better than phone call audio. & #x200B; FM radio channels allow more spectrum to any given station than AM radio channels (just because that's the way we parcelled out the spectrum at the time radio stations started broadcasting). & #x200B; Imagine you had to describe a painting so that someone else could recreate it. With AM, the page is really narrow, and you can only squeeze in a paragraph. But with FM, the page is nice and wide, so you get a whole page. When the painting is reconstructed, many more details will be missing from the AM reproduction.",
"The simplicity of it doesn't help. Amplitude Modulation, pretty much varies the intensity of the signal, so some of the radio waves are stronger than others. The receiver just catches this varying strength and amplifies it and that produces sound, kinda like a wireless version of a vinyl record. But because of this, any sort of electrical noise easily messes with the signal and makes it sound less nice. Also, AM radio stations only have a 20 kHz bandwidth, which makes squeezing more \"data\" into their broadcast much more difficult. While FM radio had stereo sound by 1961, AM stations were struggling to match that even by 1970. FM radio enjoys both a wider bandwidth and a modulation scheme that is less susceptible to interference.",
"AM has a much longer wavelength and “bounces” off the atmosphere, meaning it can travel very long distances but loses quality very easily due to the amount of interference it accumulates. FM signal, on the other hand, is generally picked up only where there is a direct line to the station, as its short wavelength can be blocked by walls and other solid objects. It does not “bounce” in the same way AM does. However, this also means the signal comes in very strong, so typically the quality on FM is far better even if you can only tune in within a comparatively short area close to the broadcast. Basically, AM is like a cable with really low bandwidth that can go like 60 feet, while FM is like a 5-foot HDMI you use for hooking up your Xbox. You’re not going to get great picture from the AM cable because it’s limited and loses detail due to the length, but you can stretch it throughout the house. Meanwhile, you’ll get great picture from FM but it’s short so you’ve gotta make sure the box is close to the TV. This is also the reason why AM tends to be news or public access while FM has the big music channels and local stations; general stations need to reach a wide range of people, and being lower quality isn’t as much of an issue when you’re mostly just using spoken word.",
"AM is affected a lot more by outside sources, such as lightning, where as FM cuts that out when the signal is received. Source: 8 months of hell (hopefully someone that attended this school will see this)"
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a8xisc | Why is it that live TV doesn't buffer as an internet stream does? | Technology | explainlikeimfive | {
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"* Live TV via broadcast or cable network is sent directly to you via a dedicated system that only exists to send the audio and video to you. * The internet sends all kinds of data via a web of different companies and locations. Each stream of data is broken up into different little packets that can each take a different route to your computer. Then they have to be put back together in the right order. If some get lost along the way, your computer asks them to be resent. * Also internet streams are individual connections where your computer and the server have a back and forth conversation. Broadcast TV, on the other hand is one transmission tower blasting out a signal. You TV can choose to listen to it or not, but the number of TVs trying to listen has no effect on the tower's ability to send out the signal.",
"Broadcast TV signals are sent as unidirectional data. The information travels in only one direction, from the studio, through the transmission network and then over the air. The data is sent as a continuous stream. If there's no-one watching, the transmission still continues unabated. If there's momentary interference somewhere, the transmission chain doesn't know and doesn't care and still carries on sending the next frame, then the next, then the next.... This is an example of isochronous transmission. Video over the internet is different. There's bidirectional communication involved. As an example, Youtube. Your computer (phone / tablet / whatever) asks Youtube's server to send video. The information is broken up into chunks (packets). With the reception of each packet, your computer confirms to Youtube that it has received it in an understandable and non-corrupted form, and asks for the next. When Youtube's servers get a free moment, they send the next packet - receipt at your end is acknowledged and so it continues. Should a packet be received in a corrupt or otherwise damaged condition, your PC will ask Youtube to re-send it. The way the internet works, there's no precisely defined route that the packets take to get from one place to another. They might travel through the hardware that makes up the internet in a path that resembles a geographical straight line, or maybe even go via a different country hundreds of miles away. One packet can take one route, the next a different route, the next a different route yet again. There's no defined speed that a packet can be delivered, in the same way that there's no defined route it will take to get to you. Instead, the whole concept of streaming video relies upon the fact that the packets will, on average, arrive at you much more quickly than is strictly necessary. Your PC will buffer - store a few seconds of video and audio in memory - to allow for a packet needing to be re-sent, or one arriving a little later than is necessary for smooth video replay. As the clip continues, by the time you're part-way through, sometimes your PC will have grabbed the whole of the remainder of the clip into local memory. If your connection is just on the edge of being fast enough and reliable enough, the video will mostly stream OK, but bump and stutter now and again if the buffer temporarily runs empty due to a corrupt or missing packet which needs to be re-sent. This is an example of asynchronous data transmission. Broadcast TV has no need to buffer (beyond the tiny amount required to decode an MPEG stream as the compression system operates over a number of frames), as there's no mechanism for your TV to request that a data packet, or frame of video is re-sent if it's not correctly received. Instead, you'll see MPEG errors, blocking, frame-holding and the like."
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a8xza3 | How do live football field graphics appear beneath the players? | You know when it shows the scrimmage lines or whatever right on the field? I assume the graphics are already using pan/tilt/zoom data from the cameras, since it looks a lot stabler than simply motion tracking (please correct me if I'm wrong on that), but what really baffles me is how the graphics appear "beneath" the players. Chroma key? Nope. I see teams with green colours that still pass over it. Extracting a matte from thermal imaging? Wouldn't the helmets be cooler than their bodies? What then? How? | Technology | explainlikeimfive | {
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"You had the right idea already. It is indeed chroma key. The cameras are simply good enough that they can distinguish between the green of the grass and the green in uniforms. They actually need to continually reset the chroma key as the color of the grass changes as the sun moves or when shadows show up on the field.",
"It's a step beyond chromakey and motion tracking... first they can only do this from some of the cameras. Those cameras have motion tracking mounts that are very precise. Then when they set up before the game they not only calibrate those motion tracking, they map the field... it isn't as simple as keying out green. They're keying out the exact shade of grass at that location (within some slight variation for lighting changes). That's the way it was 10 years ago. They may have built into some level of 3d tracking to even improve it further."
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a8z2q4 | What is the difference between re-chargeable batteries and standard ones, that allows for the former to be recharged? | Title | Technology | explainlikeimfive | {
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"All batteries use a chemical reaction to create the negative-to-positive electron current that powers our world. The chemical reaction that gives a standard, alkaline battery is irreversible, so once they are done they are done. Rechargable batteries use an electrical current (a charger) to reverse that negative-to-positive energy flow, that both types of batteries utilize, allowing them to be re-charged for use. Maybe that was more ELI9 or 10 but I hope I helped."
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a90lrv | - How is music pressed into a vinyl disc and then replayed with a needle? | Technology | explainlikeimfive | {
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"First let's start with recording. A band would gather in a studio and play a song, and there would be a receiver of some sort that captures the sound. So imagine something like the horn on an old phonograph, and inside there is something that vibrates when sound hits it, and makes a needle vibrate on a blank record (which may not be the same material as the vinyl you buy at the store). It literally physically cuts the soundwaves into the record. You know how seismographs, those machines they use to read earthquakes, have that needle that's drawing the vibrations on paper? It's a lot like that. To play it, it's nearly just reversing the process. In recording we had a horn funneling sound down to a diaphragm that moved a needle. To play it, we put the needle to the record and since it has grooves in it now, it vibrates the diaphragm and the horn helps make it a bit louder. In later times, the needle vibrates an electromagnetic mechanism which made an electric signal that could be amplified and played through normal speakers. But if we want to make copies of our recording record, how do we do it? First you make negatives of it by pressing some moldable material against it. Like how when you push your finger onto Silly Putty, it leaves an imprint of your fingerprint. But the negatives are the *opposite* of the final product we need, It's the literal opposite of the original record. So with the soft negatives you make harder positives by making a negative of the negative. Then once more to make a *final* negative that is a lot harder than that \"silly putty\" we used to make our first copies, and these final negatives will be pressed against blank records to \"leave their fingerprint\" on them. They go through all this to keep the original recording as unaltered as possible, whether for archival purposes or in case they need to make more molds if the first set wears out, as making copies from the original preserves more of the recording than copies of copies of copies of copies of copies."
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a91ndx | why aren’t commercial cargo shipping vessels using nuclear power? The little I’ve read says because of cost but if they have such a long life won’t the eventually pay for themselves? | With the recent talks of shipping lanes opening in the arctic and some Arctic’s icebreakers already using nuclear power, wouldn’t it be smart to only allow/ pusher for greener options to use these possible shipping lanes. Would it reduce greenhouse gases? | Technology | explainlikeimfive | {
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"In that regard it's not a bad idea in my opinion, but there are more costs than just building the reactors, you also have to pay to train the operators and then pay them to operate. And trust me when I say that learning all that stuff is not an easy job. So I'd say at this point it's a bit of a gamble. Plus the military reactor design is classified so they'd have to pay a bunch of engineers to come up with a design. It definitely could be done, we're just not there yet."
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a9232t | Why do some state government healthcare websites shut down every night "for scheduled maintenance" - what maintenance are they doing for 8 hours every single night that prevents users from logging on to see their account? | Technology | explainlikeimfive | {
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"Could be database backups that they don't want new data being written into while copying over to the backup files because that can lead to issues.",
"If the system is connected to their mainframe, it would be due to the fact that the mainframe goes offline (as far as interactive processes are concerned) nightly for batch job processing. (Not that it actually takes that long to run them, but if the schedule hasn’t broken since the 80s why fix it now?"
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a953i7 | During the film editing process, how does a camera know exactly what is behind someone wearing a green morph suit? | Technology | explainlikeimfive | {
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"Usually a shot called a \"plate shot\" is used. Sometimes it's as simple as removing all the actors, and filming the background for a second or two. This gives the visual effect company enough information to remove any green and replace that hole with the background. Other times it may be several stills photographs stitched together. Compositing software is used to remove any unwanted element - green screen, morph suits, stunt wires, etc and the plate shots provide the background to replace it. In some scenes the background can also be completely computer generated.",
"It doesn't. Two separate shots are made with the camera in the same place and layered on top of each other. One with the guy in the green suit and one without the guy. That way when the green is made invisible you have a background to put behind it. It can get considerably more complicated than this, especially with moving shots, but this is the basic principle.",
"when you're using these things, its actually the computer doing the hard work. You have a program that tells theediting program to pretend that everything with this one color is invisible. That way you can create layered images - putting one thing on top of another, separately recorded thing. then you can paste whatever you like onto the suit. the two things will work by themselves, and the editing makes it appear as if it was one single clip."
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a95ge0 | How does machine learning work? And why are people saying its dangerous? | Technology | explainlikeimfive | {
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"Facebook can tell whether you're gay based on a few 'likes,' study says URL_0 Now suppose you live in a country where being gay is against the law.",
"Machine learning takes a bunch of random inputs: height, weight, income, education, race, car you drive, etc and an output. Say, likelihood you have or will commit a crime. It’s trained on a large dataset, and makes its own correlations, much like the movie Minority Report. If the correlations are mathematically valid, it assumes correctness. So, based on historical crime patterns, race will correlate highly, and be a predictor of crime. *But*, what if the dataset is misleading. That income, education and other factors influenced the propensity for crime, and those factors correlated to race because of discrimination. Or even more worryingly, what if discrimination by the police had them letting white criminals off with a warning, and people of color got prosecuted. That would bias the machine learning. And if they got more scrutiny in the future, it would look like the model was correct as it identified criminals. A self-reinforcing spiral. So, what if you remove race as an input. Then other inputs, like neighborhood, income, etc correlate to it and effectively add it back in.",
"Machine learning is the process of developing a computer program that can perform a task without explicitly telling the program how to do it. You tell it what you want it to do and give it a way to tell if it has succeeded and let the program figure out how to get there. For example, let's say you want to develop a computer vision algorithm to tell humans and cars apart. You give the program a very basic set of skills like how to access the pictures but you don't tell it how to tell the two things apart. Then you give it a bunch of examples of humans and cars. The program will then learn what is in the car pictures that is unique from the pictures of people. This process takes a while and at first the program will be really bad at making the distinction. But, over time, the program changes and gets better at its job until eventually you have an algorithm that can tell humans and cars apart very well but no one can tell you exactly what it is doing to make that determination. I don't know about people saying it's dangerous other than, since we can't know exactly how the program works, we can't know what the program will do if presented with unexpected data. Take the death of the pedestrian in the Uber self-driving testing in Arizona earlier this year. The person was pushing a bicycle along the street and, at first, the car got confused because it saw a person but also saw wheels and wasn't 100% sure what it was. It eventually figured it out, but it was too late. (There were other things going on in that crash but this was one of them.) Here are a couple of really good videos that go into more depth: URL_1 URL_0"
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a96bwk | How did they manage to land people on the Moon and return to Earth with computers that were not even as powerful as mobile phones? | Technology | explainlikeimfive | {
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"The trajectories were all calculated beforehand. There are still plenty of variables in space, but wind speed, weather, etc don’t apply like they do for aircraft. It really comes down to geometry, which can be done without much processing power.",
"> Seems impossible, given that the modern aircraft (even absolute small ones) have hundreds of intruments, advanced computerized systems and so on. Remember, we had people flying all over the world well before there was even a single computer inside an airplane."
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a977dd | why is there a need for both "ip" and "mac" addressees to exist? | edit: thanks for the help guys | Technology | explainlikeimfive | {
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"Mac is who you are. IP is where you are. It’s same reason you have both a social security number and an address.",
"My very basic understanding is that MAC is like a devices serial number. Where IP can be reassigned. It's like you're living in a house. The mac is you and the ip address is your house's adress. If you move, your mac stays the same even though your IP address may change....... I may be totally wrong.",
"There isn't a \"need\" in the sense that we couldn't have computer networks without two forms of addressing. But the current model is a layered model where what happens at one layer doesn't care about anything happening at another layer. This allows people to design protocols, services, and applications without worrying about what's happening below or above the area they need to worry about. A result of this is you have things like multiple forms of addressing at different layers. The MAC layer doesn't care about the IP layer and vice versa, but each needs a form of addressing.",
"Mac addresses came first, back when computer networking was almost entirely a local-area thing. They are hard-coded into the hardware and in no particular order. There is no way to tell from mac addresses whether two computers are on the same section of a network. That's fine when you only have a few computers. But as you get more and more computers, you start needing to segment your network because the shared bus* gets crowded and congested. So, they designed an IP addressing scheme, which was hierarchical and configured by software. The first part of the address defined which network segment you were on and the last bit pointed to your specific computer. There's also the issue of encapsulation. Computer networking relies on independent layers being able to do their job without any assistance from the layers above, or need to meddle with the layers below. The mac address is used by one layer, and the ip address is used by the layer above that. Think of it like hiring a taxi; you tell the driver where you want to end up and they figure out how to get there. Finally, ip addresses are often configured remotely, by a central server. So each computer needs some OTHER unique identifier so they know the server message of 'this is your ip address' is meant for that computer and not some other one on the same network. Long ago, it was common to shutdown a computers when it wasn't in use, so at the start of the work day, every computer is going to be powering up and asking for an ip address at around the same time. \\* the shared bus is a space where all the communications flow through. Often it was just a network cable that computers were connected to in some fashion."
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a99q9n | Why do modern ultra-high-def TVs make some high-quality productions look like home video? | I’ve been noticing this for a while. When watching movies or shows on modern HD TVs, the production quality suddenly feels cheap. Top productions have the feel of high-quality home video or Asian soap opera. What would cause this? | Technology | explainlikeimfive | {
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"The colloquial term is 'the Soap Opera effect'. Higher end TVs basically insert fake frames to reduce motion blur, causing 24fps video to look like 30/60fps. It causes that weird smooth look. If you wanna do further research, lookup MC/ME (motion estimation/motion compensation).",
"There's a couple of issues at play. First of all is the soap opera effect. Many TVs use motion interpolation tricks to smooth out the juddering that can occur from low frame rate video. One side effect is that motion suddenly feels artificially clear (which is ironic considering that higher clarity/higher framerate material actually more closely approximates what you'd see in real life rather than the motion blur we're used to from 24fps movies). It's called the soap opera effect because soap operas tended to shoot direct to digital video rather than film in order to cut costs, bypassing that inherent cinematic feel that comes from the motion blur present on film. Tangentially related to this is the enhanced detail you are able to see. This makes all the flaws in makeup, set pieces, special effects, etc. glaringly obvious. Higher resolution, like 4k video vs an old 480p tv feed, means that a set-piece that was meant to look like a worn down brick wall and was convincing at lower resolutions, now actually looks like a cheap painted piece of cardboard. But the enhanced motion clarity also means all the stuff that normally looks smeared in moving scenes is sharper as well. Props and makeup are no longed blurred during fast moving scenes, and now are clearly identifiable as being cheap approximations. Our brains are really good at filling in the blanks. So when detail is missing, but the obvious omissions are cleverly masked, we perceive something as \"real,\" even if it is a cheap set piece that upon close inspection would be obviously fake. However, our brains are also great at pattern recognition. If something is visibly wrong we will pick it out right away. So as video becomes sharper our brains are more easily able to detect everything that is wrong with the scene, and it makes it feel like we are watching a cheap production on stage or a home video shot with a handycam.",
"If you’re referring to what people are calling the “soap opera effect” than excuse what I’m going to add. There are some productions that look terrible in Hi-Def. One of my favorite movies comes to mind. The movie “Tombstone” is really negatively effected by hi-def. I probably watched the movie 50+ times before seeing a blu-Ray version of the movie on a good TV. In the ultra high def version of the movie, the props and set are obvious props and set. It makes the movie look like a high school play. It can be really off putting. This likely happens because the movie is now being shown in a way not intended by the film maker. They simply didn’t do a good enough job on the set."
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a9b2eg | how do computers know how to do math? | I understand someone programs it but how do you teach a piece of software to do math? | Technology | explainlikeimfive | {
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"Logic gates. Basically you set up a series of switches that depending on an input will have one output. The basic logic gates are AND, OR, XOR, and NOT. They are all in binary and with the exception of NOT take two inputs. An AND gate outputs 1 if both of the inputs are the 1. So it will return 1 if you input 1,1 and return 0 if you input 1,0 0,0 or 0,1. Or gates will return 1 if any of the values are 1. XOR gates or Exclusive Or will return 1 only if both the values are different. Finally not only takes a single input and it will just invert it, so an input of 1 will return 0 and an input of 0 will return 1. You can then put these logic gates together to create more advanced gates like the NaND, NoR, and XNOR which are just the AND, OR, and XOR gates with an inverter on the end giving the opposite output that you would get from their more basic counterparts. From there we can continue to add gates together to get more advanced systems. By adding a XOR gate and an AND gate together we can get whats called a half adder, its its basically a very basic calculator. You have the Xor gate handle the \"ones\" place and the \"AND\" gate governs the \"tens\" place. so if our input is 1,1 our output would be 10 which in binary is 2. 1,0 and 0,1 will output 01 which is of course 1 with 0,0 outputting 00. We have basically created a very simple calculator that can count up to 2. Finally we get to the full adder. A full adder is basically 2 half adders and a or gate. They have 3 inputs instead of 2 and have 2 outputs. They can output a \"ones\" and a \"tens\" place as well as output a carry over value, and that extra input is for a carry over value. This means that you can basically stack them up with the carry over output of one connected to the carry over input of another and add bigger numbers. By combining full adders together you can create a really basic calculator that can add numbers bigger than 1 bit. From there things get more complicated as we move to division, multiplications and other operations, but thats the basic idea. Logic gates that when combined together in specific ways will give an output that matches what the mathematical output would be.",
"You don't need to teach software how to do math, because math is implemented at a hardware level. There's a piece of circuitry in a CPU called the ALU which does, well, arithmetic operations. Adding, subtracting, etc.",
"Math operations are done in a part of the CPU called the Arithmetic Logic Unit (ALU), which handles arithmetic and logical operations: adding, subtracting, bitwise and-ing, bitwise or-ing. Everything is done with hardware, so it's all electrical signals. Since it is all electrical signals, the math is done in binary. So, the ALU will take in your two numbers, for example 5 and 3, and the CPU tells the ALU that it should add them. The ALU adds them using binary addition. The final product is the binary representation of 8. Multiplication and division are more complicated from the hardware perspective, ~~and is not done in the ALU.~~ A more thorough description can be found at URL_0"
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a9bf6g | What defines a font? I.e., can one deduce what X, Y & Z look like based off of A-V? | Technology | explainlikeimfive | {
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"A font is a uniform form of letter. It is based on calligraphy, an art form. The only thing that makes a font look a specific way is they look alike and since it's based on stylising something you can guess but there isn't a formula, just as there is not a set formula for art. That is how I have come to understand it."
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a9bymq | How do lights change colors? | Technology | explainlikeimfive | {
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"Lights that change collors will actually have three small lights inside them which can turn on at various brightness. The lights inside will be a red, green, and blue. These will turn on at various brightnesses to cause different colors to appear. Red and blue for purple is the obvious one, and the lights work together to create any other color.",
"I'm assuming you mean RGB lights, like LifX or Hue bulbs and strips. Each of the points of light is actually a set of tiny LEDs, like pixels on your TV/Computer, that are composed of sub-pixels in red, green, and blue. By dimming different colors and diffusing the light outward, the light mixes into the colors you want to display. Turning the Red all the way on, and the Green about halfway makes the light orange. If you know the RGB values for the color you want, you can make the light practically any color you want."
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a9bzep | 5: how or why do wireless devices catch viruses? | Technology | explainlikeimfive | {
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"The same way that conventional electronic devices do, wireless is just another way of connecting to the internet it doesn't provide any protection against viruses if anything because a wireless network is easier to hack you are more vulnerable.",
"Wireless devices can receive malicious software because of the ways in which the wireless signals can be intercepted as your device talks to something else. For example (assuming no crypto) I can intercept or snoop on your laptop talking to your home WiFi router from a nearby device. This provide me the opportunity to steal information. Credentials, or provide you bad responses. Using these, malicious code can be given to you much in the same way as wired devices. RF provides a lot of other possibilities for attacking but this is the basic concept."
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a9d3id | how 60fps works on a 144Hz monitor | According to quick calculations in my head, for a 144Hz monitor to display 60 fps, each frame would have to run for 2.4 "cycles" of the monitor, which to my understanding wouldn't be possible (only changes on whole digit "cycles", 144 of which happen per second) Do I have some kind of fundamental misunderstanding of this?!? | Technology | explainlikeimfive | {
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"They are unrelated. The screen is always technically flickering at 144hz no matter what the FPS is. The FPS is from your computer only",
"The fps is the limiting factor. If the GPU pushes a new image 60 times per second, but the monitor is refreshing 144, it will refresh the screen with the same image. When it GPU sends a new one, the monitor will desplay that next refresh, no matter where in the time between monitor refresh the GPU sends it."
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a9d8ed | Why did the ".us" domain never catch on compared to other countries' domains? | Technology | explainlikeimfive | {
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"The Internet was invented by the US as a joint project with universities and the US military, and while the World Wide Web (www.) address system was developed in the UK most of the early sites cataloged in the system were based in the US. The early internet also did not really want nation based ID and instead focused on category type domains such as commercial (.com), Educational (.edu), Governmental (.gov), Organization (.org) and the like. The use of national domains is a relatively new thing and the other method was so established within the US that there is no legitimate business pressure to switch things up. Meanwhile in other countries there is a reason to try and differentiate your site from those used by Americans either due to the laws of your country or due to the type of people you are wanting to attract.",
".com is viewed as more prestigious and was already in use by most US sites, and most commercial businesses and online businesses. .com was essentially .us already. .US holds no interest to companies in the US, and would be viewed as weird and cheap, since .com is essentially the defacto .us and used for US-based sites anyways. It may be a better question to ask the opposite: Why did things like the .uk or .nl become more common? Well... because .com catered to the US based audience, not to the UK or Dutch audience! Especially in the earlier days of the internet, when geolocating was uncommon (now a site can automatically determine your location and route you to a local site), but back then, for example if you wanted a UK version of the site, you go to the .com, and go through a, often unintuitive method on the site, to manually change your country to UK to get the right local site.",
".us actually predates .com (only by a month), but .us had more restrictions in its use compared to .com. You couldn't get 2nd level domains (ie URL_0 ), instead you'd need to get URL_1 . This restriction was removed in 2002, but by then .com had won."
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a9dmrd | Why does a device retain it's setting if the batteries are replaced quickly? | I have an older digital camera. If I swap the batteries in a few seconds the clock and other settings remain. Why? | Technology | explainlikeimfive | {
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"This can be any one of several different reasons: 1) If you lose those settings if you take more than 15 seconds to switch, most likely there's charge left in capacitors distributed throughout the camera and it's this charge that's used to keep the clock ticking for a few seconds. 2) If the clock will run longer than that there's likely a small battery somewhere in your camera that does nothing but run the clock and maybe the on/off button. This is common in PCs and gameboy cartridges. 3) If removing the battery for an hour makes the clock about an hour late, it along with your other settings are stored in non-volatile memory."
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a9f80s | Why aren't decentralized "Internets" popular? | Technology | explainlikeimfive | {
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"They have a lot of problems. For example you would need some path to whatever physical server you want to reach and that generally means you would need an unbroken chain of WiFi routers. That simply doesn't exist in most cases; perhaps within a dense city but there is a lot you want to access elsewhere. Another problem is speed. Depending on the physical locations of the participants a lot of traffic may pass through one node, and inevitably there will be a lot of nodes to traverse. That means it will be slow, completely unsuitable for significant amounts of data. And finally you have the issue of private users changing the network topology without consulting anyone or due care. Someone may note their node is dirt slow and overheating so they turn it off... oops, that just cut off a critical connection between parts of the collective network, nothing works anymore. Who is accountable or going to fix it? Nobody. All those problems mean it isn't a viable solution for internet as we know it."
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a9g16p | Why does auto correct often change what you're actually trying to say, but when you make simple mistakes, like 'tge' instead of 'the', it often doesn't fix it? | Technology | explainlikeimfive | {
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"Most auto correct features \"learn\". Because small fuckups on everyday words happen quite often, after a while the auto correct assumes that is how you want to spell it, because it may be a slang or dialect word, the program doesn't know. Errors on lesser used words tend to be fixed, because you haven't made that error that often. That said, lots of auto corrects have the ability to turn off the \"learning\" feature.",
"They said, that auto-correct has ability to \"learn\". But really, in most cases it doesnt. Its easy to test thru the time: you could correct the same words every day or the auto correct can correct you in wrong way every day (so you correct it), but it will not \"learn\" from the corrections. Not at all, even after months of use. So, I think that auto correct just use some pre-filled correction list from some server or even fixed list inside of the keyboard app. Who know when your mistakes will get to the list, so it will start to correct the mistakes... I think, at the moment, the \"learning\" is mostly marketing feature. Hope that after several years, new versions will actually learn something and help peoples.",
"I think there's a bit of dictionary look-up happening that work s lot better when you at least spell the beginning of the word right as well."
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a9i2ci | How does a Turbofan differ from a Turbojet? | I’ve heard that Turbofans are much more efficient, and powerful compared to a turbojet which is why airliners use them, if this is true, why does something like an F-18 or even the F-35 use a turbojet? | Technology | explainlikeimfive | {
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"Let's clear up some confusion: F/A-18s, F-35s, F-22s, F-15s, etc all use turbofan engines. Turbojet engines haven't been used in fighters for quite some time because they're less efficient. Turbofans are essentially turbojets that are placed into yet another tube, with the turbojet part being the \"core\" and the space around the core being the bypass / bypass flow. In front of the the core, attached to generally the same shaft that powers the stage 1 (front) compressor disks, is a fan. Air from this fan flows both into the core, and the bypass. For the core, this just provides a minor boost in air flow, but a lot of the fan's work goes into accelerating the air into the bypass flow. --- Now here's where the efficiency aspect comes in: Thrust is generated by a change in momentum. Momentum = mass * velocity. However, increasing the velocity of something requires exponentially (or quadratically; sue me semantics freaks) more energy to achieve. So what this means, is that the most energy efficient way to generate thrust is to move a **lot** of air, but to only move it slightly faster than it was already moving. This is how commercial airliner engines are efficient; they have giant intakes / fans that are designed to move a massive amount of air, but to only move it at subsonic speeds (slower than the speed of sound). The more air that passes through the bypass, rather than the core, the higher the engine's \"bypass ratio\" is. A bypass ratio of 1.0 means an equal amount of air flows through the core as the bypass. Commercial airliners have BPRs of up to around 9.0 (9x as much air flows through the bypass as core), although some engines can go even higher. Most fighter jet turbofans have BPRs of around 0.2 to 0.6. --- But here's the thing; if you're trying to go faster than the speed of sound (supersonic), trying to propel yourself with subsonic air won't work. If you're ejecting air that's slower than the surrounding air, you're generating negative thrust; you're generating drag. To create supersonic thrust, a convergent-divergent is typically used, as while this doesn't generate thrust, it can convert high-mass (high density), low-velocity thrust into low-mass (low density), high-velocity thrust, including making exhaust gases go supersonic. As a side note, this process also results in the exhaust gases themselves getting cooler. It is possible to make a supersonic jet that has a high bypass ratio, or to even have a supersonic jet powered by an electric compressor / fan (using a convergent-divergent nozzle), but the issue is that compressing and slowing that incoming supersonic air (into high pressure subsonic air, which you can then accelerate with a fan), comes at a cost. Compressing air releases heat, which is real, usable energy being lost, and if you try to decelerate / compress too much air, you can run into the very real issue of your fan and compressor getting so hot that it violently breaks. What supersonic aircraft do instead is they burn fuel. Burning fuel generates heat, but it generates it downstream of the compressor and fan. The turbine stages (which capture kinetic energy to spin the compressor and fan stages) do need to withstand immense heat, but there's generally fewer turbine blisks (disks with blades on the edges) than compressor blisks, plus they can be made to be a little less aerodynamic, etc. Burning fuel also causes liquids to turn into gases, which causes a massive increase in pressure. By creating all this heat and pressure, you provide that convergent-divergent nozzle with a lot more to work with when it comes to expand and cool that gas in exchange for increased flow velocity. You can also inject extra fuel to the exhaust coming from the turbine (in a turbofan or a turbojet) and burn even more of the oxygen (some of which will get through the combustion chamber and turbine without reacting with fuel). This is called using afterburner or 'reheat'. Older engines also even used to inject water (plus things like methanol) into their engines, both to cool critical engine components and to also generate that liquid-to-gas expansion / boost in pressure. This is where the term \"wet thrust\" came from (which today refers to the thrust generated with afterburner engaged). --- Lastly - why do supersonic jets use turbofans and not turbojets then? Because jets spend most of their time at subsonic speeds; flying at supersonic speeds requires much more thrust; usually afterburner. Afterburners usually consumer about 2-3x as much fuel per unit of thrust, but they also generate more thrust (meaning even more fuel consumption), plus most jets can cruise at decent subsonic speeds at much less than their maximum dry (non-afterburning) thrust level. Something like an F-35 might only burn 5,000lb / 2,270kg of fuel per hour when cruising at Mach 0.75, but at max afterburner it'll be burning 86,000lb / 39,000kg of fuel per hour. Most fighter jets only carry enough internal fuel to fly a max of about 10 minutes in afterburner. A handful of jets like the F-22 can generate so much dry thrust (and have so little drag) that they can fly at supersonic speeds without using afterburner, but again they're generally using their max dry thrust (and maybe some afterburning to accelerate to a decent speed first), so they can be burning 2-3x as much fuel as if they just stayed at Mach 0.8, etc. Bypass flow in turbofans is also useful because it provides cooling to the engine core, plus you can fit radiators / heat exchangers in the bypass flow, allowing you to cool things like radars using liquid coolant loops. Turbojet engines are still used in some things like cruise missiles, but even then it's not because they're superior, but because a turbojet has fewer parts. Some small (cruise missile, etc) turbojet engines don't even use axial flow (where the engine is essentially tube); instead they work like water pumps, with a compressor disk that uses centrifugal forces to push air to the edge of a disk, where it then pass around to the back, gets mixed with fuel burned, etc; all just because machining some ridges onto a disk is easier than precision-milling a bunch of blades, etc."
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a9k2ux | What exactly is Discogs for/how does it work? | Technology | explainlikeimfive | {
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"text": [
"It’s a database that allows users to archive all the recorded music of a particular artist in detail. Their discography. It’s an excellent reference site for music nerds. Users obsess over how many test pressings a record had, or find out how many red Van Halen Diver Down 8 tracks were made. You can also buy and sell records there, as well as add reviews, artwork and information so it’s kinda half Ebay half Wikipedia. Example: you search for Prince. What comes up is every single record Prince made - his 12” LPs, 7” eps, promo records, CDs, Cassettes listed by release date."
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a9k9r8 | How does the sound of your phone transfer through headphones? | Technology | explainlikeimfive | {
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"text": [
"The headphones contain speakers like the phone does, a flexible diaphragm which is caused to vibrate with an electromagnet to make the air vibrate. The wire connecting them to the phone conveys the electricity to actuate the electromagnet."
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a9knzm | Why is it that we are unable to take good photos of the moon using a cellphone camera? | Technology | explainlikeimfive | {
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"text": [
"It's exposing for an average of the frame, which is very dark, so the moon which is bright overexposes to white. If you have an exposure slider you can drop it way negative and potentially expose for the moon correctly. Or get a zoom so you can make the moon more than 50% of the frame so it exposes correctly."
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a9p4d7 | How data packets work? | Technology | explainlikeimfive | {
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"A packet is just the general name for a chunk of data, how it's configured is different for each protocol For communication over Ethernet it works a lot like an IRL letter where there's a header that says who it's from and where it's going. If you want to send a 15kB picture then it'll take about 10 packets since Ethernet packets are restricted to 1500 bytes so the first packet will arrive labeled as Lena.Jpg packet 1 of 10, the next is 2 of 10, and so on. When you've gotten all the packets your computer will concatenate (smush together) the data from all the packets and then stores or shows you the completed image. For basic point to point serial over RS-232 a packet is a single byte. There's a Byte Start signal and a Byte end signal with no real headers.",
"A “packet” in just a string of 1’s and 0’s (bits or BInary digiTS) or “yes’s” and “no’s”. A string of 8 bits is called a byte. You can represent any character (letter or number) with 1 byte. For example, the number 3 is represented in binary as “000000011”. Assuming you don’t want to learn how to translate binary, I will skip to the data transfer part. Let’s say we have a cable that has a transfer speed of 1 Kbps (Kilo-bit per second, pretty slow). That means that every second, 1,000 bits or 1,000/8 bytes transfer across that wire. (There are some handshake bits and error detection bits, but these aren’t really critical to the story). These bits are flying through this wire (the bits are signals by voltage or light if it is a fiber optic cable). Ok, finally to the packet question. To make any sense of these bits, the are stored in a packet. However, these packets have a certain size that we can max out. I can’t remember off the top of my head but I think it is like 1500 bits. Unfortunately, your picture is way over this size. So these pictures are segmented into parts. On these packets, there is a certain amount of overhead data, this data consists of source/destination IP/MAC addresses and segment number or order. This overhead is pretty generic so every packet has these “excess bits”. Overall, a packet is just a series of bits. A picture consists of many packets. And these packets are stitched together at the destination. A side note: IBM designed a protocol to send jumbo frames (packets) across the internet. Basically, you can send more data with less overhead. Any questions? I would love to *try* to answer them! If I missed anything, let me know!"
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a9pc90 | How do active noise cancelling headphones work? | As in the headphones with mics in them that supposedly counteract the outside noise depending on what it is? I mean they can't just play silence? I'm so confused... | Technology | explainlikeimfive | {
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"text": [
"A micro phone picks up the average ( selected range) sound and produces the opposite sound (one sound wave cancelling out the other) in the ear thereby cancelling the two out. (Edit for thick thumbs)"
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a9pxti | Difference between Excel Add-in and COM Add-in? | There's an Add-in category dropdown in Excel. There are other options, but I'm interested in Excel Add-in and COM Add-in. Aren't they both Excel add-ins? | Technology | explainlikeimfive | {
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"text": [
"They are both Add-Ins, but the integration/development method is different. Microsoft evolved the add-in and extension frameworks over time. COM (Common Object Model) was notoriously difficult to work with and an unstable COM add-in could crash the whole application. They could also be used as a malware mechanism and were generally not secure or easy to manage for sysadmins. The newer frameworks use more modern SDKs (C#, .NET etc). These are easier to develop and run in threads isolated from the core application. They are also easier to deploy and manage in Enterprise environments."
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a9r14p | How do phone/computer chargers work? | Technology | explainlikeimfive | {
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"Without more explanation of what you want to understand I'll explain very simply. Your phone and computer have batteries that need to be charged. They need direct current input at a specific voltage. The charger takes the alternating current coming out of the wall at either 120 or 240 volts and converts it to direct current at the desired voltage.",
"You have 50 or 60hz AC coming in, it goes through a full bridge rectifier to convert it into high voltage DC. Now there's a big capacitor to store that charge. Next some transistors chop that high voltage DC up into high frequency AC pulses, which goes through a transformer to convert it into low voltage AC. This is then rectified and filtered again to get the DC voltage that the phone or computer uses. You could technically skip the initial rectifier and switching, but then you'd need a much bigger transformer and filtering components, because you'd have to smooth out several milliseconds instead of micro or nanoseconds. As for charging the battery, there's a circuit that limits the voltage and current going into the battery, so that it doesn't overheat(can cause battery fires) or get overcharged(can cause metal to deposit in parts of the battery's internals that are supposed to be non-conductive)."
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a9ru2d | How does Bluetooth work? | We see and use Bluetooth on our devices all the time. We all know that if we press the device we want to connect to on the Bluetooth page from our devices we can hear or watch whatever we want on different devices, but I can not even begin to understand how it works. | Technology | explainlikeimfive | {
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"How deep of an explanation do you want? At its core, Bluetooth is similar to any other wireless data communication standard like wifi or cellular data. It sends data encoded into a radio wave in the 2.4 Ghz range. Bluetooth has multiple profiles that allows it to send all kinds of data from audio to mouse and keyboard controls. New profiles can be added to newer versions of the protocol. When you put a device into pairing mode it starts announcing to every other device around it that it is looking to pair. Then, on the receiving device it listens for this announcement and allows you to pair the two."
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a9tw5f | When movies were projected on screen with film, the screen was black 50% of the time and our brains filled in the gaps to create motion. Do modern digital projectors work in the same way? Or how is the magic achieved? | Technology | explainlikeimfive | {
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"Old fashioned film projectors used a flashing light or a blinking shutter to briefly project a still image onto a screen, then blanks the screen to enable the film to rotate to the new image. Modern screens use solid-state electronics, which are capable of changing each pixel almost instantaneously. The pixels are updated in rows, and then vertically. There is no intermediary blank period",
"So, most cinema projectors use DMDs (Digital Micromirror Devices) from Texas Instruments ([ URL_0 ]( URL_0 )) basically tiny mirrors per-pixel that are binary, either 'off' (directing light towards the screen) or 'on' (directing light into baffles that absorb light). The tiny mirrors are moved off/on rapidly (called duty-cycle, or Pulse Width Modulation) to create different brightness-es. In single chip projectors, color is then created by way of a rotating colour filter, or with large projectors, 3 chips are used simultaneously to create a colour image (one for each of red, green, and blue). Cinema projectors also use frames, and there are gaps between those frames (called 'dark time' in our industry). Generally, projectors are running at a multiple of the movie frame rate. In the case of typical 24 fps films, this is usually 120 or 144 fps, repeating each frame many times. In the film-projector days, this was double or triple flashing the image, but now it's much more typically 5 or 6 flashes. (note that this allows 3D presentations to show one frame to each eye 3 times). Now dark-time for digital cinema presentations is much less than it was for film projectors, since there is no need to have the screen go dark while the film moves in the gate. This has the added value of allowing more efficient use of the bulbs, since we don't have to 'waste' half of our light during a dark period. Note that unlike 2D presentations, since in 3D presentations we show each eye's frame sequentially, we again have that 50% dark time like we did in the film days. (one of the reasons 3D presentations tend to not be as bright). The above is true for cinema projectors made by Christie Digital, NEC, and Barco. For Sony projectors (the only company that makes a cinema compatible projector not based on DMDs) the technology is different, and is based on LCoS (Liquid Crystal on Silicon). Alot of what I said is not true for those cinemas, but Sony cinema projectors are a quickly dropping minority in the industry. Source - am a motion picture technology engineer. edit: punctuation",
"Yes, that is still essentially how it works, although it isn't necessarily a 50 black screen gap. It still based on fooling the brain because our brains normally fill in gaps in information anyway. Essentially your senses don't tell you as much as you think they do, but your brains are very, VERY good at filling in the gaps with guesswork. Optical illusions as well as things like television exploit this."
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a9ubfp | SSH certificates | I work in the web dev industry but rarely use them so don’t have a good understanding when they’re brought up in tutorials or conversation. Could any ELI5 SSH certificates and how they work for the web world? | Technology | explainlikeimfive | {
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"A certificate is used to verify that you are who you claim to be. Basically like a password, but a certificate is more like a big document that is too big to remember. Certificates can be handy for SSH as an alternative to passwords because * Passwords aren't very secure * Certificates are stored as files, which means you can use the filesystem to protect them * Easily used by multiple different programs The reason why certificates are so secure is that they use mathematics. Imagine that you wanted me to prove who I am at a Christmas party. After all, I could be an imposter. Having a password is one way. But that means I have to tell you my password, and someone might be listening in on our conversation. Also, that means you have to know my password before hand, and either of us might lose the password or accidently share it. But another way to verify who I am is for me to bake a cake. I make a wicked black forrest cake and you know exactly what it tastes like. Sure, other people can make cakes. But they can't make this one quite like I can. The great part about this verification method is that if anyone else gets a hold of my cake, they can't figure out the recipe. You can't \"uncook\" a cake. Even if you have an idea of the ingredients I used, you don't know the exact method. It's easy for me to make the cake, but impossible for someone else to reverse the process.",
"There are 2 parts to an SSL certificate: a public key, which can be shared with anyone, and a private key, which is kept secret by the owner: * Encryption - The public key is a number used to encode messages such that only someone with the private key can decrypt them. * Identification - The private key is a related number that can \"sign\" a message in such a way that anyone holding the public key can verify that it was created/signed by the owner. * Authenticity - The \"signed\" message cannot be modified by someone who doesn't hold the secret key without being detected. * Due to the mathematics behind them, it's very difficult to discover the secret number from the public key by brute force. These are very convenient properties, but they are still limited for general use. A public key is just a number. It doesn't really mean anything, apart from being useful to encrypt messages that one person can read. As long as you are given that number directly from the person you want to share a secret with, then you're fine, but that's not how the Internet works. Instead, you are often given the public key when you first receive and email or connect to a website, and then use that to communicate securely. But how do you know that it really comes from Google, and not someone who intercepted the message and substituted their own magic number? How do you know you can *trust* the peer, sight unseen? That's where the \"Public Key Infrastructure\" or PKI come in. The PKI system is used to create trust by vouching for the public key, tying the number to an entity that has registered it. There are a number of systems for PKI, but the one that the Internet mostly relies is a network of \"certificate authorities\" (CA). So, what's a certificate? A certificate is a file or record, composed of the following pieces of information: * The public key. * Information about the person who holds the private key (name, location). * Information about the \"issuer\" of the certificate, if any. * The algorithm necessary to encrypt messages. * Creation date, expiration date, and revocation information. * Other details, such as website(s), usage limits, extensions, etc. The simplest certificate is simply one generated by the owner of the private key. He can \"self-sign\" a certificate as its issuer, so that it can't be tampered with. But the only thing you really know is that (a) it was signed by someone holding the private key and (b) the indicated information hasn't been modified by someone else. You can securely exchange messages with him, but his identity isn't verifiable. For this reason, the issuer of a certificate is generally a trusted certificate authority, such as Digicert, GeoTrust, or Symantec. When the owner creates the public and private key pair, they submit the above information and establish their identity to the CA (using documentation or business records), and the CA issues the certificate back to that user with all of the necessary details. Most importantly, the issuer uses their own private key to \"sign\" the generated certificate, so that it can be trusted as authentic (as much as the CA itself can be trusted). Finally, on your computer, there is a list of trusted certificates, called \"root certificates\", that describe the most common CAs used to issue certificates. These are curated by the big companies, such as Microsoft, Apple, Amazon, and Google, who try to weed out the bad actors and those with poor security practices. The issuer of a given certificate may not be in that list, but it may be an \"intermediate\" issued by someone holding one of those roots... creating a \"trust chain\" from the website certificate up to one of the trusted roots. One last bit of info... if the private key is somehow lost or stolen, the owner needs some way to \"revoke\" the certificate, so that users will know that messages to/signed by the owner may no longer be secure. This is done by submitting a message (signed with the private key) to the issuing CA that indicates the certificate has been compromised. The CA then publishes a list of \"revoked\" certificates on their server (signed with the CA's key), so that anyone can check it as part of the verifying the trust chain. Revoked certificates are published on the list until the expiration date listed within the original record. So, while an expired certificate may actually still be valid and intact, there is no longer any way to securely determine if it has been compromised or revoked. The owner is responsible for renewing it before that happens."
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a9uid3 | do planes actually have to request 'permission' to land at airports even when they have flight plans? | Technology | explainlikeimfive | {
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"Busy airports schedule their flights to the minute, and a flight plan is not anywhere near that specific. If you want to land at a controlled airport you need to announce your intentions and await permission. Flights with a special status (like a declared emergency) can do what is necessary to protect the lives of passengers.",
"Read this awesome question and answer of a 747 pilot. This will answer a lot of your questions URL_0",
"Think of it like a restaurant. You can plan to be there and you can even make a reservation (which is very different from planning to be there) but if you show up at the same time as 6 other couples, you may have to wait a couple minutes to be seated.",
"Your flight plan is to inform the FAA and others of your intended plans, it neither guarantees a time to land or spot in a queue, nor does it compel you to maintain the exact path or schedule. It also doesn’t factor with other plans to avoid simultaneous arrivals. Of course, things happen during flights. Winds and storms and passenger issues to pick a few. Upon arrival near your destination, you inform the tower of your arrival and desire to enter the queue. If you have special concerns, you tell that as well. The tower coordinates the arrival. Even when in the queue, adjustments are made, and situations communicated throughout. Airlines do coordinate schedules to some degree, which is why many times you don’t notice. They’ll also slow instead of circle. If you’ve been to a busy or stressed airport, you’ve circled, whether you know it or not. Generally, giant planes and small planes don’t fly into the same airports. Obviously this is a generalization, especially since I noted that.",
"I worked at an airport and I have two friends who are pilots. They do communicate with the ground. Their flight may be perfectly on schedule but there could have been a delay on the ground or an issue with another flight that needs to land first. This may be different at different airports, especially smaller ones. I worked at an international airport that had multiple terminals, a private flight terminal, UPS, FedEx, etc flying out of there as well as a military base connected to it. During peak times of the day there are multiple planes in sight in the air on approach, landing, taking off... It needs to be carefully coordinated. As for Air Force One - I'm sure there are different rules that apply to them in a sense, but I'm also sure that they have communication with the ground as well. I haven't worked with those flights, but I've seen them come in and leave several times. The airspace is shut down for a little while before and after. And parts of the airport may be shut down as well. And there's definitely a heightened security during that times. But all in all, it doesn't affect most people at the airport. A lot of people who worked there didn't even know that it had come in or left. But it definitely would be planned out with other flights."
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a9v961 | Why do nearby WIFI networks appear above mine, even though I am next to my router? | Technology | explainlikeimfive | {
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"Depends on the fliter in the OS. Could be due to name, WiFi security type, strength of the connection, GHz band etc.",
"Being right next to the router can sometimes result in a worse signal because of the way radio waves travel away from the antenna. It’s like being next to someone shouting, you can hear them better from a distance.",
"Some operating systems scan the channels from low to high (which typically correlated to frequency as well). So an SSID at a lower frequency pops up before one on a higher."
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a9vriu | C$ network share | I know this is a hidden share, but what's the point of it? Is C$ a duplication of the C: drive (meaning is it using the same amount of space as C:), and why does it exist? Surely administrators can see the regular C drive anyway? | Technology | explainlikeimfive | {
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"text": [
"C$ is your C: drive. It's not a duplicate of your C: drive, it's the same thing. Administrators can't see the C: drive from a different computer."
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a9wbyo | Difference between Cat5 and Cat5e lan cables? How does this entire LAN tech work? | Technology | explainlikeimfive | {
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"It’s just a huge, broad question. There are four year degree programs about this (Computer Network Engineering). As for the cables, simply put the difference between cat5 and cat5e is that e is faster. This is because of the way the cables are twisted, essentially. They’re made to more stringent specifications. More expensive. Faster."
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a9wme8 | Why can TV antenna's reception be improved by adding a dish around it but the same won’t work for WiFi antennas and cellphone antennas? | Technology | explainlikeimfive | {
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"Your premise is false. It *does* work for these other antennas, as long as you know the direction of the device you are communicating with.",
"We use them for point to point where both units stay in the same place. If you don't mind having to aim, you can make a cantenna URL_0 Cell phones lose the benefits of the multiple towers unless you are way far out from them and unable to lock on a signal.",
"They *can* be improved by adding a dish, provided of course you know which way to point your cell phone or other WiFi device in order to get reception. Usually that would be a huge burden for the use of such devices."
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a9xalj | How is video manipulation done? | I understand one could painstakingly manipulate photos to add, remove or move objects, change the color, etc. But isn't it crazy to do the same for video, since it would need to be done for thousands of frames? Maybe with modern Machine Learning techniques it got easier, but isn't that still in experimental stages? & #x200B; How did they make that effect in Schindler's list for example, where only the girl appears red in a sea of black and white [ URL_1 ]( URL_1 )? & #x200B; Or more recently (this was what triggered the question), what about colors by beck? [ URL_2 ]( URL_0 ) How did they make Alison Brie black and white except for her red lipstick, or flicker colors? While people behind and in front of her don't get affected? | Technology | explainlikeimfive | {
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"One way is to track motion in the video and add the effect/object to that \"stationary\" (relative to the in-footage object) point. We did a post effects project in my uni where we replaced a wound on the actor with a 3D model because the makeup wasn't deemed good enough. We had to track the camera movement and rotation (semi-automatic), replicate the skin stretching as the actor moved (semi-automatic), and manually mask out the original wound for each frame (half our team did this for two weeks). There was also the sculpting, texturing and lighting the replacement wound and matching the colour grading and film grain/noise to that of the original footage. In the end I couldn't tell the charred flesh and jacket wasn't real.",
"There's still a ton of painstaking manual work, but tools like After Effects make it much easier. A major part of it is digital rotoscoping, where they basically are tracing which part of an image to be manipulated. This is done largely frame by frame by hand - look at the credits list for a Marvel film and you'll see dozens of rotoscope artists. I'm underselling what they do, of course. It's an entire industry, and employs hundreds of thousands these days.",
"The colour work you are specifically asking about is actually really easy, you just take the colour information in your footage, define a range of colour you want and then just desaturate everything else. After Effects has a dedicated effect called `Leave Colour` that will do just that to whatever footage you apply it too, [heres a tutorial]( URL_0 ). Even back in the day of actual film this would have been possible, if much more of a pain I imagine. Though looking at the Schindlers List clip and how much the red colouring moves around, it might have also been a case where they just actually painted on top of each frame."
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aa0dob | How do game anti cheats, like BattlEye or GameGuard work? | What I mean is - I know they can check the processes which are running and are associated to the game that you're playing, but how do they know that those processes are actually cheating tools? | Technology | explainlikeimfive | {
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"There are different flags that can be detected to assume someone is trying to tamper the game, such as debugging another process (the game in this case), accessing the memory mapped to that game, running the game in a virtualized environment, tampering the binary or assets and many more. Anti-cheat try to detect those abnormal behaviors targeting the game's process.",
"They guess. \"We know about a cheat program, and it looks like *this*. You currently have something running that looks like it, so we're gonna assume you're cheating.\""
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aa0sei | Why do people that repair phone screens need your passcode to your phone? | Technology | explainlikeimfive | {
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"Every phone has a test mode where you can test every corner of the screen and be sure everything works. Without passcode you cannot get to that mode.",
"I think maybe they need to make sure your finger movements work properly and the sensitivity is okay?",
"Here's a tip if you're an android user. Make a guest account the next time you're giving your phone for repair. Easiest way to give your phone without unlocking your account."
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aa12y9 | in a world of account lockout thresholds, do brute force attacks still work? | Technology | explainlikeimfive | {
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"So you're assuming your account lockout is on the account rather than an IP block. Most brute force systems will block the IP address trying to attack (because locking the account means the genuine user can no longer gain access). A few points: 1) if account lockout is enabled, you could easily perform a \"Denial of Service\" by just hitting Jane's password wrong five times. Inconvenient to the user. 2) by blocking the IP you stop the attack in its tracks from that source for all accounts on your network. The problem is most brute force attacks are more sophisticated than just one source IP address and will target you from hundreds of IP addresses (sometimes thousands) over a period of time. Your brute force detection usually resets after X failed attempts over Y minutes. If you've got 10 IPs you could just try one password every minute per IP and not get blocked. Adding a character to your password exponentially (a to the power n) increases the complexity and time it'd take to brute force, but the overall difficulty of remembering a 14 char password over a 13 char password isn't that much more. You also have the scenario where you the hacker has gained access to the password hash database and can brute force each individual password. Edit: sorry, didn't realise this is ELI5."
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aa2fm1 | Why is there internet download and upload limits. | Technology | explainlikeimfive | {
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"text": [
"Partly to help keep bandwidth available for other people to use; but mostly just because they can make money out of you that way."
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aa31o0 | In the Apollo 13 mission, how did the command module become freezing in the return trip from the moon? | So in the Apollo 13 movie, when returning from the moon, the crew has to turn off all of their equipment in order to conserve energy for the reentry, due to a lot of their fuel being vented. Now I'm not sure if this is just creative license in the movie to create more suspense, but my cursory knowledge of this is that it's incredibly hard to radiate heat away from objects in space for the most part just simply due to it being a void and there being nothing to convect the heat to apart from a small amount of solar wind on the scale of the space craft. So how did it get so cold in such a short time? | Technology | explainlikeimfive | {
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"It's absolutely true that the command module reached temperatures not much above freezing after the equipment was shut off. You're correct that it's hard to radiate heat in space, but on the same hand, it's hard to absorb heat radiated from the sun (radiation is the only method of heat transfer in space as it does not require a medium). The equipment in the command module and lunar module generated a lot of heat, and the spacecraft were designed to dump this heat to keep the cabin temperature comfortable *with all of this equipment running*. With almost no heat-generating equipment on, it got very cold inside. This was exacerbated by the fact that for most of the return trip, the spacecraft was oriented in such a way so that all the windows were facing away from the sun, meaning there was no sunlight entering the cabin to warm anything."
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aa3lvq | How can data (files and photos) be recovered from a damaged or deleted hard drive? | Technology | explainlikeimfive | {
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"text": [
"Most often, \"deleted\" data isn't actually gone. The computer simply removes its reference to it -- like scratching out a chapter in the Table of Contents without actually tearing those pages from the book. Similarly, when new data is written over old data, it may not be enough new data to completely fill the space of the old data. Back to the book & chapter analogy; imagine now writing one page of text into that \"deleted\" chapter. Because the other 15 pages are still there, you can continue to make decent sense of that chapter."
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aa45sz | How do those movie theatre vacuums work? The ones that don’t plug in and you just run it over the carpet? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Wheels turn a drum with brushes, that moves trash into the body of the unit. No suction, just human powered rotating brushes."
],
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aa7l7n | How does a relatively small transformer fire light up almost an entire city? Also, why is it blue? | Technology | explainlikeimfive | {
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"text": [
"Even a relatively small transformer draws a massive amount of power. The power supply is high voltage AC, which is arcing in the open air. Basically, the open air is acting as a fluorescent bulb. It's mostly light from nitrogen, which glows blue, like neon glows red. It's not an unusual thing to have happen, but I've never seen it to quite this extent before.",
"The small transformer is connected to a bigger transformer at the nearest substation. This much bigger transformer is feeding the short-circuit. You don't get the same energy from a short circuit on your outlet, for example."
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aa7ofu | How can videos capture the physical movement of waves passing through guitar strings, when they just look like they are moving back and forth rapidly to the naked eye? | An example of this would be like in this video URL_0 | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Rolling shutter. Image sensors in cameras don't take the entire imagine at one single time, they scan it up and down/side to side. So it is basically capturing the strings in different places for the same frame. Here's a video. [ URL_0 ]( URL_0 )"
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aa8e4x | How do google "index of" websites work? | I know that you can find some interesting stuff(eg. movies, games, software) by adding "indexof" to your google query. I want to know why and how this works and why the websites cannot be found by normal search. I also tried to do a traceroute, ping and whois search but the sites seem to be non existant. How are they able to be found by a specific Google search but not other means. | Technology | explainlikeimfive | {
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"text": [
"The \"index of\" is a feature of the webserver, that is delivering the website. Normally you tell your webserver which file of a directory is the index, or rather which file to deliver by default (i.e. index.html). If the webserver does not find that file it might create an index of all files in the directory on the fly and deliver that as the page. This makes navigation through the webserver easier, and you do not have to write a \"index\" page for every directory. Nowadays this feature is often disabled for security reasons. Back your question I would guess, that searching your term without \"index of\" will result in you finding that page, but much further away in the search results, because there are \"better\" pages containing your term. The \"index of\" pages do not have much searchable data. Only \"index of\", \"directoryname\" and a list of \"filenames\". Including \"index of\" will discard all these \"better\" results, since the term \"index of\" is not a term on most of these sites, but the autogenerated directory index will most likely have \"index of\" as one of the first words on the page. EDIT1: the traceroute and ping tool have nothing to do with searching the internet. They are network diagnostic tools and there is no need for anyone to reply to these packets. You can disable the ping reply of your computer without losing any functionality. If you use windows, the ms firewall does not reply to ping by default (depending on the profile). A Traceroute are just multiple ping requests with different TTLs. And they get answered by routers, most of the routers in the world tend to process these request with the lowest priority or rate limitted, resulting in \"packet loss\". EDIT2: whois only shows you the information about the owner of an ip address or domain name. It should always yield information for ip addresses, domain names might be different sometimes. But the owner of the ip/domain does not have to be the one providing the files. The ip might belong to an ISP, thus they use the same info for all their clients."
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aa8nvd | Why is a camera not able to take a proper picture of a monitor or TV screen? | Technology | explainlikeimfive | {
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"text": [
"Are you talking about the wavy lines? They're called [moiré patterns]( URL_0 ). Nothing to do with the refreshing of the screen. It's an interference pattern due to the difference between the grid of pixels on the screen, grid of the camera sensor, and pixel grid on the camera screen. You can see this same effect if you try to take a picture of a window screen",
"Cameras catch an instant in time, and screens update faster than the eye can tell, but cameras can catch it updating. You can slow the shutter speed to get around it sometimes though."
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aa9li2 | How do computer drivers work? Why do some accessories need them and some don't? | Technology | explainlikeimfive | {
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"text": [
"Basically, a driver is a program (software) that tells the computer how to use the hardware. When you press a key on a keyboard, move or click your mouse, or anything of that nature, the computer needs to have a program to tell it what those signals should make it do. In the case of internals, like a graphics card, it gets a little bit more complicated, but it still is the same basic principal. The reason some accessories do not need drivers is because there are loads of generic drivers that come pre-loaded on computer operating systems. Something really basic that is on almost every computer is a standard keyboard and mouse. \"Generic mouse driver 3000\" would probably work for pretty much any wired mouse that uses a laser to track movement and has right and left click buttons. Now, generic drivers are great for something basic. However, a piece of standard hardware with extra features (like a gaming mouse with extra programmable buttons, for example) might still be able to use a generic driver for basic functionality - movement, right and left clicks, and maybe a scroll wheel - but the extra buttons will be useless until you install the proper driver."
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aac6l1 | How could improper connection of 3.5mm jack could sometimes fully isolate the music in some content? | I've been watching a show with my headphones connected to the PC and something happened that I recall to have happen more than once before, the voices of the people are cut out and the music plays like nothing is wrong. How could it isolate it so perfectly like that from just an improper connection? | Technology | explainlikeimfive | {
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"text": [
"Former audio equipment service guy here. 3.5mm jack is built that way that, if you don’t plug it in fully - it doesn’t connect all 3 wires (L, R, and mutual ground); without ground, both headphone sides plays the same - just the difference between left and right; now, voice is almost always monaural but instruments are almost always either paned to the side or “late” to the side (transients), so the music is still easily heard. Tip: bass also disappears, cause also - monaural. So: ELI5: mono sounds disappear, stereo stays.",
"The only explanation I can think of is that the voices are only in one channel (left or right) and your headphones were only making a connection on the other channel."
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aacmq5 | How are 3D movies made? Are the movies also edited wearing 3D glasses? | Technology | explainlikeimfive | {
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"text": [
"There are 3d cameras that have 2 lenses that allow for the 3d effect. I can't speak about editing though.",
"What you refer to is called stereoscopic vision which requires a movie to be shot on two different films in order to take the differing perspectives of human eyes into account. Traditionally this can be achieved by using two camera with a lens centre distance of 6 cm which equals the medium distance between left and right eye. When editing movies you can hide L or R view, it wouldn't be feasible to edit in stereoscopic vision."
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aafurh | Why when stored vertically vinyl records do not warp but when stored laying flat (horizontal) they can warp? | Seems like it should be the opposite | Technology | explainlikeimfive | {
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"text": [
"You can store them horizontally, you can even store two of them on top of each other, but keep in mind: The more you put on top of each other, the more weight will be on the bottom ones. The edges of the cover and sheet are twisted back and glued, which means that the paper there is thicker than in the middle. As such the middle of the record will be pressed deeper than the outer, which will make it warp. When taking a record from out of a horizontal stack, you will bend it. Not on purpose, but it will happen. Also the stack will fall over once in a while. And: Don't store them in direct sunlight. Don't store them next to a heater. Don't store them in your fireplace, you never know who accidentally fires it up."
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aagoil | What is a long exposure photo and how are they taken? | I have seen a lot of "long exposure" photos in reddit and I can't seem to understand what are they exactly and how do they work, any help? | Technology | explainlikeimfive | {
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"text": [
"To take a picture, we control for 3 variables - aperture, exposure time and ISO. ISO is the sensitivity of the sensor. Higher the sensitivity, higher the noise. Increase ISO only if the light is low and subject is moving. Aperture is how wide the lens is open. Larger the opening, more light falls into the sensor. Larger aperture also affects the depth of field. Exposure duration is how long the aperture is kept open. More the duration, more light flows in, and more the blur. We use large exposure duration to take static pictures (sky, stars, moon). We also use it to get silky smooth pictures of motion (waves in a sea or froth in a brook)."
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aagt4p | How does the live traffic feature on Google Maps work? | Technology | explainlikeimfive | {
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"text": [
"URL_0 It collects data from smartphones with location turned on, and if notices a lot of users seem to move slowly on a certain road, it'll know that there is a traffic congestion there.",
"They gather real time data from people who have their phone turned on & are signed in. You don’t really need that many active users driving down a highway for google to determine if traffic is moving fast or slow"
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"https://en.m.wikipedia.org/wiki/Google_Traffic"
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aagyft | What exactly does "Airplane mode" do and how does it keep my phone from disrupting airplane functions? | Technology | explainlikeimfive | {
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"It disables the cellular transceiver in your phone. It just turns off the part of your phone that sends and receives data from cell towers. The idea is that you will not be creating electromagnetic interference that could potentially interact with the aircraft's instrumentation. The reality is that everything is so well shielded now, it probably wouldn't matter.",
"Wasn't it proven that phones don't disrupt aircraft functions at all? Anyways, airplane mode just turns off Wifi/Mobile Data/Cellular Service/possibly radio",
"Airplane mode disables the radios on your phone that talk to Cell Towers. Phones periodically ping phone towers basically saying \"Hey, are you there? How many of you are there?\" the further away a phone gets from a Cell Tower, the louder it yells \"HEY!!!!\". That's why older phones, when they are out of service range, drain battery really fast. Its because they are pumping as much power as they can into that little antenna trying to yell \"HEY! Is anyone there?\". Modern phones give up after a while and check a lot less frequently after enough attempts have failed. Which is why if you are in an area with low reception and your modern phone loses bars, it helps to flip it into airplane mode and flip it back so the phone can try checking for cell towers one more time! Cellphones don't really disrupt aircraft systems as much as they cause an annoyance in the captains ears. When 100 devices are going off yelling \"HEY\" at 50,000 feet, each \"HEY\" sounds like a high pitched chirp in the ear of the radio the captain, who is listening to Air Traffic Controller instructions. If the chirps are really loud (on unshielded equipment) it can prevent the captain from hearing important information, or delay how long it takes for information to be conveyed! (that's how turning Airplane mode on helps!)",
"\"Airplane Mode\" turns off all the radios in your phone, for example your cellular and wifi radios. This is why your connection goes dead whenever you use Airplane Mode. In theory airlines make you do this (or shut off your phone entirely) because they don't want transmissions from your device interfering with the plane's instruments. It's a very very old regulation and its applicability to modern aircraft is dubious at best but the airlines still take a \"better safe than sorry\" approach.",
"As others have said, Airplane mode mostly just turns off the radios on your phone. These features by themselves will not disrupt airplane functions. You can think of it this way incidentally, if having dozens of devices with radios would cause problems with the avionics, why would they equip planes with wifi for you to use? It was a theorized fear years ago but not a practical one. The big reason they make you put your phones and such away during takeoff and landing is that those are the points most likely for something to go wrong during the flight. They want you focused on the plane and what's going on outside both for safeties sake (you may have a bit of information that makes you slightly faster at responding in the emergency) and so that after the incident, you might be able to provide some critical piece of information (I saw a duck hit the wing!) that would help the accident investigation."
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aahnmb | How does a computer keep track of the time even when its off? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"There is a real clock in the computer that keeps track of date and time even when the computer is powered off. All computer mother boards have CMOS battery installed that keeps this real clock running. The battery doesn't last forever but from my experience it can last up to 10 years in some cases.",
"There is a battery on the motherboard in every PC that holds a current to the bios chip of the board. This bios chip is powered 24/7 by the battery called a cmos battery. In this way, with this CR2032 battery, usually, the chip stays powered and things like time and bios setting are stored. Over time, like many years, these batteries do die and the time as well as bios settings are reset to default."
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aahuhx | How do interactive movies (like Bandersnatch) work, technologically-speaking? | Technology | explainlikeimfive | {
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"text": [
"I haven't watched it yet, so no spoilers please, but Basically it has to do with utilising Netflix's metadata parser. You may be familiar with how you can click a button to skip the intro of a show, or to immediately go from the credits of one ep to the start of the next episode without having to sit through the intro. Each video has what's called metadata - data that is about the file itself. This data includes things like the screen ratio, production company, etc. But Netflix can also add metadata for marking specific moments in the video, and to have buttons appearing to take you to specific moments if you click them. To make an interactive movie, one needs to just film all the possible scenes, edit them together, and keep a list of the start times of each scene. Then by inputting those times as markers in the metadata, and data for the buttons, you can allow the video to jump to specific scenes when those buttons are pressed."
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aai7mu | Why do holy books (the Bible, Book of Mormon, etc.) tend to use similar thin paper? | Technology | explainlikeimfive | {
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"text": [
"The special type of paper is called \"scritta paper,\" and it is used in books that have a large number of pages to reduce the thickness and weight.",
"A big part of it is cost - you can get a 1200 page hardcover for 12$, and a softcover for 3$ (or free if you ask nicely, haha). You can get Bibles printed on nicer paper, and other books of the same length, but they’re more expensive and usually have to be split into separate volumes. They’re also huge and unwieldy, not appropriate for carrying around on you and bringing to church and so on. As a casual Bible and Bible adaptation collector, I’d rather have interesting translations and variations than one of them. That said, this isn’t universal across religions - my multivolume copy of the Torah’s not, although it’s a bit of a higher end item, and I’ve never seen a Quran on scritta, not even the cheap ones evangels give away (so much better quality than Gideons). It’s much shorter, to be fair."
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aal3g3 | Why does a weapon scope aims precisely to where the bullet is going to hit if it is standing above the barrel? | Technology | explainlikeimfive | {
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"I mean, it has to be calibrated to a certain distance. Its not like video games where ya just pop it on and its accurate",
"Well first of all you have to calibrate the scope. You still have to adjust for distance, wind etc. There's also the Coriolis Effect which, if shooting over long enough distances, you must account for the curvature of the Earth and whether you're in the northern or southern hemisphere. Snipers are unreal at calculating these things.",
"A scope is sighted in to be dead on at a specific range (say 100 yds). Because a bullet flies in a parabola, you have to aim lower for a target closer than that zero’ed range and higher for a target at a more distant range. You can alternatively adjust the scope to account for the range difference before each shot.",
"It's not. There are two imaginary lines for each gun basically - sight line and bullet trajectory. Sight line is a straight line that goes through three points - your eye, scope/sight and target. A bullet trajectory, on the other hand, is not straight - it is influenced by many factors, like gravity and air resistance. To simplify, the bullet path is a curve, that goes paraller to the ground or up in the initial part of the trajectory, and then starts to fall down. So, in order to hit a target that is far away, you have to point the gun slightly upward. The elevation angle for each distance (100-200-300 m, etc.) can be precalculated, and so, the sight/scope is sligtly tilted, so that sight line and bullet trajectory intersect at required distance. This is called \"zeroing\" the gun. There is also [this]( URL_0 ) picture, which may be helpful."
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aal91x | How a PS2 game will be incompatible with the Xbox even if both games are written in C++ | Just something I'm wondering about. I have an engine that makes games with C++, but there are compile/export options to make the game a game for the Nintendo Switch, PS4, PC or Xbox One. What exactly do these options do? For example why can the same PS2 game be ported to the Xbox but if you put the Xbox disk into the PS2 it would not load? | Technology | explainlikeimfive | {
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"C++ is a \"high level\" language. The CPU doesn't directly understand C++, it has to be converted into machine code. That's what the compiler does. The PS2 and the Xbox use different machine code. They \"speak different languages\" in a sense. Some C++ compiled for the PS2 just won't make sense to an Xbox. That's one reason. Another is that the hardware is just different. For example the PS2 game might have code that uses the PS2's special co-processors, but they just don't exist on Xbox. For some things they might have equivalent hardware (e.g. they both have GPUs, they both have controller ports, etc), but it just works differently so code written for one won't work on the other. Then there's the OS. A modern PS4 and Xbox One are actually very similar on the hardware level. They have more or less the same CPU, which understands the same machine code, and most of the rest of the hardware is also very similar. But a PS4 game still won't work on an Xbox One. The Operating System (or System Software as its often called on consoles) provides a lot of features that games use. Using the hardware goes via the OS using an Application Programmer's Interface (API). The two consoles have different APIs for things like playing sounds or drawing graphics, so a game written for one won't work on the other.",
"The operating system provides a bunch of functions for a program to interact with. These functions are essentially what connects the program to the hardware. Since Xbox and PS have different hardware and different operating systems, these functions are different between them, so writing code that will run on both is difficult."
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aal9yk | How are console games developed for a system when they take longer than that system’s lifecycle? | I read an article that the game Cyberpunk 2077 has been in development for the past 8 years. Say a game that’s in development spans a console, do the developers need to refactor code and assets to work on the new platform? | Technology | explainlikeimfive | {
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"In short: Yes. Nowadays assets are often made in very high quality (because it's easier to work with) and then downgraded to fit into the game. Porting a game to a new console can be very little work, assuming the architecture isn't too different from other hardware: you just need to rewrite a bit of platform specific code (ie: the part that does makes the interface between the engine and the console itself), and export the assets with the desired settings.",
"They're really just making the game for PC at this point. As development gets closer to completion, they'll port the game to whatever consoles are popular by that time. They may internally decide they're \"targeting\" current-gen consoles, but really this just means they're making certain design decisions to ensure that it'll still be technically possible to port the game to those consoles."
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aalkxm | In old cartridge console games, why would an image be frozen onto the screen if the cartridge was removed during play? | I can remember as a kid that if you were playing an N64 or Genesis and, while the game was running, removed the cartridge without turning off the console, the game's present image would be frozen onto the tv screen. How does this happen? | Technology | explainlikeimfive | {
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"text": [
"The graphics processor (if you will) would await commands from the central processor that would be awaiting responses from the cartridge based on the parameters in the rom file. If the cartridge was all the sudden gone, the processor would move into a hold loop awaiting a response and thus the image would reside as the next set of commands to render (or draw depending on your POV) would never arrive as the processor wouldn’t receive a response from the cartridge.",
"The graphics hardware on these systems have what's called a framebuffer, which stores the colors of all of the dots (pixels) that make up the image on the screen. The process of displaying the framebuffer on the screen is automatic, and doesn't depend on whether the cartridge is in or not. The game code on the cartridge is responsible for getting the framebuffer updated to reflect what's going on, whether it's character movement, background movement, rotation, etc. When you pull the cartridge out, that crashes and no longer updates the framebuffer, so you're stuck with the frozen image of what was last put there."
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aamfk7 | With the popularity of high powered telescopes, can't moon landing deniers be easily proven wrong by seeing leftovers from the landings? | Basically the title... With the popularity of high powered telescopes, aren't there enough consumer grade telescopes available to see all the leftover stuff on the moon from all the landings and wouldn't this easily disprove all moon-landing deniers? Or am I underestimating how hard that would be to see | Technology | explainlikeimfive | {
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"Moon landing deniers aren't interested in seeing proof. There is ample proof available already, and there has been for decades. Anyone actually curious about it could find definitive proof quite quickly. New proof is irrelevant if someone is already ignoring the existing proof.",
"> Or am I underestimating how hard that would be to see You are underestimating how difficult they are to see. While we can take good pictures of far more distant objects, those objects are also far, far larger than the artifacts left on the moon by the landings. It is like asking why if we can see mountains from miles away we can't see how many fingers someone is holding up from 200 yards. Also most of the things we try to look at produce light of their own, so change that to mountains which are literally on fire.",
"You're misunderstanding how hard it would be to see. Take a look at [these]( URL_0 ) pictures of the landing sites and realize the clearest pictures on the left were taken by the optics of an advanced NASA satellite passing at an altitude of only 20 to 25 miles above the landing site (maybe less). By comparison an earth based consumer grade telescope is trying to spot them from a distance of 200,000 to 250,000 miles.",
"Let's figure out why we can't use just any ol' telescope to spot a lander from Earth. We've got a couple simple formulas that are shorthand, they'll tell you what you're dealing with and what you'll need to do what you want - It's not ELI5 to derive the formulas and explain why optics work that way. How big does an object have to be for a telescope to resolve it? The relation can be explained in the equation: R = 11.6 / D. R is the angular size of the object in arc seconds. There are 360 degrees in a circle, 3600 arc seconds in a degree. D is the diameter of your mirror in centimeters. To calculate angular size, we need another formula: (d / D) x 206265 = a. d is the size of the object, D is the distance from the observer. So a lunar lander is 4 meters across and 400,000,000 meters away. So (4 / 400,000,000) x 206265 = 0.002 arc seconds. What's the smallest the Hubble Space Telescope can resolve? The mirror is 2.4 meters across, so 11.6 / 240 = 0.05 arc seconds. That means the lander would be an indistinguishable point of light to Hubble. It gets worse. According to Nyquist Sampling Therom, you actually need twice the resolving power to properly see what you're looking at, so this means Hubble's resolving power as actual half, 0.1 arc seconds. *YOU COULD HIDE A FOOTBALL STADIUM ON THE MOON*, and Hubble couldn't distinguish it from a point of light. So Hubble can see anything 0.1 arc seconds across or larger, no matter how far away it is. We see magnificent photos of galaxies and gas clouds, but they're hundreds of thousands to billions of lightyears across. --- Of course, deniers are unreasonable. James Randy has proven this time and time again. Ever hear of the James Randy $1m Paranormal Challenge? If you can scientifically prove a paranormal phenomena, you get the prize. And the way they do is is they work with you to design a scientific experiment. The challengers AGREE to the experiment they help design! And yet, when each and every last one of them fail, they all continue believing, even though they proved themselves wrong. This is the mentality you're dealing with. Even if you had a 100 meter mirror, which is what you would need, and it was a classic telescope you could peer though a lens and actually see the lander, they will STILL justify their disbelief. You've tampered with the optics, the moon itself is fake, man hasn't been to the moon, that was space junk put there to make it look like we went there. Just you try it. I'm sure you've gotten into arguments with people that you've proved them wrong, and yet they still won't concede - in their minds they're still not wrong, they're just resentful."
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aamq9z | why does restarting seem to solve so many computer problems? | Heck, it solves many other problems with electronics too from a faulty bulb to a WiFi router. | Technology | explainlikeimfive | {
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"It clears the RAM and reloads all of the drivers. So if theres anything that is stuck or had a driver failure it fixed the immediate problem. The problem may still exist but its been put back to square 1.",
"Have you ever read a Choose Your Own Adventure Book? They're pretty neat- at certain points in the story, you're given the opportunity to make a choice, and you flip to a different page depending on what choice you make. These books are pretty straightforward to follow since all you need to know is the current page you're on and the answer to the decision you just made (in computing theory, we'd call this a deterministic finite automaton). Computer programs are like these books with an extra twist added- you need to have a pencil and piece of paper with you, at various points you'll be instructed to write stuff down, and the pages you turn to are determined not only based on what choice you make, but also what you have previously written down. And also the books are a few hundred thousand pages long, written by dozens of authors possibly over a period of years who are all trying to make every path follow a coherent story. So there's plenty that can go wrong- perhaps someone typo'd what page you should turn to so you end up going back to the same page over and over again, never hitting an ending. Perhaps you find a way to a page that assumes you wrote something down, but the path you followed to get there never had you write it down so you don't know which page you're supposed to turn to. What does this have to do with restarting? Well, restarting is like saying \"screw this\", turning back to the beginning of the book, and grabbing a fresh sheet of paper. Sure, if you follow exactly the same path back through the book you'll end up with the same problem again, but there's so many choices that odds are you won't follow exactly the same path, and hopefully the path you follow this time is one that doesn't hit any of these typos or mistakes.",
"It's like if you are giving directions to someone from their house to yours and they get lost in a place you don't know. It will be much easier for them to start back at their house than to find a way out of an unknown area."
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aan6r0 | Why are most file extensions 3 letters long? | Technology | explainlikeimfive | {
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"text": [
"Many years ago when memory was an issue and the name of a file could actually be important for your computers allocation of memory, ~~windows microsoft operating systems~~ older operating systems used a so-called [8.3 filename system]( URL_0 ) which was 8 characters for the file name and 3 characters for the file extension.",
"Because that was the way filenames were coded in the first mainstream operating system (DOS) that was the foundation of early versions of Windows.",
"A lot of modern standards within computers were developed at a time when space was a premium. The screens were smaller and much slower to update in addition the storage space were very small compared to modern standards. So if you could just save a few characters in each filename you could save a lot of space and time. So a lot of compute systems limited the file extensions to 3 letters and the filename to 8 letters. This practice is something which have continued even twenty years after all systems can handle much longer filenames. This is mostly because newer systems still have to be backwards compatible with older systems which had to be compatible with even older systems and so forth. However even new file types tend to have extensions shorter then five characters as long filenames can be annoying to work with."
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aan6vf | why is the sound quality of a song so much better when it’s played during a movie vs just listening to the song regularly? | Technology | explainlikeimfive | {
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"text": [
"I have not experienced this. Maybe it is something subjective to yourself? I listen to music on the same HiFi system that I use for movies. Both sound equally great. Can you provide a specific example of a song in a movie? I'll stream the movie then play it via Spotify or Tidal and listen closely.",
"Movie editing is magic, you have nooo idea how much time a **team** of people spent on that 15 sec clip"
],
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7,
6
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aap1iu | Why is styrofoam still used? | I just removed a piece of exercise equipment purchased from Costco. It was packed in molded styrofoam. I'm super careful that I don't litter anything, but styrofoam makes that nearly impossible. Tons of little foam beads break off and blow away, stick to anything with static, and are very difficult to clean up, yet we still use them. Why? I know they're cheap to manufacture, but in an age where we seem to care so much about the environment, it seems these should be left behind. | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"It's cheap, effective, and for the most part completely legal. As long as those three factors are still true companies will very likely continue to use it. If another, cheaper, more effective option presents itself or styrofoam is banned then we'll see a change",
"Styrofoam is very good at keeping stuff padded and from breaking at an inexpensive price. Know what is even more costly than waste foam? Having to manufacture an entire new product and ship it to you because the first one was broken in shipping. Other padding solutions have their own downsides.",
"Styrofoam is a remarkable material. It is 98% air and the rest is a very inexpensive plastic. The main reason that styrofoam is not recycled is that it takes up so much volume that it is not cost effective to collect it for the small amount of plastic involved. As a packing material, it sort of hits the holy trinity: it very cheap, very strong and very light. There's really nothing else that comes close.",
"Styrofoam is super cheap and a great packing material. Its soft so it protects the object but strong enough it can take a hit and absorb it so the packed item is safe While we say we care about the environment, we generally only care if we can care about it for a similar price. Would you have paid $10 more for that object to have no styrofoam in its packaging? Would everyone? Cost is a huge driver of purchasing decisions so saving a buck or two on packaging can amount to a lot of sales for a company."
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aap44j | How do you judge lenses for cameras? | I've been looking at lenses for my camera, but there are so many terms to watch out for. I've come to understand the 14-80mm thing and how that works for zooming, but once you have e.g. two 14-80mm lenses, what else do you consider? | Technology | explainlikeimfive | {
"a_id": [
"ectwdh4"
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"text": [
"First of all, the aperture. f/2.8 has a shallower depth of field and can capture more light than f/5.6 Then you should consider optical defects, like chromatic aberration, geometric distortion, vignetting and propensity to flare. You should also consider the resolving power. Look for MTF charts. If the camera does stabilization in the lens, you definitely should consider a lens with it. **Edit:** A couple things I forgot. Macro capability -- whether the lens can take 1:1 images of a subject. Be careful in that anything cheap that says \"macro\" on it probably isn't real macro, but some half-assed approximation considerably worse than 1:1. Since a true macro is 1:1 what distinguishes them from one another is how close you have to be to the subject to get that much magnification. With a 30mm macro, you need to be very close. With a 150mm macro, you can be a good distance away. This is very important for subjects like insects, which don't appreciate you invading their space. Minimum focus distance -- how close you can get to the subject and be able to focus on it. This can actually be annoying in that some lenses want to focus quite far away, to the point that one might bump into the issue quite often. Then there are a bunch of miscellaneous features that don't really affect optical quality, but can be very useful: * Sealed lenses resist water and dust. Very useful if you plan to shoot under difficult conditions. * Some lenses are internally focused and nothing changes outside when focusing them. * Not all lenses maintain focus when changing the zoom level. * They may be made of better or worse materials. * Some have a \"quick shift\" focus system that allows you to manually focus the lens without fighting with the camera * Sigma has a dock for their lenses that allows connecting them to a computer and fine tuning the parameters"
],
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5
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aaq1dk | How does the electronic ignition in a lighter with no batreries work? | Technology | explainlikeimfive | {
"a_id": [
"ecu0ftb"
],
"text": [
"There are certain crystals that generate electricity when squeezed or bent. It's called piezoelectricity. The crystal has two electrodes either side to collect the electricity when the button is pressed, one is connected to the has jet nozzle nd the other to a metal rod just above it. The button also starts the gas flow and the spark jumps between the rod and the jet through the gas, igniting it. The same principle is used to produce sound in cheap record players. The needle is connected to the crystal and the bending caused by the wobbles in the record groove generate a signal that is amplified to the speakers."
],
"score": [
8
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aaq57x | What cores, threads and other related terms are when talking about game performance | I recently updated my Stellaris game and the game has slowed down a lot. Apparently this is something to do with cores and threads, but I can never follow the conversation. Could someone please explain? | Technology | explainlikeimfive | {
"a_id": [
"ecu1j7y"
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"text": [
"Up until the mid-2000's the most common CPUs could only do one thing at a time. It could only be doing work on one set of calculations. It had the ability to pause its work, set aside one set of calculations and work on another set but the first set would be waiting on the second one before it can finish. We say that those CPUs had a single core. A common problem in computing is that sometimes the CPU has extra power that isn't being utilized because the active program can't get data to the CPU fast enough. So, it has to wait until data can be loaded from RAM before it can keep working. To try and avoid wasted time they started doing something called simultaneous multithreading (SMT). The CPU would tell the operating system that it actually had two cores so that the operating system would send it twice as much work. When the CPU was waiting on a program to get its data ready to be processed, it could work on a second program. This sped up overall processing by reducing wasted time. So, a single core CPU with SMT enables is what we would call a 1 core, 2 thread processor. A core is the actual chunk of circuitry that does the processing and a thread is a sequence of instructions coming from a program. The CPU only has 1 core but it can work on 2 threads at the same time, quickly swapping between them. Eventually CPU manufacturers started adding in multiple physical cores to their processors. Now they could truly work on two distinct things at the same time. Depending on the exact CPU they would still enable SMT and so you now had a 2 core, 4 thread CPU. This has continued to scale up and now we have mainstream 8 core, 16 thread CPUs. Some programs scale really well with more cores and more threads because their workload can be easily split between the different cores. However, if the program is only doing a single thing at a time then having multiple cores won't speed anything up because that program can only use a single core. Modern games are commonly built to run well on up to 4 physical cores because that was the standard number available for years. But, depending on the game and how it is written, some games can benefit from more cores and even virtual cores in the form of SMT."
],
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49
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aaqepu | What's the function of a Screensaver | Technology | explainlikeimfive | {
"a_id": [
"ecu364m",
"ecu40of"
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"text": [
"Back in the day when people had cathode ray tube monitors, if you left a static image on your screen for too long it would \"burn in\" and permanently discolor the screen. So people invented software called \"screen savers\" that after a certain period of inactivity would either black the screen or cover it with a simple moving image that wouldn't burn in.",
"Back when old monitors such as crt monitors had an image left on the screen for too long it caused screen burn. Meaning when the image was taken off the screen an imprint of what was left up could still be seen. Screen savers were meant to “save the screen” from screen burn. Screen savers were mainly black with moving constant moving images so no screen burn could occur. So no real function now I don’t think."
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aaqf9f | How did daguerreotypes work? What was the process? | Technology | explainlikeimfive | {
"a_id": [
"ecu4of3"
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"text": [
"For that type of early photography you take a dark baseplate coated in silver and expose it to fumes from typically iodine or chlorine. This changes the pure silver to a compound that is sensitive to light. The places where the light hits are turned back into silver by that. So after exposure you get the image in silver upside-down. After exposing the plaque you expose it to mercury fumes. The mercury sticks to the silver but not to the silver compund. After this step you dip the plate into a solution of potassium cyanide which removes the silver compound and you get the image from the shiny mercury on the black plate. This \"photo\" is very fragile so you need to put it behind a glass plate and and seal it airtight so that the picture doesn't fade."
],
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aaqu7a | why do digital clocks, like the ones on your stove or car, always lose time and fall behind, but never gain time and speed up? What mechanism controls their “time-keeping”? | Technology | explainlikeimfive | {
"a_id": [
"ecu7c6f",
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"text": [
"the clock in my car actually runs fast, i have to set it back every couple months or so because i start calculating if ill be late to work or not by subtracting five minutes",
"The clocks of the type you're describing are typically quartz movements. Basically, there's a tiny crystal of quartz that has an electrical charge applied to it, using a battery, so it vibrates. This vibration is of a well known frequency and generally remains constant. The problem is a quartz time keeping device is most accurate within a certain temperature range. When the temperature goes outside of this range the quartz crystal vibrates slower, resulting in the clock falling behind. The reason your clock typically won't run fast, is that the quartz is vibrating the fastest within the optimal temperature range and will only slow. While this is the biggest reason, there are also other factors in play, such as the quality of the time keeping hardware. Cheap watches are accurate enough for most people, but they're cheap for a reason."
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aasckm | What is, and how do, torrents work. | Technology | explainlikeimfive | {
"a_id": [
"ecuki55"
],
"text": [
"Imagine that a \"regular download\" is like you copying a book from start to finish in exact order. you can speed up your download by writing faster may be getting a better pen or reading faster At the end of the day you will still be limited by the system that you are using which is following the order of the words in the book I like to think of torrent downloading as copying a book but getting bits and pieces from different pages at the same time You are not limited by following the order of the words in the book but instead limited by the number of words that you can get from each page at the same time if that make sense Torrent downloading is like a thousands of people contribute in small bits and pieces to each other to speed up the download process"
],
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4
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aasoxb | Why did televisions go from squares to rectangles? Is there an actual reason for the shape change or is it just for aesthetic purposes? | Technology | explainlikeimfive | {
"a_id": [
"ecuntri",
"ecur41g",
"ecunuse"
],
"text": [
"It more closely matches cinematic screens, making the migration of films from theaters to screens more appealing. Prior to this, two techniques were used to try to put big screen movies on television. The first is “pan and scan” where the more interesting parts of the screen were captured, chopping off the sides that aren’t deemed interesting, but leaving the whole of the image height. The other is “letterbox “ where the film is filled into the whole television screen, but the top and bottoms are left blank, all making the content a little smaller. Neither is totally satisfactory, so allowing the whole image to be presented is a good reason to shift technology.",
"*not a troll answer, nor an educated answer our eyes field of view is wider than it is high. two points, separated by an inch or two horizontally. vision is a rounded rectangle, so wider aspects are natural.",
"Movie theatres have traditionally show movies in a wide-screen format. As a result when movies are adapted for cable tv part of the scene has to be cut away to fit a 4:3 television format. When Flat screen TVs started getting introduced they made a conscious decision to adopt the 16:9 widescreen format in order to standardize it for DVDs and TV."
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5
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aau6ew | How do seeds in video games work? | Like how in the binding of Isaac it gives you a string of eight (?) letters and numbers, and if someone else plugs in those digits they get the exact same run. How does this work? Are these values stored somewhere? | Technology | explainlikeimfive | {
"a_id": [
"ecv0bmn",
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"text": [
"The seed is converted into a number, which is then used to load a [Pseudo-random number generator]( URL_0 ). The PRNG is a mathematical formula that generates a list of seemingly random sequence of numbers. The game then uses this sequence of numbers to generate the game world. If you feed the same seed to the game, then the list of numbers is the same, so the generated world is the same.",
"You're asking about procedural generation. You might think this is synonymous with random, but it's quite the opposite. Basically a complex series of algorithms are used to generate your world state. In order to do this, it needs a starting point, or a seed. For example when starting a new Minecraft world the system generates a seed and a starting chunk. Based on the seed and your chunks coordinates the algorithm generates all the features of that chunk as well as every chunk within your visible range. as you continue exploring the world that same seed is used along with the new coordinates to generate new chunks. The algorithm is written in such a way that is very very unlikely that to contiguous chunks will not match up. If you then press f3 and copy down that seed and give it to a friend running the same version of Minecraft they can create the same world you are in and that can be proven by having them travel to the coordinates you started at it will be an exact match. The world you generate isn't stored anywhere rather the algorithm itself can be said to contain every possible world with every possible seed. This is because algorithms are simply patterns or sets of instructions and the seeds affect how those algorithms will react. no matter how many times you try using the same seed even if you start in different areas you can return to the origin 0 0 and find that they're all the exact same world. The only way this breaks down is when running two different versions which do not contain the same algorithm. The smallest change to it can result in drastically different worlds. you can actually affect the algorithm using the advanced world generation settings and see this for yourself. Adjusting one slider might make terrain features wider or slimmer in one direction or make them taller or shorter. Some if affected enough can result in nearly unrecognizable worlds. Now imagine rather than just changing those variables you actually change a set of instructions that use the variables. If those instructions now act differently the same numbers between those two sets of instructions can result in vastly different results"
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"https://en.wikipedia.org/wiki/Pseudorandom_number_generator"
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aau8wg | How does a country "shut down" the internet? | Technology | explainlikeimfive | {
"a_id": [
"ecv0jds",
"ecv0ogc",
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"text": [
"Many countries, especially smaller ones, have only a very small number of telecom companies. If they (under government orders) turn off their network router devices, almost no one in the country has Internet service.",
"It's not shutting down the global net, just every thing in their area. The internet relies on a network of very powerful switch nodes called the Internet Backbone to handle the absolute tons of traffic; sort of like how when you ship a package, the truck takes it to the local sorting center, where semis full of packages get sent to other sorting centers. You yourself are sending just little packets of data, but the \"sorting centers\" of the Internet are like the semis able to handle tens of thousands of packages easily. So how do they shut it down? Disconnect the nodes within their country from the external links. If they want to knock it fully offline, just take their backbone switches down entirely. Other traffic that usually went through those one their way from one end of the world to the other will just find an alternate route to its destination, if there is one.",
"Simply put, you shut down internet access to a country the same way you'd disconnect yourself (your home or office) from the intetnet: by turning of the main router that connects you to the internet feed entering your premises. At a country level, it happens the same way, except the main router is just a lot bigger than the one you have at home. For smaller countries that get internet through an international underwater cable, it's even easier: they just shut down the device that sits between said underwater cable and their main router. For larger countries, such as the US, where internet access arrives through multiple points, shutting down the internet would require every single internet provider to shut down his main router, which would take a coordinated effort and take longer, but the end-result would be the same."
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aauj0h | Server vs. External HDD/SSD | Is a server basically just a bunch of hard drives connected to the internet or is it something else? | Technology | explainlikeimfive | {
"a_id": [
"ecv2mtp",
"ecv3e7k",
"ecv6raa"
],
"text": [
"A server is just a high powered computer. They have all the components a regular computer has, and they usually have an array of hard drives rather than just one hard drive.",
"To be clear, a server is just a name for a device that acts as a server. I know. Using the name in the definition. But your personal computer at home can be a server. A server can be a bunch of hard drives with networking software. A server can be a gaming console. It can be those giant dark rooms with VCR looking things on racks, lit only by LED lights you see in action movies. The server is part of a request/response relationship. A computer asks it for something (ex. files, reports, routing etc.), it responds to that request. So what what makes it different than just a hard drive? Primarily the software/architecture behind it. While your hard drive can act as a server if you set it up to be one, it isn't a server until you tell it to be one. A hard drive itself is just set up to store data. That's it. It doesn't have instructions on how to set up communications between other computers or how to exchange data between those computers. It can become part of a server when it's used in a system that is set up to do those things.",
"A server is just a computer that provides a specific service (hence the name). Besides hard drives, they also contain software to use that data. For example, Netflix doesn't let you read and definitely not write to their hard drives. Instead they read the data themselves and stream it to you, or to multiple people at once. Another example is video game servers. They don't provide storage resources, but part of the game logic. Finally, the closest you get to \"Just hard drives connected to the internet\" is a File Transfer Protocol (FTP) server. It is the most common type to share files, but of course also provides some access control logic etc. If you want to, you could use your own PC as an FTP server and share files with others."
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aavf32 | Why do some search engines change predictions, even though I'm typing the suggested letters? | For example, Windows 10 search: "n" = > "Notepad" "no" = > "Notepad++" "not" = > "Notepad++" "note" = > "Notepad++" "notep" = > "Notepad" "notepa" = > "Notepad" "notepad" = > "Notepad" (Example found in /u/Wargon2015 's comment on reddit, happens on many occasions, though.) | Technology | explainlikeimfive | {
"a_id": [
"ecv9xd7",
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"text": [
"One possible idea I know to explain that, is that it's designed as a user experience thing. You start typing, and it makes suggestions, you click them if you want those. If not you keep on typing, so you're telling the system that the suggestions weren't what you wanted. Doesn't explain why it wouold keep flipping between two suggestions though.",
"Suggestions use probabilities to determine what to suggest, which are learned from user behaviour. Given a string of characters, what search phrases do users tend to select from the suggestions, or go on to type out? Hypothetically if you started from scratch (no learned suggestions) and typed \"no\" then select notepad twice in a row, and then type \"not\" and select notepad++ twice in a row, the probabilities will now have learned that given you pause with those two strings entered, you go on to select those apps, so when you start typing in the future you'll get the same suggestions back. Obviously implementations vary wildly depending on the search engine and its features, and this is quite a simplistic algorithm which is almost certainly not used in a pure form in the wild, but it's something you could implement yourself and the basis for a simple suggestion engine.",
"I am sorry but.... This is the first time I am hearing about notepad++..... And I need a moment....."
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aavhce | How are modern cartoons made? | Technology | explainlikeimfive | {
"a_id": [
"ecvcx5p"
],
"text": [
"Anime is still hand drawn. If you watch the after credit, there are keyframe animator (原画), secondary keyframe animator (第二原画), and much more. Most of them are drawn on paper and scan to computer."
],
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3
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aawz3i | Ackermann function | Also what does primitive recursive mean? How Does the function relate to the hyperoperation hierarchy? | Technology | explainlikeimfive | {
"a_id": [
"ecvst4w"
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"text": [
"I hope I can help you with primitive recursion. So u have set of basic (primitive) functions which are just 3 I think. Constant, successor and projection. Each of these takes some input and produces output. The first one is pretty straightforward and always returns the same number doesn't matter what the input is. It can be any number you need to be returned. The second one returns the next element in the array. If we consider positive natural numbers (which is basically all you need in theory of computation) and we have input of 5 it will return 6 and so on. Then there is projection which is a bit more complicated but it takes a set of inputs and \"projects\" them on the set of outputs. Then there is a composition which basically says you can put functions together u can see that as chaining them sorta. With all this you should be able to express any computable function. Let's say you want to perform addition 2+3 but you don't know what addition means. You have only your three basic functions. But. Addition is just adding one more times which is our successor function. You have input of 2 and then you call successor three times which will increment (or we can say return following element from array) three times which then gives us 5. With this you have proven that the addition can be expressed only with primitive functions so addition is primitive recursive. Now that you have proven that addition is primitive recursive you can go on and try multiplication. First ask yourself what is multiplication. It's is just addition performed more times. And this goes on and on from the simplest functions to the most complicated. Hope this helps somehow. This whole topic is kinda complicated and too abstract to get into. But the start is the hardest. I suggest you try to understand these basics maybe try to express subtraction, division and some other simple operations and them move on."
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aaxyfc | How do navigation apps like Waze work without creating new traffic? | Technology | explainlikeimfive | {
"a_id": [
"ecvvyyj",
"ecwbbyo"
],
"text": [
"I used Waze going into NYC once. It rerouted every 3 minutes. This way is 2 minutes faster, this way is 5 minute faster, over and over. It never occurred to me that doing just that, incidentally moving the traffic jam around.",
"> It seems like it’s just giving people a new road to make busy. That's the point. If you are busy in road B, then that's room available on road A. Lets say that everybody is commuting from the subarbs to the city and there are only two roads. Waze will calculate the fastest route available at-the-moment and send you down road A. The next person going to work will use Waze which will now see that road B is faster because you are on road A, so it sends the person down road B. The next person now goes down road A, and repeat. Both roads may have traffic now, but the traffic is split between the two roads. Without waze, road A will have even more traffic and road B would be underutilized because road A is a highway and most people assume that road A is faster."
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aayb2z | Why did controllers in the 80s and 90s require calibration? How come we dont need to calibrate controllers now? | Technology | explainlikeimfive | {
"a_id": [
"ecw15sk",
"ecw039o"
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"text": [
"The way older joysticks were built, the software had no way of knowing where the 'center' was, and how far the joystick could move before it hit max tilt - so it had to measure those values itself. (Similar to taring a scale). These days there are little chips inside the joystick which know those values through factory calibration, and will deliver normalized output to the PC.",
"The only controllers that required calibration were early analog type controllers (joysticks, steering wheels, etc). In many cases they were also user-adjustable via on-controller (I want to call them rheostats but that may not be right). Every manufacturer made devices slightly different from one another also, so the dynamic range of each device had to be determined before you could use it. Digital controllers like the joysticks on the Atari 2600 or the original Nintendo D-pad did not require calibration."
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aaybjv | how do flea collars work? | I never understood how it wards of fleas successfully unless it courses electricity over an animal’s fur. | Technology | explainlikeimfive | {
"a_id": [
"ecvyd5q"
],
"text": [
"There is a pesticide impregnated in the plastic. It’s safe for dogs but poisonous to bugs, cats and other animals. As the bugs crawls on the fur it kills the insects."
],
"score": [
3
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aayu0n | Why do homing missile explode even though it hasn't hit the target? | I've observed this in a lot of movies that a jet is being targeted by a homing missile and decided to increase the speed and do some stunts to dodge the homing missile but then the homing missiles explodes without even touching something. | Technology | explainlikeimfive | {
"a_id": [
"ecw3auq",
"ecw3uiv",
"ecw3h5f",
"ecw5k7i"
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"text": [
"The answer for movies is probably \"it looks cool\" much. However, many anti-aircraft missiles are designed to detonate a short distance away from the target, not just on direct hits.",
"A missile damages the plane by shrapnel as well as shockwave. If the missile thinks it's close enough to the plane, it'll detonate the warhead. Movies are fake",
"Well in movies they do that because its more dramatic. In real life there are a few design philosophies for air-to-air missiles. Some of them will attempt to simply slam into the target and explode inside. That turns out to be surprisingly difficult, though. The other method is for the missile to act like a grenade. Since aircraft are not heavily armored you can do catastrophic damage with fragmentation. This is easier since the missile only has to get \"close\" to the target and then explode. As I understand it many missiles are designed to explode as a safety mechanism. If they go to long without finding a target or find themselves completely turned around (ie possibly pointing at the plane that fire them) they destroy themselves to prevent them from turning into an unpredictable danger.",
"Because planes are fragile and poorly armored so fragments can take them out When the missile is approaching from behind its only seeing a small profile of the plane. You can try to hit the tube that's less than 4 meters wide with a missile less than a meter wide but it'll be hard. If you put a proximity fuse in with a good fragmentation warhead then now you get to try to hit the plane with fragments that are traveling 50-300 meters from the initial explosion point. This greatly increases your chances of hitting the plane. If you're within 50 meters it is going down, and hitting a 50 meter radius sphere is much much easier than hitting a 4 meter radius tube The most produced Surface-to-Air missile is the Soviet S-75 Dvina which had a 250 meter lethal radius at high altitudes, that makes it really easy to hit your target"
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ab0tiy | My Phone Charger | Does a plugged-in wall charger still draw electricity even when it's not charging? If not, how does my phone battery tell it to 'turn on' then? Please explain like I'm 2 yrs old instead. | Technology | explainlikeimfive | {
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"It might use electricity but only an incredibly tiny bit. The way your phone tells it to start charging is by completing a circuit. When nothing is plugged into the charger the circuit is open and no electricity is flowing. When you plug your phone in then the circuit is completed and electricity can flow.",
"It does but it draws a very minimal amount, just enough to keep the circuitry in there powered but without a load(plugged in phone) its going to be using well under a watt of power For a super simple charger, there will always be +5V at the +5V pin so when you plug your phone in it'll start to draw power from that. There is a capacitor that stores energy for this +5V line and the voltage will begin to fall, the switcher controller will detect this and start increasing the power supply output to get back to a nice even 5 volts. For fancier chargers that have something like QuickCharge or USB-PD, the devices will talk to the charger over the data wires to tell the charger what it wants. If the charger doesn't get instructions then it assumes its a dumb device and just provides the basic 5 volts."
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ab16jf | Does my phone check every second to see if the current time matches the time of a previously set alarm so it can trigger that alarm? How are these scheduled events generally triggered? | Technology | explainlikeimfive | {
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"Your phone is literally just a computer. Computers have a piece of software called a scheduler. Schedulers are a fundamental part of the operating system and do way more than simply check for your alarms. They coordinate all of the other software that wants a piece of the main processor's time. So, the scheduler has a list of all of the things that need to happen. If you are browsing a web page while also listening to music then the scheduler allots time on the CPU for each of those tasks. It will also check to see if there are things that need to happen in the future. If a piece of software is set to wait for 1 second before checking on something then it will tell the scheduler that it needs CPU time in 1 second. Similarly, your phone's alarm will be set into the future and the scheduler will notice when the current time matches the alarm time. Since the scheduler is always running and always making sure that things happen on time, an alarm is one of the easier things for it to do.",
"I think a lot of the answers here are a bit misleading. I'm gonna go off the dude that talked about schedulers. This is more of an ELI10 or 15. ELI5 at the very bottom as TL;DR. A [scheduler]( URL_1 ) isn't a complicated concept: it's the piece of software in a modern operating system that runs on top of all other software and gives each running program time to do work on the CPU, called a time slice. From what I can find, this is anywhere from 10-20 milliseconds in Windows. Ignoring things like threads, if your computer has 5 programs running, the scheduler will put each program on the CPU for 10-20 milliseconds before switching to another one. The scheduler doesn't have a concept of much of anything since its only job is to juggle your running programs and give them time to do stuff. How does the rest of your computer know how much time has passed? [A hardware clock generator.]( URL_0 ) This is kind of irrelevant because I assume what you want may be something a little more high level and not how does your phone's operating system play into it. But really, how does the Alarm app on your phone do it? Something like an alarm has a goal, though: use up as few time slices as possible while trying to make sure it goes off at the right time. If you had 100 alarms set and they're eating up all of your phone's CPU and it becomes impossible to use, that's unfortunate. Here's a few ways to implement an alarm. Since I don't know what phone you have (and it really isn't relevant anyway), I'll go with generic things. What an alarm app will do is see if the current time is equal to greater than the time you have set. If you set the timer for 8:00 AM, if the scheduler wakes it up at 8:00:01, it's time to buzz your ass awake. * Set a timer to 8:00 AM. The Alarm app creates a new item in its list of alarms to go off at 8:00 AM. That new alarm is just one in a list of all your existing alarms, all of which are all checked at once: \"Get current time. Does current time satisfy any alarm we have set? If Yes, set it to go off. Otherwise, tell the scheduler to not run this program again for, say, 900 milliseconds.\" It's reasonable if the timer goes off one second after 8:00 AM. *This is a reasonable solution.* * Set timer for 8:00 AM. This Alarm app is badly made. This time it starts up a new thread (independent schedule-able piece of a program) that checks the system time every loop of its code. This is going to take up a lot of time slices since each alarm has one thread, can be scheduled by the scheduler, and will make the CPU do more work than it needs, since it shoves other threads out of the way. Since a time slice may be 20 milliseconds, it's just *not necessary* to check the time every 20 milliseconds, and create a new thread for each alarm. *I'd delete this app and shame the developer.* * Set timer for 8:00 AM. Let's go with the same setup as the first option above but instead of pausing for less than a second, tell the scheduler to pause for 29 seconds. Why 29 seconds? You'll never wake up at 8:01 AM but you could wake up at 8:00:59. Or you could wake up at 8:00:30. Those time slices and other inaccuracies mean your time just might shift if you think you're starting it at 9:00 PM the prior day. This takes up less CPU time than either option above but could make you wake up to what is essentially a minute late. Of course, it's really all superficial: in the end, your CPU is checking every clock cycle directly what time (option 2), or when to wake up a program to check the time (1 or 3). It's just that options 1 and 3 let your computer do more important things. Source: have written applications that check for times to do things. TL;DR: Something is checking every CPU clock cycle: either the alarm app itself or Windows/iOS/Android checking to see if it's time to execute the alarm app's code, which in turn will check. These things are not really *scheduled.* The alarm checks to see if the time has passed, and then the program tells Windows/iOS/Android that it wants to go to sleep for 500 milliseconds, at which point Windows/iOS/Android wakes it up and it checks again. Repeat forever. Windows has a \"Task Scheduler\" app but it works on much the same principle if you set a job to go off at a certain time. The time for your computer that everything else relies on to tell time is kept by the computer's clock generator.",
"it doesn't check every instant if it's time to trigger the alarm, it follows a schedule. When you create the alarm you basically set a new task to do at a certain moment and when that moment comes, it triggers. Just once. What it does every instant, however, is to check this \"schedule\""
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ab28ce | What does it mean when it says music is "Remastered"? | Technology | explainlikeimfive | {
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"TLDR: Processing an original audio recording to make it sound better. A master is the original recording used for an album, usually on Analog tape. Armed with the knowledge that the technology and techniques used in the audio industry have improved over time it's often obvious how to improve a recording. Remastering an album involves cleaning up the audio of the original. Digitizing the analog tape and then applying filters, removing hiss and popping noises from the recording, changing the volumes of the various tracks in the mix and audio channels. You can even fix mistakes in the editing and instrument playing in the recording, although sometimes this is considered taboo when messing with older recordings. Tracks are recorded and mixed to optimize the qualify on formats of the day like Vinyl or Tapes. Remastering a recording can help make it sound better in modern formats like Digital, CD's etc, and through headphones instead of speakers. Modern recordings also tend to be a lot louder sounding than older ones. It really depends on what the studio is trying to accomplish.",
"Mastering in music is where the different elements of the mix are brought together and balanced. Remastered means that they have redone this process. Usually it's with older analog (tape) recordings and they have taken out the hissing and popping that is sometimes present.",
"Remastered also means baaaad. At least in some cases. Pls. see URL_0"
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ab4owo | How is it that games become poorly optimized? | Technology | explainlikeimfive | {
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"It can be anything from sloppy code to non-efficient ways of solving problems. A lot of things can cause performance issues and they can’t always fix all of them. It is extremely case specific.",
"Games companies are businesses. They are actively trying to optimize their profits, and make the most revenue in the most efficient way. & #x200B; Writing highly optimized code is difficult and expensive, but 'poorly optimized' code can be produced much, much cheaper, and will run 'well enough' on higher end machines. & #x200B; In a very simplified scenario, let's assume a game company will spend $1m/year to run its business. (salaries, rent, hardware, utilities etc.) Let's also assume the market for any arbitrary game at a standard price is about $10m & #x200B; Let's consider two 5 year business plans: 1. Release one poorly optimised game per year. The games will only run on high-end machines and will only sell to half the population. Each game brings in about $5m in revenue. That will be $25m in total for the 5 years. 2. Release one extremely well built game that takes 5 years to develop. The game will run well on all machines. It should bring in $10m in revenue. In 5 years, option #1 makes $20m in profits, but option #2 will only bring in $5m in profits. & #x200B; Also, the cost of hardware comes down over time. Today's top-of-the-range machines will be affordable in 5 years. Compare today's entry-level machines with the high end machines of 5 years ago. In a few years time, your poorly optimised game will probably run 'well enough' on entry-level machines. & #x200B; So, with option #1, you can also re-release the games at budget prices, and they can now be sold to the other half of the population, that missed out on the game first time round. Another source of profits, that you don't get from option #2 & #x200B;"
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ab4y4y | i've been watching old VHSs from my childhoods and I wonder how they work. Specifically, when you rewind it, how does it just play the film backwards? What mechanism exists so you can watch the film forward (with sound), and backward (without sound). | Technology | explainlikeimfive | {
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"VCRs record the video in stripes diagonally across the tape. This is done by placing the heads that read the video on a rotating drum, set at an angle to the tape. The video is stored as an analog signal, so even if there are problems with it, you still get a signal. So when you wind the tape backwards across the heads, you still get a video signal. It won't be perfect, however - the angle of the stripes assume the tape is moving forward, so if the tape is moving backwards, the angle is wrong, so each picture on the screen will show part of one stripe, part of another, and part of what is in the gap between them. Now, as for audio - originally, the audio on a VCR tape was another analog, mono signal, placed along one edge of the tape by a fixed head almost identical to an old-school cassette tape head. But users demanded stereo audio, so they instead created a digital audio signal and squeezed it between the stripes of video data. But, again, because the angles are wrong when the tape goes backwards, most of the time the audio heads will be reading video data, which would work out to be full-volume noise if put through the audio decoder. Thankfully, they turn it off to preserve both your ears and your speakers. Of course, they could give you the audio off the simple mono audio track, which would work, but they chose not to do that. It would probably be at the wrong speed, because rewind is normally faster than normal play speed, and would be annoyingly high-pitched."
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ab5gv1 | What exactly are polarized lenses and what makes them "better" than non-polarized lenses? | Technology | explainlikeimfive | {
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"Natural light from the sun or even from a light bulb is radiating out in all different directions and angles. The oscillations are overlapping and chaotic; or what we call \"non-polarized\". The polarizing filter blocks light from all but a very small set of angles so that the only light that comes through are those oscillation that are, for example, straight up and down, or straight side to side. This dramatically cuts down on glare as the eye receives none of the incident or low angle \"rays\" of light (in quotes because light does not actually travel in lines/rays) that you would otherwise see."
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ab6f23 | How is a patient kept alive during a heart transplant? | I imagine that it takes a while to 'install' the new heart, so you can't do the Indiana Jones switch. | Technology | explainlikeimfive | {
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"They use a bypass machine, which puts your blood through a pump that can oxygenate and remove CO2 from your blood.",
"Machines. One breathes for you, one pumps your blood. What I found to be an interesting side-note; a surgeon told me that every person put on heart/lung machines during surgery hallucinates in recovery. Seeing/talking to people who aren't there, etc. I ponder that sometimes."
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ab85gl | How can they go back and remaster old movies in 4K when the technology did not exist when the movie was filmed? | Technology | explainlikeimfive | {
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"The technology did exist back then. 35mm film is closer to 4k resolution and has been used for major films since the 1920s. So basically they sort of did have \"4k cameras\" for over one hundred years. When you see a grainy, low resolution black and white film as a kid, you're seeing an imperfect transfer of that 35mm film to VHS or TV broadcast. Today, we can transfer that copy better, and digitally remove the rips and tears that weren't there originally.",
"Old movies were filmed to film, not digital. When you remaster an old movie, you can just re-scan the old film with a higher resolution scanner. HD is roughly 2K megapixels, 4K is around 9K. My understanding is that with current technology a 35mm negative can be scanned at a maximum of 24 megapixels, so there's still a ways to go."
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aba8od | How do electronics keep memory after you take all power sources away? | When I turn my phone off and take the battery out, how does it remember what all my setting were and then boot up like nothing happened? How can a flash drive that’s been sitting in a garage for 5 years remember what was put on it? I keep trying to think of how it’s possible but I just can’t wrap my mind around it. So how does it keep memory with essentially no way to “remember” since it doesn’t have power? | Technology | explainlikeimfive | {
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"Memory is basically just millions of light switches. Each light switch is called a bit. The bits can be flipped to \"on\" or \"off\" represented as 1 and 0. Eight bits make a byte. A thousand bytes make a kilobyte. A thousand Kilobytes make a megabyte. A thousand megabytes make a gigabyte. When the power goes out at your house, the light switches are still in the position you left them in even though no electricity is flowing through it.",
"Going to try my hand at Flash EEPROM here, since that is what the question is mostly about, phones and pen drives. Imagine you dig a ditch near a river. It stays dry in the beginning, but every once in a while, the river floods and water flows into the ditch. Now, even if the river level goes down, water will stay in the ditch until it evaporates, which can take a lot of time compared to the flooding. If you are in a cold climate, the ditch can stay full indefinitely.",
"There are a couple different ways to store data. Flash is good for long term storage because you store data in it by ramming electrons through an insulator onto a gate. The electrons have no way to escape so they're stuck there until you provide enough voltage to get them off the gate. Since the electrons are trapped you don't need to constantly refresh it and it can hold onto values even without power; though over a long period of time(years) they can escape and you'll start to lose data. We use RAM for short term storage because its fast but loses information when you take power away because it is storing charge in tiny capacitors that slowly discharge overtime and need to be refreshed periodically. When you remove power they discharge to fairly quickly and you lose the data.",
"Lots of people in this thread are missing a fundamental aspect of modern solid state electronics that make physical object movement a bad analogy. This gets into quantum mechanics, so it isnt really an eli5 answer. But it's better than getting an answer that's straight up wrong. This is more of eli15. When you assign something to memory, there is no physical object being moved that you can just look at after the power goes out to determine what was there before. What we do when we write something to what's called volatile memory (that means it has no permanence if power is lost) is we send a signal to allow current to flow from A to B. If the power goes out, we lose that signal and the current from A to B stops. Everything in the circuit is well-grounded, so when you turn the power off, all of the electrons are sucked to the ground (actually to the source, but that's because electrons move in the opposite direction of current. Not important here.) When we re-power that circuit, the signal isn't guaranteed to appear as it was when we left it, because that signal is composed of a current similar to the one from A to B that was interrupted by the loss of power. How can A to B be reliable if its accuracy is dependent on itself already being reliable and you've disrupted it? You can't, is the answer. This is one of the hardest concepts to grasp in electrical engineering. Non-voltile memory has an extra mechanic in place to help prevent this. We can create what's called a \"floating gate\" that can be charged up with electrons to \"lock\" the memory into place. This way, when power is lost and the circuit repowered, that floating gate will provide a force to allow current to flow from A to B. We call it a floating gate because it's not grounded, meaning electrons can't escape it when power is lost. However, electrons have a habit of disappearing and reappearing somewhere else via a process called quantum tunneling. This means that even non-volatile memory won't last forever and requires a refresh every few decades to bring it back up to snuff. This floating gate acts something like a battery to store that one bit of information as long as it can, and there's a floating gate on every transistor that's intended to be non-volatile. If you didn't refresh it, eventually the electrons would tunnel out of the gate and you'd have the same problem as you had with volatile memory. This is also why EMP's are so dangerous for solid state electronics; it gives electrons a lot of energy to go wherever they want, at minimum wiping your memory and at maximum damaging the intended paths for current to flow."
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abayit | Why GPS works on my phone in airplane mode? | On flights I'm able to see where we are on Google maps even with Airplane mode on. | Technology | explainlikeimfive | {
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"Your phone only has a GPS receiver. It only listens to GPS signals, in contrast to wifi or cellular data where it both gets data and sends data. Additionally, even if you turn off airplane mode of course you will still not receive cellular data. GPS signals come from satellites, not towers located on the ground. This is also why, apparently surprising to some people, you can use Google maps and whatnot to navigate without data.",
"Airplane mode turns off transmitters (anything that SENDS a signal from your phone) where as GPS is just a receiver (only RECEIVING signals from other sources to your phone).",
"Airplane mode will block all radiowaves **emissions**... but reception works fine as the phone only absorb radio waves in that case. There are some technologies that only require reception: GPS, AM/FM Radio, and Radio TV reception. Therefore, those features can actually work safely in airplane mode. Although in altitude in an airplane only the first would still be working, as the other ones need to be close to an antenna, typically on the ground."
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abbe8j | What was the Y2K problem, what was the potential outcome, and how was it averted? Will we ever encounter something similar? | Technology | explainlikeimfive | {
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"A real world example: I worked as a programmer for a payroll services company in the late 90's. Part of my job was changing the software that ran the payrolls to use 4 digit years instead of 2. Now lets say your vacation accrual rate, retirement fund deposits, etc. were based on your length of employment. So if you were hired in 1995 and it's 1999, it would calculate your length of employment as 9 9 - 95 = 4 years (way oversimplified of course) and then it would calculate those other things based on 4 years of employment. Without changing to 4 digits years, when 2000 hit, the calculation would be 00 - 95, which would either result in a length of employment calculated as -95 years, or more likely, the payroll software would have just crashed. That would be bad. People's paychecks or direct deposits would not go out, or be delayed significantly while someone tried to either figure it out by hand or rush a software fix - either way it could be several days. This could have legal ramifications for the employers and the payroll service company. Not to mention the chances of you being late with your rent/mortgage, groceries, etc. Not the end of the world, but definitely a major inconvenience. & #x200B;",
"The main problem was when people coded up heaps of control programs in the past they used a shortened date format so 12/12/91 instead of 12/12/1991. This was done to save computer memory when executing code in some cases and in some cases it was lack of foresight. The fear was that when the date ticked over to 01/01/2000 it would be interpreted as 01/01/00 and reset or reverse heaps of transactions in databases or programs would not know how to handle the time change and would crash out in an unpredictable way. As there was a chance these systems controlled everything from nukes to flight control systems people were petrified it could lead to the end of the world. Millions if not billions was spent on new software, reverse engineering old software and patching software to y2k proof critical systems. We all waited as midnight hit across the world for the possbility a bright flash on the horizon and headlines to pour in but here we are in one piece. 👍",
"> Will we ever encounter something similar? We certainly could, in the form of the [2038 problem.]( URL_0 ) Where Y2K was an issue of coding, 2038 is a problem with logic and arithmetic. Simply put, computer processors can only hold so much space, and a 32-bit processor would be unable to store any more numbers after a certain time on January 19^th 2038. However, this is becoming less likely for everyday users and most businesses as more and more computers are built and sold with 64-bit processors, which can hold more space for numbers than there are grains of sand or drops of water on Earth. The **real** issue, as with Y2K, is that systems such as the US nuclear arsenal currently run on computers from the 1970s and 1980s, which can't easily be upgraded.",
"It should be noted that there have bean much bigger date issues in the past. Which was why the Y2K was so terrifying. For example a popular computer in the 80s would handle leap years by deleting every temporary file as soon as it was created therefore rending the computer useless. This was seen as a worst case scenario although it was not a very realistic one. The issue was that a lot of systems used two digit year in their date format. So for example if a sales system would record a sale as happening at 1/1/00 this may be interpreted as 1900. A cleanup script might go ahead and delete the records of all sales older then 10 years so that the database does not grow too big. This would then delete all newly created sales. This was just one of the potential issues that could have happened. & #x200B; There are still critical date bugs happening. Every leap year and ever leap second some computer systems will fail as the software is rarely tested in these conditions. So whenever we get close to a leap year or a leap second is announced people are running around looking through code for date bugs and testing systems for these conditions. Some even go as far as closing business to shut down their systems to avoid issues. There are also some like Google which do not use the correct time during the leap second day so that they avoid the leap second all together. There is a similar issue to the Y2K issue looming over us. The 2038 problem. The issue here is that computers usually use what is known as a UNIX timestamp to simplify date and time calculations. This is a single number which is the amount of seconds since 1970. This number fits nicely in a 32 bit integer number which have been the standard for almost all computers until recently. A lot of systems still use 32 bit integer numbers even though 64 bit numbers are just as fast on modern computers. The issue is that in 2038 a UNIX timestamp will no longer fit in a 32 bit integer. So similarly to the Y2K problem it is suspected that a lot of dates will be incorrectly be recorded as 1970 instead of 2038. There have already been some minor bugs related to this as we need to refer to dates long in the future. However we do not know the extent of the problem.",
"I was the Y2K compliance officer for my work. If I remember correctly, it consisted of a 1 day training seminar, a binder, and a couple of floppy disks. I had to go to each console and patch the OS manually. Took a couple of days, wasn’t very exciting."
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