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a29brh | How do barcode scanners work? | Technology | explainlikeimfive | {
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"It shines a light, the black part of the barcode absorbs the light and the white part reflects it, so the reader receives aback the reflected white parts and is able to read the pattern."
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a29ddk | Why does the Google maps voice sometimes sound normal and then suddenly become robotic? | Technology | explainlikeimfive | {
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"The different noises/letters are separately recorded and some flow together better than others I think",
"It depends on if it's streaming text to speech from Google servers vs if it's coming from your local phone. If you lose your connection or your connection isn't fast enough it'll default back to your phone's tts. Google's servers sounds natural, your phone's tts sounds kinda bad."
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a2cxbb | why is the download speed of a file always less than the speed shown on an internet speed test like ookla? | For example, my current internet speed is roughly 30mb/sec... but my Sims 4 update is only downloading at roughly 1mb/sec. Where does the rest of my internet go? | Technology | explainlikeimfive | {
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"First of all, you're mixing up mega*bits* and mega*bytes*. A byte is 8 bits, and internet speeds are usually given in megabits, while actual download speeds are given in megabytes. So your speedtest result is 30megabits/s, which is 3.75megabytes/s. Additionally your bandwidth is limited by the server's bandwidth. If the server doesn't want you to get more than 1mb/s then it doesn't matter how fast your internet connection is.",
"You are limitless by the file hosts available bandwidth. Many times they limit the speed to an individual user so that it is more fairly spread amongst everyone.",
"When you run a speed test, they try to find the closest possible server & make sure it's on your ISPs internal network. This gives you the absolute best possible results, sort of like taking a car to a race track. When you're downloading things, you've got countless little bottlenecks that add up. The server probably has limited bandwidth to share between everyone downloading from it. That traffic has to go across multiple networks. Your ISP's connection to the network it's on might be bottlenecked. Think of it more like driving your car through a major city where you have speed limits & traffic to deal with.",
"This is a common misconception based on people's lack of understanding of the internet. The internet can be fairly good explained by comparing it to the postal service. The speed you buy from your ISP (the company selling you 'internet access') is roughly the speed you have from your house to their central hub. That's what you're buying. In essence this is kinda comparable to the size of the truck from your hose to the next sorting station of the postal service. Now, just like the postal service there are a lot of hubs between you and your target. It goes from your house to your local villages postal service, then from there it's probably sent to the central hub for your state and the central hub for your state sends it to the central hub for your target's state and then this central hub sends it to the local village hub of your target and then it's delivered to the targets house. The internet is about the same. There are many hubs and paths between you and your target. If any of these paths have a lower speed than what you bought from your ISP then you're automatically capped to that limit. If you a 1Gbps path followed by a 128Mbps path then followed by a 1Gbps path and you send data through this you're going to be limited to that 128Mbps. Also, you're not the only one sending data. If two people send data then you're limited to 64Mbps (assuming they have equal load). If you download something form your average webserver you're probably going to have somewhat around 200-500Kbps and if it's some bigger company behind it maybe 1-2Mbps. That's because even though they have 1Gbps line right at their server you're not the only one using that server and there could be a slow path inbetween. This is almost the full story. You're not only limited by the bandwidth of the server you're limited by the bandwidths of every path that your packets travel through. The bandwidth is also not entirely determined by your physical line because you could have a 1Gbps line but you're behind a router/switch that can only handle 128Mbps or maybe your network card can only handle 128Mbps. People genuinely buy 1Gbps connection for their private home but then use the router that comes for free with it that can't handle 1Gbps. Also keep in mind that packets get routinely lost you just don't notice it because we've developed smart network protocols that resend lost packets but packet loss is also going to influence how much data you can send through a path. If a path is overloaded the switches/routers will start throwing away packets because they have to temporarily store packets for routing and they can only store a limited number of packets. Also, the downloading software also has an influence on how fast you can download things. You can have multiple connections open to increase download speed (but that depends on how loaded the network path is). There are cooperation protocols to not overload network paths because if everybody was egoistic and would just always try to max it out it'd collapse and everybody would get much worse speed than when everybody throttles speeds a bit."
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a2e421 | Why are electric cars more eco-friendly if electricity is still fossil-fuel powered? | If a normal car burns gas, I get why that's bad for the environment, and an electric car doesn't. But doesn't the power that charges electric cars still come from power plants that also are bad for the environment? How big is the difference in pollution? | Technology | explainlikeimfive | {
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"> But doesn't the power that charges electric cars still come from power plants that also are bad for the environment? Some of it, sure, but not all. But, even if all power was produced from fossil fuels, it's still much better to have those fuels burnt at a large, central power plant than in a tiny engine in a car. A power plant can be much more efficient in converting fuel to energy than a gas-burning car is. Also, it's much easier to trap pollution at the power plant than coming out of your car's tailpipe.",
"Not all electricity generation is powered by fossil fuels. You would be hard-pressed to find a grid which doesn't have *any* renewable energy contributing to it so there is that aspect. Another issue is that efficiency and pollution produced by automobiles and power plants are not equivalent. Power plants can focus on burning their fuel in the most productive manner, and filtering the pollutants out of the exhaust in the best way possible. Automobiles however need to worry about weight as they are trying to move the engine and exhaust system around, meaning they need to make sacrifices in some areas. Finally there is a difference in *where* the pollution is deposited. Power plants tend to be placed outside of dense cities and have tall towers from which to exhaust their waste products, hopefully beyond where people are going to be breathing. Automobiles on the other hand by necessity must dump it right out at ground level, in concert creating the city smog which causes so much trouble. Even if electric cars resulted in exactly the same amount of pollution being produced and released (which they don't) it matters very much to the *local* environment in which people live.",
"That is why we should start moving away from power plants that pollute. Wind, solar and nuclear powerplants have zero emissions when operating with the exception of used fuel rods from the nuclear plant. But when those are properly stored things are fine.",
"Generally, electric cars use energy more efficiently than petrol cars. Also, coal and natural gas power plants usually implement expensive processes that clean up the by-products of burning fossil fuels before releasing the exhaust into the air. Petrol cars would be far too expensive if similar measures were implemented in every car so they tend to pollute heavily.",
"Bigger generators are more efficient than little generators. Coal burned in a big power plant is about the only fuel that has worse emissions per kWh than gasoline burned in a small engine. Your car engine has an efficiency of ~35%, the absolute best coal plant using the perfect coal can hit 43% but still has all the icky stuff from coal exhaust Compare this to combined cycle natural gas which can pull off 60% efficiency and you can see that if you get your power from a natural gas plant you'll avoid a lot of emissions(almost half), and in the long run power gotten from Wind and Solar are effectively zero emissions. As the US is currently in the process of retiring coal plants or swapping them over to gas, odds are your electric car will just be more and more environmentally friendly over its lifespan."
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a2ewfd | How do prosthetic arms work? | How is a person able to move a hand and even the fingers of a prosthetic? | Technology | explainlikeimfive | {
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"Hi there! I'm a prosthetics student, so I'm happy to answer this one! It's important to remember that there are various levels of amputation. If a person is missing fingers, there are devices that can be controlled by the remaining fingers. If someone is missing their arm past the elbow, there's still some forearm that can be used to control the prosthetic. With amputations above the elbow, you have an entirely new joint to worry about with loss of elbow movement. And finally, with someone missing an entire arm, it is very difficult to make a useful device for them, and many people with that level of amputation will not use a prosthetic. First, there is a socket, which is the laminated carbon fiber or plastic custom-shaped interface with the residual limb (a.k.a. stump). The fit is important for comfort and making sure that the prosthetic arm will stay attached to the body. It's attached to the hand components, which may be controlled in various ways. Currently, there are two main methods of controlling a prosthetic hand - myoelectric (fancy word for muscles controlling a prosthetic that has to be charged) and body-powered. You can find out more here: [ URL_1 ]( URL_1 ) Like aragorn18 described, the myoelectric prosthetics pick up signals from your skin to calculate how the hand should move. However, it isn't directly taking signals from your nerves. Go ahead and wiggle your fingers, looking at your forearm. Most of the muscles that open and close your fingers are located in the forearm, meaning that if there is some forearm muscle left, sensors can pick up the electricity of muscles moving and determine how the hand is meant to move. For body-powered, it's fairly common for an amputee to have several different types of prosthetic devices for different activities. Prosthetists (not doctors!) can make rock climbing arms, arms good for pushing a wheelchair, and more. Many of these look like several hooks and are not very cosmetically appealing although they are effective. These take less training to use. Bending the elbow might close the hand, or maybe flexing the wrist backward would open the hand. It totally depends on exact location of the amputation. 3D-printed hands (usually used for kids because they outgrow everything so gosh darn fast) are an example, although they can be myoelectric too. Keep in mind that 3D printing is not the standard in the field yet, and may not ever be because it is generally not as strong as metal and other materials. Here's an example of a body-powered 3D-printed hand! [ URL_0 ]( URL_0 ) Hope this helps!",
"The nerves that would control your limbs are often still intact after an amputation. Doctors can put sensors on the skin next to those nerves and pick up the impulses when you want to open your hand. The prosthetic has a computer in it that reads that signal and opens the hand on the prosthetic."
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a2gb3u | How are old songs like "Here comes the sun" remastered? | Technology | explainlikeimfive | {
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"It depends on how it was mastered in the first place. And frankly, there isn't a strict definition of the word \"remaster\", so it really means whatever the marketing department says it means. In the old days, you recorded through a mixing board directly to 2-track magnetic tape to create the stereo music. Once that's been done, there's not much more that can be done to the music. The magnetic tape was then used to create a \"master\" record which was then used as the original to create one or more molds, which were then used to stamp out more records. Eventually the molds wear out and new ones need to be made. This in turn causes the master record to wear out. So remastering could consist of simply digging out the old tapes and making a fresh master from them. Maybe modern audio processing techniques could be used to improve the audio quality while you're at it. More likely, \"remastering\" means using the original magnetic tape to make DVDs and MP3s directly, skipping the entire messy process of making vinyl records. This would produce much cleaner results than simply grabbing a copy of the old vinyl record and digitizing it. Now, if your original studio master was a multi-track tape, then you also have the options of processing the different tracks separately, and of re-doing the mix entirely (assuming you can do a better job than whoever originally mixed it.) Fun fact: when the Muppet Show did their [Bohemian Rhapsody parody]( URL_0 ), Queen loaned them a copy of the original 24-track master so that the Muppet show could simply put their own vocals on top of the original music.",
"The recording studio still has the the original multitrack recording or unmastered mix of the song and simply they re-do the mastering process. If they have the original multitrack tape, sometimes they will also re-mix it before re-mastering."
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a2h2ze | how do self checkout machines ensure that customers aren't stealing items or taking things by mistake when scanned incorrectly? | Technology | explainlikeimfive | {
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"They've calculated risk. Essentially, people are generally trustworthy and scan all items. If there is an issue they wave down the assistant. For the few people who do steal stuff, the expense of the stolen products is calculated into the price of the food. So people who follow the rules pretty much subsidize those who are taking advantage of the low security, self check out system.",
"Some have a scale that registers when you put something in the bag without ringing it up but they are slow and glitchy. Most don't have any way of knowing except for the attendant.",
"A bunch of ways. First, the bagging area is actually a scale so if the weight doesn't match what was entered/scanned, it will not let you continue. In the UK, scammers worked around this by [buying avocados but entering the code for carrots]( URL_0 ). Presumably the used traditional monitoring and enforcement methods to determine who was scamming and to build a case against them.",
"As the others said, the machines don't know. Attendants are watching though and will randomly check customers who are done ringing their items up by asking to see the receipt + what they have in their bag. That way the can see if items are missing from the receipt. Nothing is preventing people from stealing things inside the store either by putting it in their pockets, except for the risk of getting caught. It's basically the same thing with self-checkout.",
"There may be systems in place that weigh the items or which can detect if certain resonant magnetic strips placed on high value items leaves the store without being scanned. They may also call out for random controls. But overall it is a calculated risk that the shop is making. There will be more theft on a self checkout line then on a regular line but you only need a fraction of the staff so overall the shop is saving money.",
"It weighs to see if an item was placed in after scanning and then comparing the settled weight to an acceptable limit."
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a2i9v7 | If I text my friend and immediately see it pop up on their screen, how far has that text gone to get there? To space and back? | Technology | explainlikeimfive | {
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"Almost certainly not to space, that takes too long. It goes via radio to the nearest cell tower, then by fiber optic line to your cell company, then via data link (probably not the Internet) to your friend's cell company, then by fiber optic to their cell tower and then radio to your friend's phone.",
"Cell Phones rarely send signals to satellites. Normally it goes from your phone to the tower, then it is processed and either sent via telephone line to another tower and broadcast or it is automatically rebroadcast to at the same tower and sent to your friend's phone.",
"It's not a satellite phone. It doesn't go to space. Your cellphone signal goes wirelessly to the nearest tower, then passed along to a centralized system, processed, then sent to the recipient. Actual total distance will depend on how far away the tower is and how far from that tower to whatever server system is doing the \"thinking\" A GPS uses a satellite signal but it's one-way, it only has to *see* the satellite to locate you on the map. Cellphone geolocation isn't done by GPS either, it's done by proximity to towers, and it's good enough to tell you when to take the next left.",
"If your friend has the same carrier as you: Your phone > Tower > Base Station > Tower > Your Friend if it is a different carrier: Your phone > Tower > Base Station > Internal network > external network (his carrier) > base station > tower > your friends phone cell phones do not use satellites for the most part, satellite communication is expensive",
"12+ years as a telecommunications engineer in the US here. It depends on a few things. Which technology does your carrier use to send the message 1x/evdo/lte? All are similar but different elements and different protocols. Is it an IMS message or regular sms txt? Is it same carrier or intercarrier? In general at a high level, when you send an sms it's transmitted from the field devices (base station, eNodeB, MME, SGW) to the core elements and eventually to the SMSC platform. if it's intercarrier it's transmitted as an SMPP message out through the intercarrier gateway which is an intermediary between carriers. We don't want other carriers to have direct access to our network and they don't want us to have access to theirs so we mutually agree to use a 3rd party intermediary to route sms/mms/data traffic. Once the sms is forwarded out this gateway it's considered delivered from the sending carriers perspective, regardless of what actually happened to the message once the 3rd party received it. This is the point where it would show delivered on your phone but in actuality that may not always be the case. If it's intracarrier the SMS is forwarded to the SMSC that's geographically closest to the destination customer. At this point, the SMSC attempts to deliver the SMS by sending pages to the device to wake it up. Once the device sends back an acknowledgment the download is initiated and the device receives the message in reverse order through all of the network elements. & #x200B; I know others have mentioned that the message is broadcast at the local cell site. I won't say that they're wrong but I can tell you that's not how the top tier carriers do it in the US. All sms records are stored in a central database within the core for multiple reasons. The messages are not just re-broadcasted locally at the cell site. & #x200B; Edit: I always wanted to mention that we don't use satellites in any way. We use fiber, T1 lines and microwave throughout the network. Using satellites would cost too much in latency. Technologies like VoLTE are extremely sensitive to latency.",
"If that was the way signal worked for cell phones..... The distance from the surface to the earth to a geosynchronous satellite is approximately 26,200 miles. So if the signal has to only travel up and then down once, the total travel distance is 52,400 miles. Geosynchronous orbit is when a satellite orbits the earth at the same speed the earth rotates. This keeps the satellite in the same position relative to earth at all times. However, to put the speed at which data travels into perspective, satellite internet has an average ping rating of 750 milliseconds. Which means you can transmit a signal to the satellite, have it sent back down to the providers station, have the signal sent back up and then back to your location all in 750ms. That is a total of four trips,104,800 miles in only .75 seconds. Source (am satellite technician) Edit - tried to math while high",
"If your friend lived in another country then it still wouldn’t go via satellite, rather undersea fibre optic cables. Communication via satellite is much slower as it can take as much as a second or two for a signal to be sent, compared to fractions of a second for fibre optic cables. The reason for this is that the distance to travel are much shorter with undersea cables compared to a satellite and back. If you were on a phone call the extra delay of satellite communication would be very noticeable where as there is very little delay usually for international phone calls. The only time you would use satellites to communicate is in remote areas where there are no nearby cell towers."
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a2kiyu | Why do phone manufacturers let their customers set the date and time on their phones to before the phone's manufacturing date? | Technology | explainlikeimfive | {
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"Why would they put even a second of thought or effort into preventing that? There is no harm in doing that. It doesn't hurt the device and there is no reason the company would care.",
"There are standards in the industry for timekeeping. I can't remember how this one goes but pretty much it started at all 0s, and counts up by 1 for each second that's passed since I think January 1 1970... Probably wrong on the date but if you Google \"the 2038 problem\" it's about this specific timekeeping standard. Anyway, they pick a particular standard and just use it because it works, no need to reinvent the wheel. And by having some standardised timekeeping function it's easier than having to program the Date of Manufacture into all the chips as they're made because you have to keep changing the programming all the time, better to just use a standard format and allow the phone to update itself when it connects to a tower for the first time.",
"Why not? To make the impossible you need to store the manufacturing date in the cellphone and to my knowledge it is not stored in the as it is not needed for anything. You could add some code so you could snot the time to before the date of the compilation but that is extra work. Android phone are based on Linux that used UNIX time stamps as system time. That has the 0 as 1 January 1970 and measure time in second from that so that is the it the earliest date you can use on android. MacOS is based on BSD that is UNIX and iOS is based on MacOS so I guess that the same format is used on that OS. So the date limit might be the same but I don't have a device to test it on. The max yeas in my phone is 2037. It is 32 bit android and the max date for a 32 bit signed timestamp is 3:14:08 on 19 January 2038 but the code is stops at 2037 likely because it is simple to use limit it the the last year where all days can be selected so you do not need to check for max and min. I suspect that the code look at what date timestamp of 0 is and one for max of the type of the timestamp. For 64 bit android the max date is in 292 billion years so you might be able so scroll the date as long as you like or the limit might be year 9999 if there is a 4 digit limit. So the codes hade make one simple way so you can set a valid year Any limit to manufacturing or complication date of the code of the code complicate thing and add code interdependence and is deemed unnecessary. Computer usually do not have a date limit either and cellphones is computers.",
"Testing. Every feature in a phone must be tested to ensure it works. And a feature which changes based on the date of manufacture is hard to test. The automated tests may be created (and tested!) on simulators long before the final hardware design is complete -- and you don't want to have to update the tests as your ship date slips, or because your phone happens to go through yet another production run. Also one set of software may run on multiple hardware platforms -- and so you'd have to vary your tests based on what hardware is being tested on that day. That's a pain, for a minuscule gain. Not worth the trouble."
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a2lhrc | How does the Emergency Call feature work? | Technology | explainlikeimfive | {
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"Most phones will allow a user to bypass log in/unlock screens of a phone to open up a dialer window that is only allowed to connect a small set of phone numbers, including emergency services."
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a2lp09 | How do Asian keyboards work? | just a quick google translate says this is "the house" in japanese 家, so they use symbols instead of words, but you couldn't put all these symbols on a keyboard so how does it work? | Technology | explainlikeimfive | {
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"Specifically Japanese - Each kanji has a pronunciation that can be romanized. For example, \"egg\" is pronounced \"tamago\". So, I type in \"tamago\", then press the space bar to convert. If there are multiple kanji with the same pronunciation, when pressing space, you get a list to choose from. Step 1: type \"tamago\" - this is autoconverted to たまご (hiragana - Japanese characters) Step 2: press \"space\" Step 3: select character that is appropriate for your context URL_0",
"In Chinese there is the Pinyin system which represents the pronunciation of the character. After typing the pinyin, a variety of different words will pop up and you just choose the one you were looking for.",
"By using a system thats bound to the pronouciation or writing of that symbol Latin based languages is mostly pronouciation based. The letter makes the sound. Korean is also pronounciation based. As is katakana script in Japanese. But suppose you wanted to encoded writing without knowing how to say it. You could categorize letters and words by how they're written. Small a (in normal writing) is a circle with a right side tail. b is vertical line then left open sided semicircle. c is a right open sided semicircle. d is a right open sided semicircle then vertical line. Etcetc. Semicircles, verticals, horizontals, left sweeps, right sweeps, down sweeps, ups sweeps, left hooks, right hooks.",
"Add on question... how does the speed of typing compare to typing in English? From the previous comments it sounds like it would be slower but I am curious."
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a2m98r | RAW image format. How does it capture more data than what the pixels in the sensor see? | Technology | explainlikeimfive | {
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"It doesn't capture more data, it holds *exactly* the data that the sensors can see. When the camera (or any other software) converts the RAW image into an actual image format such as JPG or PNG, it actually has to discard some information. For example, each pixel in the camera has a filter so that it only captures one color (red, green or blue). When converting to a usable image format, an algorithm called [demosaicing]( URL_0 ) is performed in order to get an approximation of the actual color of each pixel. This process loses some of the color information from each pixel.",
"It doesn\\`t. But what it does is storing the image with alot more data than for example a jpeg. A camera sensor can \"see\" alot more colour than the human eye. (Not to be confused with seing a wider dynamic range of light) Then the camera stores the \"colour\" so that we can take advantage of the range of colours in editing."
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a2tzkz | What is a DNS record composed of? What data can it store? | Technology | explainlikeimfive | {
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"Your question didn't make clear if it was about what goes on the wire or what is defined on the name server. On the wire, there are requests and there are replies. Requests only had the requested label and some basic options in it, modern requests also have a bunch of options it which could be of importance of the answering name server to answer the question. One of these new options can be \"I'm located in Australia\", so that the answering name server knows the return information most relevant for Australian users. The label is the thing which is requested, for example the name \"www. URL_0 \". The basic options are which protocol to us (yes, this was designed in the time before the Internet Protocol overtook everything and you had different protocols on the wire) and what the request is for (an IP address or a mail gateway or a something else) Replies have more things in it: It has the requested label in it (the \"www. URL_0 \"), it can have an answer in it (Either a real answer for the request or a \"you should ask these name servers\" referral), it can have a \"these servers also know all about this\" in it, it can have some extra information in it (\"I told you to talk to these others servers, here is their IP address\"). On the server, each DNS record consists of various fields: - A label, for example \"www. URL_0 \" or \"4.3.2.1\" or \"_ldap._tcp. URL_0 \". - A protocol, these days it's all \"IN\" from Internet but in past you had different protocols. - A record type, A for an IPv4 address, A6 for an IPv6 address, MX for a mail server, TXT for a text record, SRV for a service record etc. - A time-to-live, the maximum time the answer for this request can be used by others. - And an answer, which format depends on the record type. Some examples in BIND format: www. URL_0 IN A 3600 1.2.3.4 URL_0 IN MX 7200 mail1. URL_0 10 The first one is the A record (address) for www. URL_0 , with a TTL of 1 hour and the answer 1.2.3.4. The second one is MX record (mail server) for URL_0 with a TTL of 2 hours and the answer of mail1. URL_0 which has a cost of \"10\". Enjoy your travels through DNS land, it's very exciting."
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a2uuu6 | How do football clubs know who in a stadium has committed an offence in order to ban them? | As in [the man being banned from Tottenham games for throwing a banana at a black player on the pitch]( URL_0 ), and numerous other incidents of people being banned from football grounds for offences including shouting racist/homophobic abuse and throwing things on the pitch, how are the clubs able to find and identify who amongst the tens of thousands of spectators committed the abuse in order to ban them? They can't have cameras pointed at all areas of the stadium in enough detail to know who did what, or be able to hear who shouted what, surely? | Technology | explainlikeimfive | {
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"CCTV surveillance and a security staff. There is usually at least one guard per section watching the crowd."
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a2xnw7 | How is it when you’re using something that uses two batteries and it starts to go dead you can switch the same batteries in different slots and I’ll give your electronics more battery life? | It’ll* | Technology | explainlikeimfive | {
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"Two reasons: 1. Removing and reinserting the batteries cleans some oxidation off the contacts, improving the connection. 2. Handling the batteries heat them slightly. Household batteries rely on chemical reactions that work slightly better at higher temperatures. Switching doesn't do anything by itself.",
"THe act of taking the batteries out and replacing them will improve the electrical connection because it abrades the ends of the batteries slightly. Same principle behind taking out and putting in old game console catridges to make them play properly. The old blow on it part did nothing except maybe accelerate corrosion due to moisture in your breath; it was the physical scraping of the connections against one another that improved the connection and fixed things.",
"So there are a couple things that I havent seen posted yet. There are a lot of reasons this could be happening depending on whether the batteries are connected in series or parallel with the circuitry. Parallel batteries should be matched as best as possible by brand/capacity/etc, batteries that are in series are a bit different and the life impact of mismatching are less than parallel batteries. If you have a device using series-connected batteries and it dies, when you swap them you are changing which batteries are being discharged/charged more aggressively. Often times in systems that have 2 series batteries, they are referred to as \"upper\" and \"lower\" batteries in the strings. The \"upper\" battery is usually the one that dies faster, so switching the upper and lower batteries could definitely add \"life\" to your device by having the battery that was discharging less become the battery that will be discharged more aggressively. Hopefully this makes sense and helps. & #x200B; Source: Electrical Engineer working in battery research",
"And how comes that every human instinctively shuffles the batteries first? It's amazing!",
"Just turning it completely off will often do this. As a device is using power, the chemicals near the terminals gets used up first. There is often a little bit of that chemical further away, but it can't migrate to the terminals fast enough to keep the device running. Disconnect it, and a bit of chemical can migrate closer to the terminals, so the battery voltage goes back up and you can use the device for a little time. But the effect isn't that great. There's not much active chemical left in the battery, so the voltage will drop away quickly.",
"Taking out batteries and putting them back in the *same* slots will usually give your electronic device a bit more life. If you were to do a controlled experiment I think you'd see approximately the same results whether you switched slots or not.",
"Electronics usually don't \"know\" there are 2 or more batteries but simply sees/senses 1 battery, this is the first battery in the circuit which takes the largest load /toll on it, this means while battery 1 is almost empty(say 10%) battery 2 still has some capacity left(say 15%). This among other reasons contributes to new life when swapping places.",
"What about putting the batteries in the refrigerator? I remember doing this as a kid to magically get a little more life out of batteries. Was that a placebo effect, and the terminal cleaning theory was the real reason it seemed to work?",
"I didn't see this in the top answers, but I _think_ by \"changing slots\" OP didn't mean simply taking batteries out and back in (although removing rust or dust might give a strong connection with less resistance and thus yield some more current before the batteries die). If by \"changing slots\" OP meant re-using the same batteries for different devices, then the explanation is a lot more logical: - Most AA batteries have a 1.5V rating when full, so two AA batteries in series will give a 3V tension. -Different devices require different minimum tensions to work. I don't know the exact values, but I'd expect a Wii remote to need ~2V to work, and a small mechanical clock to need ~1V. - What happens when you power the wii remote is you will deplete the batteries from the 3V initial tension to 2V. The wiimote's battery indicator is calibrated to tell you the battery is full when its tension is 3V, half-full when it's 2.5V, empty when less than 2V because it cannot operate anymore. - Then you may take out the batteries, and even though they are 'dead' according to the wiimote, they can still power less demanding devices! So put them inside your mechanical clock, and it will run for a very long time since 2V means that the batteries are 'half-full' according to the clock!"
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a2xqmw | How is it that ads play well on mobile apps even when the internet is spotty? | Technology | explainlikeimfive | {
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"They are preloaded I think? They do the same on Instagram or FB even when I have no data or Wi-Fi enabled. But I'm sure someone has the actual answer for you.",
"There are different types of advertisements depending on the developer and the advertising network. When there is no internet connection, the app shows the preloaded advertisements(downloaded along with the app itself), which are of the main sponsors ( if you are offline you can notice the same advertisements playing back to back ). Note : Different developers have different methods of handling this, some won't show you advertisements when you are offline, while some will, as a push for the clients to upgrade to the paid versions. Edit : Beyond a certain threshold, spotty internet is treated as offline."
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a30t9l | Why do hard drives need to be formatted before you are able to store data on them? | Technology | explainlikeimfive | {
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"There are a bunch of possible ways to lay out files on a drive. What formatting does is mark the drive as using a specific layout and write a bunch of bookkeeping data to the drive that's needed for that layout, so that when the operating system goes to look up files, it finds the information it needs to be able to say that the files do or don't exist."
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a31nfr | Why do satellites need periodic adjustment to stay in orbit but the moon does it just fine on its own? | Satellites (and the ISS) have their own propulsion and fuel and occasionally fire their engines to adjust position. When they run out of fuel or their engines otherwise fail, they eventually crash to Earth. The moon has no engines and has been up there for thousands of years. What gives? | Technology | explainlikeimfive | {
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"Because satellites and ISS are on the edge atmosphere, so there is some resistance from atmospheric particles that slow them down over time.",
"And the moon doesn't have to be accurately set at a specific position. In fact the moon is on average, slowly moving away from us every year. The moons orbit can vary by many, many kilometers during year, a varition to that degree is unacceptably large for something as precise as a communication sattelite.",
"> been up there for thousands of years. Billions. But as /u/blackwe11_ninja noted, it doesn't suffer significant drag from our atmosphere.",
"The moon is moving one and half inches farther away from us each year. At the same time the planet's rotation is slightly slowing down. So it is not perfectly stable. Eventually both the Earth and the Moon will get engulfed by our Sun as it expands during its own death. That won't happen for a LONG time so don't worry."
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a32y8m | Why is it that YouTube never struggles to stream an ad whether it be 5 seconds or 3 minutes when there is bad connection, yet my videos struggle to stream. | Technology | explainlikeimfive | {
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"Ads are hosted on different servers, better infrastructure, and are usually located closer to you than (most) videos you'll watch. More popular videos like new movie trailers, giant viral hits, or trending stuff that Google wants you to watch may also be hosted on those servers, but Ads are always 'gold tier' because they drive revenue.",
"YouTube servers aren't just in one location. They have bunches of smaller server locations scattered around the world so if you want to view something you don't necessarily need to have it brought out of the central archives across the world. Instead the most popular stuff is kept cached in local nodes where they can be delivered to you very quickly. While a lot of people will be viewing the most popular videos there is other traffic which is entirely unpredictable. Perhaps whatever video you wanted to see is located across the world and that takes time to access. Advertisements however are usually locally targeted, making the most of advertising dollars, which means they are going to be present on local servers. *Everyone* gets the same sort of ads in their videos while the actual content of the video might be anything and take longer to be found. To make an analogy imagine you come to an auto parts store. They have many racks of thousands of different parts behind the counter and a computer to look them up. When you ask for an arbitrary piece the employee needs to find out where it is kept and go get it, which will take some time. Depending on where it is it might take quite a while. However this store also has a stack of fliers which is kept on the front counter. Everyone gets a flier with their purchase so it is kept handy, and there is no mystery why it is always quick to access compared to other parts.",
"Youtube has a rather intelligent structure where the most viewed videos are stored on different servers with more capacity. Naturally, Adds are also on these high performance servers, its not only money, but virtually every user gets to see them. It makes sense for them to be there. The content you want to watch, has a very real chance of not being on these servers",
"On the contrary, even the ads load badly for me on a bad connection. Sometimes it takes like 5 minutes to get past a 15 second ad because youtube forces them to load in 1080p HD. When I can only stream 480p buffering here and there. It's why I don't do YouTube on my phone. Ad block is a necessity",
"I'm OK with them advertising, what I hate is how the volume all of the sudden gets cranked during an ad. No I don't want to dl your meditation app when you just made me jump from the sudden explosion from my speakers!",
"I finally installed an adblocker when I got one of those \"skip in five seconds\" ads and it froze when there was one second left.",
"Because of CDNs (content distribution network). Content providers (companies like Netflix) use CDNs to intelligently store data at network edge nodes to reduce overall internet backbone traffic. Not everyone that uses your CDN edge node has watched the content you're trying to view, but I guarantee someone at some point has already watched the ad video before it, thus it remains cached on your local CDN node and easily accessible. The more popular a piece of content is, the more likely it is to be cached on a CDN edge node, thus the more likely it is that it will load quickly for you.",
"Just to add.. I’m mainly talking mobile. I also have adblocker on my computer.",
"I can load a 4 minute ad in 4k while roaming instantly. But can't get enough data to open the gps."
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a36qyh | When close to burning out, why will a fluorescent tube struggle to illuminate for long periods of time then work fine once it has started? | As title states | Technology | explainlikeimfive | {
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"A fluorescent tube works by having an electric discharge through mercury vapour. That doesn't happen immediately on turning on the power. Instead the starter rewires the power through two heater filaments at the ends. After a delay the switch opens and puts the voltage through the tube. If the discharge strikes, then it stays that way. If not, the starter recycles through the sequence until it detects the discharge."
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a37mbv | When did IP addresses change to that new format and how does it work? | Did an IP Config tonight and instead of the old format of [123.123.123.123]( URL_0 ), I've got something that looks more like a MAC address. When did this change? | Technology | explainlikeimfive | {
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"That’s IPv6 (as opposed to the familiar IPv4). The standard has been around for quite some time and is slowly gaining traction. Most infrastructure anymore can route both, and you’ll sometimes see both addresses for your hardware. The big advantage of v6 is that allows for many, many more IP addresses than v4–we’re actually on the brink of running out of assignable v4 addresses. However, it’s pretty difficult to get the entire Internet to change over all at once so it’ll take some time.",
"IPv4 is 32 bits, with each of the numbers being 8 bits (in decimal, that's 0 - 255). IPv6 is 128 bits, 8 fields of 16 bits each. So each number would be (0 - 65535 in decimal), but it's easier to express 16 bits as a hex code, so that's why it looks like a MAC address (which is also a hex code). Ultimately, they made the IP address have more bits, so they can express more addresses on the internet. Cause they were running out.",
"The old format that looks like 192.168.242.128 is called IPv4 but poses a problem for the internet because it only has ~4 billion unique addresses and there are a bunch of reserved blocks The new format that looks like 2001:0db8:0000:0042:0000:8a2e:0370:7334 is IPv6 and supports 2^128 addresses. It was created back in 1998 but rolled out very very slowly through the years. There was a push in the late 00s to switch systems over to IPv6 and that's been rolling out for the last decade. Generally local networking still occurs with IPv4 addresses because they're nice and human enterable, but your modem will have an IPv6 address from your ISP so they can support tons of devices in their subnet without needing to worry about running out of addresses",
"Others have answered this correctly, but also it's worth noting that your ISP deserves a pat on the back for rolling out IPv6. This isn't such an easy process and in many cases there's no immediate benefit to them until enough of the Internet has switched it on. We're really heading towards a crunch in terms of running out of unused IPv4 addresses. In the last few years a secondary market has emerged where networks are selling addresses to each other - there's some big money changing hands. A single IP address can go for as much as $20 USD these days. We're even seeing people stealing addresses to sell them on the black market! APNIC publishes a map showing per-country IPv6 deployment levels - still a long way to go until IPv6 is the dominant protocol on the Internet: URL_0",
"As /u/ryschwith has already mentioned, the new \"format\" is IPv6, as opposed to IPv4, which is what you are already familiar with. An IPv4 address is four bytes long. The typical notation is four decimal numbers for the four bytes, separated by dots. IPv6 addresses are 16 bytes long, and usually written in hexadecimal, separated by colons. Because the addresses are so much longer, they're usually abbreviated to remove most of the zeros. So, if a full IPv6 address looks like this... 1234:0000:0000:0000:000a:0031:8052:0123 ... the abbreviated form looks like this. 1234::a:31:8052:123 Notice, `000a` becomes `a`. Also, the three groups that are all zeroes are simply replaced by `::`. IPv6 also redefines which addresses are special. In v4, the address `127.0.0.1` is the \"loopback\" or \"localhost\" address, and always refers to the local computer. In v6 the loopback address is `::1`, or all zeros with a one at the end."
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a37qz8 | How fo radio stations transmit text (title of station and song) to cars through FM/AM radio waves? | Technology | explainlikeimfive | {
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"text": [
"There is a low bandwidth digital signal broadcast by the FM station. It is outside the audible range. It only carries around 1200 bits/second, but that's enough for title, artist and call sign. It is called the [Radio Data System]( URL_0 )"
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a3ad6j | How does cartoon animation work? | Technology | explainlikeimfive | {
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"text": [
"That was mostly how old-school animation worked. There were some shortcuts like having a static background, and then drawing the character movements on a transparent sheet above the background. (That's why in old cartoons, you can tell the difference between background and moving characters). These days, with computer animation, they can draw keyframes and have the computer kinda \"fill in\" every frame needed to get from one keyframe to another. That helps. But it's still a very time-consuming process. You can also build basically a video game engine, and program your characters to move how the director wants. Then, because you don't have to respond to a player's input, you can devote a lot of resources to rendering each frame, so you can achieve much more realistic graphics than even the awesome videogames we have today.",
"They used to. It's called frame by frame animation. Nowadays most 2d television animation is made in programs similar to or in Flash, where you can basically pull and move the drawings themselves and apply rigs to the limbs and other objects. You still work by frame but in a different way. But frame by frame is still used in 2d animated films afaik, even though those are rare now sadly."
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a3andn | How are earbuds and headphones able to make music / audio sound like its coming from inside your head? | Technology | explainlikeimfive | {
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"text": [
"So you have two ears, right? And sound is actually pretty slow, you can see it when someone claps on the other side of a road and you hear it only a moment later. So what your ears do is they check if a sound comes to one ear earlier than the other. That happens completely subconscious. The ear that hears the sound first is closer to the source, and your brain then calculates the direction the sound came from. Also, some wavelengths are blocked by your head, so don't reach your other ear at all. and the shape of the ear can also help determine if a sound is above you, behind you, or in front of you. So when the sound arrives in both ears at the same time, and all wavelengths still arrive in both ears, and there is no distortion from the surroundings or your head/ears, then where does the sound come from? Inside your head? The brain doesn't know, it's not prepared for this."
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a3c7ue | Where does that money go when an online transaction fails and the amount is debited from one side but is not credited on the other side? | Technology | explainlikeimfive | {
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"text": [
"It stays with your bank. Real time transactions are between banks and banks, and no \"money\" but the \"amount\" is debited from one bank and goes to next bank. If a transaction fails, the bank still keeps your money and returns it to your account."
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a3d5w7 | How does a night light or car with automatic lights know when to turn on? How can it truly detect if there is light? | Technology | explainlikeimfive | {
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"text": [
"Cars use photo sensors, sometimes on the dash under a frosted cover and sometimes in the back of the mirror. They aren't usually on the outside, that would expose them to environmental effects."
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a3d6xu | Why does chrome need so much RAM? | Technology | explainlikeimfive | {
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"text": [
"Web pages are complex. Browers can handle that complexity either with CPU or with RAM. The more CPU you use, the less RAM you need, and vice versa. This means that high usage of RAM is a good thing. You want as much of your RAM to be used all the time. Unused RAM doesn't do anything, except force you to use more CPU. One reason Chrome is fast is because it aggressively uses RAM to reduce CPU load. The downside comes when Chrome continues to use the RAM even when it doesn't need it, and when other applications need it. That's a bug called a memory leak, and bugs like that are inevitable with complex software, particularly when that software is modified with extensions."
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a3dxp4 | How does "Zalgo" text work? | By "Zalgo text", I'm referring to text generators like URL_0 , which formats any text you enter in it with an overload of extra symbols to make it look like a demon has possessed your Internet browser, kind of like this: Ê̱̤̹͖̖̈́̒͑̎̕͜ͅx̘̖̲̅̔͐ͤ́ṯ͈̣̻̼͚̈͊̈̊̐̈́ͮͮ̿͝ͅr̶̲͎̘̞͂͌͌͐̆ͫ̄̚a͇̔̀ͮ͠ ͇̥̪͍̼ͨ̓̔̿͌̉ͨ̚͘s̴̨̮̩̥ͦ͊ͫ̋̆͂ͥ͟p͉̠̺͕͈̥̱̾̈́̅̐̓ͨ͜͠oͦ͏̸̨̺̰͓o̶ͣͮ͗̽͟҉͉̗̙̭̙͙͙k̷͎͉͕̪͕ͮͫͨ̊̆͛y̥̝̏͗ͤ̊ͣ̈̀̕͝ How does this type of text formatter work, and how does it trick your computer/phone/etc to render all of these symbols on top of what's already being displayed? | Technology | explainlikeimfive | {
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"Yo ho ho! Yer not alone in askin', and kind strangers have explained: 1. [ELI5: How exactly does Zalgo text work? ]( URL_4 ) ^(_1 comment_) 1. [How do you create crazy looking text like this (p̷ͦ́̓͘a̐̿̆̂͋́͛̀̃̀͘͠҉͞s̃͊̂̈́͋̍̕҉t̷̛̋͆ͪ̇̄ͥ̓̈a̐̿̆̂͋́͛̀̃̀͘͠) and what is it called? ]( URL_5 ) ^(_._) 1. [ELI5: What the heck is Zalgo text? What is its purpose? ]( URL_2 ) ^(_._) 1. [ELI5:How does the weird \"horror text\" work? ]( URL_1 ) ^(_5 comments_) 1. [How does this comment work? ]( URL_3 ) ^(_._) 1. [ELI5: why are these font exist? what are the function? ]( URL_6 ) ^(_3 comments_) 1. [Eli5: What causes this weird text effect? ]( URL_0 ) ^(_4 comments_)",
"> how does it trick your computer/phone/etc to render all of these symbols It doesn't \"trick\" it, the computer is doing exactly what it was designed to do. Writing in English we do not often encounter symbols placed above or below characters, but other languages often employ such symbols. Things like the acute, grave, circumflex, tilde, umlaut and dieresis, and cedilla are all somewhat common marks above or below characters. Computer font systems are broadly coded to allow a huge variety of marks to be displayed above or below any given character as desired, even multiple simultaneously. This feature allows almost any language to insert whatever squiggles form their written language as required, but it also means such text generators can go overboard and inject a dizzying array of extra, pointless symbols over and under text simply for the bizarre appearance it yields."
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"https://np.reddit.com/r/explainlikeimfive/comments/207blp/eli5_how_exactly_does_zalgo_text_work/",
"https://www.reddit.com/r/NoStupidQuestions/comments/5hqamz/how_do_you_create_crazy_looking_text_like_this/",
"https://np.reddit.com/r/explainlikeimfive/comments/3la96b/eli5_why_are_these_font_exist_what_are_the/"
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a3eyks | Why does google earth not display the north pole? | Technology | explainlikeimfive | {
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"Because it technically is just ocean. It's always frozen, but it's ocean. Unlike Antarctica, which is an actual landmass, the North Pole is a floating ice sheet. So instead of live tracking which parts are ice and which aren't *cough cough global warming* , they just display whatever's not strictly land as ocean.",
"Because they only show land. There is no land at the North Pole. It is just ice and that ice is constantly shifting. So they show the ocean floor instead."
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a3fm59 | What is the difference between Bandwidth vs Latency? | I've heard them in terms of some analogies but am still kind of confused. If the analogy is cars on a high-way, is bandwidth more like having more lanes? Or is bandwidth more like cars are getting on the on-ramp at a higher frequency? Does that mean that Latency is the travel time? | Technology | explainlikeimfive | {
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"Bandwidth is how many cars can be on the road, latency is how fast they are going. So you basically got it. & #x200B; Another way to put it would be how many things you can carry vs how long it takes you to deliver them.",
"1. bandwidth = the total amount of traffic something supports. ie your internet speeds, # of cars on a road, etc. 2. latency = the response time of getting something back when you request for something. ie you go to a website, you request for the home page, the time it takes to get it back is the latency. you can have high bandwidth and high latency. for example. you friend asks you to ship them a 5TB hdd and you mail it and they get get it in a few days. the 5TB Hdd can be considered the bandwidth, and the time from when they asked to when you get it can be considered the latency.",
"As an extreme example, shipping a box of hard drives by Fedex has great bandwidth - if you send 10TB of data in 24 hours, that's over 900Mbps. But the latency is awful - it takes 24 hours for a given piece of data to make the journey.",
"Bandwith is total cars per hour, it's a combination of the number of lanes and the cars per hour of each lane (if a car just joined a lane the next car has to keep some distance and wait 2 minutes to join, for example). Latency is how much a given car takes to arrive, the difference between the departure time and the arrival time. Latency depends on speed obviously, but it's also affected by bandwith because if there are already cars on the road a new car will have to wait until there's a free spot and enough distance to join a lane."
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a3g580 | How did people change/alter pictures in the 1930s-1950s? Apparently pictures like the Nazis marching through the Brandenburger Gate or Lenin's speech were edited, how did they do that, with what tools available at their time? | Technology | explainlikeimfive | {
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"You know how people will say that things like fashion models are \"airbrushed\", but of course they mean that their photographs were digitally altered? An airbrush is a real, physical painting tool used to spray paint, ink, or dye. They could be used to paint on photographs in order to change them, smoothing out wrinkles or even removing people from the frame. Different photographs could be physically cut up and the seams where they merge airbrushed over to disguise them.",
"Others have pointed to specific methods, but to add a tidbit: most of the names of the tools in Photoshop come from real tools and/or techniques used to develop/alter photographs before digital editing. Anything from dodging/burning, smudging, blurring, cutting/pasting (literally using a razor or x-acto blade to cut out the part you wanted from one negative and pasting/gluing it on top of another negative) and many others that I can't remember off the top of my head.",
"I am by no means an expert on the subject, but you can do a lot with partial exposures. Basically you can only allow certain bits of image on the negative to be transmitted by blocking out the light. Then you can take another image, block other portions, and \"complete\" the exposure."
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a3icp7 | Monitors - What is the difference between response time (ms), refresh rate (hz) and frames per second (fps) | Technology | explainlikeimfive | {
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"Response time is a measure of how quickly a pixel can change from one color to another on an LCD monitor, since LCDs work sort of like a little curtain opening and closing that allows a light to shine through. A longer response time means that the image can appear blurry or have a \"ghosting\" effect if quick changes are supposed to happen. So a response time of 5ms means that a certain change to a pixel requires 5ms or 1/200th of a second to complete. Refresh rate is how many times each second that the screen is given a new image to display. The image might be identical to the previous one or it might have differences, in which case the response time determines how quickly it switches from the old image to the new one. So 60hz means the display is given a new image 60 times each second. Images are not sent instantly, in fact most of that 1/60 of a second is spent sending the image pixel by pixel, line by line starting from the top left. FPS isn't directly related to the monitor, it's a measure of how many images (frames) are being generated by *software* each second. When something called v-sync is enabled it means that new images created by software won't be displayed until the current refresh is completed, meaning that FPS won't go any faster than the refresh rate. If v-sync is not enabled then the image can be changed mid-refresh. This can cause \"tearing\" since when the image is changed mid-refresh then the upper part of the screen will get the pixels from the first image while the lower part of the screen will get the pixels from the newer image."
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a3ih3o | Why is modern electronically generated voice usually a female voice? | Today, things such as voice assistant devices (i.e. Amazon Echo), answering machines, computer text to speech (in default), etc. usually have a female voice. However, most 20th century electronic devices with a voice synthesizer chip (i.e. DECtalk, Texas Instruments Speak & Spell, etc.) generate a male voice. Why is modern electronically generated voice usually a female voice, while 1980's and 1990's usually a male voice? | Technology | explainlikeimfive | {
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"There are a few reasons. 1) People tend to like a female voice more than a male voice, just in general, especially an alto like Siri or Alexa. Everybody loves their mother, etc. 2) Disembodied voices that provide assistance have historically been female, like telephone switchboard operators, secretaries, and receptionists. 3) Male disembodied voices are often famously evil or deceptive in Western media. Think the Wizard of Oz, or HAL 9000. I'd bet that \"don't sound like HAL\" was pretty high on the interface design spec list, honestly. :-)",
"This was explained to me in a documentary about fighter jets. The voice inside that says, \"pull up. Pull up\" when the plane is about to crash is female because people listen to their moms and a female voice is more likely to be obeyed. A Male voice promotes Male to Male combat and the pilot wouldn't do as he is told. That's why the GPS in a car is female too. It's all about psychooogy."
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a3kvuk | How in the world does a cd, mp3 player, or any other sort of digital music player take data and turn it into sound? | I think I understand how data is stored... But how does it go from data to sound?? | Technology | explainlikeimfive | {
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"Remember, it starts out as sound. When it's digitized, it is compressed using an algorithm. To turn it back into sound, the process is simply reversed. It is decoded using the same algorithm. It's also important to remember that all sound is simply vibration at varying frequencies, so encoding that into something mathematical isn't that hard. Ergo, decoding it isn't that hard, either."
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a3l6ra | Why are the front and back cameras on smartphones not the same to begin with? Why do they need to differ in quality? | Technology | explainlikeimfive | {
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"cost and size. if all other variables remain constant, a bigger lens allows for better photos, as well as a bigger image sensor (the light sensing chip behind the lens). since they’re intended for different things, they just use different cameras. smaller cameras are also better at taking pictures of things closer to themselves (like a selfie)",
"Size. And cost. One has to discreetly fit beside the screen, not look like a hideous lens obscuring your screen size, and only needs to take photos up close of your face. The other one needs to function as an actual camera and take detail, be able to zoom, etc.",
"Back cameras are much larger and are able to do many more things. There’s no need to have two of them on a phone. The front facing camera is mostly for selfies so there’s no need for a zoom or wide lens",
"Most people are never going to use the selfie camera for anything other than - you guessed it - selfies, or possibly video chat, which by their very nature never need to be all that high quality. Putting a top quality camera in the front camera position would just increase the cost for a benefit, from most people's perspective, of very little.",
"Every penny saved on a component, when you're shipping several million units, adds up quick!!! If the selfie camera just needs to be adequate enough to do a good enough job, it's hard to justify the few extra pennies on the component, especially since selfie cams are not that popular of a selling point."
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a3pc09 | How did we ping the first satellite? | Technology | explainlikeimfive | {
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"We didn't. The first artificial satellite, Sputnik I, had nothing aboard but a transmitter that simply beeped until its battery ran down. Tracking was purely by radar.",
"The first satellite could not receive a ping. For the first one that could: We sent a radio signal from Earth toward the direction of the satellite. The satellite received the signal with an antenna. The satellite then sent a signal back to Earth which we received with an antenna."
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a3qxhq | Self driving cars | I have never seen a self driving car in person yet. But all these pictures in news articles and everywhere else show that they have outside rear view mirrors (OSRVM). Do self driving cars need a rear view mirror? What's the purpose of OSRVM in self driving cars? | Technology | explainlikeimfive | {
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"They don't \"need\" them to operate the self driving feature, but they aren't there for the computer. They have them for a variety of reasons. The biggest one is that most self driving cars are regular cars (Uber uses Volvos, Google has used Priyus and Chrystler Pacifica in the Waymo project) that have been modified to be driven by a computer. The cars came with mirrors on them already. Additionally - if you put the cars on the street - most cities require a driver to be available to take the controls. Side view mirrors would be useful for the driver in these cases. Most importantly - every US states has minimum safety standards for cars, including having functional side view mirrors. So, even if you had a fully self-sufficient self-driving car, unless you update these laws, the side view mirrors will still be required before the car is allowed on the street. Additionally - T[esla wanted to get rid of side view mirrors]( URL_0 ) and to replace them with cameras (could reduce drag up 3 percent) but were told \"nope\" by the National Highway Traffic Safety Administration. So, don't expect them to be going anywhere anytime soon. I for one, hope that they don't update this, and we get this little tiny vestigial mirrors on self driving cars only that only old people understand why they are there.",
"Nobody is making 100% self-driving cars right now - they still have to be able to be driven by a human operator. Humans need mirrors to see around them because they can't be watching 12 cameras simultaneously.",
"Self driving cars are very much coming, but they’re a bit overhyped right now by tech blogs and Reddit full of 20-somethings. There are quite a few hard hurdles remaining to get there, which can threaten progress significantly. In before article showing Waymo testing in Arizona, with fine print that its only under very certain conditions."
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a3vhjb | how are timelapses of growing plants made | How are timelapses like these made? URL_0 | Technology | explainlikeimfive | {
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"a stationary camera is placed in position and is set to automatically take a photo every minute/5 minutes/hour/whatever and then those images are combined into a timelapse video"
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a3y7qg | why airplanes have a special headphone jack? | Technology | explainlikeimfive | {
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"Originally, so you had to hire theirs instead of using your own. Nowadays you can buy an adaptor. It works the other way round too, their headphones don't fit your stuff so they're less likely to be stolen.",
"Ripped this straight from quora: > Why do airplane headphones have two jacks? > It is cheaper to have two wires for two channels going into two jacks. Secondly, it is to discourage passengers from stealing the headphones because they cannot be plugged into any radio, cassette deck, tape recorder, etc. Bear in the mind the newer planes use the standard 3.5mm jack."
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a3z6w2 | Why are dots and dashes the only acceptable non-alphabetical/numerical characters in usernames on social media sites and message boards? | Like is there any specific reason as to why other characters cannot be accepted, like an asterisk or a currency symbol? | Technology | explainlikeimfive | {
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"In programming, certain characters are reserved as special characters. These characters vary by programming language, so it's easiest to just prohibit all of them. Why is this a problem? A lazy programmer might take the provided username and simply drop it right into their code. This means that a malicious user could create a username that intentionally makes the code do something it's not meant to do. This is called an \"injection attack\". And there are plenty of good non-malicious reasons too. For instance, the $ symbol looks like a capital S, so that presents issues with readability and username forgery.",
"We give people usernames because it provides us a recognizable identifier we can use *everywhere* to refer to one specific person *Everywhere* can potentially include the front of email addresses, URLs, filenames, links, etc as well as places we haven't even thought of yet. All those different places have different rules about what characters you can use, and what they do when you try to use the ones you can't. For example, if I wanted my reddit username to be `the?mighty?chris`, my reddit URL would have to show up like ` URL_0 ` because `?` has special meaning in URLs and the rule for using those characters without their special meaning is to replace them with those `%XX` stand-ins. If you're used to knowing me as `the?mighty?chris` you might not recognize me in that URL at a glance because those stand-ins can be distracting Many other answers have focused on how programmers forgetting to change special characters into their stand-ins can cause problems and saying it's safer to just forbid them. That's not really why they're always forbidden in usernames though, websites already deal with lots of other places where you can type any characters you want. The real reason is that even when you succeed in handling the special characters correctly in every place, you'd still be defeating the whole point of having a username by making it ugly and less recognizable So, the traditional constraints for usernames are really about adhering to a lowest-common-denominator of characters you can use *everywhere* present and future **without needing to make them unrecognizable**. This particular set of characters probably came to be the lowest-common-denominator because they're ones programmers would commonly use while naming files. Dots became common with the convention of file extensions (e.g. `.doc`) to indicate the type of a file, and hyphens/underscores became common alternatives to spaces because spaces look like breaks when you have columns of data on your screen. Programmers always want to be able to recognize their filenames easily so it's always been a priority to keep those characters usable without any stand-ins by choosing different characters when they need to find ones to give special meanings to",
"A lot of these characters don’t work in URLs, or at least not across all browsers, so only safe ones are accepted so you can have urls like URL_0 There are some security concerns also with some characters as they can be used for “injection-style” attacks on databases but most modern platforms are protected against that these days. I’d also suspect most platforms keep the allowed characters to the strict minimum to prevent you from coming up with something you’ll never remember yourself.",
"In addition to what everybody said, there's also a Unicode problem where a sequence of codepoints could look like another sequence. For example: * ; and ; are different codepoints. * Code point U+200F makes text go right-to-left but would be technically invisible in a username. * There are more so-called invisible codepoints which would be unnoticable. You could remove any of these fancy things, but then suddenly you're back at square one, and also people suddenly occupy multiple usernames, one with the invisible codepoint and one without (GMail works like this, where `FearfulGoose` and `Fearful......Goose` point to the same account). The easiest solution would be to just disallow such characters.",
"For a real ELI5, maybe even ELI3: have you ever seen those memes where people are playing a game, and there's a dialog option where an NPC says \"good job [username]!\" And then someone makes their username \"killing all those people\" and it makes the NPC say \"good job killing all those people!\" Well in the same way, using special characters would make the program DO bad stuff, like run mean virus programs, instead of harmlessly making an NPC say something naughty.",
"Some symbols may be hard to type on some layouts. For instance things like an € or a £ may not be anywhere on an user's keyboard. If you need to write an user's username, it's useful to be able to actually do it. For some symbols they may be unusal enough that the person that needs to type it wouldn't know what it's even called, and asking \"how do you type a weird bent squiggly thing\" isn't going to get very far. The same goes for accents. In the US and the UK, they're not seen much at all. They're also quite varied. Compare: áéíóú and àèìòù. Then there's the matter of encodings. While these days UTF-8 is thankfully in a lot of places there are still legacy systems that don't use it, and where something like an £ may not exist at all. And then, there's an additional bit of fun. Different languages have identical looking letters to English ones, but which to a computer, are different. Let's say I registered myself as \"dаlе_glаss\". Go and try to search for it with Ctrl+F by typing it in the search box (without copy/pasting) and see if you find it in my comment. Overall, allowing people use whatever random thing they please in usernames allows for a lot of corner cases and confusion. **Edit:** typo",
"Because it's the [POSIX Portable Filename Character Set]( URL_0 ) Even though it's usually not used for filenames, the same underlying reasoning applies.",
"I think the short answer to your question is \"No, there isn't any specific reason why other characters cannot be accepted\". So why do sites limit usernames this way? They don't all do so, of course -- some limit them in other ways (underscore can be used sometimes), some allow only alphanumeric. Having them limit the characters they accept makes it a little easier to use the usernames in some programming situations. For instance, some programming libraries use asterisk (\"\\*\") as a 'wild card' character, matching 0 or more characters; someone doing a search for \"al\\*\" will match albert, alvin, and al; if the program allowed asterisks in the username, then programming code to search for a name would have to search the name for asterisks and mark any asterisk specially so that it meant a real asterisk, not an asterisk that meant a wildcard (\"al\\\\**\"). Commas, as another example, are often used to separate fields of data; there are situations where the string \"al, becky, charlie\" means 3 first names. If the program allowed commas within the names, then in any situation where they might be used in a list, programming code would have to search each name for a comma and mark it, and programming code getting the name would have to look for the special mark and remove it. So it's easier to just say \"They don't need those characters, we'll ensure that they don't get into any usernames.\"",
"Some characters are not accepted because they have a syntax meaning. That is, they control how a block of text is interpreted. There aren't any characters that are universally special. Some might be special because of how the username is used. For example, in Twitter, usernames can appear in tweets like so: \"I saw @joe just yesterday!\". The @ special character marks the start of the username and a space marks the end of the username. So those two characters should be reserved. If they allowed spaces, for example, how can you tell they're not referring to the user \"joe just\"? For the same reason, they bar other punctuation characters, so that an @username can fit into normal English writing. Some characters are special for more \"internal\" reasons. For example, a Twitter's user page is \" URL_0 \". In URL syntax, the forward-slash is character with special syntax. It'll cause trouble, then, if the username contains one. One ugly kind of internal-use special-character ban is to prevent code injection. (See other comments on code injection.) It exists because programmers are bad. Such is life. Most of the other \"standard\" special character restrictions go back to Unix filename conventions. Tons of places that special characters show up (like URLs) are ultimately patterned after how you name files in Unix. While few if any characters are actually disallowed, most special characters are avoided because they have special meaning to the command-line shell. People stick to alphanumeric and dot, dash, and underscore. Other characters are disallowed because they'll cause trouble or confusion for users -- like crazy Unicode tricks. At that point, it's easier to make a limited list of allowed characters rather than try to figure out how to make a list of everything that should be disallowed. TLDR: Usernames are a-zA-Z0-9.-\\_ because that's how you name things in Unix. Go figure."
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a3zkbv | How is google search so ridiculously fast? | Technology | explainlikeimfive | {
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"Because Google doesn't search the internet every time. It has bots (so called web crawlers) that surf through the internet constantly and make some kind of phone book, memorizing everything they see. So if you type something intk Google, to stay in the phone metaphor, it doesn't need to dial every number to find the right number but only look in its phone book.",
"Search engines are made possible by storing an index in a data structure called a hash table. The basic idea is that you make a whole bunch of buckets, and then you have a way to figure out exactly which bucket to go to. Unlike the index in a book, you don't have to fumble through it to find the right entry. Instead, you use a special formula (called a hash function) that tells you exactly which bucket to go to. The hash table is an almost magical idea that makes many otherwise daunting problems in Computer Science fast and easy."
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a40x7g | Why are radio stations identified by their exact frequency, such as 103.1Mhz, whereas TV stations were traditionally identified by a generalized channel number, such as 7? | Technology | explainlikeimfive | {
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"Radio signals are a single frequency. TV signals contain(ed) multiple frequencies (for the video, RGB colors, and separately for the audio), so they made a dial with \"channels\" instead of having multiple frequency dials and forcing people to \"tune\" the image and then \"tune\" the audio separately. That way you tune into the \"channel\" and the TV tunes into the sets of frequencies required to receive the video AND audio for that station.",
"Just realized this is ELI5, so I'll add some more. Radio and TV use the \"electromagnetic spectrum\" to reach you. That is a fancy word for stuff like light, and a small part of that is the rainbow. Think of each color in the rainbow as a frequency like on a radio. You can just listen to red or blue or yellow for the radio, but TV has to send out pictures and sound so it can't fit on just one color. Instead of watching a show on Red-Orange-Yellow, we call that Channel 1. Green-Blue-Purple is Channel 2. ----- More detail that is not ELI5: A TV channel uses up a wider section of the spectrum in order to handle all of the video and audio content. URL_0 It's like WiFi uses channels as a shorthand for the chunks of spectrum you are using.",
"Both television and FM frequencies are allocated by channel. FM channels are small enough to be centered on a readily human decennale frequency. In imitation of earlier forms of radio, they use the center frequency as an identifier. Before 1989 they were typically more vague with an approximation of the center frequency. \"Rock 96\" became \"Rock 95.7\" during the eighties in no small part due to the introduction of digital frequency counters or dials on consumer-grade receivers. Television utilizes channels which are, in North America, 6 Mhz wide or obnoxious to common ears to discern through announcement. From 1947 forward, in lieu of 63 MHz or 60-66 MHz a more convenient identifier was simply \"Channel 3\" which also made the dials on TV receivers easier to discern.",
"Radio stations are much more spread out, over the spectrum. You might have 2 dozen radio stations in the same geographic area. You may also have someone on 100.3 and someone on 100.9 With television, particularly with VHF in the analog days, you only had a couple, so a fixed dial made more sense. My guess is UHF which had more channels just copied what was then the format everyone knew for VHF.",
"It is part of the laws that are enforced by the FCC found here: & #x200B; [47 CFR 73.1201 - Station identification.]( URL_0 ) & #x200B; As an interesting side note some television stations used to broadcast over the air (remember back in the days of antennas) VERY closely to the band of frequencies that radio worked at. In the Milwaukee, WI area you used to be able to pick up the audio for channel 4 if you turned your radio all the way down to the LOWEST end of the FM dial. There was some slight leaking for channel 4 that would be picked up on a radio but only for audio.",
"TV actually used to be tuned manually with a dial, same as radio, these days they're tuned automatically. Each TV (and Radio) station is assigned a bracket (or channel) with a small range of radio frequency to accommodate any signal disruption. In television it's usually several megahertz wide. Each of those brackets is numerically identified by its position along the radio spectrum and the stations themselves usually name themselves to match. Mostly it's a national/international convention. Side note: Modern TV broadcasting includes a lot of stuff like multiplexing which means that not all of the signal you're watching is in the same channel, but they continue using the original brackets for legacy reasons. you can still take an old TV from the 40s and watch modern shows on it without most of the extra features. In the US, radio stations are required by the FAA to identify themselves for legal reasons at the top of every hour, minimum requirement is the callsign and city of licence, but typically they include the frequency and the station ownership as well. TV do something similar, but only have to do a callsign as a graphic on-screen each hour or so. Speculatively, by providing their exact frequency (as the middle and strongest part of their signal bracket) a radio station is assisting manual tuning because now you know whether you need to dial up or down the spectrum to get a better signal. TVs don't bother because you're not generally travelling, so stepping up and down the frequencies at fixed intervals will get consistent results once you've tuned initially.",
"They weren't until digital tuners became common in the 1980's. Everyone just rounded up or down because on the old tuners with a dial, the decimals weren't there. You just kind of scrolled around until you got the best signal."
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a41j62 | how does polymorphic code work? | Technology | explainlikeimfive | {
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"Imagine a living Rubik's Cube whose function is to keep you from solving it. Whenever you try to solve it, it changes itself to make it more difficult. When you make one move, it makes another move, just to prevent you from solving it. This is basically what polymorphic code is: a program that changes itself while maintaining it's function. In this case, if the Rubik's Cube were a program, its function would be to keep you from solving it. It will constantly change just to keep you from solving it until you solve it."
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a41luk | How does the weather get reported by each town to the weather app on my phone? | Technology | explainlikeimfive | {
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"There are organizations (large groups of people) who have satellites (giant cameras and sensors in outer space) which send the information they find to weather apps. The satellites along with local meteorologists (weather analysts) provide information to weather apps, which show you the information they have and their predictions."
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a420ap | How do buttons on electronic devices have more than one function based on how long you press them for? | Like when you want to completely turn off a smartphone you hold down the power button for five seconds, but pressing the same button for just one second simply locks the screen. The same for an iMac where the length of time you hold the power button changes what happens, and there’s (apparently) multiple outcomes depending on how long you hold the button for. Button, how you do so many different things?! | Technology | explainlikeimfive | {
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"When you depress the button, it allows electricity to flow through a gap, like turning on a faucet. Another circuit measures how long that electricity flows for. When you lift your finger, the flow of electricity turns off, and an action is performed depending on how long the electicity was flowing.. Sometimes there is also a time limit; once 5 seconds is reached, your iMac turns off regardless of whether you lifted your finger or not.",
"So imagine there is a little person inside the phone. They've got a stopwatch, and a chart, and a little panel of buttons. And there's a light that comes on whenever you push the button. The moment they see the light come on, they start their stopwatch. Every time the watch ticks, they look at the chart. The one for the phone's power button says something like \"if the button is released, lock the screen; if the button is held for five seconds, shut down the phone\". And they do that - if you hold it down long enough for the stopwatch to count up to five seconds, they hit the button on their panel that says \"shut down\", which turns on some *other* lights in other rooms that tell everyone to save what they're doing and get ready to go to sleep, then eventually tells the person hanging out in the power room to pull the big switch that shuts everything off. But if you let go before that, then they stop their watch, check the time, and hit the other button on their panel that says \"lock screen\". Which, again, turns on some other lights in other rooms, telling the people there to do whatever they may need to do to get ready for the screen lock, then to lock the screen, and ultimately tells the person in the power room to pull the lever that shuts down *some* parts of the phone. Of course there are not actually little people in your phone or computer, but there are different bits of software running on multiple computers inside your computer that do these things. Macs have a separate computer called the [System Management Controller]( URL_0 ) that is *always* on as long as the computer has power; it does a bunch of low-level things but one of its most important jobs is to sit there watching the power button and wake up the rest of the computer when you push it! And it is a complicated enough entity that it can get confused and need to be reset.",
"Using the smartphone as an example. The software on the phone determines the action not the mechanics of the button. When the button is pushed it just says \"hey the \"power\" button is being pressed. It keeps getting that signal until you let go. Then when programming the phone essentially you say \"IF the power button is pressed for more than 2 seconds THEN power down\" while having another condition that says \"IF power button is pressed for less than 2 seconds THEN turn the screen on or off\" I tried to keep this ELI5, it's much more complicated and there are many different pieces of software that are needed to perform this function but that's the basic idea.",
"so it used to be that buttons would be hard-wired to a power source and physically either connect or break the circuit between the power source and the rest of the device. Nowadays, they are more complicated devices with pressure sensitive states that will tell a circuit or piece of software (depending on the design) how long the button is held down for before being released, and that will in turn run through logic that dictates what to do with that kind of key-press. Behind the scenes there is some bit of hardware or software that is programmed to do something like \"wait for power button to be pressed, then start timer and wait for power button to be released or for 30 seconds to pass. If released and timer is under 5 seconds, toggle screen on/off. If released and timer is between 5 and 30 seconds, show menu. Else hard shutdown phone.\" which will either turn off your screen if you tap it quickly, present the on-screen \"restart phone, turn off phone\" menu if you hold it down for longer than 5 seconds, or hard shutdown the phone if you just keep holding it"
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a43gqp | How does Teslas giant battery work? | Technology | explainlikeimfive | {
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"It's just a bunch of smaller cells. You know how a remote control seems to always take two AAs? It's like that but on a larger scale and with much more than 3 volts involved. There's 3 ways to set up cells: series, parallel, and series-parallel. Series is where they're end-to-end, like the way that remote control is wired up. Each AA in there gives 1.5 volts, put two of them end to end and you get the voltage of both! So now you have 3 volts, and for simplicity let's say you can draw 1 amp this way. Parallel is if they were truly wired \"side by side\" instead of end to end. If we wired those AAs in parallel, you wouldn't get double the voltage like in series, but you would get double the potential current, so twice as many amps. Only 1.5 volts, but now we have 2 amps. In series-parallel, you combine the two. So let's put our first two AAs in series to get 3 volts out of them, but they can only put out 1 amp. Now let's get two more AAs and put those end-to-end also. Then wire the top and bottom of our two stacks side by side. So now we can get 3 volts, but can now draw 2 amps since we have two stacks. A Tesla battery likely does series-parallel, just with cells *much* more powerful than AAs."
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a43j0x | In photography, with regards to exposure bracketing, what does the term 'stops' mean? And how does it all work, does the camera actually take 3 pictures and just merge them or? | Technology | explainlikeimfive | {
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"Stops is an old photography term, from the age of film. Most of photography has difficult units, and this is a way of avoiding that. Exposure bracketing involves taking three pictures: neutral, +1 stop over exposed, and -1 stop underexposed. The three pictures are kept separate, and the best one used to make the final output. When this was done with film cameras sometimes the three images, or two of the three images, were recombined during printing to make a composite exposure. For landscapes, this has some technical advantages over dodging/burning (optical equivalents of Photoshoping).",
"Fundamentally, there are three things that control how exposed a picture is in a camera: how long the shutter is open, how wide the opening between the outside world and the sensor (the \"aperture\") is, and how sensitive the sensor is. Each of these things lends themselves to a different kind of measurement, though - shutter speed is a length of time, aperture is a function of distance (diameter of the opening), and sensor sensitivity is a function of engineering constraints that are more than I can cover in an ELI5 - but it's expressed as an ISO number representing the \"speed\" of the sensor (bear in mind this is inherited from film, and is basically \"how fast will this film go from completely unexposed to completely exposed under a standard light\"). But each of these factors has an impact not just on how exposed the sensor is, but on other aspects of the image. For example, slower shutter speeds (meaning the shutter stays open for longer) mean motion gets blurred; wider apertures mean a shallower depth of field; higher ISO means more noise in the picture. While you always want to have the right exposure, several combinations of those variables can achieve that. If the shutter is open for longer, for example, you can compensate by closing the aperture or slowing the sensor. As a result, it is useful to know how each maps to the other: that is, if you want to close the aperture, how much longer do you have to keep the shutter open to exactly compensate for it? In other words, what length of time maps to a given change in diameter? The answer is the \"stop\" - each of the three variables can change by a number of \"stops,\" with each 1-stop increment representing a doubling or halving of the amount of light let in. So if you close the aperture one stop from f/5.6 to f/8 (why f/numbers are what they are is a somewhat separate topic I can go into if you'd like, but isn't pertinent here), and you slow the shutter from 1/200 to 1/100 (those are fractions of a second), you'll get the same amount of light. This leads to changes to exposure being expressed in stops - because from a strict \"is it properly exposed\" standpoint, it doesn't matter how you got there. Which, in turn, is why exposure bracketing is expressed in stops. When you're doing exposure bracketing, the camera is taking three pictures in a row at three different shutter speeds to get three different exposures. You might, for example, set the camera up to bracket at a full stop - then when you hit the shutter button, the camera will take three pictures in quick succession. One at +0 stops, one at -1 stop, and one at +1 stop. Typically you do exposure bracketing for one of a couple reasons - first, to give yourself some wiggle room, particularly in changing lighting conditions. Three shots at different exposures gives you a better chance at one of them being the right exposure. If this is the goal, you're likely to use fairly narrow brackets (so 0, -1/3, +1/3, for example), since you're likely to only miss your exposure by a little bit. The second reason is to do HDR - high dynamic range - processing on it. This is when the camera (or, better, post-processing software) does some algorithmic wizardry on three different exposures of the same scene to mash them together such that you can see detail in both the bright and dark areas of a picture. You do this because like your eye, a camera sensor has a limited brightness range it can see at once. You've probably had the experience of someone shining a flashlight in your eyes, which makes it very difficult to see any detail in the darker areas around the flashlight - this is because there's only so much \"dynamic range\" your eye can see at once. The \"dynamic range\" is the total difference between the brightest thing you can see and the darkest thing you can see. A camera sensor has the same problem (only much worse; by some measurements, human eyesight can take in more than 20 stops of dynamic range; a DSLR will typically be able to see ~12 stops), so you have to pick which range of brightnesses it records. HDR works around that by sort of \"flattening\" the brightest bits and darkest bits towards the middle bits of three exposures. Hopefully that's answered your question (albeit in a somewhat rambling and lengthy way; sorry about that). Let me know if I can clarify anything for you."
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a43v6p | How does 2 channel, 4 pole, audio from a 3.5mm jack deliver 7.1 surround sound? | I want to buy a new headset, currently have a USB headset that is 7.1 and I can understand that there is some digital magic at work creating surround sound. I do not, however, understand how a 2 channel stereo, 4 pole, 3.5 mm jack can deliver surround sound... how does it not require 7 channels? Looking at HyperX Cloud Revolver S. | Technology | explainlikeimfive | {
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"The additional channels are decoded by the receiver. Dolby Pro Logic does this (very old school surround). So the signal is encoded by the manufacturer of the audio and when you turn on the Dolby Pro Logic it sends a different set of tracks that include the whole data, this gets decompressed and played back. This process is referred to as Matrix-encoding because it uses linear algebra equations to encode / decode the data. This did not need high end digital circuitry, and could be done using resistors capacitors and amplifiers. For ELI5: pretty much just play the left front and rear on the same line but separate them using electronic trickery. Then decode those back out into two channels at the receiver. EDIT: It's a pretty simple circuit. URL_0"
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a44oco | How do devices like JUUL detect inhale? | I have taken mine apart, both pod and device and I am completely stumped as to how devices such as the JUUL detect when you inhale. Any ideas? | Technology | explainlikeimfive | {
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"Not sure on how JUUL are set up, but there's two types. If you have to hold a button it doesn't have to detect any inhalation, the button activates the coil. If it is a manual device without a button, there is a pressure switch that is delicate enough to be drawn closed when you inhale. I could easily see something like a reed switch controlling this; they require magnetic fields to operate, and you could simply make the air intake be behind a magnet that then gets pulled up next to the switch when breathing."
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a46tv5 | How do Draw Bridges kmow when a boat is coming to pass by? How are the traffic lights programmed for this? | Technology | explainlikeimfive | {
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"Usually there's someone controlling the drawbridge, and when they open the bridge the lights turn red",
"Usually, a boat will radio the intent to pass through the channel spaned by the bridge. The drawbridge operator may open the bridge upon a single request, or delay to queue other boats also in close proximity."
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a46u8m | how a vinyl record is able to produce music and sounds since it’s a just a piece of plastic | Technology | explainlikeimfive | {
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"There are very small grooves etched into the surface of the disc and these grooves have tiny hills and valleys in them as well as being squiggly back and forth. As the needle of a record player follows these grooves the vibrations caused by it going up and down and back and forth are amplified and played as sound. Fifteen minutes of a more in depth explanation if you feel so inclined: URL_0"
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a46z0h | Does memory that’s been ‘leaked’ ever get freed? | Technology | explainlikeimfive | {
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"Yes. Applications don't get direct memory access. They're given virtual memory, and the OS will reclaim all of the virtual memory once the program ends.",
"Sure, just turn off the power. When the machine starts back up, all those allocations will be forgotten. This is one of the reasons that turning the power off and then on again \"fixes\" computers.",
"Short Answer: Yes. Close the program and restart it or reboot the device. Long Answer: I want to clarify for any novices that memory does not mean disk space, or storage. This discussion is not about how to recover disk space. What does it mean when we say memory is \"leaked\"? When any given program is running, it needs memory to do its job. It requests this memory from the OS (operating system). The OS is usually Windows, macOS, Linux, Android, iOS, etc. If the application loses track of the memory given to it then that memory is considered to be \"leaked\". Think of it like losing a phone number. The phone is still there but you can't call it any more because you lost the number. The reason the program loses track of the memory is because it no longer needs it. It's like losing a CraigsList seller's number. Who cares? You don't need it any more. Ultimately this is always due to a programmer making a mistake. Depending on the language and development environment, it can be VERY difficult to prevent or even detect that a program is leaking memory. In many situations, small memory leaks aren't worth bothering with detecting and fixing because the program is restarted often enough that the leak doesn't really matter. The consequences vary, but ultimately they lead to the same endgame. Eventually the OS will run out of memory.You might be told to close some programs. The program might \"crash\" if it assumes the memory is there when it isn't. Another program might crash because it can't get any memory either. If the program is leaking a few bytes at a time, it will take a long long time for this to happen. If it's leaking memory millions of bytes at a time, the OS will run out of memory much sooner. The last thing is this. When you close a program **and it finishes executing**^1, ALL of the memory it was using is released. So if you are using a program that leaks memory, you can just restart the program to free up the memory it's using and the OS will reclaim it. If you run the program long enough that the OS runs out of memory all kinds of things can happen. In these cases it's best (and usually necessary) to reboot the entire machine. This will reset everything and all memory will be freed. This can also happen if you're running too many programs that are asking for too much memory for the OS to handle. ^1 On Android, and probably some other OS, even when you close a program it is still running in the background. There are also some programs that are designed to leave a background process running. You can usually use some sort of Task Manager to kill these programs, but some things might require a reboot (I'm thinking of things like Windows device drivers). Note: I'm glossing over things like how much physical memory is available, virtual memory, and so on."
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a476ue | Why would a solar storm's sustained magnetic field NOT destroy all data-even tape drives? If a degausser wipes data with powerful sustained magnetic fields, why would a weeklong solar storm not have the same effect on our data? | Could a solar storm big enough and sustained long enough destroy all data storage devices that aren't inside a Faraday cage? Why or why not? | Technology | explainlikeimfive | {
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"A really strong solar storm causes changes of > 250 nanoTesla in the magnetic field. The absolutely worst geomagnetic storm is estimated to have peaked at 1760 nanoTeslas. For reference, the Earth's magnetic field is around 50 microTesla or around 25x stronger than the strongest storm Those degaussers use electromagnets that can put out magnetic field strengths in the 1-10 Tesla range, or 20,000-200,000x stronger than the Earth's magnetic field"
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a47tq0 | Why do PC drives always default to C: as the boot drive? | Technology | explainlikeimfive | {
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"text": [
"A an B were reserved for floppy drives. One for boot, one for programs. C was for a hard disk.",
"This is a Windows OS convention that originates back from the days when the first two drives, A and B, were for large \"floppy\" drives. Hard disks which contained bootable operating systems were a later development and so were assigned the third drive letter.",
"Originally PCs had a maximum of 2 floppy disk drives labelled A and B. As technology advanced some time later hard disks got added and became drive C."
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a4bctx | How Do the Different Cell Networks Talk to Eachother ? e.g. I Send a Group SMS to 12 Contacts. Some Contacts Receive it Immediately. Others Don't Receive it for up to 3.5 Hours. | Technology | explainlikeimfive | {
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"before we start on the text message, we need to talk about the cell phone and tower relationship. whenever a phone has its cell radio turned on (not in airplane mode), it's going to broadcast a message \"i am krystar78's phone, is any cell tower hearing me?\" if there's a cell tower that hears that, they'll reply \"yo, i'm cell tower #98465 for AT & T. i see krystar78's SIM card is registered to an AT & T account, i'll register your phone as active on me and let the phone network know to contact you via my station\" when twitstein's cell phone sends the msg to the associated cell tower in NYC, whether that be your phone carrier's or the roaming carrier's. the cell tower sends it to the carrier's central computers that owns that cell tower. central computer then sees if the recipient (krystar78) phone has registered itself on any of this carrier's cell towers. oh.. looks like krystar78 is registered on cell tower #98465. we'll just send that txt msg to cell tower #98465 and have it send the msg to krystar78's phone. or oh...looks like krystar78 isn't on any of our carrier's accounts. that number belongs to Tmobile. we'll send this to Tmobile's SMS gateway and let them figured out which cell tower krystar78's phone is on."
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a4dj56 | How did admirals know the location of their ships and control them over vast distances before the invention of radios? | Was reading about the battle of trafalgar and was curious how fleets were managed and how they communicated | Technology | explainlikeimfive | {
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"In short: they didn't. The longer answer is that they sent out faster ships to certain ports, with messages. Hoping to meet up when the ships in question resuplied. Most ports also kept records of ships sighted. In the shorter distance of fleets signal flags and flares were used. Semafore, (waving around paddles) was developed relatively late.",
"Admirals often traveled with their fleets. Every fleet on extended operation would have a Flagship, this was the ship the Admiral was on and it flew his Flag to denote that it was in charge. At the battle of Trafalgar there were four Admirals present, two for the British(Nelson and Collingswood), Villeneuve for the French, and Gravina for the Spanish fleet. Admirals would issue orders to the ships in the fleet by having flags raised to send messages to any ship that could see them. They could issue orders to specific ships, or the whole fleet, or send general messages depending on what flags were raised in what order."
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a4do96 | It seems like we’ve had telephones for decades, but the sound quality of phone calls has remained the same. Why is this? | Technology | explainlikeimfive | {
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"> but the sound quality of phone calls has remained the same. No it hasn't. I grew up in small-town Canada in the 1970s. I won't say I recall the exact sound of the background static/noise. I will say phone calls today(local/international) are much less noisy compared to then.",
"Some of these technical answers were technically right but the correct answer is... The phone company has determined the lowest possible call quality you're willing to accept and provides its customers with nothing but the lowest quality possible. & #x200B;",
"Phone call quality depends heavily on frequency bandwidth. Human hearing goes up to about 16-20kHz, but phone calls are typically allotted only 3kHz. This cuts off any frequency higher than about 3.5kHz and lower than 500 Hz and makes the audio quality terrible. Frequency bandwidth is increasingly very limited in cellular networks and there's no economical way to give calls 20k of bandwidth without seriously limiting the number of calls that can fit on the network. If you've ever used google hangouts or something similar to place a call you'll notice the audio quality is usually much better because they can afford a wider bandwidth over wifi.",
"All the other people have great explanation but the simplest one is ‘if it isn’t broke don’t fix it’",
"I think the sound quality of phone calls today is much worse than during the '90s. It seemed to take a drastic drop in quality when we changed from analog lines to digital compression. Anyone remember 20+ years ago Sprint advertising you could hear a pin drop? No carrier would ever try to make that claim today.",
"Phone call quality has actually gone down, it's because instead of analogue lines like POTS that everything ran on, everything is digital SIP nowadays. POTS provided better quality than the way we implement SIP nowadays. ( there is a lot more to it though, but this is an extremely general answer. )",
"Because the infrastructure (mainly the way the phones are connected) has stayed pretty much the same.",
"The short answer is bandwidth. Regardless of the technology used, quality is mostly governed by how much bandwidth we are prepared to allocate to each call. While more bandwidth improves the quality of an individual call, it also reduces the number of simultaneous calls you can pack into a given main phone line (the ones that connect various central offices / exchanges together). Most phone systems have determined that limiting the audio to a 4kHz band (about 1/6 of the bandwidth of \"CD Audio\") gives enough sound quality for the average person to understand speech while still letting lots of calls get packed together onto each main line. Since main lines are expensive, the fewer of these you can get away with, the better."
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a4eo0i | How did we count the years before we knew that the earth went around the sun? | Technology | explainlikeimfive | {
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"We still had seasons. So someone might say their child was born during fall harvest and has been through 5 winters. Or use landmark points in time and say they got their scars during the wildfire of the dry summer thunderstorm. I don't know how useful it would have been to most people to know exactly how many years there were between points in time, but if it needed to be measured, humans are clever pattern seekers.",
"A mix between seasons and the length of days. It's a year between Winter's and a year between the longest day of the year and shortest day of the year. Then people came up with Calendars based off knowing that."
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a4f27q | Why are cartoon movies colored differently than their TV counterparts? | When comparing episodes of a cartoon TV show (ex. Spongebob or Hey Arnold) to their respective movies, the coloring (and sometimes even the art style) doesn't look quite the same. What is different about creating the artwork for movies? | Technology | explainlikeimfive | {
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"1. The medium: they are going to be viewed on is different. A movie screen is substantially different than a tv screen and a different aspect ratio. This requires higher quality picture 2. time: they have more time and funding to complete their task. Cartoons made weekly or biweekly have a tight schedule, a lot of corners are cut to expedite production to meet deadlines. 3. Funding: the source of income for a movie is ticket sales, the source of funding for a show is however much a studio appropriates depending on how much they can get for commercial time. Films in theaters tend to make money best when quality is high and quality cost money. Shows require new content, people want to ‘tune in’ to the newest episode that’s good for selling commercials. So cranking out new episodes is more important than quality.",
"I was an animator for a studio that made tv series. The colors are decided by a process known as color scripting. In a movie, a lot of attention is paid to the color script and it can take weeks and maybe months to finalize all the colors for a movie. No corners are cut, no limits for fancy lighting setups, and we take all the time we need to make it perfect and amazing. In a tv show, because there are so many episodes and so little time, the color scripting is done extremely quickly, and we have to find economical ways to get these colors without adding too much to the workload of the animators, background artists and compositors (the person who puts all the elements together in the end and does post production). If you try to do something fancy, the workload gets compounded throughout the pipeline so you really can't deviate too far from the base colors unless you can find a way to do it quickly, which really limits the techniques you can use. This of course depends a lot on the style of the show. The last series i animated in had gorgeous colors and lighting because the style was kept simple enough that more attention could be made to the colors. But I also animated in a series where there was no color change at all, everyone was always in their base colors, and it was fine because it was more about the animation and writing. It's the choice of the director how much work he wants to put into the colors and whether or not it added enough to the show to justify the man hours it would add. Spongebob and Hey Arnold's style and writing was enough to carry the show without the need to go all fancy for the colors, so they didn't. tl;dr It takes a lot of time and a lot of skill to make great colors, and while movie productions can afford it, tv series have much more limiting time and budget constraints",
"they have more money, for one thing. also I think it would be good to distinguish from the shoe so it's more dazzling, cause it is a movie. why make a movie, another form of entertainment, the same thing? you wanna drive to the theater to watch the exact same thing you can get on tv?",
"The Digimon movie did this! The cartoon looked fine but the movie looked amazing and so clean looking!",
"I noticed that the TV series version of Disney's *Tangled* got around this somewhat by shifting from 3D-style in the movie to a more traditional-looking 2D in the series. 3D looks awful under a smaller budget."
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a4g0cx | Why does picture quality on Netflix appear to be of much higher quality than Cable TV even when both sources are outputting 1080p? | Both Netflix and Cable output 1080p, but the quality on Netflix is much clearer than that of cable which looks a bit more grainy. I've even rewatched shows that used to air on cable and it's not even close. Will cable TV quality ever actually catch up? | Technology | explainlikeimfive | {
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"It depends entirely on how much *compression* the sender is using to save on data capacity. Your cable TV provider is probably compressing the picture transmission so they can carry more channels on the same wires.",
"Everyone has given various answers relating to \"compression\", which is accurate, but is only one part of the story. An equally important part is the use of *one-pass* versus *two-pass* encoding. When compressing a video using two-pass encoding, the compression software will first conduct an *analysis* pass, scanning the video and checking for various ways to compress it more efficiently than normal. Then, it will go back and do the actual *compression* pass. This results in *much* better video quality at the same compression level than you can get with one-pass encoding. Cable TV is encoded \"live\", so there is no possible way for them to do an analysis pass. They have to encode on-the-fly. By contrast, Netflix can encode their content in advance, so they use two-pass encoding for everything. You can see this phenomenon for yourself with on-demand content: record a show broadcast live with your DVR. Wait two weeks, then look for the same show via on-demand on your cable service. The recording, using one-pass encoding, will look significantly worse than the on-demand version, which they used two-pass encoding on.",
"a lot of cable stations are actually sending 1080i instead of 1080p. URL_0",
"1080p only represents how many pixels will be getting information. it has nothing to do with the quality of the information. For example, I want to show you a 1080p picture of car. If I'm terrible at my job, I'll give your TV information to make every pixel show purple. All you see is a purple screen. It's still 1080p (each pixel in your 1080p display has obtained information), but the quality of the information is so bad that you don't see the car. If I'm good at my job, I'll give your TV information to make the 1080p pixels display different colors that make up the car. It's still 1080p (each pixel in your 1080p TV has obtained information), and of good quality (the colors of your pixels actually display a car). What determines the colors that your pixels get? Compression quality.",
"The resolution of a video stream says nothing about its quality. What matters is compression algorithm and bitrate. Broadcast TV uses a pretty basic and generic constant bitrate compression algorithm because broadcast TV works that way. Netflix uses a highly specific variable bitrate compression. Disclaimer, the information about TV being constant bitrate is a few years old and things might have changed, but I don't think so.",
"In addition to the compression that others have mentioned. It also depends on the source material, although your cable box is outputting 1080p, it doesn't mean that the images were recorded in that format (especially if you're watching older shows). So the box/provider will just 'enlarge' the images to 1080 which also makes them look terrible.",
"ELI5 version: Give an artist 10min, 1min, 10sec to draw the same picture, compare the results. Obviously the time isn't changing for the video, but the amount of data is. This can be compared to how \"fast\" they can draw, so more like; give them speed for one picture, nothing for the next, and a tranquilizer for the 3rd and keep the time constant. The first example in action: URL_0 Non ELI5 3 big factors: 1) The source material may be the same quality, but what you are getting probably isn't. 1080p is just the SIZE of the picture not the quality. Go look on piratebay as a reference, you can get a 1080p movie encoded by YIFY for like 700mb, you can get the same movie from most others from between 8-15gb. Both are going to be \"watchable\" but the 700mb one might be a little pixilated, the blacks might be splotchy etc. Look up \"bitrate\". This is the amount of data per second in the video file. 2) Netflix is a dedicated connection, it can send you a bunch of data as quickly as you can receive it, and change the quality on the fly. You will often see a stream start off at \"ok\" quality for a few sec and then bump up to higher quality. Rather than waiting 30sec while it says \"buffering\", they give you a lower quality version to watch then switch whenever its ready. The assumption is nothing important is happening in the first few min anyway. A tv channel on the other hand is broadcast, every subscriber gets the same thing so they have to cater to the slowest persons connection. 3) TVs are dumb, computers and smart tvs (tv with built in computer) are not. TVs display what they are given. Computers can process things, so the provider can send the video compressed, knowing your computer can uncompress it to watch. Would you rather sleep on a sleeping bag or an air mattress if you didn't own an air pump? Does owning an airpump to inflate it change your decision?",
"Broadcast TV whether cable or satellite is at most 1080i. Even if they tell you it is 1080p, it is only unconverted from 720p or 1080i.",
"Yeah, but there's something wrong with Netflix's audio. I think they compress the shit out of that, because for some reason, I can never understand what people are saying. And it's not a volume issue, there's just something wrong with the clarity.",
"Most cable companies broadcast on 720 or 1080i, not 1080p. Netflix does broadcast some things in 1080p.",
"If you use an antenna for local channels, the HD is about as good as you will find. Cable recompresses the video considerably.",
"Most of the reason comes down to the codec used and if it was encoded with Hardware or a CPU. Most cable and over the air broadcasters deal in bulk realtime video, which needs to be encoded right now and realtime encoding is never efficient. With cable they might have to re-encode 100s of channels at a time so it fits on their cable bandwidth, so they don't give each channel much bitrate. Cable would use less efficient and cheaper hardware encoders that can deal in bulk. They are also probably still encoding with the MPEG2 standard from 1995, which was used for the DVD. While Netflix uses codecs for H.264 (from 2003), codecs for H.265 (from 2013), VP9 (used for YT), and they are testing out the newest standard AV1. Every single one of these standards are better than old MPEG2, and Netflix has the time to do CPU encodings instead of hardware encoding.",
"No one is mentioning that netflix gives a copy of the entire movie database on a small server rack to every isp or most of them anyways. Instead of going long distances accross many dozens or hundreds of machines to stream your movie its a direct feed to your isp instead so the compression, bitspeed, and encoding can all be optomized and efficient",
"Most (if not all) 1080p on cable is upconverted from 720p or 1080i. It is all done with lower quality compression than Netflix can use, as well. Additionally, Netflix only has to concern themselves with total data bandwidth for active streams based on what they pay for, whereas cable has to manage internet, video on demand, and live channels, all within a finite *frequency* bandwidth (typically ~1 GHz, but it varies between systems) Edit: One \"channel\" is 6 MHz. When I left Comcast, they could fit 4 HD broadcasts per channel, or 30 Mbps of internet download speed, or 2.5Mbps upload speed. So if you have 1Gb cable internet available in your area, it is probably taking up 200 MHz of that 1000 MHz range they have. 100 Mb upload speed is going to be another 100-200 MHz (surely they are pushing more now than they used to). That's 30-40% of total spectrum available going to internet service. Source: was Comcast employee for 12+ years, cable technician for 9 of them.",
"Cable is stuck using old standards, that is it more than anything. Cable has to send everything in a format that the least of the equipment can handle, so that person who is using a cable box they got 20 years ago (some of the first HD boxes) is the limiting factor. Netflix can send you the best your system can handle. In the last 20 years compression technology has advanced by staggering amounts. Cable is sending out early DVD technology level video, pushed to force 1080, and then compressed to fit whatever can be spared for that channel. Netflix still has that technology level as the minimum, but what you are seeing is some of the latest video compression technology. Netflix has some content available in H.265 and is rolling out AV1. AV1 in particular is at the cutting edge. Both 265 and AV1 offer vastly superior video quality in the same bandwidth and both have additional room for improvement over the next few years. Tldr. Cable is using technology older than you are, and it shows",
"OTA (Over The Air - antenna) channels use 1080i, 720p, or 480i typically in the USA. This can be much different in other countries. The signal is a MPEG-2 video stream at up to 19.39Mbps (megabits, not bytes). If there are sub-channels like 9-1, 9-2, 9-3, 9-4 etc in your area, the stream's bandwidth is typically divided across those channels, though sometimes stations deactivate sub-channels at different times of day. All that said - OTA channels look really good because of this. They are mostly low-compression, high bitrate video streams on an easy-to-decode format and look fantastic. But they are limited because of the frequency each channel must be given (similar to FM stations, each OTA TV station must have its own frequency, though they typically do not talk about it because they are large numbers and hard to remember instead of like 3-1, etc) So, why do cable channels look worse? Because although the DECODER at your end (your cable box) is telling you that it's \"1080p\", it's a lie. They might be sending a 1080p signal over the HDMI cable into your TV set, but in reality the video signal is a highly compressed MP2, MP4, or other proprietary video encoding method. They must send all the video streams to your TV simultaneously and the spectrum isn't that large when it needs to be shared amongst all those channels. So, imagine the info I gave you above regarding OTA signals- if you can see the quality getting worse when a single channel is split into 4 sub-channels (like 9-1, 9-2, 9-3, and 9-4), imagine what would happen if they split it into THIRTY sub-channels. These channels are always running at all times. That's what your cable company does. Now, as for Netflix and other internet based connections, they don't \"split\" a channel into interwoven subsections of constantly streaming (whether you are using them or not) data. Instead, your internet connection (for the most part) only delivers the ONE thing you're asking for. You send a signal to Netflix saying \"I'm interested in this video\" and Netflix responds with the data. It's still a compressed 1080p stream, but they have more room with the single dedicated stream of data to send you a picture with decent bandwidth. Here are some pictures of OTA resolutions I just took here in Denver. Remember - if those channels are broadcasting at that image quality - your cable provider is receiving them at the same quality. So if they then send you that station over the cable line, the signal doesn't magically turn into 1080p even if they claim it does. It is really in the same format as OTA, but even more compressed and therefore worse quality. URL_0"
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a4gzqg | Signs on the freeway that say "Speed enforced by aircraft" | What aircraft are these? And how are they enforcing speed? I assume it's not armed drones decimating speeding minivans. | Technology | explainlikeimfive | {
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"It just means that there may be an airplane or helicopter overhead checking your speed. If you're breaking the limit, a car will be dispatched to pull you over. That said, it's almost always a bluff. Enforcing speed limits by aircraft is simply too expensive and not done very much.",
"In Virginia they tried it. They basically drew giant white lines on the interstate and put a stop watch on your vechile and a mile down the road they had another giant white line with about 20 troopers waiting. If you crossed that line faster than a specific time you must have been speeding. Utter fail. They could not issue enough tickets fast enough to justify the cost of operating the aircraft. So even if you see the signs in Virginia it pretty much means nothing.",
"There are horizontal white lines in the road that are placed a certain distance away from each other. If cars pass those lines at a specific rates the aircrafts can calculate your speed and tell if you are speeding.",
"It used to be light engine planes or helicopters, but now I would assume that it's drones hovering over the treeline. Either way, they're mainly going after racers, as it's still a time and traffic drag to pull you over and give you a ticket.",
"It means they might have a helicopter or something that is involved in reporting and collecting info on speeders. Or it may be that something like that is allowed by law so even if they don't actually do that they post it, just to keep some of the would-be speeders nervous about planes overhead or something.",
"It's also much easier to monitor multiple roads at once or long stretches of roadway, from the air. Especially if those roads are out in the middle of a desert. I've heard several stories of people going upwards of 150 mph in the desert. Then arrive at the next town to get pulled over and find out a plane was watching them the whole time.",
"Georgia and Florida do it every day. There are lines painted across the road and a pilot times you with a stopwatch. I’ve known and worked with these guys. One plane & pilot - Less than $200/hour Four cars on the road, two tickets per hour per car - minimum - at $200 per ticket, gives you 1,600 per hour. [The state makes money.]( URL_0 )",
"I’ve been caught speeding by an aircraft. I challenged it in court and the police provided transcripts proving that they maintained visual contact with my vehicle from the time I was caught speeding to the time I was pulled over by the officer in the cruiser. They had multiple cruisers at a certain point and were blitzing a certain section of highway. Rare but it definitely happens."
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a4h1p3 | Why does internet speed fluctuate? i.e., why does it go from 25 mbps to 30 mbps? | Technology | explainlikeimfive | {
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"Side question: Why does my computer lie to me and tell me I have full connection yet I can't load any web sites?",
"Along with what others have mentioned, error correction plays a large role in it. We don't often think about the physical reality of data transmission, but on a very basic level it's actually electrons (or, increasingly, photons) zipping along the surface of a wire and it turns out a lot of things can happen that keep them from reaching their destinations in a timely fashion. The actual electric signal that makes it to the far side is generally pretty beat up by the time it gets there, and one of the biggest hurdles to developing reliable digital communication was developing a good system of error correction and redundancy (i.e., transmitting the same thing numerous times so that enough of it would arrive intact that it could be pieced together). And although we've solved that *enough* to rely on digital communication, it still interferes with those communications enough that it can affect how quickly something comes across the wire. It's also random enough (technically *chaotic*, not random) that its effects appear as apparently random fluctuations of throughput. As a side note, when you read stories about people developing \"a faster Internet,\" that's generally what they're working on: better error correction schemes that allow the same datum to be transmitted with less redundancy, ultimately allowing us to transmit more data per unit time."
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a4h1xo | Why does a dead laptop turns on right away when plugged in but a dead phone must charge for a few minutes before turning on ? | Technology | explainlikeimfive | {
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"A laptop can run directly off wall power; a phone cannot. Even when a phone is plugged in, it's actually running off battery power. So when you plug in a dead phone it takes several minutes to build up enough charge to power itself up.",
"That’s iOS-specific. If your device suddenly looses power it may leave filesystem in inconsistent state. To avoid that phones and laptops automatically shut down before battery is completely dry. Most android phones can be forcefully started even in this state, but iOS doesn’t start unless phone has enough power to both boot and shutdown again gracefully. Edit: and yes, most android phones do run just fine completely without battery, powered by usb cable.",
"Erm, I suspect the answer here is \"because Apple\" - my Mi A2 will turn on immediately, and so will the Mi A1 I had before (which, having been left uncharged for a couple of months you'd expect to need a while - nope!) Edit: down votes? For not only stating a fact about my current phone, but getting out of bed, finding my old one and confirming it? Well, fuck you apple fan boys. I hope your many dongles get stuck in your many crevices."
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a4kvi7 | How does cellphone reception work? | Does a cellphone (3G/4G) tower send radio waves in your general direction, or does anyone receive every wave but if it's not for your phone it decides not to do anything with it? | Technology | explainlikeimfive | {
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"Phones emanate in all directions, they do not have directional antennas or you would have to specifically point it toward a tower to use it. So every thing is just floating out there and other cellphones just ignore it because it's not addressed for them. Towers may have general antennas that radiate everywhere, or directional ones that cover specific cones of space, but with directional antennas they'll still have enough installed to cover a 360-degree radius all around. Other cell phones also ignore any thing not addressed to them.",
"To add, other phones will ignore things not addressed to them but you can buy or make a signal sniffer to capture all that traffic. That's why modern cell phone data is encrypted. (Note: using a device above to capture someone's cell phone data is illegal in the U.S. even if it's an accident. Illegal in many other countries too)"
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a4kxh9 | why have the reposted pictures less quality than the original post? | Technology | explainlikeimfive | {
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"Iirc: whenever you post to, say, Facebook, the platform compresses the picture, by default. So, you take a pic with your phone and post it... Suppose its quality is defined by a value which is defined at 1'000'000. You post it and it goes to 100'000. Someone saves it, and reposts it, and it goes to 10'000. Someone else saves it, reposts it, and it goes to 1'000. And so on."
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a4l2yf | Why do certain setting changes on your computer or phone require the device to restart and other don’t? | Technology | explainlikeimfive | {
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"If you want to change your car's tires, you have to stop driving it while the work is being done. The tires are fundamental to the car's use, so they can't be changed *while* the car is being used. You can change the station on your car's radio any time you like, because the radio isn't fundamental. Same thing - if the setting is going to change something that's fundamental to how the computer is working, then rebooting it is the equivalent of putting it up on a lift to change the tires (just much faster!).",
"Some functions ar so deeply integrated into a system that changing their behaviour with a setting needs the restart of a setting. (For example changing language requires re-reading all written data in a different language. Instead of making the software capable of changing it's visible data \"on the fly\", it is easier and more stable for the programmer to just require a restart, when the software instead of reading english data, it reads chinese, the first time it loads, not after it has already started)"
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a4o8w9 | What's the difference between JPG, JPEG and PNG? | Technology | explainlikeimfive | {
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"JPG and JPEG is the same. It is a file format for pictures with pretty good compression, which works best on photos. Compression rate is variable and can be chosen when saving the picture. Higher compression means smaller files (and thus faster downloads) - but at the cost of reduced image quality. This is, because the way the compression works, the JPEG image is not 100% identical to the original. Individual pixels may have slightly different colors than before compression. Opening a JPG, editing it, and saving it again (re-compressing it) will cause increasingly visible compression artifacts, as those losses/errors compound. PNG on the other hand is a lossless format. It guarantuees that every single pixel remains exactly the color it was - and that you can edit the file and save it again as often as you want without any loss in image quality or visual degradation. This of course means that PNG cannot compress files as much. High resolution photos will have significantly larger file size when stored in PNG format, as opposed to JPG format. PNG also supports transparency, which is not possible with JPG."
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a4ql7t | Computers at workplaces of major corporations warn us that upon logging in, we agree to be monitored. How are we actually being monitored? | Technology | explainlikeimfive | {
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"Generally logs are kept regarding what sites each user visits and if you have permissions to download files that's also logged as well.",
"I've worked in shops that in addition to standard network logging, system logs, etc. we've also had software that does keystroke capture, screenshot capture, and remote viewing of whatever was actively happening on screen. And since it's their equipment, it's generally legal (in the US). Ethical is a different statement...",
"IT friend had a high pressure large company gig that got slow every once in a while. He scanned random hard drives on the network looking for porn (jpegs, mp4, avi). Caught several guys - could have been fired. Spoke to them privately and the files disappeared.",
"They track your network packets being sent from your computer to your company network/firewall. The thing to keep in mind is depending on the size of your company it can be a lot of data do they don’t keep it very long. However, if they are building a case to fire you they may use your network browsing as one of several reasons. Also all your company email is copied as well. So if you get a dirty joke or porn links your company as a copy of it. Don’t do anything at work that could get you fired. If possible RDP to your house computer and do the bad stuff from there. 😁",
"Usually it's two part, they have a proxy, they do have logs of what websites your visit, and two, they are telling you that they can and will look at what you're doing. In practice, I think most are like where I work, they have logs and can see what you did, and they have the computers configured such that IT can see everything that you're doing right now. They probably won't look at the logs, and probably won't look at what you're doing, because honestly you're not that interesting. But if someone asks or they get a formal complaint, they'll look, and they won't tell you. A formal complaint could be the CEO saying they want anyone looking at porn fired, to the IT VP wanting a list of everyone who wastes company bandwidth with youtube."
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a4uhnk | What is YouTube Rewind and why is it so widely hated? | Technology | explainlikeimfive | {
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"Youtube rewind is a video that youtube makes near the end of the year to highlight what was popular and important in the past year. Now, why it is so widely hated, there isnt a single answer for that. A few reasons stated are: too much political \"propaganda\" in this year's YT rewind. Overlooking a lot of YT's memorable moments; pewds vs T-series. Demonetising videos that have trans-focused content, yet they claim there was a large progress in social acceptance. What i think the reason fot a lot of people is, is that YT is becoming too distanced from its content creators and too much company-focused. A ton of creators arent acknowledged in the videos and the same people keep getting starred in the videos. Pewdiepie does have a great explanation in a [video]( URL_0 ). Although it is paired with some pewd-esque crazyness, he does bring up very good points and explains it better than i think i can. Also, i'm sorry if this isnt very ELI5... Edit: as others mentioned; yes, there are obviously people that just dislike it because others do so. You will alwayd have those people, but i dont think over 6million people are like this.",
"People dislike youtube rewind (including me) because it doesn't represent the past year. I watch youtube daily and i check out the trading page daily as wel so i don't just watch my subscribed channels but i don't recognize anything that has been iconic in the past year except for fortnite."
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a4vknj | How do guns actually work | More specifically the trigger mechanism and chambering, not the obvious explosion propels bullet. | Technology | explainlikeimfive | {
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"They're all built around a primer that creates a spark when struck and the spark ignites the gunpowder inside the round propelling the bullet through the barrel. All modern guns are designed to strike the primer hard enough to create with a firing pin when the trigger is pulled and then contain the resulting expansion so the bullet accelerates. The exact method used to convert the trigger movement into firing pin movement is called the \"action\" of the gun and it varies by the design of the gun, but often involves a fairly strong spring being held in place by an edge that's connected to the trigger (when it moves the spring is released and the firing pin is allowed to move forward). The US army [made a very nice video with oversized props]( URL_0 ) explaining a general small arms rifle cycle of operations. Once you understand the general steps, you can usually intuit how a specific other weapon works, from an operation gif or video (similar parts do similar things with some differences in the linkages and safeties).",
"There's a lot to cover, so let me know if you'd like anything clarified The cartridge is constructed of a bullet, the case, the powder inside, and a primer that gets struck to light the powder. The simplest scenario is a revolver with a hammer. The hammer is cocked back until the trigger catches a notch in the hammer. There's a somewhat pointy pin on the hammer (I guess you could think of it more like a pickaxe than a hammer) that pierces the primer. In a more complicated scenario, older submachine guns have what's called an open-bolt operation. They typically have a large hunk of metal called the bolt that moves within the body of the firearm. Like the hammer of revolvers, these hunks get held back by the trigger. When let go, the hunk of metal strips a cartridge out of the magazine and then slams it into the chamber. There's a fixed little piece of metal on the front (called a fixed firing pin) that pierces the primer. The weight of the bolt itself keeps the cartridge in the chamber long enough for the pressure to lower, and then the force eventually overcomes the weight and forces the hunk of metal back, extracting the cartridge and starting the process all over again. The trigger in this case is simple, it's just a pivoting piece directly connected to the trigger called a sear. If you hold the trigger down, it never catches the bolt, hence it fires fully automatically. Else it stops firing when you let go, so it catches on the sear again. Now, things get a little more complicated when you start looking at semi-automatic weapons and closed-bolt systems. I'm just going to be brief and give you the gist of each. Semi-automatics involve a disconnector. There are typically two patterns: 1. Once you've pulled the trigger far enough back to fire, the sear resets regardless of if you hold the trigger down, requiring you to let go to fire again. 2. There's a secondary sear behind the main sear that catches the bolt / striker / hammer if you hold down the trigger, which then gets let go and held by the main sear after letting go of the trigger. Closed-bolt firearms have a lot of different systems but the gist is that there's typically the actual bolt and then the bolt carrier connected to the bolt. The bolt itself gets locked up somehow while the bolt carrier is free to move. The gases can't push the bolt back until it's unlocked. Somehow the firearm is setup so some of excess pressure ends up pushing the bolt carrier later, which unlocks the bolt and allows it to move. It typically either pushes a hammer back or a striker inside the bolt gets held back. In order for these to fire fully automatically, the sear is setup with a sort of second internal trigger where the bolt has to return all the way forward and to trip it before the hammer/striker is let go."
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a4xl66 | How is the new Ocean Cleanup Machine supposed to clean up trash without hurting wildlife? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Not clear. One of the big challenges with ocean plastic cleanup is that the plastic particles are about the same size, shape, and density as a bunch of living organisms. How is a filter supposed to tell the difference between a dinoflagellate and a microbead, or a plastic bag and a [salp]( URL_1 )? The Ocean Cleanup Machine has been criticized by a number of ocean scientists, who argue that it a) won't work as advertised, b) will become fouled by organisms so it can't do its job, c) may harm organisms in doing its job, and d) is poorly designed and may break apart to become more of the same plastic trash it's supposed to remove. URL_0 (And please do check out pictures of [salps]( URL_2 ), if like most people you've never heard of them. They're super common, and really make you rethink this problem. How do you clean up bits of floating plastic when the oceans are just *full* of delicate floating bags of transparent goo?)"
],
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"http://www.deepseanews.com/2014/07/the-ocean-cleanup-part-2-technical-review-of-the-feasibility-study/",
"http://www.antarctica.gov.au/about-antarctica/wildlife/animals/salps",
"https://theethogram.com/2015/05/04/featured-creature-salps/"
]
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|
a4xt58 | Do 4k panels weigh more than 1080p? | Technology | explainlikeimfive | {
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"text": [
"Not really. Think of a tile floor, you can have tiles of any size, they will still cover the same amount of floor space, even if it's tiny mosaic tiles no bigger than a dime. So that's the way it works with pixels. They have just found a way to make the individual units that make up the LED screen have a smaller size for each unit. Since there are now four pixels where there used to be one, the resolution increases, but since those four weigh the same as the older one unit they are replacing, the net weight doesn't really change."
],
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14
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|
a4ya5x | how does radiotherapy work? | Technology | explainlikeimfive | {
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"text": [
"Radiation damagea cells by randomly breaking DNA. If some important part of the DNA is broken the cell needs to repair it or die. Cancerous cells are worse at this kind of repair than normal cells, that's sort of what makes then cancerous. So radiation kills cancerous cells faster than it kills healthy cells. It is also possible to focus the beam of radiation so that it is much more intense where the tumor is than in other tissue. That reduces the damage to healthy parts. Kind of like burning a leaf with a magnifying glass."
],
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a4yrm7 | The reason that some updates and downloads HAVE to be carried out using Wi-Fi instead of data | Some updates require you to download them via Wi-Fi, regardless of whether you have a data cap or not. Is this to prevent those who do have caps from accidentally eating up all their data with a large download or update, or is their another reason? | Technology | explainlikeimfive | {
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"text": [
"There is no phone or computer OS out there that forces you to download via WiFi only. You always have the option to download via your carrier. All that has happened is that they have a hidden option somewhere in the relevant settings for that update that says \"Allow updates via WiFi only\" or \"Restrict updates to WiFi networks\" or \"Don't allow updates via cellular carrier\" or something along those lines."
],
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a50dbm | Why do a lot of movies and video games use the exact same sound effects? | I've noticed a fair number of them use the exact same door opening sound, children's laughter, baby crying etc. Obviously there's something I don't understand here, but I would think it wouldn't be hard to just open and close any random door and record that? Or to go to anyone with a baby and record it crying. I know these are fairly mundane sounds, but when they're used SO much you do notice after a while. | Technology | explainlikeimfive | {
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"text": [
"Same reason a lot of movies use the same props. Unless the exact flavour of door sound is critical to the plot, why bother to record it anew when you have terabytes of sound effects libraries pre-recorded and ready to load into Pro Tools? Recording takes time and effort. Most people will never notice, and even if they do, it's not important.",
"It's cheaper and easier to use premade sounds than to go out and hire the sfx team and such to make new sounds. Literally the main reason is money.... It also saves a lot of time and there is no reason for each movie to completely remake all of their sound effects.",
"To record a door opening, you need to go to a door, with a microphone and record the door. Then edit it, and you end up with a sound that is pretty much the same as the sample in your sound bank, which probably costs next to nothing. The hour or so it takes to do all the setup, recording and editing is going to have a certain cost in wages and overheads."
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a50dj8 | How do we keep in contact with spacecrafts like Voyager 1 which is millions of miles away from Earth? | Technology | explainlikeimfive | {
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"text": [
"Well it's not that different to making a phone call. Most communication with space crafts are done via radio communication. Radio waves travel at the speed of light which is about 300 000 km/s or 190 000 mi/s so even if the space craft is millions of miles away you just have to wait a minute or two to get a reply. There are other problems with communication of such vast distances how ever such as the radio signals will get weaker the further away from the source they travel. There are also problems regarding stuff that gets in the way like asteroids and planets and then there's also a lot of noise from stars and other celestial bodies which might drown out the radio signals over long distances."
],
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a514v6 | How did people protect against forgeries in the past? | Before the telegraph/telephones, how could people trust any documents handed to them? Like in the movie "A Knight's tale", wouldn't every scam artist just write his own nobility papers? Who is going to check for their veracity? And how? I guess a letter could be sent to the noble's castle but it could take months/years to be answered, assuming it even gets there. | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"By having trusted messengers, and by having everybody know everybody. If you're a nobleman, and you need to send a letter to the king, you think about whom to send to carry it, you first ask, *who among my family and inner circle, did I introduce to the king and his court, last time they visited this area?* I'll send him, so that people in court will be confident that the letter came from me, and not some impostor. Then you ask yourself, *is there anybody who **hasn't** been introduced? I'd better send him along, so he can meet some important people, and become a more useful messenger in the future.*",
"Kings, high nobles and government officials had signet rings for this purpose. A document was “signed” by pressing the ring into hot wax, transferring the image to the wax. This was done either to seal the document closed or to sign the bottom of the document, or both. The ring was usually an image of the family crest, which was unique to that family. In Japan and China, carved jade pieces were used similarly as stamps. Another technique was to have a duplicate copy of the document - one public and one sealed. If there was ever a challenge to the public document, the sealed one would be opened and compared."
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a51oox | The 20th century and earlier had a lot of Great Citywide Fires. How has fire suppression improved so much that we don't really have those anymore? | Technology | explainlikeimfive | {
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"text": [
"Large buildings are no longer made of wood. High-pressure firefighting water lines are laid throughout every large city, with hoses stationed in large buildings, and fire trucks in every district. Most large buildings are fitted with fire-suppression sprinklers throughout.",
"Building codes are always the first line of defense. Any larger building is built with multiple fire walls and systems to keep fires contained and not allow rapid spreading (like heavy doors that will close and isolated stairwells that are primarily concrete or steel), plus sprinkler systems in the buildings themselves. Places that are prone to burning generally toughen their codes a little bit more every time a catastrophic fire rolls through, so they become a little better at resisting it next time (there are always those who want to rebuild cheap and dirty, though, who fight any code upgrades)",
"Wood shingles were one of the worst reasons for the ‘spread’ of fires to other buildings... they were outlawed once that was discovered...",
"Total agree the captain. I'd also add that fire inspection is much more common now. Back in the day there wasn't as much knowledge about safe building practices nor was enforcement of \"code\" as common"
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a52ian | How does an automatic focus camera work? How does it "know" what to focus on? Compared to a manual focus of the same "type/parameters" and assuming everything else is identical with no special lenses/filters, etc., which one is inherently better than the other, quality-wise? | Technology | explainlikeimfive | {
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"text": [
"Most of this is explained [here]( URL_0 ) so I'll paraphrase what was written there. Light travels into the camera through lenses, where it hits a series of Light Sensitive components. These components allow the camera to see that light as an image represented by dots, or pixels, each with their own distinct RGB color value. When an image is correctly in focus, the definition between two pixels will be clearly defined, especially if they are two different colors. If the image shows a red dot, then a blue dot next to it, the camera knows it's probably in focus because the two dots aren't purple-ish. For it to find this level of focus, it starts by scaling the focus in one direction in tiny steps, quickly analyzing a group of pixels (typically around a pre-defiend focus point, usually the center of the screen) to see if their difference in color is sharper than before, and keeps going until it stops seeing a difference, then it starts going back until the image starts getting worse. It'll then go back and forth like this until it's confident that it's gotten the best result it can. This is pretty much the same way as how an optometrist works when they test your vision (asking which is better, 1 or 2, etc). A manual focus is usually better and what most professionals rely on, as automatic focus can be grossly inaccurate (like sometimes when a digital camera picks a group of pixels to focus on that you didn't want it to focus on)."
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a54rqx | How do game / software developers decide what to call each version update? e.x. v1.1 vs v1.01 | I've seen tons of different version update formats, usually with decimals involved. I sometimes see version updates with multiple periods, such as "v1.01.2". How do developers decide if an update is a .1 update or a .01 update etc. , and what do the occasional extra periods mean? | Technology | explainlikeimfive | {
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"Often (but not always) the versions are numbered by the [MAJOR.MINOR.PATCH scheme]( URL_0 ), which is widely used. MAJOR means some significant changes in the software, like architecture or development approach changes, often making it incompatible with the previous versions. MINOR mostly adds some features, but without any drastic overhaul. PATCH usually marks bug fixes or any minor corrections, without any changes to functionality.",
"Everyone is different but the general practice is this: `major.minor.patch` This is called \"semantic versioning\" and it's been raining more traction recently. Major releases happen more rarely (annually, maybe shorter, most likely longer depending on the industry). Major releases contain what are called \"breaking\" changes, where users must change their workflow or new projects are incompatible with older versions. Minor releases usually don't contain breaking changes, and they really shouldn't unless it's a security issue. These usually contain new features that don't break anything, or fulfill what are called \"feature requests\" where users need something and the developers comply. Patch releases don't contain any breaking changes or new features, so they're typically just bug fixes.",
"It really varies from developer to developer, sometimes it's not even consistent within a developer. Some don't even bother with the v1.01 format. My company for example does {3 letter product code}12p10 With the first number being a set of new features, with the second number being patches to those new features when they break. No new feature is added if you increment the second number. I suspect many developers are doing that for v1.01.02 type numbers. Many developers publish what the version numbers mean. Others can only be gleamed through the patterns. Other's just don't care.",
"With the software that I work with, the first number refers to the year we’re releasing in. The second number is the major release. Think of this as the release that is ‘planned’. The third number is usually a patch number. This is when something has gone wrong in the major release that needs to be fixed. We also have a fourth number after another decimal point, which is the ‘build’ number of that release, patch etc (but this is generally only used internally). For example, the second planned release of 2018 would be 18.2; and if we need to release a patch, this would be 18.2.1. Please note, lots of software houses work very differently, not many use years as we do. So the first number is the major release which just increments up, the second number is a minor release. It tends to be the product owner’s call on what constitutes a major or minor release, but generally, big new feature = major, minor features and bug fixes = minor.",
"There is one very popular system called \"semantic versioning\", which works like this: - The first number increases when the program changes the way it interconnects with other programs, potentially breaking features other programs rely on. - The second number increases when the program adds features or changes how features work for users, but in a way that doesn't break interconnectedness with other programs. - The third number increases when bugs are fixed or security problems are closed, without adding new features or breaking things other programs connect to and rely on. - When a number increases, the subsequent numbers roll back to zero. This system is nice because it lets you decide whether you want to update or not. Going from 1.0.0 to 1.0.1, yeah, you almost certainly want to update, because it fixes bugs without changing much. 1.0.1 to 1.1.0 means there'll be some new features and improvements, but nothing big will break. 1.1.0 to 2.0.0 means there's a fundamental change in how some things work and you'll want to do research first to make sure everything will still work the way you expect. Not everyone follows this system, though. Sometimes, software will just use YEAR.MONTH.DAY (eg 2018.05.10). Sometimes, they'll just use two numbers (eg 15.2), bumping the first number for updates that are 'big' and add a lot of new stuff, and bumping the second number for small patches and fixes. One concern that affects versioning is whether you'll maintain old versions. For example, Windows 10 is the current version, but Microsoft still publish security updates for Windows 7 and 8, just not new feature updates. They might publish Windows 10.2.308 and Windows 7.5.118 on the same day (making up version numbers here for simplicity's sake). If you want to keep offering security fixes for old versions (which is very important to millions of people!) you can't just use a \"Windows version 23712\" or \"Windows version 2018.05.10\" system. However, if you're writing say, the server software that hosts World of Warcraft or something, \"version 2018.05.10\" would be fine, since there's really just the one latest version that matters."
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a54skd | Why is internet speed in underdeveloped/developing nations slower than that of developed nations? | Technology | explainlikeimfive | {
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"text": [
"It takes an investment ($$) to build out the infrastructure for high speed internet, like fiber optic cables. Investors don't want to sink a lot of money into developing countries because they don't expect as great a return i.e. profit.",
"This is kind of a big question. At the end of the day it's more expensive and less profitable to build the infrastructure to deliver the same bandwidth. The reasons are complicated. The ideal place to build high bandwidth networks would be high population density areas with existing telephone networks and regulatory frameworks to improve them. Essentially if there are already phone lines, the distance between nodes is small, and the government has a defined way to build on top of that you can easily go in and add broadband. This is why South Korea, Taiwan, urban China, and Japan have some of the fastest networks in the world, despite industrializing (or re-industrializing) in the last few decades. There's also the issue of power. Data can only get places with reliable power to the home. India is only a few years removed from regular brown outs, and much of Africa is still without reliable power. Then there's physics. When you don't have existing telecoms lines it's cheaper and more effective to build cellular networks (wireless data). This is how much of the developing world consumes data, especially in Africa. The catch is that the inverse square law applies to wireless signals, meaning that the further from the tower you get the much less bandwidth is available. Then theres international trade. Only a handful of companies actually manufacture the components to actually build the infrastructure, and it isn't cheap. That plays into the final and possibly greatest hurdle: government. It is against the law in most developed nations where the wireless manufacturers exist to bribe foreign officials, and the penalties are immense (talking corporate death penalty). In a lot of the developing world, it is impossible to build without the government's OK, which means officials from every level collect \"fees\" (bribes) to process paperwork to even start construction. To avoid penalties, western businesses operate through middlemen (\"local distributors\") who actually handle point of sale and any government \"fees\" associated with it. All of that creates overhead, and it's really fucking shady."
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a57igv | why are car batteries already "good enough" that they haven't changed much while all other battery technology has improved? | Car batteries look basically the same in cars from decades ago, but mobile devide batteries are much smaller, stronger etc. So what is it about the standard car battery technology that has stood the test of time? | Technology | explainlikeimfive | {
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"Car batteries require a very powerful, but short burst of energy to get the engine started. This is very different of what we expect of other battery use cases: small size and long endurance. In that sense a car battery acts more like a capacitor than a battery. Therefore car batteries are still lead-acid based instead of Lithium. The battery in electric vehicles is of course a Lithium one. There has been some improvements to avoid battery failure, but in essense there is little to no need to innovate lead-acid batteries.",
"Think about the environment that a car battery operates in. It could be -20 outside, or 45c, and the battery needs to operate, not catch on fire, and not have it's life severely shortened from environmental factors. Lead acid batteries are very old technology, but the reason it's still used for things like UPS power supplies, deep cycle batteries for boats, and automobile power, is because they operate under a wide range of conditions, reliably, and safely. They can take the heat and the cold, and still produce large amounts of cranking power (amps). They are also able to discharge and recharge repeatedly without damaging the cells. NIMH batteries lose their charge over time, and lose capacity quickly with frequent discharge/recharge cycles. Lithium Ion batteries are very delicate, prone to high and low temperature failure, and they can explode. They also have a limited number of charge/discharge cycles before losing capacity. But you say, electric cars use them! This is true, and they make up a considerable portion of the total cost of the vehicle. They don't last very long, a half dozen years or so. And they must use a significant portion of their power in order to keep the batteries at a safe operating temperature. In the cold, this means heating the cells, and in the heat, it means pumping heat out of the battery compartment. This is do-able when there are hundreds of battery cells with a large storage capacity, but less so when it's only a handful of cells. Would you want a battery that goes dead keeping itself at a stable temperature, and is more costly and expensive?",
"Some people have replaced their car batteries with supercaps, and they end up saving a bunch of money because they last significantly longer than car batteries. Edit: You still need a tiny lead acid battery to hold a charge for a longer period of time, but supercaps hold enough energy when charged to start the car. The alternator is enough to keep everything charged though."
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a59evy | How does a washing machine actually clean clothes? | So I get that hot water and soap help, but how does the spin work to scrub the clothes? | Technology | explainlikeimfive | {
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"text": [
"The spin cycle isn't for cleaning. It's to remove most of the water. The cleaning cycle twists the drum back and forth to move the clothes, soap, water around and the agitator (the thing in the middle) helps make bubbles and make things rub against each other. Basically it makes the items scrub against each other which removes the dirt."
],
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a59zm3 | Why do miniguns have to "rev" or spin up before being able to fire? | Technology | explainlikeimfive | {
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"text": [
"A minigun is actually unloaded until you push the trigger. It can take a fraction of a second for the feed mechanism to get up to speed so it can load the chambers of the gun until the gun actually starts firing. And you do not want the feed mechanism to go at an odd speed as it is possible for the components to become misaligned and the gun will jam. The motors in the miniguns are therefore quite powerful and spins the gun up to speed in just a fraction of a second. However this can be noticeable if you try to aim it at fast moving targets. But it is nothing like the delay you might see a minigun in some popular video games have. This is done more for game balance purposes to make the minigun less powerful.",
"To be able to reach the needed rotation speed without the risk of bullet going somewhere it shouldn’t go.",
"I have no hands-on experience, but I’ve been told by people that do, the ‘spinning up’ is a video game creation for adding tension/drama. Mini guns rotate using an electric motor, which spools instantly. Again, just what I’ve been told.",
"To expand a bit on the previous answer: Miniguns have a set of rotating barrels that rotate in front of the chamber of a machine gun that fires at an absurdly high rate. The reason for this is to prevent any one barrel from overheating. The first multi-barreled rotating firearms were gatling guns, and the action on these were less automatic and more of a crank; you would rotate a lever handle and for each, say, 1/6 of a turn, the barrel assembly would rotate and then at a set point a round would be fired (along with all of the ejection and whatnot being handled by that rotation). As we got more advanced, now that is handled by motors and math, so that holding down the trigger waits for the barrels to get up to speed, and then the minigun fires only when there is a barrel in front of the chamber ready to fire the bullets out. If this didn't happen, either there would be a lower rate of fire (which, for the applications a minigun is/was used for, is not desirable as it results in lost ammunition, essentially) at the cost of more mechanical complexity (a rapid-fire system that speeds up as the rotation of the barrels does is more complex than one that goes at one speed all the time and waits for the barrel to speed up to that one speed), which is the enemy of reliability, especially in a fairly complex gun like the minigun, OR there would be bullets getting fired into the frame between barrel alignments when it was speeding up, which is not good (although your target probably disagrees there)."
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a5al7m | Why is 2-D animation more timeless than 3-D? | I guess the more straightforward explanation is that 3-D has another dimension, making it more complex. It’s just that every time we see a cgi heavy “marvel”, it inevitably shows its age least a decade later. But movies from the 40’s still look splendid. | Technology | explainlikeimfive | {
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"There are a couple of reasons. A big is like someone else said, CGI often aims to be realistic, while lots of 2D animation is stylized. A stylized animation doesn't look bad compared to a realistic modern animation because the former wasn't trying to be realistic in the first place. On the other hand, a piece from 10 years ago that tries to appear photo realistic will look archaic compared to a modern photo realistic animation. Another factor is that 3D is a lot more reliant on technology. Lots of new technology has been used to enhance 2D animation, but at the end of the day you're looking at something someone drew, and humans in general aren't better at drawing than they were in the past. On the other hand, while 3D still involves a lot of skill and artistry, it's also constrained by computer power, and computers have become *much* more powerful in the past few decades. It's kind of like how modern paintings aren't much better than renaissance paintings, but modern photographs are vastly better than the first photographs."
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a5avb8 | What type of motor is used to make phones, controllers, etc. vibrate? | Technology | explainlikeimfive | {
"a_id": [
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"Usually it is just an electric motor. Nothing really special about it, except that instead of driving a gear or something it has an unbalanced weight on the end. That weight being slung around causes the motor and whatever it is mounted on to vibrate.",
"Among the many components inside the phone is a small motor. The motor is built in such a way that it is partially off-balanced. In other words, a mass of improper weight distribution is attached to the motor's shaft/axis. So when the motor rotates, the irregular weight causes the phone to vibrate"
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a5axit | how does placing a bowl of water next my radiator increase the humidity in the house? | I thought that to have vapor in the house, I need to have a boiling point of water. That is the vapor pressure = atmospheric pressure. If I place the bowl of water next to my radiator, it is no where near boiling, yet there is a noticeable decrease of my water in my bowl. Can someone shed some knowledge to me. | Technology | explainlikeimfive | {
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"Ever take a hot shower and the mirror is all foggy? The water isn't boiling but water vapor still gets into the air.",
"Boiling water creates a lot of evaporation, but even in room-temp water, there will be a small amount of ongoing evaporation as water molecules near the surface collide and get enough energy to \"escape.\" The more heat the quicker this happens. Boiling is not the mechanism, it's just an extreme version."
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a5b2mn | How do fingerprint scanners on phones work? | Yes i've searched for this answer and found the same question (#7), but the answer did not really sastisfy as a ELI5 and therefore me does still not understand.. | Technology | explainlikeimfive | {
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"> There are three primary types of fingerprint scanners on the market. The one used in smartphones is called a capacitive scanner, as it relies on a property called capacitance. Basically, the scanner plate (typically a pad somewhere on the phone, often built into the home or power button) passes a small electrical current through itself, and when you press your finger to it, the pattern of ridges and valleys changes the capacitance through the array of cells that make up the scanner. The scanner then stores, not the picture of your fingerprint, but the pattern of capacitance changes that your finger causes. It can then check that stored pattern against a new pattern generated the next time you touch your finger to the plate. This is the same as other scanners on the market, but if you have the space and you want a more accurate reading, you'll generally use an optical or ultrasound scanner. Edit 2: source of this quote is u/toxiclay Most smartphones use a capacitance scanner because they have the hardware already built into the phone. For instance your touch screen is a giant version of a capacitance scanner (that's how it actually detects the touch if that makes sense) Optical scanners (like in many laptops) will use infrared light and catch the reflection of the light, then passing it though a filter it will make everything touching the scanner appear white and everything that has air between the scanner appear black producing a negative image of the fingerprint and then run comparisons via that method. Ultrasound fingerprint scanners I haven't seen as much but then precisely measure the distance between the scanner and the finger which produces (essentially) a 3d model of the finger (including fingerprint) that will allow for comparisons. These are simplifications and neither optical nor ultrasound sensors have been used on any phones that I have seen. Edit: the reason why high precision capacitance arrays work for fingerprint scanning it because capacitance is inversely proportional to the square of the distance meaning even tiny changes in distances can produce massive differences in the capacitance. The problem with capacitance arrays is that they have parasitic capacitance and as a result fingerprint scans and other high precision scans are blurry (relative to other methods) which means they generally have a higher tolerance and thus are slightly less secure than other variants, however that's a completely different discussion."
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a5bodv | How you can have the notification saying "new password cannot be old password" despite being told your old password is wrong | Technology | explainlikeimfive | {
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"There are a few possibilities: * You just made a mistake when entering your password the first time. * The password is case sensitive, but when it tests against old passwords it's case insensitive. So if your password is microwave and you login with Microwave it will be wrong, but when you try to change your password to Microwave it's still an old password. * You used that same password previously, it's just not the password you're using now."
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a5cgbk | How does banning Huawei/ZTE from 5G network combat spying? | 4G speeds should easily be able to to upload secret audio/video recordings within managable timesframes. | Technology | explainlikeimfive | {
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"Huawei and ZTE are specifically using their hardware to spy on customers, and possibly worse. They are both doing it on behalf of the government of China for (as of yet unknown) economic, military, and political use by the Chinese govt, and its way out in the open now. The US has (allegedly) known about backdoors and spy stuff for various computer hardwares made in China for a long time, but its becoming more public after some recent events and various countries are taking their own routes to combat this. Basically, they are saying \"hey we know what you are doing, and we are no longer going to be in business together in the future\""
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a5d2xf | What features give bullets power, effectiveness, and so on, and why there isn't just one best bullet? | The context behind this was this: I was reading about the FN Five-seveN, which - true to its name - uses FN's special bullet, a 5.7 x 28mm cartridge. After a brief period of consideration (and a little bit of googling for inch conversion), I came to realize a few things. 5.7mm (0.224 inches) is *puny*. I vaguely remember reading elsewhere about the .22LR round, which is one of the smaller rounds out there, and terrifically "weak" (or so I think, correct me!), used for shooting pests, plinking, and generally being used recreationally. For those in the audience that struggle with math, 0.22 inches is just barely less than 0.224 inches - and yet the Five-seveN sees usage in military and police forces all around the world, so it's clearly powerful enough to see actual use. My question here is: why is the 5.7 so good, being so small? Next consider the .45 Auto, a bullet almost double the caliber, and coming very very close to the enormous .50 caliber, the stuff of popular myth a la .50 BMG machine-guns and .50 AE Desert Eagles. The .45 is another handgun round, presumably relatively powerful as well. I'll throw 9mm Parabellum - the world's most cherished modern cartridge - into the mix as well, and 9mm coming a hand-and-a-half larger than 5.7mm. My question here is: why so large, and how does this translate into effectiveness? My final consideration was the caliber of a number of rifle rounds - the .30-06 and the other 7.62mm rounds, the .308 Winchester, and others. I read around on Wikipedia and they always mention things like "the 5.56mm round is used in smaller, less powerful carbines, while the full 7.62mm is used in the rifles" and I understand the relative comparisons, but all of these common calibers are vastly smaller than the .45 auto, a pistol round, and yet presumably are more powerful, being outfit for a rifle. So: Why so small? My question might be this, then: what's the advantage of a .45 over a 5.7mm, why would you ever design a .45 pistol round when perfectly acceptable power can be attained by a diameter of .308, and don't tell me that the size matters when we've got a 5.7mm round making the (heh) rounds? What is the real motivation for the design and choice of caliber for all of these, what are the factors that go into deciding the power of a bullet, and why did anyone think that the Desert Eagle was necessary? EDIT: And I apologize for being a flair noob - couldn't decide between physics and engineering so I went with "other". | Technology | explainlikeimfive | {
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"There's a lot of personal preference for handgun rounds, but for rifle rounds it is much more established Big bullets like the .308 Winchester and .30-06 will travel really far and will take out a person with a good hit without a question, they're really good for long range engagements, but most combat takes place at less than 300 meters so the range isn't helpful. Full sized rifle rounds are rather heavy, a .308 cartridge weighs 24.2 grams and a .30-06 cartridge weighs 26.8, that means a solider carrying 5 kg of ammo can carry 206 and 186 rounds respectively. Intermediate cartridges were pioneered with the 7.92x33 used in the StG44 and continue today with the 5.56x45 and 7.62x39. They're not great at super long ranges, they're not obscenely powerful, but they're good enough and light. A 5.56x45 round weighs 11.6 grams meaning that 5 kg of ammunition now lets you carry 431 rounds, more than twice as much as the full sized rifle rounds. That buys you a lot more time of suppressing fire or the same amount of time but significantly more mobility. Really big rounds like .50 BMG are extremely heavy and have ludicrous recoil making them poorly suited for anything that isn't a bipod mounted sniper rifle or a crew served machine gun, but it'll take out a car. Rifle rounds have smaller bullets than pistol rounds, but significantly longer cartridges with way more gun powder. A .50 BMG round is 6x longer than a .45 ACP round, that's a hell of a lot more gunpowder pushing the bullet down the barrel getting it up to much much higher speeds.",
"There are 3 big things to look for when looking at bullet effectiveness. Mass of the projectile(correlates to caliber), Speed of the projectile, And the composition of the projectile. Bigger projectile means more mass which means more force when it actually hits something. It also means its harder to get that round up to speed meaning bigger rounds need a bigger powder load to truly be effective. Next is speed. The faster a bullet goes the harder its gonna hit, and the this depends on how much gunpowder you are putting behind a round. This means that you can have two rounds with the same caliber having different powder loads and vastly different power output. [To help visualize this]( URL_0 ) these are some rounds. The round on the far right is 50 bmg, while the one labled 50AE is 50 action express aka the biggest round a Deagle can chamber. Both are technically 50 caliber rounds but obviously 50bmg is gonna have a fair bit more power behind it. Finally there is the actual composition of the projectile which while less impactful than the other two does change how the bullet behaves on penetration. Harder bullets penetrate harder surfaces better, while softer rounds will tend to mushroom and tumble when they hit a hard object. This tumbling is actually a feature and can drastically increase the damage a round will do to a soft target. Side note .22lr is small, but it does work if you let it. There was even a fully automatic gun similar to a tommy gun adopted by U.S police that shot .22lr. The idea was that it wouldn't penetrate walls or shoot through people, but you could absolutely still chew through whatever was in front of it.",
"The difference between .45 and 5.7mm is the velocity of the bullets after they leave the muzzle. .45 was designed in the early 1900s after US Army testing indicated that, when using solid metal jacketed bullets, small fast pistol cartridges tend to punch through the body and leave a small hole while heavy but slow rounds will stop inside the body and dump all their energy into the target's internal organs. It wasn't much of a concern that rife cartridges of the day (all around 30 caliber) would penetrate the body because they were so fast and powerful that even a fraction of their energy could incapacitate an enemy, but for pistol cartridges that had to be fired from the hand having some of the energy be \"wasted\" due to over penetration was seen as a problem. 5.7mm is a much newer cartridge, and was designed to be small and fast to allow police and military personnel to have a bullet that could be fired from a handgun and still penetrate body armor. To compensate for the possibility of punching through people, the designers took advantage of more modern bullet construction techniques which cause the projectile to either expand or tumble inside the body, causing them to dump all of their energy despite being very fast. Despite all of the above, both .45 and 5.7mm are both much less common pistol cartridges than 9mm, which strikes a much better balance than either at being small and fast enough to fit a large number of rounds in a magazine, while also being slow enough to reliably stop inside the target. & #x200B; TLDR; 5.7mm is really fast to beat Kevlar, but expensive and not as good at stopping unarmored threats. 45 ACP is a very old design and not good at fitting in a gun's magazine. 9mm Parabellum strikes a balance, and that's why everyone uses it. & #x200B; Really fast edit: Someone thought the Desert Eagle was necessary because people are willing to buy guns that shoot ridiculous bullets, and wherever there is a demand there is money to be made as the supply.",
"Many factors such as length and weight (caliber is just diameter), powder load, abd jacket. Compare a .223 and a .22lr. A .223 goes in an M16, and despite being only .003 larger in diamter is more than twice as long. The shell casing for a .223 alone is larger than a .22lr. Heavier bullet and more powder."
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a5do6l | what is (video) rendering, why is it necessary, and why does it take such an enormous amount of time? | Technology | explainlikeimfive | {
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"hmmm... I guess a very simple way of saying this is that the computer is ‘drawing’ all the things in each frame of the video.",
"These descriptions are correct. Adding to this if your video has 3D elements or it is totaly 3D (like toy story) the computer has to spend lots of time calculating things like lights/colour/reflections etc. This kind of resource heavy computing is often done by large \"render farms\" which can be dozens and dozens of systems all working together to render a different frame or different parts of frames. When i rendered some of my work for my final projects in college, some of my renders took 60+ hours on 10 or so computers. And that is just small scale work. Big motion pictures can take hundreds of thousands of combined hours to process."
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a5f524 | Why, as a normal civilian, should I be worried about data leaks? | Asking more out of interest to learn, it seems like such a bad thing for companies to have your data, but what's the actual harm in this? | Technology | explainlikeimfive | {
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"If they have your email and password, and you use the same password for your email (which many people do), they can effectively take control of your online presence (sending password resets for things). A little digging in your personal emails and they could probably get the answer to a few of your security questions (or ask people close to you while posing as you). At that point they have access to your online banking. So keep a diverse set of passwords and you are fine, but most people don’t.",
"As a normal person your primary concerns would be fraud and identity theft committed against you and the damage to society done as a whole. The first part is easy. If someone has your details they cans teal from you. It might be something simple as finding out what email and password you use on one website and then using it on another website where they then take over your account and do things with it that damage you. Or it might be that they gain enough of your data to open up accounts in your name and incur debts that you have to prove aren't your later. Or they might simply steal your credit card number and do shit with that. Less obvious are things when the data that gets in the wrong hands is not really used to directly hurt you financially. The bad guys might simply amass a list of thousands or millions of people who according to their data fit their profile and target them with political advertising in ways that drive them to ever more radical opinions since only the people who are inclined to believe it get targeted. Before you know it you have a large number of victims who live in a parallel world where everyone agrees that the moon is made of cheese and they vote accordingly. That can really hurt society as a whole."
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a5fm3i | What are the random characters you see when you open an MP3 file in Notepad? | Technology | explainlikeimfive | {
"a_id": [
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"The way notepad process the 1s and 0s is different from the way a mp3 player processes those ines and 0s so the notepad sees rick astleys never gonna give you up as a series of random letters and numbers",
"All files are 0's and 1's on your computer. The question is, how to interpret those 0's and 1's. Text files assume you have each byte(set of 8 consecutive bits) represent a character(or in case of unicode, it may be several bytes. In that case, the first byte tells that). So notepad uses this to just turn each byte into a character. But actually in music file, the bits tell sound frequencies and volumes(usually. Mp3 files are more complicated than that). So this idea of turning them into characters makes no sense. And so, opening them with text editor just results in essentially random characters. The reason it's not just numbers and letters is that text encoding(encoding is the rule that tells you which numbers correspond to which letters) have bunch of extra control characters. Each byte can have 256 different values, but usual letters and number symbols only amount to maybe 70. Others are used in less standardized ways, but for example, some correspond to line breaks, some correspond to adding accent symbols to previous letter, etc. There actually are multiple encodings, and Unicode actually is capable of describing all symbols in the world(but characters may require more than 1 byte), and to do it it includes complex system of modifying letters. So when you input essentially random numbers, you get just random samples of the things the encoding notepad decides to use can represent. And it's a lot. And many of them are weird."
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a5fo2i | When people used to rely more heavily on well systems, how did they keep that water from being stagnant and unhealthy to drink? | Technology | explainlikeimfive | {
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"Stagnant results from when it has decaying organic matter in it, or some other pollutant. As long as a well is kept covered, there isn't much that can get in there. If they really thought it had a problem they could just remove all the water in the well, and more new, fresh, cleaner water would refill it.",
"Water becomes unsafe to drink after people use it for bathing (fecal matter and other bodily fluids that transfer disease get mixed in) or you do something gross like drop a carcass in it. People have known not to bathe in their drinking water for a long time (the Inca, for example, had it figured out - they were very smart with how to keep water clean and how to manage stormwater). General pollutants to the water supply don’t help. Wells just pull groundwater from aquifers. Groundwater is becoming more polluted now via agricultural pollutants (fertilizers), urban runoff (all the shit that gets washed out of cities and into the watershed during stormwater events), and industrial pollutants. When people were more reliant on wells than treated water, these pollutants weren’t as numerous.",
"Some ancient cultures used a system to keep water moving, i.e aqueducts, man made rivers, or carved spirals that circulated cool air across the water to keep it chilled which prevented some contaminants. Back then water and springs were less risky. Thev did boil the water to clean it. diphtheria and other water born illnesses were prevalent back then though.",
"For water to be stagnant it has to have microbial growth and decaying matter in it. This happens on the surface due to sunlight and things falling in it. Water that is at groundwater level has seeped slowly through the dirt and gravel which means it has been filtered to an extent. While it is possible for pollutants to get into ground water, in general that filtration makes it safe to drink and you only have to worry about keeping stuff from falling into the well."
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a5g1ga | How to you build/compile from github? | How do you build/compile from something like this URL_0 I never understood this Is it simple or difficult? Any step by step tutorial? | Technology | explainlikeimfive | {
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"there is nothing to compile, the above is bunch of javascript front and backend. Just look at URL_1 for instructions, follow them. once you set it up and startup the web server, you’ll just point your browser to it like so URL_0",
"Depending on the programming language, the steps to build or compile a program are slightly different, but in the general sense, most programs have a list of actions to take in order to build an executable file that can be distributed or just for use in the computer that built the program. Unsurprisingly this file is often referred as \"build file\" and depending the programming language it may be named differently. Some programming languages don't even need a build file and can generate an executable on the fly. In order to run this build file, your computer requires to have some special tools and libraries, for the simplest of programs a compiler is often enough, but for anything more complicated you need more stuff to be installed in your computer in order to build a program, this varies wildly program to program. To answer your question, building or compiling a program is as complicated as the program author makes it. Most good software has explicit instructions on how to build the program and it's dependencies. A good example of such program is: URL_0 try following the example to compile it, I'm sure you'll be able to do so with a bit of digging provided you have the development tools installed in your machine."
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a5hkh7 | Why are servers where they are | On every game that I play, the servers are always in one location for that region (German servers for EU, Singaporean servers for South Asia, Japan servers for East Asia). Why are these servers not placed at other countries? | Technology | explainlikeimfive | {
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"It costs more to have multiple server sites. You need a building and personnel to service them, or hire arrangements with more providers for space on theirs. On the other hand, distance usually results in increased delay times for a single location. So they balance cost against performance.",
"Probaly due a mix of good legal regulations on that country plus good Internet infrastructure. Also, geographical situation is a variable to keep in mind. Afrer somebody did his job and decided the best place possible to keep the videogame's server, make sense that other professionals looking to offer very similar services to reach the same conclusion.",
"There are several things determining where you want to place your servers. Main things are costs (including taxes), existing infrastructure and latency. For a game server latency is quite important and the speed of light is a big factor. So you want to place the servers in the center of the customers. So for example Ireland, Spain or Russia would make for a bad place for game servers to server Europe. Germany does have lots of big datacenters already with lots of infrastructure in place. So this makes for an obvious choice of server placement. Singapore is similarly placed centrally between China, India and Australia and therefore have low latency to these countries. And their taxes are lower which attracts businesses that helps build the infrastructure. The servers in Japan or Korea is mainly there to serve the massive amounts of gamers in these countries. And there are similar choices being done when choosing which city to place them in."
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a5jhca | What is the difference between a video and a gif? | Technology | explainlikeimfive | {
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"text": [
"A video will use more frames per second making it much more fluid. Videos also usually have audio files to accompany the video, gifs are more like a looping slideshow",
"The biggest difference is compression - gifs compress each image individually. Video compression looks at the difference between consecutive frames - if you're watching a movie, in any scene, very little changes from frame to frame (the background remains constant, some of the characters stay in the same place), which has less information and is therefore able to compress much smaller."
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a5mya2 | How do websites like the Wayback Machine work? They can't possibly visit every obscure website in existence to take frequent snapshots, right? | Technology | explainlikeimfive | {
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"text": [
"That's pretty much exactly what they do. URL_1 They use something called a [web crawler]( URL_0 ), which is basically a bot that visits every publically accessible website that it can find. They store millions of gigabytes of data."
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a5nfon | What makes a device "safe to remove"? | If I don't click to "Safely remove ...", what could be the worst-case scenario? Does Windows or OSx make a difference? | Technology | explainlikeimfive | {
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"text": [
"So let's say you're writing in a book. If I let you finish what you're writing and update the table of contents, it's all good. The book can be 'safely removed' from your desk. But, if I just pull the book away, you might still be writing. Now it's unfinished, and the last bit won't make any sense. It's similar in a USB drive. Safely removing it means the computer has stopped working on it, both reading and writing. If you pull it out during an operation, you could just lose the data, or break the drive entirely.",
"It makes sure its no longer writing or reading anything to that device. There is a potential that data could be unfinished or get corrupted if you remove a device while its transferring or processing data. \"safe to remove\" is a bit overkill, but it just ensures that, yes, its all good, you can remove it without causing any data issues.",
"Saving information on the device sometimes doesn't happen immediately. Windows and macOS might sometimes store up information that needs to be written to a device for a short time (say, for example, when multiple programs are reading/writing from it, or when the system is lagging) and writes it out to the device as soon as possible. It's called buffering, and most modern OS reads and writes are buffered reads and writes. You could theoretically unplug before the buffer has been written out to the device. When \"ejecting\" a device, the OS flushes the memory buffers of stuff that needs to be written and forces it all out to disk."
],
"score": [
31,
3,
3
],
"text_urls": [
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} | [
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