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e2fdur | what is an API (application programming interface) | A nice analogy will really help. | Technology | explainlikeimfive | {
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"Its an agreed upon standard to transmit data. (or it could be used to request an action) Lets say you go to a doctor. He wants information about you, so you go to his website, and download a new patient form. You then fill it out. You are giving him the exact information he wants, in a form that he understands. This is kind of the human equivalent of an API. With an API, you are transmitting the exact information the site wants, in a format it expects. Lets say you also have a new dentist, and you bring your new patient form from your dentist to your doctor. Your doctor would say 'this is the wrong form, can you please retry. An API might say Error code 400, which your end of the API knows this means 'bad request'",
"Think of it like a set of tools you can use to achieve a task without needing to know precisely how those tools are built. You don't need to know precisely how to build a hammer and a paintbrush, or where to buy the building supplies; you just call getHammer(), then useHammer($onObject), then getPaintSupplies(), then paintObject($chosenObject), and finally you get your constructed and painted object. It's up to the people who create the API to know how to make each of the commands work. To take a real world example, PayPal offers an API. If you understand how it works, then you can create your own website code or plugin to create PayPal orders and payments by contacting the PayPal API and providing the right information in the right structures. PayPal takes that information in the correct format and does their own magic upon it, turning your code (your API request) into actual payments."
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e2fvdf | How to barcode scanners instantly detect what an item is, despite the barcode being at any angle and often on a crinkled surface, completeley changing the look of the code from the scanner's perspective? | Technology | explainlikeimfive | {
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"The lasers that read the barcode hit it from many angles and scan it very quickly. Also barcodes have something like a checksum, where it's easy to recognize if the data that was read is garbage and needs to be read again. That's why when using hand scanners, like at the grocery store, sometimes it scans a valid item very quickly, and somtimes it takes a while. The built-in scanners in the checkout lanes have lasers that shot from the sides and from the bottom.",
"It depends on the scanner for many of those to be true. A very simple barcode scanner will simply read one direction (allowing some but not much tilt) while others will use various techniques to account for these challenges. In most cases, a beam of light is fired at a thin foil that is extremely sensitive to current change, allowing a rapid low current to be pulsed in to control the angle of the beam. Some, such as grocery store checkout lanes, supply multiple beams and reflectors allowing any angle to be scanned. The reflection of the beam is sent back to the scanner when a reflection is possible, toggling an internal state between 1 and 0. During this, either the duty cycle - the time between “reads” of that 0/1 state, is constantly slowed and sped up, or the pulse rate to the reflectors is variated, changing the sampling rate very rapidly. This allows for distance to be much less of an issue. Basically, there’s always a beam of light and the hardware is asking repeatedly “Do you see the emitted IR light?” That data is pushed into a cyclical buffer, and each read triggers a checksum calculation. Since the length of the code(s) are known, it allows the assertion “If these are the numbers, their sum should calculate to the check digit.” - if the checksum for example is just a basic digital root, and the numbers read as 6,4,8,3,7, then 6+4+8+3+7=28, 2+8=10, 1+0=1, so the check digit must be a 1. To detect the start and end of a barcode, a specific character is often used - since were dealing with binary, it’s often a non-numeral character such as * or a,b,c - this extra data not only serves the purpose of telling a scanner where a start of a barcode is so it knows it can use more processing power to actually read the code, but the kind of code it is so it knows what checksum formula to use and how long to expect the barcode. These little details allow them to be extremely fast as it’s quick to tell, “If my buffer doesn’t start with *, it’s not a barcode, keep reading” You can act see the effects of that on much older scanners, they’ll start flickering at a certain rate, quickly ramp up and down, then shut off when it hits that known character, often pausing for 1-2 seconds before the register receives a barcode. tl;dr, you can take a piece of paper and put a series of dots in a Braille fashion, 1 dot for one, 2 for off. Start a metronome and “read” whatever is under your finger, even if it’s the same dots or 3 dots apart, moving your finger at a constant rate, counting on/off, and grouping every 4 dots. Convert from binary to numbers. Repeat adjusting the metronome up or down until your finger hits each dot once per tick. That’s all it’s doing just using light. (I don’t expect you to actually do that but if you do - props - it also illustrates how much faster computers are at “thinking” than we are."
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e2gxmv | how are we able to see planets that are 100’s of lightyears away? By continually increasing the magnification of a telescope? How do we know anything about the planets atmosphere if it’s that far away? For example, the Corot-7b, we are told it rains rocks there. | Technology | explainlikeimfive | {
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"We’re not able to see them. We see them block the light from their star. Or we see their gravity tugging on their star. We know about their atmosphere because when they block that star, some light pass through the atmosphere, which filters out some light but not others.",
"We don't actually see them. When the plant passes in front of its star, it blocks some of the sunlight. We see the sunlight dim in a very predictable way. By doing some calculation we can figure out the size of the planet and how far it is from its star. We can tell the chemistry of the atmosphere by looking at the light. By using a prism, we can tell what the Star is made of. And then, when the planet first starts to pass in front of the star some of this light passes through its atmosphere. By using a prism and comparing the changes in the light we can tell what the planets atmosphere is made of. Imagine looking at a flashlight at night, and then looking at it when there is smoke in front of it. It changes right?",
"A Prism is how we can see what something is made of Simply put, you shine light through a prism and it reveals a spectrum of light waves. Based on the wave, you can determine the element present ELI5 version: You send 118 people into a muddy room, all with different shoes. No matter how far the muddy room is from you, you can tell who has been in the room because evereyone has different shoes, and there are different shoeprints in the room.",
"The most common method is by watching the host star's output for telltale signs of variation in it's brightness and position. A star that wobbles a small fraction tells you that there is some other body's gravity acting on it. This is done by watching a star's spectral lines as they change because a star and it's planet(s) will orbit a common center of mass. A star that moves away from you will have it's spectral lines shift red, and then blue as it comes toward you. Additionally if a star dims a small fraction on a periodic basis, then that means an orbital body has moved across it from our perspective. The size and mass of a star is determined first by watching binary stars. If you determine the size of their orbits around each other and the period (speed) of their orbits, then you can calculate their respective mass as well. Once you know the mass of a pair of binary stars you can apply that knowledge to similar stars not in binary systems. (And the more binary systems you study, the larger the range of single stars you can size) Once you know the size of the individual star, you can calculate the mass of the orbital body and it's orbit by the parents star wobble and changes in luminosity. What the planet is made up of can be seen in general terms from watching the transmission spectrum coming from the system, and the spectral lines will tell you what materials are present."
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e2h91x | Why are there multiple types of command line interfaces in windows rather than just one? Command prompt, Powershell etc. | Technology | explainlikeimfive | {
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"Powershell is the NEW command prompt. Cmd really only lets you run - from a dos prompt - the applications in your path (environment variable) or in the local folder which you normally could run by finding the executable in Windows Explorer. You can \"script\" cmd by using batch files, but DOS/Windows .bat file syntax essentially is just what you could type line by line in a cmd window, nothing more. In order to interact with files, system parameters, registry values or running applications you'd have to write a cmd executable program to do so. Powershell on the other hand does everything cmd does, but includes support for plugins and scripting - if you like, its very similar to a UNIX/Linux style \"shell\" - it can launch programs, interact with running programs, can be scripted and provides APIs to maniupulate files, parse file contents etc. if you ever find yourself cursing while you attempt to troubleshoot a complex .bat file, seriously look into Powershell scripting. So much nicer.",
"There's just those two. Command Prompt is the old interface. It's a lot simpler than Powershell so it's easier to work with if you're only doing basic things. It also still exists for backwards compatibility. Powershell is much more powerful, but much more complicated."
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e2ir0h | How do aimbots work? | I've seen people get banned from Twitch and other streaming sights for using aimbots in games like fortnite (bleh) and apex and other games; but I'm not entirely sure how they work and how the player activates it, i guess? | Technology | explainlikeimfive | {
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"The bot responds to the \"pull trigger\" key by twitching the weapon's aimpoint onto the nearest target first. The user kits a key and the game sees a mouse move and key sequence that produces a better score. You have to be pretty close and \"target-ness\" needs to be well defined, so it's hardly a perfect thing. However, it's clearly cheating.",
"1. Aimbots read the game memory somehow(hooking into the game or another software process and reading the game memory from it, or reading it directly by using kernel drivers, ...) 2. Certain memory offsets are read to get coordinates of enemy players. (the offsets change everytime the game gets updated) 3. 2-argument arctangent is used to calculate the necessary angle to aim at the nearest player. Cheaters bind this feature to a mouse button or key and press when needed."
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e2m750 | Why do many laptops have 2 GPUs if you're gonna use the best not integrated? | Technology | explainlikeimfive | {
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"The more powerful the GPU, the more power it takes. Using a less powerful GPU for more everyday tasks, it prolongs the battery life.",
"A separate GPU in computer systems is considered an add-on for a small segment of users. The design of computers is generally built to support all users, not just this gamer segment. Most CPUs have a built in gpu in today’s market. These are designed to be put in a variety of systems with ease and always work. As such if you’re a user that wants to “add on” a gpu you can without issue and if you’re not, then everything works fine. Separate gpus are better, but mire niche and more expensive. So it’s only generally offered as an add on."
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e2obl0 | why does the video mode on my smartphone camera zoom in compared to the photos mode (single lens camera) | Technology | explainlikeimfive | {
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"It could be because of video stabilisation. It will crop a certain amount of the outer pixels of each frame in order to keep the video looking straight",
"camera sensors are made up of lots and lots of little light-collecting buckets called pixels. the total number of pixels in a sensor is usually in the millions, and we refer to those quantities as megapixels (mega- means “million”). digital still images can be made up of any number of pixels, but videos have a more restrictive and specific set of rules. a “full HD” video, for example, must be exactly 1920 pixels wide by 1080 pixels high. if you multiply 1920 by 1080, you get just a little bit over two million. your camera’s sensor is larger than 2 megapixels for a lot of reasons, but they all add up to “because more than 2 megapixels looks better.” when you shoot an HD video, however, there’s no reason to use the whole sensor since HD video only needs a 2 megapixel image. so, when you flip to video mode, the camera just uses the middle of the sensor, and ignores all the pixels around the edges. the lens doesn’t change, though, so light coming into the camera is still covering the whole sensor. when you clip out the middle of the whole image into a 2 megapixel size rectangle, and throw away the edges, that has the effect of zooming in, since you’re seeing a smaller “window into the world” than if you included all the edges."
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e2qjrq | Can someone explain what people mean by “ticks” when they talk about computers? | Technology | explainlikeimfive | {
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"It's often a simulation term. Is you have a game or a simulation, processing can't be continuous, but update rates are variable to maximize response speed. The generic term for the time between frames is a tick. The tick size may need to vary, to maintain real time execution, but this way none of the other code has to change."
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e2qq4r | How does a rotating tree stand work?! | I just can’t wrap my head around it. I need answers! | Technology | explainlikeimfive | {
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"Imagine a normal outlet + plug. A pair of metal rods/ plates transfers electricity by being in contact with another pair of metal plates. Now make each plate a large ring instead, so they’re two circles with the same center point. Now they can rotate against each other without losing contact. That’s how a rotating tree transfers power from the base to the tree."
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e2sjw5 | How do magnetics remove tape footage? | Technology | explainlikeimfive | {
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"Imagine pencils arranged in a certain way to say something- like a big letter A. That letter A represents the data on the tape. When you run a magnet over the tape, its like swiping your hand through that letter A of pencils. The pencils go every which way, and you won't know what it was by looking at it.",
"Information on digital tape is stored magnetically -- that is, each direction the magnetic regions can point is either a one or a zero. Exposing the tape to a strong magnet scrambles these domains, erasing the data."
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e2srro | How does a government shut down the internet for an entire country? What are the steps involved in shutting down the connection? | Technology | explainlikeimfive | {
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"Every country has only a relative handful of places where they connect their network to the rest of the world (forming the internet). For most countries, these connection points are along the coast, where fiberoptic cables (armored glass tubes) come together in large facilities for distribution throughout the country. Other countries that are landlocked have similar facilities, though I'm not sure whether they're located on the border or elsewhere. In either case, to block outside information they simply stop those signals at those facilities and prevent them from moving throughout the country (this is like what Russia is trying to do). If they want to shut down the internet within the country (such as Iran), so that people can't even communicate domestically, they turn off the internal facilities as well. What you term \"the internet\" is just information being sent through a bunch of hubs. Because it's so expensive to build, those hubs are relatively few and far between. You shut down the hubs, and nobody can send information. It's not all that different than asking \"how do you shut down the power for an entire country.\" Only there are fewer facilities providing internet than there are power stations. Edit: This is a map of the underwater fiberoptic cables mentioned in the first two sentences. URL_0"
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e2t26s | "RIPE NCC has run out of IPv4 Addresses", what does it mean, is it serious and what do we do now? | Technology | explainlikeimfive | {
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"The \"old\" system is IPV4 and it has long been known that the numbers would run out at some time. The industry has adopted the new IPV6 standard 20 years ago. They work in parallel although they don't interoperate very well. The new IPV6 has a lot more numbers than IPV4 and isn't expected to run out any time soon.",
"TLDR: The system used by the internet to define addresses ran out of space, but it's ok because we're already using a new system. Imagine a city that has reached a theoretical maximum size. All of the space within the city limits is allocated, and all the possible roads are built and named, but there's still tons of empty lots to build houses. But if you go to the city to ask for a plot of land they'll tell you there's none left, you have to buy it from a developer that bought the land years ago and has just been sitting on it. RIPE is the organization responsible for issuing blocks of IP addresses to organizations and ISPs in the EU. The equivalent in North America is ARIN. RIPE running out of IP blocks means there are now no new blocks available in North America or Europe (ARIN ran out years ago). ARIN+RIPE running out of IP blocks though doesn't mean that there aren't any available. It just means that they've run out of new blocks (think streets) to issue to organizations that want them. But there are still millions of addresses out there available to be used, most of them owned by ISPs and big companies. IPv4 (Internet protocol version 4) is the protocol used to define the addresses usable on the internet. IPv4 supports 2^32 or 4,294,967,296 possible addresses. But because of a combination of the internet growing faster than anyone anticipated, a massive amount of waste, and a spectacular lack of forward thinking we've run out of addresses. For example at one point they decided that every address starting with 127.x.x.x would represent 'home' or a loopback, a very important thing in networking, but this effectively wasted 2^24 or 16,777,216 IP addresses. Back in the day ARIN handed out blocks of IPs like candy so organizations like HP, the US govt, and Apple that got in early were assigned an obscene number of IPs that they now sit on and basically refuse to share. Meanwhile the ISPs use up IPs for subscribers and businesses faster than we can count while the internet continues to grow. But all this doesn't really affect the average Joe. The average user or business doesn't get it's IPs from RIPE or ARIN, because you are too small scale for them to care. Smaller organizations get their IPs leased to them from an ISP. When you plug in your modem at home you get an IP that is assigned to you from your ISP, which in turn got the right to use those IPs from RIPE or ARIN. So what's the fix? Technologies like NAT were developed in the 90's to kick the problem down the curb and bought the internet decades to come up with a long term fix. This fix is Internet Protocol version 6 or IPv6. IPv6 is a complete new method of addressing for the internet and supports 2^128 IP addresses (340,282,366,920,938,463,463,374,607,431,768,211,456, which is approximately 340 undecillion, or 340 billion billion billion billion, addresses). IPv6 has been in use for decades, but implementation has been slow. v4 and v6 run in parallel but they aren't compatible (v4 addresses can't talk directly to v6 addresses) which causes some interesting problems. Business and ISPs have to upgrade their equipment to IPv6 which costs time and money, and many organizations just don't see the point of making the change when there is no real tangible benefit to doing so for the immediate future. v6 however is growing in use, particularly in the mobile market. Your cellphone probably uses an IPv6 address and you aren't even aware of it. In time v6 will take over the entire internet, but whether that will be in 10 years or 50 is still up in the air and depends on getting people to actually switch over... which is kinda like pulling teeth."
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e2u559 | What does it mean that Europe has run out of IP addresses? | URL_0 Why can't they just generate more numbers? Is there a fixed number of physical ports or something? | Technology | explainlikeimfive | {
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"> Is there a fixed number of physical ports or something? Not physical, logical. IPv4 uses 32 bit addresses. This means that only a total of 2^32 (approximately 4.2 billion) IP addresses can ever exist. Each ISP gets a subset of these addresses (known as as subnet), so it is limited to the addresses in that subnet. RIPE is the organization that hands out subnets to ISP in Europe.",
"IPv4 addresses can go from 0.0.0.0 to 255.255.255.255. That's 2^(32) addresses. Certain addresses are reserved, private, or public. Public ones got allocated to the various Internet governing bodies across the planet which would then lease their use. The governing body for Europe is fresh out of IPv4 leases Thankfully there's IPv6, the improved Internet Protocol. It has a far larger address space (2^(128), which is more addresses than atoms that make up the planet), as well as more security overall"
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e2u8l5 | How does the ‘perfect motion rate’ setting on my TV make even movies shot at 24fps appear to be at least 120 | Technology | explainlikeimfive | {
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"If you've ever read the [Animorphs book series]( URL_0 ), you'll notice the covers always depict a human \"morphing\" into an animal through multiple still frames. The human and animal are quite real because they occur in nature but all the intermediate steps must have been filled in based on the artist's imagination. The \"perfect motion rate\" and other motion interpolation settings in TVs do the same thing. They take two known frames at 24 fps and \"fill in\" the gaps to make it appear as though it is 60 or 120 fps much like the intermediate steps in the Animorph covers. This means it can create a blending of those two images that didn't exist in the original content. This makes the motion look \"smoother\" because there are more frames. However, this can also cause the content to appear different from what it was intended to be displayed or even introduce issues not present in the original content. It's called \"soap opera effect\" because it resembles the higher frame rate used when shooting soap operas.",
"Short answer, the TV uses software to take half of the current frame and half of the next frame, and creates a frame between the two."
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e2ut6p | how does solar panels work, and how do they generate power? | Technology | explainlikeimfive | {
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"When a light particle lands on the solar panel, it lands on an atom. The energy of the photon (light particle) is just enough to knock an electron out of the atom. The electron is then free to flow over the atoms in the solar panel, creating a current. This creates electricity.",
"Light knocks the electrons off of one terminal and onto the other. These electrons want to return to the first terminal, and we can harness this 'want' or energy to power things.",
"A solar panel is a semiconductor diode. So electricity only flows one way and not the other. When a photon hits an atom in the solar cell it transfers all its energy to one of the electrons. This electron will shoot out of the atom in a random direction. Normally it would bounce around the other atoms losing energy through heat and then finally get realed back by the atom due to the different charges. However is the entire solar cell is a diode the electron will not be able to return if it moves in the normal direction of current through the diode. This leaves too many electrons on one side of the diode then the other. By connecting the two sides of the solar cells together with wires we gives the electrons a path back, and putting electrical appliances in the path of the electrons allows us to harness the energy from the current of electrons.",
"I don't know how they work, but since we live off-grid and depend 100% on our solar panels for power, I'll give you my take. Inside our house, in two long boxes are 8 huge batteries. They're bigger than a car battery. Batteries need to be kept indoors from freezing. Regular maintenance requires us to to \"top off\" battery levels every month with distilled water. A line runs from the battery underground to our panels, We have 8 panels. As it is winter, our panels are tilted nearly vertical as the sun is only hitting the panels for a few hours per day. During the summer, the panels lay nearly flat when we get sun for 12-14 hours a day. As we haven't seen the sun in over a week, we need to run a generator that charges the batteries, We're having to do this every second day, In summer we'll generate about 6Kwh per day, but currently generating about 0.1kwh. We use about 3kwh a day. Far cry from when we lived in the city, averaging 35kwh per day."
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e2va8o | What is it about certain notes of music that induce a feeling of either sadness or happiness? | Technology | explainlikeimfive | {
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"Which notes or scales you find happy/sad is cultural. For instance a \"happy\" sounding scale to one culture is literally burial music in another.",
"Music mimics human speech and heartbeat. If you say something in a sad tone you hit those exact sad notes a d if you say it upbeat you say it in happy notes. So listening to a sad song evokes the same feelings as listening to a person wailing and crying"
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e2vcrg | How does the radio app on a smart phone use wired headphones as an antenna to tune into radio stations? | Pretty much the title. On Samsung smart phones, for example, there is a radio app but in order to tune into the radio you have to plug in your wired headphones which acts as an antenna and lets you tune into the local radio stations. How does that work? | Technology | explainlikeimfive | {
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"The optimal size of the antenna for receiving radio signals relates to the wavelength of the signal. For cellular traffic the cell phones use frequencies over 700MHz which have a wavelength of about 10cm which allows it to be received perfectly by an antenna of about 5cm length that can easily fit inside the phone. However for FM radio at 100MHz the wavelength is 3m. The phone can use your body as a counterpoise to act as half the antenna (this is why you often get better radio reception if you hold your phone) but still needs a 75cm long antenna, or about the standard length of a headphone cable. The issue with this is that there is already a signal on the cable, the audio signal. The good news is that this signal is all bellow 20kHz while the FM radio signal is all over 80MHz. This gives you three and a half orders of magnitude frequency difference. So you can use a frequency splitter which splits the audio signal from the audio amplifier and the radio signal to the built inn radio. As there is so big difference in frequency you can use a very crude frequency splitter of just a couple of components. Even if you do not have an FM radio in the phone you still want this frequency splitter to prevent radio signals to get to the audio amplifier and interfere with the audio signal."
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e2x004 | How do compressed files work? | Technology | explainlikeimfive | {
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"Say you have the following string: AABAAAAAABAAAABAAAAABABABAAAA You can compress it to A2BA6BA4BA5BABABA4 (A2 means AA, A4 means AAAA etc) This is lossless compression as it can be restored fully. It is also just one of many, many ways compression can be done."
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e2z33n | What does RAM in a computer do ... | Technology | explainlikeimfive | {
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"Think of a computer like an office in the 60's trying to get things done. The CPU (central processing unit) is like the person sitting at the desk. The faster, more motivated, and more experienced the person is, the more work they can get done in a day - this is why some CPU's are better/faster/stronger (and more expensive) than others. The HDD (hard disk drive) is like a filing cabinet full of important paperwork which needs to be kept and referenced. This is where all the files actually live. It is reliable, cannot be easily disrupted by the janitor at night, but it takes time to get things out of it or to put them away correctly. It is also vulnerable to an error scrambling it up making files difficult to find. Now, RAM (random access memory) is like the desk itself. This is where paperwork and files sit to be referenced and worked on quickly by the CPU. A bigger desk means more room for more paperwork (while keeping it organized and efficent) the same way more RAM gives the computer more \"stuff\" it can consider quickly (without having to mess with the filing cabinet). The difficulty with RAM is that it has limited space compared to the HDD and it is volatile - the janitor is a real clean freak so any papers left on the desk at night, or on lunch, or any other time the desk is not in use will be collected by the cleaning staff and shredded. We could really torture this analogy further but comparing office layout to mainboard architecture, adding a bookshelf to sub in for the HDD cache, maybe compare the type of door to I/O formats (you know,double doors for lightning ports but a doggy door for UBB 1.0 and a mail tube for RS-232...). I should stop now. Hope this helps.",
"In laymans terms, the part of your computer that does the processing is the CPU. It is what CPU means after all - Central Processing Unit. So you send instructions to the cpu - like \"Add 1 to address 17\", and it executes them. It executes them very fast, and a lot of them. Any time CPU isn't executing something, it wastes its time - so our hardware is designed to avoid that (its called Stalling). So what happens is that CPU gets a queue of orders, that it processes one at a time. But that queue needs to be stored somewhere - that's what RAM does. RAM is a very, very fast memory (meaning the speed at which you write and read from it), meaning it can send and receive data to CPU without being bottlenecked. RAM is also used to load data in advance - for example, say you are playing a game. Game developer sees that you have rotated to look left. There is a good chance that you will rotate even more left, so game loads the textures etc from that direction in preparation. Also any kind of data that might need to be accessed FAST is stored in ram. Say you copy an image. That image is stored in RAM - because you want to be able to call it back (paste) it at will. The downside of ram is that it's volatile. Volatile means that it requires power to work - and once powered down, it wipes all memory. So as soon as you turn off your PC, your RAM is cleared. Any data stored there is gone. That's why we still use other types of storage, like HDDs or SSDs, even though they arent as fast as RAM - they are non-volatile, meaning they preserve data even when not powered.",
"Ive always used the kitchen analogy. Think of your pc as a kitchen. You are the cpu, the fridge is the hard drive and the ram is your counter space. You (cpu) places ingredients (program) on the counter (ram) and can work with them from there. The bigger your counter space, the more ingredients you can work with. If you run out of counter space then you'll have to put something back into the fridge and take out the new ingredient which takes a lot of time. So ram is basically the fast access area where the CPU can work with instructions but if you run out of it, the the CPU will have to access from the hard drive which takes a ton of time compared to ram.",
"It's a memory that is used to store what your computer is generally working with at the moment. It can't store data when the computer is turned off, but when it is turned on your computer uses the RAM to store all the stuff it's going to need for the programs currently running so it doesn't have to use the hard drive for every little thing. If we imagine the computer as an office, and the CPU as the office worker, then the general types of memory are: * Hard-drive (HDD, SSD) can be thought of as the library next to the office. It has a lot of storage capacity, but it takes a long time to get the books you need. * RAM can then be thought of as the file cabinet next to your desk. It's easy to reach and so you store the books and files you're working with often there. It takes a bit of time to open the correct drawer and space is a bit more limited than the library, but it's great to store the books you'll need today instead of getting up and going to the library every time you need to switch books. * Cache is then the desk in front of you. It has little to no room on it, but it stores the files you're working with *right now*, and need to be able to get instantly."
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e31kcz | Rainbow Tables | Technology | explainlikeimfive | {
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"When you log into a website you have to tell them a password. It's important that they know if you gave them the right password, but they don't actually need to know what the password is. In fact, since someone could come along and steal their files they really ought to *not* be able to figure out what the password is using just the information they have stored. To do that they use hashing functions. These are functions that mangle data in peculiar ways. If you put the same data in then you get the same mangled data out every time, but to figure out what data went in to get a given output there's generally no faster approach than just guessing and checking every possible input. There are so many possible inputs that this takes an impractically long time, ideally. If a hacker does steal the database of hashed passwords then they will go about guessing and checking. They could start at the first account and start guessing common passwords until they give up or find it, then go on to the next one. That's unnecessarily slow, though. They can instead hash the first common password and compare it against *everyone's* hashed password, to see if anyone used it. Hashing functions are sometimes designed to be slow, such that computing tons of hashes takes more time and energy, so a hacker could set out and pre-compute the hash of every common password they know, then save that in a file. That file is a rainbow table. It lets them quickly lookup \"If a person's password hash is ABC, their password is XYZ.\" To defeat rainbow tables websites use what's called salt. This is just some extra random data that they add to each person's password before hashing it. It isn't secret, and it's likely that a hacker that steals the hashed passwords also steals the salt. What this does is it makes it so that the hacker can't just look up hashes in their rainbow table. They now have to go account by account, hashing all of their common passwords plus that account's salt to see if the hash matches. If the website had a million users this makes the hacker's job a million times harder."
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e32tuv | Why are saxophones so much louder than guitars? | More generally: Why are instruments you blow into so much louder than guitars, violins, pianos... | Technology | explainlikeimfive | {
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"Larger brass and woodwind instruments resonate much more loudly than guitars simply because of how they're constructed (i.e. from metals). Saxophones are also louder typically because saxophonists are obnoxious. Source: played saxophone for 10 years, was obnoxious.",
"Brass instruments are designed to make the air you blow vibrate stronger throughout the pathway of the instrument which makes it stronger; the keys change this pathway to produce different sounds. String instruments are designed to make the air that the string moves vibrate stronger. In the case of a guitar it is in the body where this strengthening occurs, and the sound is changed by the length of the string that is allowed to move. The biggest difference is that brass instruments have more time to strengthen the sound because of the longer path way, and their shape and material do a better job at this. String instruments have a smaller area to strengthen the sound and wood is not as good as brass at strengthening sound. That's why cymbals are made of brass instead of wood!"
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e34u5a | Why do some lights glow after being turned off? | Sometimes when you turn a light off it glows quite dimly, but it only happens with some lights, can anyone explain why this is? | Technology | explainlikeimfive | {
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"There are multiple reasons. Many lights have capacitors in them that store a charge. Once it's turned off that charge will slowly discharge through the electronics resulting in it being lit dimly for a while. Good quality lights should have a resistor in the circuit that will quickly drain this charge so it goes out immediately. Another way is that sometimes the current through the wiring induces a slight current in nearby wires. This can be enough to slightly power lights even when the switch is off. & #x200B; Another reason is that some lights like fluorescent bulbs, use phospors, a chemical that absorbs UV and then re emits it as visible light. These phosphors slowly discharge that light once the UV light is turned off. It's basically the same process as glow in the dark materials, but not as strong.",
"Modern lightbumbs are no generating light by heating, they use another, more efficient physical processes which will emit light that is not visible (UV light) Inside the light bulb is a powder made of a special material called non newtonien crystals, which will emit visible light if they receive UV light. This process is not instant, as the crystal will still keep glowing if the light is turned off, sometimes for several seconds, more if you have good eyes adapted to the obscurités"
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e35edc | why do some shoes crease and show signs of wear more than others, despite the same amout of usage? | Technology | explainlikeimfive | {
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"Depends where the leather for each particular shoe/boot had been cut from the hide. Leather cut from the belly, for instance, stretches more that leather cut from the shoulder. It's luck of the draw when buying."
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e38uvq | Cars with ultra bright blue LED things, why? | Technology | explainlikeimfive | {
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"They're brighter, which means they provide better visibility in the dark. This is very useful when there might be wildlife darting around on the edges of the road that you can't see with dimmer bulbs. With that said: a lot of what you're complaining about isn't the bulb, per se, but the aiming or height of the bulb. A pickup's lights will be about head-level with a sedan's driver's eyes, so they'll be more distracting by default."
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e3aeyb | How does electricity power a fan? | Technology | explainlikeimfive | {
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"Voltage pushes electrons through a coil. This coil becomes a magnet because of the electrons spinning through it. This magnet tries to align with another nearby magnet. This coil is then shut off and a new coil activates, which is rotated differently. Each coil pulls a different part of the spinning part towards the magnet. Boom; electric motor.",
"Most small motors, like fan motors, are of the induction type. This design is relatively simple and uses a stationary iron or steel core with copper wires wound through or around it. When alternating current goes through the wires, a continuously reversing magnetic field is created. Inserted into a hole in the core is the armature - a cylindrical block of metal with wires would through it, but these wires are much heavier and connected in a \"squirrel cage\" fashion to a copper ring on each end of the armature - hence these motors are sometimes called squirrel-cage motors. The previously-mentioned reversing magnetic field cuts through this cage of conductors, and induces a current in them (hence the term \"induction motor\"), which creates a second magnetic field that interacts with the first one, and the interactions (attractions and repulsions) between these fields cause the armature to rotate."
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e3d1ud | How does fps work in gaming compared to TV? | For example, playing games on your PC you would want 60 fps or more, but with TV and movies you are fine with 24fps. What's the difference? | Technology | explainlikeimfive | {
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"Tv shows a fixed scene. Games add motion and can have performance dips. Higher frames allow these dips to go unnoticed, thus the smoother feel when playing a game. Imagine a music beat playing at a fixed rhythm (metronome) as a tv show. A game beat you want to play fast enough that you cannot tell the difference from where one beat ends and the next one starts.",
"The key is responsiveness. Even in a GUI this makes a difference. 24fps is perfectly usable, but 60fps feels extremely smooth. In a game, this matters even more. Response feels immediate. We don't care about this in movies. They're not interactive.",
"TV and movies are mostly produced and edited. They can make the finished product not look like there are jerks and clips since it is a passive viewing environment - ie they can see what the viewers see and correct anything. Games are interactive and it isn't always predictable how the graphic elements move (how many and how they interact). A higher frame rate allows things to look a bit \"smoother\" when there are a lot of \"moving\" elements. This is very useful since the player is actively using the picture to decide on what they want to do next - jerky motion can make this tough.",
"The image taken from a camera is taken over an exposure time. If something moves during that time, it will create a blur - the motion blur. This is very close to how our own eyes perceive motion, and combined with some manual post processing, you get moving images that are very natural looking even at 24 Hz. The frame from a video game meanwhile is an instant snapshot, where moving objects are just as sharp as still objects. Therefore, moving objects don't blur together like they do in film, creating a very jagged and unnatural effect, which is especially noticeable if the camera moves rapidly. In order to make games look as smooth as a 24 fps film, they need to run at a higher framerate and use an artificial post-processing filter. A really good example for that is the machinima [Freeman's Mind]( URL_0 ), which looks much smoother at 30 fps than any game would at the same framerate. It was recorded at a very high framerate and the motion blur added in post-processing."
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e3dqtn | What do foundries actually do? | I mean I get that they produce semiconductors, but what is their part in the process. Like take Qualcomm or Apple ARM processor. ASML produces the machines while Qualcomm and Apple design the processor. What do the foundries like TSMC and Samsung Foundry do? Like is it just the infrastructure? I mean it can’t be as otherwise they would both be on the same level? | Technology | explainlikeimfive | {
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"Imagine it like a machine shop. Company A orders a design from a Engineering company B. These designs are manufactured by Machine shop C. Machine shop C needs a special tools that it orders from Specialist company D. Machine shops C needs stock that it gets from supplier E. Like. A processor is extremely complicated thing, it requires many parties to design and to manufacture. Like different systems in a chip can be made different companies. Imagine you are building a big building. You get an architect, structural engineer, electrical engineer, HVAC engineer, civil engineer and then you can design the house. After this you get a contractor, who gets other subcontractors, who get suppliers. At the end of this with proper management and correct allignment of the planets you got a functional building, on budget and within deadline. Nothing nowadays is actually done from start finish in house.",
"What is the conflict here? Qualcomm designs the processors, and ASML builds the machines that TSMC uses to actually manufacture the chips in large numbers."
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e3f77u | how do humidifiers work? | Technology | explainlikeimfive | {
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"There are lots of different designs but to put it simply, it’s a device with a reservoir of water that evaporates into the atmosphere, increasing humidity.",
"Some of them work by heating water, some work by using an ultrasonic transducer. Basically this is a type of speaker, which makes a vibration way higher frequency than what we could hear as sound, and it vibrates the body of water enough to make the top layer lift off as a mist. Then it's normally pushed out into the air with a fan. Those are the most common type of humidifier by a mile."
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e3gwxz | How did old school shooter gun games like duck hunt or arcade shooters accurately track your shots with only the gun and without a sensor bar or camera? | Technology | explainlikeimfive | {
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"When you point at a duck and pull the trigger, the computer in the NES blacks out the screen and the Zapper diode begins reception. Then, the computer flashes a solid white block around the targets you’re supposed to be shooting at. The photodiode in the Zapper detects the change in light intensity and tells the computer that it’s pointed at a lit target block — in others words, you should get a point because you hit a target. In the event of multiple targets, a white block is drawn around each potential target one at a time. The diode’s reception of light combined with the sequence of the drawing of the targets lets the computer know that you hit a target and which one it was. Of course, when you’re playing the game, you don’t notice the blackout and the targets flashing because it all happens in a fraction of a second.",
"There is a light sensor in the gun. when you pull the trigger the entire screen goes black and then each of the targets produces a white square one at a time. The camera in the gun notices whether it's looking at a white square when that happens and if it is then it is counted as a hit",
"I just want to say, oh dear the wording of that title is a little unfortunate. Anyway, the way it worked is neat. The screen blacks out, and the hitboxes for the ducks turn white. If the diode inside detects the change from dark to light, it registers a shot and gives you points. And if there's multiple targets, it goes one at a time and tries to find the delay. Because of the way it works, it actually can't be used on an LCD screen, only CRT.",
"The sensor in the gun would check if it was pointed at a white box that showed up for a brief moment on the screen where the target was. Sidenote: > old *school shooter* gun games Yikes that’s an unfortunate title.",
"> \"How did old school shooter-\" ....!? > \"gun games like duck hunt or arcade shooters-\" Oh, phew! /s Seriously, though, from what I recall, you would pull the trigger and the screen would go blank for a split-second. The blank screen would have a white box that pointed to where you shot the screen. This would work by the sensor is built into the gun. The white box would determine if you hit the target or not. The scanlines on the screen also play a part in it, as the boxes were built via the scanlines. This is also why a lot of old lightgun games don't work on flatscreens, since most flat screens don't use scanlines like CRTs.",
"To everyone who answered, THANK YOU. Also, I now see the unfortunate wording of my title, if I could change it I would. It should say old-school shooter, sorry about that....",
"The old NES light gun that was used with Duck Hunt, simply had a light sensor on it. The game would briefly flash the target on the screen in bright white when you pressed the trigger. If the light gun registered a bright light in the direction it was pointed the game counted that as a hit. Other than timing there was no way for the game to know if you perhaps pointed the gun at a different source of light to fake a hit. Other types of gun would for example be based on the timing of the electron beam sweeping across your crt display. Those devices won't work with modern displays. Some later ones had infra-red emitters placed around the screen and the gun measuring how far below and to the side of the emitters it was pointed. This required calibration and might not be as accurate.",
"As I recall, duck hunt used a simple light sensor in the back of the barrel. When you pull the trigger the screen turns black for a frame with a white square where the duck was. If the sensor reads light instead of black then you hit the duck.",
"Old school shooter game guns used pellets. The pellet would hit the metal \"duck\" and it would flip back showing the hit. If you didn't hit the target, the duck would remain upright. No sensor bar or camera was needed.",
"Here's what happens. When playing Duck Hunt you pull the trigger to shoot a duck out of the air. When that trigger is pulled, the TV screen goes entirely black for one frame. The light sensor uses that black screen as a reference point, which helps it account for the wide variety of lighting situations in the rooms where the game is being played. In the next frame, the area the duck occupied turns white while the rest of the screen remains black. If the light sensor detects light in that second frame, your gun is on target. If the light sensor does not, the dog is going to laugh at you. -DUSTIN NELSON Wait, How Did the 'Duck Hunt' Gun Work? URL_0 Also a video going over it URL_1",
"I remember hearing you could point the gun directly at say, a lightbulb and it would register 100%, because the gun was constantly recieving light. Is that true?",
"When you pull the trigger, the entire screen turns black for a single frame, and the target becomes a white block. The photodiode sensor inside the gun detects whether it is pointed at a white block or not, and determines if your shot hit or missed. This is the origin of the term “light gun,” as they are sometimes called. If you watch carefully while you’re playing, you can see this tiny flicker happen.",
"Not quite ELI5, but I hope you can follow along... In the nes gun, there is a light sensor. The old TV, the CRT, do not display the full image at once, but draw it pixel by pixel. The way it work is that there is an electron canon behind that fire at the front of the screen. This light a single pixel at a time. (For the sake of simplicity we'll forget the mess of the colors). There is some electromagnet on the sides and top of the tube that make the beam deviate. So, by changing how much current each coil have you can light any pixel at a time. Now, the TV have two oscillators, one is fast (15.734 kHz), the other slower (59.94 Hz). The first is connected to the left-right coils, while the second to the top-bottom one. This cause the electron beam move left to right (then reset to left), and top to bottom. In other words, the beam do each pixels in a line from left to right and top to bottom. When the electron beam hit the front of the screen, it actually hit some phosphore that light up. By varying the power of that beam, you make the pixel dimmer or brighter. The phosphore do not light up for a long time after the beam have left. In fact, it will be basically off when about 1/4 to 1/3 of the screen has been draw. Our eye however have a problem: it continue to send the light signal to our brain, so we think the image is there all the time (persistance of vision). The TV will sync the two oscillator on the incomming video signal. The signal have embedded sync pulses. Now, who generate that video signal and those pulses? Yup, the NES! Therefore it know exactly where it is in the image, as in which pixel it is now drawing. So, what happen when you pull the trigger? Two possibility: the annoying one: send a white picture and see when the zapper see a spike in light amount. When it does it just need to see where it is in the video signal, as in which pixel it is sending. The less annoying way is very simmilar: send a black image with white square only on the targets. Our eye is less sensitive to a black frame than a white frame, so it get less annoying. Again, it check for when it see a spike in light. Now, why don't it work on modern TV? Because of the way it work. Modern TV buffer the incomming video signal. Basically, it put the image in a first buffer. Once the first image has been fully received, it wait for the LCD to finish to draw the image, which is quite fast, and then swap the buffers. Now the new image is in the LCD memory, while it can overwrite the old image with the next image. This ensure that only a full image is displayed... But anyway, the important thing here is: buffer. This mean delays.You pull the trigger, the NES send the white image, it go in the buffer. The zapper saw no spike of light. And soon after the TV display the white image. But it is too late, the nes stopped to check as it is done writting the image and it found nothing. Remember, on CRT the signal being sent is immediatelly displayed on the screen with very little delays (read none). While the modern TV atleast have 1 image lag...",
"Fascinating bit of history: the light gun was initially invented and developed for use in the Semi-Automatic Ground Environment (SAGE) air-defense System used by the US Air Force in the late 1950s before NORAD. Radar operators would point light guns at their displays and the gun would see the scan line, and the computer knew based on when it saw the pulse where the display was in the process of drawing the screen, and thus where on the screen the gun was pointing. It was then able to identify what the operator was selecting. Cutting edge space age stuff in 1960. The vacuum tube computer that ran each SAGE site was housed in a giant bomb proof concrete building. It drew a few million watts and had the equivalent processing power of an Intel 80286 based personal computer 3 decades later. The Air Force had 30 of these sites, and the system was only in operation for a few years. About the time the 80286 computers came out is when video games started using light guns. In just a few decades, the light gun went from secret high tech military hardware to an electronic toy for kids.",
"Back then, the screens used a different technology, they mostly only lit one pixel at a time (pixels kinda faded away after being lit, but quickly faded away from the brightest they got), the image looked whole to the human eye due to persistence of vision, but with [high speed cameras]( URL_1 ) you can kinda see how it works. The way games like Duck Hunt worked, is the moment the trigger is pressed, the game first draws a fully black screen to get a base level of light (to deal with environment light and such), and then it would paint white only the area where the target was; it would then check if the light sensor on the tip of the gun picked white or not (it was basically like a single-pixel camera with strong zoom), at the exact moments where the white parts of the screen were being lit up to detect a hit (if there were multiple targets present, it would light up each target in order to identify which of them was hit). | Those games have a hard time working on modern screens because with modern screens the consoles no longer control individual pixels directly, they send the whole picture and the screen displays the frame when it feels like it; so the precise timing trick can't be trusted anymore. edit: Someone else posted [this video]( URL_0 ) on a reply to another comment here that illustrates how the tech works.",
"And why don’t they have any modern games like this? These types of games were fun.",
"There was a small light sensor in the guns. When the trigger was pulled, the screen goes black and a certain part of the screen lights up. If the sensor picks it up it counts a hit.",
"he old NES light gun that was used with Duck Hunt, simply had a light sensor on it. The game would briefly flash the target on the screen in bright white when you pressed the trigger. If the light gun registered an bright light in the direction it was pointed the game counted that as a hit. Other than timing there was no way for the game to know if you perhaps pointed the gun at a different source of light to fake a hit. Other types of gun would for based on the timing of the electron beam sweeping across your crt display. Those devices won't work with modern displays. Some later ones had infra-red emitters placed around the screen and the gun measuring how far below and to the side of the emitters it was pointed. This required calibration and might not be as accurate.."
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e3i0cm | Why are diesel mechanics and auto mechanics a different trade? | Technology | explainlikeimfive | {
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"Diesel mechanics work on other types of equipment including tractors, crane, big trucks, lifting equipment.",
"Because they're working on different engines that operate on different principles. Diesel has much higher compression and no spark plugs. Non-diesel don't have glow plugs. There are similarities, but if you're going to be a professional, you're gonna have to specialize. Aircraft Mechanic and Marine Mechanic are also different trades, because they are specialized versions of (essentially) automotive engines.",
"* a diesel mechanic works on engines, an auto mechanic works on all parts of the car * a diesel mechanic works on engines that might not be inside of an automobile * most auto mechanics can work on diesel engines in cars, when a diesel mechanic is called to work on a vehicle, it will usually a big one, like a tractor trailer or construction equipment",
"A microwave and an oven both cook food, but they do it in completely different ways. Both normally have a clock and timer. Both have a door. One you get past the few physical things that match and the similar end result, they actually have very little in common. Diesel and gasoline engines are just like this. They both use explosions to move pistons, but how they make that happen requires different parts and different parts means different knowledge.",
"The engines run differently. Unfortunately, I can only explain like I'm five because I really don't know the full detail. What I think I know is, diesel fuel ignites under pressure unlike gasoline. I don't think diesel engines use spark plugs but don't quote that in front of a mechanic. Diesel engines also use a fuel additive to help lower the emissions of the vehicle. It's called DEF. Diesel Emissions Fluid. I believe it is mixed with the fuel before combustion, again, could be wrong, but the idea is that this fluid will combine with the fuel and neutralize some of the harmful toxins that comes with diesel combustion. Gasoline engines use a spark plug in each cylinder because pressure won't ignite the gasoline. That's all I can tell you. I hope somebody adds onto this with more details.",
"A diesel technician is an auto technician that specializes in diesel engines and usually larger trucks/equipment. Usually, a diesel technician can work on a gas engine but an auto technician usually can only work on a gas engine for lack of knowledge/experience"
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e3n6q0 | My email address is [email protected], i just received a couple emails from [email protected]. how is this possible? | Technology | explainlikeimfive | {
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"Google Mail doesn’t care about dots. There’s a support doc here. URL_0 There’s a good chance this person hasn’t registered the same name... “JohnQcheesecake@gmail”, but possibly just uses it as a throwaway for registration onto websites.",
"Gmail doesn’t differentiate periods in addresses... pro-tip, insert a random period into a specific spot in address for signups you don’t want in your inbox and filter those, ie f.irstname.middleunitial.lastname",
"You sure they didn’t replace an l with an I?",
"The email standard doesn't account for full stops. From the point of view of most email systems Name.Initial.Surname at mail dot com is the same address as NameInitialSurname at mail dot com. It's in your inbox because Gmail doesn't differentiate between the two. Someone with a similar name as you most likely just gave the wrong address and it went to you."
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e3od1m | How do the antiplagiarism mechanisms work in uni? | Technology | explainlikeimfive | {
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"My honest answer is don't plagiarize... I know that's not what you wanted, but copying work in university will potentially get you kicked out, and with that on your record it will be harder to find another university that will accept you. As for exact mechanisms, in my experience it is going to be at the discretion of the instructor to look up any questionable information you have used by putting it through a number of different sites that will automatically flag anything that is too close to someone else's published online/print work. Code is different from what I've seen. Most of the time you can find solutions to assignments on Chegg and instructors know that so they check to see how close your code matches that solution. But if you only include code that you were actually taught how to use in class, and turn what you didn't learn into something similar that you did learn to create the same functionality you should be fine."
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e3s157 | How come turning wifi/data on and off again makes it work better? | Technology | explainlikeimfive | {
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"Like pretty much anything computer related, resetting fixes an abundance of issues. By starting something over it is forced to run all it's code from the beginning, refreshing anything that might have gotten out of whack. I don't have a specific technical answer because it could be a whole number of things making your wifi or data not work well in the first place, but in short, it's like when you're in a conversation with someone and you get confused and say \"woah woah hold on let's start over.\"",
"One potential cause can occur if you are on some sort of extended network system where many access points (APs) are all broadcasting the same SSID (that is, a bunch of antennas all pretending to be the same network that shows up on your device). You'll usually find these in large offices or school campuses. Even though these APs are all the same network, most basic configurations can only let you talk to one of these APs at a time, so your device can still tell them apart. To that end, when you connect your device to one of them, it will do everything in its ability to stay connected to *that* AP in particular, no matter how bad the signal gets, even if a better connection to a different AP is nearby. That is, if you're walking about and roam out of the zone of the first AP you connected to, your signal will get worse and worse, even if there are other APs in your area to cover you. Your device will only break the connection and start over on its own if the original connection outright times out. Cycling your network connectivity forces your device to drop the old connection and look again, which will presumably select the strongest signal in your area. Newer network equipment is being made that can address this by giving the central router the ability to detect signal strengths of clients and dynamically route traffic through the best AP possible, making the switch seamless. These are marketed as \"WiFi mesh\" systems. I'm not at all versed on how the cellular network system operates, but I think it has some parallels to a Wi-Fi mesh system, with towers dynamically trying to shift you between one another seamlessly as you roam, but due to their greater distances and higher volume of clients this can be unreliable. Turning data off and on can easily shift you to a new tower if you are in range of more than one. You can often verify that this has happened by checking your public IP address before and after cycling.",
"There are probably many more reasons, but maybe one is that the WiFi changes the channel being used which might have been being jammed by noise. It's like if many people are speaking English in a room, so to make things a little clearer you switch to German. Sure, the noise remains the same but because you're talking a different language you don't get confused by the English words. In the same way WiFi has different channels it uses, which are basically bands of frequency."
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e3s9j4 | Why using electric car/scooter is more friendly to environment, despite that (high percentage) electric is made by burning fuel or coal? | Technology | explainlikeimfive | {
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"Gasoline engines are very inefficient. Maybe 20% on a good day. Electric motors in cars are in the 98% range iirc, and gasoline power plants are more like 40% efficient. Add to that the fact that a lot of power comes from solar, wind, and nukes, and you have a pretty substantial reduction in carbon footprint.",
"Because even if the electricity comes from fossil fuels, a plant can convert it much more efficiently compared to a car engine. Think about it, your engine would keep running even when you're stuck in traffic / idling. It needs to function over a wider speed range, portions of which it wouldn't be efficient at. Also, most importantly, using EVs opens up opportunities to use cleaner sources of energy in the future.",
"In addition to these other reasons: consider HOW the gasoline gets to the gas station before you put in your tank. 1. It takes about 1/16th of a gallon of oil to refine crude to its other forms like gasoline for every gallon of gas. 2. 2. That gasoline doesn't just flow to your gas station in most cases (pipelines.) It takes a tanker truck. That truck uses fossil fuels to run. That tanker takes a petroleum product to cool its engine, reduced friction in its wheels, axles, transmission and drive gears and \"fifth wheel\". These are all fossil fuel products and they all evaporate (to a small degree) when the truck is used to haul your gas. 3. Multiply that by 10's of THOUSANDS of these trucks every day and it adds up.",
"Because even if you account for the contribution of fossil fuels to the energy an EV uses, [99% of the US' population]( URL_1 ) live in places where driving a Model 3 will yield lower per-mile emissions than even a Prius. In Europe, EVs [also realize significantly lower lifecycle emissions than diesels]( URL_0 ).",
"And yes even mining for the ores required for the batteries is more friendly to the environment than pure oil."
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"https://blog.ucsusa.org/dave-reichmuth/new-data-show-electric-vehicles-continue-to-get-cleaner"
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e3sds5 | what are ratios when it comes to visual electronic displays? | I’m playing the game “The Division” and I was reading that the game is based on a 1:1 scale of NYC. What does this mean in simple terms? | Technology | explainlikeimfive | {
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"Any visual ratio is based upon a real and given metric (or imperialistic if you use burgerland units). A 1:1 map of will be the exact same size as a real area. A 1:3 map will be a third of the size. Think of your colon as a dividing line in this respect."
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e3sfts | What is an induction motor? | This is Wikipedia's definition - URL_0 'An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding' I know that a motor is a machine designed to convert one form of energy into mechanical energy(car engine being a motor) Can someone give an ELI5 explanation for this motor and how did Nikola Tesla made this discovery? What were motors like before this discovery? | Technology | explainlikeimfive | {
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"text": [
"Normal motors are DC motors, synchronous AC motors, or universal motors. Induction motors are unique in that they provide torque at a wide range of RPMs while requiring no contacts that can wear out. Metals tend to resist moving magnetic fields. If you move a powerful magnet quickly past some metal, the metal will get tugged along. Induction motors use electricity to create a rotating magnetic field around a piece of metal, and the metal tries to spin with the field."
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e3t1hi | why are walkie talkies only able to send signals or receive signals, and not both at the same time? | Technology | explainlikeimfive | {
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"text": [
"They use one radio frequency. If they tried to transmit and receive at the same frequency at the same time, you'd just get a ton of audio feedback. Even if not, you'd still probably get a fair amount of feedback."
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e3tkba | How did the discovery of fire by early humans and the means to control it spread throughout the world? | When humanity discovered fire, surely that was an isolated thing in only one or two groups of homo sapiens. How did the knowledge of control of fire spread across every continent simultaneously when humans were so isolated at the time? | Technology | explainlikeimfive | {
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"text": [
"The ability to create and use fire was discovered between 400000 and 1.7 million years ago by human ancestors. Long before Homo Sapiens Our species has never been without the ability to create fire. The discovery pre-dates humans. The knowledge spread with us to different continents.",
"Fire occurs naturally (a lightning strike on a dry dead tree, for example). The knowledge of how to control and use fire would have developed simultaneously in different places."
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e3twwm | How does noise-cancelling devices work or create a silent bubble? | Technology | explainlikeimfive | {
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"text": [
"In true ELI5 fashion: Sound is created by vibrations in the air. So when something makes a sound, the air vibrates and hits your ears. This in turn makes your eardrums vibrate and your brain interprets the signal. This vibration is kind of like a wave. You might have seen a graphic of a sound wave before. Funnily enough a sound wave can be cancelled out by another sound wave. In this case by emitting a wave that is opposite to the noise. So when a noise-cancelling headset is active its actually listening to the environment and tries to create antiwaves in order to cancel out any constant noise. You may have experienced that sharp sudden noises aren’t cancelled effectively. That’s because there isn’t enough time to create an antiwave. But constant sounds are easier to negate.",
"The have a microphone that detects the noise frequency and they digitally create a same frequency with a phase shift of 180deg cancelling each other..."
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e3yq5f | how my computer identifies subjects from conversations I've had -- or texts I've sent or received -- to embed targeted advertising into web pages (I think I have my microphones turned off on my devices.) | For example, yesterday I talked to my family about needing window shades. I did not look them up on the Internet. Today, I have had several ads for window shades show up as I browse. I don't have a smart speaker, no smart TV, and I thought I had Siri turned off. How does this work? | Technology | explainlikeimfive | {
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"I could be wrong but I believe if someone in your close group of friends or family decided to look up window shades or blinders targeted ads may think you may be interested in that as well.",
"Its likely your phone, especially if you use facebook. Your advertising profile will easily follow from device to device as they know who you are on each machine. Most phones come with facebook preinstalled to mine as much data as possible.",
"May be confirmation bias (when your brain is subconsciously looking for certain things and makes them seem more abundant than they are) or if you EVER typed it on your device cookies will notice and show you ads. For example, I was looking at adapters for a rare kind of cable on the Walmart website. Later, I was playing a game on my phone and got an ad for the EXACT product I was looking at. I hope this answers your question!",
"Even if Siri isn't on your phone listens to you a lot. On Android you can turn off microphone permission for all of the apps including Google. You can go to this site to turn off lots of different tracking (it doesn't block everything but does help a lot. URL_0",
"Siri is listening even when she's turned off. If what you say is accurate, that is the most reasonable explanation. Regarding texts, that's easy. Everything you type on your phone is transmitted somewhere, and passes through multiple points of collection."
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e3yvor | - measuring the ocean sizes before flight | Technology | explainlikeimfive | {
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"text": [
"You can figure out longitude and latitude using the sky. You can stand one one side of the ocean and figure out where you are, then stand on the other side and figure out where you are then figure out how far apart they are."
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e4223b | why do Firefox and chrome use so much memory to run? | Technology | explainlikeimfive | {
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"text": [
"To make it run faster. Basically thats it. Using up memory and having all the processes loaded up in memory helps the end user interact with the software faster. Its not a \"bad\" thing to use a lot of memory, in fact in this case its probably a good thing since the browser will be running much faster if all this stuff is loaded up in memory rather than not. In the end of the day, unused memory is wasted, so if there is memory available to use, its best to use it. Many programs take advantage of this to improve performance And in the current world, where 8GB of RAM (or more) is standard, there is generally far more than enough memory available for programs like your browser to use a lot of memory and still leave tons leftover for any other use",
"Using up all your RAM is a lot harder than it used to be. Programs using a lot of RAM won't effect your computer's speed like it used to, instead, by having that freedom, they can load up as much information as they can to your ultra-fast RAM and end up making things faster for you. When 2gb of RAM was big, and background processes took 1gb at peak, it meant it was going to be very difficult to allocate about 1gb to games back at that time. Now, with 16gb being much more common, even if games soak up a whopping 4gb, it's going to be so much harder to get close to all 16gb for the casual user, so that extra space is utilized. As long as you're not maxing out and having to hit your page file (slow version of RAM basically on your hard drive as an overflow just if it's necessary), any unused RAM is wasted speed potential."
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e43anh | Even when Sony and Microsoft has allowed it, why is crossplay in games difficult to develop? | Technology | explainlikeimfive | {
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"text": [
"There are multiple reasons why crossplatform play is difficult to implement. Hardware and connectivity requirements can differ between consoles and computers. If things like Framerates, screen refresh, and processing power is locked on consoles that might offer an unfair advantage to PC players who are less restricted in those areas. the difference between controllers vs keyboard set ups might also offer a distinct advantage to certain games. Different versions of the same game might have software differences that are difficult to make compatible with each other. Consoles that might rely on peer to peer game hosting would be at a disadvantage to computer players who don’t follow that model. PC games are much more prone to cheating and game modification that might offer unfair advantages or content that Console players don’t have. They would have to develop a universal system for player interaction through VoIP and dashboard interactions like game invites/communications.",
"Cross play is not difficult to develop, it literally is just a case of allowing people from both networks to join the same servers. I don't know who told you it is difficult to develop because it is not. **EDIT:** for anyone who doesn't believe me, there are two documented cases that show it really is as simple as flicking a switch, both rocket league and fortnite before cross play was allowed accidentally enabled crossplay between the xbone and ps4. If you can do it by accident it is not hard to develop."
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e45dfx | How does the dust caught in an iPhone charging port not catch fire if it’s caught in the electric current? | Technology | explainlikeimfive | {
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"text": [
"Dust is a pretty crappy conductor, it won't let much current go through it. If the dust is the only path between the charger and the phone then the phone just won't charge, it won't be able to get enough current through with just the 5 volts provided by the charger. If the dust isn't the only path between the charger and the phone then the current will flow through those other paths and not through the dust almost at all. The resistance of the dust is so high and the voltage off the charger is so low that you simply can't get enough power loss in the dust to ignite it."
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e4brvt | Why do ‘tactical’ flashlights use red lenses? | I’ve heard it was because red light waves don’t travel that far, but I can see the red light on an airplane wing that’s miles away. | Technology | explainlikeimfive | {
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"text": [
"Greetings from /r/flashlight. First of all, \"tactical\" flashlight doesn't have a fixed definition - it tends to be more of a marketing term. Most lights marketed as \"tactical\" don't have a red LED or include a red filter. We do see a number of posts from people in various armies asking for lights with red capability though, usually because someone well above their pay grade has mandated it for reducing observability. Oddly, there doesn't seem to be any limit on output or intensity most of the time, and someone looking upon [this]( URL_0 ) from a mile away would easily be able to tell someone is using a light source. There's also a perception that red light doesn't ruin dark adaptation. It's half-true: at similar intensity, red light will have less impact than white, but it's harder to see what you're doing with red light, so it kind of evens out. I'd make the same argument for observability: the most important factors are to use as little light as possible, and avoid pointing light sources directly toward where an observer might be. Much of this doctrine was likely developed long before the advent of modern LED-based flashlights, which can support dimming between a hundredth of a lumen (literally thirty times dimmer than a firefly) to over a thousand (car headlight). A red filter substantially reduces the brightness of a fixed-brightness white light.",
"I was adding to the other posters. A tactical flashlight is meant for situations where you want to see without being seen. It gives enough light for you to read a map by, but allows you to get closer to an opponent without him seeing you do it.",
"To not mess up your natural night vision. Also, I believe it doesn't show up on night vision/IR."
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e4btwu | why do blow dryers consume so much power? | Technology | explainlikeimfive | {
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"text": [
"We generally don't realize how much energy it takes to generate heat. Our electronics are so efficient that they use far less energy than is created by, say, a large candle. My entire gaming computer only produces maybe 200 watts, or 6 tea candles' worth of heat. That's really not a lot. A blowdryer, meanwhile, is more like 56 tea candles. It is making the air quite hot, and moving a *lot* of that air."
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e4c9ib | - What exactly is the "exposure" in photography? | Like, for instance, I've seen photos of the night sky with crazy details of the stars and they say that this picture was taken with "12 hours exposure". What does that mean exactly and what does it do? | Technology | explainlikeimfive | {
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"“Exposure” in photography is a combination of three things: 1) the size of the hole through which the light is being gathered (“aperture”), 2) the sensitivity of the film or electronic sensor (“sensitivity” or “ISO”), and 3) the time that the sensor is exposed to the light (“exposure time” or “shutter speed”). The combination that’s right for a given set of circumstances will depend on various things, such as the amount of light that’s coming off the thing you want to photograph, the amount it’s moving with respect to the camera, and the required distances that need to be in focus. For most everyday photography in daylight, a normal shutter speed (exposure time) would be around 1/30 to 1/500 of a second. Photographing stars would require a much longer exposure time because they’re much dimmer than a normal daytime scene. An exposure time for stars using a normal camera would often be several minutes. Any reasonably advanced camera would support this kind of long exposure, but it would normally require a special setting on the camera. Such a long exposure will require the camera to be locked down on a tripod or similar. (For a sharp picture, the camera has to be still during the exposure and nobody can hold a camera still enough for such a long time.) Because the stars are moving in relation to the camera (the stars are still but the camera is fixed to the Earth and the Earth is rotating under the stars) the stars will often appear to move during the exposure and the resulting image will show the stars as lines (in a “star trail” picture). An exposure time of a few minutes is enough for the stars to move enough to start forming these lines. To have a long exposure of several minutes (edit to add: or hours, as in your example) but still keep the stars as fixed points rather than star trails, the camera can be mounted on a special device that very slowly moves the camera to compensate for the Earth’s rotation and keeps the stars stationary in the view the camera is pointing at.",
"No expert here, but I think it comes from having to expose film to light for chemical changes on the film to happen. The longer the film was exposed to light, the more details you could make out on it.",
"Stars are very, very dim. When you take a picture, you are exposing the frame for a period of time, usually just a fraction of a second, but you can control that amount of time. When they say a 12 hour exposure, they mean that literally. The frame has been exposed for that time, letting an incredible amount of light in. Of course, any movement in the cameras field of view will come across as a blur, so the movement of the earth comes into play at that point. For stars, you don’t need hours, just enough time to capture enough light. Lens choice and camera sensitivity also help."
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e4hpwo | why does a phones wifi control a drone up to 150ft in the sky, but home wifi only works well within 30ft or less? | Technology | explainlikeimfive | {
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"text": [
"You are usually in line of sight to the drone, outside, but in the house there are many obstructions such as walls, furniture, and items like clothing that absorb the radio waves.",
"How buildings and homes are built are death to Wi-Fi - basically steel studs, nails, screws...anything short and metal are going to block or attenuate the Wi-Fi radio signal. Worse is the higher frequency they go, the worse that attenuation gets. 2.4GHz has a wavelength of about 12.5cm and 5GHz is about 6cm so those nails, steel studs, the edges of the studs and screws are all perfect for reflecting and interfering",
"Everybody talking eye of sight. But those sick videos of drone racing inside abandoned buildings? They set some kind of beacons or signal repetears?",
"At microwave frequencies on which WiFi operates, the signal is reduced significantly by any obstacles in between the transmitter and receiver (such as walls, concrete, furniture, people, trees, moreso with anything that has a high water content). The fact that water absorbs microwave radiation (specifically at 2.4GHz, same as WiFi, causing it to heat up) is the basis of how a microwave oven works. However, if there is unobstructed line-of-sight between the transmitter / receiver which will be the case of a drone in the open air, the signal can go a very very long way despite WiFi being very low power. Some microwave links between towers / buildings can work over distances of 50km+ using the same power output as a home WiFi router using directional antennas. If the drone loses the line-of-sight e.g. if it goes behind a building / hill / trees, you are likely to lose it unless you can get the line of sight back. Some drones are programmed to take automatic actions such as increasing altitude / reverse course and backtrack in an attempt to restore signal."
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e4lfs5 | how is music able to be unevenly distributed through headphones? | You know when you’re listening to layered music and you hear the drums on your left ear, and guitar in the right ear......seems like I don’t notice this when playing old time music, so I assume it’s something that has to be programed? in. Would this mean it takes longer to produce music today than before the widespread use of headphones? | Technology | explainlikeimfive | {
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"So others have mentioned that this is called stereo sound, and no it doesn't have to be programmed. There is one channel for each headphone, so each ear is getting slightly different audio (surround sound works similarly, there are just more channels). When mixing, each input (microphone or instrument input) can be panned, meaning you are sending different levels of the signal to the right and left channels. Because our brains locate sounds based in part on the difference in volume received by each ear, the stereo effect makes it seem like that instrument or voice is coming from a certain direction. It is one of the ways to create separation in a mix. The effect is more pronounced when wearing headphones because the speakers are angled wider than say the speakers in your car. Also, there are stereo recording techniques that are used to create the stereo effect. These are used often when recording ensembles (such as a choir or orchestra) as well as grand pianos or acoustic guitars (in certain circumstances). These techniques use two microphones on the source instead of one. The left microphone is panned hard left and the right microphone is panned hard right. This attempts to recreate what it would sound like if you were actually present.",
"Stereo music has existed since the 1950s, and became increasingly common throughout the 60s and 70s. You don't need headphones to hear stereo sound, you can hear it with a good speaker system.",
"My parents have a old vinyl record of a train going from left to right, which demonstrated the stereo effect quite well. I suspect that recording left and right separately is a lot easier in the digital age. You can edit and synchronise the two streams quite easily, unlike the magnetic tapes they used to use. But I've definitely heard old recordings with stereo, specifically orchestral works, where you can hear violins on the one channel and cellos on the other. I imagine a studio recording might have been more likely to record to a single channel."
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e4on5s | Why dont you get shocked when you hold a AA battery by its positive and negative. | Technology | explainlikeimfive | {
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"You have high resistance. At least 100KΩ, so that over 1.5V you're getting a current too small for you to sense. It would take 20x more voltage for you to feel it, 50X more to shock you.",
"It's just not enough voltage to feel a shock. Even a 12v car battery won't actually shock you if you touch both terminals unless your hands are wet, but you might feel a slight tingle. That trope in movies where someone gets tortured with a car battery is fake.",
"As the others have said, your skin has a resistance to electricity, and it would take more voltage than 1.5 Volts that the battery provides to break through. A 9V battery still doesn't overcome the skin resistance, but place it on your tongue (wet, and mucous membrane NOT skin) and you'll feel it.",
"relatively low voltage. AA batteries will try to deliver 1.5 volts. if you connected six of them together you could probably get a shock/buzz similar to a 9V battery. Although that also depends on other factors like conductivity, think of the difference between using your fingers or using your tongue to connect the ends of a 9V battery... it clearly feels different, and that's down the conductivity of the points used to connect the terminals of the battery.",
"So if I touched both ends of my car battery how much would I feel? A nasty shock? Slight shock? Or like nothing at all?",
"So, in theory, you would drain a battery if you held it like this for long enough?"
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e4p76z | What is cloud virtualisation? | Technology | explainlikeimfive | {
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"Ignoring all of the technical facts regarding how virtualiztion works, think about how you boot up a video game in Windows. It's a program that runs off of Windows. Now imagine that the video game you're playing is Windows 10. In a very, very basic nutshell, that's what virtualization is. As to why this is a thing, it's to cut down on hardware costs. Let's say you need to deploy 10 servers at a business in order for it to run the way the owner wants it to. You can either buy 10 servers, or you can buy 2 servers, and use virtualization to run all 10 server OS's on the two physical servers. 5 OS's on one, 5 OS's on the other. Save a ton of money that way and it's also more efficient. For the Cloud part of it, all that it means is that the physical servers reside off-site. The best example of this is Amazon Web Services. You pay them some money and they spin up a Virtual Server for you that you can access from wherever, or pipe a direct path from the cloud server to the building your business resides in. To specify a little further, almost every aspect of cloud computing you do is going to be virtualized. You are never going to have a dedicated machine at Amazon's data center that is just yours. You will be running a virtual machine that is running off of a physical server, and dozens of other people's virtual machines will be running off of it as well."
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e4qjwi | How does an oxygen concentrator work? | I don't mean plug it in and turn it on, I mean is it an electrical process that separates oxygen from nitrogen and pumps it through or is it a chemical process or magic or something else? | Technology | explainlikeimfive | {
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"As I understand it the process typically used is that of pressure swing adsorption. Normal air is increased in pressure and passed over a bed of zeolite. At such pressure nitrogen tends to be attracted to solid surfaces such as the porous zeolite, sticking to it more strongly than oxygen. This increases the concentration of oxygen in the remaining gas and when pressure is release the nitrogen returns to gas so the zeolite can be reused."
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e4rqon | What dictates how bright or dark a phone screen can get? | Technology | explainlikeimfive | {
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"Typical LCD screens have a white backlight and on top of that is a liquid crystal panel that can block certain colors, or all of them. If you block green and blue light, the display will look red, for example. If you also block the red light, the display will be dark. The easiest way to make a display brighter is to make the backlight more powerful. This is relatively simple since it's easy to produce bright white light. The problem with that is that the LCD panel on top does not block 100% of the light, so if your backlight is too bright, areas that are supposed to be black look gray instead. That means how bright or dark it can get depends on how good the LCD is at blocking and passing light. Ideally you would want a panel that can go from 100% transparent to 100% opaque. That way you could have a very bright backlight and still get perfect blacks. In the real world LCDs are neither 100% transparent nor 100% opaque, so it's always a trade-off between maximum brightness and dark enough blacks. OLED screens work on a different principle because they don't have a backlight and each (sub-)pixel can emit light. So you get almost perfect blacks when a pixel is off, and the maximum brightness is limited by how much light you can squeeze out of a tiny, tiny LED."
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e4whe2 | Why do some programs take ages to close when task manager closes them instantly? | Technology | explainlikeimfive | {
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"The task manager kills things instantly and forcefully. This means the program doesn't get to do anything in response, and doesn't even know it's being closed, so it can't clean up after itself, can't ask if you'd like to save your work, etc. Closing a program the normal way sends it a message: \"please close now\". This means the program has to receive the message (which may not happen immediately). Then some of those will have internal parts of themselves that will go through the same sort of process: they'll get sent a message from the main program, have to receive it, and terminate. This can take time. Windows monitors the message queue, and if it's not being read then eventually it'll just offer to kill the program by force.",
"If you hit the 'x' button in windows, it asks the program to shut down. This basically tells the program to run its shutdown routine, allowing it to do stuff such as save unsaved documents before hitting a piece of code which exits the program for good. Now if the program gets hung up, it might not ever get there and will never quit on its own. The task manager can give commands to the parts of windows that control all the programs running on the computer. At the core of that is the kernel, which allocates CPU power to programs (among other things). The task manager can tell the kernel to stop running the program, so it simply no longer runs on your computer and takes up no more memory space.",
"X button = would you be so kind as to run your shut down routine, take as long as you like, and close please? Task Manager = fuck off, right now.",
"Well you can ask your room-mate to leave, they'd need to clean up after themselves, pack up their stuff and everything. Or on the other hand you could just kill them and toss all their shit out the window.",
"Usually program is told \"close now\" when you press x. Program obeys and does whatever programmer set it to do in case of closing down, things like saving unsaved stuff, finishing operations it was in the middle of doing etc, before actually telling OS that \"I'm ready, you can do the cleanup\" Task manager does things more forcefully. It doesn't ask, it just takes program out of queue for cpu time, marks all the ram used by program as free, etc, all the cleanup. This works quite reliably, but hopefully it's obvious why this can be troublesome. Anything the program was doing is lost. No matter how critical. It's the difference of security guard at shop or something saying \"we're about to close for the day, you should leave now\" and the security guard just coming at you, grabbing you and throwing you out.",
"Pressing the quit or x button is like asking a customer to leave your coffee shop because you are closing soon. They still have the opportunity to finish their drink, newspaper, and donut before gathering their belongings and leaving. Force quiting in task manager is like going up to said customer and tossing them out of the building by their pant waist and shirt collar; cartoon style. After, you go to their table and toss all of their belongings in the trash, because they didn't have time to save them.",
"A program normally has a cleanup procedure before shutting down, e.g. save unsaved changes, write into log file, etc. The task manager shuts down a program forcefully and abruptly, i.e. it just closes and frees all allocated resources of processes belonged to the program without doing the cleanup procedure.",
"Your computer is the bar. The program you're trying to close is the guy who has had one too many and fallen asleep at his table. He's not buying any more drinks and he's taking up space that could be used by people who will. Closing the program normally is when you send one of your wait staff to nudge the guy awake, make sure he's paid his tab and usher him outside into a waiting taxi. Closing the program with Task Manager is getting the bouncer to just hurl him out into the street because you can't get him to wake up. If he left his coat behind, tough.",
"What if the task manager can't close a program? What causes this?"
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e4wq0h | What do the numbers next to Graphic cards and other PC hardware mean? | For years it has annoyed me that I don't know and I need clarity, thanks in advance. | Technology | explainlikeimfive | {
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"What exactly are you referring to?. But in general, model numbers are completely arbitrary and are used to place a particular offering in a specific spot in the company's line of offerings."
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e4y8ok | Why are so many tech problems solved by turning things off and on again? | Technology | explainlikeimfive | {
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"Poor explanations so far so here goes. ELI18: There's Non-Volatile storage (A hard drive for example) and Volatile storage. Non volatile storage is able to persistently store data by hard-writing it to for example a block in flash memory. Volatile storage works more directly with electricity. Each bit has a capacitor, this is what makes up the data in RAM. These capacitors \"leak\" very very fast, and so when they lose power they will immediately leak until empty, where data is lost. Programs use RAM to store data that may be used frequently, because using RAM is much faster than pulling from the hard drive. Programs aren't perfect, and frequently make errors. It might store data it thinks it hasn't stored but it has, creating memory leaks meaning things slow down because there's less memory. Restarting the machine clears the RAM, and as such clears the errors the program has caused. ELI5: You have a sink. You wash the dishes every now and then. Sometimes, a bit of food comes off and goes into the food filter at the plug hole, but the water still drains so it's okay. Eventually there's too much food in the filter and the water is taking too long to drain. You pull out the filter and clean it, and the water now works fine. The sink is your PC. The tap is a program. The water is data. The filter is memory. The food is programs making errors.",
"If something isn't working right, it's likely that this is because the software got into a state it shouldn't be in. If you turn it off and on again, you might reset it to a known state, namely the one that it's in when it's turned on. Some problems aren't solved by this... If you managed to store into persistent storage that the software should go into a weird state at startup, then you'll have to do something else, like a factory reset.",
"The reason most tech problems are solved by turning things off and on is that it stop everything happening and gives the \"tech\" a fresh start. Basically most issues are caused by tasks trying to get through a doorway an one task is standing in the doorway, yes tasks can still squeeze through but untill the problem tasks moves issues will occur. Rebooting removes both the task in the way and all the tasks waiting to go through.",
"It's usually state conflicts which are a result of bad programming. For example, let's say that a device that can be connected to a computer and has a battery, like a camera, wireless mouse or a cellphone has these two states, \"connected\" and \"charging\", each of which can be either true or false: Let's make a table: ||deviceIsConnected |deviceIsCharging | |:-|:-|:-| |Makes sense|true|true| |Battery is full|true|false| |**Doesn't make sense**|false|true| |Makes sense|false|false| Now let's imagine that for some reason the device managed to get into a state where it thinks it's charging but not connected, which isn't possible. Maybe the user was fiddling with the cable, or there was some weird issue in the device's programming or in the hardware. The programmer hasn't thought that this situation might ever occur so the program doesn't know where to go from here and it's basically broken. A surefire way to fix it is to start from scratch by turning it off and on.",
"Let's start with an analogy. I'm going over to my friend's house, but I don't know where he lives. My friend gives me directions, but he's not very good at giving directions and he doesn't really know the names of streets very well. So I'm supposed to \"go north on that one main road\" and then \"turn right at that big funny tree\", \"go down about 3 or 4 stop signs\" and finally my friend lives \"2 doors down from the brown house\". I hop in my car, do my best and...get lost. At this point, I could call my friend and try to get directions from wherever I am now (and I don't know where that is, exactly) or I could go back the way I came, go back to my house, and start over. power-off is a known state for electronics, where RAM is cleared and the processor is not doing anything. The boot-up process is pretty well defined as well, with specific tasks happening in specific order. After that, things aren't well-defined. The system needs to respond to inputs which come at seemingly random times in seemingly random order. As these inputs are handled the system, assuming it's not perfectly designed, may start to become more and more disordered. Eventually, bugs start being triggered (there are, on average, between 15-50 bugs per 1000 lines of code depending on developer skill, and while many of these may be very minor, when you run long enough you're bound to trip over some of them). Powering off and on again clears memory, removes the built-up disorder, and moves into a well-defined boot-up process.",
"Okay so you have a computer that is stuck on something, it could be a feedback loop, a stuck programme, some bad code,whatever, a hard reset shuts these programmes down, restarts the loop and zeroes bad values. Now your computer works again, it dosent work all the time though",
"This isn't the most common reason that this solution works (already a lot of good answers for that) but one reason why asking a user to try turning something off and then on again is a smart first step: Because \"can you try turning it off and then on again\" sounds much less insulting than \"are you sure it's turned on?\" By asking the user to turn it off and then on, you have a built in way of confirming they've turned it on. A similar strategy for printers and peripheral devices is \"can you try unplugging it and plugging it back in?\" You'd be amazed how many calls end with \"oh…um, I think I found the problem.\""
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e4z2dg | How does Autofocus in a camera work? | Technology | explainlikeimfive | {
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"Nowadays the most common way of autofocus measures the contrast (difference in brightness) between the pixels while shifting the lenses. Once the contrast value is as large as possible, you have a sharp picture. Another common way of autofocus is phase detection. This is a bit more complicated. The camera will look at two different spots within the picture and try to recognize similar patterns of light intensity. Then it tries to get them to overlap by moving the lenses. [This]( URL_0 ) picture from Wikipedia shows the general idea quite well. & #x200B; There are also other methods like measuring the distance using ultrasound, but these are far less common or outdated."
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e51029 | how can a Pulse Monitor Watch (e.g. Fitbit Watch) know when you fell asleep, and when your REM, light sleep and deep sleep hit? I don’t get it | Technology | explainlikeimfive | {
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"The science is still very shaky, and you should take anything from these devices as helpful, and more than you would have known without them, but not as \"truth.\" Early watches used activity to stage sleep, because in REM sleep you don't move. But you don't move much when sleeping regardless, so that's generally not useful on a night-by-night basis. Heart rate and heart rate variability also show some changes that seem to line up with the changes seen in your cortex (the thin other layer of brain in which REM occurs, and from which sleep stages are measured), but no one has yet done definitive studies about the body's sleep cycles and how they like to with these cortical sleep cycles. Sleep as a scientific field is kind of stuck in cortex, which is a problem. So, several companies use machine learning and related approaches to generate algorithms that look at heart rate (or other things they measure) any compute probable sleep stages based on comparisons from people wearing a given device and also sleeping in a sleep lab. These algorithms are notoriously over-fit, which means they work great if you happen to be very similar to those people who were the test subjects (usually means young white male with no sleep problems), and very poorly otherwise. Encourage your favorite wearable to invest more in real science and not just marketing. There's a lot of good these devices can do by helping people be aware of their bodies, but there's a lot of snake oil going around right now, and that erodes trust and makes real learning harder. Companies love to hear from you. Write them and ask for more science."
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e52cmb | How do app testers emulate iOS? | I recently found a service that lets you test your mobile apps ( URL_0 ) and they run on Android and iOS. I know Android is open source so it's easy to modify it to run on the web but how did these vendors manage to perfectly emulate iOS which is proprietary? | Technology | explainlikeimfive | {
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"Technically, these apps aren't running on \"the web\". It appears that the emulation is being done on their server and just the video output of the emulator is being sent over the web. just a guess here, but I suspect they're running the standard Apple iOS Emulator and have way of screen capture & streaming of the single window of the emulator."
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e53ysw | What is light rail? Are there any advantages of Light rail over streetcars or busses? | Technology | explainlikeimfive | {
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"Light rail = subways or their above-ground equivalent. Trains that move people on tracks that aren't suitable for moving cargo. The advantage of light rail over streetcars/buses is that they do not travel on the road network. They are either in a separate right-of-way or they are underground. This means that they add nothing to traffic congestion, while removing commuters that would otherwise be adding more cars to the road network."
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e541a3 | - why do smartphones charge slower in cold temperatures? | Technology | explainlikeimfive | {
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"Batteries produce power via a chemical reaction. Rechargeable batteries reverse this reaction when a charge is run through it. Temperature can effect how easily a reaction can occur. Whats more, different temperatures can change what reactions will occur. In effect, charging a battery outside of its optimal range will reduce how many effective charges it can take. So your phone is programmed to reduce how quickly it charges the battery, which reduces the adverse effects of charging at those temperatures.",
"Batteries are designed to operate in an optimal range of temperatures. Going too far outside of that range can cause problems with the battery’s function, including draining it of power.",
"To answer this generally, heat can be thought of as energy. If something has lots of energy, the particles within it move fast. If it's cold, the particles are moving slowly. The same applies to batteries - the chemical reactions happen more slowly , meaning the battery charges more slowly."
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e5at6b | How does the mathematical data transfer over to colors when showing off the Mandelbrot zoom? | example: URL_0 | Technology | explainlikeimfive | {
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"Usually, the color in the Mandelbrot set corresponds to how many iterations of the Mandelbrot function it takes before the starting value leaves a closed disk centered at the origin (A radius of 2 will show you where the actual Mandelbrot set is, assuming you run infinitely many iterations on each point. Other values can be used to approximate the set though). So values which leave the disc after 5 iterations get one color, after 10 iterations get another color, etc. Which color goes with which number depends on the color space, and typically, you take the number of iterations modulo some number since values near the Mandelbrot set can take many, many iterations before they leave the disc. Since we can only run finitely many iterations, any starting point that hasn’t left the disc after some set number of iterations is usually colored black. This doesn’t mean that every black point is in the Mandelbrot set, it just means that the algorithm hasn’t proven that the point is *not* in the set."
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e5b6a0 | A vinyl record spins at a constant pace, but since it's circular, the needle is moving across more material at the start of the album. Does this mean they are recorded at different pitches throughout the album to compensate? | Technology | explainlikeimfive | {
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"Everyone is right here. But to answer the question more in depth... A master vinyl is etched using a much heavier etching head that has a tracking system to GO INWARDS at a constant rate. This is reflected In how the vinyl is played back except your needle follows the grooves and so is controlled by the grooves. The speed, 45 or 33 rpm, remains constant during master etching and final playback. Though technically you can (and do) master at lower speeds to improve quality. So yes the outer tracks move faster and therefore have higher \"bandwidth\" or fidelity (even though these are different terms, they both apply)",
"Geez, no one posted the Calvin and Hobbes that addresses this?!? Edit: here. URL_0",
"The outer bands have more bandwidth, but the recording device uses the same RPM notion as the player. Neither use the \"inches of groove past the needle\" measure.",
"The recording is done at the same speed as the playback so it sounds just fine, but as you get closer to the centre of the record, there's not as much vinyl track per second of music, so the fidelity does drop. That's why on a lot of records that have been mastered with some thought, the tracks with a brighter sound (more high frequency content) tend to be closer to the outer edge of the record, because it's the high frequencies that become less possible to reproduce as the \"inches of track per second of audio\" value drops, as it's naturally going to as you get further towards the middle of the record.",
"It is always recorded spinning at the same constant speed, the same as it is played back, so it never changes. But of course the further in it gets, the faster it gets to the center, but everything is at the same rate. Think of it like writing spiralled around a disk, except the words do not get stretched or compressed. Otherwise this would make it more complicated to record and playback which is unnecessary, because it would mean you would of course need the needle to change size and motor to slow increasingly as it moves further in, which of course not possible to do with the needle being a static unchanging object.",
"Related fact: video discs coped with this by having two modes: constant angular velocity and constant linear velocity. A CAV disc recorded one frame of video per rotation, regardless of where on the disc it was. This meant that you could skip from frame to frame just by moving over one track. This was great for special effects like freeze-frame, slow motion and also for random access, in video games and image archives. But it wasn't an efficient use of space: only 30 minute per side could be held. For movies, CLV was used where the data was packed as tightly as possible, and the number of frames per rotation was about 3 at the outer edge and 1 at the inner edge. More could be stored, but \"trick play\" was limited to chunky jumps and jittery freezes.",
"[Relevant ELIC]( URL_0 ) You may need to zoom in.",
"Everyone else is correct. Just one small addition: A side effect of this is that you have better sound quality at the edge of the record, as the \"resolution\" is better there.",
"Well, traditionally records were recorded right onto a spinning disk. Just because of the way geometry works, the tracks closer to the center are more compressed. If you were to somehow play the disk at a constant speed relative to the needle (surface speed), you'd notice the music would speed up closer to the center of the disk. However, since the recording and playback are done on disks of the same diameter spinning at the same speed, playback is perfectly 1:1 with the recording. While the inner tracks are technically more compressed and \"higher frequency\" from a linear perspective, it doesn't matter because playback is done the same way recording is. Same deal for tape; as you get closer to the end, the tape is moving faster because the take-up spool has a larger diameter. But since it was recorded this way, it plays back just fine. (though I think Phillips compact cassette is constant surface speed, as well as the various continuous-loop tapes like 8 track) I don't know if modern vinyl masters are created digitally, or by transferring digital audio to an actual spinning disk. Software could definitely generate a track pattern for a record, compensating for the different surface speeds, but I suspect it's just cheaper to use a real spinning disk."
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e5cdka | Why are there so many different types of wireless signals? | ELI5: Why are there so many different types of wireless signals? (WiFi, 2.4, 5, Bluetooth, 3g, 4g, 5g, LTE, Ect. I understand each serves a distinct purpose, but it seems like most could be standardized to transmit data into the latest technology like 5G. | Technology | explainlikeimfive | {
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"There are so many design considerations to be had when designing a wireless device. First of all, there are silly amount of wireless devices in existence today and the spectrum is limited. So you have to comply with laws and regulations so that your device doesn't interfere with other devices or people's health. Then you have to adhere to physical laws, like does the signal need to penetrate walls? What's the required range? Does it matter if rain attenuates the signal? Do you care if you transmit one message and then your battery dies? You also need to consider the bandwidth requirements and how many users are expected in a given area. Something like orthogonal frequency-division multiple access modulation seems a bit overkill when you're just connecting a controller to your game console. & #x200B; ...etc."
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e5ck00 | How do musical vinyls work? | Technology | explainlikeimfive | {
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"Sound waves are etched into a record. When being played a very fine needle runs along those etches and vibrates. Those vibrations are converted into an electric signal and amplified"
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e5d0vo | why some remote controls have IR light while others have an antenna instead of any IR led? Do antenna is meant for IR? Or difference between the 2 types? | Technology | explainlikeimfive | {
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"The antenna communicates using radio frequency signals, or RF. IR is used when great distance is not necessary, and line of sight is pretty much always possible, because it depends on it. For example if someone stands between you and the TV, your IR based TV remote will either not function at all or function not as well, because the IR signals from it have to be direct visible by the little IR decoder in the front of the TV. RF is used when either larger distance is needed, or the device you're controlling isn't directly visible, and might be obscured. That's why game console controllers tend to connect using Bluetooth or some variant of it, which is a radio technology, because you don't want to lose control of your game even for a moment if your knee gets in the way of the controller signal, as it could if IR was used. Yes, IR game controllers have existed in the past like [this example]( URL_0 ) released back in the day for the SNES."
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e5h5oc | Can nuclear waste be recycled? | I know the jist of what nuclear waste is I just want to know if its possible to recycle it and if so (optional) why it isnt being done and if there are any benefits besides the obvious which is it being good for the enviroment. | Technology | explainlikeimfive | {
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"Sure. ~96% of the mass of spent nuclear fuel is still the same uranium that was put into the reactor (though more depleted of ^(235)U, and some ^(236)U). Another ~1% is perfectly usable (as fuel) plutonium. And there's plenty of other useful things in there. Isotopes with uses in nuclear medicine, even (non-radioactive) valuable metals (such as the \"fission platinoids\" - ruthenium, rhodium, palladium - and silver). As for why it's not commonly done, the reprocessing \"industry\" (if you could call it that) was killed by presidential order, citing \"proliferation concerns\" (as if someone is going to break into a reprocessing plant on US soil, smuggle out the isotopes useful for making weapons, go through the rigamarole of enriching those isotopes so they can make one that won't fizzle, so on and so forth). That presidential order has been lifted, but since it was put into place in the first place, it's generally considered too risky to be commercially viable. France, on the other hand, being the heavily nuclear country it is, *does* reprocess their spent fuel (among many other intelligent decisions in designing a nuclear industry). So do China, Russia, India, the UK, and Pakistan.",
"It can be, but isn't usually done because the process of doing so can allow access to nuclear isotopes that could be used in nuclear weapons.",
"Lots of issues: 1. Radioactive waste is often embedded and mixed with other materials, so reprocessing would involve separating the radioactive material from the material it is embedded in. 2. Reprocessing waste is difficult and expensive. 3. It can only reduce, but not completely eliminate, waste meaning we still need a strategy for dealing with waste. The strategies for dealing with waste depend on the level of radioactivity in question, but are various forms of \"contain, cool, and bury.\" The more radioactive it is, the more we need to do those things."
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e5lwu8 | If my TV is already dolby vision compatible, why the device playing the video needs to be too ? | In short, I have a nvidia shield 2015. When I play dolby vision titles on netflix from the shield, they appear as 'HDR' only. I thought the device was supposed to send the video pixels to the TV untouched. | Technology | explainlikeimfive | {
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"That's like asking why you can't hook up a VHS player to a 4K UHD TV and have it appear as if it was footage shot and recorded in 4K, or why your old cassettes don't sound any better on your $4000 sound system than your car stereo and doesn't provide Dolby Surround. In order for a given audio or video feature to work, both the device transmitting the signal and the one producing the audio/video need to support that feature.",
"URL_0 > Netflix supports two different HDR streaming formats, Dolby Vision and HDR10. What do I need to stream with Dolby Vision or HDR10? A smart TV that supports either Dolby Vision or HDR10 and Netflix, connected to your device via an HDMI port that supports HDCP 2.2 or later (usually the HDMI 1 port). URL_2 > In October 2019, Nvidia unveiled two new Shield TV models. Both models use the Tegra X1+ system-on-chip, ship with Android 9.0 \"Pie\", support Dolby Atmos and Dolby Vision, and include an updated remote control, and a new \"AI-enhanced\" upscaling system that can upscale high-definition video to 4K resolution. URL_1 > The new SHIELD TV features Dolby Vision and AI upscaling. However, neither of these features are backwards-compatible with older SHIELD players. > **Due to this, the 2015 and 2017 SHIELD TV players will not receive Dolby Vision or the AI-enhanced upscaling via an update.**"
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e5nl2a | How ISPs control your internet speed | So I have unthrottled gigabit fiber internet and when the guy was setting it up, he literally just had to push a button to change it from 150 Mbps to gigabit. My assumption here is that there's some electronic throttling that happens at the customer's home, and that the speed of the data coming through the pipes otherwise is at max speed. It doesn't make sense given that fiber is fiber, coax is coax. Does this mean there's some local caching of your data when your speed is throttled? | Technology | explainlikeimfive | {
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"With cable + DSL modems there is a configuration file uploaded to the modem from the ISP during boot up that includes the details of your connection as well as your speed limits. The modem's firmware (software) limits your upload/download speeds by only allowing a certain throughput via the device. Just in case you were considering trying to modify that file, they have protections in place to prevent exactly that. Also a great way to get fined and have your service disconnected permanently. For fiber services typically your fiber optic is plugged directly into a switch on the ISP side bypassing the Cable + DSL gear that turns fiber signals into phone or coax signals. By changing the port speed they can change your much bandwidth you get. (10, 100, 1000mb/s) This physically rate limits how much bandwidth can run over the wire by changing the communication protocol. This is the poor mans way of doing it. For more granular control they can use a QoS port policing rule that restricts how much bandwidth you get per port. The software on the switch monitors your bandwidth usage and drops traffic to make sure you don't exceed your limits. They can set prioritization, bursting, and rate limits all using the QoS technology on the switch. We use the exact same technologies in industry to restrict or optimize traffic flows on switches both in and out of the datacenter. EDIT: For the record what limits your maximum potential internet speed isn't the cable in your house so much as the cable coming into your district. All of the homes in your neighborhood tie into a local node that in turn has an uplink cable back to the ISP. This uplink cable has a fixed speed limit (by hardware) and is the total amount of bandwidth available for your neighborhood. So if that cable has a 10gb/s max, and each of 100 houses has a 1gb/s connection, then theoretically speaking 10 users could max out the bandwidth for the whole neighborhood. This is called over-subscription and is done deliberately to reduce ISP costs. The simple reality is that at any given time most people in the neighborhood aren't using any bandwidth at all, so this works."
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e5vi6o | why news channels can broadcast events from miles away in excellent quality with no lag, while I struggle to have a decent Skype conversation without connection issues | Technology | explainlikeimfive | {
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"TV news channels are allowed to broadcast on TV air waves (just like airplanes can fly through the sky really fast). Your Skype conversation needs to fight with traffic of all the other home internet users (just like driving on the freeway at rush hour). They are just fundamentally different modes of data transportation.",
"Your best bet would be to get a better connection, if you have the option. Thing is, news agencies might use dedicated networks - Reuters does, as far as I know. This means that a whole country- or worldwide mesh of connected hardware is dedicated to that kind of traffic. Don't forget that it might just be the service that sucks. Try to see if Hangouts/Discord/Whatsapp calls also lag, and if not, it's just Skype that is at fault.",
"News links are generally one way. A high bandwidth video and audio from the reporter in the field back to the studio and a low bandwidth telephone connection for the news anchor to ask questions to the reporter. Many news crews still use microwave transmitters back to the studio for remote links. Newer technology exists that uses four 4g lte card links for the similar connections. Fits in a backpack instead of a white van. Your home internet connection is probably 10mbs down, 1mbs up so there is delay between the question and answer. Plus, tv hardware is designed for high bandwidth, high quality connections. Skype and other services are designed to not use up much bandwidth between you and where ever the server resides, so video quality inevitably suffers."
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e5vsa6 | How are sounds in video games and movies made from complete scratch? | Technology | explainlikeimfive | {
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"Many of them will be pre-recorded and just saved into a pack that can be dragged and dropped in. The rest will be Foley sound which is just recording something that sounds like the action in a sound proof room. Off the top of my head the only one I can think of was snapping a piece of celery for a bone breaking. They're normally layered with many other sounds to create the best sound for the film"
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e5w8y2 | What do hackers actually and how does hacking works, | Technology | explainlikeimfive | {
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"To simplify - they abuse a vulnerability in a system. Let's say that your house has a finicky door handle that if you turn it counter clockwise it will always open - wether or not it is locked Hackers take that vulnerability and abuse it so they can get what they want. This also extends to people (social engineering). Most of the time they are attacking code base in an unusual or unexpected way that results in glitches / bugs that may or may not be fruitful in their endeavours",
"It's basically testing out server security. Poking around to see if it can be breached and taken down. Hackers get hired by companies to test this. They look for loopholes in the code, use programs to see if they can bypass a firewall or other security features of a server, in order for the company to improve their cyber security. Those are the good \"ethical\" Hackers. On the other side, Hackers who bring down or attack servers for their personal gain are called \"unethical\" ones. There is way more to it of course, but this is the gist what hacking actually does."
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e5xp7a | Why is there whenever you take a photo with your phone of a PC/Laptop screen a rainbow effect in the photo? | Technology | explainlikeimfive | {
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"Your screen is made of a grid of pixels each made of red, green and blue subcomponents. Your camera is basically the same way, but since the two are independent of each other and there are perspective issues, the two grids of pixels are out of alignment. Each camera pixel is prone to seeing the edges of the monitor's red/green/blue sub-pixels causing weird colour effects. TV ads for cellphones always say \"Screen images simulated\" for a reason, and not just because they want their phone to behave perfectly. It also has to look perfect. The technical term for this phenomenon is called Moiré and the pixel thing is just making it worse.",
"Depending on the screen type, usually each pixel is one colour. For example, a pixel can either be red, green or blue, or enable all three of those colours to produce white, and some screens completely turn off the pixel to produce black. Your camera lens is most likely picking up the individual colours of the pixels and somewhat blurring them, which is why photos of a display have a rainbow effect. Maybe someone can explain it better but hope that helped :)"
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e5yb4d | how do flash grenades work | Technology | explainlikeimfive | {
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"text": [
"Instead of being filled with high explosives, like a normal grenade, stun grenades (flash bangs) are filled with a pyrotechnic charge, usually made of magnesium (which burns hot and bright) mixed with an oxidizer (to make it burn faster.) The casing has holes in it to help keep it from rupturing so you don't get shrapnel. The result is that you get a huge flash of light with a big bang, but no shrapnel and limited damage so that things and people in the room won't be badly injured/destroyed (although it's not perfect - injuries and hearing damage happen, and they can light stuff on fire.) Edit: TL;DR it's a firework pretending to be a grenade."
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e5zv7j | How does a number get traced? | Technology | explainlikeimfive | {
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"text": [
"You call the phone company and ask them. Generally it helps if you have a warrant. But all modern phone calls are handled digitally and the phone company has records of when Number A calls Number B, how long, etc. That's how they bill people and make money. There are outliers that make it more complicated (VOIP, calls from within PBX networks, etc) but the old days of \"stay on the line for 3 minutes so we can trace it\" are long gone."
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e63f68 | How does frequency on a CPU impact performance? I.e. if I overclock a 2Ghz CPU to 4Ghz, is it +100% performance? | Technology | explainlikeimfive | {
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"Increasing the clock speed on a CPU increased the frequency with which it can process tasks. If you double its clock speed, that means it can send data through the bus twice as frequently. This, however, does not translate to twice the overall speed of the computer. There are a number of other links to the chain that would bottleneck things (speed of your RAM, volume of RAM, speed of the other components within (GPU, SSD, etc), but in theory a task that relies 100% on the processing power of the CPU could be performed in half the time (think of highly complex mathematical calculations). BUT! Increasing the clock speed is not without consequence. Faster clock speeds generate more heat, and without effectively dissipating that heat (with a more efficient heat sink/fan configuration, or liquid cooling) that resultant heat will slow the machine back down. (hot wires have higher electrical resistance). If the components get TOO hot they'll actually stop working altogether, as the resistance gets too high for the circuit's integrity to be maintained (or it could result in physically damaging/destroying internal components like resistors, capacitors, melting solder points, etc.) Generally overclocking your CPU is limited to a 5-15% increase, and is only done by enthusiasts who have invested in good heat management (a high conductive heatsink with push/pull fan setup, or liquid cooling.) In short: heat is the enemy of performance in a computer, and increased clock speed, while results in increased performance, also results in increased heat which is bad. So it's a balancing act to get the most bang for your buck without shortening the life-span of the components themselves. EDIT: I accidentally a word",
"No it’s not a linear increase like that. Personally though I find clock speed to be the best indicator of performance apart from maybe benchmarks. Like others have said, a faster clock speed means that the CPU can process more instructions in less time. There are other factors though like cache size (the more data you can hold in cache the less fetches you need to make from main memory - and fetches are very costly in terms of performance). Another factor could be the instruction set being used, essentially you get simple instructions such as ADD which takes the values in 2 different registers, adds them and stores the result in a third register. We’re getting a bit outside my area of expertise now but let’s say the ADD instruction can be completed in a single clock cycle. Now lets imagine an instruction set which contains a multiply instruction which can complete in 2 clock cycles. And imagine we want to multiply 8x7. How many ADD instructions does the first simple set need? Maybe 7. How many MUL instructions does the more complex set need? Let’s say 1. In these examples, we could say that a CPU with lower clock speed using the more complex instruction set might actually have better performance. To be clear, I’m not arguing that complex instruction sets are inherently superior, only in this made up example I’ve given. In summary, it’s a balancing act, but for consumers I’d generally state that clock speed is a good indicator of performance."
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e63lm3 | Why do movie cams (the ones recorded in theatres and put on torrent sites) seem like they're always small and blurry low-quality video files, even though camcorders have improved massively in the last decade? | Technology | explainlikeimfive | {
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"Taking a fancy schmancy camcorder into a theater is a real easy way to get caught and ejected (and possibly arrested). As such, those people who bootleg movies do so in as discreet a way as possible. Most of the time that means recording with a small inconspicuous handheld device, (most often a phone). Phones can take some pretty good video, BUT generally they require good lighting to do so. If you've ever been in a movie theater you probably know that \"good lighting\" is not high on the list of \"things found in a movie theater\". So the video as a result is lower resolution. Additionally, the small microphones in a phone can't accurately capture and reproduce the 8.1 Dobly Surround Sound experience, so the audio is pretty flat and crappy on playback by comparison to the source.",
"Because it is illegal to capture the movie and pirates tend to use very small cameras to not get caught and a small camera has worse video quality. Also why should any pirate buy an overly expensive camera? It is not like they are making money with it if they are uploading it to torrent.",
"What the other people said...plus the fact that the video is likely compressed to save space. Turns out when you are giving away a product for free, you probably arent shelling out on hosting costs."
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e66env | On Coursera, how does the text written by a person facing the camera appear correct? | I'm taking a Coursera class, and the videos show an instructor facing the camera while talking. He writes on the "screen", using his right hand, and the notes appear correctly (also facing me) as if drawn on a glass window between us. How is this accomplished without him actually writing backwards a la Da Vinci? He is clearly writing on something board-sized. | Technology | explainlikeimfive | {
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"The presenter is writing on a piece of glass with the camera looking through, so the raw video will have the text reversed. They just flip/reverse the clip and like magic everything is the right way round. Think of it like taking a selfie using a mirror. The image in your phone is backwards, but if you look at the image using the mirror it is all good."
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e66uu8 | How do animators sync up their characters talking with audio? | How do they make their character's mouths move at just the right speed? Is there a lot of overshooting/undershooting and then having to go back and fix the frames? Or is there some general rule of thumb (x amount of frames to each second of audio)? | Technology | explainlikeimfive | {
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"text": [
"actual animator here: experience and timing. if you do as others in this thread say and just plug in whatever lip shape happens for whatever sound you get terribly ugly uncanny valley lip sync. It looks terrible and fucking creepy, it looks unprofessional and slapped-on. What mouth shape you think there'd be is not actually what would be there. The shape you'd use to make one sound in one instance, is not the same elsewhere. there's like 4 different ways to do an \"eeeeee\" noise, that changes in context to the dialogue it's in. An animator's talent lies in their ability to see how people actually move, not how they think they move, but also vice versa, so by compounding this experience and observation we animate characters- including dialogue- to look the best it can not just realistically but have it \"feel\" good as well. but the vast majority is just a large amount of eyeballing it with expertise and experience.",
"Back in the analog days they would write a chart of what sounds were being made each 1/24th (or 1/12th) of a second on the soundtrack. Occasionally they would also film the voice actors while recording, and that can be used as a reference. Nowadays computers make it easier. When I animate dialogue in TVPaint, I can import the audio file into the timeline, and when I scrub frame-by-frame, the program plays just that frame’s snippet of audio and I can usually tell what sound is being made.",
"Usually they would record the audio in advance then synchronize the animation to that voice over. With computers these days they can produce some reference positions for the mouth and lip movements for given language sounds, like a “p” sound is going to require closing the lips, etc. The computer then runs a program that recognizes those language sounds (perhaps also referencing a script) and can animate the movement of the face between those points automatically. On big budget productions they would then go in and tweak those animations to perfection."
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e67o7i | Why does regular Wikipedia run smooth as butter, but "fandom" Wikipedias and the like make every device I've ever used them on chug like nobody's business or straight up crash the browser? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Because regular Wikipedia is 99.9% text and a few pictures, whereas \"fandom\" Wiki pages oftentimes run special scripts to change your mouse cursor or add flashier graphics. They usually also feature multiple advertisements. All of the extra scripting and ads use more resources.",
"Because unlike regular Wikipedia, the Fandom wikis are loaded with tons of ads and Javascripts meant for loading more ads and tracking behaviors onto your browser. You can easily open your browser debug window and see all the crap that gets downloaded when loading a single page, and also see all the script tags embedded in the HTML of every page loaded. The result is that your browser has to run a ton of JavaScript and download a lot of assets from each page, running not particularly optimized code whose purpose is to download ads and autoplay video ads while phoning home to their advertising company all the info they have on you via your various cookies and IP address.",
"Um because Wikipedia spends at least hundreds of thousands and probably millions of dollars on it's hardware, and fandom wikis run by people in their basement....don't",
"Web dev here, the primary reason is their infrastructure. ELI5: Wikipedia deliver their website to you via a modern fighter jet. Fandom wikis deliver you their website via partially lame donkey."
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e6anbw | What do wifi mesh systems do and do they actually work? | Technology | explainlikeimfive | {
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"Yes. Let’s take a classic analogy. You want to hear music. You have a speaker in one room that plays music. In other rooms the sound is a little muffled, outside you strain to hear it. In the garage you can hear anything. You get a bright idea, you put a speaker in every room. Now the walls and doors and other interference don’t cause a problem. That’s a mesh network. It just allows you to bypass impediments to the signal so you can get good throughout everywhere. Just like listening to music.",
"Others explain what they are well - but the important thing is, in older 'consumer' grade equipment, once you connect to wifi, you stay attached to that point...If there was a wifi extender/repeater in range with better signal, it wouldn't matter as you are still connected to the older, crappier signal. In a mesh system, all points try to communicate with all other points to assess 'Who has the best signal to this node' - then they actively hand off the client to the best point. This is how cel phone towers work also - constantly switching to the best available signal."
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e6d2ho | how do rechargeable batteries work? | Technology | explainlikeimfive | {
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"Batteries are chemical reactions. Some chemical reactions are one way. Once the chemicals have reacted they cant revert to their previous form. Some reactions move both ways. Take two chemicals and put them together and they react and release energy. Then put energy into them and the chemicals split apart into their previous form. Non-rechargeable batteries, such as alkaline, are a one way reaction. Rechargeable batteries, such as lithium ion, nickel metal hydride or lead acid, are a two way reaction.",
"This video does a pretty good job of explaining and showing what's going on: [ URL_0 ]( URL_0 ) In the simplest of terms, it's basically a chemical reaction that creates an electric current, but that when you introduce a current that runs in the opposite way, reverses the reaction and allows it to start over again."
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e6e7no | why if I factory-reset my phone it wont be as fast as the day I bought it? | Technology | explainlikeimfive | {
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"All operating systems (regardless of device) that receive regular updates will run slower. This is primarily because those updates either address security concerns or stability issues. These are either resolved by adding additional checks or additional processes to the system, or in some cases deliberately slowing the system down. Apple has previously admitted to deliberately slowing down certain older models to protect aging batteries."
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e6kf71 | How do radio stations measure how many listeners they have? Does the strength of the signal they send out weaken when more listeners tune in and they measure it? | Technology | explainlikeimfive | {
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"There is no electronic means of measuring it. No the signal does not weaken as more listeners tune in. It's likely done through surveys \"What radio station do you listen to?\" and listener feedback. Those giveaways where they ask for caller 9? Yeah, that also tells them how many people might be listening. If they struggle to get 9 callers, then that's a bad sign."
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e6lsnc | How does picture format conversion work? Eg. PNG to JPG | Technology | explainlikeimfive | {
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"It's basically the same as translating languages. A program knows how to read and save both formats and remakes the original in the other format."
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e6ncqj | What is the Internet of Things? | Technology | explainlikeimfive | {
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"Typically, people only think of computers and phones being able to connect to the internet. But in the past few years many other devices started being able to connect. First it was TVs, but it's expanded to appliances like refrigerators, washers, dryers, cars, and even light switches! All of these additional 'things' that people don't automatically associate with connecting to the internet now have that capability.",
"Basically it’s all the smart devices that you can hook up to your WiFi at home. You could get a smart thermostat, so when you get 2 blocks from home, your phone will turn up the heat. Or a garage opener that connects to your phone, and when it opens the door when you drive within range. Or something like Alexa speakers, where you can just say something like “turn off the kitchen lights”, and it’ll happen. They’re a great new convenience factor to daily life, but they’re also additional security risks and privacy breaches. Alexa speakers are constantly listening for you to call them and will periodically mishear what you say. They also send small recordings to Amazon employees so they can double check that it’s working correctly, and you can’t stop it from doing that. As you can imagine, it’s an interesting and crazy new field!",
"The \"internet of things\" is sort of a broad category of internet connected devices that don't generally fall under the category of general purpose computers. Which would include PCs, smartphones, tablets, game consoles, etc. Typically they're meant to cover single purpose, consumer grade, smart appliances that can be remotely controlled via, or access data from, the internet as opposed to just local area networks like Bluetooth and WiFi. Devices that fall into this category would be personal assistants (Google Home), smart TVs, streaming sticks, Nest thermostats, security cameras that utilize cloud storage, BD-Live enabled Bluray players, smart door locks, security systems, certain robot vacuum cleaners, smart lighting, smart kitchen appliances, certain smartwatches, etc. The problem with the Internet of Things is that a lot of these devices don't receive security updates for long, if at all. Making them a potential security vulnerabilities for networks, since they can be used as a vector to get access to other devices on the same network.",
"Devices being made to connect to the internet. E.i. your TV, refrigerator and other things that usually don't have the ability to send and receive info over a network"
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e6qh8x | with bushfires moving across much of Australian right now, how do fire fighters fight fires that seem beyond human control? | Technology | explainlikeimfive | {
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"They can do things like dig break ditches. They basically take a wide enough line of the vegitation out between the fire and the unburnt brush so the fire cant spread further or to slow it down enough so evac is easier.",
"It depends on the fire and how quickly it is moving. There are some offensive and defensive methods to fighting fires. Offensively, they can attack the fire directly. They do this by spraying/dropping water and other things to put the fire out at its source. Defensively, they can do a few things to try and prevent the fire from spreading. One way to do this is to cut fire lines. You basically clear a wide path that the fire is heading towards. If you cut down the trees, bushes, etc the fire can’t spread over this cleared area. Another way is controlled burns. If you set a small fire to burn up the combustible materials before the main force of the fire gets there, the fire won’t be able to continue in that path. Smaller fires are much easier to control than large ones. Many sides of the fire they let burn on their own. The first objective is saving lives and property. So if they can focus their efforts on a small neighborhood in the fires path, they will devote more resources to that area than a place with nobody living there."
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e6qprr | Why are "feather dusters“ still so widespread and how are they superior to microfiber cloths? | Technology | explainlikeimfive | {
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"text": [
"They are good at removing dust from very irregular surfaces (they get in between bits), and at not disturbing delicate items."
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e6tk95 | Can I make my own domain or do I have to buy it from sites like godaddy? | Technology | explainlikeimfive | {
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"text": [
"To make a domain you have to be registrar, which means you are approved to add Domains to the DNS and lease them out to people and companies. Sites like GoDaddy are a registrar. Yes you could theoretically do that but... The cost and process of becoming a registrar would be so enormous that it wouldn't be worth it."
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e704kt | How does a nuclear reactor work. | Technology | explainlikeimfive | {
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"The basic principle behind a coal burning boiler and a nuclear reactor are similar. The main difference is the heat source. In a coal burning boiler, as the name suggests, a coal burning fire is used to heat water to steam, and that steam is used to turn turbines to generate electricity. This of course requires a constant replenishing of the burning coal, and creates all manner of exhaust from the burning fire. A nuclear reactor replaces that coal burning fire with fuel elements and control rods. This setup produces and controls the release of energy from splitting the atoms of uranium. Inside the reactor core, urnaium-235 isotopes fission, or split, producing a lot of heat in a continuous process called a chain reaction. This reaction is controlled with water or graphite (the purpose of the control rods) to ensure the reaction doesn't get out of control and cause a literal melt down. That heat produced is what's used to, just like a coal burning generator, boil water to make steam and use the steam to move turbines. URL_1 URL_0 The primary differences are A: the immense increase in efficiency, in terms of how much water can be constantly boiled, and B: the waste product. Instead of emissions and exhausts, you have irradiated water from the core that needs to be properly disposed of. But you also get a nifty byproduct of depleted uranium, which makes for some pretty sweet ammunition."
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e70bcs | How can a single coaxial cable provide HDMI and an internet connection with minimal data loss? | Ok, set the WABAC machine for, say 20 years ago. I'm working at Best Buy selling electronics and, being the diligent and curious person that I was, I was reading about the various ways of connecting your game consoles, DVD players, etc. to your TV. Back then, in the pre-HDMI days, there were basically 4 options available: * RF Coax (worst) * Composite / RCA (standard) * S-Video * Component (best) And the explanations for what made each method good or bad was pretty simple: **RF Coax** bundled all the information (video and audio) into one signal that had to be translated by your TV. This translation had to happen very quickly could sometimes create "errors" so you ended up with a pretty noisy / low quality picture. **Composite** separated out the audio from the video, so that was one (well 2 for stereo) less thing for your TV to translate. However it still had to break out all the video information from one line, so there was still a pretty low-quality image. **S-Video** took things a step further by separating out brightness and color information, so there was even less translation required, giving a much better image than composite. **Component** was the best of the bunch because the individual red, green, and blue color data was each sent on its own line. Eventually in like 2003 or so, HDMI came out and that became the "gold standard" for video. But here's my question: How is it that cable companies can use a coax cable to transmit high-definition video *and* a high-speed internet connection using basically the same cable that provided the absolute *worst* possible image for, say, video game console? What's the difference? | Technology | explainlikeimfive | {
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"Because it wasn't the coax itself that was causing the low video quality. Coax by itself is extremely wide bandwidth (only fiber optics have higher bandwidth). The relatively low video quality for RF was because the signals being sent down the coax were the exact same type of signals (6 Mhz wide analogue) that would have been transmitted over the air by a TV station with it's limited broadcast spectrum. If you look at the inner workings of a TV station these days, almost everything is uncompressed digital audio/video over coax. Even 4K/8K video."
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e70xl7 | How do websites know a phone number is Google Voice? | I like to use my GV to avoid spam to my real mobile number but some websites can detect that it's not tied to a mobile carrier and won't allow it. How do they know? | Technology | explainlikeimfive | {
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"Different carriers purchase a range of phone exchanges to use and assign to subscribers. I’m sure Google is just doing the same thing and those websites are able to determine this by validating the number. You can do a reverse lookup on a phone number to find out the carrier using public databases.",
"There are databases you can query to see what carrier a phone number belongs to. First is the LERG (local exchange routing guide). The LERG will tell you the carrier that block of numbers is assigned to. But if a number has been ported to a different carrier, you have to query the LNP (local number portability) database. That tells you where the number has been moved to (AT & T, Tmobile, Google Voice)."
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e721no | why can’t we just insert video games into the console and start playing anymore? | Technology | explainlikeimfive | {
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"Games these days are much, much bigger, with gigabytes of textures, sound and so on. They are simply too big to run from temporary memory as they used to. They install because data access is much faster from a hard drive than an optical disc. You only need the disc in the drive to prove you own the disc. Downloaded games work just fine without the disc.",
"Games are bigger now. Installing from disk prevents you having to constantly be reading data from the disk while playing, which would dramatically hurt performance. You must continue to use the disk after installation as a form of DRM. You can't just give the disk to someone else for free and continue to play.",
"Playing off the disk would be too slow. Since a bluray can hold like 50 GB and it reads at like 27MB/s. So you copy to disk first where reads can reach 100MB/s or faster. Then you need to download stuff or patch because the disks are made weeks if not months before the game is actually ready since it takes a while to manufacture, distribute, and put on shelves. And all people are doing these days are just rushing things out the door asap since competition is high.",
"It's important to note that video game consoles didn't used to have internet. This means that when a video game was shipped to the store shelves, it HAD to be finished and quality checked BEFORE shipping. Now with internet access, video game developers have the luxury of setting a release deadline and shipping games before the product is actually finished. The disc will include 99% of the game, but developers can finish the game after the disc is manufactured, before the game is delivered to the customer, then require the customer to download updates on release day."
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e728aa | How do smart screens work with skin but nothing else? | Technology | explainlikeimfive | {
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"Not quite accurate. They also work with conductive synthetic rubber, or other items that can hold a tiny electric charge. Basically, they detect *capacitance.*",
"The type of touchscreen you're referring to is a *capacitive* touchscreen. These touchscreens work on a principle of electronics called capacitance. This is the ability of something to store an electical charge. The touchscreen is coated in a transparent coating that is conductive (it can pass electricity). When you bring your finger close enough to the touchscreen (your finger doesn't actually have to touch on some devices, as capacitance does not rely on contact) it causes the capacitance of the material to change in that specific spot. That thin layer of coating combined with anything conductive that comes close to it forms a capacitor. Think of a capacitor as a tank of water. A tank can store, gain, or release water at will. You could measure the size of the tank of water by filling it up to capacity, then draining it again and measuring how much comes out. The capacitor works essentially the same way, but with electricity. In electronics, all you need to form a capacitor is two sheets of something conductive and a thin gap made up of something that isn't conductive. In the case of the screen, one side of the capacitor is the coating and the other side is your finger. The coating is laid out in a pattern on the screen, so instead of one large surface coated in it, there are lots of little spots. Due to the way that capacitors work, by putting your finger on the screen, you are making lots of little capacitors. However, they are all linked on one side because your finger is one piece. Using this, your phone can figure out when and where your finger is on the screen by testing any two points for capacitance. If they show capacitance, than that means that your finger is on both of the points. However, if your finger is only on one of the points, it would not show capacitance because there is not a complete circuit. However, since the fundamental design of the capacitive touchscreen relies on whatever touches it being at least slightly conductive, it won't work with anything that isn't.",
"Screens work with anything conductive. This is why you can get touchscreen gloves - they have metal fibres in the finger tips. You can also get styluses that work with touch screens. You could use a metal pen or paperclip, anything conductive."
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e74aax | Why is functional programming said to be better for multithreading than object oriented programming? | Technology | explainlikeimfive | {
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"It's all about data immutability and, more generally, managing state. Functional languages, in general, embrace and even enforce data immutability. You can't change your data, which means other threads can't change the data, which means you can't have conflicts or data corruption due to multithreading. With OO languages you can do the same exact thing by keeping your data immutable, but by tradition OO languages don't treat data immutability as the default. It's often easier to make mutable state data than it is to make your data immutable. This leads to situations where you have to worry about the same pieces of data being modified simultaneously on multiple threads, which means you need locks. Locks slow down performance and can lead to other problems as well (deadlocks, lock contention, etc) Multi-threaded programming is a bigger and deeper topic than most people like to acknowledge. Getting it right is extremely difficult. Making data immutable by default seems like a real small thing, but it's one less thing for a programmer to worry about."
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e74u9c | What is an API? | My current understanding of it is, its like a bunch of code translated into a "language" that is understood by an application or software , so it serves as a translator between a programmer and the app am I understanding it right? | Technology | explainlikeimfive | {
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"Everyone's talking about it from a computer programming perspective, but it's easier for an ELI5 post to think of it as a real-world example. I'm going to assume you're not an automobile designer or mechanic. (Sorry if you are. Just go with it.) But you can still learn to drive a car. You don't need to know how the engine is designed, what kind of metal it uses or where it was mined, what the chemical structure of the gasoline is, how it's refined, etc. All you need to know is that when you push the pedal, the car goes forward. When you turn the wheel, it moves a certain direction. This is called \"abstraction.\" The really complicated stuff, requiring deep expertise and knowledge about how cars are made, is \"hidden\" behind a set of very simple buttons and levers so that you can make the car do stuff without understanding how it does it. This layer of simple control in front of something very complicated is called an \"interface.\" Writing software works the same way. There is nobody on a software team who understands how every line of code works. People write their own parts of a big project, just like the engine guy in a car designed the engine, the refinery guys made the gasoline, the electrical guys wired up the dashboard, etc. But they all then wrap their stuff in an interface, with a set of instructions that say \"if you push the pedal, the car goes forward.\" In software, we call that an \"API.\" It's the interface layer between my code and yours. You don't need to know how my code does what it does. You just need to know that if you tell it to do something on this list of things, it will do them. Then your code can talk to my code, and together we can do a more powerful thing, without us ever having to see each other's actual code or even understand how it works.",
"You are making good assumptions yes. API means 'Application Programming Interface'. If you'd like to understand it at an EL15 level: Think of the connections on the back your TV. There are inputs for your cable, for your game system or VCR. And API is like a panel on the back of your software that lets other software connect and talk to it. The reason you want this is so that you can focus on what you are good at, and let your software talk to other programs that might be better at what they do. I might have the best weather data program, but not have any skills making a good User Interface for it.... enter Mr. Design who is very good at this, but is not strong at collecting data. Now his program and my program talk to each other using language they both understand. The result is good data in a good looking program. APIs are usually pretty invisible to us, but are in use everywhere in many applications.",
"From a software standpoint here... E.g. if you pull a lever out pops a cake. You don't care how, but it gave you a cake. And that's what you really care about in the end. The cake. From a software perspective it's essentially the same thing, but with code. The work has been done already to get you what you want. You just have to use it.",
"Imagine I had a pile of shapes. Squares, circles, triangles, etc. And suppose I want to be able to share my shapes with a lot of people. If someone needs a certain kind of shape, they can take one. And if they want to give me a shape, they can put it on the pile. This is well and good, but if my pile of shapes is kinda large, and has a lot of attention on it, it could get kind of messy. If someone just wanted a very specific octagon, for example, they'd have to tear through the whole pile looking for it, possibly messing up things they shouldn't be touching. Or they could take way more shapes than they should fairly have. And if I let people just leave whatever they want in my pile, I might end up collecting a lot of junk I didn't even want, things that might not be shapes at all, or might be put in my pile to hurt me somehow. So, I could elect to devise some sort of magic wall to put in front of my pile. This wall has a bunch of buttons and holes of very specific shapes. If someone wants to give me something to put on my pile, they have to make sure it fits in one of the shaped holes, or else it won't go in. And if they want something out, they have to press one of the buttons, which will only dispense a very specific shape. This way, I can restrict access to my pile in such a way that I only get things in that I want, and people can only take things that I want them to be able to take. An API is that kind of magic wall. It exposes a very specific set of things you're allowed to do, and gives you predictable results back when you do those things.",
"The acronym API (Application Programming Interface) actually explains it fairly well, just not well for ELI5. An API is interface between two services. It is a defined set of end points on a web server that accept certain input and will return certain output. They are used to pass information from one service to another, such as a website login. When you login to a website, you give them a username and password and the API will return back whether or not your login attempt was successful."
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e74z4o | How do Christmas lights flash individual bulbs? | With most Christmas lights, they have a line of LED's. How do they light particular LED's individually? | Technology | explainlikeimfive | {
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"text": [
"Many are done as an arangement of 3 strings. If you look closely you can see three wires on many strings or icicle lights. If you really look closely, there's never a need for the entire string to be off and a individual bulb lit. You can get away with controlling 33% of the string at a time for it to look random. It will iluminate each string independantly and it will look like every bulb is independantly flashing but in reality, every third bulb is iluminating at the same time. Sometimes they switch up the order so its not uniformly every third connected for randomness. Some new light strings have a tiny IC on every light which is really interesting. Power, ground and data is shared for all lights and every single bulb understands a giant string of pulsed numbers and what ID it is and what colour and brightness it should be at. This happens every milisecond or quicker. Believe it or not, these are actually cheaper since the entire bulb and silicon processing core is integrated and produced in the billions without manual labor."
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e77h94 | Why doesn’t “Alexa” respond when it is summoned on TV? | Technology | explainlikeimfive | {
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"text": [
"The show or ad has a buried frequency in it, which, when the Alexa hears it, it knows not to trigger.",
"Mine goes off all the time from the TV. I'll tell you a funny story. I have ties to QVC and when last year's TSV was an Echo. The host would order pizza as a demo live on the air. Over 300 viewers called QVC to complain because Domino's was showing up at their house because their echo was listening to the TV and ordering pizza for real. They had to stop doing the demo 1/2 through the day because of complaints. Dead true! But for me, I had to change our wake word to \"Echo\" for the show 5 we have in the living room because every commercial would set off Alexa."
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e7dnow | I talk about ADHD in person but never search about it online. A Google Play Ad triggered by a game from the app store is about ADHD. How do they do make that happen? | Technology | explainlikeimfive | {
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"At all times your phones microphone is listening. It hears buzz or trigger words and googles ad sence algorithim will play ads based on that.",
"Well, the whole premise of your question is based on the assumption that your question about ADHD causes the add you saw about ADHD. But that is really only one part of the equation. So two questions for you: 1. How many conversations have you had about products, sports, travel, cooking, videos games, TV shows, movies, politics, science, psychology, fashion, etc. and did NOT immediately see an ad about that topic? If you were to actually track your conversation, it’d likely be in the hundreds or thousands. 2. Would you have noticed the ad about ADHD the day before you had this conversation with your friend? After reading this post, take a day to consciously notice all the ads you run into every day - on TV, in magazines, online, on the bus driving by, etc. For the VAST majority of these ads, they are just in the background and you barely even notice them. But if you just spent an hour talking to your friends about how much you like the new Honda styling, you’re much more likely to notice the commercial selling Hondas. Last thing to point out - I’d argue that people are far more predictable than we like to admit. The game you were playing/downloading probably gave away a ton of information to google just based on the fact that you were playing/downloading it. For example (and this is just an example, so please don’t take it too literally), people that suffer from ADHD may be more likely to play/download some particular games from the App Store because it gives them something to focus on when they get easily bored. It may also give Google more demographic information about you then you realized. My point is, Google can get way more information from us just based on browsing/download habits then we even realize, without listening to our conversations."
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e7eqlt | How do historians and archaeologists comfirm that every ancient documents that they read are real? | You know that in the ancient times there is no digital stuffs to verify that it is really happening, they really say that, etc. So it is very possible that some historic writings are manipulated. Like there is a saying: history is written by the winners. Then how do historians can know that all the ancient writings they found are legit and not manipulated? | Technology | explainlikeimfive | {
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"1. That quote is something of a joke among historians. “The winners” are rarely willing or able to get rid of every piece of evidence that contradicts their narrative. 2. Historians don’t just take the documents they find at face value. Every piece of evidence is examined in the context of other pieces to determine what it means.",
"Interpreting sources really isn't *that* different whether you're talking about an ancient document or a modern one. The only difference with the ancient stuff is it tends to be a lot harder. Let's say you discovered some ancient tablets talking about a king's achievements. Here are some questions you might ask. What do other sources say about this king? Is it consistent or not? What is the archaeological evidence? If the document says the king built such-and-such, is there evidence of it? Why was the document written? Was it to commemorate the king's achievements? To damn him for his failures? To provide useful diplomatic information for another ruler? To tax his people? That will tell you something about what it's likely to hide, exaggerate or distort. What sort of document is it? Many texts follow a similar pattern and this can help you judge what to trust and what not to. Now all that can be *really* hard for ancient documents simply because there is so little surviving evidence. There are cases where we don't know if ancient rulers who are mentioned were real or mythical (or some combination of the two). Or take the case of the Hanging Gardens of Babylon. One of the wonders of the world, according to Greek writers. Except that no Babylonian sources mention them, and no archaeological evidence has been found. So were they a myth or did they exist? And if they did exist what were they?",
"Often they are fooled, however there are some ways round the problem firstly it is context where was the item found, if you dig it up from an ancient tomb you know the writing is genuine. Next there are references made in the writing which cross match to other documents, of course if those documents are also forged then this can be a major issue (Mark Hofmann forged a whole bunch of stuff on the Mormons, but his forgeries were used to check other forgeries so he got away for years) Finally you can chemically or physically check the ink and paper they are written on, but inks can be faked and original paper can be used to create forgeries taken out of old books.",
"We don't need to imagine ancient documents for this, we can talk about more recent ones. I am a historian who uses lots of documents from the 1940s and 1950s to write history. How do I know that the documents aren't all forged, or created by liars, or biased in some way to throw me off? On forgery, we can look into provenance. Where is the document from? Who claims to have created it, found it, stored it? Are they reputable? Does the document look like it comes from where it claims it does? These are questions we can ask, though it only really comes up if we see something very suspicious — something that doesn't \"fit\" with the rest of the other things we know. The only place I've really seen outright forged documents are relating to UFOs and things like that, on the Internet — people will post \"authentic\" documents that are in a typeface that wasn't used in the 1940s, for example, and can never cite any kind of verifiable source for them. That's not to say that it couldn't happen in other places (like archives) — it occasionally does, but it seems pretty rare. On liars and bias — we think about this all the time. We don't take anything for granted. If someone says, \"here's why I did it,\" we ask, \"is this likely? does this match up with other records? could they be presenting this falsely in order to change the historical record?\" And often the answer is \"yes\" — especially with historical figures who talk about themselves, their motivations, their goals. Ferreting this out is a matter of comparing many sources, and building up a sense of the world at the time in history that the events took place, and then figuring out which sources actually seem to be reflective of that. But this is why historians are very dubious of long-after-the-fact recollections that are designed for public consumption, like memoirs: they are usually very selective in what they tell and don't, and even the best ones are tainted by a knowledge of what happened later. Could a document be simply _wrong_ — no lies, just error? Of course! It happens all the time. And again, we tackle this by never taking their truth totally for granted, and attempting, wherever possible, to find other sources that either confirm, contradict, or complicate the picture. The job of a historian, when we are doing research, is basically trying to sort through lots of documentation, figure out what it can and can't tell us about what happened in the past, and then try to sort a story and interpretation (\"what it all means\") out of all of that. No historian I know (and I know many!) ever thinks that any one of us is going to come up with \"the final story\" on the past, or that anything we decide today can't be overturned tomorrow by someone who finds something different, or comes up with a different interpretation. It's an endless job (as long as there are jobs to be had, anyway) — but we all do our part to try and contribute to the work. It's fun work if you like digging through dead people's mail. (And I might just encourage you to wonder how reliable digital sources are, or how easy they can be faked, or how easy they can be just plain wrong... the idea that \"digital\" means \"reliable\" is very far from the truth!)"
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