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b16tic | How do companies (such as 1Password) verify a password is correct without storing it anywhere? | Technology | explainlikeimfive | {
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"Based off of its description, 1Password DOES store your passwords. It most likely encrypts them, and doesn't store them in the clear. But it does store them.",
"The idea of password storage relies on using an irreversible function that [ideally] returns a unique output for any given input. Since the function can not be reversed and hopefully only one input could generate the same output, the website can store the output and use that for authentication. It's like if I asked you to give me a numerical password, I added up all the digits, and stored the sum. Next time I see you, you give me the original input, I calculate the sum and compare it against what I had written down last time. If the sum matches, I know it's really you speaking to me. However, if you stole my notebook, you would know that [Person]'s secret sums out to X, but you wouldn't know what original number was used to generate that sum [Obviously such function that I'm using as an example is extremely prone to collisions since there are multiple possible strings that could generate any given sum, but let's just ignore that for simplicity's sake]",
"Your password goes into a grinder and comes out as a hamburger. They store the hamburger instead of your password. Now when you type your password, they grind it up and see if it’s a hamburger. If so, you typed the right password."
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b17jpz | Pi has just been calculated to over 31 trillion digits (smashing the old record) and it took 111 days. Why was that the stopping point? | Technology | explainlikeimfive | {
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"All those computers cost money. AWS sells time on those computers. When paying customers want to use them, the pi folks have to wait. They wanted to announce before March 124 (pi day) and that's how far they got."
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b17ywa | What is the difference between Object-Oriented Programming and Functional Programming? | Freshman in Computer Science here. This a concept that for one reason or another I can’t seem to wrap my head around | Technology | explainlikeimfive | {
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"Object-Oriented Programming is something of a buzzword that has a variety of definitions. At the most fundamental, it's about bundling data and algorithms together so they're isolated from the rest of the program. Functional programming is the counterpart to imperative programming (and both can be object-oriented or not). Consider the following 'program': 1. Get out of bed 2. Take out the trash 3. Feed the dog In an imperative program, you are required to do those steps in that order because that's the order I programmed them in. In a functional program, you would program it differently. Instead of a 1,2,3 sequence, you would explicitly label the dependencies. Clearly, you need to get out of bed to do either of the other two activities. But the other two activities are not dependent on one another in any way. So I could write it as: GetOutOfBedComplete = GetOutOfBed() TakeOutTrash (GetOutOfBedComplete) FeedTheDog (GetOutOfBedComplete) This makes it clear to my compiler that the order of TakeOutTrash and FeedTheDog isn't relevant (while the order of GetOutOfBed and the other two is relevant). Indeed, if there were two of me, I could do TakeOutTrash and FeedTheDog simultaneously. In theory, the advantage of functional programming is that ability to re-arrange tasks in time and parallelize them. Note: Compilers can often optimize imperative code in a functional manner by identifying the dependencies at each line. However, functional code can be used to perform this optimization at run-time."
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b19ffx | How does WiFi or cellular data work? Are audio / video / text transmitted differently? | Technology | explainlikeimfive | {
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"In modern world all data is transmitted as binary string of 1s and 0s. How you interpret it makes all the difference. Audio , video and text in digital networks are transmitted similarly as 1s and 0s . In very simple terms: there are a lot of established international standard protocols that state how this binary data must be interpreted . Usually the data is sent as packets which are sort of like Russian babushka dolls. On the top is the carrier or envelope, which contain information on who sent it, how large it is and the actual data. This data is then sent for further processing which extracts things like say what application is this message for? Then finally the application gets that message and interprets it into audio or video depending on what the message said. The above process assumes that all the data was sent according to a protocol or format otherwise there will be communication error. But the entire data can be converted into a string of 1s and 0s ."
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b1bdky | Why do fitness trackers and smart watches need the green lights/lasers to operate, and why are they always green? | Technology | explainlikeimfive | {
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"They seem to be using a technology called Photoplethysmography (PPG) where green (and sometimes infrared) light is flashed onto the skin and sensors measure the return amount. & #x200B; Blood is red (duh) and it absorbs green light. During a heartbeat, there is more blood flow, than in between heartbeats. & #x200B; More green light returned (no heartbeat) Less green light returned (heart just beat) Do that over a few seconds and you get a pulsrate. And the light used is green, because it seems to give the best (most accurate) results compared to red or blue & #x200B;"
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b1copp | How do planes know when there's an air turbulence in front to turn on the seatbelt signs? | When there's a turbulence coming, the lights always go on a few seconds in advance. Can the pilot see the turbulence coming or is there a radar or something like that? | Technology | explainlikeimfive | {
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"There are multiple ways that pilots can know turbulence is coming. Some kinds of turbulence can be seen on the radar on the plane. Sometimes pilots can see conditions that are likely to cause turbulence (like layers in the clouds). Additionally, pilots will report turbulent conditions on the radio, so at times air traffic control may provide pilots notice of upcoming turbulence.",
"Planes that have flown the same route earlier report turbulence and it gets passed along. I have been in planes where they tell us to prepare for turbulence and there is nothing as it has dissipated/passed since the last plane flew through.",
"> When there's a turbulence coming, the lights always go on a few seconds in advance. Always? Certainly not in my experience. The lights usually come on after the turbulence has already started. Occasionally the pilot will make an announcement that other pilots have reported turbulence in this area so he will be turning on the light preemptively. But that is the exception, rather than the rule."
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b1e7o0 | How does night vision cameras work? | Technology | explainlikeimfive | {
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"When it's dark there is not enough photons to trigger the sensors in our eyes. But there are still enough to trigger the sensors in an CCD camera. The processor inside the CCD camera increases the level of the received data so that there is a higher perceived brightness and as such you can see the details. More ELI5: Better eyes which can deal with less photons.",
"Shoots out IR light which is not visible to human eyes. But camera sensors can pick them. Then the feed is converted into visible spectrum. They also have a setup that have super sensitive light sensors. So that it picks up every minute source of light. I am no expert. Just basing this based on own knowledge of physics."
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b1eejg | Why can't we freely zoom-in in videos/gifs while we can in still-photos? | Technology | explainlikeimfive | {
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"You can...? I don’t recall the last time I used a desktop media player that didn’t support this and mobile players are starting to (iOS does out of the box)."
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b1gkfd | Why do mobile apps get updates so frequently? | Some of the apps literally have updates in 2-3 days. What is it that they are adding to the app so frequently? Is it not possible to have delayed updates that are larger in size? | Technology | explainlikeimfive | {
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"A few reasons. 1) It's very easy to update an app, even for small changes. A day's work could solve a lot of problems, and just a few button clicks sends it out to everyone 2) Apps potentially have much smaller dev teams than a lot of other software. This cuts down on the bloat and allows them to push through updates a lot faster 3) Phones are *fragmented*. Especially on android. It's unrealistic to try and test for every phone out there, but they all work very differently and a lot of different issues come up. These can be minor, or totally app-breaking issues that you were completely unaware of. This totals up to a situation where big flaws can come up for a section of users, that can be fixed quickly, and can be pushed out easily. So if you've managed to fix a problem for some users, there's really no reason to hang on to it just for a big update later. Most of these fixes are fixing problems that you might never encounter, and might not even be *able* to encounter if they're device-specific issues. Of course, quick and easy fixes *might* lead to more problems for other users... but that's a whole other thing. A lot of times it really is pretty simple, if you've got a simple app, to just quickly identify an issue and be pretty well-assured that fixing it won't cause other issues."
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b1h81u | Why are 4k TVs with a ton of features cheaper per-inch than a computer monitor of equivalent specs? | Why do computer monitors cost so much when a 50inch 4k tv with HDR can cost as little as 600EUR these days? The same argument can be made for smartphone screens, AMOLED screens of 4k resolution with perfect blacks, smaller, pricier to manufacture, attached to a fully functional pocket computer, cost less than a larger TV of the same specs / technology. | Technology | explainlikeimfive | {
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"There are some specs that aren’t mentioned in tvs. One important spec is latency. I would venture to say that a tv will be much slower on the order of 15- or more milliseconds. A good gaming monitor has 1 millisecond response time."
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b1j0u7 | How does programming a video game work? Can the devs test it at any given moment? | I understand that there are software like Unity that helps out, but what about older games like Super Mario? | Technology | explainlikeimfive | {
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"Generally, a program must be \"compiled\" to run. Compiling the the process of taking human-readable programming and turning it into computer-readable machine code. When programming, the programmer will do a bunch of changes, compile the program, and test the compiled version. They will then find bugs, go back and fix the bugs, and recompile the software. This process continues until the program is ready."
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b1l8cs | If computers run on code, then how did the original computers know how to process code? How was the first computer programmed? | Technology | explainlikeimfive | {
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"There is something called \"machine code\", which is the code actually executed by processors. The processors are physically built to understand such code, they \"know\" how to execute it because of the way their transistors are connected."
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b1le73 | How does the 4k recording on an S5 differ from the 4k recording on the S10 if it's the same resolution? | Technology | explainlikeimfive | {
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"The video sensor picks up less noise on the S10, the preprocessor does a better job of interpolating the signal, and the compression preserves the data that better represents what was originally seen. Think of the video like a glass of water. Both videos hold 4K (or 4oz of water) but the quality of that water can be vastly different depending on how it was processed before being put in the glass."
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b1lfuj | How does Dolby Surround and Pro Logic work if it's just stereo audio? | Technology | explainlikeimfive | {
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"Prologic works by flipping the phase on the audio meant for the rear channel. The decoder works like this: * any audio this is present on both the left and right channel and is in phase, is routed to the center speaker. * any audio that is present on both the left and right channel but is out of phase is routed to the rear speaker. * any audio that is only on the left stays on the left. * any audio that is only on the right stays on the right. EDIT: If you don't know what phase means. Audio is air moving back and forth. Speakers make audio by moving back and forth. Audio is encoded as voltage that swings from positive to negative. So when we say that audio is on both the left and right channels but 'out of phase' that means one speaker is pushing the air while the other speaker is pulling the air. In practice you can have the left and right be out of phase and you won't really notice. But the ProLogic decoder can tell and thus can route the out of phase audio to the rear speaker."
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b1moka | What's the difference in frigates, cruiser, corvette, Battleships, destroyers, and dreadnoughts? | Technology | explainlikeimfive | {
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"A battleship is a large, heavily armored warship with big guns. A dreadnought is just a name for a type of battleship that was popular from 1906 until the interwar years based off the British battleship HMS Dreadnought. Battleships have been obsolete since the end of WWII. There are none in service now. The difference between the others is less clear cut. There's no single definition, and each navy calls its ships different things. Generally, corvettes are small-ish ships that don't operate on the open ocean but are mostly used for things like coastal patrol and defense. Frigates are a step up from that, being somewhat larger and better armed. They might operate on the open ocean alone. There's overlap between what you could call a frigate and a destroyer. For example, the French and Italian navies' largest surface combatants are called frigates, despite being comparable to what other navies call destroyers. There's also significant overlap between what you could consider a cruiser and a destroyer. Only 2 navies in the world operate cruisers. Traditionally, cruisers generally were larger and focused on anti-air, and destroyers were smaller and focused on anti-submarine warfare. Nowadays, the distinction is mostly moot, with modern destroyers and cruisers being similar in size, armament, and capability. Destroyers and Cruisers are generally the largest surface combatants of a navy with the ability to operate alone on the open ocean or as part of a carrier fleet, and have the ability to engage just about any kind of target with a wide variety of guns and missiles."
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b1o40b | Why is it so difficult to program reflections in games? | I often see alot of discussion revolving around that subject and never quite see any reflections in games. | Technology | explainlikeimfive | {
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"There is so much to take into account because light bounces off of everything which is fine if the scene is static. Once you start moving around, you have to calculate every reflection, color changes, refraction, shadows, etc every single frame for every object in the frame. And this is only one small part of the game environment.",
"Conceptually it isn't difficult provided you have plenty of time to do it. Suppose you have your first pixel of your image and you want to figure out what color it should be. You could use a technique called \"ray tracing\" where you calculate a straight line from that pixel going out in a direction determined by the field of view and focus of the simulated camera. Figure out the point where that intersects an opaque object in the scene, and then from that point draw a straight line to any light source in the scene checking for obstructions along the way. Calculate the appropriate lighting on said point from those light sources, determine the texture overlaid on the object along with the associated angle, and then you produce said pixel's color. Repeat for all your pixels and you have an image. Rendering a reflective object with this method is relatively simple as your first line (or \"ray\") when intersecting with a reflective object can just bounce at an angle determined by the geometry of the object and continue on until it intersects another relevant object. The problem is this technique is *slow* and each image needs to be produced in fractions of a second. People playing a game don't have hours to wait on a perfectly rendered frame, they need at least 30 per second (and many prefer 120 or more). Instead games use some techniques to form an image in a faster way. You figure out the field of view of your camera and then only objects which might possibly intersect with that field of view are rendered, everything else in the scene is culled and ignored. This can often be done in a simplified way just by considering a single origin point of an object model as opposed to trying to calculate the actual shape of the model itself. Then each model can be rendered independently and things like occlusion calculated afterwards (figuring out exactly what part of the wall behind a character isn't able to be seen from the camera can be computationally difficult, it is easier just to render the wall in full and then put the character in front of it, figuring out what parts aren't shown during this process). In these sorts of methods true reflection is a really tough problem. If objects can be reflective then how does the scene get culled at the start? We haven't gotten to the step where the surface textures of objects are even determined, or calculated their physical geometry, so how could we know what a reflective surface would be expected to show? A reflective object with a complex geometry would require rendering the entire scene from multiple angles and then somehow wrapping the results around said object for us then to render *that* texture for the object which only works for that single frame... and what if that reflective object reflects *another* object with reflection?! Our task of rendering a frame has now somehow started to nest more tasks within itself, there is no way it is going to be finished in the fractions of a second available."
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b1ogjr | Why do relatively popular free movie sites not get shut down sooner by authorities? | I'm all for it, im just curious how these sites stay up for so long. | Technology | explainlikeimfive | {
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"It may be that the computer servers operate in countries where there are no laws against it. I could be mistaken, but online gambling sites are similar in that regard",
"It's a combination of the sites' being hosted in countries that ignore copyright complaints, and some sites being listed as a simple hosting site and that they're not responsible for whatever their users use their site for.",
"Pssst. What are these sites of which you speak? Lay it on me. Feel free to PM me.",
"A few years ago, I built and designed a pirate ship playhouse for my daughter. Are these the actions of an undercover agent? URL_0"
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b1oujq | When an accident happens in public and multiple people call the police, how do operators know if a call has already been made about it? | So is there one or multiple operators? Do they just tell each other? Just came to my mind when I passed a car accident. | Technology | explainlikeimfive | {
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"There’s a central computer system that the incidents are logged into. I would expect the location of the incident and the other details would allow the operators to realize things have been reported already.",
"There is a program that every work station uses that when a call comes in we document as much info as we can and send it to the radios. And if another person gets a call that matches the location to approximately 1 mile then it pops a duplicate call window. If the information matches then we put the calls together. That's why it's important to know the location."
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b1tc56 | What are the sounds a PC makes when it's launched? | Technology | explainlikeimfive | {
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"text": [
"Are you asking about the POST (Power On Self Test) beeps? POST beeps indicate if all the hardware in the PC is healthy enough to run. When a PC is first turned on the boot process checks the CPU, RAM, video card, etc. to make sure they are ready. If anyone of them fail you will get multiple POST beeps. If all is good you hear 1 POST beep. Edit: spelling",
"In addition to the other comments, all your fans will likely come on briefly until the temp control system is up, for safety. Mechanical storage like CD, floppy (!) and spinning HDDs will spin up, recalibrate any positioning and do a media check before settling down again in case the machine needs to boot from them.",
"When the computer is turned on it will first do a Power On Self Test to check that all components are working and initialize the components. If something is wrong it will alert the user of its progress so they can know what component was being tested when the computer had issues. But one of the latest components to be initialized is the video card and it might even be the source of the problem. So the computer can only communicate with the user through the speaker and lights on the motherboard. A lot of failure modes will turn off the power and therefore the lights so these can not be used in all cases. So it needs to beep to let the user know how far in the POST it have gotten. What the beeps and lights means depends on the motherboard and the BIOS and can be looked up in the troubleshooting section of the manual."
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b1vum9 | Why haven't we invented ray guns yet? | Technology | explainlikeimfive | {
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"I mean lasers exist but even if ray guns existed, they likely wouldn’t look like what you see in movies with a visible beam flying through the air"
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b1weqk | How accurate are older temperature recordings(i.e. ice cores, older measurements, other temp proxies)? | It's oft cited that worldwide temperatures have been rising but how well can we rely on data collected with less accurate tools or with proxies? PS: I'm not a climate denier just trying to explain to my denier friend and learn a little while Im at it | Technology | explainlikeimfive | {
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"We've had accurate instruments for only a couple of hundred years. But we have estate accounts and diaries going back many hundreds of years. These are not as accurate, but since they overlap the period of modern instruments we can compare the two and have a very good approximation of the weather that far back. To go back further we can look at accounts of harvests and records of the Nile floods which go back thousands of years. While the harvest depends on rain as well as temperature, we can see which years had a good harvest, and of which crop. This gives an indication of the climate. To turn to proxy measurements, such as ice cores, tree ring data and sea bed cores. Ice cores tell us the amount of CO2 or SO2 in the air. Since these are the two most influential gases on temperature, they enable us to make a good approximation. Tree ring data tells us if it was a good or bad year for trees to grow. On their own they don't tell us the temperature because both temperature and rainfall affect their growth. But again like crop harvests they show when conditions were favourable to growth. Sea core data is a good indicator of temperature. Many diatoms are very sensitive to temperature. The abundance of one species over another gives the temperature to within a degree or two. No good scientist is going to rely on just one proxy. But since all the proxies agree, it's fair to say we have an accurate picture of the climate going back millions of years. We can go back further by looking at fossils. It's not as accurate, but the shape of plant leaves can give an indication of rainfall and temperature."
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b1xte5 | How were movies and TV shows edited and then copied for mass production before computers were capable of doing this for us? | Technology | explainlikeimfive | {
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"Movies used to be a long line of images, like photo negatives but on a much longer roll and comprising 24 or 26 frames per second. The movie was edited by physically cutting the roll after a frame and taping a new section of film (a new angle or scene) after the cut. Movie editors used to be very highly skilled due to the inability to make too many mistakes (digital editing doesn't have the same stakes as the original copy isn't damaged, no matter how many changes you make). The finished roll was then copied like photograph negatives can be, so a whole new roll of individual images was made and sent out to cinemas. It was a time and labour intensive process. Movies were not available for personal use until digital technology became available (I mean you could have a cinema and projector in your house but it was incredibly impractical). TV shows were edited and shipped out using the same format (huge film reels of individual frames) but I'm unsure how that was then turned into a broadcast signal before the digital age.",
"Movies used film until quite recently. Many of the 2018 blockbusters were still shot on film and not digital cameras. To edit film you used a special editing table that allowed you to view the rolls of films as you cut the film with a cutting blade and taped them together with scotch tape. To duplicate a film (which you often had to do after editing as the film were more tape then film) you would run a film over an undeveloped film and then shine a light through it to expose the undeveloped film. You could then develop this film and distribute it to the movies. The same rolls of films (and posters) used to be sent from movie theater to movie theater often going through three different movie theaters before being shipped overseas to international theaters as the films were expensive. & #x200B; TV needed fresher content and did not require the high resolution of the movies as TV was low resolution anyway. They could use film as well of course. However they did a lot of things live and then later on using magnetic tape. The tape can be played on one machine and then recorded on another. Expensive machines could do this in fast forward as well."
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b1y1oc | How does recycling work? | Technology | explainlikeimfive | {
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"text": [
"Paper recycling starts with washing the paper in order to remove the ink. The paper is then dissolved in water in order to create “slurry”. To this slurry different compounds can be added, depending on the type of paper you want to make. Then slurry is spread out thinly and left to dry, which results in new paper."
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b1yt3i | When taking a picture of a monitor or TV screen with a camera phone why does the screen seem to have moving waves and lines even after the picture is taken while zooming in and out? | Technology | explainlikeimfive | {
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"It's called a moire pattern. It's the issue you have when you are looking at something laid out on a grid through a different grid. You end up with a really noticeable pattern of interference that changes as you move the grids relative to each other. & #x200B; Like if you have pixel edges cutting stuff off on a smooth analog picture it's random enough it's not noticeable in most situations, but if you are using one grid to cut off another grid it makes a super super noticeable pattern because it effects a whole line of things the exact same way.",
"Your camera is taking video at a certain rate, and the screen is refreshing at another. The bars and bands represent a mismatch between when the picture is refreshed and when your phone captures it. If your phone is taking samples much faster than the refresh rate, you will see partially drawn screens. If you have shutter control on your phone, set it for less sensitive and take the picture anyway. This will slow down your phone and let the monitor draw and redraw frames while your phone is taking the picture, evening things out some."
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b21oo6 | Difference in generations of i7 processors | Technology | explainlikeimfive | {
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"Cpuboss and cpu.uderbenchmark are great tools for this. Just google 4790k vs 8700k, for example, and those 2 sites will usually be the top results. You can do it with graphics cards, too. As for your question, your CPU is a quad core with hyper threading (so an octa thread cpu). Whereas the latest ones are 6 core 12 thread CPUs running at higher frequencies. As for the unspoken question: There's not really much reason to upgrade, as the 4790K is still a very capable CPU. If you're using the PC for gaming, a new graphics card would benefit you much more, as would 16GB of RAM"
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b23e7v | How does the wifi bridge work on my phone? | The Android system wifi bridge how does it actually work? & #x200B; I am currently sitting in my hotel lobby. I can access hotel wifi on my phone but my laptop is being annoying and refuses to log onto the splash page to click okay. Story of my life. & #x200B; I turn on Android Wifi Bridge. Everything is good right now. But does the Wifi Bridge application actually creates a hotspot? My battery life is still healthy compared to when I normally use the 4G hotspot, so I am curious if the Wifi Bridge is actually transmitting the megabytes as well or is it doing some other kind of IT Black Magicery. Thx in advance. | Technology | explainlikeimfive | {
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"Hey that’s a neat feature! I’m not intimately familiar with the specifics of your phone, but I do have a fair knowledge of networks. What’s most likely going on is exactly the same process that 4G hotspot uses, but only involving wifi. Basically the laptop is connected to the phone via some means (hotspot wifi, Bluetooth or USB cable), on a private network just between those two devices. Any traffic from the laptop destined for the inter webs hits the phone and the phone performs some address translation (NAT) before forwarding it on via the hotel wifi. As far as the hotel can see you’ve only got one device (phone) using their connection. The phone keeps track of the data it forwards on so that when the response comes back, it knows to send it on through to the laptop. As for the battery life - wifi uses a lot less power than 4G does because the base stations are much much closer"
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b23wva | How would a hacker know whether my password only has lowercase letters, or also uppercase letters, numbers and symbols? | Technology | explainlikeimfive | {
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"The reason why they demand that you include upper case, lower and symbols is that if you were to only use lowercase letters, the password would be easy to guess. Most people will use a simple word as their password, if left to their own choice, and with modern systems you can check a password against all of the simple words fairly quickly. Indeed, it isn't any harder to check all words with a capital letter at the start and a 1 at the end, either."
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b24du4 | how do WhatsApp keep being online? | Technology | explainlikeimfive | {
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"One of the most important rules to realise on the internet: if it's free they're (probably) selling your Data",
"Facebook owns Whatsapp and uses some of WhatsApp’s data. If you talk to someone on WhatsApp, they are suggested as a Friend on Facebook.",
"WhatsApp is owned by Facebook since 2014, so technically they don't need any revenue to stay afloat. However they are making money by getting data, which they can sell and/or use for advertising. Supposedly WhatsApp uses end-to-end encryption which means that while the company can't see the contents of your conversations, it does know who you are talking to and when."
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b2505l | How does the ISS never run out of fresh air to breathe ? | Since space has no air in it how can astronauts breathe fresh air inside the ISS? Edit: Thanks anonymous redditor for the gold! | Technology | explainlikeimfive | {
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"**\\[EDIT2\\] This got a little more complicated the more I did research. So for a 5 year old:** The space station doesn't run out of air because NASA got really really good at recycling the things they already have on the station. They have some magic machines up there that can turn water into air. So then where do they get the water, you ask? From the astronauts pee, from their showers, from their sweat, from the humidity in the air. They turn that gross, weird water into drinkable / air-making-able water. BUT eventually they'll run out. SO they send up a fun little gas called hydrogen (which is a thing that's in water, but way way lighter than water and therefore cheaper and easier to send up) and they combine that with the stuff the astronauts breathe out (CO2) using yet another magic machine that makes water. **Full explanation:** Electrolysis of water (H2O) is the main method to generate oxygen aboard the ISS. Water is split into oxygen (O2) and hydrogen (H2). The oxygen is vented into the breathable cabin air system, known as the Oxygen Generation System, while the explosive hydrogen is vented externally. \\[EDIT1\\] Check the edit below, it seems like they don't vent the hydrogen anymore and instead reuse it to make more water. The station’s football-field-sized solar arrays are the power source to electrolyse the water. Each day the OGS continuously provides between 2.3 and 9kg (5 to 20lbs) of oxygen. The OGS is a component of the ISS life support system, known as ECLSS or Environmental Control and Life Support System, located in the US Destiny module. The Elektron system aboard the Russian Zvezda service module performs the same vital electrolysis service for the ISS crew. The Electron system was also used aboard the Russian Mir Space Station. Pressurized oxygen storage tanks replenished by visiting unmanned cargo ships provide a backup to the electrolysis method. Finally, the crew can also generate oxygen chemically by igniting Solid Fuel Oxygen Generation (SFOG) canisters comprised of lithium perchlorate. Each canister provides the oxygen needed to support one crew member for one day. From: [ URL_13 ]( URL_13 ) As for where the water comes from, after reading an article on URL_9 , it's mostly recycled. They have systems that efficiently gather all the water. This includes moisture in the air, sweat, urine, and shower water that was unused. ~~There's also apparently another Russian space station that has a large stock pile.~~ They don't usually ship more water from earth because it's so expensive but they can and do sometimes. The NASA article: [ URL_12 ]( URL_14 ) **\\[EDIT1\\]** I think the idea is the recycling is hyper optimal and also the water that is recycled is all drinkable. I just read some other article (which I closed out of) which mentioned the water tastes like bottled water, although it came from urine. Also /u/ubik2 just posted a good explanation of how the system kind of feeds into itself and how they can get around needing to ship up heavy water to the space station. > Since 2010, they’ve also been using the Sabatier reaction. That consumes the hydrogen from electrolysis and the CO2 from breathing, producing methane and water (which can then go back into electrolysis). This means you don’t have to keep shipping up a bunch of water. Unfortunately, that reaction needs more H2 than it frees (to make the methane), so we still ship that up. Fortunately, hydrogen is very light. As for \"where does the nitrogen come from\" which is necessary for the air, it seems like they ship that up there (couldn't find any magic processes that produce it). > One system is to have oxygen delivered from [Earth]( URL_7 ) via spacecraft. This oxygen is stored in external tanks; similarly, these spacecraft deliver [nitrogen]( URL_0 ) gas, which makes the ISS air supply. From [ URL_5 ]( URL_5 ) BUT it seems like you don't actually need that for breathing. Super interesting! > Nitrogen, a gas that makes up 78 percent of breathable air on Earth, is inert and can therefore be safely stored onboard spacecraft. Despite its high concentration within ambient air, nitrogen serves no particular physiological benefit to humans and only serves to keep the Space Station pressure at 1 atmosphere (14.7 psia). Prior to extra vehicular activities (EVA or space walking), astronauts purge nitrogen from their blood supply to prevent decompression sickness (“the bends”). It is neither important nor practical to reclaim this nitrogen. From: [ URL_8 ]( URL_1 ) **\\[EDIT3\\]** From /u/acorz on how often they fly out the resupplies (unchecked source but they mention that work at the [Johnson Space Center]( URL_6 ) aka NASA). > We fly N2 and O2 tanks 2 or 3 times a year. We fly most of our water once a year on [HTV]( URL_4 ). In 4 years, I've only seen small hydrogen tanks for a science experiments, not resupply. **\\[EDIT4\\]** /u/sharfpang has a really [awesome comment]( URL_3 ) explaining how the Sabatier process isn't actually *currently* used and that they do actually ship the water up. I'm actually not totally sure this is true but they sounded confident (and [this article]( URL_11 ) suggests Sabatier is used). BUT their comment goes into detail with the potential problems that come out of the Sabatier process and some other cool science stuff, so it's worth checking out. **\\[EDIT5\\]** Just a funny tidbit in this research is the Russian side of the ISS doesn't actually use their urine in the recycling process, but the US side does. I feel like I read it in a more credible source, but here's just a [random article]( URL_2 ) I Googled that says the same thing. **\\[EDIT6\\]** Alright back to business. So the plot thickens, /u/sharfpang sourced an [exchange thread]( URL_10 ) comment that makes it sound like Sabatier was a \"success\" which was actually a failure they silently decommissioned.",
"Electrolysis of water. Water is split into oxygen and hydrogen. The breathable oxygen is vented into the cabin, while the explosive hydrogen is is vented externally. Edit: I do not know where the water comes from. Some other comments say urine and air conditioning condensation contribute.",
"I worked on the software that controls Atmospheric Revitalization for the ISS; as others have mentioned it's electrolysis and venting. Since I have nothing else to add, here's a fun fact: You have to heat the venting nozzles before venting otherwise the ice crystals from the rapid change in pressure (i.e. not a vacuum to totally the vacuum of space) will clog them.",
"They absolutely would without regular deliveries of water. As efficient as their system is, it has waste products. Each time it runs a cycle, it loses a little bit of water and oxygen. Without a steady supply, the system will use up all the water.",
"Aside from everything that's been mentioned, many ships that dock with the ISS, such as the Soyuz and the Space Shuttle, have \"puffed up\" the Space Station with some air from their stores, or have specifically carried extra gas from Earth to add to circulation.",
"There’s a regenerative cycle as others have mentioned that uses electrolysis to create oxygen. Also there are contingency tanks which can be used to resupply cabin. Source: I’m currently working on the sustaining ISS Water team and WHC team.",
"The real question is, how do they not run out of water? That’s what makes the O2.",
"On a related question, how much plant matter would need to exist in the ISS to recycle the CO2, if they used that method instead of the current one?",
"People here are all pretty much correct, but they're missing some of the complexities that come with designing a spacecraft cabin atmosphere. The ISS uses a 14 psia mix of 20% oxygen and 80% nitrogen in order to better replicate a terrestrial environment for science. The nitrogen is just a buffer to keep the pressure up, but other space missions such as Apollo flew with 5.5 psia 100% oxygen atmospheres. A lower pressure lets you make a lighter spacecraft that leaks less, but the ISS is really good at not leaking anyway. The nitrogen is brought up bottled I think, and because it never really goes anywhere (you breathe it in and pretty much just breathe it right out) they don't have to replace it often. However, a human body *does* use up oxygen and produces CO2, so they need to replace that. The modern system on the US side of the ISS is called CDRA, and it absorbs CO2 from the atmosphere that the astronauts breathe out and concentrates it. They then use the [Sabatier reaction]( URL_0 ), where they add hydrogen to the CO2 and heat both. The result is water (H2O) and methane (CH4). The methane can be vented and the water is electrolyzed into molecular hydrogen and oxygen. I don't recall if the hydrogen is vented overboard or reused in the Sabatier reaction. This whole process is complicated and for short duration spacecraft like the Soyuz, plain bottled oxygen is used along with a lithium hydroxide canister to just absorb CO2. In addition, there's pressure, temperature, humidity, and trace gasses (like farts, smoke, etc) to keep under control."
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b256vs | What makes the iPhone more secure than other phones and how do people still hack it? | Technology | explainlikeimfive | {
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"Some if the security features like hard drive encryption are enabled by default on a current model iPhone. Most of the same features are available for an Android, but are not the default. Sometimes you need to use a different app altogether in order to get the best security on an Android. In some cases the default apps and settings on both devices aren't the best choice out there, but a new iPhone has more security enabled by default than a typical Android. I'm not aware of any Android manufacturers who advertise security up front, that doesn't seem to be what sells (sadly)"
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b27k4v | Why do electronics usually require 2 batteries instead of just one bigger battery? ie: 2 AAA instead of 1 AA. | Technology | explainlikeimfive | {
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"It's to do with the voltages at play. The common battery sizes -- AAA, AA, C, and D -- are all 1.5V. If you connect two batteries in series, you increase the voltage. So, 2 AAA batteries have a total voltage of 3V, compared to a single AA battery with a voltage of 1.5V.",
"TLDR: Batteries are often chosen to optimize size + weight of the device. AA, AAA, C, and D batteries all have the same voltage (1.5V), the major difference between them is how long they last. The larger the battery the more energy storage it has, so the longer the battery will last. You can replace the batteries in a device with similar batteries that have the same total voltage. So 2x AAA's = 2 x 1.5 = 3 volts. So if a device is powered by 2x AAA's, you can replace them with 2x D's which would make the device run much longer. BUT the catch is those D batteries are huge and would make the device very heavy and cumbersome. The reason most devices run on AA's is size + weight.",
"An AA battery is bigger in capacity than a AAA battery but both are at the same voltage. Think of voltage as water pressure and capacity as the amount of water in a water tank. You're lifting water into the air with a water tower so that you can get water pressure to run your shower. An AA battery would have a larger water tank but both AA and AAA batteries would have the same height. By stacking two AAA batteries together, you double the voltage so essentially, you get a water tower with twice the height, doubling the water pressure. A single height water tower would cause a small dribble out of the shower nozzle but with two, there is enough water to properly shower. Why 2 AAA and not two AA? Generally, there are size and weight requirements for the device. So why two batteries worth of voltage? Each battery is 1.5 volts so two stacked gives you 3 volts. Many electronics require about 3 volts to be powered. Nowadays, there are some electronics that can be powered with a single battery because of the progress we made in shrinking our electronic building blocks."
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b29l8t | Why does it seem like only a few mobile games appear in almost all mobile game ads ? | Technology | explainlikeimfive | {
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"There's actually several factors: 1 Remarketing, 2 Look-alike targeting, 3 Profile targeting 1. In remarketing if you ever demonstrate a whisper of interest in a product they will seize upon that and bend the powers of targeted advertising towards prolonged exposure. This is most common and annoying when you sign up for or buy something you want then see ads for it everywhere. Lazy remarketing flagged you as a hot lead without also tagging you as a customer. Yes Amazon, I did just buy one of those thanks for reminding me. 2. Look-alike targeting is where that magic happens that makes you SURE, JUST SURE that Facebook and Google are listening to you through your microphone. It actually takes two forms. The first form is a super secret black box that Facebook feeds data into, it compares you with millions of other people and figure out people who browse and shop like you do. So it someone already identified as like-you starts playing X game, they will start targeting you as a look alike. The other aspect is proximity. If it geolocates you with a friend, it will assume you will talk about things. So for example when I saw a guy I hadn't seen in a while and he said his son started karate lessons, wouldn't you know it I started seeing karate ads even though I never looked it up once. They assumed right we'd talk about it. Creepy. Yeah. 3. Profile targeting is kind of old fashioned but say an advertiser says they want someone who follows the EA Sports Facebook page AND college football teams. You'll be targeted by that advertiser more than advertisers who just say college football teams because you're a more specific match."
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b2ao8w | why is there a lower limit to brightness on your smart phone. Why can’t they make it so that you can keep on turning it down till your phone turns completely dark ? | Technology | explainlikeimfive | {
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"Designer: Hey! Let's make it so the user can turn the brightness all the way down! Boss: Great idea. Are you volunteering to go sit your ass down in that chair, put on the headset, and spend the next 5 years fielding nothing but support calls from angry customers? Designer: But we'll have obvious ways to reset the brightness. They'll be intuitive, they'll be spelled out in the user manual, and we'll put it at the top of the FAQ on our website. Boss: Go spend an hour in support right now. See what questions our users are already asking. [an hour later...] Designer: Holy fucking shitsnacks. Never mind.",
"The biggest reason: if you could put it to completely dark, how could you ever turn it back up since the control is on the screen itself?",
"How would you get higher brightness again, after turning it to 0 making your screen completely dark?",
"Sometimes people don't think of the obvious! Relax, folks! That said, yes. The most likely reason is to keep the controls visible since all controls are on screen. Theoretically, the only time one would need the screen completely dark would be if they were turning the phone off. Further, the LCD screens on phones aren't designed to reflect the light that hits them in a diffuse pattern (randomly scattered, like from a frosted light bulb or light bouncing off skin) and instead tends to bounce reflectively from the surface glass. Since the light is mostly absorbed by the dark panels the liquid crystal material is stored in (the black stuff that oozes from a shattered screen), and reflected by the smooth glass screen, while also being polarized on it's trip into and out of the glass, the amount of visible light that escapes the phone in even the brightest light can appear black. Even if some of the image shows, there is usually a reflection on the screen obscuring some of the image. In short, phones are simply not designed to be used with front lighting, so the backlight must be kept on at least a little bit to ensure the screen and its controls are all visible.",
"The light sources behind your screen only turn on over a certain minimum current is going through them and so the screen can't be dimmed arbitrarily. Basically, you would try to dim the screen and at some point it would just turn off."
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b2bggp | how is it possible to contact emergency services when there is no connection to a mobile network? | Technology | explainlikeimfive | {
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"There's no signal on your carrier's network, but there may be a signal on another compatible tower operated by a different carrier. By federal law, cell networks must connect an emergency call from any phone capable of speaking to that tower, regardless if that phone has an active service plan with that carrier."
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b2ci5v | Why does old electronics make crackling noices when they get turned off? | Technology | explainlikeimfive | {
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"Because when the device is on it creates heat and it expands and when you turn it off it starts to contracts. Just like the ticking when you turn your car off from driving"
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b2cpl9 | When the FBI seizes a domain and a website why do they put an image saying the site has been seized instead of just deleting it completely? | Technology | explainlikeimfive | {
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"To let people know what they are doing and to put a deterrence in the mind of people who might be using some sites for illegal activities, since the FBI might be tracking their activities.",
"There’s a potential for more data to be captured from those who visit afterwards than they could capture from a DNS lookup for a nonexistent domain."
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b2d1du | Why arent robots smart enough to check the “i am not a robot checkbox”? | Technology | explainlikeimfive | {
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"It's not just the act of clicking the box that is observed, but the **how** the box is clicked. In other words, a few other factors like the movement of the mouse up to that point are checked to determine if an additional challenge should be given.",
"They are, but it takes time. The check box is checking a number of things related to you moving the mouse and clicking it. It's very easy to build a bot that can recognize the box. It's also easy to train a bot to simulate moving a mouse. But the check box is set to recognize when the mouse cursor is moving too fast or instantly teleporting. So it might take a couple of seconds. The box is there to stop a bot from doing things dozens of times PER SECOND.",
"It not that the robots can’t check it, they can. It’s the speed they check it and how they move. The use data samples to determine wether it is a human or not and lighting fast then they can determine it is a robot.",
"Also sometimes when the Captcha is not sure / randomly it will make you select some images that contain x or make you type in some letters that look jumbled on the screen. A robot usually cannot get passed these, but it is quite easy and simple for a human.",
"[This]( URL_0 ) is the correct and definitive answer to your question. Basically, you only see a box where in fact there is an invisible image behind it and a lot of tricks, including a double encryption in a language where the key changes as it reads the encrypted content. Read the article I linked, it's actually ELI5 and illustrated."
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b2e36d | How to make a bot that responds to specific comments? | Technology | explainlikeimfive | {
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"text": [
"Do you have any programming experience at all? The fact that I’m not seeing you mention it means you must be asking for an entire tutorial on learning a scripting language and then making the bot, right?"
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b2efkk | How does a microphone work | Technology | explainlikeimfive | {
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"text": [
"The sound pressure from your speech (or whatever it is you're recording) causes a little magnet called a voice coil to move in and out within another piece of wire. A moving magnetic field generates an electric current that exactly corresponds to the magnetic field, and since the magnetic field was created by pressure from sound, the electric field exactly corresponds to the original sound."
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b2en5b | Batteries. What's the difference between volts and amps? How does a charger know when a battery is fully charged? | As a specific example, I have a drone that takes 3.7v and 500mAh, but I can use 3.7v and 750mAh batteries for it (from another drone) and it works just fine. Does it fly longer. Another example is that my daughter has one of those electric cars with a 6v 5amp battery in it. I replaced it with a 12v 5amp battery and it goes twice as fast. If I used a 6v *10amp* battery, would it go the same speed but for twice as long? Oh, and if I connect two batteries, what's the difference between connecting them in in line (pos to neg) as opposed to side by side (pos to pos, neg to neg)? | Technology | explainlikeimfive | {
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"There are three different, but related quantities you’re asking about when it comes to batteries; - How ‘strong’ is your battery? Measured in Volts - How ‘fast’ can your battery go? Measured in Amps (or milliamps for smaller batteries) - How much total energy does your battery have? This is determined by how long it will last when it goes given a certain speed. We measure that in Amp-Hours or milliamperes-hours (mAh) Batteries will always push a circuit as hard as they can (use all their Volts). But how fast a circuit goes depends on its resistance. A high resistance circuit will not run as fast (i.e., it uses less Amps). Using a battery with the same strength (Voltage) but more or less total energy (mAh) just changes how long a device will run - there isn’t any risk or other effects on its behaviour. Using a battery with a different strength (Voltage) can change how a circuit behaves and has some risks of damaging the device. In the example of your daughter’s car, we can probably assume it has a fairly simple dc motor circuit in it. When a battery tries to turn a dc motor, how fast it goes is proportional to the strength (Voltage). If you double the voltage, you will double the speed (as you observed) - you also doubled the Amps being drawn from the battery. This means if your 6V and 12V battery both had the same mAh, the 12V would run out of energy twice as fast (because of the faster running circuit (higher Amps)). So, the car is more fun, just not for as long... But, there is also a risk - running faster with a stronger battery means it’s consuming higher power, and heating up, which might cause the motor to burn out completely. Then the car is no fun at all :-(",
"mAh (milliamp hour) is a measure of capacity, whereas voltage and amperage are measures of energy flow. Voltage is a function of the battery (think of it as electrical \"pressure\"), amperage is a function of the circuit that it is hooked to (equivalent to how far open the taps are). Hooking up a higher voltage battery to a circuit can be dangerous and cause damage to the electronics, but hooking a battery with the same voltage and higher mAh will just cause the thing to run longer before it exhausts the battery.",
"The capacity of the battery is like the capacity of a bucket. If the battery holds 500mA*hr and you drain it out at a rate of 1A, it will last half an hour. The 750mA batteries will last 50% longer under the same load (though they are presumably heavier so the drone has to work harder...). Be careful with Amps and Amp Hours. They are not the same thing at all. In this case you probably mean 5 AHr and 10 AHr in which case, yes, the 10AHr battery will last twice as long. On the other hand, an automotive starting battery has a rating \"cold cranking amps\". This described the maximum current the battery can deliver over a few seconds and *has nothing to do with the size of the battery*. A deep cycle might be quite a bit bigger (and have much more capacity) but it probably can't deliver it is as quickly. A couple of simple and useful equations: V = IR. Voltage (Volts) = Current (Amps) * Resistance (Ohms). P = IV. Power (Watts) = Current (Amps) * Voltage (Volts). The resistance is determined by the load (the drone or the electric car). So doubling the Voltage without also modifying the car made it twice as powerful."
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b2g6uh | Why when you take a picture of a screen does the camera puck up lines on the screen that you cant see? | Technology | explainlikeimfive | {
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"Computer displays don't display the entire image constantly. They display alternating lines of pixels at a pace of the refresh rate of the monitor (for instance a 60 Hz monitor switches between the even lines and odd lines 60 times per second). Since a picture taken with a camera is a singular moment in time, only the lines that were 'on' when the picture is taken are displayed."
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b2imoz | How does wireless connections actually work? I mean, how is the data transferred without physical connection? | Technology | explainlikeimfive | {
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"With radio waves, which are basically an invisible form of light. Instead of the electrical signals (current) traveling through a wire, they go into an antenna, where the current is sloshing back and forth. Electrons moving back and forth like that creates waves in the electric field that travel through space. That's what light is. The receiver is just the same thing in reverse. The waves traveling through space cause the electrons in the receiving antenna to move in the same pattern, so the information has been transferred. Imagine two floating balls on opposite sides of a pond. Move one ball up and down and it creates a pattern of waves. When the waves reach the other ball, it will move up and down with the same pattern. It's the same concept, just a different medium."
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b2kfu8 | How do they take super old movies/footage and remaster it to 1080p HD or even 4K UHD? | Technology | explainlikeimfive | {
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"A lot of movies were shot on film which have much higher resolution then a standard definition TV. It is only recently that movies are being shot on digital camera. So when you visited the movie theater in the 70s you were watching something at about the same quality as modern 4K monitors. By just scanning these films again in a higher resolution you end up with a high resolution movie. Remastering is a different independent process. People have been remastering movies for a long time. Just look at the controversies of the Star Wars remasters throughout the years. Remastering is the process of taking the movie back to the editing studio and make changes. Maybe the changes you are doing would be impossible or too expensive with the technology at the time. A lot of times the colors of modern systems can be brighter then they were before. And sometimes the movie would be better with some CGI changes."
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b2ltnf | How does a digital scale operate? | Technology | explainlikeimfive | {
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"There's a tiny accordion of metal foil encased in a nonconductive flexible backing. An electric current is run through the metal foil, and the resistance is measured. As the accordion is pushed together by the weight on the scale, the resistance changes according to a known mathematical formula, allowing you to calculate the weight based on the resistance measurement. This accordion assembly is called a Strain Gauge."
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b2lzdl | what caused the iconic old dial up internet tone from the 90s? did someone design that sound digitally or is that some sort of analog tone generated from hardware? | Technology | explainlikeimfive | {
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"If you've ever gotten a call from a fax machine, it'll sound familiar. That's the actual audio being send through the phone lines, being used to encode the data that on each end, gets turned back into a digital signal.",
"dial up uses sound to transfer data. that's just the sound of your hardware talking to the server. that sound continues for as long as you're connected, it's just that your modem mutes it after the initial connection. it's the same way touch tone phones can recognize what numbers you input, when you press a number it creates a different tone based on what you pressed. so while someone did design the sound of the various logic values, what happens afterwards just depends on what data is being transfered."
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b2mo7u | How doesn't my cars remote work on other cars? Like how isn't there another car with the same frequency if its even based on that? | Technology | explainlikeimfive | {
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"they use the same frequency sure. but there are unique identifiers in the transmitter and receiver. only if the transmitter sends the correct code the receiver is expecting does it unlock. for cheap systems, these are hardcoded so anyone that knows the correct code can unlock the door. thieves could monitor wireless signals capture the code and duplicate your remote. for more expensive systems, the transmitter/receiver can change the codes. & #x200B; it's like cell phones, they all operate over the same frequencies, but there are unique sims or esns for each phone. key fobs sorta work like that but are less complex."
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b2u5dr | How can a software be open source and secure from hacking at the same time? | Technology | explainlikeimfive | {
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"Here's my code #1, I checked it with a few of my mates, and we don't think there's any vulnerabilities. You'll just have to trust us, because I don't want you seeing the code. & #x200B; Here's my code #2, thousands of coders throughout the world have studied it and nobody has found any vulnerabilities. But if you still don't trust us, you're free to check for yourself. & #x200B; Which one do you think is more secure?",
"Imagine a vending machine with a 2-bit CPU and a program that just says. 1 WAIT FOR COIN 2 DISPENSE SODA 3 GOTO 1 If the company publishes this code, there is nothing a hacker can do. It doesn't matter how many ethernet ports are open to the world, because there is simply no path through the software that will make it dispense a soda without a coin. Hackers must resort to trying to physically modify the machine. In the same way, open source software can be secure if there is no set of data that can be given to it that will put it a state not intended by the designers. It doesn't matter that the hackers see the code - there's simply no external influence that will make the code do something hackery. Now, whether this is really possible is debatable. There are many cases where a state is considered valid but has unintended knockon effects elsewhere, or was considered valid by designers but not users, or was considered valid simply by mistake. There are even cases where within the semantics of the language software is perfectly secure, but because of the hardware it's running on it becomes insecure. However, history has at least shown that closed-source software doesn't really have an advantage. Hackers are just as good at exploiting an opaque binary as they are a large codebase, as both still involve some creativity to see flows that were not intentional.",
"This is the patent [US3035433A]( URL_0 ) It's the patent for a lock. You knowing how the lock works, does not make it significantly easier to pick. In fact, having a bunch of people looking at it could lead them to spot things you got wrong and tell you about them so you can fix it.",
"imagine a well-guarded castle that you can only enter if you stand on the drawbridge and say the password -- which changes every day. now, imagine someone gets their hands on the employee handbook for the castle guards. it has rules for when to walk the castle's perimeter, when and how the new passwords get disseminated by the captain, how to ring the bell when an intruder is detected, and so on. what does this buy you, if you want to get into the castle? nothing, if the castle's security is actually good: you still don't know the password, and now you might even realize the whole perimeter is on watch 24/7. that said, if there's something in the book that says something like \"if they claim to be the Marquis of Blahblahton, just let them in. that guy never knows the password\", well, that's a security problem, and you just got a shortcut to knowing about it. with software, it's the same way -- the source code just tells you the rules of how the thing you want to get into will behave. if the rules are properly done, that shouldn't make it any easier to actually get into it.",
"It peer reviewed and fed back by the rest of the world. Closed source is compiled and sent out with only proprietary checks on the code. This means some bugs and vulnerabilities get through.",
"Because there are just as many (if not more) users and experts looking at the code as there are hackers. If you use open source software, and you encounter a bug or security hole, you'll probably report it to the maintainers along with your fix. T If you kept the info to yourself, you'd have to reapply your fix every time you updated your system to the new official version."
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b2yjff | Why do small screens have a better resolution than bigger screens? | Such as my laptop, with a 15 inch screen, which is 1080p, but my phone, with a very tiny screen relative to my laptop is 1440p? | Technology | explainlikeimfive | {
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"You're looking at just 1 phone, and just 1 laptop screen. Look at ALL screens, and you will see you can get just about any screen resolution in any size you want. We now have tv's that are 8k, which is 4320p, and you can get them in 72\" at any place that sells new tv's. However, you correct if you are thinking about it in terms of \"pixels per square inch\" of screen. In that context, yes, larger screens tend to have fewer pixels per square inch. And as /u/gman5495 pointed out, that is because you will be much farther away from a big screen than a little screen. This is done so that from your viewing perspective, everything looks similar.",
"Because your face is closer to it. If you put your face up close to tv you can see the pixels if you put uour face up close to a computer monitor you can kind of see them. If you do the same with your phone you cant because it was designed with yhe fact in mind that users would be less than foot away from the screen."
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b2yt8d | How is it possible for 2 devices to communicate without wires?! Bluetooth, WiFi, telephone...?! | It’s so mind boggling that somehow, even without wires connecting me from me to you, we can communicate. How does something transfer from one entity to another?? When I was a kid, with a wired phone, I always thought that the ways phones worked was that my audio traveled super fast through the wires outside my house to whoever I’m talking to. Probably not how it works, but that was my comprehension of how a telephone works. But now I can communicate with a device smaller than my hand to millions of people at once, without any form of physical communication... MIND BOGGLING! How does it work? | Technology | explainlikeimfive | {
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"Both devices have an antenna that resonates. The transmitting device sends the signal by encoding it in subtle changes to the vibration of the antenna, and the receiving device picks it up by listening on the same frequency. & #x200B; It is worth noting that cell phones rarely, if ever, connect directly to each other. You instead connect to a nearby cell phone tower, which relays the information along the (usually wired) network to the cell tower nearest the recipient's phone. This is why if two of you are lost in the woods with no cell signal, you can't call each other with your phones.",
"Actually, fairly similarly to the way they do with wires. When you've got a digital device talking to a digital device over a wire, you're translating the digital information into electrical signals (analog) and transmitting it over the wire, where it's re-encoded on the other end as digital. Wirelessly, it's basically the same thing only instead of sending the signal through a wire, you're sending it through an antenna (which incidentally, is for many devices just a wire) where it's transmitted over the air as radio waves on a pre-defined frequency."
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b34y91 | Why are we improving hardware instead of optimizing code? | Technology | explainlikeimfive | {
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"This is a systemic problem in the industry... To paraphrase XKCD \"I don't know how to tell you this, but everyone in IT is secretly terrible at what we do.\" There's only a handful of companies making hardware, but everyone and their dog are writing code. Improving hardware is a logical progression, it would happen anyway. On the other hand much of the development industry is driven by philosophies like Agile which are all about rapid delivery rather than quality. It's more important to deliver the new product or feature than to fix things that don't work right. This leads to a state where the vast majority of programmers aren't interested in optimizing code, they are only interested in getting code to work because they either don't care, don't know, or are too rushed to be bothered. On the flip side you have guys like Linus Torvalds (who is ultimately responsible for the Linux Kernel). Linus takes code from contributors, re-organizes it to make it more efficient, and then does it again once the code is compiled into machine language. Very few people on Earth have the skills and know how to even be able to do that. Unfortunately guys like Linus are few and far between, and he's not a particularly good teacher either. In a few decades the industry will be critically short of people with that kind of knowledge and first hand experience working in machine language because programmers these days aren't taught those skills. That was very much a 70's and 80's thing. Well guess what, those programmers and going to all die soon!"
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b38xgb | How exactly does heat make batteries discharge faster? | Technology | explainlikeimfive | {
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"Batteries generate electricity via chemical reactions. Chemical reactions rely on molecules that would like to interact bumping into each other. For some reactions they have to bump into each other with enough energy to overcome their natural stability enough to cause them to undergo a reaction (eg. wood oxidizes very-very-very slowly in air, but given enough energy(heat) it reacts violently with air as \"fire\"). Cooling down a battery makes it harder for the chemical reactions to happen, as everything becomes more stable with the lower-energy bumping around. Conversely heating up the battery pushes the reactions to happen more often, possibly to the point that un-intended reactions start to happen and the battery explodes."
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b3ae64 | How does the crease-free setting of a dryer work? | Technology | explainlikeimfive | {
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"All the most common \"crease-free\" setting does is keep the temperature up in the dryer and spins the drum back and forth once a minute or so - in order to stop the clothes from settling in one spot and forming creases. It just buys you some extra time between when the clothes are dried (i.e the main cycle) and when you need to take them out the drier. It is a terrible waste of electricity though."
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b3as0t | If we can see cells with a microscope, why can’t we just keep adding lenses/magnification to see atoms fairly clearly (with electrons etc.)? | Technology | explainlikeimfive | {
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"We can only see things by bouncing light off them and then into our eyes. Lenses help us focus light so we can see smaller things, but evsntually, the things you're looking at are smaller than the wavelengths of light. Light itself has a size and you can't bounce it off things that are smaller than it and get a good picture. We can get around this a bit by using electrons instead of light, But even that has a limit as well. We'll never see things like quarks, they're just too small.",
"Lots of good comments here already about how the wavelength of light is a limiting factor for conventional microscopy. It's worth mentioning that we can \"see\" things smaller than that, but through indirect means. One such way is by using the power of X-rays, which have a much shorter wavelength than visible light, such that the X-rays interact with the electrons of molecules. Growing crystals of something and then measuring how these X-rays are scattered is the basis of a method called X-ray crystallography, which is regularly used to \"visualize\" (or more accurately build models that are consistent with the data) to \"see\" what proteins and nucleic acids look like on an atomic level.",
"There’s even something else that comes into play before what the top comments are mentioning. If you zoom in with a microscope, you’ll notice that the image gets dimmer and dimmer the more you zoom. That’s because light from a smaller and smaller area is being spread out to your entire field of view. At some zooming point, there will be almost no photons to even produce that image, and this point is far before the wavelength of light. EDIT: Hmm, I guess it’s not that far before the wavelength of light. And you can of course just pump more light in. But the image quality definitely degrades a lot due to the limited amount of light, and using too much of a high energy bulb could come with other effects as well.",
"Just because atoms are smaller than \"light\" we use to see. it's like trying to catch a bug with a net with big holes, it won't work.",
"Light is a waves that have larger wavelength then the size of a atom. & #x200B; The wavelenght of visible light is 380-740 nm. A larger atoms have a diameter of 0.5 nm and the smaller hydrogen have a diameter of 0.05nm. & #x200B; When a wave interact with object that is smaller then the wavelength it will diffract. So light start to bend around object and other effect so the result is that you cant use light with microscopes for sizes below 200nm. So light can pass around a small object and you cant see it is a way to look at it. The minimum object you can see depend on the wavelength. & #x200B; If you use electrons as the illumination instead of light you can ave a resolution smaller then 0.05 nm & #x200B; All particles can be looked at as both particles and waves. The wavelength of a electron will depend on the momentum and when used in electron microscopes the momentum depend on the voltage you use. At 200 000 V the wavelength of a electron is 0.0025nm and that is smaller then a atom. So in some condition you can see individual atoms with a election microscope. & #x200B; & #x200B; Wavelength also determine size of antennas in radio communication. Lower frequency require larger antennas. So cellphones that can receive FM radio need to have the headphones inserted because it is used as the antenna. You cant have a good antenna builtin as the phone is to small.",
"The way we see things is by light reflecting of of it into our eyes. Lenses take reflected light and make the image appear bigger. In order for the \"reflection\" to work the wavelength of the light has to be smaller than the object. This isn't a problem with anything we interact with in the normal world because everything is massive compared to wavelengths of visible light. The problem is as you try to view something small, like cells, you need increasing smaller wavelengths of light. For most cells visible light is fine as they're still quite big. The problem is on an atomic level the wavelength of light is too big compared to the object, it will just go around it. If you keep adding lenses there will be no visible light for the lens to make bigger.",
"With current technology we actually can use a electron microscope which uses a stream of electrons to help show what we are looking for by stimulating what we are looking at with electrons. Currently you can see a neutron and proton but unfortunately with current tech we cannot see a electron. On the bright side who knows what we will be able to see in 50 years! Technology has a way of rapidly improving. So to answer ELI5 our equipment isn’t good enough yet",
"This is what I do my research in! How light bouncing off electrons is used in optical microscopes has already been answered, so I’ll just add some neat facts about how we CAN see (or rather, make images of) things on a smaller level. There’s a branch of equipment called Atomic Force Microscopes (AFM) that have levers with tips that are only a couple of atoms wide. That tip is brought in contact with the surface of a sample and is dragged across it. The equipment can sense the very small movements of the tip and use that information to draw a picture of the surface. This is great for characterizing samples that we have put a material on, and determining if it is smooth on an atomic level. It’s a little more nuanced than that, and different kinds of technologies can incorporate other things, like running a small electric current through the tip and into the sample, but that’s the gist of it. Hope that helps! :) EDIT: fixed the microscope name to be correct",
"It's essentially the idea that you're only as accurate as your tools. Microscopes use magnified lenses, as well as \"Light\" to help focus the certain wavelengths of light. The light passes through the magnified lenses, bounces off the object, and feeds back into our eyes, which is how pretty much how all human eye sight works. However, if the object you're looking at in the microscope is smaller than a wave of light, it won't be able to reflect light and thus we cannot see it in a microscope. It's sort of like if you were to try to measure a grain of sand with a 12 inch ruler. & #x200B; The Electron Microscope was invented to fix this. Electron microscopes work in a way to mimic how our eyes receive and translate light. While regular microscopes rely on shooting light through the magnified lenses reflecting back into our eyes, Electron microscopes work by shooting electrons through a magnified lens. The electrons then bounce/reflect off the object, and the angle/impact of the electrons on the object can be reverse calculated to determine the shape and size of the object you're trying to look at. Electrons are smaller than light wavelengths, so the electrons are able to reflect back off super small objects that normal light wavelengths wouldn't reflect off of. & #x200B; & #x200B;",
"Light microscopes work by shining white light (or sometimes single coloured light) against an object, and letting it bounce off a mirror through our magnification lens. This is great when the object we want to see, is big. Our issue is with light, not the object. Light is understood to be a particle (the photon) and an energy wave at the same time. Different colours of light have different characteristics to their energy waves. One of which we call a wave length. Higher energy light has shorter wave lengths. Blue and purple are low wave-length, and red is high wave length. This is part of the reason the ocean looks blue. Red, with a high wave length, is more easily knocked off course than blue, so you lose red light faster. With our microscope, an object like a cell is 1000-10,000 nanometers (billionths of a meter) in size. A light wavelength would be between 400 and 700. Because the cell is bigger, it bounces a lot of light off for us to collect and see. The smaller an object is, the less light it bounces off. So we make up for it by using smaller and smaller wavelengths as the object gets smaller. The rule is, when your object is smaller than the wavelength of light you use to see it, you probably won't see it. Once an object gets past the wavelengths for light, we might use something like X-rays (~10nm). Thats great for seeing single proteins (around the same size) or structures. An atom is around the size of 0.1 to 0.5nm in diameter. We simply don't have tools which can produce a wavelength that small, with enough power and enough precision to view an atom. To quote Scotty, \"...like trying to hit a bullet with a smaller bullet, whilst wearing a blindfold, riding a horse.\"",
"because light itself is a small particle(kinda) and the way we see is by catching those particles(photons) that bounced off of objects. this works because photons are incredibly small so they dont affect anything we see really. but at atomic scale photons arent that small anymore so they can interact with things like atoms. so at an atomic scale seeing using light would be like determining the distance of a beach-ball by bouncing another beach-ball off of it"
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b3dhrm | How do electric cars work so it supplies enough energy to the car? | To my knowledge normal gas cars have to make continuous explosions (via the otto cycle) to make energy to make a car run, while electric cars dont (or so I'm assuming) so I'm wonder how much power does an electric car need to make it function? Also gas cars have a battery, so why cant that thing be used to power a whole car like an electric car Edit: essentially what I'm asking is for the difference about gas and electric cars that makes one run purely on electricity. | Technology | explainlikeimfive | {
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"Electric cars use an electric motor (or multiple motors in most cases) The electric motor is powered via electricity by energizing elector magnets that basically push and pull causing the motor to turn. Attach a wheel, and you've got something to strap into a car. Your battery in your gas car doesn't provide nearly enough energy to propel your car any respectable distance.",
"Electric cars have much more powerful and much larger capacity batteries than gas cars. The battery in a gas car is only needed to make a small spark in order to ignite the gasoline, so it doesn't need to store enough energy to power the whole engine on its own. A typical number for a car battery (it'll vary a little depending on the car and the battery you buy) might be around 480 watt\\*hours (watt\\*hours is a measure of how much work the battery can do). A 2017 Tesla battery pack is rated at around 100,000 watt\\*hours, which is 208 times more total stored energy. This isn't the only important part. They're also designed to be able to release a lot more of that energy safely at once. It won't be able to keep up with the power requirements of a large electric motor like you'd find in a Tesla."
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b3dpuq | Programming Concurrency | Technology | explainlikeimfive | {
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"Computer processing is like cooking. In the past, computers operated like household kitchens with a single cook. It was straightforward to list out all the tasks needed for that person to make food: prepare ingredients, cook them, plate them, and wash dishes. Computer companies focused on making the cook work faster and faster until they got to a point where the cook reached physical limits and ended up overheating. So computer companies changed tactics and added more cooks to the kitchen (multicore). This should have sped things up but assigning work to properly utilize them got more difficult. You can have them all chop up ingredients but if you only have one stove, you're stuck waiting for dishes to cook one at a time (bottlenecked). Or you can have some cooks wait for plating but forget to prepare one ingredient so the cooks never end up doing anything (deadlocked). Concurrency is a way to properly assign tasks to the cooks so that they can produce the most amount of dishes without being deadlocked or bottlenecked.",
"Computers are electrical machines. Interestingly, Charles Babbage designed a digital computer using clockwork mechanics in 1837. Though he never built the machine, one was completed around 2010-2012 and was on display for a few years; it now exists in a private collection. That machine works. It's Turing Complete, which means it is as computationally powerful as a modern super computer. That may sound misleading, but what it means is there's nothing a computer today can compute that this mechanical machine can't, modern computers just do it faster. Charles Babbage called his machine an engine, and ultimately that's the analogy I'm gunning for. You can think of the computing core of a modern computer processor as an engine. A decade ago, computers had only one core. This means the computer could only do one thing at a time. Sure there's fancy technologies like pipelines, where multiple tasks that take multiple steps can be ordered in the pipeline so that they're all at different stages of completion, and then the results are re-ordered and presented to the program as though they happened in turn. There's also the concept of multitasking, where each program you're running gets a small time-slice of the CPU, and they switch out frequently, approximately every 25 microseconds. This gives the illusion that all your programs are running at the same time but they're not! They each get a turn to run for a little bit. Enter the modern era, where miniaturization has just about bottomed out. There ain't much smaller to go, because we're putting transistors and wires on silicon that measure in tens of atoms across. Other than increasing manufacturing precision and managing heat, it's getting a lot harder to make processors faster. We used to call this the \"Free Lunch\", because if you wanted to make your programs faster, you could either write the code better, or you could wait for faster hardware to hit the market and upgrade. I'm a software developer, BTW. As Herb Sutter once said - a programmer of some fame in the industry, the free lunch is over. So to get faster, the idea is to do more work at the same time. And the hardware engineers have had all sorts of strategies to do that, some I mentioned above, hyper threading is another one, where any unused work unit, like a pipeline stage that finished early, could be given cheap work that was available to do (like integer addition, if you're a pipeline stage and you're just a couple steps from the end, integer addition can be done in a single step so it's a good use to fill the void). The other thing to do is add more CPUs to the machine. With multiple CPUs in a machine, now you can ACTUALLY do multiple things at once. Now you can have two programs executing literally at the same time, or maybe one program that was designed to do multiple things at once, like draw the latest video frame to the screen and communicate with a server. At first, computers had literally multiple CPUs plugged into sockets on a motherboard, but now we can put multiple CPUs on a single silicon wafer. And we can even combine the two ideas and have multiple multi-core CPUs in a machine, if you fancy, and can afford... Concurrency means things are happening at the same time, but that doesn't mean they're happening together. There's a separate concept called parallelism. And parallelism is where multiple of the same operation happen at once. For example, your GPU and certain bits of your CPU can both perform math multiplication at once. One step, and a whole bunch of numbers all get multiplied, the results all come out at the same time. Parallelism is important in math heavy things like games and simulation, where you want to do something very simple a whole bunch at the same time, and you have, say, multiple multiplications that are all independent of one another. Concurrency is a bigger concept of multiple programs or, in a sense, multiple actors all jumping around and doing different things coincidentally at the same time."
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b3g9tz | How do stealth fighters like the F-22 or F-35 work? | How does the stealth technology in these aircraft work? | Technology | explainlikeimfive | {
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"Radar works by sending a radio wave out. The radio wave hits the surface of an object and is reflected back at the radar station. It measures the time it takes for the radio wave it sent to get back and that tell you how far away and in what direction an object is. & #x200B; Most airplanes are made of rounded shapes. So not matter what direction the airplane is facing there is always a part of the plane that can reflect the radar signal back towards the radar station. The stealth airplanes are made up of flat surfaces. When radar hits the flat surfaces the radio waves are not reflected back to the radar station but they are reflected away instead. They also use materials on the surfaces that help absorb the radio waves instead of reflecting them. Stealth airplanes are not 100% invisible there are certain angles that the radar can hit the aircraft and reflect straight back to the radar station so that it can detect it. & #x200B; If you have a reflective ball like a Christmas ornament you can see the process illustrated with light waves instead of radio waves. Because the Christmas ornament is rounded you can see your reflection in the ball no matter what angle the ball is from you. But if you take a flat mirror you can only see your reflection if you are facing the mirror at a very narrow angle.",
"To add, some radar is capable of penetrating the skin of an aircraft and reflect off internal structures. Stealth technologies can use geometries inside it's skin to act as traps, where radar waves bounce around inside and never escape back out toward the receiver. Another method is to use paint with iron in it to absorb still more or other frequencies. Other things to do is to produce as little electrical noise as possible - any conductor carrying a current is an antenna transmitting electromagnetic radiation. This can make you a beacon. That also means no radio. Another means is to scatter your engine exhaust to have a low thermal signature, so you don't look like a hot streak - I think this comes up more with heat seeking missiles, if those are even still used. You can also employ countermeasures. Chaff is basically strips of aluminum foil that reflect radar waves and confuse enemy radar. Or you can use a jammer that fills their receivers with EM noise, provided they don't track your jammer itself through counter-counter measures, as I alluded in the paragraph above about being an EM beacon."
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b3ijog | If governments improve cybersecurity, are they really just learning more ways to access private data? | Technology | explainlikeimfive | {
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"Yes, but the alternative is probably worse. See the government doesn't give a shit about you on an individual basis. What kind of porn you wack it too, your personal information, even your political affiliations, most governments couldn't care less so long as you aren't planning on *causing problems or are involved in criminal activity*. The threats to your data mostly come from companies and people, not the government. On top of that, the government is most likely the best choice to do something like developing new cyber-security protocols. They have the money, the resources, and the people to make it happen. They don't need to turn a profit on it and they have A LOT of stuff they need to protect that is far more important than your browser history. So I'd turn the question around and say - Who would you prefer to have develop these things? Someone who couldn't care less about stealing your data.. or someone who would really like to have that data thank you very much."
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b3lh5g | Why do almost all FM radio frequencies have an odd decimal value? For example: 100.3, 91.5, 101.1 | Technology | explainlikeimfive | {
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"So the stations don’t interfere with each other. 101.3 and 101.1 can be 2 separate stations but it would overlap with 101.2. If you have the capability you can hear this happen if the station you want is 101.1 and you tune to 101.2 you can still hear a bit of the 101.1 through the static. Why the numbers are odd and not even is arbitrary and chosen by the FCC. But they all remain odd because the FCC chose odd and they need to be .2 apart",
"The bandwidth of a FM radio signal is 200kHz or 0.2Mhz. In the US the frequency band for FM radio is 88-108Mhz so the first is 88-88.2 Mhz. The name of the channels is for the center frequency of the rang so for 88-88.2 Mhz the center is 88.1Mhz. The next channel have a center frequency 0.2Mhz higher so all channels have a odd decimal digits. & #x200B; The channels also have a channel number and 88.1 id change 201 but the are seldom used outside the FCC Commercial radio the range is 92.0 to 108 MHz & #x200B; How the spectrum is distributed depend on the country and even decimal digit are used. I can for example pick up 7 odd and 6 even decimal FM station from my desk in Sweden & #x200B; EDIT: mixed upp the start ad 80 instead of 88 for some dum reason. & #x200B;",
"Some good answers but no one has mentioned yet that FM means \"Frequency Modulation\". The signal is sent by encoding the sound in variations in the frequency. So a signal is not sent on one specific frequency, it's a range of frequencies centered on, for example, 100.3Mhz. The stations have to be a certain distance apart on the spectrum to not overlap each other, and 0.2Mhz is the separation that works for FM radio.",
"If stations are close to each other, they will interfere. The rest of my answer is specific to Melbourne, Australia (which given the frequencies you listed is probably where you are from too) The regulators here decided to make them all 0.3 more than a multiple of 0.8 This is an arbitrary choice. The 0.8 is to leave enough of a gap between that they don't interfere (lower would probably work too as long as it was at least 0.4). The 0.3 was an arbitrary decision but stops any of the stations having much 'better' numbers than the others.",
"When you transmit on a radio, the signal leaks off to both sides, and more so at higher power. (Say, putting out a signal strong enough to be picked up across the city with a crappy car antenna) & #x200B; In the US, the FCC allocates 88.0-108.0 for consumer radio. They break the radio spectrum into channels, each .2 wide. This provides 100 different channels. However, the radio station actually tries to transmit in the middle of the channel. So the person assigned the 100.2-100.4 channel tries to transmit right in the middle at 100.3, knowing they won't leak outside of their range too badly. & #x200B; In reality, the FCC takes a bunch of stuff into consideration to make sure stations don't step on each other. The higher the power the station, the further it can be picked up, but the more it bleeds outside the channel. So you have to show you're important enough to get a radio station assigned to you, and you're limited. That's why you can hear the major channels further away then your local collage radio. It's not just that the college can't afford a powerful transmitter, it's that they are limited on how powerful of a transmitter they can use. They also look at nearby cities radio stations as well, so the high-powered station from one city won't wipe out the next city's smaller station.",
"A picture is worth a thousand words: [ URL_0 ]( URL_0 ) This is a screenshot of SDR#, a software to receive all kinds of radio broadcasts.What you can see in the screenshot are multiple FM radio stations. Each peak is a station, with the highlighted one at 95.5 MHz. The highlighting around the station is 240kHz wide, so basically 0.24 MHz.If you had a station at 100.3 and 100.4 MHz, they would interfere, because they are both wider than a 100 kHz step...",
"For a real ELI5, pretend your radio tuner is a bucket, and in order to listen to a radio station you have to place that bucket on a pole with the stations name on it. If the poles are all too close together it becomes hard put the bucket on just one pole instead of 2 or 3. So we space out the poles (or radio frequencies). The 0.2 difference is enough for the bucket to miss other stations when tuning into one specific one, yet allows for us to put the poles fairly close together",
"The answer is in pieces scattered across a few different top-level comments, so to give a summary: * Stations have to be a certain distance apart on the radio spectrum, or they will interfere with one another * In the US, the FM band is split into 0.2MHz-wide chunks * These chunks are always arranged as xx.0-xx.2, xx.2-xx.4, xx.4-xx.6, etc. * The stations broadcast in the center of each 0.2MHz chunk, so the station occupying 100.0-100.2 has a center frequency of 100.1",
"FM is short for *Frequency Modulation* which means the different sounds are transmitted by slightly adjusting the frequency of the signal. If the station frequencies are too close together, they will sometimes overlap. By using odd tenths of a kHz we keep some space between stations.",
"Something that doesn't seem to get mentioned is that this applies to the US, in Europe (afaik, throughout) they have stations on the EVEN decimals. In Israel they have one both, but still give a buffer - 88, 91.3, 91.8, 93.9, 95.5, 96.6, 97.7, 99, 100, 101, 102, 103, 107 are all popular stations here (though some are regional and others are national).",
"It's an american thing. In Europe all decimal numbers are used.",
"I don’t know the technical reasons (smaller area, stronger signal, less deviation?) but in the UK, we have both even numbers and odd numbers in our FM frequencies",
"The Fourier equation states that if you broadcast on say, 88.7, there will be a harmonic at lesser power a predictable distance away, higher and lower. So maybe 101.6, and 67.whatever. the stations are carefully spaced so that this harmonic is not on top of another station.",
"FM works by changing the frequency transmitted above and below the nominal frequency. In North America, broadcast FM radio station allocations are 200 kHz wide. That's one reason why they sound better than AM, which has 10 kHz spacing -- they can carry more information. In North America, the band reserved for FM starts at 87.8 MHz. In order to go above and below the center frequency, then, the first *center* frequency has to be 87.9. All the rest follow every 200 kHz after that. Other places, the channel width may be 50 kHz or 100 kHz, and so the center frequencies that you tune to may not follow that odd numbered decimal rule. With 50 kHz spacing, it would be possible to have a station at, say, 87.825 MHz.",
"I actually know this one very very well. So FM stands for frequency modulation. That means the station has a specific frequency they can broadcast on say 105.7. Now in order for them to actually send any sound they have to change that signal somehow so your radio can tell the difference between the sound and the base signal. It does this by modifying the frequency a little. So what happens is the sound changes the base frequency from 105.7 to something roughly between 105.65 and 105.75 depending on the exact sound they want to make. You radio is set up to interpret these constantly changing differences as sound and plays it through your speaker. Now if you had a station on 105.6, 105.7, and 105.8 you would hear the edges of sound from .6 and .8 while listening to .7 so they force extra room between the stations then is ideally needed. Why is it odd numbers well the FCC says hey here are the bands you can operate with for FM radio 88-108 so if you you are changing the frequency to send your signal you can broadcast at the 88 or 108 because you will be over or under the required frequency range. So where is the first place you can really start transmitting 88.1 and if you need a .1 gap what's the next one that can transmit 88.3 and so on and so forth.",
"The fact that they are 0.2 apart is because of the way radio works. It's like lines of text: you need to have the text be a certain size so you can read it. If you make it smaller, it's harder to read (similarly, AM radio stations are narrower and it has less fidelity—550-1600 AM is like 0.55 to 1.6 FM). You can put the lines closer together but if you get too close then it's hard to read. Ideally, the lines of text are in perfectly straight lines, but radio gets wiggled by the air, and radios don't read the radio waves perfectly either (although advancements in radios made them better at following variations in the waves.) So if you imaging trying to read text that's kind of wiggly up and down on the page, and if you're an old radio, you're also shaking the paper, it would be much easier if the text was big and there were was a big gap between lines. If it were all perfectly aligned, radio could be fit as close as 0.04 apart (that's two channels, right and left, that are 0.02 wide) but that would be like reading text where each line touches the next; if you add in the wiggly printing and shaking the paper, you'd often read the wrong thing. So they give the sound 0.1 MHz width or so to make it big enough to read, and then they give a gap of 0.1 MHz between each line of text so when it's distorted, it's still readable. In other countries, radio stations are on even numbers instead. (100.2, 91.2, etc.)"
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b3m9re | How does cable work? I know streaming shows and movies downloads bytes but does cable use bytes? Are cable recorded shows just files to be played back? | Technology | explainlikeimfive | {
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"In the old days, cable contained analog signals. There are still some of those systems around. Cable now sends digital packets to the box. The box is simply a decoder. The digital packets contain bytes of digital information. Yes, the recorded shows are simply files. The files are broken down into packets. The packets are then sent to the box. Live TV also sends packets to the box."
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b3nfxe | How do computers accurately keep time? | Technology | explainlikeimfive | {
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"They have a tiny quartz crystal in them that vibrates at a constant speed (thousands of times per second). The computer counts the number of vibrations and knows a second has gone by after it reaches a certain number in its count. TL;dr piezoelectricity.",
"Some materials (usually quartz is used) have the nifty property that, when hooked up to the right kind of circuit, you can put electricity in, and get a steady stream of pulses out at a predictable, reliable rate [1]. This is called a \"crystal oscillator\". Add a digital circuit to count the pulses, and your computer can tell time. > the clock speed of the CPU You can use this to tell time. Especially in low-cost systems where accuracy isn't super important. You can adjust the electricity to change the crystal's frequency. CPU clocks, especially for powerful chips in PC's and smartphones, often do this to save power/heat when the user doesn't actually need the CPU's full computing power right now. Some additional notes: - You need an alternate power source if you want the clock to keep running during a power cut. Smartphones and laptops obviously have batteries. Desktop PC's traditionally have a very small battery for this purpose as well. - These days, many devices have connections to the Internet, the cell network, and/or GPS satellites. These kinds of connections allow devices to get information about the current date and time, so their software can correct an on-device clock that's inaccurate. For example after a full power loss including battery removal. Or just the buildup of small timing errors over weeks/months/years of operation [2]. [1] Why do they do that? It has to do with the way electricity propagates in an arrangement of atoms, it's a bunch of quantum physics. [2] There are limits to how precisely crystal oscillators keep time. Both in small differences or imperfections in the manufacturing of the crystal, and differences caused by the operating environment's temperature, humidity, and electricity supply.",
"URL_0 Because there's a clock in every computer. It is powered by a CMOS battery, The clock keeps running even when the PC is off."
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b3nypp | How TLC ssd handle byte, kB etc with 3 bit cells? | As far as I know TLC can store 3 bits of data in cell. But you can't find X, where 2\^x is dividable by 3. So pretty much by changing value of one byte, you need to rewrite part of other byte, right? But to do this it must read the other byte. Or is it operating in some kind of strange chunks like 3\*x bytes to read/write, or it have pretty normal chunk like 2\^x bytes, but 1-2 bits of last cell of chunk are unused? | Technology | explainlikeimfive | {
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"SSDs work in large blocks, like 16 & #8239;kiB which is 131 & #8239;072 bits. You can't change an individual bit or byte without rewriting the whole block. Dividing the above number of bits by 3 (rounding up) gives 43 & #8239;691 cells required to store a 16 & #8239;kiB with only 1 bit wasted. Do they do it this way? Probably not exactly but there'll be some similar scheme. Note that SSDs have all kinds of extra magic going on under the hood that you can't see. Most importantly they do error correction. Each block has a percentage of extra bits used to store \"Error Correction Codes\" (EECs) that can be used to work out the correct value of a small number of failed bits. My example block above would actually need extra cells for this purpose. SSDs also use \"wear levelling\" so what you call block, say, 123 will be written to a different physical block each time. This way, if you keep rewriting that block, it doesn't wear out one particular physical block on the SSD. It's like rotating the tyres on your car. There's also a mechanism to detect that a physical block is about to go bad and to take it out of service. SSDs have extra blocks so they can tolerate some failures."
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b3petl | How come some images can take like 10 seconds to load but videos load fine? | Technology | explainlikeimfive | {
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"The video website was ready but the image one wasn't. Whenever your phone/computer does anything to do with the Internet it's ultimately connecting to a machine at the other end that's not much more powerful. Sites like Youtube have thousands of machines ready with the most popular videos already in RAM or close to it on SSDs. If you're looking for something less popular it will take more time to retrieve.",
"Videos are generally far more compressed than images. It's not uncommon to have a 1 MB image. If video was encoded like that, it'd be 30 MB per second. Also, in general on the internet you're streaming video. It's being displayed as it's being downloaded. It's possible to make progressive JPEGs which gradually gain in quality as they load, but this seems to have went out of fashion on the modern internet."
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b3pscp | What are the main technologic advancements that make it possible to store so much more data in increasingly smaller circuits? | Technology | explainlikeimfive | {
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"Our ability to make tiny transistors which is largely driven by the machines that build them. I wouldn't say there is on specific thing that allows it, chip companies put a lot of effort into developing the machines that make the chips, and it's many advancements that come together to make what it ultimately a smaller process that can pack more stuff into a smaller space.",
"Optics. We make chips by etching patterns onto little silicon (glass-like material) plates. The smaller we can make the patterns, the more chips we can pack in for cheaper. Data *storage* is a special type of chip make of specific elements but made the same way. The way we make the patterns is by coating the plates with a waxy substance called *photoresist*. Then we take an oversized template called a *mask*, and hold it above the plate. The template is a black sheet with holes cut in it to represent where the patterns go. We use the shadow it creates on the plate to make a pattern. We shine light through the mask and it cures the photoresist — hardening the wax in certain places. Then you pour off the uncured resist and wash it so only the cited pattern remains. Finally, you use an acid to etch away all the non-covered parts of the plate and wash off the resist. Now you have a patterned plate ready to make microcircuits. So the part that makes chips smaller, is our ability to use lenses to project the shadow from the mask and shrink it down to a smaller pattern on the plate. The better the lenses we can make with less distortion, the smaller the patterns can be."
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b3q8m5 | Why does stropping a blade with leather make it sharper? | Technology | explainlikeimfive | {
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"Basically, when you use a blade, the edge gets tiny imperfections which bring the edge out of alignment. Stropping realigns the edge of the blade without removing any material like a stone would. [This]( URL_0 ) website is great for visualising what is actually happening, as it has pictures of blade edges using a scanning electron microscope so you can really see what is going on at each stage of sharpening.",
"If you look at a metal blade under strong magnification you'll see \"burrs\" that look like saw teeth. They alternate in direction. After repeated use they get out of line and mangled. Using a leather strop realigns them and makes for a smoother cut or shave. It's pretty much the same as using a whetstone for a knife or sword. & #x200B; & #x200B;",
"it does two things. & #x200B; First it will align the edge. Imagine your blade has a microscopic ding in the edge so if you look at it straight on the edge, the edge is it shaped like an \"S\" instead of an \"l\". Imagine this \"S\" shape and you apply a sanding block to the side of the \"S\" to remove the material. S < --\\[block\\] What happens? The sanding block will grind away the high spots and you have something left over that looks like this instead. ; Instead of a straight edge now you've made small serrations in the edge. To fix this you have to grind away all of the old edge until you form a new straight edge. What the strop does is instead of grinding away the material, because it is softer than the steel, it pushes on the material It works like a rolling pin where high spots in the edge get more pressure and you eventually \"push\" the material back straight without grinding away material. Now your edge is shaped like an \"l\" again and will be razor sharp again without grinding away material. & #x200B; The second use for a strop is to de-burr and hone the edge. When you sharpen a blade you rub a harder material against the steel to remove microscopic bits of metal. It's like when you rub a spot on your favorite sweater and all those little pills of material show up. The same thing is happening on the edge of the blade, little pills of steels are forming on the edge where you are sharpening it. People will put a very fine polishing compound on the strop so after sharpening on a stone the now rub it on the strop which will remove the pills of steel off the edge and the polishing compound polishes the edge to a mirror finish."
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b3qxbd | What makes dollar store headphones sound so cheap and muffled? | Technology | explainlikeimfive | {
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"Low quality components. Speakers work by having a small magnet attached to a membrane. When electricity is pushed through the wires to a coil around the magnet, the magnet pulls back on the membrane. When the current cuts off the magnet is pulled forward by the membrane. This shaking is what created the sound you hear. If the coil is poorly made, magnet offset, or too weak, membrane to stuff or soft, glued together poorly, etc the sound quality suffers",
"Their components and assembly, a little extra solder on a wire can effect quality of sound positively. Low quality speakers will always not sound so great. When the price point is that low, the key point on the product is that they work not that they work well.",
"They're made using the cheapest possible drivers, and the body is designed with little attention to acoustics. The result is that they cannot reproduce high or low frequencies, and the frequencies that they can reproduce sound muddy and bad."
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b3sleb | How did graphic designers enlarge images before computers? | I am wanting to no how did graphic designers enlarge a logo or sign they had designed before computers? were there special machines that could reproduce a design larger and what was it that did it? Thanks & #x200B; & #x200B; | Technology | explainlikeimfive | {
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"Grid enlargement, where boxes are drawn on a picture and the stuff in the boxes is drawn on bigger boxes so they match. Projector enlargement, where a really bright light shines through the picture onto a big space and a special piece of curved glass called a lens makes the picture look good enough to trace where the light shines.",
"You're looking for the pantograph / eidograph! URL_0 It's a very simple, very clever mechanical linkage that's been recorded since 1603 but probably known to humanity and used before them. There are also 3D versions used for sculpture. I really can't explain this better than with the GIF in the Wikipedia link, so I recommend you checking that out. These machines are still in use in many applications, e.g. in woodworking for tracing a pattern with a router.",
"Many ways depending on the final use (newspapers/signs etc) and whether it was colour or black and white (1) Hand drawn (with grid) (2) Enlarged with a LARGE overhead camera called a \"Repomaster\" (3) Enlarged with a pantograph / eidograph traced by hand (4) Enlarged with a Overhead projector on to a wall and traced by hand (5) 70's\\~80's Photocopier (for black & White/line images) Source I am a old Graphic Artist",
"One technique is to use an [opaque projector]( URL_0 ). You put a picture in it and it projects it onto a surface. You can adjust then adjust how big the projected picture is and use it to trace the image."
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b3sn0d | why do 220v circuits not need a neutral? | Technology | explainlikeimfive | {
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"Circuits need a return path. In a normal circuit one uses a hot leg that swings to the max positive and negative voltage and a neutral that is nominally at 0 volts. This is partly because it means you only have 1 leg that has potentially dangerous voltage on it. & #x200B; For 220, instead of using a neutral as a return path, we use another hot leg that has opposite phase. The reason for this is because we can get twice the voltage and it's easy to generate this second hot opposite phase leg with a transformer. The trade off is that now we have two hots that have potentially dangerous voltage on them. However a safety ground is still used so steps are taken to minimize the risks.",
"In the US 220VAC power is made by summing two 110V legs that are 180 degrees out of phase with each other. Due to the sine waves being out of phase, one is low while the other is high providing a path to ground through the opposite phase."
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b3t76h | Why do many modern cars have a headlight that turns off when the turn signal on that side is activated? | Technology | explainlikeimfive | {
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"Having a light on next to the turn signal makes it harder to see the blinking. This could contribute to an accident by hiding the signal."
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b3vw5y | How do barcode scanners display the correct barcode number even when the barcode is upside down? | Technology | explainlikeimfive | {
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"The first block of lines and the last block of lines are a set symbol and aren't the same so it's easy to tell if it's reading left to right or right to left.",
"The barcode is split down the middle, and each half uses a different encoding for the digits. So if the computer sees the left side codes on the right and vice versa, it knows it's upside down and reverses the binary code."
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b3xzzh | How does streaming music work? Where does the music come from? How are you able to scroll through a song that a while ago you didn't have in your phone | Technology | explainlikeimfive | {
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"Music is actually fairly \"small\" in size in the big scheme of things and for how fast most broadband connections are (including mobile connections) its a really easy thing to work with. Generally, the music would be downloaded and cached on your local device within seconds of needing it... potentially even before you need it as it may get the next song before the last song is over (ads actually do this more often though). After that, it can play the song locally even if you don't have an internet connection. If you've ever been on a subway or something where internet connection is intermittent, you can see this, the song will play, as its already downloaded and stored locally, even when you don't have constant connection, but the next song or so won't play until you get your connection back. tl;dr: The whole song is generally downloaded and stored locally very very fast, then played that way. Your connection doesn't really \"stream\" the song, as much as it just downloads it quickly and then plays it locally. Note: Streaming video is much more bandwidth and storage intensive and doesn't necessarily work this way"
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b3yc8q | How is the internet stored? Are there people who have like a million hard drives to store all of the internet so it can be accessed wirelessly? | Technology | explainlikeimfive | {
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"\"The internet\" isn't all in once place. Each site is stored by different entities, often in many different places. So there are millions of hard drives but they are also in millions of places. Also the \"so it can be accessed wirelessly\" part doesn't make any sense. Wireless access is generally just a question of a short range wireless communication to wherever wired location you are connected to. It doesn't have anything to do with the media or location where the website is hosted.",
"There are millions of people (and companies of course) with a few hard drives each that store each a little bit of the internet. That's called servers (they 'serve' you the internet). What makes the Internet comfortable are a few important servers called Domain Name Servers which basically match a written, human readable web address with a computer-readable web address. The internet is for utmost part not wireless. There are lots of cables all about the world connecting servers with each other and with cable companies boxes and from there to your wifi router. What is wireless is the connection from your (or anyone's) wifi router to your computer or phone. So just the last loose end of the internet is wireless.",
"Here is a view of some of the underwater cables that connect various countries and then from there eventually to your local provider. So access a site in Japan from the U.S. would travel over some of these and access their drives. [ URL_0 ]( URL_0 )"
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b40s1n | How do electronics with battery indicators "know" how much battery they have left? | My phone has a battery icon that shows a visual representation and a percentage of battery remaining. How does it tell how full the battery is? | Technology | explainlikeimfive | {
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"Batteries voltage changes slightly as they discharge. A simple way is just to measure this voltage (like a battery tester). Smarter batteries, like laptop batteries, have micro-controllers built into them that allow the device to communicate with the battery. Charge is measured in Coulombs and battery capacity can be measured by counting Coulombs. Amps, are just the number of Coulombs per second flowing, so smarter batteries can measure the current flowing out of a device and integrate this to get the amount of charge flowing into or out of a battery. Current is usually measured with a small resistor and a voltage meter using Ohm's law (Voltage = Current \\* resistance) Smart batteries will also report battery degradation over time etc, so a 100% charge on an old battery might only be 80% of the original capacity. & #x200B; Better ELI5: & #x200B; A Coulomb (charge) counter would act like a water meter that can measure water flowing into or out of a storage tank. By keeping track of the net water in the tank, and you know the total size of the tank, you know the percentage. & #x200B; A more simple method is to measure voltage. This would be like capping the spigot on a tank with a PSI gauge and reading how much pressure was at the bottom of the tank and therefore you can calculate the water depth and estimate the remaining capacity. & #x200B;",
"I’ll do my best to ELI5, I’m usually horrible at this. The battery has available power at full charge. We measure this in Amperage and each battery is rated or designed for a certain amperage rate. Using a tool that reads amps, we measure what the battery has and compare it to what it can have. The difference is calculated into percentage. Calculation is simple: amps/power available divided by amps/power listed on the battery and then multiplied by 100 equals battery power percentage available. Edit: missing words. Also nobody liked my ELI5. Bummer.",
"To be accurate, they don’t know. They make estimations. That’s why on old, damaged or overused batteries give wrong information.",
"Think of batteries like a pool of water, there is a max capacity (total size of pool), and drainage (pipes leaving). There's also something called self discharge, which is like water evaporating. That's when batteries just start to discharge on their own. Based on the makeup of the battery, they all have different, but measurable characteristics for capacity and self discharge. Okay, so assume you know how big your pool is when you buy it (capacity of battery in this case). How do you know how much water (energy) is left in your pool (Battery)? Well, one way is something called a coulomb counter. This is a device that can measure how much water (energy) is leaving your pool (battery). It basically counts the water (energy) leaving, and subtracts it from the total capacity - and boom you get a count of how much water (energy) is left. Some older circuits would use another measurement, called voltage to try and approximate battery life, those types of applications have been largely replace (I think) by coulomb counters. There are other methods too, as outlined here: URL_0 Hope that helped!",
"Think of it this way: say you had a battery powered machine that pushes objects. As the battery depletes, the strength with which it can push also diminishes. Now imagine if you could link the strength of the push to the amount of battery charge left, you could accurately predict how much percentage the battery has at any given point of time. This is a gross, *gross* simplification of how various current and voltage sensors work inside battery sensing circuits. Ultimately the sensing circuit is that mechanism that measures the strength of the push."
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b417bw | Is today's Qi charging the same wireless power technology that Nikola Tesla was ostracized for working on? | Technology | explainlikeimfive | {
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"Basically, but it's also the same wireless power technology that's inside every AC power adapter and electrical transformer in the world. You've got two electromagnetic coils, and alternating current in one induces a voltage in the other: the only difference with Qi is that the two coils are in separate devices. Tesla's great achievement was perfecting the use of magnetic induction to transfer power from one electric circuit to another. His great mistake later in life was believing that it could be done *at long range*, miles or more, without losing energy to the environment. He was never able to overcome the power loss problem, and there's no reason to believe his scheme would have ever worked.",
"No. Qi wireless charging is based on well-known physics and actually works. Tesla's mythical \"power everything from miles away\" isn't real and couldn't work the way Tesla thought it could."
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b45ld1 | How is data sent to one cell phone, not all cell phones connected to the same tower | When I receive a text message / data request, how does the cell tower send it directly to my phone! Does the tower just broadcast the message over its range with a specific ID tag (and other devices read but ignore the message)? My interest in this stems from privacy concerns, would it be possible for a user to see the data I am sending to a cell tower? | Technology | explainlikeimfive | {
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"> Does the tower just broadcast the message over its range with a specific ID tag Basically, yes, that's exactly what they do, that tag id is your SIM card ID > My interest in this stems from privacy concerns, would it be possible for a user to see the data I am sending to a cell tower? Every SIM card has some encryption features. The tower is capable of encrypting the data so only the person with that SIM can decrypt it. I don't think most carriers actually have that feature enabled unfortunately, but it's a capability all the phones support. Also, on CDMA networks (Verizon/Sprint 2/3G) the way the tech works, you can't actually read the data without first knowing the ID you're looking for. Basically it transmits to all phones at the same time on top of each other. Your phone uses its ID to generate a pseudorandom stream which is required to figure out who has what data. This psudorandom stream is basically encryption, but it's not secure, that is for a normal user, it looks like it's encrypted and it's very difficult to read, but the math says it's not secure, and someone can probably break it if they tried hard enough. GSM networks transmit to one phone at a time, so it's a lot easier to pull the data out.",
"It's more complicated than that, but you've got the right idea. It's not enough to just prefix each message with an ID tag and politely ask every other phone to ignore messages not meant for it: you've got to *stop* phones from eavesdropping on each other. And there's the problem of crosstalk: what if two phones try to talk at the same time? So yes, each phone has an ID tag, and that id tag is used to divide up conversation. This can be done by having the tower assign each phone a time slot in which it's allowed to transmit and receive (Bob talks with the tower for the first 10 microseconds, Jane gets the next 10 microseconds, etc), or by giving each phone a slightly different frequency on which to talk (Bob and the tower communicate at 2100 Mhz, Jane and the tower chat at 2110 Mhz, etc), or other more complicated schemes. And usually the phone and the tower will change this scheme unpredictably, varying the frequency or timeslot or whatever according to a pattern that looks random if you don't know the phone's secret ID number. The two schemes I mentioned are called TDMA (Time Domain Multiple Access) and frequency hopping. Modern LTE networks use more complicated variations on this idea that unfortunately I don't know much about. URL_1 URL_0",
"I'll try to make this as simple as possible. Your phone has a code waveform. This is unique to your phone. Signals are broadcast as another waveform. To recover the data, your phone multiplies the signals with the code waveform. The signal intended for you is the only waveform that isn't orthogonal to your code. The result is every other waveform multiplies to 0, whereas your waveform multiplies to a data signal."
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b492v7 | How do CPUs decode and run instructions ? Do they have a dedicated circuit for each instruction / opcode of their set ? | It’s unclear to me how the instruction contained in the ram is actually « parsed » and executed in the circuits | Technology | explainlikeimfive | {
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"First, an explanation of what the instructions actually are: Every component in a CPU is connected to a bus, which is a collection of wires that let the components communicate. That bus can have control bits, address bits, and data bits. A control bit tells a component what to do. So, let's say you have a component that can either add two numbers or subtract them. There will be a control bit to tell it which one to do. If it could add, subtract, multiply, and divide, you would need two control bits. The data bits are the ones that carry the actual information. So, let's say you just put a couple numbers in the adder and you want to store the result in a register (a component that can hold a single number). You tell the adder to put the result on the data bits, then you tell the register to store what it sees from the data bits. Now let's say you have a lot of registers. It can get impractical to have a special set of control bits for each and every one to tell them what to do, so instead you have address bits. The address bits just carry the number of the register you want to control. That way, if you had 32 registers, you could differentiate between them with only 5 bits rather than 32. An instruction is a series of actions called micro-ops, and each micro-op is just a certain state for the control and address bits. So, if you have an instruction that adds the numbers from registers 1 and 2 and stores it in register 3, the micro-ops could be * tell register 1 to put its number on the bus and tell the adder to add the number from the bus. * tell register 2 to put its number on the bus and tell the adder to add the number from the bus. * tell the adder to put its result on the bus and tell register 3 to store the number from the bus. Notice how the micro-op can tell one component to send and another component to receive at the same time. And also note that the bus is all just 1's and 0's, meaning its entire state is just a number. So, if your bus is laid out as [adder control bit][read address][write address], the adder is at address 4, and you’re adding the numbers in registers 1 and 2, the instruction above would be * [0: add][001: register 1][100: adder] = 0001100 * [0: add][010: register 2][100: adder] = 0010100 * [0: add][100: adder][011: register 3] = 0100011 Notice that the data bits aren’t in there: The data is not part of the micro-op, only the control and address bits are. And those numbers are what micro-ops are stored as. Now, as for how those numbers are stored and used, there are two main ways: Hard-wired and microcode. Hard-wired is pretty straightforward. For each instruction, you have a series of registers that permanently store each micro-op. When the CPU runs a program, it gets an opcode (a number that indicates which instruction to execute, opcodes make up the actual “machine code” of the program), turns on the registers for that instruction, and puts the number from each register on the bus one after another. This is called the fetch-decode-execute cycle, and it happens for every single instruction the CPU gets. Microcode is what most modern CPUs use. Instead of each instruction having its own set of registers that are turned on and off depending on which instruction is being executed, all the micro-ops are stored in a block of ROM (Read Only Memory). When the CPU gets an opcode, it loads the micro-ops from the ROM into a special set of registers, *then* it goes through them one-by-one like before. Microcode is good for very large instruction sets (x86, the set used by Intel and AMD in desktop CPUs, has more than 3,000 instructions) because you don’t need to design a special circuit for each and every instruction, you just store them all together in one place and grab the ones you need when you need them. It also lets you change the instruction set after building the CPU, like those microcode updates Intel sent out after the Spectre and Meltdown vulnerabilities went public. The drawback of microcode is that it’s slower, since it takes time to load the instruction from the ROM. Modern CPUs will start loading the next instruction before the current one is done, and they use a variety of methods to try and predict what instructions they’ll have to load next. But yeah, that’s the basics of how a CPU works on the component level. There are actually just a few components involved in doing the actual computation, like adders and registers, and most of the billions and billions of transistors that get crammed onto the chip are for memory, like cache and the micro-op ROM. *EDIT: Cleared up wording and improved the example adding instruction.*",
"> Do they have a dedicated circuit for each instruction / opcode of their set ? Basically, yes. The CPU has multiple circuits dedicated to each specific instruction or set of related instructions. Each of these circuits basically outputs a bit which denotes whether the appropriate component is active, and maybe other bits determining what type of operation it should perform, and where it should take its input from."
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b4agjq | What exactly happens when a country decides to block a website, f.ex. LiveLeak in Australia right now? | Technology | explainlikeimfive | {
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"The government tells the companies that distribute high-tier Internet data \"block LiveLeak\". Those companies change their routing tables, to make that site inaccessible. Of course, there are VPNs and TOR to technically solve the problem, so sane governments don't do this."
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b4cbg8 | What exactly is this copyright law right from the EU against which people and organizations are demonstrating? | Technology | explainlikeimfive | {
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"I'll put it in simple terms as it's not a subject I'm exactly an expert on. Others will doubtless explain it better afterwards. Essentially the new law proposes to improve copyright of materials online, with a view to protecting authors' rights to materials they produce on the internet. The lawmakers argue that there is an inequality between how something in printed media can be protected yet works produced online are essentially fair game for anyone to copy. So far so fair, but the way they want to solve it is, simply put, grossly ill-thought out lunacy which could potentially turn the entire way that the internet works on its head. Essentially they want a system where every content producer would charge a licence fee for other websites to use their material. It would be the responsibility of the websites themselves to then police what went on on their own domains. Without a licence, those websites would legally be in breach of copyright if they made any sort of replication of material on those other websites. This would mean that, for instance, Google would have to pay licence fees to any European news agencies in order to include parts of the text of news stories in its search results, Wikipedia would have to buy licences in order for its users to reference academic papers, quotes from news stories, or text from pretty much any other sources, etc. Theoretically, social websites (forums, social media etc) could be fined or shut down if their users posted pictures from another website, as that other website could claim copyright infringement. Also, the EU wants to insist that all major websites must have rigorous algorithms which automatically ban anything flagged as potentially breaching copyright. You thought YouTube's policies on what can get demonetised were bad before? Imagine if YouTube decided that they weren't being strict enough on their users instead... The lawmakers have the belief that it will resolve itself in a semi-equitable middle ground where companies are fairly recompensed for their work but the average internet user still has enough freedom to access what they want in a way which doesn't impact them too much. What most major companies are actually saying will happen instead is that they will consider the sheer number of licences they need to buy to be uneconomical and essentially they will have to simply take severe steps to ban all forms of reference to pretty much anything which originated on any other website because it simply won't be worth risking a breach of the rules. Better to overreact and never be found guilty than to risk potentially huge fines over misunderstanding the rules. As I say, I'm sure that there are nuances I've missed and that better explanations will emerge (it's been a year or so since I last read up on the probable implications of this and I'm not sure if much has changed since then) but that's the basic gist."
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b4e2to | How does Cloudflare work? | Technology | explainlikeimfive | {
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"Cloudflare is a content distribution network (a CDN). Cloudflare works by having many copies of the website spread all over the world and giving people the IP address for the server closest to them when they visit a web site. That is the ELI5 version. Below I try to keep it simple but most five year olds would not understand all of what follows. But you probably aren't five so I will keep explaining - still trying to keep it simple though. The key to a CDN is, instead of having web servers all in one place, they have them all over the world. If you are their customer, you pay them to put copies of your web content on these servers which are spread geographically all over the earth. Also, the internet really uses only IP addresses. Why does this matter? Because a single \"website\" can be more than one IP address. It doesn't really matter which IP address gives you the web content - as long as it is the \\_right\\_ content. With a CDN, when someone looks up the IP address for a website, it doesn't give the same IP address to everyone. There are databases that map IP addresses to physical locations. If I know your IP address, I can basically guess where (down to the city/neighborhood) you are on earth. The most famous example of an IP to geo-location lookup database is the one sold by Maxmind: [ URL_0 ]( URL_0 ) Using a database like the one Maxmind sells, Cloudflare uses specialized DNS servers (they turn domain names into IP addresses). These DNS servers give you an IP address (for a web server Cloudflare controls) which is closest to you. So people in the eastern US will get your content from a web server in New York. For people on the west coast, they will get a web server in San Francisco. & #x200B; You're in Australia? Then you get an Australian web server (and long live Ozzy Man) . But all of these web servers have the exact same content on them. Everyone gets the same page but where you get that page from will depend are where you are in world. The goal being to get you the page \"the fastest\"! Now, you may think, \"Light and electricity are fast! Why does it matter how close the servers are?\" The truth is light isn't all that fast. (In a single second light can only circle the earth just over six times. Light from the sun takes eight minutes and twenty seconds to reach earth. Not exactly instantaneous now is it? ) The delay from Australia to New York may be only a fraction of a second but it isn't zero. Also, a web page normally requires multiple requests for a single page to be loaded. This causes those little delays to be multiplied. So, reducing the physical distance between the server sending the website and the person requesting it will speed things up noticeably. tl;dr - Cloudflare copies a single website (or individual files - it doesn't have to be the whole website) to many servers all over the world and then use logic to send people to the server closest to them - all because it makes pages load faster! One last thing to consider is that this only works for \"static content\", meaning things that don't change (or don't change often). Things like static HTML, images, fonts, javascript files. But even dynamic websites depend on many static files so almost any web app/site can be sped up by using a CDN (like Cloudflare)."
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b4en6m | What is the goal of all the "sexy girl" fake profiles? | Technology | explainlikeimfive | {
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"The link is most likely to a service you need to pay for that will either steal your information or just get your money. That or it's a catfish.",
"I clicked one once...it exported my friends list to some spammer and now I get spam with a from name of my friends. In general, it's all bots trying to harvest something from you.",
"There are (or used to be) dating sites that would pay you a smell amount of you got someone to subscribe. I had a friend who did those fake profiles to get guys to subscribe. He made a couple thousand bucks a year from what seemed like a lot of time to me",
"You'd be surprised at the amount of people who are willing to spend tons of money on a pretty girl just because she's pretty.",
"Here's how it works: Most guys like hot girls. Most guys don't get hot girls. If a guy thinks there's a one percent chance he can get a hot girl he'll go to stupid lengths. Hence why like every other college girl has a guy friend who'd get up at 3am to drive her across town to the airport or some banal shit he'd never do if she had a dick. There's a reason you see way more hot girls in service jobs like barkeep or waitress than anywhere else. Online if you say you're a girl getting free shit is easy. This dates back to shit like EVE online or old school MMO's where even playing a female character was guaranteed easy items. You get weird messages to but that's kind of the price you pay for free shit. Catfish accounts just apply that idea to money. If some dude thinks a months rent will get him attention there's a chance he'll eat the bullet. Especially if it's a link that'll take your data rather than you paying. Obviously this means a lot of people also want to *be* hot girls. Regardless of what 2X or AskWomen will tell you being an attractive probably white woman opens a whole lot of doors. People give you shit for free like it's normal. You get more social validation in a day than a lot of people do in their whole lives. It may be fake validation but so is a strip club and those things do a roaring trade. Because once again, being a hot girl makes money a lot easier and the guy on the other side doesn't get that. & #x200B;",
"If it's a beautiful Russian woman telling you that she needs some money for a visa or what have you... then it's a Russian man with a plan to fleece you of whatever he can get.",
"They have different hostile agendas. Blackmail - Hostile gets you to send them a naughty pic and then blackmails you. Virus droppers - Hostile has you install something, and locks your machine, forcing you to pay up. Sugar Daddy/Romance Scam - Hostile has you forward them money.",
"Bots, scammers, to infect as many computers as possible, viruses, and refer back to 3. Seriously man, it's just going to infect your device. Don't fall for it. Please.",
"That’s just it they do t have the money for these kinds of things . But I’ve personally witnessed a guy at my job who was in a real long distance relationship with a women in his home country. She was not a catfish but they saw each other maybe twice in the last year . This man was sending money every week to Ecuador, he would lose sleep on the phone with this woman and then show to work exhausted and penniless.His desperation for money grew more and more every day and he would literally find any excuse to be allowed to stay and work overtime hours or come into work on off days. When his western union account was closed because he had reached his limit of transactions he would have other employees send the money for them until their accounts were eventually closed. The only way I even learned of the situation was because he eventually asked me to send money for him, which at first I did not thinking anything of it. I work with a lot of people from foreign countries and this did not seem irregular. Then it started to become a weekly habit, every Friday he would call me even on my off days or his off days to send money for him. This man was so desperate he had reached the limit on the amount of loans he could take on 401k so he proceeded to get a false repair quote on his house for $20,000 so he could use it as proof in Human Resources to obtain a hardship withdrawal. The breaking point for me was when one these western union transactions got double charged and the second charge came from my paycheck. My wife was really pissed that me helping him has now cost me money. I was able to recover my money from western union within a few business days but the damage had been done and I told him I couldn’t anymore. I saw all that because if this man can be taken advantage of from someone he knows actually exists the same can easily translate over to someone starved of human interaction and attention.",
"I followed some account on Instagram, and months later it turned into an Indian politicians informational page with everything else deleted. Guessing some of them just build followers and sell the name.",
"Also by clicking on a link, you allow the site to send you a first party cookie, which has a much longer lifetime than a third party cookie. This means that they can track you longer and make more advertising money from you.",
"I work customer service for an adult entertainment company. The ones we see are designed to bait you into using a link to sign up for a verification of some sort for dating or hookup ID. Typically (not always) the links are designed as a man in the middle attack stealing card information and signing you up to a variety of different trials/adult entertainment services. Usually you are dealing with us so long on the phone and trying to figure out why we charged you when our service says 'free membership' (hint: we didn't bill you) , they've already made several purchases or drained your account the best they could. This isn't just fake profiles. This is random texts, emails and messages on various social media/dating sites sites. If you don't know her and she all the sudden wants to hook up? I recommend not.",
"People are less likely to fall for a Nigerian prince, even if he's hot as fuck. Hot singles in your area > Hot singles in a different continent",
"I've always either assumed computer viruses or something to do with a scam. Also some people are just weird. There's a documentary on the relationship between internet scams and blood sacrifice (no shit) in Africa. I think it's called Sakawa. They apparently invest a lot of time into romance rip-offs",
"So sometimes they take you to a porn site and there you do your thing everybody's happy. Except (happened to a close friend) when theyve gotten into your camera somegow and now have videos of you jerking (or say they do) and tell you if you dont pay theyll send the video to all your friends and family. My friend in this case just made a status about it and was like if you dont wanna see dont open it guys"
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b4f3wn | How come patented things say "patent pending" on them? | At this point, it seems like the patent is no longer pending, but in use. | Technology | explainlikeimfive | {
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"That means they have applied for a patent, but it hasn't been granted yet, so they don't have a patent number to list."
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b4g76p | How the hell do ac motors work? | Technology | explainlikeimfive | {
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"You basically have a rotating magnetic field. Your AC voltage runs through a ring made of electromagnets called a stator. The stator magnets fire in pairs almost instantly. Inside the stator, which looks like a copper donut, is where you'll have your axle (spinning part), a few other wires, and the squirrel cage, which literally looks like a hamster wheel. Since the stator creates a magnetic field that runs in a circle around the squirrel cage and axle, it pulls it into motion, which means your motor drive shaft is eternally trying to catch up to the passing wave of electromagnetism."
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b4ifdo | Why do "simple" online games like Hearthstone have such a big delay? | If complex online games like World of Warcraft can be played in Real time despite the supposedly huge amount of information that has to be communicated between the clients, I'm wondering why games like Hearthstone have any noticeable delay at all. I would imagine that the only information that needs to be transmitted is like "played card x with target y". | Technology | explainlikeimfive | {
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"TCP is to make sure all packages of data arrive to destination. UDP just sends them fast not caring if they arrive or not. I suppose HS uses TCP to be sure that no action any player does is lost. And wow needs to go fast to maintain the \"real time\" illusion, hence that's why sometimes you may see a player do a little skip forward or backwards, that was a lost package.",
"Because it doesn't matter for the gameplay, therefore the company doesn't have to fork out for fast servers. The delay you experience is from the game servers not being as efficient as WoW servers. The company saves a ton of money and the game is playable."
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b4nbmd | How can a computer restart itself? | I am assuming a restart is the same as a shutdown and boot up. If that’s the case, how can a computer go from completely off, to turning itself back on without additional user input? | Technology | explainlikeimfive | {
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"When you shut the computer down, the operating system is shut down and the motherboard turns off afterwards. When you select restart, it shuts down the operating system but the motherboard stays on and boots the operating system again."
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b4plls | Why are eyeballs and teeth rendered separately from the rest of the head in a video game. | As can be seen in the picture below and in many other video games, why are the eyeballs and teeth rendered separately from the rest of the head? Ive always wondered why. Picture for context: URL_0 | Technology | explainlikeimfive | {
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"***TL;DR:*** *Skin stretches. Teeth don't. Eyeballs rotate. All are different actions that are a lot easier to work with if you keep them as separate pieces of an animated human character.* \\--- Let's time travel a bit to answer your question. Go back 15 years or so to when there were more low quality animated characters, like a really bad early-CGI ad showing happy kids eating some lunchpack yogourt, or a cheap CGI television show for preschooler kids, or a low quality cut-scene for a not-that-popular computer game. If you looked carefully at a character's face, you'd see that the teeth stretched when the mouth did. The teeth *actually moved*. Ick, right? Yeah, that problem needed a fix. The cause of the problem was when they animated the lips, they animated the teeth with them, and so teeth actually got a little bigger or smaller when the character smiles or pouts. So they avoid that by not locking the teeth to the lips, because the teeth are hard and non-flexible while the skin of the lips is. The teeth are one \"DO NOT STRETCH\" model, the lips and skin are another \"OKAY TO STRETCH\" model... and so now animators can change the position of the mouth area on your face - smile, frown, whistle, talk - without stretching the teeth along with the skin. Eyes are like that too, except for them it's more about rotating than stretching. The skin near the eyes doesn't rotate, but the eyeballs themselves do... and so having a separate render of the eyeball as a separate shape in the head makes animation much easier to do, because you can easily rotate it to point it at whatever you want your character to look at.",
"When animating teeth and eyes for facial animations, the teeth and eyes are tied to separate “joints” so they can be rigged to move as the animation plays. It helps with allowing facial animations that are not just flapping jaws since the lips can be made to move separately.",
"It is easier to work with them as with separated object that are in the same hierarchy as the rest of the character. Doing things like looking on something while moving the head or moving the teethes when person is speaking. Side effect is that creepy stuff if face object disappear for some reason."
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b4ufld | How do nuclear missile submarines receive orders from the president to launch a nuke while underwater? | Technology | explainlikeimfive | {
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"When deep, an ELF signal can be used to tell them to come up for further info. Extremely Low Frequency signals are very constrained, so it would take a long time to send/receive a more detailed message. But once they come up to a shallower depth, they can deploy a floating wire antenna that floats on or near the surface, and can get much higher-bandwidth signals for more details. Of course, they could also surface, but with the floating wire antenna they don't have to.",
"Some orders are given in advance - the UK nuclear subs carry written instructions from the Prime Minister on what to do if the government has been destroyed and/or both the Prime Minister and their assigned deputy is killed. These are known as \"Letters of last resort\" and writing them is the Prime Ministers first job after taking office, following a briefing on the impact of launching the weapons. As soon as the new letters are delivered the previous letters are destroyed without being opened. I don't know about the US equivalent, but there must be something in place to handle this scenario. I suspect you were more interested in how radio signals could be transmitted underwater, but I think this is also relevant and interesting. Edit: Spelling"
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b4vrd4 | How are pictures of planets so focused and not blurred, when they move at a speed of several km/s? | How do telescopes a) keep celestial bodies in the frame, b) focused and c) not blurred, when said bodies move at really high speeds (googled Pluto: ca 5km/s)? | Technology | explainlikeimfive | {
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"They're very far away. It's like looking at a distant mountain, or any object on the horizon, when you're in a car. It's far enough that it looks almost stationary. Compare it to the nearby objects that seem to zoom past, even though your speed doesn't change. Also, you often have to adjust the telescope every few mins, to account for the earth's rotation, but that can be done automatically using modern hi-tech telescopes",
"Essentially, it's the rate that the angle of view changes that matters, not the speed of the object. Whether it's far away and moving quickly or close to and moving slowly, the angular change is the same. When photographing moving objects, it is also possible to \"pan\" the camera, change the angle of view to follow the object. That technique is more often used for terrestrial photography like racing cars. But a reverse of that idea is used for terrestrial astronomy where the telescope mount moves over time to counter the rotation of the Earth.",
"Because they are far away. It's like how you can look at a plane flying at 600 kmh in the sky versus a car going at 90 from the side of the road",
"1. Distance. The planets are very far away, so they don't seem to be moving much from here. 2. Equatorial telescope mounts. These compensate for the earth's rotation, helping to keep the telescope locked onto a distant object, like a planet, and allow a long esposure without blur. Most of the movement we can see from the earth's surface is from the Earth's rotation (once a day), not the movement of Earth and the other planet around the sun (once a year - much less change in an hour or so). 3. Image stacking. Many photos of planets and other celestial objects are actually stacks of images. Many photos are taken, then special software is used to stack the images together, keeping only pixals that all of the seperate images have in common. Photoshop will do this, but there are other tools that are targeted just for Astral photography. This helps eliminate blurring from movement, fringing from the telescope optics, and other undesirable artifacts by averaging them out.",
"Ever saw a car pass by you at a high speed? You'd have to move your head a lot to keep the car in focus. Now imagine watching a car 500m away. You wouldn't have to move your head a lot to track that car, right? So it's all about distance.",
"Angular speed is what matters, not absolute speed. Angular speed is what portion of a circle something moves in a given unit of time.",
"The clearest images of planets and dwarves are not taken by telescope. We sent probes out there. From a much closer vantage point, and travelling at similar speeds, the images were able to be as clear as we needed. Closer and larger planets (Mars, Venus, and Jupiter) were able to be observed with decent detail using telescopy, but the high res images you see in textbooks are either artist renditions or probe-based.",
"I’m guessing that this question is prompted by the most recent post about photos of Pluto 25 years ago versus today? 25 years ago the photo of Pluto was just a blurry dot because it was taken from Earth or a very far away photograph. The most recent photo was taken by a satellite that passed very close to Pluto and was able to match speeds with Pluto. Even today when taking pictures of celestial bodies from Earth, the photos are not very clear. That’s why we have the Hubble and other satellites. Furthermore for far-away objects, they are moving fast but because they are far away their moment of arc is very low. Far away objects seem to travel slower because they are far away so you don’t have to swing your camera as much.",
"It is exactly like asking why our eyes can focus on car or even planes when they are going at 1000km/h speeds. It all depends on the distance between the object and you",
"Quite a good video by Curious Droid on the very topic URL_0"
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b4vrt6 | What’s the physical difference between a low end budget speaker and a high end pro one? | More specifically I’m wondering about the speaker cone itself. Is it anything to do with speaker cone materials, shape, design, testing, etc, or is the biggest difference found in the drivers? (I realise brand and to a lesser extent quality of electronics makes a difference to price.) Bonus question: is it possible to get some indication just by visually inspecting the cone? | Technology | explainlikeimfive | {
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"First, high-end and professional speakers are not the same. What you hear during concert will never work well at home. Second, speakers and speaker cones are very important, but it's just part of what makes a high-quality speaker. Budget speaker cones are made basically from paper with flimsy suspensions and tiny coils. The quality drivers are heavy, with very stiff and light cones, often made from composites and exotic materials. Generally, speakers to be high quality have to be very stiff - and usually heavy. Plastic is one of the worst materials for speakers. I don't think there is a way to judge the driver visually only, there is much more to it.",
"There is more to a high end speaker than just the speaker itself. Speaker construction can vary in a few ways. Cone materials can range from cheap materials such as paper or bamboo. Metal cones are also available with aluminum and titanium or even more exotic stuff like beryllium. Then there are plastics or composites like kevlar and carbon fiber. The costs can vary but higher doesn't always mean better. People will comment that paper cones sound the most natural and it's one of the cheapest and easiest to produce. Metal cones can be harsh. Plastic cones can be dull. Everyone has their opinions and some of them are generalizations. Don't write off a speaker just because of a cone material. Let your ears guide you. A large part of a speakers cost can actually come from the crossover (the part that separates frequencies, such as highs and lows, and directs them to the proper woofer/tweeter). Crossovers can be rather simple (containing a few components) or very complex (20 or more). Crossover components can often be had in a good/better/best where cost increases dramatically. I've seen speakers where the crossover was more than 50% of the cost. Then you factor in design and material finish. A nice piano black cabinet is much more costly than a veneered MDF cabinet. But the big take away is that cost vs enjoyment is subjective. I was not blessed with golden ears. I have trouble telling a $300 speaker from a $1000 speaker. So I can enjoy my comfortable ignorance knowing that my current setup sounds great without having to drop 10k on the ultimate best of the best speaker. I can go on and on. There's lots of resources on how to build speakers that will help you appreciate what is involved. Here's a link I saved that might get you started URL_0",
"This thread doesn’t seem to recognise that a speaker may contain multiple drivers that way not all be cones, piezo, domes and electrostatic are all things.",
"I am no expert in this, but since nobody has answered yet i will give it a try One point is the mass of the cone, a heavier cone needs more energy to be accelerated/cant accelerate as quickly as a lighter cone and therefore can not display the higher frequencies as well Also the material can be \"hard\" which shows itself in spikes where a certain frequency ist played too loud Hope anyone with more detailed knowlegde can expand on this Edit: i am sure the geometry has an influence, so the research which goes into developing has to be considered as well"
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b4w2b7 | How does P2P encryption work? | Technology | explainlikeimfive | {
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"Whenever you send a message, the message is locked (encrypted) using a key . The key is unique in the sense that you and only the intended recipient has the key to that lock. Thus, only the recipient can unlock (decrypt) the message.",
"If it's peer to peer, imagine it like this: You own a lock box. If someone wants to send you a letter, you tell them the lock box number to send it to. In fact, everyone can know your lock box number, no big deal. Someone sends a letter and now you have a message in your box. Since you're the only one with a key and the box is impossible to break, you're the only one who has access to that letter. If the key gets lost, you have to get a new lock box because there's only one key ever. The lock box is the \"public key\". It's a unique code that allows anyone to encrypt a message but only to you (since it's your personal box). The lockbox key is your \"private key.\" It's the only thing that can decrypt the message (open the lockbox). It would take someone a long long time to recreate your lockbox key, so there's no point to trying.",
"I can't tell you the exact math of it, but that wouldn't be eli5 anyway. Basically they use math problems that are one-way. By one-way it means that you can easily get a solution when you start, because you know all the parts. But, there are so many possible combinations, that it's very hard to get the original parts when all you're given is an answer. Like this: X+Y+Z=21289745127828972. There are many different combinations of X,Y, and Z that would give you the same answer. But to actually decrypt the message, you need the exact same ones that were used to create it. Keys are kind of like the X,Y, and Z in the example (but much more complicated.) There are generally two keys: public and private. A private key contains all of the information needed, usually the public key is derived from the private key. A public key only has enough information to create a math problem that can be solved using the information in the private key (encrypting the message.) But not enough information to go backwards (decrypt) the message.",
"Here’s the old school way it worked. You have a lock box that has two latches for padlocks. You put your message inside the box and lock one latch with your padlock. Nobody else can now open the box but you. You send the locked box to the recipient using a courier. The recipient can not open the box, but they can place their padlock on the other latch. Nobody else can unlock the recipients padlock other than the recipient. The recipient returns the now double locked box back to you. You remove your padlock, and send the box back to the recipient. The recipient can now remove their padlock and open the box."
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b4y4ib | how do doctors know if babies need spectacles? And if they can assess babies without them reading letters/numbers why can’t they assess others that way? | Technology | explainlikeimfive | {
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"The lens work the same way in both direction. So you you look into the eye and the retina is not sharp the image the eye see it not sharp. It is quite normal today that the first thing you do when you check you eye is to look into a machine where if you just focus on the image is project it can with good accurate automatically determine what your prescription is. The reading number part is just for fine tuning today. The machine is called a autorefractor or automated refractor . You could do the same thing manually in the past. The process take a few seconds per eye and work find in children and people with disabilities that have communication problems. & #x200B; If I am not mistaken it project a circles infrared likt the the retina of the eye and detect in a camera. You can see how they operate [in this video]( URL_0 )"
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b4ym3b | How do movies get “frozen/still” shots of an action scene with everyone perfectly still, but the camera panels around the room? | Technology | explainlikeimfive | {
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"The Matrix (1999) pioneered this filming technique. They used a line of cameras arranged in a circle around the action scene. At the \"freeze\" moment, all the cameras capture an image at once. When you play each of the camera images in the circle in sequence, it shows the same point in time but at different angles.",
"This effect, known as bullet time, was first shown in The Matrix, where it was done mostly in camera. A series of as many as 120 still cameras was setup around a chromakey volume, each pre-aimed and prefocused to catch one frame of the bullet time sequence. Then the stunt is performed in the volume, and the cameras are triggered remotely in a precisely timed manner by a computer.All the images were developed, then sequenced into a strip of film. Nowadays you can do this with DSLRs, where the files are placed into the proper sequence in a computer and rendered out into up to 5 seconds of film. URL_0",
"Cameras. Lots of cameras. Thanks /u/whosthedoginthisscen URL_0 As others have said, its a technique popularized in The Matrix as bullet time."
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b4zd6d | How can a computer program written to play chess defeat world champion? Is it only because it is fast and can compute all possible moves? If yes, can a human defeat it, given infinite time? | Technology | explainlikeimfive | {
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"Computer programs can be written to learn from experience just like humans can. And they can play many, many more games very quickly. Just like humans get better with experience, so can the program.",
"A chess computer can't calculate all possible moves. If you could calculate all move chess would be a solved problem and the result might be either white or black would always win or it would always be a draw if both player used the optimal moves. For example tic tac toe is a solved game as there is so few possible games and if both players do optimal moves the result is always a raw & #x200B; A conservative lower bound of all possible chess games is 10\\^120 so a 1 with 120 zeros after it. The higher bound of the numbers of atoms in the obsessive universe is 10\\^82 so there is at least 10\\^38 games of chess per atom in the universe & #x200B; & #x200B; Deep blur that beat Kasparov is 1997 could calculate 100million -200 million positions per second. If one game of chess is just one position and the universe is 13.772 billion yeas old is would have tested 200\\*10\\^6 \\* 13.772\\*10\\^9\\*365\\*60\\*60=3.6\\*10\\^24 games if is had been in operation since the universe was created. But you still ned to run it 2.7\\*10\\^95 times longer to rest a the lower bound of all chess games. & #x200B; Or another way if you had one deep blue computer for each atom in the observable universe it would have only tested 3\\* 10\\^62 games. So you still would need to run them all for 2\\*10\\^57 times longer then the universe have existed. There have been 1.8\\*10\\^54 seconds since the universe was created. & #x200B; So if you compare the age of the universe to a second you get a idea of how many times longer you run the same number of deep blur computers as there are atoms in the universe and they was turned on when the universe was created. & #x200B; So a chess computer is nowhere close to calculate all possible move and will never be able to do that. But it can when the number of pieces is reduced find away so it never loos or somtimes so it can fore a win in a lot of moves but that is not the same as testin all possible move in a complete game of chess. Human players do the same and there is book with rules how to play chess when there if few pices left to force win or a draw. & #x200B; By 2012 all possible gams where there is only 7 of fewer pieces left have ben calculated. There is not table for all games with 8 pieces but research is ongoing. You would need a \\~1000 TB to store them & #x200B; You gest a lot of moves and evaluate how good they are according to relative simple rules. You can get a idea of how to calculate how god a position is by looking at by looking at the result of old chess games. So is it a lot of test of positions but you used rules created by human and by looking at old games or games computer vs computer to evaluate them. & #x200B; & #x200B; & #x200B;"
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b50rrh | Why didn't firearms people other than snipers and machinegunners just paint dots on glass sights? | Technology | explainlikeimfive | {
"a_id": [
"ejae4u7"
],
"text": [
"A reflex sight isn't just a dot on glass, a dot on the glass doesn't show you where the bullet will go unless you're looking at it dead on A reflex sight uses creative lenses and mirrors to make the dot appear \"at infinity\" so it is always straight down the barrel from the lens. This means no matter what angle you look at it the dot is always where the bullet is going to go. You can see in [this gif]( URL_0 ) how looking at the sight from an angle it still shows you the true aim of the gun while a dot in the middle of the sight would lie to you if you weren't looking absolutely straight at it."
],
"score": [
10
],
"text_urls": [
[
"https://upload.wikimedia.org/wikipedia/commons/4/49/Mark_III_free_gun_reflector_sight_mk_9_variant_reflex_sight_animation.gif"
]
]
} | [
"url"
] | [
"url"
] |
|
b53vp5 | How heart rate sensor in smartphones detect user's heart beat through index finger? | I downloaded a fitness app last night and found a feature where users can measure heart beat by putting index finger on phone lense. How does it work? | Technology | explainlikeimfive | {
"a_id": [
"ejb2dl8"
],
"text": [
"Pretty sure they’re optical sensors that use a bright light to illuminate your veins and then take a sort of “picture” of how rapidly the veins are shrinking and expanding."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
b55iob | why is the sound on cell phone conversations still so bad in 2019 when compared to a hard line ? | Technology | explainlikeimfive | {
"a_id": [
"ejbfs8j"
],
"text": [
"There are better quality options available, however, it requires that every piece of equipment along the way support the higher quality protocol. That is to say, your phone has to support it, your carrier has to support it, the other guy's carrier has to support it, and his phone has to support it. Any incompatibilities, and it falls back to the older protocols. Why has there not been a bigger push? Because it's not really a huge demand--regular voice support falls into a \"good enough\" category for most people. People don't really want to pay extra for \"HD Voice\" support, and probably put it below data speeds, free Netflix, etc when comparing providers, so it's not a big priority for carriers."
],
"score": [
8
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
b55ize | how does the autofucos function work on modern cameras? | Basically what it says above. How do cameras or I guess more specifically the computers in a camera or smartphone know when the image is in focus? | Technology | explainlikeimfive | {
"a_id": [
"ejbdh40"
],
"text": [
"If you calculate the contrast it the color difference between pixels next to each other, it is highest when you are in focus. If you are out of focus it is blurred and each pixel is a lot closer to the neighbor in color. & #x200B; There are other way that it can be done but that is a common way. A harder problem is often to know what part to focus on and for the focus to follow a subject that change in distance."
],
"score": [
6
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
b55ri0 | how come when I’m on a call and it’s connected to a speaker, the other person can’t hear themselves despite their voice being the loudest thing in the room | Bonus question: why does this only happen with certain speakers and on others the other person hears an echo | Technology | explainlikeimfive | {
"a_id": [
"ejbhxo5"
],
"text": [
"Telephone devices use \"echo cancellation\" techniques to prevent people hearing themselves like this. It's hard to do well, especially in environments where the hardware is moving about. Devices listen for echoes of their outgoing signal to work out their delay and volume so they can subtract it from future incoming signals. Some devices do it better than others, and some listening environments can be more difficult to handle than others, so the results will vary. For example, in a room with many hard (reflective) surfaces, the echo from a speaker can travel directly back to the microphone, and also be bounced off the walls back to the microphone. So there can be multiple echoes, each with a different delay and volume."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
b57h98 | What’s inside CPUs? | I understand that there are silicon, micro/nano chips, resistors and transistors, but what is it that make all the ACC, ALU and CU etc work? And how they they translated to machine code to make a whole system work? | Technology | explainlikeimfive | {
"a_id": [
"ejboor1"
],
"text": [
"> but what is it that make all the ACC, ALU and CU etc work? The aforementioned transistors, resistors, etc. Binary operations are performed simply by flipping switches, and the logic comes in with how those switches are arranged. > And how they they translated to machine code to make a whole system work? [I suggest watching this video about defining the control logic in an 8-bit breadboard computer.]( URL_0 ) Basically it just comes down to how the computer is designed as to what values initiate what kinds of operations."
],
"score": [
4
],
"text_urls": [
[
"https://youtu.be/dXdoim96v5A"
]
]
} | [
"url"
] | [
"url"
] |
b57p3e | Why can my phone easily catch WiFi and mobile data, but can't catch any radio frequencies without headphones plugged in? | Technology | explainlikeimfive | {
"a_id": [
"ejbqa5f"
],
"text": [
"It has to do with the length of the antenna: The lower the frequency of the signal, the longer your antenna needs to be in order to properly pick up the signal. It still works with a shorter antenna, but the signal strength will drop of quite a bit. So an antenna that is made for receiving cellular signals (~800 MHz and more) is shorter than an antenna made for FM radio (~100 MHz), and would have a very weak signal strength trying to pick that up. So instead, they use the headphone jack as an FM radio antenna, using the cable to extend its length."
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
b5aol6 | Ad blockers are common for Computer applications, (Adblock+) Why is it uncommon to find working ad lockers for mobile phones? | Technology | explainlikeimfive | {
"a_id": [
"ejc52s7",
"ejc9hpf"
],
"text": [
"firefox on android supports plugins just like its desktop counterpart such as ublock origin. google chrome on android on the other hand does not have the same extension system as the desktop version",
"Mobile apps and operating systems in general are siloed, meaning that apps can't directly interact with each other. A good adblock on windows directly looks at all the traffic coming in and chooses what to block. It establishes itself between the server and your phone screen. On the other hand, there's no way (unless you root /jailbreak) your phone so that an app can sit in the middle of that connection, which means those ads can't be blocked. That's of course in addition to both companies banning ad blockers on their app stores because of \"safety\"."
],
"score": [
3,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
b5cso0 | How does one-way encryption for passwords work? How is it possible to convert text into a hash, but not be able to reverse engineer a hash back into text? | Trying to understand SHA-256 | Technology | explainlikeimfive | {
"a_id": [
"ejcnfkz",
"ejcnf7j"
],
"text": [
"The easiest way is to think of a non-secure hash algorithm. Take the letters, represented as 8-bit ASCII numbers, and add them up. Save the last 3 digits of the sum as the hash. In ASCII A=65, B=66, ... . If your password is ABCDEF, that gives a hash of 405. Of course AAAAAO also gives that same value. With this hash you can use arbitrarily complex passwords, and only use 3 digits to store the hash. That's not enough digits to store the hash securely, so SHA-256 uses a much bigger number. The ASCII code isn't random in it's assignment of letters, and so it doesn't really maximize the value of each bit input. Secure hashes essentially encrypt the message and hash the result†. This makes the distribution of hashes more uniform and reduces collisions. Even with keys in the real world, collisions can occur. Your house key opens somebody else's door, but you don't know who. Your password might unlock somebody else's account, but you don't know who. † This is conceptually what happens, not really the math behind how it's done. That math isn't really ELI5.",
"A simple example is if for a number like 12345 calculate the hash as the sum of the digits so 1+2+3+4+5= 15. The hash is then 15 but that no way to determine that 12345 was the input. 69, 96, 555, 5505, 23451 all have the sam sum/hash. & #x200B; It is a bad hash system but it show that it is quite easy to create a function that is impossible to go in the other direction because there is multiple input that can generate the same output. & #x200B; You can of course test all possible inputs and get what passwords with some restriction like length generate that hash value. So you might have the idea to calculate the hash of all possible password with som length or other limitations. This is called a Rainbow table and is a weakness of password hashing. A way to solve the problem is by adding salt. Slat is a random random string you add after the password when you calculate the hashed value. The salt is is stored unencrypted. You then need a rainbow table for each possible salt and if the salt is 64 bits you need 1.8\\*10\\^19 tables, that is 19 billions billions and it make it unfeasible to create and store that huge number of tables."
],
"score": [
5,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
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