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md3te8 | How did the filming of the Apollo missions work? Was all lunar activity filmed? | How did filming the moon landings work? Was every event that took place on the Moon filmed, or was there some activity that took place off camera? | Technology | explainlikeimfive | {
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"There were cameras on the Moon missions, operated by the astronauts. There were also TV cameras, which had the big advantage that the recording was done here on Earth, where resources are plentiful. Landings were shot through the windows, relaunches were shot with TV cameras set up and left behind by the astronauts. Many events were filmed, but not \"all\" by any measure.",
"The landing was filmed on 16mm film, the film was developed when the astronauts returned. The first step on the moon was from a video camera attached to a landing leg, it was broadcast live and recorded on earth. Astronauts had a hand carried video camera that could be left on a tripod to video broadcast their activities. The camera on Apollo 12 was accidentally pointed at the sun and ceased to work early in the mission. One of the two astronauts typically carried a 35mm camera to take still high quality photos that were developed on their return. The rover, used only in the last few missions, had a built in video camera that could be controlled from Earth. This was the camera used to record the famous lift-off sequence of the LM from Apollo 17. The difficulty was that the commands sent, took over 2 seconds to reach the moon, so the controller had to anticipate the lift off and make a good guess as to how fast to pan upwards."
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mdahkj | Why can't voice changed audio be reversed to reveal the original audio? | Technology | explainlikeimfive | {
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"Some changes are destructive, and leave no way to recover from them. Some have multiple plausible starting points. Eg, if I shift my voice's pitch up, how would you know? Maybe I actually shifted it down. If I do it well you have no idea what change to make to leave it as it was, unless I tell you.",
"It's not a reversible process because you don't know what the voice changer did. All you get is a waveform (the \"wiggling\" electric signal you feed to the speaker). That waveform is the sum of the original signal and the distortion signal that the changer introduced and you can't tell which is which. Simple example...I am playing a musical note. I run it through a simple frequency changer and you hear a tone of 440 Hz (the note A). What's my original note? You know exactly how a frequency changer works but you don't know what my original note was because you're missing two pieces of information, not one...you don't know my original note and you don't know what shift the frequency changer put in. Without knowing one of the two, you can't separate the signal from the distortion.",
"If I roll a pair of dice, I can't unroll them to get the original number unless I was tracking every aspect of their journey across the table with ridiculous precision. How fast were they spinning when they left the hand? How many times did they hit the table? How hard is the table they landed on? etc. When someone scrambles or distorts audio for the purpose of obfuscation, they are changing it using an element of randomness. Basically, every moment of audio has a different filter applied to it, and without knowing what each and every one of those filters is, it's impossible to properly undo."
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mdd65v | How is calibration equipment...calibrated? | Technology | explainlikeimfive | {
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"Using \"standards\" - there exist objects that represent units of measure, ounces, grams, cm, inches. For chemical analysis there are also standards but those are usually just pure samples of whatever they're measuring.",
"There are levels of calibration, and you just need upper level. Think as you have a steel meter take it as lvl 1. So the calibration equipment is lvl 2, their calibration equipment is lvl 3... And this goes up to the definition of meter.",
"What type of calibration are you wondering about? Generally there's time-intensive ways to make something of that's highly calibrated, like [surface plates]( URL_0 ). But once you've gone through the effort of doing that you can use your new calibration thing to test other things. And nowadays much of the precise calibration is done with physics and lasers and stuff. Not practical to take to every thing that needs calibrated, but if you make one really good thing it can check a lot of other things."
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mdm6lv | if a monitor receives signals at a higher rate than its refresh rate, how does it handle such a request? | I've heard both that it doesn't matter so I should just cap my games and programs at whatever fps my monitor can display or that a higher frame rate than the monitor can refresh "gives my monitor more frames to choose from to display." Which is more accurate? If the latter, how does the monitor select which frames to display? Is there some sort of algorithm or method or is it just random? (Assume the computer and monitor are both fairly modern. Ignore the effects of air resistance.) | Technology | explainlikeimfive | {
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"Your monitor will always receive the frames at whatever frame rate it is running at, or more accurately it will run at whatever framerate it is receiving frames at. If that frame rate is too high (or too low) for the monitor to display, it will simply turn blank, and maybe display an error message - early tube monitors could actually suffer damage from the wrong refresh rate, but that is not an issue for anything modern. That means when your game renders at a frame rate higher than what your monitor is set up to deal with, your GPU comes in. It is what decides what frames will be sent to, and therefore be displayed on, the monitor. Whenever your game renders a new frame, it is written to what is called a \"frame buffer\", which is pretty much a space in the video RAM where the frame to be displayed is stored. Whenever the monitor is ready to receive a new frame, the contents of the frame buffer are sent out. However, it takes time to send the content out, and by the time one frame is done, the next one is already about to start. This means that with just one frame buffer, the new frame may be written while the old one is still being sent out. This means the writing may end up overtaking the sending, and suddenly instead of the old frame, you start sending a new frame. As a result, the bottom half of the screen may show a different frame than the top half, which is known as tearing. To stop tearing, you need to enable vertical synchronization (or \"VSync\"), which ensures that you always have a full frame ready to show. However, you do not know how much time exactly each frame takes to render, so just starting at the right time is not enough. Instead, you use two buffers, and read from one while the other is being written. Once the new buffer is full, you start reading from that one and writing to the other. The problem with this is that you can only write to a buffer after it has been completely read, and only read from it after the *other* buffer has been completely read, so there is a certain delay built into it. So, a modern solution is to have a third buffer. Basically, while one buffer is being read, you are continuously writing to one of the two free buffers or the other, and when a new frame needs to be read, you pick whatever one has been completed most recently. As a result, you can maintain VSync (and therefore avoid tearing) without your frame rate being limited to the monitor's refresh rate, and the delay between rendering an image and seeing it is sort of a compromise between single and double buffers."
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mdr3uy | Why to some high megapixel cameras in low-end mobile phones perform worse than lesser megapixel cameras in high-end mobile phones and what exactly creates the difference we notice? | Technology | explainlikeimfive | {
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"Megapixels are only one of the factors that determine a good image. Others are optics quality, sensor size and noise levels, exposure time, stabilization, image processing, aperture et cetera. In fact, more megapixels can have a negative influence on e.g. noise, since it means the camera uses more compact receptors. Also mobile phones do a great deal of image processing and high end phones do more than cheap ones."
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mdyqsi | How do they record Voiceovers for movies? Like how do they put the actors on mute, but still keep the sounds in the background? | How do they manage to keep all the other sounds (special effects, music, etc.), while changing the actors' voices? | Technology | explainlikeimfive | {
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"Im not an audio engineer myself, but my friend is and he’s done audio for some small movies and tv shows (although his primary work is music). Native voice audio for movies is often isolated with boom mics so the audio can easily be replaced with a voice over in the final mix. A lot of the background audio you hear is done by foley artists because isolated sounds give you the most control over the final product, especially since a lot of sounds wouldn’t be possible to record without foley (ie. Punching doesn’t make a big whoosh, nor does it make much of a sound in impact).",
"Dozens and dozens and dozens of audio tracks with crazy talented audio engineers mixing it all together.",
"Sound engineer here. Pretty much every sound in a film is put onto a different track which can be turned up or down individually, as well as things like where the sound comes from. When there's a voice over and the actors are muted, it's because everything is controlled separately.",
"Even more mind-blowing: when you see people in the background talking in a restaurant, but can't hear them, it's because they're just pretending to talk. Background actors may have to keep it up for hours while the stars spend multiple takes to complete a scene."
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me33ff | How do pulse oximeters work? How does it measure oxygen from your finger? | Technology | explainlikeimfive | {
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"Technically, a pulse oximeter measures hemoglobin saturation, which corresponds to oxygen saturation generally, but can be erroneous because it also responds if your hemoglobin is saturated with e.g. carbon monoxide. The device works by having two light sources in it. One of these lights is in the visible spectrum, and one is in the infrared. The device measures how much light is transmitted from one side to the other, but more importantly, measures the ratio between how much visible light is transmitted vs how much of the infrared is transmitted. Oxygenated hemoglobin absorbs infrared light and passes visible light, while deoxygenated hemoglobin does the opposite. So, while the total amount of light transmitted can vary based on the thickness of your finger or how exactly the device is clipped on, the ratio between the two remains consistent."
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me40pr | What is the difference between LTE and 4G? Is one “better” than the other? | Technology | explainlikeimfive | {
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"LTE is one of the 4th generation cellular networking technologies, and the only one in common use these days (WiMax never really took off), although some devices may label hspda+ as a 4th gen cell network technology",
"The difference between LTE and 4G is like the difference between a hammer and \"things you use to put in nails\", they're pretty much the same thing even though pedantic people will point out that not *just* hammers can be nail-inserters. To answer the question, there's no difference, unless you're using your shoe instead of a hammer, in which case the hammer is better.",
"4G is a very broad term that refers to the that generation of mobile technology. Kind of like cars, Honda = 4G. LTE and Wimax are examples of different and competing 4G technologies, kind of like the Accord vs Civic."
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me89r6 | Why can we run over 1 tile gaps in videogames | Technology | explainlikeimfive | {
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"A lot of games have a 'grace period' after you run over an edge where you can still jump. In those games, sometimes the grace period is long enough that it lets you run across small gaps. This period of time is sometimes called 'Coyote Time' as in the Road Runner cartoons.",
"Most platformers have a certain amount of «coyote time», named for Wile E. Coyote, built in to make the game a little less frustrating for people who might have trouble hitting the jump button right on time, whether due to lacking skills, physical impairment, or hardware lag. This means that occasionally, the game gives enough leeway to just run across narrow gaps entirely before gravity kicks in.",
"This is a mechanic there to make playing the game easier - when leaving a platform you have a short time where you still count as \"grounded\" - you don't fall and can still perform jumps. This makes the timing of hard jumps a bit more forgiving. The mechanic is called [\"coyote time\"]( URL_0 ) and exists in most platformers."
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meey7i | What is spintronic and how it work? | Technology | explainlikeimfive | {
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"Spintronics is the study of using electron spin in electronic devices. Basically, electrons have charge and spin, which is a rather complicated concept that you can visualize as an arrow. The direction that arrow points can be changed by magnetic fields. Now, modern electronic devices use only charge. A circuit works by flowing charge through wires, transistors, etc. This is why turning the power off on your computer causes most RAM to lose its information. Without the flow of charge, RAM and processor registers can't save their states. (This is why we need magnetic hard drives or SSDs.) Spin, however, is *intrinsic*, meaning that you wouldn't need to keep power flowing to maintain memory. Spin also points in a direction, which could be useful, since you could (in theory) transmit more information in a \"spin current\" (a line of little spin arrows pointing the same way) than in a charge current. The direction f the arrow could be used as additional information. Spin and charge currents also don't need to point the same way. You could have opposite spin currents with no net charge current! It is also possible that such devices would be far more energy efficient than current circuits. Understanding how to manipulate these spins, how they move, and how they work is what the research field \"spintronics\" is, but the general idea of having circuit devices which use electron spins as well as charge is also called \"spintronics.\""
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meh926 | If you replaced your individual lightbulbs with pairs of lightbulbs wired together in series, would that cut the current flowing through each bulb in half resulting in the bulbs lasting much longer? | Technology | explainlikeimfive | {
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"It would double the resistance, which would effectively cut the current in half. However, doing so may mean that neither bulb has enough current to actually produce light."
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mej80u | why does a phone’s battery keep working if plugged in just before dying, but takes a few minutes to turn back on if plugged in after dying? | Technology | explainlikeimfive | {
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"Because once the phone dies, it needs to boot back up. That boot up process is a bit more sensitive, a crash/the phone shutting down again during a boot up could possibly corrupt the files needed to run the boot. If that happens, you’re just dead in the water. So, smartphones will refuse to turn back on right away, allowing the battery to get enough charge that it definitely won’t die while booting up even if you unplug it again.",
"First, electrically, it takes more energy to go thru the startup process than to keep running. So a slow charge might be enough to keep it going but not enough to sustain a one-minute bootup. Second, electrically, all the components require a certain voltage range, batteries output higher voltage when charged, and voltage drops quickly under load\\*. So even if there's enough chemical energy in the battery to sustain a bootup, a near-dead charge level might not be enough to provide that energy at a fast enough rate. Third, on the software side, phone makers know about the first two reasons. So they program the OS (operating system, usually Android or iOS) to shut down cleanly when battery is critical and they program the firmware (the low-level code that handles stuff before the OS can load) to refuse startup until there's enough charge to be useful. \\*That is, idle voltage is higher than sustained voltage. This likely depends a lot on specific battery technology, and newer battery designs (and phone OSes) seem a lot better about this. My first smartphone had this so badly that I could do a high-intensity task (by decade-ago standards) for an hour, watch the stated battery level drop from 100% to 50%, close the app and turn off the screen, and check again in an hour to see 70% battery (not actual numbers, but nominal battery level did go up a lot while idling after a huge drain)."
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mekihw | How is an NFT bad for the environment? | Technology | explainlikeimfive | {
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"So, the thing is that an NFT relies on computers doing computational work, consuming electricity to do so. Consuming more electricity means the power generation stations are doing more work, which releases more pollution into the environment."
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melo3h | Database Performance vs Latency | What's the difference between database performance and latency? | Technology | explainlikeimfive | {
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"Performance is a broader term, it includes things like latency and throughput and resource consumption and so on. Imagine a rubber tube that is connected to a fire hydrant. We can measure performance of the tube. Latency is: when you open a hydrant, how long does it take for the water to start flowing from the other end of the tube. Throughput is: how many liters of water per minute can we push through the tube. Resource consumption is: how much pressure the pump would need to apply to push that amount of water through the tube. In case with databases, latency is how fast you can get the response after sending a request, and throughput is how many requests per N milliseconds you can execute."
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meme3d | How do batteries hold their charge for so long? How do they work? | Technology | explainlikeimfive | {
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"Batteries contain chemicals that create electricity in some way or another. This is called electrochemistry. The electricity is harvested by the mechanism the battery is part of. There are many types of batteries, so exactly what type of chemicals and other materials they contain varies."
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meobet | Why do phones have to download text documents and other files that computers can open up in a new tab normally with no download required? | Technology | explainlikeimfive | {
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"If your computer shows the document in another tab then is has downloaded it. If it was not downloaded how could you show the information? You are confusing downloading with saving to the device filesystem so it can be opened with another program versus displaying it in the browser. The difference is that for some reason the browser on the phone does not have support for the file format you downloaded. Phone browsers os does not have the support for an external plugin like on desktops because having at least historically been on devices with less ram and processing power that are battery-powered. So the browsers have been more streamlined."
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mesjw9 | Why are video games required to provide seizure warnings but movies are not? | Technology | explainlikeimfive | {
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"Movie theaters have been offering warnings and sites also have warnings. A lot of gamers play in dark rooms with their eyes right next to the screen. There's a difference in how people consume media.",
"Might depend on the country you're in? In NZ there are warnings for movies.",
"Because video games are under a lot more scrutiny. Surprisingly, they still carry a lot of stigma, and need to be a lot more conscious than something like a movie, which, relatively speaking, can do whatever it wants. A similar example is the way parents frequently freak out about M rated games existing, but not so much about R rated movies. It is absolutely an example of a double standard, and the culture still adapting to a newer medium. Back when movies first introduced sound, the same sorta stuff happened."
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mesnco | How exactly do cpu and gpu 'improve'? | How do they improve? for example what is the physical difference between RTX3080 and GTX1080? | Technology | explainlikeimfive | {
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"There are basically 2 ways to make a CPU or GPU perform faster: 1 - get more computation done in one clock cycle 2 - get more clock cycles per second. You can achieve #2, just by making the clock chip pulse at a higher frequency. But faster pulses will a) consume more power and generate more heat, and b) push the switching components closer to their error threshold, where you might start to see them output the wrong values. So to keep increasing the clock rate, you need to keep inventing transistors and logic and memory components which can switch more precisely, in fewer nanoseconds, and you need to keep coming up with better ways to suck more heat energy out of a little tiny hot microchip. You can achieve #1, either by adding more CPU cores to the device so that each one can work on its own math problems at the same time, or by changing the CPU architecture - perhaps by adding a new instruction which does what you used to do in three instructions. Those are the main ways that CPU and GPU performance improves generation over generation.",
"More transistors in the chips, more cores, and making those cores run at faster speeds. Cooling solutions and power delivery can also be improved."
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meta1z | What is www(World wide web) and how is everything stored on it? Does it have any data limit. Is it like a big drive or something like that? | Technology | explainlikeimfive | {
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"The internet is a bunch of computers with information in them, connected by a network (wires and devices designed to communicate information by sending electricity over said wires). The web is a sub-part of the internet, computers designed to present information as websites. As opposed to information presented as text chats, or game downloads, or movies, or other forms. Basically it's just computers sending information to you, when you click on things or go to a site. EDIT: The data limits are determined by the companies that own these server computers. For example, the Reddit company probably has a data limit; they're only willing to pay for so many computers to hold all these subreddits with all the text we type, it's not infinite. Microsoft, Amazon, Ebay, other companies have their own server computers and their own data limits.",
"The World Wide Web, or colloquially known as the Internet, is a network of computers on a wider scale. When you go to a website, what you’re actually doing is connecting to a server (or collection of servers) via an IP address (which a website name like URL_0 is translated through a domain name service, which is altogether a different subject). Everything stored on that server is done through the conventional means through some sort of media like a hard drive or solid state drive. Technically, the only limit the servers have in regards to storage is what each of these hard/solid state drives can hold. Since there’s so many of them, it’s near limitless. So, no, it’s not all one big drive, but thousands (if not millions) of drives all connected to this one huge network.",
"It's a bit more complicated than that. The way the Web works is that each individual website can be stored on a different server--in some cases a server will have multiple web sites on it, but mostly they're all separate. When you type a URL (e.g. [ URL_1 ]( URL_0 )) into your browser, the first thing it does is do a \"DNS lookup\" to find out what the actual IP address that corresponds to (it's similar to a street address, but for the Internet)--it then sends a request to that address for the web page, and hopefully gets a response. It's possible for a single server to have multiple websites on it, in which case, it figures out which one to send back by looking at the URL, which is sent as part of the website request."
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meviui | How were CDs and DVDs professionally made? What computers, software, and printers are used? | Technology | explainlikeimfive | {
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"They use a clean room and production line. Sound typically came from digital audio tape (in the '90s) and was then transferred on a glass disc called a master, using lasers. This master was then plated with metal to create a stamper. This entire process was relatively slow and took place in a clean room. The stamper was used to mould large amounts of cds (which are made out of plastic) on a production line. This is a quick process that only takes a few seconds per cd. Afterwards reflective material was dampened on the disc and the disc was coated with lacquer for protection. It is a different process compared to burning cd-recordables, as recordable discs have a layer with organic dye that can be burned using a laser. This also gives cdrs their distinctive color."
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mevosc | How do the new grocery scanners work where you just put stuff in a box do they work similar to book scanners | Link to what I mean URL_0 | Technology | explainlikeimfive | {
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"Typically, and this isn't necessarily the case in that one (simply because not there to see it), is something called an RFID tag. In short an RFID tag is coded with specific information, and when put near certain transmitters will send back whatever information is on the tag. This is often used in key fobs and security tags at stores."
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mewzyt | What are Tensor and CUDA cores? | Need help understanding what exactly Tensor and CUDA cores are and what they do in graphics cards | Technology | explainlikeimfive | {
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"[Based on this answer in stack overflow]( URL_0 ) They're both essentially just a part of the GPU that is really good at a certain type of calculation. CUDA cores are good at multiplying two numbers and adding it to another number. Meanwhile, a tensor core is specialized in doing the same but with 4x4 matrices instead. Both of these types of calculations are heavily involved in rendering traditional raster graphics. They also happen to be very useful in machine learning, which is why you'll often see GPU used for AI"
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meyttz | How do contact lenses stay in correct position following your eye movement? | Technology | explainlikeimfive | {
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"Your eyes aren’t actually perfectly spherical. The cornea bulges out slightly, and the contact rests on that bulge, so as your eye moves, so does the contact",
"Contact lenses for astigmatism also have a nearly imperceptible weight on the bottom to ensure it spins to the bottom to line up correctly :)"
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mez50b | Why is it that a movie plays at 24 FPS and is buttery smooth, but then a video game at the same frame rate is like a slideshow? | Technology | explainlikeimfive | {
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"- It is not buttery smooth. The choppiness of 24hz is quite obvious if you have ever seen movies at a higher frame rate. - Film cameras have natural motion blur, which kind of smooths movement across multiple frames. In video games this has to be created artificially. - Video games are interactive. The frame rate matters a lot more, because it has react to the player's inputs as quickly as possible.",
"Because videogames are interactive. You expect things to change instantly when you click something, and at 24fps there is a noticable delay between action and visible change.",
"i cant speak on video games but in film there is shutter speed, aperture, and frame rate. shutter speed is how long the shutter of the lens is open for aperture is how wide the shutter opens and frame rate is what you referred to. common frame rates are 24 frames per second, 30fps, or 60fps. with shutter speed, the longer the shutter is open for (meaning a slow shutter speed), the more action it picks up in each frame. it’s formatted to look like this: 1/1000 is a very fast shutter speed, while 1/30 is a much slower shutter speed. a typical rule of thumb for film is to double the frame rate (in this case 24fps) to get 1/48. not only are you picking up more the movement but each frame will likely have a slight blur in any motion, giving the illusion the frames blend together. for an action flick, cinematographer might choose a faster shutter speed to get a choppier appearance."
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mf1ksg | What does computer hacking actually look like? | Technology | explainlikeimfive | {
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"Either: a ) An email sent to someone working in the office with a dodgy link b ) A person opening a program and typing a few words in to a form before clicking \"scan\" c ) A very tired looking person looking over documents, slowly stepping over code on a black console on their screen, occasionally typing in a command or two before cursing a bit and trying something else. If said person is lucky maybe they get a somewhat positive response from their commands and they get slightly less irritated. Hacking is exceptionally boring as a spectator activity. It's not fast and frantic with numbers flying all over the screen and the need for three people using two keyboards. It's just a person writing code and sending commands in hopes of finding and exploiting some weakness.",
"It can still involve a screen that is full of incomprehensible code (to an outside observer) but it will also involve browsing documentation of other software standards and implementations, looking at and copying code from other programmers, sitting around and pondering problems, etc. It isn’t some intense keyboard sprint, hacking usually takes weeks or months to perform.",
"The vast majority of what is called hacking these days mainly refers to social engineering like phishing. Actual hacking usually consists of building a program to do something for you followed by looking for a way to get a target to execute that program. It’s mainly software development which is essentially text editing interspersed with cursing and long sighs.",
"Mostly casual typing, maybe a bit more stressed hair pulling dependent on the hacker. If you are a professional penetration-tester (good guy hacker) then it's this followed by hours of report writing, so even more casual typing.",
"Most of it is done via phishing, email attachments, social engineering or using leaked passwords (when people have re-used the same password on other sites that have been hacked in the past). The next way in is unpatched software. If a company hasn't updated their mail server or some other piece of software since 2018, there's a good chance that there are well-documented vulnerabilities, so you'd read up on them and spend a day or two or three putting together a script that takes advantage of this vulnerability. And if that doesn't work, you look at what kind of software is running on the server and look for some kind of service or app or device that's accessible from the internet and somewhat obscure. You do that because the most commonly used software tends to be pretty well maintained and probably doesn't have have undiscovered, easily exploitable bugs. But some kind of niche device or app that hasn't been scrutinized to the same extent is probably not as bug-free. Then you get yourself a copy of the app or device and try various techniques to get in. And once you find a bug after days of testing and probing, you may be able to use the same technique on the network that you're trying to break into. So it's basically someone sitting in front of a computer for days or weeks, bored, slowly going over hundreds or thousands of pages of decompiled code or memory dumps as well as writing code. It's about as exciting as an accountant doing an annual report in Excel, so it wouldn't really work in a movie."
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mf4s3k | Why are there so many conspiracies about 5G in particular, but not for preexisting cellphone networks? | Technology | explainlikeimfive | {
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"Basically all new techs have some kind of conspiracy nutters (I’ve still got a non-gmo, anti-microwave aunt). Same thing happened with cell phones, and WiFi, and every tech that can’t be seen. The only reason the 5G conspiracy is more common is that a significant portion of the US has recently taken a departure from reality. The formerly tiny corner of the internet that substitutes is own reality went from a fringe to now a significant portion. That means that more people with low passive critical thinking abilities are seeing hubbub about something they don’t understand...and only see the conspiracies instead of the scientists saying “it’s just non-visible light”.",
"Side note to what everyone else is saying: a conspiracy and a conspiracy theory are different things. A conspiracy is an actual crime with a legal definition where multiple people are orchestrating a crime. A conspiracy theory is a term that's almost always a in reference to a crack pot taking circumstantial evidence (or none at all) and saying it's proof of an actual conspiracy.",
"Lots of 5G talking points are about a 'HUGE INCREASE IN BANDWIDTH' or the 'ABILITY TO CONNECT 100x MORE DEVICES', which can come off as increasing exposure to more powerful radiofrequencies. In reality, 5G wavelengths are less penetrative and MUCH more narrow (power spread over less than 1 degree vs. LTE 10+ degrees) but I don't think people with strong negative opinion on the technology understand it very well.",
"Unscientific answer: There WAS 4g conspiracies also, same with 3g, etc. It's just so long ago that nobody remembers. Also, I imagine that the social media age made this one a lot more widespread.",
"People can be made afraid of things they don’t understand. Existing cell phone networks generally aren’t something people fear because they have been around for a while and apparently haven’t been causing harm. You can’t argue a cell tower that has been standing for ten years is going to turn someone’s brain to jelly, because why hasn’t it already? But people might believe new technology they have never encountered can cause such harm."
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mf880u | How were codes for Game Genie/Gameshark/Action Replay found/created back in the day? | Technology | explainlikeimfive | {
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"The other answer is talking about something different, actual cheat codes. Most game genie devices that I'm aware of don't do that. They alter memory addresses. The console stores everything in memory. Ammo, weapon, lives, points. The game genie forces the value to whatever it wants. As for how it's found (I e. How to make the code), trial and error. You can take a dump of everything currently in memory. It will be in hex, it won't be in English and won't make sense to a naked eye. Then lose a life and take another dump. Compare what has changed. Even if it doesn't make sense reading on its own, your can still spot the difference Do it enough and maybe you learn that line 4, character 6 is where the life value is stored. The \"code\" can then be made as an instruction of what location in memory to edit and what value to insert.",
"These devices could look at all of the numbers stored in the memory of the console. To make a cheat work, you would have to find a memory value that matters (like the player's HP or number of lives or whatever) and tell the Game Genie what value you want it to have. To make it more clear, let's look at an example card for Final Fantasy IX using the GameShark. Here's the code: 8008B7B0 FFFF The first portion \"8008B7B0\" is the memory address that the GameShark is modifying. Like 1234 Sycamore St. is the address where Steve Smith lives. For this code it's the place where the amount of money the player has is stored. The second portion \"FFFF\" is just the largest number that can be stuck in that memory address. It's hexadecimal for 65,535. So the GameShark in this case is forcing the player's money to always be 65,535 by screwing with the console's memory. So how is this code found? By checking all the different numbers in the different memory addresses in the console until you found the address you want. A lot of these devices could do this on the fly. Many GameShark models had a little button that you pushed and it would pause the game and do this. So it pauses the game, then you tell it to search for a number. If I'm looking for player money in FFIX and I had 125 at that point in the game, I could punch in 125. Then it tells you all the different memory addresses that currently have that value. To narrow it down, you could earn or spend a little money and do the process again until you keep getting the same memory address show up in your search results repeatedly. That's your new cheat code: 8008B7B0 for the memory address and then whatever number after that that you want."
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mfbpt6 | How are DVD "easter eggs" created? | Technology | explainlikeimfive | {
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"The DVD menu system is more complex than it seems. You can make buttons/links pretty much anywhere, make links only available at certain times, and act on simple variables. Most easter eggs are presented by abusing these features to hide a piece of video until someone finds the button and presses it."
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mfh3ni | Why your printer needs magenta just to print in black and white? | I get printers are way advanced now... but why do I need color(magenta) to simply print in black and white. | Technology | explainlikeimfive | {
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"Because the people who made printers want you to buy a new printer cartridge. They make close to nothing on the printers, they make money on the inks. They've configured the computer programming parts of the printer to say you are out of ink, so you go out and buy more ink.",
"The *only* reason is they want to sell you more expensive ink. Buy a printer with \"eco tank\". Then you can buy bulk ink without ever needing a cartridge again.",
"If your printer is a 4-color, you have a black cartridge, and should have a “grayscale” option in the settings that forces it to only use the black cartridge for everything in a print job."
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mfh4q4 | How do power plants actually make electricity? | Technology | explainlikeimfive | {
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"There are lots of types of power plants, but most work in one way or another by turning a turbine. The turbine spins magnets in a metal coil which pushes the electrons in that wire and that is what creates the electricity.",
"Something inside the plant creats physical work. This can be burning coal to heat water to spin a turbine, or letting the wind push a fan blade to spin a turbine, or allowing water to fall onto a wheel to spin a turbine... I'm sure you see a pattern here. That turbine is connected to a system of magnets, which are spun around using the turbines. And by placing copper cabling next to the spinning magnets, an electric current begins to run through the cable.",
"Steam turbines. At the very basic level, water is heated to steam to turn a turbine and that kinetic energy is converted to electric energy. Most often, fossil fuels are the primary source of heat, but nuclear power plants use nuclear energy to heat the water instead."
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mfo5p9 | How did so many places learn to process and harness Copper to get out of the stone age? | I've been watching heaps of pre-history videos and people replicating how to make tools from copper, iron, etc. Copper alone seems like such a HUGE jump and complicated process. How would have people have known to mine and heat (put simply) copper ore into all these copper tools? | Technology | explainlikeimfive | {
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"Imagine you're using stone all your life to poke and chop things. You get irritated by the stone always chipping and breaking and you have to go find a new stone to do this... multiple times a day. But one day you find this neat greenish and shiny stone. You start noticing that the gray bits fall away leaving more of that pretty shiny stuff. But that shiny stuff seems more reliable than the gray stuff. You show your friends these cool shiny stones and demonstrate their superiority, so they become the new standard and everyone begins using them. Then your cousin Ugga, who is also the clan buffoon one day drops his stone in the fire. He panicks and cries, then goes to bed. But the next morning, Ugga comes to retrieve his pretty stone. He sifts through the embers of the fire with a stick for it and finds it completely changed by the fire. It's now the color of the sun, shinier, and deformed relative to how it was when he tossed it in the. Both excited and upset, he shows others. One guy decides to do an experiment and discovers that heat makes the shiny stuff more malleable and devises his own tools to make more shiny rock. Then the first metal spearhead is formed and the first foundry is planned. And so of your prior now know that metals are weaker with heat and everybody starts spotting metal more frequently.",
"Humans were already using (and still use) pottery kilns - a kind of a hot-burning oven for making solid pots, hard bricks and other useful stuff like that. The temperature in such a kiln can get high enough to melt copper, so they might have accidentally smelted the new* shiny metal, got interested with its properties and then experimented further to get more of it. *copper was not the first metal to be discovered by humans. Tin and lead had been found and used before copper, as they have a lower melting point and can be smelted in a campfire.",
"Gold and copper could be found as pure nuggets in streams or just in the ground, called placer deposits. They do not corrode away so the large nuggets just lay there until someone found them. This is how more modern gold rushes would happen - someone would find a gold nugget in a stream. So we have found native American copper and gold items made by just hammering out a nugget of the material with a rock. As they used up the larger pieces, they would work the smaller and smaller pieces. Eventually they learned how to melt small copper pieces to make larger copper pieces. They were probably smelting copper before they started mining it. Once they could smelt it, getting more small pieces would be useful.",
"We've been using fire for a long time. First for light, then for cooking, and then for pottery. When you're building fires (and kilns) you put rocks around them, and some of those rocks contain lead and tin. Those metals melt, and leave you with soft metal to play with. Soon, you find out what kinds of rock make metal when they're heated, and start doing it on purpose. Then you start heating other rocks that look interesting. Most of them don't do anything, but eventually somebody puts a copper-bearing rock into a pottery kiln, and finds out that copper makes pretty good (compared to rocks) tools and weapons. Before too long, somebody else discovers (probably by accident) that combining tin and copper makes bronze (or pewter if you do it wrong.) Bronze is vastly better than copper for weapons and tools, and you've just entered the Bronze Age. (Pewter is good for making pretty things, but isn't very useful for tools.) It will be a while before the Iron Age, because iron melts at a really high temperature compared to copper and tin.",
"Copper is one of the few metals that could be easily found in its native form. Most other metals were locked up in ore. More importantly, copper could easily be pounded thin enough to make a sharp blade."
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mfpeq6 | What does hexadecimal have to do with binary? | Confused sounds | Technology | explainlikeimfive | {
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"It’s a power of 2, 16 is 2^4, which makes it really handy, that means 4 bits is just one digit (number or letter A-F) in hex So for example 1100 is C in hex but 12 in decimal And a byte is just two letters, so 1100 0011 is C 3, you simply need to split in 4 bit chunks and turn each 4 bit chunk in a digit, which is super simple Compare that to converting to decimal, which requires doing divisions and module operations which are much more time consuming for the processor",
"Binary is good for computers, but it's tricky for humans to read because the numbers get big (as in the written form takes up a lot of space) very quickly. The number one thousand in binary is 1111101000 (10 digits long). So, we convert it to hexadecimal so humans can read it more easily. Let's write out the numbers from 0 to 15 in binary: 0=0000, 1=0001, 2=0010, 3=0011, 4=0100, 5=0101, 6=0110, 7=0111, 8=1000, 9=1001, 10=1010, 11=1011, 12=1100, 13=1101, 14=1110, 15=1111. Now, you can see that for most of that we only used a single digit. Let's suppose we expand and include a few extra \"numerals,\" and we'll label these with A, B, C, D, E, and F. A will be equal to 10, B to 11, C to 12, D to 13, E to 14, and F to 15. Now our hex and binary table looks like: 0=0000, 1=0001, 2=0010, 3=0011, 4=0100, 5=0101, 6=0110, 7=0111, 8=1000, 9=1001, A=1010, B=1011, C=1100, D=1101, E=1110, F=1111. This means we can take any 4-bit binary number (a number in binary that uses 4 zeros or ones) and replace it with a single digit. Take the example of 1000 from earlier. That was 1111101000. We split it in to groups of 4 digits: 11 1110 1000 Pad the beginning with extra 0s: 0011 1110 1000 Then replace each block of 4 with a single hex character: 3E8 Suddenly that 10-digit number takes a lot less space on the screen. And because hex maps perfectly to binary (since 16=2^(4)), it's super easy for computers to convert between them. This is the advantage that hex has over base-10. The computer has to do lots of divisions or multiplications to convert between binary and decimal. But binary and hex is just a nice, easy table.",
"16 is 2 to the power of 4. So every hexadecimal digit is equivalent to a sequence of exactly 4 binary digits. And a byte (equal to 8 bits or 8 binary digits) can be written down as a two-digit hexadecimal number. This allows for a more compact and readable notation of what is still in essence a binary sequence.",
"Let's start with what Base 10 is. When you count, you have the numbers 0-9. When you try to add 1 more to 9, you've run out of ways to represent it, so instead, you count up in the next column, and rollover 9 to 0, giving you 10. With binary, you only have the numbers 0-1. If you try to add 1 to 1, you have run out of digits, so you rollover and add 1 to the next column, giving you 10. With hexadecimal, you have the numbers 0-F (A representing 10, B representing 11, F representing 15, etc). If you try to add 1 to F, you run out of digits, rollover, and have 10. This is true for any Base-N counting system. You have the numbers 0 to N-1, and if you try to represent exactly N, you would write 10. Now as for what Hexadecimal has to do with Binary? It's because it can be directly translated easily. If you were to try and translate the number 192 from Base 10 to Binary, you have to do it more or less via brute force. However, hexadecimal has a bonus. If you were counting up in binary and hexidecimal at the same time, you would notice that as you approached 1111 in binary, you would also be approaching F in hex (15 base 10). When you add 1 to either, you roll over. Because the rollovers happen at the same time, the next 4 bits also rollover at the same time as 1 hex digit (FF vs 11111111). This follows true for any number of digits. This means every single hex digit can represent exactly 4 bits **entirely**. This means if you're converting, you don't need to start from the bottom of the number and work your way up, you can just do it in 4 bit chunks. You can convert between the two freely from the start or from the end, as long as you have 4 bit chunks."
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mfq2gb | Are LEDs of varying color doped to get a certain frequency or do they use dyed plastic heads to get the color? | Do they dope the silicon with various element to get the bandgap which matches with the wavelength the color, or do they just dye a transparent LED head (or whatever it is called) and use a single frequency? | Technology | explainlikeimfive | {
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"Yep, the use different materials to get a specific frequency, you’ll sometimes see blue LEDs called “gallium nitride” because that’s what they use to make them. However white LEDs use just blue LEDs, but put a layer of phosphor on top in order to get all the colors of white light in a spectrum. There are some rare colored LEDs that use the same method as white ones, but with a colored phosphor instead for a less monochromatic light",
"They are all clear lenses now. They do as you said use different frequencies to achieve different colors. Early LEDs did use dyed lenses and that's why a lot of older equipment that uses red LEDs, the red is pretty washed out looking and more like a pink."
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mfqjty | What do companies like Intel/AMD/NVIDIA do every year that makes their processor faster? | And why is the performance increase only a small amount and why so often? Couldnt they just double the speed and release another another one in 5 years? | Technology | explainlikeimfive | {
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"If they can improve speed by 10% and make a new product, they can release it now and start making profit on it instead of waiting 5 years to make a product 20% faster to only get the same relative profit. Simply put, improvements on technology aren't worth anything if they sit around for years not being sold. It's the same reason Sony doesn't just stockpile hundreds of millions of PS5s before sending them out to be distributed to defeat scalpers - they have a finished product and lose profit for every month they *aren't* selling it.",
"Digital design engineer here (working on 5G mobile communications chips, but the same rules apply). Improvements in a chip basically come from two areas: Manufacturing and the design itself. Manufacturing improvements are mostly related to making all the tiny transistors even tinier, make them use less power, make them switch faster and so on. In addition you want to produce them more reliable and cheaply. Especially for big chips it’s hard to manufacture the whole thing without having a defect somewhere. Design improvements involve everything you can do better in the design. You figure out how to do something in one less clock cycle. You turn off parts of the chip to reduce power consumption. You tweak memory sizes, widths of busses, clock frequencies etc. etc. All of those improvements happen incrementally, both to reduce risks and to benefit from them as soon as possible. You should also be aware that chips are in development for several years, but different teams work on different chips in parallel, so they can release one every year (or every second year). Right now there are no big breakthroughs any more. A CPU or GPU (or any other chip) which works 30% faster than comparable products on the market while using the same area and power would be very amazing (and would make me very much doubt the tests ;) ) Maybe we’ll see a big step with quantum computing. Or carbon nanotubes. Or who knows what.",
"At the current level of technology, the complexity and the amount of resources involved, things don't improve in great big leaps quickly. There are so many interrelated areas that trying to make huge leap involves equally huge risks. At the same time, companies cannot design JUST the next generation of product. There are multiple projects going on at the same time each with some planned future launch dates because these projects take so much time to complete. With each technology building on the previous one and all these simultaneous activities, what appears to be incremental increases are all the result of multiple decisions and investments made years beforehand. This is the result of the compromise between performance and risk.",
"They don't always make them \"faster\" in the sense, but better at doing specific things. For example a difference between older and newer CPU might not be in it's speed, but the fact that the newer CPU has extra functions that can do certain things more efficiently or in a different way. Like let say that file format .meme became really common few years ago (CPU development and manufacturing cycles are fairly long), so in the next year the manufacturer could include a special portion on the chip that is dedicated to decoding and working with that file format. That is able to do it faster and better, than just doing it in a non-dedicated manner via the other parts of the CPU. Imagine that instead of trying to translate document using a dictionary and going word by word, you give it to someone who know the language and can translate it easily. In this case the other person is the dedicated function or part of the CPU. It is these features which are better and more efficient at very specific work, that are different. A CPU might (and usually does) have a dedicated portion and functionality for video decoding, or graphics processing. The graphics processing functionality can also be used for different kind of maths like physics calculations, which means that work load is not going through the main CPU. Difference between a CPU and GPU is that one is specialised in graphics, you can also have, APU (Audio processing unit) which is specialised in audio. Or whatever the developer wants to put there. And lets go with the .meme format still. The new CPU has a dedicated function for this, well the next year's CPU might also have a dedicated function that does this slightly faster and more efficient, there for you could say it is \"faster and better\". Now. Another important thing to remember is that if this year's CPU works does things specific way and has these specific functions. Next year's CPU might basically be identical but they just organised everything better in the chip. If you get .1% faster times doing a thing because you moved it around on the chip, then when that thing is done billion times, the speed adds up significantly. But what they actually do to make next year's chips better is a secret. Usually you can get some information by diving deep in to the documentation and comparing. But what they actually did on the chip, is a trade secret. Speed isn't everything on the CPUs. It doesn't matter how fast you do work, if half the work you do is unnecesary. Then someone who doesn't do that unnecessary work can work slower and still gets the same results. Like imagine that you are trying to dig a hole with a spoon, and I'll dig with a shovel. I have to do WAY less work to keep up with you, and if I want to I can dig the with way fewer actions than you, because my shovel is more efficient. Since we are reaching the physical limitations of CPU size and speed. As in if we try to make them smaller we start to get strange problems like charges passing through things they shouldn't be. Things actually getting limited due to speed at which charges can move in the conductors. So when we hit the practical limit of \"It isn't worth the headache\" and \"We just physically can't make this happen because physics limit us\", it is more about the race of being better and efficient. Basically making shovels for every use.",
"If they released only once every 5 years, then people who don't already have a computer (or whose computer broke) in the third or fourth year are shit out of luck. They either have to buy a computer that's about to be shit, or they just have to wait. Sometimes waiting isn't even an option because you need the computer for work. By releasing once a year, they guarantee that their newest product is at most a year old and will still be relevant in a few years. No matter when you buy the computer, you have a decent option that will last for a few years. They don't expect most people to upgrade their rig every year.",
"In addition to what others have said which is valid, to address your question about just doubling the speed - It IS true in a lot of cases (especially mobile processors) that speeds could be increased more than they are. But, things tend to be dialed back from their maximum capabilities in order to balance performance with heat generation and power usage. The more transistors you pack into a smaller area, the more power it takes to run and the more heat it generates. If you're targeting a particular power usage and heat generation point, you'll still definitely see performance benefits with more transistors in the same area - but still a decent amount less than if you just say, packed in twice as many transistors and had it use twice as much energy and produce twice as much heat. It just wouldn't be stable.",
"Ok, so a processor is a wafer of silicon with a huge amount of little wee switches etched into it. So, think of it this way: there are two ways to improve the performance of a processor. The first way is to find better and more efficient ways to organize all these little switches together - these tend to be incremental to provide little bumps here and there, for example imagine instead of having one big long line at the DMV, having several lines, maybe figuring out a way to divide people by what they need and having them fill out the forms needed while they wait instead of when they get to the counter. Then we get more people thru faster. Awesome! The second way is to improve the actual switches themselves - to make them in a way that they can be switched faster (because switching is NOT instantaneous), and/or in a way that you can fit more of them onto a die. If you can manage that, you can increase the amount of thoughts a processor can think in a set amount of time. And if you can fit more, you can have more cores or other bits that allow more thoughts to be worked on at the same time. Great, right?! However, there is a tradeoff - for science reasons, usually if you want to make a switch open or close faster, you need more electrical current. But this in turn generates more heat. Think of it like your stove, the more electrons that run through it, the hotter it gets. The heat generated in just one of these switches isn't much, but when you cram millions of them together, it can become quite a lot. And because the actual silicon part of the chip isn't all that big, you end up needing a lot of cooling to get all of that heat away from that small chip before it builds up enough to damage it. So, in order to improve these things, you need to find a way to get more switches into the same chip, using the same amount of electricity, but also ideally at a higher clock speed. As you can see, increasing one thing makes the other worse. Researchers have worked very hard on figuring out new and different ways of making the switches so that they can still switch fast with less heat. But these discoveries are a lot of work, and have a lot to do with what can be achieved on a large scale - a new innovation doesn't help if it costs 100 times more to make. But those researchers study and study and figure out how to manufacture these improved switches more cheaply, so something that was only for crazy expensive supercomputer processor ten years ago can be found on your phone or laptop today. But the long arc of the story is this: while it seems that processors are just on this steadily improving trajectory, each improvement is, in fact, a breakthrough, a new discovery, a big deal. And a lot of people think we're starting to reach some the limits of what we can improve in silicon based processors, and we're seeing that modern processor specs are no longer improving in the leaps and bounds that they used to.",
"back in the 90's you could have 100% performance gains from one year to the next... today there is little to improve and they launch something when it's good enough to market it...",
"From the actual engineering standpoint, the speed gains come from learning how to put more transistors into the same surface are than before. The small steps thing has less to do with engineering and more with capitalism. Why sell one processor with a huge jump every 5 years when you can sell one every year with a smaller jump? That phenomenon is by far not restricted to processors. It's everywhere. Cars, phones, televisions, fashion. Everything. We are (in the western world) way beyond the point where capitalism satisfies actual needs. Instead, most companies create wants by building competition to their own products. And even [Planned Obsolescence]( URL_0 ). EDIT Holy shit, I'm flattered. Thanks for the award! PS.: Don't tell actual five year olds I said the s word.",
"Best ELI5 i can manage: Processors and GPU’s are like car engines. Imagine if you could shrink down your v6 engine to half size, and it still had the same amount of power. Now you have room for two! Double v6 engines! They’re going to use more fuel, though. Not as much as double (they’re smaller) but more. Then somebody goes “hey, what if we make those v6 engines into v8 engines? Add more cylinders and make the fuel intake a bit more efficient?” Then some year later, somebody goes, “hey, your double v8 engines are cool, but i can shrink them half the size again, so we can have 4 v8 engines!” Repeat as much as they can and eventually: “Folks, we have a problem. We can’t make the metal or cylinders any smaller. The fuel won’t go through, and they won’t be strong enough. Its too dense!” This is the essence of Moore’s Law, and its limits. Shrink, double, shrink, double, every 2 years until a wall is hit. —————////——/- This is what GPU/CPUdevelopers have done since...ever, pretty much. They’re at a wall where they’re having a hard time shrinking and doubling, so they’re looking into making *different kinds* of GPU’s. For example, new GPU’s have cores that focus on just raytracing, rather than everything. Some have new cores that just focus a bit on AI tasks, or monitoring and optimizing themselves. A bit like if someone decided “lets make one engine just for wheels, another engine just for the A/C.” In an effort to improve efficiency and ability, rather than just “More and smaller”",
"Late to the party but what if we can’t make processors smaller , why don’t we just make them bigger?",
"To milk as much money out of the market as possible. Note also most CPUs are one design and then they artificially disable components to make different specs at different prices, but the \"thing\" is very often identical manufacturing wise to the most expensive model.",
"Essentially you don't know what the future holds for you. You don't know you will get 20 percent faster in 5 years. You don't know that so there is no point sitting on 5 percent improvement that you did today lest someone else beats you to market. And that's how it works in pretty much all the consumer industry. This is what we can do today. If something changes we will update it in future. TVs for example we had to go through crt, plasma, led, lcd. 480p, 1080p UHD and so on."
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mfs2d1 | Why are programming bugs seemingly impossible to eliminate? | It seems like with every type of software, no matter what it is, theres bugs, and sometimes hundreds to thousands of patches, and wet bugs persist. Why is it impossible to completely eradicate them? You’d think after enough patches there would be nothing left to fix | Technology | explainlikeimfive | {
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"Modern software is very complex, very large, and, crucially, highly-interdependant on both other parts of the software and common shared software that it's getting from the OS or other programs. That last point means that fixing one bug can often create others as it interacts in a new/different/unexpected way with other parts of the software. This is a specific case of what's called \"system safety\" in the safety world...it's entirely possible for a system to malfunction even when every individual piece of it does exactly what it's supposed to do because you get emergent properties from the interactions. There's no theoretical barrier here, very simple or deterministic codes, or those that run basically isolated and iterated for decades (things like calculators or industrial controllers), or things where that level of scrutiny makes sense (banking cores) can be essentially bug free. But in virtually all \"normal\" software, you get into the realm of diminishing returns and killing \\*all\\* of them gets infeasible.",
"Programming is like setting up a bunch of dominoes that knock over other dominoes in sequence down the line. When you mess with one, it messes with others downstream. When you fix one thing, it probably changed the way another domino interacted down the line, and now you need to fix that one, which causes another change and so on and so forth. Almost every event is dependent on the results from a previous event, and so when you change the event it changes the output which changes how a different event processes. Since everything is so dependent on each other it becomes a game of \"fixing one thing to break another\".",
"Software is notoriously complicated. Tens of thousands of instructions weaving in and out in a complicated system that is hard for any single programmer to fully comprehend. Systems and subsystems are interlinked and often changing something in one spot will change a different thing elsewhere that was relying on the first changed system. Because this is a complicated system, and because programmers are human, and because the environment the system itself is running inside changes frequently (web browsers changing, operating systems updating, users mucking about, what have you) often even perfect systems can have very hard to spot bugs, and fixing those bugs can lead to unknown instabilities elsewhere. Then there's always a matter of competence (you think you fixed it but didn't, just masked up the symptoms) or priority (A tiny hard-to-fix bug that affects 0.01% of users is generally left alone over implementing new features or tackling issues a lot of people see)",
"I'm going to answer very generically because without knowing your specific example it's hard to say. No bug is impossible to fix, outside of a hardware fault. But some are very expensive. Programs can be very complex, and a seemingly minor detail somewhere can have unknown consequences elsewhere. So fixing one bug might introduce several more. And it can get to the point where you basically rewrite half a program to avoid a minor bug. That's just not worth the time for most programs. As to why there are bugs, again it's time Vs cost. The bigger a program gets the more difficult, time consuming and expensive it gets to test every possible scenario. So bugs slip through. I've heard an anecdote before that helps illustrate. A company made a program to simulate a bar. They want to test it, so hand it to some testers. One asks for a water, program correctly says tap water is free. Another gets a beer but doesn't have enough money to pay, program recognises there's a negative number where there shouldn't be and handles it. Great. Program works fine. It gets released. First user asks where the bathroom is. It crashes. I may not have told the story well... But it (hopefully) illustrates how difficult it can be to plan for and test virtually limitless possibilities."
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mfsr4l | How does "optimizing" code actually work? How can just changing a few lines improve a game's fps? | Technology | explainlikeimfive | {
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"You're going over to a friends house, you know the house number and you know the block they live on. There are 10 houses on this block, They are numbered from the left end of the street to the right, but you can't see the house number unless you go up to the front door of the house. One way to find your friends house is to start at one end of the block and go up to every front door and check to see if it's the correct house. This could take up to 10 visits (one for each house). But why not take less time? If you go to the middle house and look at the house number, you can see that if it's less than your friends, all of the houses to the left of that one are definitely not your friends (and vice versa). Repeat this again and you will continually cut in half the number of houses left that you have to visit to find your friends house. This will take at most 4 visits to find your friends house. With this small number that doesn't seem like that much of a big deal, but imagine if instead of the block having 10 houses, it had a billion houses, imagine how long it would take to visit every single house versus cutting the houses you have left to check in half repeatedly?",
"There's thousands of different ways to optimize but in general it's usually how things are stored and processed. Imagine counting to a 100 but every time you hit a new number you say all of the numbers before it. 1, 1, 2, 1,2,3 etc. It would take you a lot longer right? Another example might be counting to 100 but you have to write it on a piece of paper as you go. These sound silly but sometimes in writing code we don't realize we're doing things like that, optimizations are usually fixing things like that"
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mfuwxm | What does an ISP (or whoever owns the lines) actually need/do to make faster internet speeds? | I have a vague understanding of IT. But I've never really thought what is actually used for increasing speeds. I gather the obvious of new technologies allow for increases as a general statement. But, what are the physical things? Is it just more servers? More interconnections? I'm UK based. So how does my FTTC line go from 8mb max a few years ago, to 25mb now? (Yes its still a rubbish speed), when as far as I can see nothing has changed other than a new router - the roads haven't been dug up at all so assume copper lines are unchanged. Thanks. | Technology | explainlikeimfive | {
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"One of the major advantages about fiber optic communications is that the wires in the ground are capable of much higher speeds than we use today. In the future when newer technologies come out, all they have to do is put different transceivers at each end and the same cable can now carry more data than before. For your home connection, it's likely a different issue. The equipment they already had could support the faster speed a long time ago, but if they gave that speed to all of their customers it would create a bottleneck further up the stream. Your ISP connects to other major networks at interconnection points. The links between the networks is limited and if every customer tried to use their home connection at max speed at all times, these interconnects would almost certainly get flooded. What likely happened is that your ISP upgraded their interconnects with other networks so that they could safely offer faster speeds to the end customer without flooding the ISPs upstream links."
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mfz2x5 | How do nuclear powered ships work compared to a nuclear powerplant? | I get the point that the ships operate with a running nuclear reactor which generates steam which powers the ship. But as far as i know its very important to keep a nuclear reactor as stable as possible and you can't just turn it off like a lightswitch. But what happens now when e.g. the ship is moving at full speed and "full power mode" compared to e.g. standing still and using no power at all? Also, can they simply switch off the reactor when the ship is anchored for a long period of time? | Technology | explainlikeimfive | {
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"Both land based and ship based reactors are variable to a degree. Both have _control_ rods which are graphite rods that when inserted into the core of the reactor in amongst all the uranium undergoing fusion, slows down all the neutrons flying around - it slows the reaction down. When the rods are fully inserted like when they have to go to low/shut-down power, or in the case of an emergency (you may have heard the term \"scram the reactor!\"), the rods are pushed in fully. But the nuclear reaction is still going on, just very very slowly and doesn't generate anywhere as near as much heat as when the control rods are partially removed. Anyways, there's always need for _some_ steam from a ship-based nuclear reactor (i.e. to run the power turbines to keep the lights and pumps and stuff running) so even in low power mode they're still using _some_ of the power. A shipborne nuclear reactor never really \"shuts down\" unless you are either refuelling it (see nuclear aircraft carrier mid-life refurb) or you're retiring it for good. But it does have lower power modes where it produces just enough steam to run on-board power needs and/or any excess heat can be dumped overboard into the water. This is why you don't see nuclear powered commercial vessels despite it being a very economical way to power large ships - you need a full time crew of highly trained sailors 24/7 to man the thing and make sure everything is tip-top. More sailors (and security!) = high crew costs. Not so important to the military, but $everything to commercial shipping. Even tho, the change from low/standby power mode to \"running\" has to be controlled and gradual. This rapid uncontrolled change - combined with an inherint design flaw of the RBMK reactor - is what happened at Chernobyl. And even in low power mode, water still needs to be circulated, cooled etc. otherwise bad things happen."
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mg44lb | What is Marshal and De-Marshal in Computer Science ? | All of the function documentation on this particular feature tech not giving me any idea on how it is working. pls help da younglings | Technology | explainlikeimfive | {
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"Marshalling usually means that you take an object, and turn it into another format for use by another piece of software that requires the object's data to be formatted differently. It's really similar to serialization in that respect. You may need to give more details here for us to help you better."
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mg5y3p | Why is it recommended to not fully charge a battery for any device with rechargeable capabilities? | Technology | explainlikeimfive | {
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"A strange analogy that kind of works is a bucket made of ice. If you pour some water into it, the bucket of ice will cool it down and hold the water. If you pour more water into that bucket, the water will slowly melt the bucket. If you keep pouring water into the bucket to the point that it overflows, all that water will more rapidly melt the bucket. Bringing this back to the battery, the battery is comprised of consumable materials. The more you charge the battery, the more it wears down the consumable materials. This used to be more of a problem in the past where the chargers will keep trying to charge the battery after the battery is at maximum capacity. This is less of a problem in the present with advances in battery technology that cut the charge down once the battery approaches maximum capacity.",
"So the enemy of modern batteries is parasitic reactions. Shit reacting in the battery that you don't want reacting. Overtime these parasitic reactions causes a buildup in the interface between the high and low voltage electrodes and makes it harder for the lithium to move through the battery, causing the voltage to decrease over time. So what causes parasitic reactions? They basically happen constantly, but the rate depends on how energetic the things in battery are. That's mainly heat, and charge. If a battery is stored in cold temperature with low charge, there's very little energy for parasitic reactions to occur. If the battery is fully charged and hot, there's going to be a ton of random reactions happening because there's so much energy in the system. It's not even just about not charging to 100%, it's bad for a lithium battery to sit at 100% charge for long periods of time. For example my phone will try to automatically detect if you charge at night and pause charging at 80% until morning, then charge to 100%. That's to prevent the phone from sitting at 100% charge for too long. You run into other problems if the battery is fully depleted though. For long term storage the battery charge will drop slightly over time (this is also due to parasitic reactions) so the ideal charge level is around 40%, and the ideal storage temperature up to 10 °C. Still, you bought a battery and the best thing to do for it's longevity is to never use it. Even taking perfect care of it, it's still going to die eventually. At best you might be able to extend the life 2x. On my phone a battery replacement is $20, it's really not a big deal if you burn it out using the phone like you want. If you want to do something overnight charging to 100% is for sure the biggest cause of degradation, so just charge when you need to instead.",
"Heat is the enemy of your battery's health. The process of charging your battery naturally generates heat, but majority of the heat is generated closer to a full battery. Because of this, it puts considerably more wear on your battery to go from 80-100% than it would to go from 20-80% This is why unless you know you won't be able to charge your phone for a while, its better to do small top ups through out the day than just going to full every time."
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mg7l1h | How are metal forges made if you need to forge the metal they're made of? | Or rather how can equipment that's made to work with very high melting temperature metals be possible to make? And if there is some non metal material that is used for forging high temp melting point metals, why not just use it for everything? | Technology | explainlikeimfive | {
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"In simplest form, early forges were made of dirt and mud. So over time (copper age, bronze age, iron age) more complicated materials could be forged and forges were improved. I guess you could compare it to cooking, fire on the ground and now ovens in homes. You can still cook over an open fire and you can still forge with a dirt forge, but there are better ways.",
"A lot of answers here are talking about non-metals in forging, this is strange because that's fairly rare. Hot forging tools are basically very large hammers or presses, ceramics don't work great in this application because they are so brittle. They will fail by surface fatigue, spalling and other mechanisms. Most forging tools use what are known as \"refractory metals\". These metals are generally extremely hard and strong, and retain that strength at high temperature. So why don't we use them for everything? Well they are expensive as shit, not just because they're a rare element (they usually are though), but also because how do you shape and work and create tools out of something so strong and heat-resistant? Add to this the fact that they generally have some major downsides (brittleness, high density, corrodes easily, toxic etc.) and there really isn't any point making your water bottle out of a refractory hafnium-molybdenum alloy(not sure that's a useful alloy but w/e). Tools and dies for hot-working of steels are often made from molybdenum, sometimes tungsten alloys, and high-temperature steels(high nickel and chromium content) if you can get away with it. All of materials science is a game of compromise, there is no \"perfect\" material in terms of cost, hardness, toughness, cost, density, stiffness, cost, machineability, formability, hardenability etc etc etc. But steel comes pretty damn close. Edit: I wanted to add that careful design of a forging tool can allow you to use relatively poor refractories for the process. An anvil is a very simple forging die, you can work very hot metal on an anvil because it has a lot of mass, and the hot metal only contacts the anvil intermittently. You could (but shouldn't) make an anvil out of aluminium and work steel on it with some success, you will damage it a bit every time. This is true for all tooling, they are always consumed by use, these exotic refractories are only used because it is cheaper to use a more expensive material. Edit2: I think a few commenters are mixing up their terminology. A forge is where metal is shaped, the metal is heated in a _furnace_ which can easily be made out of refractory non-metals (bricks).",
"Ceramics are nonmetals that can take the heat of being a forge. Then, you take your metal out, and beat it into the shape you want. We don't use ceramics for everything for the same reason a spring isn't made of glass. It's way too brittle.",
"It's only until people start smelting iron that forging is needed. Metals like copper and bronze can be melted and cast into forms in order to get hammers, anvils, and other metalworking tools. Iron has to be forged though since melting it to make tools is impossible if the best heat you can get is charcoal. The first iron workers already had bronze tools to work the iron metal that came from the smelter. That works just fine since even though bronze loses strength and melts at lower temperatures than iron, the hammering and shaping isn't done in the heat of the forge and the tools aren't in constant contact with the hot metal which keeps them from heating up. The same idea is how we can use steel machinery to shape white-hot steel into whatever we want. The steel rollers, cutter, etc don't continuously touch the hot steel. Technically, the roller as a whole does, but any one part of it spends most of its time not touching the work material which limits how much it heats up.",
"In my country, people collected bog iron (reddish mud in the swamp that's rich in iron) and just smelted it in very primitive limestone ovens built next to the swamp during Viking Age. Access of air is more important than material the smelter is made of. Many rocks can take the melting point of iron. True, bog iron is easier to refine than mined iron ore because all the non-wanted stuff (mostly soil) simply burns off (they also hammered the pieces a bit), so there's that. Once you get iron, you can do whatever."
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mg9bvk | How does Stephen Hawking's speech "computer" work? | Technology | explainlikeimfive | {
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"The software that the late Stephen Hawking used was custom-built just for him, because nothing similar existed at the time. Now, however, this sort of software is available for just about any computer and it comes built-in on iOS, Android, Chrome OS, macOS, etc. The general category is called \"switch control\". The idea is that you figure out a way for a person with very little motor control to somehow manipulate a single \"switch\", which can mean pressing a button or whatever. Some blow into a straw, some wiggle a finger. Stephen Hawking had one cheek muscle that he could control really well, so he hooked up some electrodes to that. In a nutshell, the computer highlights one thing at a time, and when you get to the thing you want, you press the switch. It sounds tedious, but by carefully organizing things and with a lot of practice and patience you can do anything. Here's an example of using switch control: [ URL_0 ]( URL_0 ) You can use switch control with any app, but there are special apps designed to facilitate communication, called AAC apps. These apps basically let you pick words and then they speak those words for you using synthesized speech. While Stephen Hawking used 1970s speech technology and kept it because it was associated with him, today you can get very realistic sounding speech."
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mgg39k | What happens to my data if I ignore the "accept cookies" button on a website and continue to browse it? | Technology | explainlikeimfive | {
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"That message is telling you they use cookies or might use them, it isn't asking your permission. You are accepting that you read the popup. Some sites will close if you hit no/cancel, which is neat.",
"Depends on the website. Pro-Tip: Use U-block origin. It blocks many \"accept cookies\" buttons along with most data collection.",
"remember when there was this huge deal about privacy and they announced these new measures to control it better and all that? All we got was that annoying ''accept cookies or die'' message and changed absolutely nothing",
"I'm pretty sure it just continues to use cookies regardless of whether or not you accept it.",
"Well cookies are just a text-string in a key/value pair, so they aren't doing anything to your data. They're just storing temporary data about you, either to identify you should you visit again, to keep some settings about you in memory, or to store some miscellanous information that's better used on the fly than stored in the database (Lat/Lng coordinates can be one if you've used a location lookup for stores, as an example). Cookies aren't inherently malicious, and can't be directly traded/used between websites. It's when used in corellation with other code that they can be used to actually track you, but that's a active choice on the websites behalf, and it's only then that there's any kind of data exchange really happening (profiling you usually).",
"I've noticed on some online employment applications they ask my race, age, sex, and I will ALWAYS check \"prefer not to say\" because these questions are labeled \"optional\" and I don't give anyone any info if I don't have to.YET sometimes you can't continue until you fill in the \"required information\"- you know,the ones saying optional.Ive also seen the question \"Are you older than 45?\" Wait-- it's not illegal to ask a potential employee that? Yeah,I've been sending resumes out for awhile now.Its garbage, and I hate it.",
"Information Security student here, I started working with cookies in the browser this semester, from what I understand (but im no expert) there are different kinds of cookies. First of all, what is a cookie: cookies are locally saved data that the browser/website needs to keep track of, but can't/won't safe on their servers cause reasons. From what I know there are many uses for cookies, you have more essential type of cookies, for example the ones that safe the fact that you are logged in, if it didn't, you'd have to log in every time you do anything.... ather types of important cookies are anti fraud cookies etc. won't go into those now. usually when you only check essential cookies you only get these. these can be saved for a limited time, or very long. Cookies can also be used for ather purposes. most of the time when you have to accept them, you are dealing with third party cookies. these are cookies mostly used to keep track of behaviour, trends and intrests. see it as a automatic enquete. this info will be used by the receivers to get insights into their users, and also give you personalized ads and info. People are always scared that people are looking at your data, and even though I also try to avoid accepting cookies, I don't believe actual humans are looking at my data. It's mostly a digital process that will happen automatically and there is a very slim chance that someone is looking at your data specifically. though data is power, so if you don't like giving these parties your info for free, you have all the rights to decline these cookies. this is my take though, please add any missing info"
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mgkajl | How do computers use binary code? | I understand the basic layer of computation: computers work in binary signals (basically electricity/no electricity). But, what do they do with these signals? To what are they translated if so? What is the 'next layer'? | Technology | explainlikeimfive | {
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"The basic structure of a computer is the transistor. It's basically a switch that when it's turned on, it allows current to flow from the input to the output. The real power of transistors comes when you start wiring them together. Now, the output of one transistor can go to the control of another. That means that when you turn on transistor 1, it turns on transistor 2. By combining multiple transistors in specific ways, you can build simple logic circuits. For example, an AND circuit has two or more inputs and will only turn on if all of the inputs are turned on. An OR circuit will turn on if any of the inputs are turned on. From basic logic gates you can build calculation circuits. These will take numbers (in the form of binary) and add, subtract, multiply or divide them. These are the basic building blocks of performing useful operations on a computer. From there it's just building more and more complex circuits that perform more specialized functions. But, since the inputs and outputs are either on or off, 1 or 0, everything works in binary.",
"The wires that carry that electricity/no electricity signal are connected to transistors. The transistors are like electrical switches. You have a wire in, out, and a third wire that controls whether the \"switch\" is on/off. By carefully arranging these transistors you can build up circuits that behave basically however you want. In a computer, they create circuits to handle the binary signals as either a number or an instruction. Typically, when some binary is sent along input wires into a CPU or microcontroller or whatever, it's both. The first portion is the instruction, the second is some number. So you might see: 0010 0001 Where the first half 0010 stands for the LDL instruction (called the load literal) and the second half 0001 stands for the number \"1\". That entire line tells the CPU to take the number \"1\" and load that number into the register of the CPU (the register is a circuit that holds onto numbers that you want to do stuff with). The next question is usually, \"but how does the CPU know that 0010 means load a number?\" The answer is because it's built into the chip. We arranged the transistors so that when 0010 comes in, that's what happens. It's like \"how does a transmission know to convert the power from the engine of a car and send it to the wheels?\" The transmission doesn't know anything. We just arranged a bunch of gears so that that's what happens when you hook it up to an engine. If you want to go through all the layers of abstraction that are happening there's a lengthy series of videos by Ben Eater where he builds a very simple 8-bit computer from scratch, which you can find [here]( URL_1 ). I believe the only step that he doesn't show is building up the circuits like logic gates, latches, etc. from transistors. If you'd like to see a quick, intuitive analogy for how computers do stuff, there's [this video]( URL_0 ) where they build a very basic adder using dominoes instead of wires."
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mgmmhm | How does Apple manage to waterproof a phone that has ports, which, from my understanding, would be a way for water to make it into the device? Are certain ports easier to make waterproof? If so, is this part of the reason Apple decided to get rid of the audio jack on the iPhone 8 and on? | Technology | explainlikeimfive | {
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"A well-made jack or port can fairly easily be made waterproof. Electrical signals can pass from the outside to the inside without any openings at all. A well-made phone body can also fairly easily be made waterproof, though this wasn't always done in the past, especially with user-servicable parts. Remember when you could actually change the battery in your phone yourself, with no special tools and without breaking the warranty? Good times. But the ports create holes in the body. That's where the water is most likely to get in. It takes extra effort to tightly seal the crack between the port and the body.",
"Because the port itself can be water resistant. there is no reason that a charging port for example can't be completely solid, add gaskets around where the port joins to the phone and its very water resistant."
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mgorp5 | How does a program become "unstable" after running for long periods of time? | Title, how do programs (like server software and sometimes operating systems) become unstable and need to be restarted after running for long periods of time? Does the code simply stop performing the function it's supposed to? Why? | Technology | explainlikeimfive | {
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"Cooking recipes tell you to use all sorts of spices and measuring cups and utensils, but they never tell you to put them away when you're done cooking. They don't need to, because a normal person would clean up the kitchen after a meal and make sure that everything goes back to where it was, even if the recipe doesn't say that. Computers aren't as smart, and sometimes programs leave utensils lying around in the kitchen even when they're no longer needed, because the programmer who wrote the recipe forgot to tell the computer to put things back into the drawer. And if this goes on for long enough and measuring cups and tasting spoons accumulate on the counters, it becomes impossible to work in the kitchen at some point. When a program becomes unstable after a while, chances are it failed to clean up after itself after a certain operation, so it may be creating temporary objects without destroying them properly afterwards, or it may be asking for more and more additional memory without freeing up that memory after a certain operation has finished.",
"Imagine a small public library. At the beginning of the day, every library book is in its correct spot on the shelf, and everything is nice and orderly. As the day progresses, more patrons use the library. As they patronize the library, they are pulling books off of the shelves, reading them, and then putting them back. The library rules state that patrons must put the books back where they found them. As long as everyone follows the rules perfectly, the library will function at optimal efficiency. However, humans are not perfect. Sometimes, the library books are put back in the wrong spot. Other times, the books are simply left out in the reading area. As the day progresses, the library gets more and more disorderly. It takes longer for patrons to find their books, and the library becomes less and less efficient. It still functions, but not as well as it did originally. At the end of the day, the library is closed, and the employees clean-up all of the shelves and reading areas. In other words, the library gets reset to it's proper state. When it reopens in the morning, then it once again functions at optimal efficiency. Think about the library as your program, the library books as \"blocks of memory\", and the patrons as the programmers. As a program carries-out its tasks, it uses blocks of memory as needed. When it no longer needs the memory, it releases it back to the operating system. However, programmers are not infallible. In some cases, a program will consume memory and then fail to release it. This is known as a \"memory leak\". Restarting the program is like closing the library, cleaning it, and then reopening it. When a program terminates, the operating system reclaims all of the memory that it was using, and the memory leak vanishes. In a perfect world, programs will never have memory leaks. However, software is complicated and humans are not perfect."
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mgywer | Whats a Trace Route? | Technology | explainlikeimfive | {
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"Internet traffic is made up of sending packets of data from point A to point B. Part of that packet of data is \"number of hops\" which means how many things it can go through until an error happens. This is included to prevent packets being stuck in a loop forever. A trace route is a series of events to attempt to determine the path those packets take from A to B. You start by sending a packet that says \"I only want to go through a single piece of equipment otherwise return to sender\". That gives you the first step. You repeat this by increasing the number of allowed steps until a packet goes all the way from A to B and you build up a full sequence of steps. This entire sequence of steps is the \"trace route\"."
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mgznpv | How come most things that get plugged into outlets (charging cables and appliances), the plug has a hole in each prong? | Technology | explainlikeimfive | {
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"These holes allow the wall socket to hold the plug more tightly by having small bumps that can slide part way into them. Think of the holes as little handles that the socket can use to hold onto the plug.",
"It was a standard. Manufacturers have to follow the standard. It's not needed now, but people are used to it so get weirded out by ones without holes. They are not meant for putting a lock through to make unusable. It was likely originally a way to let them stay in the socket better, but that function is no longer necessary nor designed into sockets.",
"If you're referring to a NEMA 5 outlet that's common in the US, then those holes are often used for locking the plug so it can't be put in an outlet or locking it from inside the outlet so it can't be removed. It's entirely optional.",
"This video ( URL_0 ) seems to indicate that it was either/both a mechanism for holding the plug in and/or a way to differentiate one design from another when one design was already parented."
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mh6d6c | what is wifi ? | Technology | explainlikeimfive | {
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"Wifi is a wireless version of a network cable. Many people will assume it has to mean internet but that's not necessarily the case. Wifi is used in Amazon warehouses by the hand-held scanners people use to scan boxes and items. But that wifi on those scanners does not give them the normal internet. The way Wifi works: a device called a Wireless Access Point (which is sometimes included as part of a modem/router device) has antennas that send out (and receive) radio waves. These Wifi radio waves have specific radio frequencies, and it's those specific frequencies that dictate that it's Wifi and not something else. Certain frequencies can be the radio in your car, other frequencies are for cell phone data/voice service, other frequencies can be GPS navigation, and believe it or not, other frequencies are actually visible light... and so much more. URL_0 But back to wifi. So the antennas that put out waves, send them out into the air. People need wifi-capable devices to look into the invisible part of the radio spectrum that includes wifi, and find the signal. Then we can log in to the wifi network and connect to whatever the Access Point is broadcasting. It could be internet or any other network, even a person to person network including only two people. There's so much more I could say but this is already above a five year old's head probably and it gets worse from here.",
"In a word: light. WiFi is a brand name, it doesn't mean anything. WiFi describes a wireless standard that any manufacturer can implement to facilitate computer networking over *radio*. So a bit of background: microwave ovens. Some guy in the 1940s was working on RADAR for the military when he noticed a chocolate bar in the lab had melted. A quick investigation later, he found the radio waves emitted by the RADAR equipment excited water molecules in the food, heating it. The microwave oven was born shortly after. Microwave ovens are noisy devices on the radio spectrum. Manufacturers try to get by with as little shielding as possible to save on manufacturing costs. This became a big problem when practically every household in the nation got a microwave oven. Luckily, water is excited by very specific radio frequencies, so all microwaves make the same RF noise at the same frequencies. The FCC then allocated the 2.4 GHz ISM band, a range of radio frequencies where microwaves make their noise. The noise renders these frequencies effectively useless for commercial purposes as they're quite unreliable and full of noise. Therefore, they're left basically unregulated. The FCC is the commission in charge of, among other things, policing and regulating the use of radio frequencies in the US. They set the rules. And they say anyone can use these frequencies for *almost* any purpose, but they have to be tolerant of noise and other competing transmissions. So manufacturers LOVE the ISM bands, because they can make wireless products and not have to pay a dime for licensing. So there's a whole slew of baby monitors, cordless phones (are you old enough to remember those?), remote controls, and other gadgets that use these frequencies. Enter the late 90s and the boom of the internet. Naturally, someone was going to do this. We already have Ethernet, a standard of communication, and some of that standard explains how to communicate over coaxial cable and twisted pair, the 802.11 section of the standard goes on to explain how to generate the appropriate radio signals. Here's the thing about the electromagnetic spectrum: *there's only one*. There's only one 2.4 GHz ISM band that is 220 MHz wide. And to operate unregulated, your devices can only transmit using a maximum of 1 watt (which is more capable than you think). Your WiFi router is a lightbulb, the antenna is the element, and the light is invisible to your eye. At 1 watt, it's dim, but almost everything *solid* is opaque to it - this light literally shines through your house and your body with little attenuation. But not only is your router shining light, so is your laptop, your tablet, your phone, literally every WiFi (AND BLUETOOTH!) enabled device is shining light in this band. Every device that is in range of the emitting antenna is getting shined upon, and their antennas are receiving those signals. Every network is divided by an SSID - if you're not \"connected\" to that network, you still get all that traffic over the radio waves, your device just ignores it. Every message to or from one device to another, every device in range is getting rained upon with radio signals they're dutifully ignoring if it's not marked for them. This means the more devices in range, more specifically the more *active* devices all in range, the slower everyone has to go, because only one device can transmit at a time. It's like if you closed your eyes and turned on the overhead light and a desk lamp. Which light is from which source? All you see through your eyelids is light. So it doesn't matter how strong your signal strength is, if everyone is streaming Netflix, everyone is going to have a bad time. This is why you should spare your bandwidth and physically cable in every device you can. Have a desktop computer? Run a cable to the router, don't use a WiFi card. This makes laptop docking stations appealing again. Finally, there's a bunch of revisions to the standard, and they're all lettered. 802.11 is part of the standard document that describes WiFi, but there's 802.11a, 802.11b, 802.11ab, 802.11g, 802.11n... The list goes on quite a bit. They all use more and more bandwidth, even using *additional* ISM bands at 5 and 6 GHz, but at those frequencies, the light has trouble shining through paper, and they're really meant for line-of-sight across the room from the router to a media center. If someone walks in between, the signal drops. Just run a cable!"
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mh9er1 | What is the typing noises in the middle and at the end of robo calls? | For example, if you call hr block, you get a robot, after telling her where you want to go verbally, you hear typing noises. | Technology | explainlikeimfive | {
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"It's a \"spinning circle gif\" for your ears -- people are accustomed to hearing someone on the other end of the phone typing while not speaking, so they wait for a response. It's for a \"there will be a short wait\", versus being \"put on hold\" which means \"I have to wait a while\". It's a trick to make you keep listening, or make sure you don't think you've been disconnected.",
"It is a recording to try to make old people trust the robocall. People don’t like change. Think of it like a security blanket."
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mhao1v | - How would a scammer get a phone number? I’m getting spoofed calls from scammers, and it’s throwing me off, but one number that I received a call from isn’t associated with me at all yet. | Technology | explainlikeimfive | {
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"text": [
"I believe it depends on where you live but that phone numbers are listed publicly and it was fairly recently that cell phone numbers also got listed... I may be wrong tho I don't actually have factual information to present"
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mhaqrp | Why are drives/memory/disks with more storage not physically bigger? | Technology | explainlikeimfive | {
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"text": [
"They're standardies sizes, especially for hard drives and SSDs, so even if you could fit the same amiunt of storage in less space, manufacturers choose to use standardised 2.5\" or 3.5\" inch form factors to ensure they fit in every case. Same thing for SD cards, they need to be able to actually fit in the card reader so manufacturers can't just go making their own sizes."
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mhdozf | Why do websites need to verify if you are a bot? | Technology | explainlikeimfive | {
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"Imagine you work at the grocery store giving out cheese samples. The sign says \"one sample per customer\", but I'm a greedy cheese monster and I want a lot of cheese for free. & #x200B; If I know how to cheaply build robots which can convincingly pretend to be customers, if each and every one of those robots *counts* as a customer, then I can send an army of robot shoppers to take all your cheese! If you want to save your cheese for your human customers, you might start asking a skill-testing question to keep the robots out.",
"So that the resources they provide are not overwhelmed by automated requests. It adds a layer of security and throttling.",
"It's fairly trivial for a programmer to create a script that automatically fills forms. If there was no validation, anyone could create infinite accounts or send contact forms with garbage data and eventually either exploit a promo for new users or crash the server by making it use lots of resources. There are many other possibilities but the main purpose is to stop automatic bots from exploiting the system. Not that a captcha makes it impossible but it does make it harder for most cases.",
"Every time you visit a webpage, a server has to spend a small amount of computing resources sending the page back to you. That's cool; most websites will rarely have too many visitors at once, and those that do will have the server capacity for it. But now imagine you run a website and someone had a grudge against you. By using an automated piece of software (that's what we mean by a bot here, not a literal robot), they could request so many web pages from your server that those small amounts of resources add up and it's using so many resources to respond to those requests that when someone legitimately wants to view the page, the server doesn't have the available resources to show it to them. This is called a *denial of service* (DoS) attack. In reality, this generally happens with many computers, often infected with malware to make them all send requests to this server, in which case it is called a *distributed* DoS attack, or DDoS. So human verification is a way to prevent that happening. Of course, some sites have additional reasons to not want bots, such as social networks, where bots could be used to manipulate the numbers of likes etc."
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mhfihk | Why is GPS free to use? | Technology | explainlikeimfive | {
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"In the states here, it's taxpayer funding. I guess I have to go to a quote. \"In 1983, Korean Air Lines Flight 007 entered Soviet airspace after a navigation error and was shot down, killing all 269 passengers. This incident resulted in President Ronald Reagan ordering the Unites States military to make the Global Positioning System available for civilian use once it was completed, so that similar incidents could be avoided in the future.\" [Here's where I got it]( URL_0 )",
"GPS satellites broadcast, they don't communicate. So there's no extra cost to adding a new GPS locator, any more than there's extra cost to seeing up another TV or radio to pick up local broadcasts.",
"The satellites are in orbit anyway (for military purposes), usage only requires processing capabilities on the *client* side and having large swathes of infrastructure world wide rely on US-owned military equipment gives the US government an **enormous** amount of leverage. There is no reason *not* to offer free access.",
"GPS satellites broadcast a signal, and any number of devices can listen to it. It is infinitely scalable, because the same satellites can serve one device or one billion devices without even knowing it themselves. The US government originally put in the satellite system for military purposes, but has since opened it up to the world."
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mhojo2 | How do people upscale 24/30 FPS animation to 60 FPS ? | Mostly talking about in some anime openings and edited scenes, like this one URL_0 . Do they really go in and draw extra frames, or is there a program that just adds in extra scenes? | Technology | explainlikeimfive | {
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"The easiest would be just copy and paste previous frames. There are also programs that does motion smoothing and would fill in the frames in between. This is known as the soap opera effect."
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mhpa0t | The difference between RGB and RYB. | I always remember learning that the three primary colors are Red, Yellow, and Blue. Many people rather insist that they are Red, Green, and Blue. When you take paints or markers or something else along those lines, combing RYB will give you all the colors, whereas RGB will not. Furthermore, electronic displays and lights use RGB as their primary colors, not RYB. So what exactly is the "true" set of primary colors. Or are there just two sets that function differently? | Technology | explainlikeimfive | {
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"There is no RYB: printers use CMYK (cyan, magenta, yellow, black). Kids get taught that it's red and blue because those are familiar colours but the technical names as magenta and cyan. CMYK is the system for use with paints and inks, i.e., for subtractive colour mixing. You start off with a white canvas and each layer of paint subtracts a colour: * cyan + magenta = blue * cyan + yellow = green * magenta + yellow = red * cyan + magenta + yellow = black (but not a very good black, so we use black ink) If you're starting off with a black screen and using light to add colours, then you use RGB (red, green, blue). This is additive colour mixing as used on computer monitors and TVs. * red + green = yellow * red + blue = magenta * green + blue = cyan * red + green + blue = white So there are two completely different (in a sense opposite) sets of colour primaries: additive and subtractive. The one you use depends on how you're creating colour.",
"It's a different function. If you're talking about additive colours, as are used on your computer display, then you use RGB--red and green together will make yellow, etc. For printing, the colours are subtractive (they're absorbing some part of the incoming light), and the base colours there are actually cyan, magenta and yellow, not blue, red and yellow.",
"Primary colors are simply any set of colors that can reproduce all other colors by mixing them. The way of mixing defines what colors are primary colors. In paint the way of mixing is subtractive as each pigment of paint - absorbs - \"all but one color\" so a red pigment absorbs all light quite good except for red light which is reflected back to you, thus you see the paint as red. So when mixing paint together more colors are absorbed, thus more colors are subtracted, from the color pool. Due to this behaviour the primary colors of subtractive color mixing of paint in art and design are Red, Yellow and Blue. (This is not the whole spectrum though) However everything that - emits - light mixes by - adding - colors to the pool. So a red light emits \"only in the red\" and a blue light \"only in the blue\". Thus wenn mixing them together you receive blue and red data. So this way of mixing is - additive - and here the primary colors are Red, Green and Blue. So to say \"those are the primary colors\" without mentioning the way of mixing is simply wrong. The definition literally states \"any of a group of colours from which all other colours can be obtained by mixing\". Thus there are no \"real\" or \"unreal\" primary colors. It simply depends on the way these colors are mixed and if all other colors can be obtained. So in the end what colors are considered primary depends on the so called \"color model\". The most common ones are the paint (subtractive), light (additive) and ink (subtractive) models.",
"Primary colours is basically just a set of colours that produce some *gamut* of colours by mixing the primary colours. This means that basically any set of colours can function as primary colours for the gamut that these colours may create. You can technically even have only two or one primary colour for a gamut, although that would be pretty useless (in the case of only one primary colour, the gamut would consist of only that colour). One important fact to note is that it is practically *and* theoretically impossible to create *all* colours from a finite set of primary colours. So no, there are no 3 (or any finite number of) colours that can create all other colours. Any colour gamut is fundamentally arbitrary, but we of course try to create gamuts that cover as much of all visible colours as possible using the technology we have. RGB is often used in screens becasue it covers a large amount of the visible colours and we have the technology to create red, green and blue pixels using e.g. liquid crystals (LCD) or LEDs. Take a look at this review of an LCD-panel over at Rtings: [ URL_1 ]( URL_1 ). Here, they look at at how well the monitor covers at least 4 different colour gamuts, all of which are a type of RGB-gamut (since the panel has red, green and blue pixels): SDR gamuts \"sRGB\" and \"Adobe RGB\", and HDR gamuts \"DCI P3\" and \"Rec. 2020\". Of these gamuts, Adobe RGB is wider than sRGB, i.e. it covers more colours. Similarly, Rec. 2020 is wider than DCI P3. Regarding human vision, we have three colour photoreceptors. Contrary to popular belief, each receptor can actually \"see\" more than one colour. Each receptor responds differently to different wavelengths, see this picture from wikipedia: [ URL_0 #/media/File:Normalized\\_Cone\\_Sensitivities.png]( URL_3 ) Take a look at the L-receptor. It responds most strongly to yellow, but it also responds \"sees\" red and green, and even blue although very weakly. Depending on the responses of the three receptors, our brain constructs an image in our minds. But again, there are no \"true\" primary colours. Animals may have different, or even more, photoreceptors, which for example allows certain birds to see ultra-violet, i.e. colours that humans *cannot see* at all. As others already have explained, creating colours from primaries also function differently depending on whether you use additive mixing (you produce light using some sort of lamp, e.g. a LED or LCD) or subtractive mixing (you remove light by adding e.g. ink/paint). Note that additive mixing is in a sense independent, i.e. the lamps you use shine with the colours that they shine, period. In subtractive mixing, you have some light source (e.g. the sun) that shine on your painting or whatever. The light from the sun is a mix of colours, and then you add paint to *remove* some of the colours from the light so to speak. This means that the colours you get depend on the colours existing in the light from which you remove colours, and also their relative intensities. If you swap the sun for a blue-ish LED-lamp, the colours of the painting will look different even if you have the same paint on it. Basically, a red painting only looks red as long as the light source shining at it actually contains the colour red (or some combination that the human brain would percieve as red). Here is a link to the rather good wikipedia page on primary colours, which I base a large part of my answer on: [ URL_0 ]( URL_4 )"
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mhq4ny | what is happening when old school box televisions mess up and you slap em' up to fix them? | Technology | explainlikeimfive | {
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"Older TVs had more electrical connections that were susceptible to oxidation resulting in poor contact. Smacking the TV created small movements that would break through the oxide barrier or otherwise help restore solid electrical connections.",
"Good old percussive maintenance! A connection gets loose or otherwise degrades. Giving it a jolt can sometimes reestablish those connections. They're big and flexible, which is why they got loose in the first place. Why doesn't it work now? The connections are less likely to get loose or degrade. They sometimes break, but slapping won't help that. Why? Less heat, so damage is less likely. Different kinds of connections - modern electronics have small, rigid chips soldered, at several points, to rigid circuit boards. If a solder point breaks, it's because something is pulled it apart. A slap won't stop the pulling. Plus, in a high-speed system, an imperfect connection may not work at all because of capacitance; it's often not enough for the metal to just be touching, it needs a clean enough connection that charge doesn't build up around it. So even if an angry right hook could make the pieces touch, they would fail anyway."
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mhruie | Why do phones have a camera bump? Is it a hard problem to solve? | Technology | explainlikeimfive | {
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"There are fundamental physical limits on image quality with miniscule lenses and sensors, so we can't just shrink them down and improve our lens/sensor tech - unfortunately physics doesn't allow that. So for good image quality, especially in low light, we have to make the sensor and lens a certain size. For a given lens size & sensor size, there is a practical limit to how thin you can make the arrangement based on how quickly you can bend light using glass to focus it on to the sensor. We could make thinner cameras if we could find better optical materials (we would need transparent materials that can bend light more). Things like diamond or moissanite are incredible at bending light, unfortunately they have other undesirable optical and physical properties which makes them poor choices in lenses. Sapphire could potentially be used, but it's only very slightly better than the best glasses.",
"Because phone manufactures want to have good cameras and thin phones, and good cameras require larger sensors and larger lenses, which don’t really fit in the thin body of the phone, so they make a bump If manufactures didn’t care about being that thin, they could easily put a larger battery and bring the phone thickness up to the camera bump, but they don’t want to do it"
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mhvl69 | what does my ISP know about me ?? | and is there any way that i could minimize its "knowledge"? | Technology | explainlikeimfive | {
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"In this day and age, here's what your ISP can see. First, they can see your DNS requests. When you access URL_0 , you have to make a request to know which IP Address URL_0 is. DNS is a plain-text protocol, so your ISP sees all that. Second, they see the amount of traffic coming out of your modem, and the destination IP/Port of that traffic. If they know you access an IP associated with URL_1 on port 443 and download 800TB of traffic from it each day, they know you're downloading a lot of data via HTTPS from URL_1 , even if they can't see exactly what it is. Third, for any website that doesn't use HTTPS and just uses HTTP, they can see everything you access on it. They can see the specific page you're requesting, they can see anything you enter in a form and submit. As for other comments who say \"Just use a VPN\" -- all you do is move the problem upstream to the VPN. At some point your traffic goes over the public Internet without any additional encryption beyond the protocol (i.e. HTTPS). You're just changing who you decide to trust.",
"If you don't use a VPN all the time, your ISP knows everything you do on the Internet. If you want to minimize this, you should use a VPN. Then your VPN vendor will know a lot about you. Maybe it would be better not to do what you're doing online??"
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mi2rom | why do phones battery discharge slower when the phone is fully charged? | Technology | explainlikeimfive | {
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"I assume you're referring to the fact that the drop from 100% to 90% take longer than 20% to 10%? Firstly, there's definitely a part of it in your head/due to useage. Another part is the phone never really knows how much it has left. It's an estimated guess usually based on the voltage detected. Accurately measuring battery capacity is something every device struggle with as it's difficult to do. Voltage drops off much more quickly when it's near the end, which can contribute to difficulties and seemingly dropping % faster at the bottom.",
"It doesn't seem like they discharge slower or faster based in how much charge it has, I think it may appear that way because when it is low you are constantly thinking about the battery, but when it's full you aren't and won't notice it going down."
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michi9 | How do kettles know when to turn off? | The electric ones, not the ones with a whistle | Technology | explainlikeimfive | {
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"They have a switch made of 2 different metals which expand at different rates. They're designed to move away from each other at boiling temperature. When they push away it opens the electrical circuit and it turns off. As they cool, they return to the original position and you can turn it back on."
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mig82d | why do computers (motherboards) still have ps/2 ports by default, but no such keyboards or mice have been made in at least 20* years? | Sorry if wrong sub, couldn't think of where else to ask. *To my knowledge - not meant to be hyperbole, i think I'm probably underestimating here. | Technology | explainlikeimfive | {
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"All modern computers are built to the ATX standard in order to be compatible with all the hardware and software built for this. This means that they need all the components in place that is expected on the IBM 5160 from 1983. This includes things like an ISA bus and the PS/2 keyboard and optional mouse. Most motherboards are however capable of emulating their own keyboard from an USB keyboard but it does not cost much to put the connectors in place as well. Of course not all motherboards have them but they are quite common. Another use case is in server rooms where you often have quite a lot of infrastructure in place to extend the Keyboard, Video and Mouse cables from all the servers to the operators. And this infrastructure often standardize on PS/2 and VGA. So in order to sell servers you have to have these ports in place to fit the existing infrastructure.",
"Mostly it's special use cases. Some point of sales equipment still uses PS2. Some manufacturers still make PS2 keyboards. Ie. URL_0",
"Fun fact - the last update on my Windows decided that it doesn’t need USB anymore, so I couldn’t log on, because neither USB mouse nor USB keyboard would work. After spending some hours I ended up with having to order a PS/2 mouse, because nothing else helped (I really was not up to reinstalling the system altogether). So I’m actually glad the computer at least had that port."
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mijlrn | What is the role of Cache in a CPU? | I’ve noticed some new processors have a difference of 16mb cache and 8 mb cache (I think), but I don’t what cache even does 🤔 | Technology | explainlikeimfive | {
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"It's so the CPU can store a little bit of information without having to read it from RAM every time.",
"Think of it as super-ultra-fast RAM. RAM is already fast, but it's still not fast enough to keep the arithmetic and logic cores of the CPU fed with data. The solution is to put the data you're using right now into an even faster storage, which is the cache. It's on the very same chip as the CPU itself, and therefore extremely fast. And since you're only storing data there fore very shortly, it doesn't need to be that big.",
"It’s a buffer, temporary memory that is faster than ram, because it’s physically in the CPU, this way the CPU can keep more commonly used stuff is die the cache rather than the ram and it’s able to go faster, but the catch is there’s not much of it, so the more the better (however there’s finishing return) The problem is it’s expensive to make the CPU larger, so cheaper CPUs tend to have less cache",
"Cache is similar to the memory (RAM, not disk): it stores data that the processor may need at tht moment. The larger your data storage is, the slower it gets: HDD or SSD is horribly slow compared to RAM, RAM is horribly slow compared to processor's registers directly inside the CPU but the latter can only store a few variables. If a processor requests data from RAM and has nothing else to do until it's delivered, it stops. That. of course, reduces performance. So, we can get a small but fast piece of memory, call it a cache and store some data from RAM that is used most often. Processors today have several levels of cache, getting progressively smaller but faster.",
"RAM access takes time, because it's far away on the timescales of CPU computation. Typically, when the CPU needs to read a value stored in RAM, it will need to wait 100 to 400 cycles for it to arrive. When you consider that a CPU is supposed to make (approximately) one operation each cycle, waiting for a hundred ones while doing nothing is a massive problem for performance. That's what the cache is for. It provides a much smaller space to store things, but with much faster access (1 to 20 cycles depending on the cache). Cache is part of the CPU chip so is much more expensive than RAM for the same memory, but is much faster to access. As a result, the CPU stores the currently uses data in the cache to speed up operations. Any time it needs a value not in the cache, it will request its value from the ram, and will keep it in the cache in case it needs it again. Once the CPU runs out of cache space, it will take the oldest values in the cache (the ones it hasn't accessed for a long time), and will write them back in RAM, making space for other values. As a result, the more cache you have, the more data you can keep close to your CPU, and the less you have to perform longer RAM access operations."
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mil65x | How are RFID tags read with antennas and readers, and how is the information sent back and analysed by a computer? | Technology | explainlikeimfive | {
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"An RFID tag is really two parts - a small chip and an antenna. When a reader scans the tag, it supplies a small amount of power over the air. The antenna picks up that power and it is _just_ enough to activate the chip. The chip then broadcasts a message, which the reader receives and stores. It then takes that message and compares it to a database to achieve the desired output, be that firing a command, pulling up a record, etc."
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mil6bx | Why emulated ps2/ps3/x360 games still run horribly on newest CPUs? | Technology | explainlikeimfive | {
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"In order to run the games themselves, emulators need to also simulate the hardware the game runs on. Sometimes this can be as simple as translating some CPU instructions. Other times it can mean using CPU power to simulate a whole other CPU. In the worst cases, like with some old arcade machines, this can mean running complex physics simulations to reproduce analog hardware components.",
"Software developer here, There are big physical, structural, and conceptual differences between processor architectures. It's not so easy as map the ADD instruction from that CPU to this. The fundamental differences have damning consequences. Most common emulators do try to map instructions, and try to implement feature and architectural differences as performant as possible, but whereas the original CPU was doing work in hardware, your emulator is taking more steps having to do it in software. The best emulators will emulate the actual physical hardware circuitry itself, including signal propagation and latency. These take massive amounts of compute power to run, what your typical CPU can't handle - it doesn't matter how many cores you throw at the problem. The best desktop CPUs today can emulate original NES hardware this way at its original speed.",
"With the exception of a few games pcsx2 runs very well. You do have to acquire bios file though.",
"Some analogies that might help: * Imagine being dropped in a foreign country with no knowledge of the local language, and only a Google Translate app at your disposal to facilitate communications. That app is doing the work of an emulator. * Imagine a top-ranking F1 driver suddenly being told to operate a forklift with no prior training. Luckily, there's an owner's manual. A fully-functioning emulator requires an understanding not only of the CPU, but also of all of the related specialized hardware (e.g. SPU). Much of that information is a trade-secret and won't be available for programmers to research, so a lot of it ends up being best-guess approaches. Meanwhile, these games may have been built to take advantage of system quirks or low-level optimizations that might not function appropriately in an emulated environment. All of this is being funneled through a layer of indirection. A naive approach to emulating a CPU's instructions would be to have an entire function of native code to make sense of a single instruction, which could have several orders of magnitude more work involved than the original platform. I'd liken it to that scene in Apollo 13 where the astronauts are losing the CO2 scrubbers, and the engineers on the ground are trying to figure out how to reproduce the problem on their side, solve it, and somehow communicate it all back to the flight crew.",
"Usually a console has a very very very different type of CPU and GPU and it doesn't just translate and run, but has to run inside a simulation of the real console, which is very tough to do especially for more recent and powerful multicore specialized console CPUs. SNES emulates perfectly by now, because desktop CPUs are 500x faster than the old 16-bit things. Some day when desktop CPUs are 500x faster than an IBM/PowerPC or MIPS or whatever thing (currently only like 2.5x or so) then those consoles will emulate smoothly. Sometimes there are very undocumented things which need reverse engineered and since most emulators are not well funded that work takes much longer, almost as long as it takes for the CPUs to get fast enough. DMCA complicated things even more since reverse engineering is essentially illegal, even if just for kicks.",
"Because the emulator is not optimised. It doesn't matter if you have a super powerful CPU with infinite multithreads if the program you are running (the emulator in this case) isn't programmed to utilize the CPU resources. Imagine you have a 10 lane super high speed freeway. But all the drivers have been taught to only drive 50 km/h (30mph) and only in the right most lane. Then you will still have slow traffic even if there is a lot of space you can use. The emulator is kind of the same. Unless the programmer specifically has programmed the emulator to run on multiple threads or to utilize as much memory as possible etc then it will still run poorly.",
"Emulating the actual game code is the relatively easy part. PS2 for example is a MIPS CPU. which has a handful of very simple instructions. Some emulators will convert the game instruction set into native x86 assembly instructions, which can make the game code run fast enough. What is more difficult is all the support chips (sound, GPU, vector multiplication) that need to be emulated. Even with a GPU in your system, there needs to be translation done between the graphics commands from PS2 games to the GPU driver on your system. Keeping everything synchronized is a challenge as well, as your CPU likely will not run at the same rate as the game console."
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min6c7 | Why do different countries have different power outlets? Is it on purpose? | Technology | explainlikeimfive | {
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"Countries didn’t all develop their electric grids together, they were slapped together independently in the late 1800s and early 1900s. Eventually the entire developed world was electrified, but you had a problem at the borders - they hadn’t all selected the same voltage and frequency for their grids. Some had picked 50Hz, others 60. Some were at 200V, others were at 110V. Plug in a device that’s expecting the wrong flavor of electricity and it might explode. Rather than tear down their entire grid and start over, countries just made sure their plugs were unique so you can’t plug in a Russian toaster in Boston and burn the house down.",
"They have different power outlets because there is no universal, global authority on what power outlets should look like. So whenever a country implemented them, they just came up with whatever design they though was appropriate.",
"There is the IEC 60309 standard, best example is the blue 'Caravan Mains Socket' you see in campings across Europe. The red socket is standard use in three phase power network in theatres, events and construction work. URL_0"
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mioely | the Hubble Telescope - how does it take the high definition space pictures that people post all the time? | I keep seeing all these high definition renderings of galaxies over my feed with the caption that says Hubble Telescope but I’ve never questioned it until now. Are they really photographs and if so how are they generated? Is the telescope like a really good camera? | Technology | explainlikeimfive | {
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"Well the camera isn't particularly super amazing, or the optics super amazing at least compared to earth telescopes other than that it's designed to work in space. In space though you get some really really major benefits from not being in atmosphere. The downside of being on Earth is that air doesn't transmit light perfectly. Different temperatures of air moving around in particular wiggle light around. (Side note this is why stars twinkle). This makes long exposure photographs end up blurry. The amount of sharpness you can get from a photo depends on how well you can compensate for that. With Hubble you can take ridiculously long exposure photographs of dim things and be able to combine them together by referencing some brighter nearby star for aligning the multiple images, with essentially zero loss in sharpness. For example the total exposure time for the hubble deep field was 22 days.",
"They are data collected by the telescope and then processed by people on the ground. The telescope operates in a number of frequencies of light, and most of the processing is mapping those colors into colors that look attractive. Where the telescope points and what it takes pictures of are managed by the [Space Telescope Science Institute]( URL_0 ) in Baltimore, who will also operate the James Webb telescope. Scientists make requests and describe why that collection would be a good idea. The data in generally available to all.",
"It's called a telescope, but it's not like there are humans up in space looking at the image that comes in through the lens. Images are captured digitally, just like any phone camera, then transmitted to earth. Pics are different from anything that can be seen from earth, because the light isn't filtered through the thick atmosphere."
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miqjym | What happens with a video is taking a long time to load and the circle keeps spinning? | What goes behind the scenes? | Technology | explainlikeimfive | {
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"When you're watching a video, there is a connection between you and the server. Let's use youtube as an example. YouTube will start sending data packets to you. These packets contain tiny bits of the video you want to watch. Since the internet is unpredictable and unstable, a buffering system is used. Ideally, the packets will arrive faster than the video playing speed and get stored until it's their turn to be used, so you can watch without any interruptions. However, what happens if the network is slow, and the video speed is greater than the packet sending speed? Well, the video obviously can't be played if there are no packets arriving. So the video has to pause, wait for more packets to arrive, then continue playing."
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mirqc5 | How do game servers handle millions of persistent connections at the same time? | If there are a million gamers connected to a server, are they connecting to one computer or something masquerading as one computer but actually many? Are the connections "held" open for each player through out the session? Once a player connects to a particular physical server, do they always connect to the same server during the session? Does this server (or many servers) communicate to a database on a single computer or again, many masquerading as one? (Also, how much data is transmitted during say, a 1 hour session of an MMORPG?) | Technology | explainlikeimfive | {
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"MMOs are made up of a large number of servers. Looking at World of Warcraft, each 'realm' that you can join is a separate server. You can also have different parts of the same 'realm' hosted on different servers. In Eve Online for example, there's only one 'realm' to join, but various star systems are hosted on different servers, so as you move around you'll be moved onto different servers. The databases would also be duplicated and split over various computers for redundancy and whatnot. Amount of data transmitted and the nitty gritty of server architecture will depend on the game in question.",
"No server handles the gameplay of millions of gamers at the same time, the game client will reach out to a server, which will tell the client which game server to connect to. Most mmorpg will use geographic areas to break up its main server farms (to reduce latency), Then they split it up further into instances, which usually have 20-50 players around in most areas, (mostly for quality of gameplay then technical limitations). Those instances are usually virtual computers that run with a small percentage of a large powerful servers hardware. Allowing multiple instances to run on a single hardware server. In recent event's there was a huge battle in eve, where a few thousand people joined into one instance which pushed the hardware to the limit, causing that one area of the game to have terrible performance, the game developer's said that when the hardware is pushed to the limit, that unpredictable things happen to players/ships, but they allow this. Other games like wow and destiny do not allow the server hardware to become overloaded to protect the game play."
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misqo8 | what are mosfets, and are they interchangeable with transistors? | Technology | explainlikeimfive | {
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"Mosfet is a type of transistor. Mosfet stands for Metal Oxide Semiconductor field effect transistor. They are generally considered superior in most applications to the main alternative, known as the Bipolar Junction Transistor (BJT). Field Effect Transistors (FETs) are a kind of transistor that work a bit different from a BJT. Field Effect Transistors kind of work like capacitors, where the gate itself behaves kind of like a capacitor, and when this capacitor is charged or discharged determines when the FET conducts between its source and drain. The cool thing about a FET is that it requires very little current to get going, you just have to charge the gate capacitor and at that point you don't need more current beside to supplement capacitor losses to maintain the channel between the FET. The field effect here is the whole capacitor thing, referring to how capacitors store charge by creating an electric field across two plates disconnected from each other. The metal oxide part refers to the dielectric between the gate and body of the transistor (remember, capacitors contain two conductive regions separated by a dielectric, something that does not conduct). Typically dielectric is silicon dioxide, putting this between the gate and body of the transistor creates the capacitor we want with our mosfet. Why silicon dioxide? Because we are making these devices on big slabs of silicon anyways, we just have to add oxygen in the right places and everything works."
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mit6wl | How are ISPs able to handle internet traffic coming from so many different places at once? | Technology | explainlikeimfive | {
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"Think of the photos you've seen of old manually operated telephone switchboards. Now take that, expand the size and connections by several orders of magnitude, and shrink it all down onto specialized silicon chips, dozens or hundreds of which are packed into each physical switch and router. Then, these specialized switches and routers use light, as in fiber optics, to transmit data. Then, there are many, many nodes containing all this data transmission gear distributed across a global network. There is a hierarchy, principal nodes to secondary ones and tertiary, to route the data to where it's supposed to go. All of this happens at the speed of electricity, so, for our intents and purposes, light speed. So, in summary, they use specialized switches, fiber optic cable and lots and lots and lots of both to handle the traffic. Hope this has helped!"
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mitd58 | Why is printing sutff the hardest thing to do half the time with my printer? | Like, am i just dumb? | Technology | explainlikeimfive | {
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"you didn't buy a Brother. no one should let a brother buy something other than a brother. fr.",
"I doubt you are dumb. It is most likely your printer. I found the ones that the paper is flat in a drawer work more consistently. The ones where the paper drops down have more problems. In my case, the flat drawer is a laser printer and the drop down is a color inkjet."
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mj4k0m | Why are rechargeable batteries only 1.2V? | A lot of devices expect 1.5V batteries and report 1.2V rechargeables as empty sooner. Wouldn’t it be better to make rechargeables 1.5V as well? What is preventing that to happen? | Technology | explainlikeimfive | {
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"The voltage generated in a battery is due to specific chemical reactions between the electrodes and the dielectric. This is more or less predetermined by what the battery is made of. There are other features more important in a battery - safety, reliability/rechargeability, size and energy density, current carrying capacity, cost etc. Modern commercial batteries have to optimize the above. The voltage is a very very minor issue ultimately because voltages are easily and efficiently adjusted by external circuitry. There is essentially no point to making a battery $10 more expensive just to try to eliminate $1 worth of external circuitry.",
"It's because of battery chemistry. The voltage of a battery depends on the 2 reaction partners inside the battery. While the material used in non rechargeable batteries is delivering a higher voltage, it is reacting in a way that can't be reversed (you could recharge it theoretically, but you cant do it often, and it's VERY DANGEROUS so DON'T do it.). A rechargeable one is like water ice. You can melt it, and freeze it back without quality loss. A non rechargeable battery is like ice cream: you can melt it, but if you try to freeze it back in, it's becoming a hard block of frozen milk. But sometimes you just want Ice cream and not an ice cube. So you have both. Why electronics need that bit higher voltage? I honestly don't know. It may be a spacing/comfort/engineering reason. Maybe a monopoly. That's a question to another person.",
"The choosen battery materials define its voltage and through packaging batteries together you can only end up on integer multiples of this voltage. Rechargeable batteries use different materials than none-rechargeables which leads to the difference of 0.3V. So it would either be 1.2V or 2.4V for the rechargeable.",
"Voltage depends on the battery chemistry. Though alkalines run out of energy around 0.8v, and most 1.2v rechargeables provide all their usable energy by that point as well. It's possible your device has a cutoff voltage too high even for alkalines, or your rechargeable batteries just have a very low energy density. Are they NiCd?"
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mj87f9 | how do robots in car factories get programmed to do tasks such as placing a door on a the car. Does a human record the actions first like a macro or are the actions written in code. | Technology | explainlikeimfive | {
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"Both ways are used. You can preprogram them, but there are also methods where a human operator moves the robot arm in a training phase to get it to the right spots and initiates the necessary action. I don't really know how common the latter is, but I have seen it done for spot-welding robots. The robot saves the path and action information and repeats it then.",
"A macro is also code, and code is what it comes down to. A robotic arm can perform a number of set movements simply by following programming that tells it to \"turn joint A by X degrees, extend piston B by Y cm, release gripper C\"... etc. The exact details are fine-tuned to the particular requirements at any given point of an assembly line."
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mjar18 | Where is the bottleneck for the max speeds ISPs can provide? | Why is gigabit internet feasible in some areas/countries while 100Mb/s is premium in others? | Technology | explainlikeimfive | {
"a_id": [
"gt95oo7",
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"text": [
"Some areas just don't have the infrastructure. Every single line of fiber or copper has a maximum thruput that has to satisfy every person using that line: Maximum thruput / number of customers = average max speed for each customer. To increase that, you either have to lay new lines (which is expensive - laying fiber costs between $8,500-10,000 per mile) or have bottlenecking issues when you have a ton of customers on line at once. Now, that said, much of the time the bottlenecking is artificial. ISPs without competition can reduce speeds well below their max thruput because consumers don't have a choice but to accept that due to lack of competition.",
"Their ability, or willingness due to profit margins or competition, to invest in infrastructure. Faster speeds require each customer to have a more expensive modem, they require infrastructure to reasonably be able to maintain those speeds for thousands of customers at once. 1gig is usually the highest you see because most consumer hardware can't handle more. Commercial customers can get terabit in many locations. I have an old picture of a 900GB/s internet speed test from a place I worked."
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mjknzx | Why do cell towers need to be so high and large but our cell phones can reach them at ground level with a tiny antenna? | Was just driving and had this though whole seeing some cell towers. We create these giant towers in order to broadcast over a large area which makes sense. But I started to come up short when thinking about the process in reverse. When we send a command from our phone to retrieve data or even make a call, how is it that our tiny phone can reach these towers over such a long distance with much more meager equipment? | Technology | explainlikeimfive | {
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"The cell tower isn't necessarily broadcasting stronger signal (it's usually stronger, but not by much). It's high because that's how you get a direct line of sight to the most of the phones on the street. The signal can also reflect off walls or penetrate walls, depending on frequency, but the more it reflects, the worse it gets. The other reason is that the cell tower needs to serve many phones at once. The cell tower can do it over wide range of frequencies, but the phone usually sends data back over few narrow frequencies. So the cell tower needs more power, because it sends many signals to different phones at once. But the signal levels that each individual phone is receiving and sending are not different by much. The difference is mainly because the cell tower has bigger antennas, and bigger antennas can catch more signal, so they can receive weaker signal and still process it correctly. And you will absolutely get a better signal if you raise your phone up high, so that no walls or trees obstruct the cell tower. But it's impractical to carry 3 meter long antenna on your back, so they make cell towers higher to compensate.",
"The logic goes both ways. Just as it is easier for something high up to send out signals to greater distances on the ground, it is also easier for something high up to receive signals from a larger area on the ground.",
"Your phone can talk to the cell tower BECAUSE it's so high up and easy for your cell phone to send/receive signals to. The tower is high up because it needs to talk to phones that are spread out all over the city. Your cell phone doesn't need to have a tall antenna because it ONLY needs to talk to the very tall cell tower which is easy to send signals to."
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mjlmc2 | How do phones know to turn back on when yoi restart them? | like when you turn it off, it'll stay off until you manually turn it back on but if you hit restart instead of power off how does it just know to turn back on? | Technology | explainlikeimfive | {
"a_id": [
"gtaw7l5"
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"text": [
"There is what is known as a BIOS ... a \"Basic Input/Output System\" which runs alongside the operating system (Android, iOS, etc...) When you tell the phone to restart, you are actually telling the operating system to restart. The last thing it does before shutting down is say to the BIOS \"Hey ... start me back up in a sec, k?\""
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mjpfmp | Why do people duck when getting on and off a helicopter? | Technology | explainlikeimfive | {
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"To prevent their heads or other parts of their bodies from being caught in the rotors, which are spinning very fast and could cause death or dismemberment. It may not seem like it, but those blades have a bit of vertical flex to them and I'm sure people will take all the clearance they can get.",
"The blades have a surprising amount of flex in them, and can be very springy when not at full speed. Depending on the conditions, the blades can move more with gusts of wind, and in nasty conditions the pilot can adjust the pitch and actually use the blades to keep the helicopter secured on the ground, which in that direction of flex moves closer to the ground.",
"Former airman from a blackhawk squadron here. This is more of a requirement specific to the model of the helicopter. Not all require you to duck. But it is due to the spinning rotor blades. They're very flexible and are more dangerous at the ends than the base. I've seen people hit in the face with them, they're spinning so fast you can't see it. If you're not paying attention you can walk right into them. In one instance just the flesh of the guys face was laying on the ground like a mask. Mustache and all."
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mjqkf7 | how does carbon dating work on old things | Technology | explainlikeimfive | {
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"gtbnsn2"
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"text": [
"Living things have carbon atoms. There are 2 specific types to consider C12 and C14. C12 is very stable so it'll remain the same with time. C14 is not stable so it'll go away with time. By measuring this two we can tell the age of the animals. This works on animals less than 60,000 years old"
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mju2wi | Why do electronic devices take so long to start? Why can't it just turn on the computer instantly? | Technology | explainlikeimfive | {
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"Your computer when it’s off is like an empty kitchen. To actually start cooking you have to get all your dishes out and your ingredients and do any prep work on the ingredients before you can actually start making anything. The computer needs to load lots of stuff from the hard drive into its working memory and get everything in order.",
"Imagine yourself having massive amnesia, and you only know two things: - how to read - that everything you need to do to get ready for work is written, step-by-step, in a book So you read the instructions to get up, to go to the bathroom, how to prepare (initalize) other hardware like the coffee machine or your car, … How fast you can do this depends on your reading speed, on how many machines (peripherials) you need to use, and how many different are described in your book. Edith says I should say \"Thank you\" for the award.",
"They need to go through a boot cycle, which is a series of instructions a computer has to perform basically to make sure everything loads up correctly. Phones can boot up faster than some computers, it depends on how well the device can process instructions and load all the correct data ready to access, for the system to function as intended.",
"Most simple version: In order for your computer to run (I'm assuming Windows 10, but Linux/Mac are the same) it needs to load Windows from your hard drive into RAM. Of course, there's a bit more to it than that. Let's say your computer has a graphics card- well, it also needs to load the driver (a program that tells Windows how to use the graphics card) for that graphics card into RAM. But it needs to know what the correct driver to load is first (you could have changed it since you installed windows), so it has to check and have a chat with your graphics card to see what driver to load. It has to do this with all of your hardware, including a lot of little things (Like your wifi card) that are built into your motherboard. And, of course, loading things into RAM isn't quite as simple as just copying a big chunk from the hard drive. A program needs to know where in RAM all of its data is in order to run, and since it can't know where in RAM its going to wind up ahead of time, loading a program into RAM means giving the program a chunk of memory and letting it load its data into that memory and set up all of the links so that it knows where everything is. Windows is a program just like anything else, so it needs to work that way as well."
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mjvkd4 | Convolutional neural networks | Technology | explainlikeimfive | {
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"text": [
"Neural networks are computer programs that can learn complex patterns from data. You feed a neural network a bunch of pictures of cats and dogs and it “learns” what cats and dogs look like, and can figure out whether a new picture is a cat or a dog. A *convolutional* neural network has a special addition that basically tells the neural network that it doesn’t matter *where in the image* a cat is, it’s still a cat. So if the some of the pictures have a cat on the left side and other pictures have a cat on the right side, the neural network will be able to figure out what makes it a cat either way."
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mjwsai | How do duracell ultra batteries have 100% extra, shouldn't batteries be full allready? | Technology | explainlikeimfive | {
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"text": [
"In addition to what u/disappointingHero stated, not all batteries from the same chemistry are created equal. Sometimes the \"parts\" inside the battery are lower quality (impurities, manufacturing defects, etc), meaning that the batteries produced by one company may have varying energy levels. It is a regular practice to sell the higher quality ones for more than lower quality, even if they come off the same line. This is why you can go to Target and find the same brands selling for multiple times for what you can find them at the dollar store.",
"It's not that they're overcharging them, it's a difference in total capacity due to using different components inside.",
"Hang a bucket of hot water over your head and poke tiny holes in the bottom. That lets you shower under the bucket for 5 minutes. Now take a bucket that's wider but not taller with twice the volume of the first bucket and poke the same sized holes under it. You can now shower for 10 minutes. In this case, the charge or volume of water has doubled but the voltage or water pressure set by the water's height in the bucket has not. This doubles the run time of the shower (device)."
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mjyqx7 | What are SDKs ? | In game development. | Technology | explainlikeimfive | {
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"text": [
"When you make a videogame you don't normally write every single part yourself. Usually you have an engine, where someone else wrote the stuff that handles a lot of the parts. The engine is that, and the API is the way your programs interact with that, but the SDK is the actual software you run on your own computer to write programs to interact with it. It's rarely 100% strictly necessary, but it's generally all set up in a sane way to write programs in a way that works with all the libraries and hardware and stuff without you having to figure it all out yourself. Like it's not the software that runs on the playstation specifically, it's the software that runs on your computer that has all the setup to write programs that will run on the playstation and all the compiler settings and stuff built in"
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mk0tbw | Why are drone batteries so big but have the same amount of mAh ? | My drone battery is huge but has 5000 mAh and my phone is way smaller and has 5500 mAh. Why is that? | Technology | explainlikeimfive | {
"a_id": [
"gtd7cfg"
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"text": [
"Check the voltage. If you wired multiple of your phone batteries in series, the pack would have a higher voltage, but the same capacity in terms of current."
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mk12jf | When downloading multiple files, Why some files are slow in downloading but other files are faster in downloading? | Technology | explainlikeimfive | {
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"There are a handful of reasons, the ones that came to mind for me are : 1. Your software downloaded of choice (whether it be a web browser, Steam or other game launchers, FTP programs, etc) could be prioritizing items based on when you started downloading them. 2. Your connection to the individual server one of your downloads is on is better or worse than the rest, so you have to wait longer for the packets to arrive, slowing down the download speed. 3. Your HDD/SSD can’t keep up with all the downloads at once, so it slows some of them down to make sure everything is downloaded correctly.",
"When you download a file, the server you're downloading it from doesn't know how fast the connection between it and your computer is. All it knows is that if data packages are lost on the way, it's probably sending it too fast and needs to slow down. There are different ways that servers can deal with it, but the common strategy is to start low and increase rapidly until it loses packages, then it cuts it down and increases the rate more slowly, rinse and repeat until it can maintain a speed close to the limit. This is why you can often see a sawtooth pattern on plots of download speeds. The problem with this is that servers sending data can't talk to each other and agree to split the middle. Instead, they tend to steal each other's share of the pie through this constant game of increase and decrease. That is why you often end up with one download being way faster than another. However, this problem can be fixed on your end: Many applications that download or stream files allow you to limit download speeds. So for example if you're downloading a big game on Steam, you can limit the maximum download speed through the settings menu. Some routers also allow you to set more detailed rules for internet traffic, but that's beyond eli5.",
"There's several possible bottlenecks, each of which will determine what file gets downloaded fastest. 1. The download servers. If the servers are fairly slow, your computer might be able to download faster than they (together) can upload. In this case, you'll just download every byte of data as it's sent, and the speed is determined solely by how fast the server can upload. 2. Your internet connection. Most internet connections can only handle a limited amount of traffic. In this case, the ISP decides which download server's data reaches your system first. Most likely, it'll give the physically closer server its bandwidth first, meaning that a nearby site (or one large enough to afford servers in every location, like Google) will get a faster download in this case. If there's spare bandwidth (or your ISP decides to split your connection more equitably), you'll get data from the other servers. 3. Your mass storage device (I.E. hard drive or SSD). An SSD probably is going to be faster than the internet, so it'll save data as it arrives (though it'll group data into blocks large enough to write all at once, to save device wear). But, because hard drives really don't like jumping around, they'll have to prioritize based on what's convenient for the device. That means writing the file that's nearest whatever the drive is already reading/writing first, only switching when it runs out of data in that location. Of course, depending on how your mass storage driver works, it might quietly cache the files in RAM if they download faster than your device can handle, and then write them the moment the disks aren't busy doing something else. This'll let the system completely ignore your hard drive's speed limitations, but might stop working if you fill up your unused RAM with downloaded data that hasn't been written yet."
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mk93gu | Magnets use to mess up all my screens. How can Apple put one in their phone, right next to the screen? | Technology | explainlikeimfive | {
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"text": [
"Because screens now are LED. Tube tvs are different, electrons travel and project the picture, a magnet messes up the course of travel.",
"Old screens used to blast a stream of electrons at little pixels to light them up and steered that stream using electromagnets in the side. If you put a magnet beside it you could permanently magnetize part of the screen which pushed the beam off target Most modern screens use lots of tiny wires that carry tiny electrical signals to tiny crystals that twist when electrified, we use these little crystals to filter the light coming up from the backlight. Little crystals aren't magnetic, they don't care what you do Higher end screens like OLED use little blobs that glow when electricity is applied to them and lots of tiny wires running to all the blobs and they turn the blobs on and off as needed. Again, no magnetic things in the system so nothing cares about magnets in the phone or speaker or in your hand.",
"Phones use completely different screen technology than old TVs. Magnets used to mess up cathode ray tube (CRT) screens because those used a set of magnets to steer a single beam of electrons back and forth across the screen's surface in the process of drawing an image. Modern screens use LCD or OLED technology, where each pixel is individually instructed on what it should display using an electric current, no magnets involved."
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mkan95 | How do whiteboards with real time collaboration work? | I'm wondering how whiteboards on zoom or Microsoft teams allow more than one user to write in real time! | Technology | explainlikeimfive | {
"a_id": [
"gtewu1h",
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"text": [
"Similar to multiplayer games: a dedicated server has the master copy, and all the clients submit their changes to the server as they happen. The changes are then made at the master copy, then all clients get that update. It can only be real time if everyone’s internet speed is fast.",
"As each letter is typed, deleted, the cursor is moved, something is drawn, or posted that update is sent to every single person with the board open and their client adds that content to their view of the board. This stream of data is being sent from everyone to everyone. It's basically the same concept as an online game. Instead of content on a board you are editing your characters location, appearance, abilities active, health, and more. This is all sent to everyone in view distance so they all accurately can see what you're doing."
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mkapfx | Why do the original batteries in a device seem to last so much longer than any you replace them with? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"They don’t. Or at least it is far more likely that one of two things is happening. 1) You are storing your batteries in an environment that greatly reduces the life. 2) What you think is happening as a part of a pattern isn’t really even happening regularly, you just experienced or believed 3 or 4 coincidences and assumed a pattern. There are dozens of little things that could effect performance of the device, requiring more power to perform, but not so much with these really basic devices.",
"I always thought a device came with essentially sample or demo batteries. Where they are lower grade and only have like a 15% charge (or whatever the % is) and then when you switch them with an appropriate type of battery you get a longer usage"
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mkaw5t | Why is Machine learning not applied statistics? | Preface: I'm pretty much self taught software engineer so I probably know about machine learning more than the average person, but haven't really tried to use it in any way. Since I skipped uni (most unis would have statistics in the curriculum), I haven't really touched statistics either and all I know about it is how to make a graph in excel. My take: Definition of statistics: > the practice or science of collecting and analysing numerical data in large > quantities, especially for the purpose of inferring proportions in a whole from > those in a representative sample. And machine learning does exactly that. Collects and analyses some data and infers whatever it was trained to infer. Question: My understanding is, that it actually is applied statistics, but I've read some articles that say it isn't. I didn't really understood why. I understand the data gathering is different, the problems it's trying to solve are different and even the "how it works behind the scenes" is different. But I don't see how it's abstract core differs. so .. why ML isn't applied statistics? | Technology | explainlikeimfive | {
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"I have a masters in cs with a focus in machine learning. Statistics is used heavily in machine learning but it’s a bit like asking “why is engineering not just applied physics.” There is a lot of application and design that goes into building the right agent for the right Machine learning has a lot of subfields, one of which is supervised learning. This is closest to what you describe. Take a training set to train a model to identify the trained inputs in a new set of data. There is also another section called unsupervised learning which could be though of as trying to group the data into categories as well as possible (not based on training data). Even farther away from those examples, there is reinforcement learning. Simply put, you tell the model to work towards something and then it learns to do it over time based on feedback from the environment. This learning is more “on line” and similar to how people learn. This is kind of like learning on the job because the agent is often having to explore what makes a good decision and what makes a bad one."
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mkbie1 | What exactly do each component of a computer do? Ex: cores/threads in a processor, a graphics card, RAM, the disc, etc. | Technology | explainlikeimfive | {
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"text": [
"The CPU does math. The threads are amount of arms that can hold a pencil to do math with. The RAM is how many books can be open at a time, how many eyes there are to read them math problems. The disk is like the notepad of answers to the math problems. The GPU is the one kid in class who is amazing at advanced math but struggles to open his milk carton at lunch time.",
"Alright, you're building yourself an office: Motherboard: this is the building they work in. You need enough cubes to house everybody, some people need whiteboards, some people need desk space, some people need Bluetooth connections, it all needs power, water, sewage, the motherboard is the building that houses and supports it all CPU: This is your central workforce, these guys can do just about everything. They're resourceful, they're clever, you give them instructions and they'll do it. Cores are basically how big this department is. If it's only one guy working there, it's a single core. If there's more than one, it's multi core. Usually more cores is better, because then your department can multitask, but the quality of the cores can also matter. 4 Interns doesn't necessarily = one college grad. Graphics Card: When a task is just so friggin' CONSTANT, you really just need a department dedicated to it. Otherwise you're just making a CPU core dedicated to it, which... would work. But why not just specialize an entire department into it if they're never going to bother doing anything else? While we're at it, why not build their cubes for nothing but the task at hand. The GPU department is dedicated to lighting 921,600 to 8,294,400 lights in one of 16,581,375 colors. It's a lot of stupid math... but it's stupid FAST math, calculated \\~60 times a second. Their cubicles are designed for SPEED BABY SPEED with a coffee drip IV into their arms in a fashion more akin to the old stock exchange markets and small clipboards that don't give much room for anything but simple math... CPU cores no longer want to work in that department anymore, it takes a certain type of crazy. RAM Every office is cranking out new widgets to sell and we're no different, RAM is how much the office can chew and basically how many new/existing projects can your office announce and juggle. Low ram and you're like Nintendo, one console at a time. High ram and you're like the American Military complex, you're doing so much crap you can't even keep track of it. It's the amount of inventory you have in the office for R & D, your printers, it's where your workers keep the stuff they're actually working on, the showroom floor. This is where the widgets get shown, assembled, and sold Hard Drive: It's a lot like above... but 8 blocks down the road and built like a warehouse. Yes you have access to it... but it sucks. You gotta write down the location your stuff is stored in, drive down in your car, find the location in the warehouse, load the car with the stuff you want, drive back, unload, and now you can work with your CPU cores (or GPU) on the project you had stored in the warehouse... nobody WANTS to work like that but the sheer amount of space that warehouse has is amazing. It's a terrible environment to work in but sometimes projects get put on hold, and there's no way you're going to just leave it in the office for no reason. It serves its purpose well. Disk drive: same as above, but the warehouse can be swapped with other warehouses and is stored 20 blocks away"
],
"score": [
37,
13
],
"text_urls": [
[],
[]
]
} | [
"url"
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| [
"url"
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|
|
mkbmqj | Why are so many news websites formatted so badly? | It seems like it's intentional. | Technology | explainlikeimfive | {
"a_id": [
"gtf0mhn"
],
"text": [
"They're designed around two things- making you click on ads, and making you click on more articles. The confusing layout is, indeed, somewhat intentional. They don't want you to just read the article and close the webpage- they want you to get distracted by another headline, load another page, and possibly click on an ad or two by accident."
],
"score": [
17
],
"text_urls": [
[]
]
} | [
"url"
]
| [
"url"
]
|
mkf1f3 | What is a hackerspace? | I assume it is some place where hackers get together, but how does it wok? | Technology | explainlikeimfive | {
"a_id": [
"gtfiykc",
"gtfkmxa"
],
"text": [
"It's usually a community run workspace. not really meant for hacking in the sense that most people would think, but more for people that need a place to work together, like if you and a few friends were making a computer game but didn't have the technology to work on it at home. They usually have tools for physical projects, too. Like soldering equipment, 3D printers, workshop type tools, etc. There's probably going to be a membership fee, unless it's run by your school.",
"It's a communal workshop where people get together to break apart things, code and skills only to build new things, code and skills. Sometimes pizza and beer is involved."
],
"score": [
9,
4
],
"text_urls": [
[],
[]
]
} | [
"url"
]
| [
"url"
]
|
mki1ez | What is ping and packet loss? | Technology | explainlikeimfive | {
"a_id": [
"gtfwhzg",
"gtfwlu5"
],
"text": [
"As I understand it ping is like yelling to your friend and then your friend responds. The time between those shows the delay. Packet loss would be you handing candy to your friend, each one a packet, and how many get dropped(lost) between the transfer is packet loss.",
"Ping is how long it takes one computer to send data to another one and get a response. Sort of like an echo. Or playing catch - How fast you can throw a ball to someone else and get it thrown back. Lower ping is better, it means you can send and receive quickly. Packet loss = how much data is actually lost in sending/receiving due to screwy connections. If there's a lot of packet loss your download and upload speed to that other computer are going to be bad because you gotta send/receive the data multiple times for it to transfer 100%. Usually more noticeable in streaming things like online games and movies."
],
"score": [
7,
7
],
"text_urls": [
[],
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} | [
"url"
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| [
"url"
]
|
|
mki75d | What is the difference between PGP keys, SSH keys, and SSL keys? | I know that they all use asymmetric encryption, but I don't understand their differences and applications. Any guidance is much appreciated! | Technology | explainlikeimfive | {
"a_id": [
"gtg0cdb",
"gtg53kr",
"gtfxr2u",
"gtgmq2r"
],
"text": [
"The only difference is the types of programs they're used for (PGP usually for email or encrypted messages, SSH usually for securing remote connection to computers, SSL usually for running a website or anything else done over SSL), but besides that they're the same keys just wrapped in a different container.",
"These are not different kinds of encryption, they are different *protocols* that give other people the information they need to understand how they can decrypt or verify your message. They may allow for an array of different options for exact cryptographic algorithm, which is important so that we can upgrade to more secure ones over time, or fix bugs. The connection protocols, TLS and SSH also have some kind of negotiation built in, so that the machines can understand each other and perform key exchange. PGP (1991): Pretty Good Privacy, designed for digital signatures and encryption for individual messages, such as emails. You *might* be using this somewhere without knowing about it, e.g. it might be used to sign your emails. SSL (1994)/TLS (1999): Secure Socket Layer/Transport Layer Security, protocol for encrypted *connections*, also allowing for proof of identity with digital certificates. Best for public facing web servers, to the point that all of your web traffic goes over TLS now, browsers will warn you if it is not. SSH (1995): Secure SHell, secure machine to machine command line protocol, which includes logging into a user account. Similar, in principal, to SSL, but higher level and more advanced and allows all machines to interface with each other at the command line level. You probably won't use SSH unless you are a developer, the most common use is SFTP (which is basically just running the FTP protocol inside an SSH connection.) I'll let you guess what the S stands for.",
"PGP is mostly used for text messages between people, like email. You typically send the decoding key out to people, and a lot of people might have it. or you might make it public so everyone has it, and it doesn't really encrypt anything, but proves you are really you, since you are able to 'sign' things. SSH is generally to talk one machine to one other machine. If you want your laptop to connect to one linux server you make one SSH for key. Multiple computers can use the same key and it works, but the idea is one to one. you download it and one computer can talk to another computer. SSL is good for automatic connections. Anyone can go up to an encrypted website and get a key to talk to it, so no one else can read what you are doing with it, but it'll give one to anyone.",
"There's another difference not mentioned yet: in SSH, the keys are used on their own, but in SSL (really TLS these days) there's also a certificate, which is the public key with some information about the subject, bound together by being signed with the private key."
],
"score": [
47,
28,
12,
4
],
"text_urls": [
[],
[],
[],
[]
]
} | [
"url"
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| [
"url"
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|
mkktce | Why do computers start up so fast now? | I remember computers used to take sooo long to start up, that you can press the power button and go make yourself a sandwich. What changed? Hardware got faster obviously, but software also got more complicated and there are more of them to load up no? | Technology | explainlikeimfive | {
"a_id": [
"gtga7os",
"gtgb4i2",
"gtgae7n"
],
"text": [
"Solid state drives, mostly. The OS is now often put on a solid state drive, rather than a big 'ol set of spinning platters, from where it can be read into memory very quickly.",
"SSDs are the biggest contributor as mentioned, but it's also due to general OS changes in some cases. In Windows for example, they have \"Fast Startup\" - which realistically is just waking from a sort of hybrid sleep mode. The computer writes a hibernation file then shuts down, when it boots it does so using that file which is faster than a cold boot. This is the default in almost all laptops, and in some desktops as well. Any time you boot the computer from \"shutdown\", it uses this file which is much faster than normal. A reboot operation is more akin to the shutdown from the old days of Windows, with the caveat that the computer starts back up afterwards. This Fast Startup can be disabled too though.",
"Faster processors, but also it's become standard practice to ship computers with a Solid State Drive for at *least* the operating system. These are a *ton* faster than traditional Hard Disk Drives because they don't have any moving parts - the computer just goes in and grabs what it needs. They've been around for many, many years, just for whatever reason weren't necessarily the *standard* until the past decade or so."
],
"score": [
19,
8,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
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| [
"url"
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|
mkn0bj | Does the number of threads increase the CPU execution time? | I was doing an exercise in C of matrix multiplication using threads and I realized that as I increased the number of threads the same happened with the CPU time. My computer has 2 cores, each of which can run two threads (Intel Hyper-Threading), but why exactly does this happen? | Technology | explainlikeimfive | {
"a_id": [
"gtgo7cq"
],
"text": [
"Dividing up a task so it can use multiple threads is not free. So you need to do som extra stuff to split it apart and collect the result. If the matrix you multiply is small the overhead can be greater then the time you gain by doing the calculation in parallel. So splitting it up can increase the time Try it with large matrices and you will likely se a decrease in time. Hyperthreading is sharing the same core for two threads. You can get a bit of extra preformence if there is a lot of waiting for data from memory. So going from 2 to 4 threads likely only increase preformence if the matrix size is larger then the CPU cache size."
],
"score": [
8
],
"text_urls": [
[]
]
} | [
"url"
]
| [
"url"
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|
mkok3j | How does a SIM card store data such as voicemails, contacts, etc.? How much data can a SIM card hold? If, then, it connects to the internet, how so? | Technology | explainlikeimfive | {
"a_id": [
"gtgvzbf",
"gtgwasl"
],
"text": [
"A SIM card isn't all that special - it is just a specialized form of [smart card]( URL_0 ) designed to hold specific kinds of data rather than be general purpose storage. SIM cards can come in various data capacities, from 8 KB to at least 256 KB. All can store a maximum of 250 contacts on the SIM, but while the 32 KB has room for 33 mobile network codes (MNCs) or network identifiers, the 64 KB version has room for 80 MNCs. It doesn't store voicemails - those are stored on the phone itself or on your carrier's servers. The card itself doesn't connect to to the internet - your phone does that - but rather the SIM provides the credentials to allow you to use a particular carriers network.",
"SIM cards don't hold voice mail. They have a small amount of memory for holding contacts and little else. Voice mail is held at your provider. The amount of memory is small, something like 64K, depending on how new it is. Most data is held either at some server, or on your phone's local storage. It doesn't connect to internet, rather it's your \"password\" to connect to the internet. It tells the mobile network who you are, and gives it a way to bill you for your usage."
],
"score": [
24,
6
],
"text_urls": [
[
"https://en.wikipedia.org/wiki/Smart_card"
],
[]
]
} | [
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]
| [
"url"
]
|
|
mkoxzg | How do missiles locate their target? How do they identify that they got the correct target? | Technology | explainlikeimfive | {
"a_id": [
"gtgz45g",
"gtgyoqb",
"gth07q9"
],
"text": [
"Generally the target is found first by a much fancier system and then the missile goes where its told Missiles can be sent to a specific location via GPS guidance, or they'll use inertial navigation to know how far and what direction they need to go from their launch points Others will track a specific thing like a radar return, or laser beam, or heat source, but generally some person first found the target and then selected it as \"this is where you should go little zoomer\" and the missile uses its onboard sensors to pick up the same target, confirms that it got the right one with the launcher, then goes for it Very very rarely do missiles get sent in and try to pick up the target on the way. Missiles don't have much computing power in them so they are far easier to trick into going to a wrong target than the full electronics suite of a reusable plane or drone.",
"Varies a bit from technology to technology. Heat-seeking and optical missiles see a high-contrast picture and try to maneuver so the object they are tasked to follow stays where they plan to hit it (they can think ahead to intercept objects). Radar missiles emit high-frequency radar pulses that are echoed by the object the are tasked to track. This way they know where their target is and then they can act the same way as heat-seekers or optical missiles. All of these technologies can be fooled, though. If a plane crosses exactly in front of the plane they are tracking (and its path isn't too dissimilar from their target's) they can sometimes switch to the other plane.",
"It depends. Heat/IR-seeking - there's a device that tracks a thermal source - can be confused by a stronger thermal source like a flare. Very early versions could be confused by the sun. Wild Weasel - Targets strong EM sources like radar and microwave transmissions - typically used to take out radar and communication systems GPS/Satnav - there is no guidance other than the ability to take input of the target coordinate, and a nav system to fly by the gps system. Fairly accurate up to a few feet. Requires a GPS or like receiver. Programmed Course - If you know where you are, and know where the target is, and know the variables of the missile such as fuel, weight, and external variables such as weather and orbital rotation you can program in a course that puts the missile in motion to reach its target. Very much like rockets and artillery. Networked with a target device like a range-finder - More convoluted. Requires at least communication between the targeting device and missile, the ability to know its location(gps) in regards to where its launched from and where the targeting device is. Visual/camera - Found in a lot of fly by wire. If there's an onboard computer/AI it can identify a target but this relies on pre-programmed libraries or advanced identification techniques which can be fooled and are only as good as they're programmed. & #x200B; As for identifying if it struck correctly or not, that's up to the people who fired the missile. Missiles are rarely anything other than a single use item. In a dogfight, the pilot would have to make the call whether or not a second missile is needed and this happens in a split second. Other missile use is typically followed up minutes or hours later for observation depending on the importance or ability to find out. Methods of follow up could be aerial recon by a second plane, sat observation, soldiers or inspectors on the ground, and drone flyovers."
],
"score": [
12,
3,
3
],
"text_urls": [
[],
[],
[]
]
} | [
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| [
"url"
]
|
|
mkq5s6 | Website URLs and Domains | Hello, Can someone please explain how website URLs and domain names interact? Specifically, if you own a domain such as: URL_0 If you have the domain records setup so that the CNAME www. URL_0 - > URL_0 How does the www version become the default web address and how is 301 redirects applied? If www is pointed to naked domain, why does the website default to www version - shouldn’t it be the other way around? Or is this web server configuration based? | Technology | explainlikeimfive | {
"a_id": [
"gth6qyb"
],
"text": [
"The DNS records tell a browser where the server is. So if you ask your browser to go to https://www. URL_0 /, the browser looks up www. URL_0 . If it finds a CNAME record pointing to URL_0 , it will know it should look at the record for URL_0 instead. And when it does that, it will find the IP address of the web server. To that IP address, it will send a GET request, saying \"get me the file at `/`\", that is, the top-level page or homepage. The server will look for that file and respond with it. If it's an HTML file like most websites are, it will contain text and can contains link to other files that it tells the browser it should look up as well, like stylesheets and images. Note that in this example, it's not necessary to use the `www` hostname. You'll get exactly the same result if you skip that step and go straight to ` URL_0 `, since the CNAME record is just pointing to this record. What if you want to make it so that people *have* to use `www`? You have to set that up at the server level. People will still be able to find the server by going to ` URL_0 /`, but you've set it up so that instead of responding with the page they're looking for, the server tells them go find it at `www. URL_0 /` instead. Even though it's the same server, it's giving different answers whether you're looking up the \"correct\" address at `www. URL_0 /` or the \"incorrect\" one at ` URL_0 /`. It can do this is because those URLs are different and so they can have totally different contents and actually, there's no reason those addresses need to point to the same server at all."
],
"score": [
7
],
"text_urls": [
[
"example.com",
"https://www.example.com/",
"www.example.com",
"www.example.com/",
"example.com/"
]
]
} | [
"url"
]
| [
"url"
]
|
mkq7ex | Why does hyperthreading increase CPU performance? | Technology | explainlikeimfive | {
"a_id": [
"gth78z4",
"gth6reo"
],
"text": [
"A CPU core has many parts. One accesses memory, one performs simple arithmetic (addition, subtraction, etc), multiplication is usually a separate piece, floating point is separate, encryption is separate, etc. Hyperthreading takes advantage by trying to run two jobs at the same time but having them share the parts of the CPU. If one wants to execute a multiplication instruction and the other wants to decrypt data, both can run at the same time. It's only when they want to use the same part that they have to take turns. So hyperthreading isn't a doubling of speed due to these situations where they bump into each other, but it can really help. It's like having two cooks in a kitchen. Though there's still only one sink, one oven, and one cutting board, you can still get dinner prepared faster by having another person working. Not double speed, but a lot better.",
"The CPU isn't a single unit, each core is actually multiple blocks If I give you an array of 10 numbers and tell you for each item in that array first add 4, then multiply by 3. If we're restricted to a single operation at a time then you have a lot of wasted time because the adder is empty when you're multiplying and the multiplier is empty when you're adding Superscalar architecture works to split instructions so that it can keep the blocks busier so while its multiplying for the first item its adding for the second so that nothing is empty But in real programs you often won't be filling all the blocks all the time. Hyperthreading lets two different programs run on the core at the same time with their own memory so they don't get jumbled, this does an even better job of ensuring that all of the blocks are doing something as much as possible. Consider cooking a large meal with a meat and a sauce and a pasta. Do you cook the meat in a pan, finish it, then the sauce in another, then the pasta or can you cook all three on the stove at the same time? You have spare pans and burners, but you need the capacity to focus on multiple things in succession, that's what hyperthreading gives the CPU"
],
"score": [
45,
3
],
"text_urls": [
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[]
]
} | [
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| [
"url"
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|
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