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nndn4h | Why do most audio tape formats have two "sides" when each one is simply one-half of the same physical side? Wouldn't it accomplish the same sound quality and recording length, and be more convenient, to just record across the entire tape width at half the "double-sided" speed? | Technology | explainlikeimfive | {
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"Because then you couldn't listen to an album continuously. You would have to rewind at the end of the album like a VHS tape. (People put music on repeat much more often than they do movies.) Maybe also a holdover from vinyl having two sides, so it was sort-of expected."
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nnefom | why does an MRI make so many sounds and why can’t they be quieter? Are the sounds test-specific? | Technology | explainlikeimfive | {
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"The MRI machine uses a combination of a strong magnet, radio transmitter and receiver. When the sequences are performed, electric current is sent through a coiled wire - an electromagnet. The switching of the currents causes the coils to expand making loud clicking sounds. Additionally, there are multiple different sized/powered magnets that make different sounds. All of the magnetic coils are very large in size, using a large amount of electricity, which is why the sound is so loud."
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nnpboc | why web frameworks change or die overtime ? | Technology | explainlikeimfive | {
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"Web frameworks are like cleaning devices. In the past, everyone used a broom to clean. When the vacuum cleaner was invented, it sped up cleaning and made it easier. Newer web frameworks have more modern standards and are easier to code in (usually). Old frameworks die because who wants to use a broom when you could use a vacuum cleaner?"
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nnpnpj | you know how a phone battery after so many recharges and years of use starts to lose its ability to hold a charge, is it a concern for electric vehicles in the future and their ability to hold a charge? | I'm asking because I've seen posts and threads discussing EVs here and there and mentions of as power grids incorporate more renewable energy sources the grids will yet more efficient and thus so will the EVs. Said threads also mention how the idea is for these cars to last 10+ years but I was wondering what about the batteries? I know these cars have huge battery arrays and not the usual car battery for ICE's, but if EV is 10+ years old will the battery it came with still hold the same ability to retain a charge? Or will they discharge like an older phone battery does after many years of use? If so do these manufacturers account for eventually replacing the batteries on these EVs as part of maintenence every handful of years? | Technology | explainlikeimfive | {
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"All batteries degrade over time, and EVs are no exception, in fact even combustion engine cars need their battery replaced after a while However EV batteries are quite large and you typically never use the whole range of your car every single day, and since lithium batteries have their life counted in how many “full cycles” they get, this means they will last longer than your typical phone battery",
"Yes, all batteries, regardless of type or size, will degrade with time. However different types of batteries degrade in different ways and in different lengths of time. Batteries function via chemical reactions. When you recharge the battery you are reversing the chemical reaction to put it at it's original state. But it's not a perfect reversal. Each time you recharge, the battery loses a little efficiency. The battery's ability to maintain that efficiency varies by type. A phone battery is lithium ion. They are capable of going through about 500 recharge cycles, through normal use is about 3-5 years. An ICE car battery is lead-acid. For this type of battery the reaction pulls material off the cathode and deposits it on the anode. Recharging the battery transfers the material back. But in doing so, little crystals form on the cathode which reduce the surface area which material can be transferred back to, reducing the amount of charge it can hold. Over time, and cycles, those crystals build up until the battery is no longer useable. This can take between 3 and 10 years depending on the battery design and use. An electric vehicle battery currently uses lithium ion. Though they're likely going to move towards a new lithium iron phosphate battery. It's not as energy dense as lithium ion, so you'd need a bigger battery but they're much safer than lithium ion, non-toxic, can recharge very quickly and can last about 10-20 times longer."
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nnzkbu | Why does internet upload and download speeds differ? Why is one faster if it's just a different direction? | Technology | explainlikeimfive | {
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"For fiber optic there's actually no difference. But otherwise, it's because there's a physical limit to the bandwidth in the cable. Most people download way more than they actually upload, so the systems are designed around using more of that bandwidth for giving them more room to download with. Best analogy I can think of is a four lane highway going into a city during rush hour. More people are trying to get *into* the city to get to work, so the traffic managers open up 3 lanes going in and only keep the 4th lane for outbound traffic, since there are fewer people using it."
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no52k0 | What are the differences between a database, data warehouse, data store, and a data lake? What types of software are used? | Technology | explainlikeimfive | {
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"Let's say you owned a restaurant. A database would probably be used to store the transactions for the month or year. It might have things like the menu items and their prices and all the info you need for the day-to-day stuff. A data store might be a data connection that pulls together some of the database data/views along with an unstructured list of news headlines that have keywords related to your genre of food so you can do some quick analytics that might fall outside the scope of just database data. A data warehouse is basically a long-term version of your database. Instead of just containing a year of data, it contains all your database data since the beginning. You can run heavier queries on warehouses - things that take a long time to run but give you stuff like trends of how popular your chicken entree is until you switched to the new cook a year ago. A data lake has no official structure. It's a pretty new concept and sales teams are desperate to try be the group that determines the om official definition. The general idea is that you can put any and all data into the lake. You don't process any data in the lake - it is little more than a virtual hard drive.",
"Datastore: a digital place where you store data. This can be a database or even something as simple as a file. Database: a datastore with formally defined operations for creating, requesting, updating and deleting data. Databases come in a variety of flavors. Relational database: a database that not only stores data, but also stores the relations of that data. Data is generally stored in tables with rows and columns. The columns of the table generally describe the schema, or shape, of the data. The rows of the table generally represent individual records of the table. Tables can be linked or related to each other with \"foreign keys\". For example, an \"Order\" table might have a \"CustomerId\" column which is a foreign key for the \"Customer\" table, which relates the Order and Customer tables together. This gives you an incredible amount of flexibility in how you can query your data, as you can choose to join the two tables together on the foreign key and filter your data by any column from any of your joined tables. Nonrelational database: a database that avoids storing relational data. These are also known as \"NoSQL\" databases. These databases are generally much faster than relational databases, but come with the downside that querying data is much less flexible. It is still possible to relate data in a nonrelational database but it requires special consideration ahead of time to carefully design how your data will be indexed, partitioned and sorted."
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nocjq1 | why is it that adblockers kinda "expire"? | basically I got tired of adds as you do and got a ad blocker it work fine for like \~4 months then i started seeing ads again. later I downloaded brave browser turned on shields and no ads for around \~ 4 months then I started seeing ads again. so I came to the conclusion that google somehow detected that I was using a ad blocker and somehow bypassed it if this is true then how dose it work or if I have it wrong then why? | Technology | explainlikeimfive | {
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"It's a game of cat and mouse often. Ad companies find ways around ad blockers, so sometimes you will see some ads on certain websites for some time until ad blockers start catching up again. Also, you need to update your ad blocker regularly.",
"Ublock origin is currently the best adblocker around. I haven't seen an ad since I started using it. But you do have to let it update. Some adblockers will take money from groups like Google to whitelist their ads so it won't block them anymore. Ublock origin does not, ublock does.",
"1. Adblockers work off a blocklist of known ad-tech domains. They block all requests to those domains preventing ads from loading. It's trivially easy to keep this list updated, so most ad tech companies don't bother changing their domains to get around this because of all sorts of other issues it would cause them. You are seeing ads served from the publishers domain that you are on. Those cant be blocked as easily since they come from the publisher alongside the content that you want to see. 2. Brave is an ad tech company that offers lots of ad formats to buyers while blocking other sources of ads. You are seeing ads from the publisher served like i mentioned above but you are likely also served ads by Brave",
"uBlock Origin doesn't 'expire', but you need to let it update. I don't see ads anywhere, and haven't for a long time.",
"Thats an assumption. But what ad blockers essentially does is scanning the webpages you visit for potential ad content before it's rendered in you browser and hides it. So if the way ads are displayed is changed the ad blocker has to make changes too. I'm pretty sure big browsers make changes actively to make it harder for ad blockers as well as they make money from ads (think google)"
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nofqdt | How does reverse image lookup work? | Technology | explainlikeimfive | {
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"There's not a single way but the general idea is to first downscale the image to something small (like 32x32) and then use an algorithm that detects disctintive features of that image and encodes them into an even smaller value, it's like some sort of extreme compression. Comparing this encoded values is much quicker since they're much smaller than the original image. Also the search engine is continually looking for images in the web in order to keep a database of encoded images and the corresponding addresses. So when you give it an image for a reverse lookup the engine encodes the image in the same way, then looks for similar values in the database and finally obtains the images from the stored addresses.",
"There's a paper on the subject: [Fast Multiresolution Image Querying]( URL_0 ), by Charles E. Jacobs, Adam Finkelstein & David H. Salesin in the 1995 Siggraph proceedings. I implemented this from the paper to manage and sort my own image collection, and later worked on it at Google as my 20% project. I don't think any of my own work actually went into Google's reverse image search, so I can't say if this is actually how they do it. The gist of it is this: you scale the image down to a reasonable size, and then use a Haar Wavelet transform on it. This is similar to a Fourier transform, but easier to compute. The transform returns an array of values that basically represent the components of the image in the spatial frequency domain. You pick out the 40 most significant values, truncate them to save space, and essentially construct a \"signature\" of the image. The rest of the algorithm is just a fast way to match the signature to the signatures of images in your database.",
"When you type something into Google, Google doesn't really care that it was words that you typed in. It converts that into digital information, and then uses that information to search for similar information, and then it is translated back into words. With reverse image lookup, it takes that image and converts it in two digital information. Then it searches all over for the same or similar digital information, before converting that information into images again."
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nooax3 | how the fuck do cameras work? | Technology | explainlikeimfive | {
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"A camera has a very light sensitive sensor ( or in an analog case, film) thatight is allowed in very quickly. The brighter the light outside, the faster the shutter opens and then closes. If it is a digital camera, the light is recorded and then written out to a digital file on a memory card. If it is an analog or film camera, the light exposes the film . The film is then placed into a chemical bath to make a negative that can be used to make a print.",
"A tiny pinhole allows light in. This light reacts with something, in the case of digital cameras it is a image sensor chip. This chip is divided up into thousands of squares, which are the pixels. The pixels assign a value to the light it is in contact with This data can then be reconstructed into an image on a computer Cameras before digital cameras worked by exposing a substance to light. that \"burns\" the image into the substance, creating a picture. Edit: wording",
"Willard Boyle, who was working at Bell Labs in 1969, invented a device called a 'charge coupled device'. When the CCD is exposed to light the layer of circuits being exposed can record the photons hitting it as an electric charge. After this happens, a control circuit instructs the circuits that were exposed to light to hand their charges to a coupled capacitor (hence 'coupled') and the last capacitor in each array plops the charge into a current integrator. After this happens the voltages can be recorded in memory as a series of bits - the languages computers understand. If you know the size of the image sensor, the number of capacitors hit by the light, and you can record the voltages at each capacitor hit by the light, you can create a black and white image. If you want a color image, you put a bayer filter in front of the CCD and now each pixel will only pick up a specific wavelength that corresponds to blue, green, or red. If you have enough pixels you can create a color image using a process called 'demosaicing', which is complicated - but think of it as the computer taking all of the data from the pixels and combining the colors to make a continuous color image."
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noxvix | Why are NFTs making money? | Why are NFTs selling? And is this just a hype or is there really a future in unique art that only one can have an original of? | Technology | explainlikeimfive | {
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"I don’t understand how there is enough people that this concept exists. Who cares that you have an original gif or video of something? I’ve seen it too and downloaded the file to my computer for free. I think it’s mostly people who invest into the fad only for the potential to flip it to a sucker"
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noxy3p | In public-private key encryption, what stops someone from decrypting using your public key? | Since you know something was encrypted with someone's public key X, and you know the algorithm, why can't you reverse the process using the public key and read the message without using their private key? | Technology | explainlikeimfive | {
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"I multiplied two numbers together and got 34916677 as the answer. Without using any factorizing tools tell me which two numbers I multiplied together to get that result. You likely won't be able to unless you go try every number one by one until you hit the right answer. However if I give you one of the numbers you can easily find the other. While not exactly the same the private/public keypair are a bit like that. The cryptographic properties we're interested in are arranged in such a way that the two operations: encrypting and decrypting, are really the same operation that just happen to cancel each other out. You can't use the public key to undo the public key because you need to go *the other way*. If you walk ten miles west walking a further ten miles west won't get you back to where you started. In order to undo the public key either you have to have the private key, or you have to guess billions of potential combinations until you hit something that happens to undo the public key. There is not easy way to find that number if you do not already know it, it's all about as hard as just guessing randomly.",
"The fact that the process isn't symmetric. For example symmetric encryption is when you use the same key for encryption and decryption. Like a safe. You open the safe with your key, put stuff inside and then close it using the same key. Asymmetric encryption is often compared to a locked mail box. The mail box is the public key that you expose to the whole world, everybody can see it and everybody can drop mail for you in that. But once someon has dropped mail in it, neither they nor anybody else could get it back out. The only way to get the mail is for your to use your private key that only you have to open the mail box and take the mail out of it.",
"You can. But it takes a prohibitively long time. Public key cryptography relies on the fact that the discrete logarithm is a hard mathematical problem (in the sense that it takes a long time to compute). If you could, say, factor a very large number quickly, you could do it, but no one knows how to do that (or at least, no one has published a method for doing so). It's also possible that you could find another method to do it that doesn't involve factoring large numbers, but no one's figured out how to do that either. Using the best publicly-known methods, decrypting a properly encrypted message would take thousands of years of processor time. And for really secure applications, you can use even bigger numbers and make that into *millions* of years instead."
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np016a | do satellites orbit the earth or are they held stationary by gravity as the earth turns? | My husband and I are both in the Signal branch of the army but have very different understandings of how satellites move, if they move at all. Do they go around the earth with the rotation? Do they move at a higher rate of speed than the earth? How is it that when I use my compass, I can use the same azimuth to find the same satellite every time, day or night? Help me win this friendly debate! | Technology | explainlikeimfive | {
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"> Do they go around the earth with the rotation? Do they move at a higher rate of speed than the earth? Depends. The closer to the earth they are, the faster their rate of orbit is. Close to earn, the ISS for instance orbits once every 90 minutes. Further away you have things like Geosynchronous orbit which is a special distance from earth where one orbit is one day on earth. And further away, say the moon, orbits once every 30 days. The math governing orbits does not care about how fast the earth is spinning below the orbit. The fact that geosynchronous orbit exists just comes from the fact that the closer you are to earth the faster the orbit, the further you are the slower the orbit, and that this progressively goes from 90 minutes near earth to infinite time the further out you go, thus passing 24 hours as some point. If you want an intuitive understanding of orbits, there is an excellent game called Kerbal Space Program which really makes you understand what is going on. Its a bit silly but the physics there makes a lot of sense after playing it. I have no idea how your compass works, if I were to guess, it uses the fact that orbits are predictable and it has somewhere saved the orbital data for the orbit, figuring out its location whenever needed, this at least is how GPS works.",
"Satellites orbit the Earth. Gravity doesn't hold anything stationary, it pulls objects in. Satellites orbit the Earth at different speeds, depending on how far they are away from the surface: * Satellites at [Low Earth orbit]( URL_0 ) and [Medium Earth orbit]( URL_3 ) orbit the Earth fast than Earth revolves around its axis, therefore they complete one orbit in less than a day. The ISS for example orbits the Earth every 90 minutes. * Satellites at [Geosynchronous orbit]( URL_2 ) orbit the Earth at the same speed that Earth revolves around its axis, so they actually remain above one spot on Earth all the time. * Satellites at [High Earth orbit]( URL_1 ) orbit higher than geosynchronous orbit, so they orbit slower than Earth's revolution around its axis.",
"Satellites orbit their planets. The way this works (for circular orbits, which are the relevant ones here) (in Newtonian theory) is that they move around so fast that the centrifugal force (it's a real force in a rotating F.O.R. . Don't @ me) is equal to gravity, and as such they balance each other out. Because centrifugal force is proportional to the distance form the centre of the planet, this means depending on the distance from the planets centre of gravity satelites need to orbit at different speeds. In low earth orbit (~200-800km), which is where most earth observation, spy and scientific satellites are, this speed is around 7 km/s. A satellite in LEO will orbit around the entire earth once in around 70-110 min. However there is also a type of orbit called geostationary. This is an orbit where a satellite moves at such a speed that it orbits earth once in 23hours56min (siderial day), and since the earth also spins around itself once in the same time, a satellite in an equatorial GEO Orbit will always remain above the same precise point on the ground. This orbit is used for communication and TV Satelites, because it allows you to aim your Satelite dish at them, and not have to move the dish to track the satellite because it's completely stationary relative to a point on earths surface",
"Think of it this way. If you throw a ball along the rotation of the earth, it stays above it for some time, but it eventually falls to the Earth. But what if you threw it so hard that the curvature of the Earth starts to fall away just as fast? Well then you have an orbit. An object in orbit is moving sideways so fast that, even though gravity is pulling it back towards the Earth, the Earth is falling away just as fast as the object is falling towards it.",
"It depends on the satellite. Most stuff in orbit will move across the sky so fast that they are basically constantly falling towards earth and constantly missing because they moved sideways so much. There is however a sweet spot where the satellites are so far away that the speed at which they orbit the earth is exactly the same as the speed at which the earth turns. This is the geostationary orbit and satellite in such an orbit always will remain in the same place above the equator. You can point a satellite dish to a point above the equator and won't have to move it to remain connected to such a satellite. This is the type of orbit where most satellites used for communication are. The main downside of this is that they are really far away, which is bad for things were latency matters. They also don't prove as good coverage if you are far away from the equator. The starlink service that has been in the news recently uses satellites much, much closer to earth. Because they are so close they appear to be constantly moving all the time in respect tot he ground. This requires constantly switching between satellites to stay connected.",
"The orbit of a satellite has very little to do with how fast the earth is spinning. Especially for satellites smaller than something like the moon. The lower something is the faster it orbits. Low Earth Orbit is defined as taking less than 128 minutes to go around the earth. This would be true if days lasted 12 or 48 hours as it is 24 hours. The spin doesn't matter, just the mass. Satellites that are higher orbit slower. There are orbits that just so happen to have a orbital period of about 24 hours, which just so happens to be the same time the earth takes to spin. These are called geosynchronous orbits. Because of they were launched into these orbits, they come back to the same position at the same time every day. There's nothing special about them in a physics stand point. It's just that rocket scientist did the math and launched them that way precisely so you and your dad could point a dish at a point and always get access to the satellite. Now there is a precise band of geosynchronous orbits that has the same period as a day, is perfectly circular, and is also the direction the earth is spinning (IE directly over the equator). This is called a geostationary orbit, and it's where a lot of comm satellites are put. Because from the perspective of a person on the ground the thing isn't moving."
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np7hfp | How do companies that focus on space make money? | I understand that there are lots of odd inventions that we use everyday that come from places like NASA but I don't understand the point. What are we learning thats so important? | Technology | explainlikeimfive | {
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"There are companies and governments who need satellites - everything from military reconnaisance to crop monitoring, mapping, weather forecasting, scientific research, navigation, communications and so on. Those companies and most governments don’t have their own launch capability, so they have to pay someone to get their satellites up into orbit. •The rocket companies make money from launch fees. •The satellite companies pay launch fees - but make money from businesses and governments. •The businesses pay for satellites to be designed, built and launched - and make money from services that satellites allow them to offer. •The governments raise taxes to pay for the services and scientific results they produce.",
"Not sure if you're just using NASA an example, but it's not a company and doesn't have a mandate to make money. It has generated a fair bit of revenue in patents and licenses from things its had to invent to get to space, but it's not driving that on purpose. The direct answer: some of them are not making money - today. They are funded by investors to operate on the promise that they will some day before the first companies able to do things in space. You can't just up and build a rocket to the moon. There is a lot of very specific expertise and infrastructure required. The companies already doing that will be the first companies to open space hotels or mine meteors. There are a bunch of companies that can make photocopiers now. But, if you'd been an early investor in Xerox you likely would have enjoyed a long run without competition. Investors are banking on that with some current space tech companies. To add to that, some space tech companies make money by doing things that are impractical for NASA - ferrying commercial satellites to orbit, taking supplies to the ISS, taking tourists to orbit etc. The question of what we're learning is a bit more nebulous. We're learning lots, when conducting experiments you always have to try to control as many variables as possible. But the fact of being on Earth introduces it's own variables. For instance, we've learned that plants only use certain colors of light that happen to be present in sunlight, so we can grow under artificial light much more effectively. We've learned a lot about how gravity affects our bodies. We've driven the limits of computers and advanced our understanding of how flight works. A lot of the drive to smart devices has been supported by wide spread satellite availability. Etc etc. The biggest take a way is that companies don't need to make money if investors are willing to buy their future promises. So space companies that don't have practical functions now are making money by selling shares. For a great example of this read about how Amazon was built, it's only just started to turn a profit, it lost money for more than a decade but was a darling of the business and investing world.",
"You can group what we learn from our adventures into space into 2 really broad categories. 1. Solving engineering problems in space (or space adjacent) often results in stuff we can use on earth. Space presents unique problems for engineers to solve and a lot of times those unique problems and solutions turn out to be really useful for us on earth. Probably one of the biggest things is the CMOS sensor, in other words digital cameras. Another is artificial heart pumps used in surgeries. We could develop them because of the software NASA uses to simulate fuel in rocket engines. This has permeated our society, pretty much all technology you use today got advanced in some way or form by NASA and NASA-related work. 2. Basic research. This is stuff that expands our fundamental understanding of the universe, which in turn lets us create new technologies. Sometimes this doesn't turn into something useful for decades or even centuries. Remember, technology at the end of the day stands on the shoulders of giants. Humanity has known about electricity for centuries. But couldn't really use it for a lot of things for a little more than a century. Today we literally could not have modern society without it. We never know what basic science will be used for in the future."
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np9h5e | If I completely shut down a computer and not use it for months, how can it still tell the time accurately? (given that it isn't immediately connected to the internet) | Technology | explainlikeimfive | {
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"Most if no all computers have a battery backup for stuff like that. If you turn your computer on and the date and time is wrong that battery is dead.",
"A computer's motherboard has a battery, known as the CMOS battery. This battery remembers all the basic BIOS settings on a computer and keeps track of the time and date. If you remove this battery and leave it off for a while you'll notice all BIOS settings have reset and your time will also have to be re-synced.",
"You are not shutting it down completely. CP has a battery on the motherboard that is there to power the real-time clock and to keep bios setting. For a desktop, it is often a button cell battery that is easy to switch but in a laptop, it is often soldered on. Just looked at a motherboard like [one of ASUS's current models]( URL_0 ) and the battery is trivial to spot. It is the large silver-colored circular you seed in just to below the initial P in \"ProArt B550-CREATOR\" that is printed on the motherboard.",
"Inside the computer there is a battery on the motherboard. It provides the power to the current settings of a program called BIOS. BIOS is a simple program that has a handful of settings that in the end, tell the hardware in a computer to start up everything and load Windows (or other operating system).",
"They're never truly off. CMOS battery. It keeps the board alive with a tiny amount of current to store settings and keep time. If you're going to store a machine for more than a year, pull the battery. Sometimes they corrode.",
"Not all computers do this. I've tinkered with a Raspberry Pi 3, and it absolutely always needed to stay powered on or use an Internet service to know the time. The difference between computers that can keep the time and ones that can't is a \"realtime clock\" (RTC) circuit or chip. An RTC is typically powered by a little coin cell battery. On a PC, this battery is usually also used to retain some of the computer's basic hardware settings in its BIOS or UEFI."
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npd44y | why around the year 2000 we had to put "www." before each website and now we no longer need to. | I am born in 1999, I remember having to write "www." before my website in the address bar otherwise it would not work. Later in elementary school it no longer needed to be done to access the website. What happened? | Technology | explainlikeimfive | {
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"In the early days of the Internet, it wasn't so clear yet, what everyone was going to use it for. Around the end of the 90s/start of the 00s, it was starting to become pretty clear that web browsers and web pages were going to be how most people and businesses used the internet, most of the time. If you're going to run an internet domain, there are a bunch of different services you can host on it though. You can host a web page, an email server, an FTP server, a Gopher server, or countless other things. Traditionally, you would host each of these things on a separate subdomain of your main domain: URL_0 for your website, ftp. URL_2 for file transfers, URL_1 for an SMTP server, and stuff like that. And sometimes, each of those services would be hosted by a different physical server on a different IP address. Often there would be a forwarder so that if you went to URL_2 you would be bounced to URL_0 , but that was an extra step to set up. As things developed (and as the IPv4 address pool dried up), it became much more common to use virtual hosting, reverse-proxies and similar systems so all these services would appear to be hosted on a single system, which makes it simpler to just create a URL_2 domain and host all the services on that one address. Businesses were also starting to decide arpound the same time that leaving the \"www\" out of their website domain made for better branding.",
"For many sites, the www still works, but it is basically redundant. If every site needs it, then no site needs it."
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npen37 | How does a flash bang work? | Technology | explainlikeimfive | {
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"Sensory overload. Creates a very bright light to temporarily blind people, and a loud bang that gives tinnitus (ringing in the ears) and disables a person's ability to both see and hear opponents, which totally disorientates them until they're recovered.",
"As the name suggest the explosives and the design of the bomb is chosen to create a large flight of light as well as a loud bang. Human sensors are designed to work in a wide range of conditions and will therefore adjust to various levels of sensory input. The mechanisms for this is different depending on the sensors. Firstly the retina in your eyes work by constantly generating chemicals which gets broken down when light hits them which is how we sense the levels of light and actually see. If you see a bright light it will break down all the chemicals in your retina making you go blind until the cells can reproduce the chemicals and you will slowly gain back your eyesight in the darker conditions. At the same time the eye detect the bright light and closes down the pupil. But it is not able to react fast enough for a flashbang and when it reacts and closes your pupil it is too late and you end up with a tiny pupil only allowing a bit of light though to your retina for a few seconds which also makes you blind. For your ears there is two effects going on as well. Firstly the sensors in the ear consists of hairs of different lengths which will sway depending on the frequency of sound. But a flashbang does not produce any frequencies only a large single shockwave. So it is able to set all the hairs in your ears swinging at the same time. It takes a bit of time for these to settle down and actually respond to more quiet sounds around you. So you go deaf for a few seconds. But secondly some of these hairs will be permanently damaged. The effect is that these will send a constant signal to your brain. So when your hearing does return the brain gets the signal that a few single frequencies are still loud, like a whistle or something. The brain actually focuses on these high pitch constant sounds because they are the loudest and tries to make out what it is. And it takes the brain even more seconds to find out that the hairs that these nerves are connected to are actually damaged and it will eventually just ignore them for the rest of your life. First then will the brain be able to focus on the other sounds around you and start analyzing these. There may also be other neurological conditions happening. We do not have the best ability to analyze these situations in a controlled environment with equipment scanning everything that is going on. Our research into epilepsy does show that big sensory inputs to the brain can have effects throughout the brain and nervous system. But these effects are not fully understood if there are any at all or if they are just natural responses to suddenly going blind and deaf while getting stormed by armed assailants."
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npfge7 | When we download applications or software from a server, why are we often encouraged to use a mirror site, rather than the "original"? | Technology | explainlikeimfive | {
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"Let's say you owned a store that became really popular. The store only had room for 100 people in it at a time, but as your store becomes more and more popular, people start having to wait outside. You try to tweak the inside of the store and maybe you squeeze a few more people in, but the only way to expand the current store further is to buy the place next door which is REALLY expensive ($1 million dollars). If you did that, you could handle 200 people but then once you hit that limit, you are faced with the same problem and expensive costs. Plus, you have people driving all the way from other nearby cities to come to you, so their trip is lengthy just to buy from your store. You realize that for the same cost ($1 million dollars), you could set up TWO additional stores in nearby cities. So instead of one store that can handle 200 people, you end up with three stores that each serve 100 people. And since the stores are closer to some of the shoppers, it is no longer a really long trip for them. And if you ever need more stores, it is much easier, cheaper, and quicker to buy more stores instead of trying to expand the existing stores. This is the same thing with servers and mirrors. Mirrors are the additional servers that provide the same files, and can provide them at faster download speeds if there is a mirror that is closer to wherever you are. And faster downloads also means the download is FINISHED faster, so that also helps create more availability on each mirror. And on top of it all, it increases reliability because if one server has a critical failure, people can go to a mirror instead of getting mad about being unable to download the file.",
"It’s a way to load balance server load amount multiple servers. Chances are if you are being pushed to a mirror it’s because it’s over loaded. CDN’s are a better way of handling this tbh."
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npgjl6 | Why on old cartoons, did a scenery object look brighter if the characters were going to interact with it? Why would the quality differ regardless? | Technology | explainlikeimfive | {
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"They were being drawn in different layers. Old cartoons were literally drawn on clear plastic sheets like you'd get on an overhead projector. Character's movements therefore had to be drawn and redrawn for each frame. The background didn't. It would stay the same for multiple shots. These different layers would be stacked on top of each other and a picture.would be taken. Then, the character pictures would be swapped out for the next frame. Maybe the background would be moved a bit too. If an object was going to move, it would have to be on a separate layer from the background.",
"The short answer is that background plates were often rendered with different media than the more limited choices available for ink and paint that made up the animation cels. If the director wanted a watercolor look to their scenery, they could get that, but then the animated elements would stand out from their surroundings because the ink and paint you could use on celluloid (cel) was very bright and defined, and therefore created a harsh contrast with the backgrounds that allowed subtle gradations in color.",
"Often the background is painted with water colors. Then characters or anything that has to move is painted with acrylic paint on clear plastic sheets called cells. The Ink and Paint department would try their best to match the colors. Matching the 2 different types of paint colors is difficult.",
"They weren't just brighter. They were outlined and simpler like the characters. That's because the other objects were in the background layer which, unlike everything else, which was penciled and colored in, it was painted."
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npmx3j | How does software / firmware physically 'interact' with hardware. | I understand, at least at a superficial level, that integrated circuits contain many many transistors, which act as 'switches' for current flow. By applying a current to the transistor 'base' (or not applying a current), the current flow from collector to emitter can be used together with others for AND, OR, NOR etc, which in turn can be built up to be used for many complex processes. What I don't understand is how the 'program' (software or firmware) can apply this switching signal in the first place. Somewhere there is a physical change- i.e. current is allowed to flow to the 'base' contact on the transistor. How does this happen without a physical switch? What mechanism is in place to allow current to start and stop without a physical interaction? I would love to know in the context of a simple microcontroller, something like an arduino, rather than the complexities of PC. | Technology | explainlikeimfive | {
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"The program is stored as a physical difference. From the moment the software is written to a computer (or read from a disk) it is already a physical voltage in the computer. All that's left is for it to move around via those transistors.",
"Probably easiest to go back to the 8 bit computers of yore... If you are happy with the idea behind how a CPU works. It has a fixed number of instructions each denoted by a particular sequence of numbers. It reads the next instruction from memory. The location it reads from is typically controlled by a Program Counter register. Instructions will tell the CPU to do one of the following: 1. Read from memory to a register 2. Write to memory from a register 3. Manipulate a register 4. Jump to a location (ie: change the value of the Program Counter) The interaction with hardware was achieved in the early days by simply making hardware behave like memory. So writing to location F000 (in hex) didn't write to physical memory but wrote to the Digital to Analogue converter connected to the speaker circuit. Knowing which circuit to activate is done by monitoring the address lines (aka address bus) of the CPU and the R/W (read/write) state. Once the address lines are setup there is a small amount of time during which you can get or set the data. Knowing what data to read or write is achieved by getting or setting the voltages on the data lines. (Aka: data bus) Firmware came about as an abstraction layer. It allowed software to be written that didn't need to know about the physical location of the speaker circuit. Instead it can make a simple call to a firmware function (which is a set of mini programs held in read only memory) Having a firmware means the physical hardware can change without breaking the software that calls it. Which is handy..."
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npqcbe | how does a computer ‘read’ a disk? What exactly is on the shiny side of the disk that is able to be read and over-written by the computer and it’s laser and then play a video game? | Technology | explainlikeimfive | {
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"So Hard Drives, floppies, and most tapes are read magneticly. Think the disk cut like a pizza and then ringed. Each section is magnetically charged. It can be read as a 1 or 0. Lost of 1s and 0s can be converted to data. Disks like CDs and DVDs are a bit different. Think of a spiral groove like on a record. In the spiral there's pits and lands. Basically it looks like Morse code - - - . . - it is also read as 1s and 0s."
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npsi0e | How is text to speech generated? | Technology | explainlikeimfive | {
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"The first thing you do is make a voice bank. In most cases this means recording someone say a whole bunch of words and sounds in different ways. Then you have to make a program that can look at text and pick the right sounds from that voice bank. Often this will just be a one to one word match, but for words that weren't put into the voice bank, the program needs to be able to break that word up into its individual sounds (phonemes) and then fetch those sounds from the voice bank and string them together to make them sound like one word. This is what's happening when a satnav mispronounces a place name - the program has misunderstood the sounds of the text it's reading. Because this is quite unreliable, the voice banks that sound most human are the ones with the biggest catalogues of words, generally speaking, so that they can avoid having to construct words from phonemes as much as possible. Many modern voice banks also figure out the intonation of the sentence and pick and morph the words to match that intonation instead of getting a flat, robotic tone."
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npt7tu | Why do computers/art programs still have problems with sorting colours, even when they have explicit options for it? | Technology | explainlikeimfive | {
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"For a computer, a color is a number. Traditionally they are stored as their Red-Green-Blue values, let's say \"0\" meaning none of that color and \"255\" meaning as much as possible from this color. If you now tell the computer to sort by color, it will simply sort by number. Since red is the first part, it will first have all the colors with no red in them, and at the very end those colors with a lot of red in them. That means that in between \"no red, a little green, fully blue\" and \"no red, quite some green, fully blue\" there will be other colors like \"no red, a little more green, no blue at all\". This makes sense for the computer, but looks awful to the human eye. The question you need to ask is: How do you sort colors objectively?",
"This is a very complex subject. Color, as perceived by most humans, is a mixture of four types of excitations, one for each of Red, Green, Blue, and non-colored brightness. Of course, these regions [overlap]( URL_0 ) and that complicates matters further, but let's ignore that. The thing to realize is that \"color\" (as seen by humans) is 4 dimensional (note, this can vary between 1 and 5). Four dimensional things are hard to imagine, so let's ignore the rods, leaving a 3D color space, which we can model as a large cube made of regular dice. How do you draw a 1D line through that 3D cube in a way that \"seems right\" to a person's subjective experience of which colors are close to each other? No matter how you draw the path through the dice (and I encourage you to play around with various ways to do this), there will always be dice (colors) that are nearby each other in the larger cube, but yet far apart on the 1D line (sorting). In short, there is no natural sorting of colors, so all sortings have problems of one sort or another. We can even throw out computers, people have the same issues. Imagine being in an art class and being asked to design a color wheel. Now you're projecting the 3D color space onto a 2D canvas, how do you do that? One common solution is to make a circle with the colors in rainbow order. But where on this wheel is brown? Brown isn't there, because the rainbow order circle does the 3D to 2D projection by eliminating brightness information and brown is secretly just a different name for dark orange (seriously). By a similar token, almost none of the colors of a sunset show up on the wheel, if you had a paint of one of those colors, where would you put it? Somewhere between yellow-orange and blue-purple? Problem is, those colors aren't next to each other on the wheel. Okay, so the wheel is bad, but so are all other projections, because fundamentally the projection from higher to lower dimensions loses information in a way that directly experiencing the colors does not."
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nptuq2 | Why is upload usually much slower than download? | Technology | explainlikeimfive | {
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"In simplest terms it's just a commercial consideration; most people are consumers of data hence their bandwidth is down and rarely up. It would be wasting limited bandwidth guaranteeing a fast upload speed that's rarely, if ever, used. Those who need a lot of upload capacity are, largely, businesses or content creators of some kind. Therefore they'll be offered different rates to consumers that unlock faster uploads (and will have the capacity, and desire, to pay for it). In simple terms it's a 'fake' throttle but a reasonable one I guess.",
"The signals can only physically transport so much data, and *most* people tend to download way more than they upload. So they need faster download speeds and the companies have structured their systems around that. With fiber optic it is a moot point, the speeds are the same just because of how that technology works."
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npvazy | How does the internet work in practical terms? On what does it rely physically? | Technology | explainlikeimfive | {
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"Physical computers. When you visit a website, it's essentially a set of files and scripts that you download and run locally on your computer. Those files are stored somewhere in the world on a server. A server is basically a big storage computer. Ie. it's not used by a person for personal computer stuff, it just sits in a big room full of other servers holding files. When you type in a web address into your browser, it sends that address to a DNS server. A DNS server is kind of like a phonebook for the internet. You ask the DNS server \"send me [www. URL_1 ](https://www. URL_1 )\" and the DNS server tells your browser the address of a server that holds the files for [ URL_1 ]( URL_0 ). Now that your browser knows where those files are, it gets in touch with the webserver that holds those files and downloads those files to show you in the form of a website. In the early days that was all a website was really. A bunch of text and pictures plus instructions for how to showcase these to you. Modern websites are a lot more interactive. Some websites don't just send you files and text but also scripts that run locally on your computer. Some websites run software on those servers. That way you can send a request for a website, but you can also send a request for the server to do something for you. Like, find a book on amazon. As you can imagine, it takes an enormous amount of servers to store all of the content on the internet. All over the world, there are cavernous halls filled with servers. Many websites are stored in several places all over the world so that DNS server, that phonebook, can direct you to the nearest one for the fastest server. But when you get right down to it, the internet is just a bunch of computers full of files and scripts with a clever system for making it possible for you to retrieve those files from all over the world just by asking for them using your phone or laptop.",
"The Internet relies on data sharing agreements between commercial telecommunication providers, and government providers in some countries. You subscribe to a particular Internet Service Provider (ISP), and your computer sends data to them. They share it with the other ISPs to allow it to travel to the ISP serving the site you want to visit, who provides it to the servers running the site. Returned information follows a similar path back to you.",
"The internet is a giant “network of networks”. So, what is network and how can you build your own internet? Imagine you want to connect your computer to another one. In its most basic form, you just put a cable between them and that’s it. Congratulations, you’ve got a network!. Add some networking code and both computers can now send and receive data from each other. Soon you realize that it would be cool to have all of the computers in your house connected. You could connect every computer to every computer, but the amount of cables would grow exponentially by each new computer on the network (since each computer would have to be connected to every other computer). You realize that this would be much better if every computer were connected to a single device that handles the data routing between each computer. Lucky for you, somebody has already created such device. It’s called a “router”. Even more, since having cables all around is annoying, this router comes with WiFi, which works the same way as cables but uses invisible radio signals instead. Now you have your whole house connected together! But what would happen if you decide to go even more ambitious and connect your Router to your neighbor’s router? Well my friend, now you’ve got a “network of networks”. The computers on your network can send and receive data from your neighbor’s computers. Now let’s take this further, shall we?. Let’s put a bigger router on the street and connect the routers of each house to it. And why not make a giant router for the whole city and connect each street’s router to it? You can now see how the “network of networks” starts to grow. Add a giant Router per City, State, Country, Continent and connect them together and you’ve got the biggest network of all: the internet. With this approach, you can now send and receive data from every computer in the world. To facilitate this process, you probably have an ISP (Internet Service Provider) that gave you a router and handles the connection between your house and a more general network. Interestingly, there are ISPs of ISPs. So there are consumer oriented company’s that handle this kind of domestic usage for you, and then there are other company’s that handle connections between country’s in the other end of the spectrum. The wider the scope of each network, the more data it has to handle. So you are gonna need way bigger cables and routers for handling the connection of a whole City in comparison to the ones in your house. Further more, you can make multiples routes between two networks in case one of them stops working (for example if a cable breaks). Bonus: When you visit a website (which is just one usage of the Internet, as a more general thing), your computer goes network after network until it reaches the computer where the website is located. The website itself is just some files, code and data in another computer. How big sites like Google, Netflix, Facebook etc, handle huge amounts of data and deliver them super fast to your house anywhere in the world is a whole engineering problem to solve, but the general idea remains the same. Bonus 2: In case you were wondering how mobile networks like 4G work, they function very similar in essence as a giant WiFi."
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npybls | When we send messages and posts in places like a Discord server, where are they stored? Will we ever run out of space? | Technology | explainlikeimfive | {
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"They are stored on the server of whichever messaging platform you're using. Discord, Facebook, and any other service has server space where they store everything you send. To answer the second question, probably not. They will just buy or build more servers."
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nq2bz0 | How are phone numbers created ad why do they need a country code? and wont we run out of phone numbers eventually? what happens then? | title says it all. I've been starting to wonder about how phone numbers work. Also could i create my own number with it's own country code? | Technology | explainlikeimfive | {
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"In order to receive phone calls all the phone systems in the world needs to configure their systems to route calls to your phone number in the right direction. It is too much to expect to have all the phone systems in the world add all phone numbers in the world to their configuration. So instead we have a system where the phone systems only need to look at the first digits to know roughly in which direction it will need to route the call. The country codes are defined by the International Telecommunications Union. The country code +1 is assigned to the Federal Communications Commission but they work with similar agencies in neighboring countries. Other countries have longer country codes. The numbers are further divided into several area codes. There have actually been some cases of countries running out of phone numbers. Or more commonly they make a system of phone numbers which does not work as the population changes. The thing is that there is no limit to how long a phone number can be. Some systems have technical issues with long numbers but there are phone numbers in use today that are over 15 digits long. And the FCC have reserved several area code for various changes to the current system.",
"a phone number is just a string of digits, from 0-9 inclusive (meaning it includes 0; there are 10 digits here). Phones in the US use 7 digits, without the area code. That means there's around 10 million possible phone numbers. Once you include area codes, that maximum number of phone numbers increases to 10 billion, because there's 10 digits. This means the US has more total phone numbers than there are people alive on the earth, on a technical level. Outside of that, things get a bit awkward when you consider global phone numbers. Because there's some countries like India that can have 13 digit phone numbers; and then some small island nations that barely need more than 4 digit phone numbers, just because of differences of population & size. You most likely couldn't create your own number with it's own country code, by yourself, without a lot of effort for it to get recognized by the global telecommunication companies - and even if you did, they'd probably charge some massive fees that wouldn't be respectably \"possible\" for a single person (nor would it be \"worthit\" if it were for just a single number, on their end)."
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nqc0mm | How are solid state batteries different from current lithium batteries, and why are they better? | Technology | explainlikeimfive | {
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"text": [
"Ssbs do not use a toxic liquid electrolyte. Without that, dendrites can't form and kill your battery over time, or short it and make it explode. They are safer, can last a lot longer, and can be recharged many more times than normal batteries.",
"Hypothetically, a solid state battery can be safer and lighter (or rather, more energy per weight) than a lithium ion battery. As far as I know such a battery hasn't been perfected yet. Energy capacity for the most advanced solid state batteries is still very low, and costs are very high. It's more of a \"maybe in the future\" thing and still very much in the development phase where lots of really cool sounding ideas end up dying in the crucible of real world application."
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nqkllz | Why do text-to-speech apps for nonverbal people cost hundreds of dollars? | Technology | explainlikeimfive | {
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"text": [
"Because that’s what the seller wants to price them at. The market is small, and they might be interested in recouping the investment quickly, there might be no competitors, or hard to get, substitutes are basically not having an app, etc etc etc."
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nqoqyf | why nuclear bomb tests don’t cause nuclear winters and other effects from nuclear bombs? | Technology | explainlikeimfive | {
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"They do cause all the same effects as a nuclear weapon dropped in war. The only difference is one of numbers. It is anticipated that if nuclear war ever occured that the involved nations will launch all of their available weapons. In the case of the U.S., Russian, and China this total will be in the thousands. There have been quite a few nuclear tests performed over the last 80 years, but they were spread out over time and still don't approach anywhere near that total.",
"The idea of \"nuclear winter\" was based on what might happen after an exchange of thousands of weapons aimed at major cities that resulted in massive uncontrolled fires that burned for weeks or months. Even in that worst case scenario it's debatable whether the climate impacts would be so drastic.",
"The number. This possible doomsday scenario was is if one superpower launches all its nukes to wipe the other. Once that was initiated, the other would see it coming, but not be able to stop it. The only response would be to launch thier thousands of nukes back. The majority of two vast continents getting nuked within the span of a day would completely destroy the US and Russia and have untold ecological problems for the rest of the world.",
"We haven't done nuclear bomb tests in like 30+ years, and even then during the final years of nuclear testing they were all done underground. Besides that, the idea of a nuclear winter is just *one* hypothesis about what would happen as a result of a large-scale, widespread nuclear war. And it requires the explosion of *many, many* nuclear devices at one time to create the amount of dust and dirt and debris that would cause such a nuclear winter (though there's debate about whether that would happen). Individual nuclear devices are not enough to cause a nuclear winter. Besides that, nuclear testing *has* caused serious issues, such as long-term radioactive contamination of certain areas (look at the testing grounds in Kazakhstan), electromagnetic pulse effects that destroyed satellites in space, and accidental radioactive spread over civilian populations at some points. A lot of these mishaps and consequences shaped nuclear testing agreements and protocols, so that we *wouldn't* repeat those mistakes again.",
"They have plenty of effects, you should look them up. Nuclear winter requires a large number of bombs detonating simultaneously, around the world, kicking up enough smoke/ash/debris to block the suns radiation and lower the global temperature.",
"The “Nuclear Winter” scenario assumes that the bombs will be used on cities, burning vast numbers of buildings and starting Hiroshima-esque firestorms all around the world. The smoke and soot from global destruction clouds out the sun and lowers global temperatures. Isolated tests in the middle of nowhere don’t have that effect. After the 1960s, the world powers conducted most of their nuclear testing underground to better contain fallout and maintain secrecy.",
"Nuclear winters require a massive amount of dust to be carried up into the upper atmosphere and reduce the amount of sunlight reaching the ground. A single nuclear weapon may carry some dust into the upper atmosphere, but not enough to create a nuclear winter. In addition most new tests are carried out underground so no dust is carried up into the atmosphere.",
"They do cause all the effects of Nuclear explosions otherwise they are pretty poor tests, just not the winter. That's why they are done in the middle of deserts, or underground, or ion uninhabited stops in the Pacific. The winter is caused when enough bombs go off that so much dust is thrown into the atmosphere, the sun is effectively blocked out, thus the temperature plummets globally.",
"Nuclear winter would have been the result of thousands of bombs which would in turn cause fires and produce smokes that cover sunlight around the planet. Nuclear tests were either done underground or on deserts where there's nothing to burn. Depending on what element the bombs were using the radiation can stay there for minutes or for years, some places that were used do still have faint traces of radiation from the 60s but it's a dessert so nobody lives there."
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nqr3ii | why do gaming laptops perform significantly worse on games when running on battery as opposed to it being charged? | Technology | explainlikeimfive | {
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"Running a lot of the components, such as the GPU, takes lots of power. The computer will try to minimize battery drain when unplugged, and thus won't fully utilize the hardware. I'm sure you can change this behavior in your power settings. However, your battery will probably drain *very* fast.",
"A battery has a maximum draw capability, they generally are not capable of providing enough overall power to run all components at maximum capacity when running purely from battery. Pulling too much power from the battery too quickly can damage it just like charging it too quickly can. As others have stated, the power plan on a laptop generally works to run even lower than maximum draw while trying to find a good balance of runtime and performance, but this can be changed to the detriment of one of those two criteria."
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nqtsze | Why does the magnetic strip on cards need to be swiped quickly? Why won't it read if inserted slowly? | Technology | explainlikeimfive | {
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"The reader keys off changes in the magnetic field of the strip. You need to move fast enough that the change happens quickly enough for the reader to recognize it as a change. If you go too slow, the change is so gradual that the reader doesn’t see the “edges”. The changing field is what activates the electronics in the read head. Imagine a bar code blown up to thousands of times normal size…you could be standing on a bar but it would just look like a giant black expanse and you wouldn’t realize you were standing on a bar code. Swiping slowly makes the stripe “bigger” from the reader’s point of view.",
"It's mostly because when you move faster you move more evenly. If you go slowly you actually introduce a lot of variation into your movement. When you swipe quicker it's far more likely that it's an even and consistent movement. The reader can deal with huge variations in the \"width\" of data, but it has to be consistent throughout the swipe.",
"The magnetic strip reader is sensing the changes in magnetic field as the card moves past it, and is trying to interpret that as a series of values. Because the card will be moving at various different speeds it actually needs to consider multiple possibilities from what it senses; if it senses a magnetic orientation of north for a period of time that might mean one value is north if the card is moving quickly, or two places are north if it is moving slowly, etc. The greater a period of time it needs to consider the larger the number of different speeds of swipe are possible. The card reader also at some point needs to come to a conclusion about what card was swiped. It can't do this until the maximum period a card can be swiped has elapsed, so letting someone take 10 seconds to slowly swipe a card would not only mean the reader needs to consider every possibility from the extremely slow to the fastest reasonable swipe, it also would take 10 seconds to finish reading a card swiped at a normal speed. It has no way of knowing if the user has finished!"
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nqvdqz | Why does the washing machine take twice as long with hot water then cold? | Technology | explainlikeimfive | {
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"You could have a clogged screen on the inlet of your hot water line to your washing machine. It's an easy thing to check and fix. Turn off the water feed and disconnect the hose at the washer. Look inside the washer inlet for a screen just inside it. Gently clean the screen off with some spray cleaner and a coton swab. Reassemble the hose and washer and turn the water back on. Source; I've had to do this a couple of times on my machine over the years. It greatly improves the water flow.",
"Because it needs to heat the water before washing and cool it before rinsing (machine depending). Heating water takes energy and the more of it there is, the longer it takes. So that's why it takes longer in general. Some will add a bit of cool water near the end of the cycle so that by the time everything is rinsed and spun, it's all easy peasy."
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nqw6ez | Why are IPv4/IPv6/NetBIOS addresses and names needed in networking when every device has a unique MAC address? | Technology | explainlikeimfive | {
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"The MAC address does not give any description of where the device is located or how you can send a packet to it. If we were all just using MAC addresses for all traffic then every router at every ISP needs a list of all the devices in the world and where to find them. This would be extremely difficult to maintain. The current system of addresses is based on the geographical and logical location in the network. A router only needs to look at the first bits of an address in order to know where it should send the package next. You can compare it to a post address. We technically do not need to write the street name, post code and country on every letter we send in the mail since most people have a unique name. However it is very helpful to the post office to know if the receiver is living on the other side of the city or in the next country. The way we have it now they can only look at the post code and sort it into rough boxes that can be sent in different directions. A post office in New York City does not need to know your street address in Los Angles and only need to know what post code range is used for the west coast cities.",
"MACs only work on a lan level, ARP tables arent sent across the network. Routing subnets is easier than mac tables, also for security reasons, its easier to assign/change/reassign IPs than unchanging MAC addresses. The list of reasons why IPs are needed is longer than the character limit for a comment.",
"A MAC address is a thing called an unroutable address. An IP address is routeable. It's not at all clear from just looking at the addresses but IP addresses actually have a thing built-in that allows them to be logically divided into smaller parts called subnets. This allows IP addresses to be logically subdivided so it's easier to find a device by it's IP address. MAC addresses don't have this, they are just a unique identifier for a device. To make this easier to understand imagine you want to visit somebody. Their address is 3746729924. Their neighbors address is 27319, the house across the street is 9887372838276618. The address numbers are given out essentially at random so there's no way to find out where these addresses is located based on just the number. You would have to wander around the country until you happen across it. This is how a MAC address works. Now imagine you are given the address of 300 Kitty Street, Dog Town, Florida. You don't know where this is located but because you know how addresses are formated you can more easily find it. This is how an IP address works.",
"Let's say a MAC address is the name/surname of the computer. (And work only on LAN) Imagine how complex or inefficient would it be if a computer needed to know each MAC adress in the world.",
"MAC is like your DNA, it uniquely identifies you. But good luck trying to send someone a letter addressed with their DNA. IP address is like your street address. It pin points where you are right now. The post office (the network) knows how to get mail to your house. When you move you change your address, just like your phone connecting to free Wifi at Starbucks."
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nqy9us | how does “connected, but no internet” work on computers and other technology?? | for context, this just happened to my computer, and i’ve always wondered how it was possible for something to be connected… but not connected | Technology | explainlikeimfive | {
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"It's connected to the local router (like paired, similar to a Bluetooth connection), but the router isn't receiving any information from outside",
"It's a bit like roads. You can have a few dirt paths that connect your main house with your shed and your garden plot, but those paths don't directly connect to the main road. You have to go through your house to get to the main road. If the path from your house to the main road is blocked, then you can go anywhere on your property (your network, all the devices on your WiFi or ethernet) but you can't go anywhere off the property (the internet).",
"Okay, like you're 5. Imagine being stuck in a room with a lot of other people, but no one has cell service. You can talk to all the other people in the room as much as you want, but no way to talk to the outside world. In this scenario you are the computer. The other people in the room are other devices on your local network. The cell phones are the internet."
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nr4hpu | Why do computer screen images look weird when pressed on but not just in text? | If you take a picture of a computer screen, and send it to someone, without pressing on the image it’ll look completely fine, but when they press on the image it shows a grid type of texture on top of the image. Why? | Technology | explainlikeimfive | {
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"I'm guessing by \"pressed on\", you mean zoomed in to full size? The grid texture you're seeing is what's called a Moire pattern. Your camera is actually high enough resolution to be able to see in between each of the pixels of your screen (and possibly even the red, green, and blue sub-pixels that make up the pixels). If you take a magnifying glass (or look *very* closely) to your screen, you'll be able to see the same gaps in between the pixels. But, you're not going to see that same pattern you see in the picture you took. Why? Because our eyes don't work on a grid pattern. When we look at something directly, we're able to discern all the details we want based on how close or how magnified we want it. Any lack of detail will just blur itself out because it's not able to be focused as well on our rods and cones in our eyes, which aren't really laid out in any distinguishable pattern (and *definitely* not straight up/down lines). For a camera, it's different. It has a very strict grid that it measures the light with, so if *another* pattern lines up weirdly with it (like the grid of the pixels on the screen), you're going to see an interference pattern happen with the image you take. This is the Moire pattern. Also, when you are viewing that same photo at a smaller size, you won't see the pattern any more because groups of pixels get blurred together to show a smaller version, meaning all the details of the grid get washed out and lost (check out bilinear or trilinear filtering if you want to learn more about this)."
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nr7bow | Why Do a Lot of Small Files Take Longer to Copy Then One Big One? | Technology | explainlikeimfive | {
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"It's like the difference between sending one envelope containing a 100-page manuscript vs. sending a hundred envelopes containing a page of the manuscript each. The resulting manuscript is the same size in each option, but with the second option the receiver has to spend time opening a hundred envelopes.",
"On disks, at the beginning of the filesystem there is a section that is used to store inode(index node) data structure. It's like an array, or, more accurately, an array of objects/struct. And each file has its own inode that tells the system things like file size, permission, and block number that the data of this file locates in. To copy a file, you will have to first find a free inode, write new metadata into it, then allocate new blocks somewhere else on the disk to store the actual data, write down the new block number into the inode, and then copy the data to the block that has just been allocated. Meanwhile, most modern filesystems have journaling function. Which means the system will need to log what the operation is and to what extent it has finished this instruction to make the system be able to recover from accidental power loss or crash. With that being said, for each file that you want to copy, there will be a short overhead time introduced. For a large file, you only need to do those extra steps once. But for an operation on thousands of small files with the same total size, you will need the same time plus thousands times of the overhead time. Therefore it will be significantly longer.",
"Each file copy has some overhead - you have to find the file, find a new location, move all the metadata, record the transaction information for crash resistance, and then actually move the data. These actions take time. They ruin memory locality - accessing non-sequential parts of disk and RAM - which breaks various optimizations the computer tries to make by pre-loading or reusing things. They can also take significant logic in addition to just the bare hardware actions of data copying."
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nr80hp | With film photography, ISO was physically and chemically determined: big ISO = big grain, low ISO = fine grain. Why do digital sensors work with the same constraint? Why can’t we electronically have big ISO and fine grain at the same time? | Technology | explainlikeimfive | {
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"With electronic sensors, the effect isn't really grain size & mdash;obviously the sensor pixels don't vary in size & mdash; it's the amount of \"noise\" on each pixel. In other words, at high ISO, the brightness of each pixel varies randomly from what it should be. It's like listening to a faint audio signal; turning up the volume helps but you hear more hiss. With digital pixels the same thing is happening; turning up the ISO is like turning up the volume to make a weak signal stronger. The original signal always has some small amount of random error, but when you turn up the ISO by amplifying the signal more, you also amplify the errors which makes them more obvious in the resulting image.",
"They don’t, digital noise is only superficially similar to film grain but it’s actually quite different. Film grain is more like the size of the pixels which is constant for a given camera. When you turn up the ISO on a digital camera you are effectively turning up the amplification (think like a volume knob on a speaker), this makes the dark image you want to capture appear brighter, but it also makes any random noise (caused by thermal effects in the sensor, quantum effects etc) brighter as well."
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nredvu | What is the noise some cars make when reversing? | I always wondered why it sounds different from a “normal” forward drive. | Technology | explainlikeimfive | {
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"Most forward driven gears are helical, so they mesh together on an angle. They're more expensive to produce and require synchronizers, but they are quieter. Usually reverse gear is a straight cut (spur) gear, which is much cheaper to produce and doesn't require a synchronizer. The trade off is they are much nosier and produce that whining sound. [Helical vs Spur gear]( URL_0 )"
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nrmjiy | why do downloads occur at faster rates along the download process? | Technology | explainlikeimfive | {
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"Downloads are done over the TCP protocol, and TCP gradually ramps up the speed until it finds how fast things can go. When you're downloading something you're constantly sending confirmations of \"yeah, I got this bit\" to the source, and the source throttles things down if confirmations stop arriving in a timely manner. Things also start quiet and gradually ramp up, until the system finds the maximum speed that works."
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nrwjej | Why do vinyl records always spin at 33 or 45RPM? Why not every any slower speeds that would allow for more music on each side? | Technology | explainlikeimfive | {
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"There's a trade-off between the speed of the disc and the quality of the audio stored on it--if you spin it slower then less of the vinyl will pass under the needle every second, so to get the same quality you'd have to have more detailed vibrations in the groove. Having said that, 33 and 45 are not the only speeds ever used. Many years ago, when manufacturing techniques weren't as good as they are now, in order to get decent quality the records had to spin at 78rpm. There was also a brief-lived record format that spun at 16rpm, but the audio quality was so bad it could really only be used for spoken voice and the like, not music.",
"The slower a record turns, the worse the audio sounds. Due to this, in order to provide the best sound possible, the record needs to turn faster (higher RPM). However, when a record turns faster the amount of information it can hold on a record is reduced thus having a shorter playback time."
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nrwrwq | How does chrome take 4 gb of ram? That is like 5 full movies. | Technology | explainlikeimfive | {
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"Since the introduction of Javascript websites are not just content shown to you. Websites are full on programs - some of them very complex with thousands and thousands of lines of code that is run by your browser. Look at Facebook - the website is an instant messenger program, a media player, an image viewer, a tracker (I'm sure a lot of the workings of the site are about tracking your interactions in minute detail), and a rich advertising program - and this is all running on your PC for every tab you have open. So you're not just holding the content, you're holding everything to make the website \"program\" run. Websites couldn't be as dynamic and responsive as this if they were just rendering content.",
"Every tab and extension in Chrome is divided into its own process, so if one crashes, it doesn't take down the entire web page or all of your open tabs at once. This is much more convenient for you, but it may cause Chrome to consume more memory because it must replicate some operations for each tab. Other things are going on behind the scenes as well. For example, Chrome's prerendering functionality uses more RAM, but it speeds up the loading of your web pages. Additionally, certain extensions or websites may leak memory, resulting in increased RAM utilisation over time.",
"Speaking about the computer industry in general there has always been a balance between the cost of development time vs the price of hardware. Back in the 80's and early 90's RAM was extremely expensive. A reasonable computer might only have a few kilobytes of RAM, up to several megabytes by the mid 90's. The cost of storage (hard drives) has always been an order of magnitude cheaper. To make software fit on a computer developers had to be very clever in finding ways to maintain efficiency in the code. Using what little RAM they had as effectively as possible. Come the 2000's and suddenly the paradigm shifted completely in the other direction. Computers now have several GB of RAM as standard so developers now spend more time on features and performance vs efficiency. Computer programs today are also orders of magnitude more complex than in the 80's. A developer axiom is \"computer programmers are lazy\". What's meant by that is don't re-invent the wheel, if someone already made a wheel use that instead and save yourself some time. Pre-written code is called a library, instead of having to write code to perform a common function you can instead use code in a library to do it instead. But these libraries are often quite large when you only require 1 small part, or they weren't particularly efficient in the first place. So developers have a tendency of loading all of these libraries in memory just in case they need one. - The more you can load in RAM, the faster the browser will be. Every time you have to pull something from the hard drive it slows down your computer significantly - Websites and browsers have massive inefficiencies in them. Memory leaks, extra libraries, redundant processes, and other crap that fills up RAM with time. Chrome doesn't control what code is on a particular website either, that's fault of that websites developer. - Developer teams can't be bothered to make it better because there isn't enough time, current industry focus is on new features (more profits) rather than making existing code better. - Extensive debugging time these days is more likely to be spent plugging security holes (playing security whack-a-mole) than making the underlying code better. - Many Web developers are fundamentally multimedia experts and graphic designers. Many are self taught, most don't have high end computer science degrees. This means that have very little understand of the underlying processes on a computer and make \"pretty stuff that works\" rather than \"stuff that works extremely well\" - More often than not it's \"easier\" to leave unnecessary libraries and crap in RAM in case you need it later, even if you aren't using it now. RAM is too cheap these days for developers to care that much. - Extra plugins and add-ons for your browser add to it's workload, and they aren't always super efficient at it. - Computers these days rely heavily on computer languages like Java, PhP, HTML, C#, etc that don't run code directly to the OS but instead run through an interpreter like the web browser. This has the advantage of making code multi-platform in that it will run as easily on PC as Mac or mobile devices. The problem with that is that they are inherently inefficient as a result because they add all these extra layers ontop of the OS to run. This in turn leads to more performance loss, and even sloppier code. In my own opinion the industry has taken a really wrong turn in the past 10 years and hasn't learned from its mistakes yet. The price we paid for adding under-powered and oversimplified mobile devices (smart phones and tablets) to our ecosystem is everything is now bloated, inefficient, and runs like crap."
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nrz1fr | What does an MRI of the head make images of exactly, and what is it used to look at/diagnose? | Is there sometimes dye used in an MRI? What is this test used to diagnose/see versus for example a PET scan? TIA. | Technology | explainlikeimfive | {
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"MRI scans are physically mapping the concentration of hydrogen, what this means for the human body is mostly measuring water and fat. They produce a structural image for example in the brain you can see all of the grey and white matter (and they appear different which is useful diagnostically). They’re using for diagnosing pretty much anything which causes a structural change in the brain like Alzheimer’s. MRI does occasionally use contrast agents but it’s rare as most MRI imaging doesn’t require it. A PET scan on the other hand measures the distribution of the tracer you inject, eg some sugar analog with a radioactive isotope. This lets you map metabolic processes, seeing where that tracer gets concentrated in the body. For example cancer cells use a tonne of sugar because they are growing so much, so if you image them with a PET scan then they can be easily identified. My experience in this is from studying physics involving medical imaging so someone with a medical background may be able to elaborate on exactly what they can be used for."
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ns2o5q | - How do applications like Google Maps and Apple Maps know when there is a traffic jam? Where does the information come from? | Technology | explainlikeimfive | {
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"Most people have phones with location sharing enabled. They can tell what traffic is like based on how many phones are on the road and how fast they are moving. This works especially well for highways. They also have a lot of historical data to work with and a lot of mathematical models that show how traffic usually forms and how long it tends to last based on the roads and the number of people caught in traffic. This gives them the ability to make some general predictions about how much the traffic may slow you down. Of course it isn't perfect! Sometimes traffic is caused by an accident and no model can predict that an accident will occur or guess how long it will take to clear the road and get people moving again. There are many factors that can cause the algorithm to guess wrong and take a longer path sometimes. That's why some people prefer to use their own intuition and sense of direction instead of a map app.",
"As others explained, they use the data from the mobile phones of the general public... Which might sound like conspiracy theory BS, but it has been tested and proven. Here is the story of a guy with 99 phones and no car: URL_0",
"People in cars use their devices for navigation. Their devices transfer data on their location to application servers. The server part of the application analyzes this data and figures out the average current speed of users depending on location. Places with low speed and many users are currently jammed."
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ns3vml | can someone give me an understanding of why we need 3 terms to explain electricity (volts,watts, and amps)? | Technology | explainlikeimfive | {
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"Think of a pipe that we're going to pump water through. Now imagine you put your face at the open end of the pipe. The voltage is the pressure the pump puts in. The pressure will drop depending how long the pipe is. The current is the amount of water that moves through the pipe per second, the flow rate. The watts is how hard it hits you in the face, or how much it pushes you back. I could send a low pressure and high flow rate and you'd have a shower. Or I could send a high pressure and the same flow rate and pressure wash your back deck.",
"NB: The water analogy is great but doesn't explain the whole story. In the same way, my analogy works to explain a different side. Both aren't complete because, let's face it, electricity is pretty complicated. Think of balls going through a chute [like this]( URL_0 ), but without the stop at the end. This chute is always filled with an *endless* amount of balls. They just keep pouring out. The chute is quite horizontal and the balls don't really roll fast. You decide to pick up the upper end and raise it, so it stands up more. Suddenly, the balls pick up speed and go faster. The balls get more energy. This angle, this is equivalent to the voltage, for which we use the unit **volts**. Now go to lower end, take a stopwatch and count how many balls fall out in 10 seconds. 20, maybe? The more balls come out during this time, the higher the current: the more **amps**. Now, for power, remember how I said the balls get more energy? That's important, because you can do things like that, like move the pedals on your bike. If you take the amount of balls and the amount of energy each has and multiply it together, you get power: for which we use the unit **watts**. Some might wonder why I explained it like this. The water analogy is easier. Well, this analogy also explains one other thing with electricity: charge. Every ball is an electron, which has charge. The unit for this charge is **coulomb**. Electricity is electrons(balls) going through a conductor(chute), they go through with a certain energy(volts): the more energy it has, the more can go through in a shorter time(amps). If we know how much energy each electron has and if we know how many balls pass through a conductor every second, we can calculate the energy passing through the conductor every second(watts). EDIT: For everyone saying my analogy is not 100% correct, you're right. But remember this is ELI5, getting a rough grasp of the subject matter is more important than full accuracy.",
"Because they are different things. We aren't Squanchy speaking in squanch. Voltage is the charge difference between two things. Current is the flow of electrons, measured in Amperes. Watts are the combined measure of the two for power. Volts x Amps = Watts.",
"The three terms we actually need are volts, amps, and *resistance*, which is opposition to current flow (amps). The reason we need these three terms to talk about electricity is because they are dependent upon each other. If you have a known voltage, the amount of current that will flow is dependent upon the resistance. More resistance = less current flow. Less resistance = more current flow. Power (in electrical terms) is the ability to do work, and is calculated by multiplying volts times amps. It actually gets a little more complicated than that but that's the basic equation.",
"Amps (Amperage) is how many pixies there are. Voltage is a measure of how angry said pixies are. Devices choreograph the pixies and make them dance. Wattage is how many pixies dance in a given time. DC pixies always go in a circle from negative to positive. AC pixies frolick back and forth. Pixies always want to dance and go to sleep in the ground. No matter how angry the pixies are, there have to be enough of them to hurt you.",
"If electricity was a waterfall, then volts would tell how high it is, amps how wide it is and watts how much water goes over the edge per second.",
"Electricity flows in much the same way water does. Volts is like the pressure in a pipe. The higher the volts the more force can be applied. Watts is the amount of energy per second so it is like the energy you can get from the flowing water. An amp is an amount of charge flow per second. So it is the amount of water flowing in gallons.",
"##Electricity :: Water Electricity is like the water in a waterfall that is spinning a mill wheel. You need two things to run the wheel: 1. a lot of water. 2. for that water to be falling. ###Waterfall Height :: Elecric Voltage Voltage is how tall the cliff is. You can get more power from each drop of water if it's a tall cliff, but that doesn't tell you if there's actually a LOT of water or not. ###Amount of Water :: Electric Current Amperage is current, it's how much water is actually flowing. It's how wide the waterfall is. More water means more power, probably, but you still need the water to actually be falling, otherwise it's a pond and you can't run a watermill with a pond. ###Wattage is Total Power, influenced by both amount of water (amperage, electrical current) and by the height the water is falling (voltage) Multiply the two together and you get wattage, which is how much power you actually are getting. How much that waterfall is actually going to move the watermill. Niagara Falls is a huge river (current, or amperage) with a tall cliff (height or voltage). It could power a huge watermill. A small but tall waterfall (low amp, high voltage) is useful, and so is a huge lazy river (low voltage, high amperage). A tiny lazy river (low amp, low voltage), not so much. Final factlet: static built up on a balloon has really high voltage, but very low amperage. It's like someone hitting you with a single drop of water at really high speed. Doesn't actually hurt, but only because there isn't very much of it.",
"* We need voltage (volts) and current (amps) to describe electricity. * Watts is a measure of power that is commonly used for electricity, but it's not strictly for electricity. * You can describe any source of power in watts. * So to counter OP's question, we don't *need* watts to explain electricity. * We could just use \"Volt-amps\" as the unit. * But using a term like watts to neatly represent volt-amps is easier.",
"The old water pipe analogy: Volts is the \"pressure\" of the water. (technically the pressure difference... if you pumped the water back down the pipe harder than your water company pumped it towards you, then the water would flow the other way, wouldn't it?) Amps is the size of the pipe. Watts is the total amount of water flowing through the pipe. It's a combination of the pressure and the size of the pipe. Big, high-pressure pipe have far more water flowing through them than small, low-pressure pipes, or big low-pressure pipes, or small, high-pressure pipes. The bigger the pipe (amps/current), the more water can flow through it. The higher the pressure (volts), the more water can flow through it. (And resistance, the one you missed off, is the obstructions/difficulty of pushing water through the pipe... imagine a very crusty old pipe where the water can't flow as well through it because it's 90% limescale. If the resistance is greater, it's effectively like having a smaller pipe, so you get a lower current through it, and the harder it will be to push lots of water through it). Big pipes (circuits with high current capacity) can happily supply small amounts of water (low current) but small pipes (low current capacity) cannot supply large amounts of water (high current). To know the total power (amount of water) that you're putting through the circuit, and the amount it can handle, and the amount you need, you need to know the size of the pipes of each part (the current) and the pressure you're pushing that current down there with (voltage). If you only know the pressure you're pushing, that's not enough. The pressure on one pipe would be fine, but on another it may blow it apart. If you only know the size of the pipe, that's not enough. A large pipe will handle high pressure well, a smaller one will tear itself apart. So you need to know both. And some pipes have a size that can't be made any larger (e.g. in your computer/phone, there are paths that can only handle so-much current because of their small size), so you have to know and control how much water/power could go through them. And some \"power supply\" devices (water pumps) can only give a certain pressure (e.g. batteries can only push a small voltage, mains electricity can push a larger voltage, and substations can push an even larger voltage), so you need to know what pressure can be taken by each part, and how to move from high to low pressure (e.g. by increasing the size of the pipe) and vice-versa. And, when combined, pressure and pipe size will tell you the total amount of water - the power you're putting into the system, and the power going into each part. Watts is \"unnecessary\" in that sense. As is resistance (Ohms). They can both be worked out from the other two. But you need at least two, and then the others will reveal themselves to you. Power = Voltage x Current (stated as P=VI) Voltage = Current x Resistance. (stated as V=IR) Pick any two and you can calculate the third / fourth from them. So technically only 2 measures are essential. And voltage/current appear in both, so they are all you need.",
"ELI4. 'Can I drop a rock on your foot?' 'MUM, TIMMY WANTS TO DROP A ROCK ON MY FOOT.' 'Timmy, why do you want to drop a rock on your sisters foot?' 'It's an experiment, mummy.' 'Show me the rock.' 'Oh, alright. See, it's not very big. Can I? Please?' ... 'Where are you going to drop it from?' 'Nevermind.' While volts and amps are important quantities, in isolation, they don't tell you a lot. But power is a useful quantity in it's own right as it tells you how much work, or heat, or pain is going to be generated. Just like driving a nail into a block of wood you can use a small tack hammer and swing it lots of times, or you can use a large hammer and hit it once. It's all about the nail. Or the foot.",
"Electricity is the flow of \"charge\", or more specifically electrons. Electrons have a negative charge. Just like poles on a magnet, alike charges will repel each other so if you have \"too many\" electrons in one place they'll want to move down the line until they are evenly spaced out. Voltage describes the difference in charge (number of electrons) between one place and another. Obviously those places need to be joined by materials which will allow the electrons to flow which is why you need to physically join those points with conductors in order to get any electricity. If you have no difference in the number of electrons, then there's no incentive for any of them to move and you have no flow (no electricity). The larger difference you have between two points, the higher voltage you have and really this describes the available \"pushing force\" in your circuit. I think an easy way to picture \"voltage\" is with your experience of static electricity. Electrons are the tiny, outer-most particles of an atom which means they're easily displaced (transferred from one atom to another). Let's say you're walking along an insulating carpet in insulating shoes. The electrons making up those atoms can be easily transferred and so before you know it you have an \"excess\" of electrons stored on you, but because they have no easy way to flow, they stay stored on you... until you touch a conductor. Now all of a sudden those excess electrons have an easy path to somewhere with fewer electrons and you feel a shock as they rapidly do. The other example is the classic \"rub a balloon on something then hold it near hair\". The same transfer of electrons happens through the rubbing, but because you haven't given them any way to flow what you see, as you bring the balloon close to the hair, is the electrons in the hairs atoms being attracted to the balloon because the balloon has lost a lot of its electrons through the rubbing (they want to move to the balloon, but can't, at least not easily). Amperage describes how quickly that charge (electrons) passes through the circuit. If you have a nice thick wire which will allow lots of electrons to pass through it at once, you'll have a high amperage. If you have a very thin wire which limits the flow of electrons through it then your amperage will be lower, even though the voltage (the \"pushing force\") remains the same. Wattage is a measurement of energy over time; while I've explained Volts and Amps in terms of the number and movement of electrons, wattage makes more sense when you introduce Voltage as a measurement of stored energy. Volts = energy per electron, and Amps = electrons per second (well, sort of, electrons are tiny, so they're actually measurements of millions of electrons rather than a single one). If you multiply that \"pushing force\" by how quickly the electrons are actually moving through the circuit (energy per electron, and electrons per second) you'll get an \"energy per second\" (Watts) result.",
"[ URL_0 ]( URL_0 ) & #x200B; this is the easies way to understand i found out.",
"Think of it like water. Voltage is like water pressure or how many psi your faucets have. This is important because low pressure might not provide enough force to do something, and too much pressure might break things. This is Why electronics require a certain amount of volts, but not too much. Amps is like speed, how many miles an hour your water travels down the water line, it is determined by the pressure (and the resistance, which is like how wide or skinny the pipe is). This is important because a high water velocity can be dangerous even if the pressure is low. Watts is like how many gallons per minute you get out of the faucet. It is determined by volts multiplied by amps. This is the unit used to describe exactly how much power a given device uses, theoretically you could lower voltage and increase amps or vice versa and a device could keep running until it runs into the aforementioned problems with low or high volts/amps",
"Imagine you’re giving away free money in your store today. You’re gonna have a flow of people going through your door. Voltage is how much money you’re giving per person (relative to how rich the people are). If you offer 100 dollars per person people will come really fast, very motivated. 10c per person, it won’t pull people as much. When you see electricity jumping - blue sparks like static or lightning , this is a high voltage. Like if you offer a million dollars per person people will literally jump over rivers to the avoid the queue for the bridge. How many people are passing through thru your doors each second ? This is current , amps. It will depend on how money you’re offering (volts) and narrow your doors are (the Resistance of the electric cable). Ok then imagine some clever criminals hear about your promotion. They wait on the street to rob everyone leaving the store. But they can only do it for an hour before the police will come. So they need to know how much money they can potentially make per hour to know if it’s worth it. They do “money per person” (volts )multiplied by “people per second” (current , amps) That is power, watts. It’s the rate at which money / energy is flowing. Then to workout the total money in an hour , they times this number by 3600 (seconds in an hour). Now they know the total amount of money moved in an hour. This is an amount of money / energy, can be called a watt hour , (or a kilowatt-hour is 1000x this) and it’s how the electricity company charge you."
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nsfrdf | What does Data Roaming do? | Does it increase data speed? Should I have it on or off? | Technology | explainlikeimfive | {
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"Data roaming allows you to have a data connection when you're not on your \"home network\". For example, if your contract is with AT & T in the US, if you're on AT & T's network you're not roaming, if you're on anyone else's network (typically in other countries) you're roaming. Roaming data charges can be \\*very\\* high (like thousands of dollars per month) so most phones have the option to turn data roaming off. You should generally leave it off unless you're sure that your plan covers data roaming and/or you want to pay the potentially very large bill.",
"By default, your phone connects to the cell tower that is owned by your cell phone service provider (AT & T, Verizon, T-Mobile, Cricket, etc.). And, it is constantly trying to connect to a cell tower to make sure you have service, as long as you're not on Wi-Fi or airplane mode. Now, with Data Roaming *off*, your phone will *only* connect to cell towers that it is authorized to according to your subscription plan. So if you're a T-Mobile customers, it will only connect to T-Mobile towers, or towers related to a T-Mobile service. With Data Roaming *on*, your phone will *try* to connect to a T-Mobile tower first, but if it can't find one, it will connect to whatever else it can find to ensure you've got a steady connection. This is great if you're outside your normal service provider's area of coverage, *but* it can also cost you extra for data, phone and messaging fees when you're on the other provider's tower. How much you owe, if anything, will depend on the terms of your plan. As far as having it on or off... Really just recommend keeping it off if you have good coverage with your phone, unless you've got some magical contract that makes it free :\\",
"Roaming in this context is the act of using your phone in an area/country not covered by your provider. Within your home country, your phone works via the network provider that provides your contact. An AT & T phone connects through AT & T cell towers, and AT & T deal with everything. They only have the license to broadcast their signals in certain countries however. So if you travel into a country where your provider doesn't exist, your phone is now useless as there is no appropriate network available for you to connect to. This is where roaming comes into play - your network knows it is a useful feature to have your phone be able to work in multiple countries, so they have made agreements with the network providers available in various other countries to allow your phone to work - so instead of connecting to your usual network, your phone will connect to the local company that your network has an agreement with and still work. The issue is that this can come with a cost. Because you are not using your normal network, there can sometimes be additional charges to use your phone which can be pretty expensive. The option in your phone's settings to turn off days roaming means you can stop your phone from sending or downloading any data if it is not connected to your normal network, unless you specifically allow it - so you won't get a nasty surprise because your phone has been quietly downloading email in the background, running up a data bill that is being charged by the megabyte. Incidentally a lot of networks will have better agreements that will not cost you so much - European carriers for example I believe all have no roaming charges. So if you travel from Germany to Spain, you will connect to the local network, but will use your normal phone allowances and it won't cost you any extra. So if you are traveling, definitely check with your network to see what the rules and costs will be."
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nsgblc | why do screens look weird through cameras? | I would post an image of what I’m talking about but image posting is disabled. | Technology | explainlikeimfive | {
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"This is a phenomenon called a moire pattern. Basically, the pixels of the screen are misaligned with the scan that your digital camera performs. It doesn't happen with non digital cameras.",
"Because the screen doesn't have a constant picture, it's actually cycling through and blinking the pixels so fast that we just see a constant image. A camera takes a picture very fast (and sometimes not all at once) so your picture captures the screen as it's in the middle of going through pixels.",
"These are called Moire patterns. [They form when you overlap two patterns]( URL_0 ). Parts where both grids stick out appear to add together and form darker structures. Your digital camera has a grid of sensors that react to the incoming light, which is uses to determine pixel values. Your screen is also made of a grid of pixels. These grids usually don't align, so a Moire pattern forms."
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nsjp1y | Why aren't computer-viruses as common on cell phones as they are on PCs? | Technology | explainlikeimfive | {
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"There’s a few reasons. The first, and most obvious is that most software is installed through an App Store now which (in theory) vets the submitted code. Things do slip through, but it’s not as common now. However, the biggest element is that computers as a whole are just more secure now. Things like (good) virus detection being built into an OS standard and into web browsers, better practices (such as how Microsoft Office handles Macros), and other bits (Like MacOS’s ability to block non signed apps), just combine to make computers harder to infect for the average person. Of course the underlying code has been improved too. But, it’s important to note that viruses are a threat on mobiles.",
"They are really common on phones. Like terrifyingly so. There have been a lot of malware takedowns over the years on both the iOS store and the Play Store for apps that have been installed millions or tens of millions of times. You can also get malware installed from just browsing web pages. There have been cases where just receiving a text could install malware on your phone. The thing is that in pretty much all of these cases the malware is designed to hide itself. So you don't know it's there. They usually just want to track you. Sometimes they make you send spam texts. Or fake adclicks to a specific developer. Or mine crypto. Or just steal all your private data or bank accounts. Or just sit there waiting for instructions. And they usually go through insane lengths to stay hidden. Some have been mass installed by millions and only seemed to target a handful of people. This problem is WAY worse for devices that don't get security updates anymore. As in the absolutely mind boggling number of old Android devices out there that haven't received any security patches for years. Most of the users of these devices don't even know they've been compromised because at the end of the day most of the malware wants to stay hidden as much as possible.",
"Frankly, I think it's because of Windows. Android and iOS devices run on Linux/UNIX. These operating systems are much, much more secure than Windows. Windows still runs on some very old code that was originally written in the 80s and 90s. To this day, there are ways of breaking into Windows systems that haven't been addressed for decades. For example, when booting into safe mode, it is possible to replace the on-screen keyboard app with a copy of Command Prompt in Windows' files. When you boot the machine normally, you can access the \"on-screen keyboard\" without logging in. Now that you've replaced it with Command Prompt, you have direct access to enable the default administrator account and get in without ever cracking the owner's account. This method of bypassing Windows security has existed for as long as I can remember. It's shockingly bad."
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nsk4u2 | What does solder actually do in electronics? | I understand that part of it is for structural support, but what else is it for? | Technology | explainlikeimfive | {
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"It is basically just conductive glue. It holds electrical components in place and allows them to conduct electricity along a path between them and the next components in the circuit.",
"It’s a means of connecting wires to wires, or wires to circuit board, which means energy/data needs to be passed through it. It is structural - but also conductive; meaning any electronic signals can still pass through solder and into whatever the solder is connected to."
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nsnu0d | How does the newly required vertical 911 location work? | I can understand how cell tower can triangulate using x and y coordinates, but how does the tower know z? I would have thought that would be something the phone would do but it's apparently on the carriers. How the heck does that work? | Technology | explainlikeimfive | {
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"Carriers could already use GPS as a reference point for altitude if there were four or more satellite signals reaching the phone. To further enhance location accuracy, your phone has a barometric pressure reader. Pressure changes with elevation (this is also one of the sensors fitbits use to determine floors climbed for the day). & #x200B; Readings can be pulled from this sensor and combined with the GPS / tower triangulation data to get within a 3 meter vertical reference point for the caller. The carrier requirement wasn't to develop an entirely new z-axis technology, but rather to refine the accuracy of the measurements and send the results over the e911 system. & #x200B; ELI5: Your phone already knows your rough elevation, so all carriers have to do is grab that info from your phone and send it to the 911 center."
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nsyeb2 | My headphones "broke" and now I don't hear lead vocals anymore and the sound quality is really bad - Why? | This is the 4th time any of my headphones "break" like this. It's really fascinating hearing the background vocals and...basically everything that's normally "hidden behind" the lead vocals of my favourite songs. | Technology | explainlikeimfive | {
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"Your cord / connector is fucked. It's a stereo-mixing thing - the voice is usually exactly centre, and the music is around the edges. Your ground connection has broken, so it's effectively subtracting one channel from the other - filtering out what's common, and only playing what's different. If it's possible to replace the cord, your headphones themselves should be fine. If not, make sure your next headphones use a separate cable, rather than a hardwired one. Then when this happens next time, you just go buy an aux cord. (some brands use stupid small-diameter sockets; gotta watch for that)"
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nsyzyf | How did they do color correction/color grading on film (before they used computers)? | Technology | explainlikeimfive | {
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"They didn’t really. You could control the RGB values by adjusting the printer lights. But no grading in the sense of how we do it today. Different kinds of film had different looks to them though. And lighting is a big aspect of how a film looks."
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nt3pu1 | How does end-to-end encryption work? | Technology | explainlikeimfive | {
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"Your computer generates two numbers using fancy math: one of them is used to encrypt the message and the other one is used to decrypt it. You keep the decryption number private, but you give the encryption number to anyone who wants to send you a message. Since everyone has the encryption key, they can all make messages to send to you, but since only you have the decryption key, you're the only one who can read them. The tricky part (besides the math, which some very smart people have already figured out for the rest of us) is figuring out how to make sure that the encryption key I'm using really belongs to you. Back in the Day when end to end encryption was mostly the domain of paranoid nerds, people would meet in person to verify each other's keys. With the apps that make this easy to use, most people are relying on the app provider to tell you the right encryption key.",
"Something more ELI5: Imagine you have an envelope you want to send to a friend through the postal service, but have important things on the paper. For the info to be secured, you put the envelope in a box with a lock, and give a copy of the key to your friend. That way, you can open it at your end and no one in the middle.",
"The most common kind of encryption is known as \"symmetric encryption\". This is where two people both know the same secret number, known as a key. They can use an encryption algorithm to send messages to each other in a way that no one else can read those messages without the key. Symmetric encryption is easy and fast to compute, but has a weakness in that you have to somehow share that secret key with your partner before you can communicate with them. Thankfully, there's a fancy mathematical trick known as [Diffie-Hellman key exchange]( URL_1 ) that lets you do just that. It's a fancy math trick that can let two people, talking over a public channel, to somehow agree on a shared secret key in a way that anyone eavesdropping on the conversation can't recover the key. It's not the only way to have end-to-end encryption, but it's a perfect example of how to do it. ---- This is how Diffie-Hellman works: Let's say Alice and Bob want to create a key so they can send encrypted messages to each other. To do so, first Alice and Bob agree on a public number, *P*. This number gets transmitted publicly, so it's not a secret. Then, Alice and Bob then individually create separate secret numbers, *A* and *B*. Next, they use a particular mathematical trick to combine *A*/*B* and *P* to create new numbers *AP* and *BP*. Finally, they can then send these new numbers to each other (again, over the public internet, so eavesdroppers can see them). The math trick is hard to explain (it involves exponentiation and modular arithmetic), but essentially, it's very easy to put numbers together, but very very hard to take them apart again. You can easily take *A* and *P* to make *AP*, but turning *AP* back into *A*, even if you know *P*, is nearly impossible. Even a supercomputer would take millions or billions of years to calculate *A* from *AP* and *P*. After the exchange, Alice knows *A* and *BP*, and Bob knows *B* and *AP*. Alice of course can't get *B* from *BP* (and vice versa for Bob), but she doesn't need to. She can use the trick again to combine *A* and *BP* in the same way to create *ABP*. Likewise, Bob can combine *B* and *AP* to *also* get *ABP* (it doesn't matter what order the numbers are combined, they have the same result). Thus, Alice and Bob both now share a single secret number, *ABP*. Meanwhile, anyone who's listening on their conversation, like Eve, has only been able to copy down *P*, *AP*, and *BP*. Because there's no easy way to separate numbers using that math trick, Eve has no way to combine these numbers to create the secret number, *ABP*. She can only combine them to make, *APP*, *BPP*, or *ABPP*, all of which are useless. If that example was hard to follow, Wikipedia has a [diagram that explains the trick using paint colors]( URL_0 ) ---- Anyway, the cool thing with Diffie-Hellman is that literally no one except Alice and Bob need to know the secret number. Even the service they send messages over doesn't need to know the secret. All it needs to do is pass messages between Alice and Bob. All the secret math is done locally on Alice and Bobs' devices. That's what makes it *end-to-end* encryption -- only Alice and Bob can see the messages, anyone including the message service they use cannot."
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nt7udv | What is a transistor and how can 16 billion of them fit into a tiny microchip? | Technology | explainlikeimfive | {
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"A transistor is basically an electronically controlled light switch. With convention home electricity, you can compete a circuit by physically bringing a piece of metal in contact with another. But then come semiconductors. Normally, silicon does not transmit an electrical signal. But, if you inject a little bit of another chemical into a spot on it... it still doesn't transmit an electrical signal. But then, if you also apply a small charge to the area, suddenly it does! This lets us create a light switch where the open/close action is not done via a piece of metal physically moving, but instead, another electrical circuit coming in to help align the \"doped\" section properly. This is a transistor. An electrically controlled electrical switch, with no moving parts. As for how we can fit so many in a small area... progressive improvements. As we build better and better machines, we can get them tighter and tighter to each other in manufacturing. There was no one sudden jump, just years of incremental improvement.",
"There are a number of types of transistors. But essentially they are electical switches. They have 3 connections, one controls the on/off and the other two are where the electrical current to flows from through and to. By connecting switches in the correct manner, you can create the basic logic building blocks (and, or and inverters) which can then be connectdd together to make more complex cells. They can be extremely small, or an individual transistor can be the size of the chip itself.",
"A transistor is a voltage controlled switch. While there are several types, I'm going to focus on MOSFET transistors as they are the ones I am most familiar with. A MOSFET has three ports: Gate, Source and Drain. Depending on the voltage applied at the gate port, a specific amount of current is allowed to flow between the source and drain ports. This means that you can create larger and more complex circuits (logic gates) by chaining the source & drain ports of a given transistor to the gate of another. How this works is a bit more complex to explain. MOSFET stands for \"metal–oxide–semiconductor field-effect transistor\", which is a mouthful. The metal-oxide-semiconductor part refers to the silicon that the transistor is made from. It's relatively easy to \"dope\" silicon to create internal crystal structures that make it easier or harder for electrons to pass through the silicon. MOSFET transfers are made of layers of these different kinds of silicon layered together really thinly. This will create regions which electrons will either want to travel through or have a hard time traveling through. If we apply an electromagnetic field to those regions, we can make it harder or easier for electron to pass through them. This is the field-effect part, and it is what allows us to control the operation of the transistor. We can still get these effect to work with amazing small layers of silicon, on the scale of single digit number of atoms, which allows us to create microchips with billions of them."
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ntc8bv | How do spam callers mask their phone numbers to ones registered to someone else? | Technology | explainlikeimfive | {
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"When you get a phone call and a number shows up on your caller ID, that's not always because your phone knows which number is calling it. The phone that's calling you can send the call *and* tell your phone what number to show, plus maybe a name as well. Scammers use a VoIP phone and can just alter the data that their phone sends to your phone, your phone doesn't know any better and just shows what ever the other phone tells it to show. Edited for clarity.",
"It's called spoofing, and it actually exists for legitimate reasons. For example, a business with many individual phone lines may want them all to show up the same on caller ID so that customers call the correct number back. Or a person may want calls from their cell phone to appear to come from their office phone. Unfortunately now we're dealing with people misusing this system. It used to be somewhat complicated to spoof a phone number but these days it's trivially easy. That's because a lot of phone traffic isn't actually done over traditional phone networks, it's done over the internet using a protocol called voice over IP (VoIP), in which case all you have to do is send deliberately incorrect caller ID data.",
"The telephone backbone operators such as AT & T have no incentive to block spam calls. They profit from it. Perhaps it even makes up the bulk of their call traffic. So although they could shut down the spam, they will be making excuses until they are forced to somehow. The reality is, despite the fact that the presentation caller ID may be spoofed, the billing number cannot be spoofed. The VoIP call traffic is well known as it enters the telephone network and they turn a blind eye to it.",
"Phone guy here. Depending on the carrier, I can send whatever the hell I want over as the caller ID. I can legit send 123 to your phone. Now you have to sign all sorts of legal docs saying you won't do anything untoward... But when has that ever stopped anyone. It's just a field in the PBX (phone system) and we can put whatever we want in there. It's normally used to send the main number of the facility or department, but nothing stops me from sending complete bogus junk. Also, VoIP has nothing to do with it. It may make cheating easier, but I can send absolute trash over a standard PRI (old fashioned telephone service on a T1) with the right settings.",
"Spoofing is when you are pretending to be a directory number that does not belong to you and masking is when you want outbound calls to appear from a different directory number of your org. Masking is done for a number of legitimate reasons. Most carriers will check and enforce the format of the directory number but do not check if that number is yours. If carriers enforced not accepting directory numbers onto their network that don't belong to the peering org we could eliminate a lot of spam and spoofing. They have the network resources to do this but it would add some overhead and cost and would require laws and regulations which isn't easy.",
"They use software on their own phone station (PBX, which they connect to other phone systems' network) to spoof the caller ID. There are often little to no checks on Caller ID validity in systems that control the whole thing. It is enough for the spammers to be a trunked client of a phone company (e.g. via a PRI or a SIP trunk) to get enough access for this. Many completely normal businesses subscribe to such service, there is nothing unusual in having a PBX to route calls in your enterprise office.",
"It's called caller ID spoofing. Like several others have said, the extremely boiled down version of it is you can use software to mimic whatever number they want. You know those calls you may get what there's no one on the line? Scammers typically send out probing calls to determine if the number is active or not. If the number is in your area code and exchange (first six numbers) then it's either a probe, or if you answer and someone with an Indian accent starts talking about a \"suspended social security number\" or some such other nonsense, just hang up. Also, if you subscribe to a voip service, please PLEASE create secure passwords for your account and log in often. I work as tech support for an ISP/voip provider.",
"When a phone call is setup over a digital connection, the originating call system has the ability to set the outbound calling information, name and number along with some other information, which is transmitted along with the call setup data. This data could be overridden by the phone carrier but is typically allowed to pass. In a legitimate scenario, this is how you know to call back an individual versus a main number in a local business. In nefarious scenarios this information is either blanked out, completely random, or chosen to be something likely to be more acceptable to the called party such as a local number. By happenstance that number at times is someone you already have in your contacts, but many times not. A truly crafty organization could use leaked call records to ensure that they only present the call as coming from a number you have called by searching in leaked call record data."
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ntlpwe | Does a hard drive change its weight if it's full storage? | Technology | explainlikeimfive | {
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"No, it doesn't. Data is stored as electrical charge, either on the platters of the drive, or within the solid state memory chips on an SSD. Adding electrons to or removing them from sections of the storage does not alter the weight. Additionally, the \"empty space\" on a hard drive isn't just a bunch of zeros. It generally has either old deleted data, or random data. What gives each sector of the platter meaning is the record of what files are located in what locations on the drive. So, the actual difference between a full and empty drive is a little bit of the structure of that index.",
"An \"empty\" hard drive isn't physically empty, it's just full of random meaningless data. In the beginning of the hard drive there's a table that says what files are on the drive, where they are physically located, and which parts of the drive are currently vacant. The vacant spaces are just filled with random 0s and 1s.",
"Wait wait wait... Magnetic drive or solid state?",
"No. A hdd is sort of like a collection of light switches. The data is stored by leaving each switch up or down. The switch doesn't change weight depending on which way its flipped."
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ntn8ud | how does companies like Apple says ,,this product is non-repairable” but you can still repair it? | Technology | explainlikeimfive | {
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"There’s a big battle going on over ‘right to repair’ right now URL_0",
"Because they want you to pay three times as much for their licensed repair people instead of attempting to do it yourself. If you can do it yourself they don’t get more money out of you. Some companies also have proprietary parts, for example, Nintendo has proprietary screws that you need to buy a specialised screwdriver for, to discourage people from attempting to repair things themselves."
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ntqee8 | How can modern scales not just tell me my weight, but also how much of that weight is water, muscle, fat etc. | Technology | explainlikeimfive | {
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"They use electrical current. It's called bioelectrical impedance analysis (BIA). When you stand on the metal contacts on the scale, a small electrical current passes through your body. Different types of tissue offer different levels of resistance to that current. That said, BIA scales are notoriously inaccurate. Even the best scales can be off by quite a large margin, particularly due to the way the numbers can be greatly skewed by things like your hydration level."
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ntt6oi | Why aren't phones like laptops when installing operating systems ? | I mean you can get any random laptop install windows or linux on it and it just works but for phones you have to get custom roms specific for your phone. Aren't phones essentially same as computers ? | Technology | explainlikeimfive | {
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"Technically this utopia is totally possible. This problem is basically a manufactured one. Apple won't let you do anything cos it wants the absolute control over your devices and the OS on them. Within android things are a little more open, you might be able to install some other flavor of android if you could get your phone's bootloader unlocked, but you'll have to jump through hoops. Basically everyone wants to lock you in, to some extent.",
"Yes and No Phones require a purpose built and stripped down operating system to work on their hardware, so you can't install PC windows on them for example. But why aren't phone OS's universal like on PC? Because the phone manufacturers *want* it that way. They've deliberately engineered the market so that you have to get both the hardware and OS from the OEM. Everything is proprietary. Android is an open source platform but manufacturers still tweak it to make it proprietary for their devices (ie drivers and plugins). They've created an ecosystem where they control the hardware and the OS exclusively, and have a stranglehold on the peripheral market. They also create devices with built-in obsolescence ensure that people will have to but new phones every couple of years. Even simple things like batteries are functionally not replaceable in modern smartphones which seems like a massive over-site but is in fact a deliberate act to encourage people buy entirely new phones instead of repairing older ones. Eventually a 'universal smartphone' will be developed, but the big manufacturers have zero interest in letting this happen. In the short term this will only happen with regulatory (ie government) interference. Left to their own graces the PC industry would have done exactly the same thing, but a critical mistake made by IBM in the late 70's led to 'universal computer' that we take for granted today. IBM at the time saw no future for a Personal Computer so they didn't bother to design one. That was until Apple released the Apple II. In a desperate attempt to get to the market IBM built the first PC using off the shelf parts, and used a pre-written OS (DOS) written by one of it's partners Microsoft. Because most of the parts were widely available, and IBM foolishly hadn't secured an exclusive contract with Microsoft for the OS, other manufacturers like Compaq and Dell were able to reverse engineer the PC and flood the market with Clones at half the unit cost. Other computer platforms like Amiga and Commodore also existed at the time, but the universal PC won out in the long run exactly because it was a universal platform. Purpose built machines with restrictive hardware and software licensing became doomed to be niche product (like Mac's today) Today ALL PCs are clones, there are no original IBM machines left."
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ntuu0w | What are compressed and uncompressed files, how does it all work and why compressed files take less storage? | Technology | explainlikeimfive | {
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"File compression saves hard drive space by removing redundant data. For example take a 500 page book and scan through it to find the 3 most commonly used words. Then replace those words with place holders so 'the' becomes $, etc Put an index at the front of the book that translates those symbols to words. Now the book contains exactly the same information as before, but now it's a couple dozen pages shorter. This is the basics of how file compression works. You find duplicate data in a file and replace it with pointers. The upside is reduced space usage, the downside is your processor has to work harder to *inflate* the file when it's needed.",
"Lets say I have a file that contains following: aaaaaaaaaaaaaaaaaaaa I could compress that like this: a20 Obviously it is now smaller. Real compression comes from redundancy and from the fact that most data is wasteful in the first place. A byte is 8 bits and thats basically the smallest amount of data that can be moved or stored. How ever, if you type a message like this, this only contains 26 different letters and some numbers and punctuation. With 5 bits you can encode 31 different characters, so we could already compress the data a lot. Next level is to count the letters and notice that some are way more common than others, so lets give shorter bit lengths per character for those. You can look into Huffman coding for more detailed info. Another form of compression is lossy compression which is used for images, videos and sound. You can easily reduce the amount of colors used in the image and it would still look the same to humans. Also you could merge similar pixels into same color and say that \"this 6x6 block is white\".",
"Suppose you're writing a grocery list. Your list initially says this: I need to get 6 eggs I need to get 2 liters of soy milk I need to get 2 liters of almond milk I need to get 1 pound of ground beef There's a lot of repetition in there, right? A smart compression algorithm would recognize that, and might render it like this: I need to get 6 eggs 2 liters of soy milk 2 liters of almond milk 1 pound of ground beef An even better compression algorithm might be able to further improve things: I need to get 6 eggs 2 liters of soy milk almond milk 1 pound of ground beef This is basically what compressing a file does. You take information that's repeated multiple times and remove that repetition, replacing it with instructions on how to put it back when you need to reconstruct the original content.",
"I like the text examples One for movies or animations is where they only save what changes between the frames. So if you have 100 frames all black, change them to one black frame and set it so that it takes up the same length of time as the 100 frames did. If you have a shot with blue sky, and it doesn't change because all the action is going on in the lower half of the frame, save the blue part of the frame and lengthen it/draw it out the same way as was done with the black, once something moves, only then do you have something you need to keep. This can be done for 10000 frames in a row, or it can be done if there are 2 frames with only 10% of the screen the same as the one before it.",
"Compression works by finding patterns in the data and then storing those patterns instead of the data itself. There are lots of different way to do this and a lot of different theory involved but it is the basic principle. Compression does work better when the compression algorithm is built for the specific file type. So a generic compression algorithm that is made to work on any file does not work as good on say image files as a dedicated image compression algorithm. Some algorithm might even opt to lose some information that is not important and does not fit into an easy pattern. This is most common in image and video where the exact value of each pixel is not that important. Compression algorithms also do not work if there is no patterns to the data. So random data, encrypted data or already compressed data can not be compressed any further.",
"Software programmer here. Like all binary data, files are stored as a series of 1's and 0's. Now imagine you had a file that was just a million 1's. If you wanted to describe this file to someone, it would be a lot smaller to write \"a million 1's\" instead of actually writing out \"1\" a million times. That's compression. More formally, compressing a file is actually writing a program that can write the uncompressed file for you. The compressed size of the file is then the size of that program. Decompressing the file is actually running the program to build your uncompressed file. More structured data like a large rectangle of a single color compresses well because it is easy to write a program that describes that data. On the other hand, random data is not very compressible because it does not have any structure and so you can't do much other than have your program actually write out the entire number, which is not going to be any smaller than the entire number itself. This is also why compressing a compressed file does not save more space. You can think of compression like squeezing juice out of a lemon, where the more structure that exists in the file, the more juice there is to squeeze, but once you have thoroughly squeezed it, there is no more juice left. Compression turns highly structured data into low structured data, so then when you compress again, you are dealing with random-ish data that doesn't have enough structure to take advantage of. You can also turn this backwards, and attempt to talk about how random some data is by measuring how easy it is to compress. There are two types of compression. The type I described above is lossless where the uncompressed file is exactly the same as the original file. Lossless algorithms are typically not that complicated and usually look for large areas of the file that share structure, like I mentioned above. Zip files are lossless. The other type of compression is lossy, where the uncompressed file does not have the same data as the original file, but has some sort of acceptable amount of data loss built into it. In return, lossy algorithms are far better at reducing the size. Lossy algorithms can be very complicated. JPEG and MPEG files are the main example of lossy compression. From personal experience, if you save a BMP file as a JPEG file, it will tend to be around a tenth the size of its BMP file. However, the JPEG file will not be the same pixels as the BMP file. The compression algorithm for JPEG files have been specifically tuned for photographs, so if you see a JPEG photograph you probably won't be able to tell that some pixels have been altered. However, for something like digital art, especially pixel art, it is much more noticeable, so you should never save digital art as a JPEG.",
"I have actually implemented file compression technology, so I feel particularly authorized to answer this question. Software needs to see files whose contents it understands. This is why software authors design file formats to be optimized to the particular needs of the particular problem their software is designed to solve, be the files written documents, audio/video recordings, spreadsheets, executable programs, scripts, etc. These needs do not necessary take into consideration file storage resources. So, when a user's file storage space is filling up, it's often in their interests to find ways to store **the exact same data** in a **smaller space**. That's what a data compression file format does. It is a way of analyzing the content of a file, identifying *self-similar parts* of that file (that's important), and recoding the file to take advantage of the fact that it can reduce the redundancy within the file to be able to store the content of the file in its own, compressed file format, which takes up less space, which is the whole point. Disk storage is not the only place where data compression is useful. Network transmittal of data benefits in taking less bandwidth and/or less time to transfer data from one place to another, if the data is compressed at one end and decompressed at the other. This, of course renders the data into a file format that the software which originally understood the file's contents no longer understands. This is the reason compressed files are given new filename extensions, so that even at the File System level, it becomes obvious that the contents of a file are compressed and so no one, human or software, makes the mistake of trying to operate upon that file's contents as if they were only encoded in the original, inner file format. Sometimes, this can be handled at the File System level, wherein the software responsible for reading data from or writing data to the actual storage media is the layer of software that takes responsibility for compressing the file's contents on write, and uncompressing the file's contents on read, which has the benefit that the file can be stored in its compressed state, consuming less space, while the original software is free to consume the file's contents, seeing only the file format that it expects. Often, software will expect its files to be compressed by external programs and so it can be architected to allow itself to be configured to detect compressed input and transparently pass the file through the appropriate decompresser program before trying to use the file's contents. Because one of the goals of compression is to reduce the redundancy of the encoded data, the compressed results have less redundancy to begin with, and so it's not possible to compress already compressed data to get the file even smaller. In fact, trying to compress already compressed data will often result in a doubly compressed file that's larger than the singly compressed file. This is due to the compression file format's meta data overhead, as well as other factors. This is often true even when two different compression schemes are used in tandem, not just reapplying the same compression scheme multiple times. Some file formats, for example audio/video recordings, are already encoded in some manner of compressed form. These are often \"lossy\" compression standards, such as JPEG or MP3, that explicitly throws away some data in order to make the image or video or audio appear identical when consumed by a human, while also rendering the data into a form that is more amenable to compression. It's fine to recode a \"lossless\" audio file to a lossy one, if the human ear will not be able to tell the difference between the playback of the lossy and the lossless encodings. Other data types, for instance executable program code, would not be amenable to lossy data compression, since actually changing the details of the instructions in the program would likely be fatal to the execution of the resultant compressed-decompressed program. For such lossless data compression schemes, it is paramount that the round-trip conversion of < original data > (compression) < compressed data > (decompression) < uncompressed data > give the result that < original data > and < uncompressed data > be bit-for-bit identical. There are many different compression schemes at work in the world. Each one does what it does in slightly different ways. It is impossible to create a single compression scheme that works equally well on all kinds of data. The compression scheme at work in MP3 files is actually so specialized that it's covered by a patent owned by the Fraunhoffer Institute. However, as adept as the compression scheme in MP3s is at compressing audio data, it would not work nearly as well for spreadsheets or written documents. Likewise, the kind of compression schemes that might work well on written documents would work very poorly for video streams. The diverse needs of different types of data and the continual research and development of computer algorithms insures that there will always be a new file compression extension to learn sooner rather than later.",
"Imagine you want to save a message: AAAAAAAAAA AAAAAAAAAA AAAAAAAAAA AAAAAAAAAA AAAAAAAAAA BAAAAAAAAA AAAAAAAAAA AAAAAAAAAA AAAAAAAAAA AAAAAAAAAA It takes 100 characters to save it. You could save it as: 50*A,B,49*A And have it saved 11 characters. This is lossless compression, and a kind of thing (though obviously a very primitive version) that, say, 7zip or winrar do. You could imagine a different algorythm that saves even more space: 100*A And voila, you saved your message in 5 characters. Well, not exactly your message, you lost the B, but it's very close to the message, maybe reader wouldn't notice the B anyway. This is \"lossy\" compression, where you sacrifice some information the original had in order to save even more space. This is (a very primitive version of) what saving an image as JPG or music as MP3 does. Of course, these formats are popular because they are very good at only loosing the information humans actually don't notice, but idea is the same.",
"Just a fun example of compression. I used the zen of python. For simplicity, I removed all punctuation and made it lower case. I'm sure there are better ways to compress this as well. Original: 807 bytes > beautiful is better than ugly > > explicit is better than implicit > > simple is better than complex > > complex is better than complicated > > flat is better than nested > > sparse is better than dense > > readability counts > > special cases arent special enough to break the rules > > although practicality beats purity > > errors should never pass silently > > unless explicitly silenced > > in the face of ambiguity refuse the temptation to guess > > there should be one and preferably only one obvious way to do it > > although that way may not be obvious at first unless youre dutch > > now is better than never > > although never is often better than right now > > if the implementation is hard to explain its a bad idea > > if the implementation is easy to explain it may be a good idea > > namespaces are one honking great idea lets do more of those Compressed generated with some code: 709 bytes > \\[\\~=is;!=better;@=than;#=the;$=although;%=never;\\^=idea; & =complex;\\*=special;(=should;)=unless;{=obvious;}=it;|=implementation;\\\\=explain\\] > > beautiful \\~ ! @ ugly > > explic} \\~ ! @ implic} > > simple \\~ ! @ & > > & \\~ ! @ complicated > > flat \\~ ! @ nested > > sparse \\~ ! @ dense > > readabil}y counts > > \\* cases arent \\* enough to break # rules > > $ practical}y beats pur}y > > errors ( % pass silently > > ) explic}ly silenced > > in # face of ambigu}y refuse # temptation to guess > > \\#re ( be one and preferably only one { way to do } > > $ that way may not be { at first ) youre dutch > > now \\~ ! @ % > > $ % \\~ often ! @ right now > > if # | \\~ hard to \\\\ }s a bad \\^ > > if # | \\~ easy to \\\\ } may be a good \\^ > > namespaces are one honking great \\^ lets do more of those Compressed after manual modification: 673 bytes > \\[\\~=is;!=better;@=than;#=the;$=although;%=never;\\^=idea; & =complex;\\*=special;(=should;)=unless;{=obvious;}=it;|=implementation;\\\\=explain;:= \\~ ! @ ;'= # | \\~ ; < = to \\\\ }\\] > > beautiful:ugly > > explic}:implic} > > simple: & > > & :complicated > > flat:nested > > sparse:dense > > readabil}y counts > > \\* cases arent \\* enough to break # rules > > $ practical}y beats pur}y > > errors ( % pass silently > > ) explic}ly silenced > > in # face of ambigu}y refuse # temptation to guess > > \\#re ( be one and preferably only one { way to do } > > $ that way may not be { at first ) youre dutch > > now:% > > $ % \\~ often ! @ right now > > if'hard < s a bad \\^ > > if'easy < may be a good \\^ > > namespaces are one honking great \\^ lets do more of those & #x200B; Edit: Dang reddit messed up my formatting. Should be fixed now",
"Compressing and uncompressing a file is like translating a book into a different language, except you make up the language based on what's in the book. To make files smaller, you have your new language use very short words for the most common words or phrases in the original language, and longer words for the uncommon ones. Then you have to make the dictionary that translates back to the original language, or figure out rules so that you can construct the dictionary, and then the compressed file is the translated file plus the dictionary. In most cases the compression method (or translation) is chosen to be very good for \"normal\" files, but bad for \"uncommon\" files that you generally wouldn't encounter. Mathematically you can't have a one-to-one translation that converts every possible combination of letters into a shorter form, because then some combinations would have the same translation and you wouldn't know which one was the original when you translate it back. If you don't need *exactly* the original file because it's something like a picture, you can have a translation that is always shorter, but in general if you try to compress an already compressed file it doesn't get smaller."
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nu86tq | how are NTFs bad for the environment | Technology | explainlikeimfive | {
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"NFTs themselves do not particularly use a lot of energy - they are simply a capability that exists within some cryptocurrencies to uniquely associate some data with a user, and transfer that association in a transaction. The environmental harm is not a result of this capability or any other transaction-related capability, but of the underlying blockchain consensus algorithm - the way everyone in the world agrees which transactions have taken place in the past. Currently, most cryptocurrencies use proof of work, which means that when a block (a list of all the transactions people are trying to make) is inserted, everyone tries to insert it at the same time by trying to compute a value associated with that block. The first one to compute it successfully gets to also insert a small transaction to themself, which is the motivation for trying to do it above and beyond simply wanting the network to continue running. This process uses quite a bit of energy.",
"NFTs are based on the same Blockchain principles as cryptocurrency. As such, they require a large amount of computer power to maintain, which means there's a large amount of electricity needed. One estimate was that a single NFT requires an amount of electricity equivalent to a month's usage for the average EU citizen."
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nub1h1 | How are large pieces of plywood made if they're even longer than tree trunks? | Technology | explainlikeimfive | {
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"Plywood is made by gluing together large sheets of wood that are made by [peeling off the diameter]( URL_0 ) of the log, then cut to size and layered with the grain going in opposite directions,for strength.",
"Plywood is made by plying off a sheet of wood from the trunk. This looks very similar to how you would sharpen pencils and you end up with the long sheets of wood. You often see this in the plywood as the wood grain pattern is repeated over and over which is because it is all from the same tree but at different depths. In addition to this plywood is glued together allowing them to just put multiple plies next to each other. The glue and the other layers of ply will make it strong enough."
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nubv9l | What's The Difference Between Software And Firmware? | Hardware is the part of the device you can touch, software the the part that makes it do stuff, so where does firmware fit in? Is it just a subcategory of software? | Technology | explainlikeimfive | {
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"Firmware is software installed on hardware for the express purpose of telling the operating system or other components how it should use the hardware.",
"If you look at a Hard Drive. HDDs have their own circuit board with a processor, memory and motor controller and are pretty much a separate little computer on it's own. The software that runs that mini system is called firmware and isn't stored on the main computer or on the motherboard and very seldom (if ever) needs to be updated."
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nuc4o3 | Why can't anyone reduce an air conditioner or refrigerator down to truly portable size? | There seems to be a lower size limit for conventional, compressor-based refrigeration. The result is that portable cooling devices are always simple fans, or at best, evaporative cooling units. What prevents conventional refrigeration and air conditioning from working at sizes much smaller than a dorm refrigerator? | Technology | explainlikeimfive | {
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"Are you talking about walking around with a personal A/C unit strapped to your back and keeping you cool while you move about your day? The main issue is the fact that you'd basically be conditioning the atmosphere around you and net no benefit. A/C units work because they take heat from one location and exhaust it in another (window unit sucks room air into the fins, transfers the heat the the refrigerant, the now cooled air is blown back into the room, and the hot refrigerant is then cooled by the outside air and the cycle repeats). If you don't have a closed environment to pump the cooled air into and a separate environment to pump the heated air into you're just spending energy for no net gain. In order to have a mobile, air conditioning unit that you can take around with you, you'd basically have to wear a suit that traps the cooled air against your body to benefit you.",
"The HVAC system in a modern vehicle is not only portable, it’s about as small as practically feasible. The compression required by the system demands a fairly strong power source to drive the refrigerant pump. It’s not just a fan.",
"Cooling cycles don't generate cold. They simply move away heat, and thusly they need a hot side. Which means for these things to have any effect at all you need to be able to place the hotside outside of the room/system that you want to cool. If the entire device has a small form factor this wouldn't really be possible"
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nucc6v | How do spam callers call you from fake numbers with area codes that are relevant to you? | Technology | explainlikeimfive | {
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"The phone system is intentionally set up to allow spoofing the number you're calling from. Imagine you've got a business with multiple office locations. Whenever someone makes an outbound call, you want the caller ID to show your businesses inbound number. This is why you can spoof caller ID. As for how they get relevant numbers, it's because of the information collected about you along with your number. They may, for instance, scrape Facebook for hometown info and full in area codes to match. These spreadsheets of information get sold and traded around many times.",
"Phone spammers operate on the internet. There are exchange services between VoIP and PSTN networks, so they're making internet calls into the phone system. It is a feature of the phone system that they transmit a caller ID when they establish the circuit from caller to callee. It is a feature of the phone system that you can specify your own caller ID. This has a legitimate business application - call centers can have hundreds or thousands of numbers, but they want to present a uniform callback number to be identified by, and callbacks can route through their private exchange. So spammers have automated a system where they will present your area code, and then the rest of the number can be effectively random. The idea is to make you believe the call is local, and therefore somehow relevant to you, like it's a local business or neighbor. That might have been more effective 30 years ago, but since the age of the cellphone, I had a Chicago area code and lived in Portland. I don't think I've ever known anyone who actually had an area code in the area they actually lived. So if I get a call from my area code, I know for sure it's spam. As a bonus fact, by federal law, all calls must be connected. This goes back to the early days of the telephone network, when the military needed a reliable national network. They didn't want to deal with competing networks where your call would be connected only if you called from the same network, so it was a mandate that calls had to be able to cross networks and be connected, and carriers couldn't intentionally degrade connection quality or anything. So the phone companies know when a call is spam, but up until very recently, they've had very little they could do legally to stop them. You have to receive the call, and you have to be the one to decline it. But what they did manage to do is if a call is coming from an internet exchange, it's almost certainly spam. In that case, they can at least warn you that it's potentially a spam call. And this also works by blacklisting. A legitimate exchange business would keep spammers from using their service, and companies that use VoIP and don't want to be flagged as spam will pay money to use an exchange in good standing. Oh, and there are online services, they take a few steps to setup, but you can route calls through them, and what they do is any restricted or spam number, they can strip away the fake or restricted caller ID info. This is more helpful with restricted numbers and weird people you might know calling and harassing you. For spammers, this will get you the outgoing number at the exchange. That might not be a valid incoming number, so you probably can't call it and connect, and it certainly won't call back to the person on the internet. And it will also strip away the legitimate business use case. So if your bank were to call you, you wouldn't know them by the call center number they called you from, and you wouldn't necessarily know who to call back if your call was interrupted."
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nud63i | Why did old TVs require that the channel be on 3 before accessories like VCRs and game consoles could work on them? | Anyone who grew up in the CRT era of TVs remembers that you had to turn the channel to 3 before you turned on the VCR or game console. Otherwise, the picture would not work. Why was this so necessary? Edit: woah this blew up while I wasn't looking! Thanks for the replies! | Technology | explainlikeimfive | {
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"Channels on old CRTVs that had TV *tuners* are basically different frequencies that you tune your TV to, like how you turn your radio to a specific frequency to pick up a channel you wanted to listen to. Edit: it was channel 3 (or the selectable alternative to avoid interference) because the NES/VCR had to be talking in the same \"language\" (channel 3 frequency 60-66 MHz, channel 4 frequency 66-72 MHz, or channel 5 frequency 76-82 MHz depending on where you live and which had the least interference for you). Back in that day we had no way of transmitting the image and sound from the game console or VCR directly to the TV like we do today with S-video, component, HDMI, Display port, etc. So the simple solution was to turn the image and sound into radio ~~waves~~ frequencies and transmit it to the TV like a TV station. To comply with Federal regulations this TV signal from the console would have to be very weak so that it wouldn't interfere with any other signal. This means that the console could only transmit the signal a few millimeters to centimeters. To get around this limitation they used coaxial cable to carry the signal but you still had to tune the TV into the frequency the console/VCR was transmitting at. This guy does a good job explaining that a NES and similar devices are actually mini TV transmitter stations. [~~ URL_0 ]( URL_3 ) [ URL_1 ]( URL_4 ) (I'm not sure what's going on with URLs today, people are saying my link is broken but when I click on their links, I get the exact same URL that I posted...) Edit: this really blew up. To clarify some things: * I accidently put radio ***waves***, the NES doesn't transmit (yes it's a transmitter) radio waves, it transmits electric Radio Frequency (RF) to the RF modulator/adaptor that translates that signal into the frequency range used by the selected channel. (There's probably something I don't understand about this as I understand modulation is changing the frequency rate to transmit more and varied information u/maxwellwood did a great job expounding on this [here]( URL_2 )). * Technically speaking anything that transmits electric RF also inadvertently transmits radio waves in the form of electromagnetic RF radiation. This is mitigated. Blocked by what is known as shielding. * Yes, I know about the two screw antenna connection. Technically, a coaxial cable is that two screw connection bundled into a single, shielded cable with a universal/standardized connector. * Yes, you can transmit your game console's frequency over the air to your TV with the appropriate Electric RF to electromagnetic RF amplifier. All electric RF produces radio waves as far as I'm aware whether on purpose or not. Doing this while remaining in the grey area of legality in most countries would get you a pretty crappy signal to the TV though at any distance you couldn't just use the cable. * All cables used to take audio/video (AV, A/V) from a device to a TV is a transmission of data regardless of electric verses electromagnetic.",
"Very similar to those audio device adapters which transmit on particular FM station frequencies, it's a very very localized pirate radio station. Except the switchbox was a direct interface to the antenna input, and did not transmit into the air. Channel 3 is a particular frequency and was commonly unused in most places (over the air) so there would be less interference/collision. If you area did have a channel 3 over the air then you had the choice of 4. And no market had channels immediately next to each other due to bleed-over, so if you had a 3 you didn't have a 4 or if you had a 4 you didn't have a 3. Usually the channels were 2,5,7,9,11 or such, nicely spread out, many markets didn't have a 3 OR 4 at all. Of course when over the air was mostly replaced by cable, there was less need for channel separations. And digital has no neighbor-bleed problem at all.",
"Older TV sets did not have inputs for devices. They could only display pictures that came in as TV signals. So the devices had to emit a TV signal. TV signals have to be on some channel. By convention channel 3 was used (only a few areas had a Channel 3 station).",
"When TVs were invented, it never occurred to the manufacturers that they could be used for anything besides broadcast content from regional television stations. That's what they are set up for: VHF broadcast reception within several predefined channels. When the first home video devices were invented (VCRs, computers, video games, etc) the only way for your television to recognize the signal was if the device in question created a signal identical to what the broadcast station would create. Conveniently, most televisions had the ability to connect an external antenna in the back. All your device had to do was convert the desired composite video into an NTSC broadcast signal with appropriate levels, and feed it into an antenna cable, which you wired directly to your television. The last step is telling your television where to find the signal. Most devices broadcast on either channel 3 or channel 4, and there was usually a switch on the back to choose.",
"Here's a cable TV company [\"Keep It On 3\"]( URL_0 ) customer education series of commercials from 1995, produced so that people with cable boxes didn't tie up the Customer Service lines, and trigger truck rolls, just because they didn't have their damn TV sets on Ch 3. OK, I made this. I went nuts. Managers gave me this assignment, they expected just a single commercial, perhaps with a service tech, wearing hardhat, standing in front of his van, saying: \"Please keep your TV set on Channel 3.\" Instead they got this.",
"You would have your normal cable line that had all the channels on it. You would plug this into your VCR. You plug another cable from your VCR into your TV. When your VCR was idle, it would just forward the signal from its line in onto its line out. However, when your VCR was on, it would interrupt the signal for one channel and put its own signal on that channel instead.",
"Is this a US spesific thing? Cause I had several CRTs growing up, the oldest one being from the 70s (which only has 2 tunable channels), and every one of these would work directly with game consoles.",
"Can someone explain like I'm 5 instead of talking about switchboxes, frequencies, bleed-over, accessories and TV transmitters. Fack",
"It's a cultural thing. In the UK we had two dedicated AV channels which didn't take up existing channel slots. And as far as I can tell, this is still the case for TV that don't have digital channels built into them.",
"I never got this - all the analogue CRT TVs I had were tunable, I used to put the console on channel 6 because we had 4 TV channels and I'd put the VHS on 5. Did American TVs not let you do that?",
"The accessory had a built inn TV transmitter. It would not output a high power signal so you could not use it to transmitt the signal over the air very far. But if you connected it to the antenna cable in your house it would be picked up by the TV. You would often be able to select what channel to transmitt on which would have to match the channel on your TV. But some channels such as channel 3 and 7 were common ones. This would be so that you did not accidentally transmitt on the same channel as your local TV station as then you would not be able to watch this TV station.",
"The joy when you found the right channel and you could hear the music and see Mario jumping around. You can hear it in your head now, right?",
"each channel is a different frequency. let's pretend that you have three people sending notes to three other people, but they're couples, and you can't mix the notes up. you mark each note with a color. now each person knows which note is theirs when they arrive frequency is how they're all sent together but the tv can know how to separate the channels old tv's didn't have extra inputs. it was the antenna or nothing. so you have to get a splitter so you can have more than one thing going in. and to the tv, it doesn't know what's connected. it just looks for the tv signals, so basically a signal that has all of those frequencies (like the colors in my example). so the vcr and nintendo and such all came with their frequency set to use the frequency that channel 3 is. (but not all, some used different ones, but not often) so, to be clear, let's say in the people example, let's say these notes are like the written subtitles for the different tv stations. you now get a new source of subtitles, how about a nintendo game. you just know that all extra sources send notes with a red label. so to view these outside sources of information, you have to go to the red note guy, as he is receiving them. and in the same way, the tv just thinks you want to watch whatever is being broadcast on channel 3. it thinks you're receiving this from the antenna. it doesn't know that you have a vcr or nintendo i think either 3 was the least used tv channel or maybe it was set aside for this purpose, but it's what everyone used for extra sources of media",
"Atari 2600 had a switch for 3-4 in case the channel 2 in the area was too strong and interfered with 3.",
"You used to have to hook up consoles to TVs using something called an \"RF adapter\" - radiofrequency adapter. This adapter would sit between antenna/cable and your TV. The way it would work is it would knock out the signal on that channel and replace it with that from your console. These adapters were noisy and sucked. For car audio, before aux inputs became standard on cars, they used to sell adapters that worked in a similar manner - you'd plug them into the cassette tape in the stereo, and they'd broadcast a really strong signal on a certain FM channel and occlude whatever was supposed to come over the radio that way, and those adapters also sucked and were noisy.",
"I don't feel like the other answers here really make this as simple as it could be, so I'm going to summarize my [video]( URL_0 ) on the topic: Televisions sold prior to the 2010s were mostly intended to receive a picture sent by a TV station over radio waves, called a \"signal.\" There are multiple TV stations in every town, so to keep signals from interfering with each other, they use a process called \"modulation\" which lets all the stations send the same kind of television signal, but using radio waves of different \"frequencies.\" A TV set can receive signals of many frequencies, then choose one and ignore the rest. This is called \"tuning,\" and it's how you choose one program to watch out of the many available. TV stations all use standard frequencies, to make sure every TV can receive from every station, and for convenience those frequencies are given numbers, and called \"channels,\" so channel 3, 4, 5, and so on, are always the same frequency no matter where you are. Although you can make a TV signal that isn't modulated, which we started calling \"composite\" when it became popular, there was nowhere to put that kind of signal into many TVs made before the late 80s. Old TVs only understood how to receive pictures on the standard TV station channels. To solve this, VCRs and game consoles all contained tiny \"TV stations\" that produced a very weak signal - too weak to travel through the air, but strong enough to be recognized by your TV if you put it into the antenna input. Your VCR had to send the signal on one of those standard channels, so the manufacturers chose channel 3, because it was available on every TV ever made, while some other channels weren't. Sometimes you already had a channel 3 in your town, and that could cause interference, which is why you could also switch your VCR to channel 4. Because of how television signals work, there can never be a channel 3 and 4 in the same region, so if you already had a real channel 3 station in your town, you'd use channel 4 on your VCR, and vice versa.",
"In France you had to set an unused channel and turn this $@?! wheel indefinitely until you see a scrappy picture.",
"You only had to do that when connecting via the TV's antenna or coax jack. With any other inputs, like composite or s-video, you did not. As for why, it's self-evident, don't you think? With the tuner input, stations are selected by channel. Your VCR or game console \"station\" can't broadcast on EVERY channel, so you have to tune into its channel.",
"Didnt have to be 3. You could use any channel. My house used channel 8 for whatever reason for the vcr/console. Channel 3 wouldn't have worked as here in the UK we have ITV which is traditionally associated with channel 3 following BBC 1 and bbc2. We also have Channel 4 which would obviously be tuned to 4 and later came channel 5 which you would tune to 5.",
"In the US it seems that each channel had a very specific part of the frequency spectrum. 3 or 4 was usually empty so that was a good place to put in the console. The Console/VCR was setup to \"broadcast\" to that frequency. As far as I know, in the NL where I grew up, there was no standard channel distribution - you had to look up the frequencies in a little book and setup each channel separately. Probably because it's a small country and there is no need for many overlapping broadcasting areas."
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nuduvk | How do batteries 'store' electricity? I understand that if you put electricity into a battery, the electric stays there, but how does that work? | Technology | explainlikeimfive | {
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"It's chemistry. There a many different kinds of battery but in general they have two metal plates, called \"Cathode\" and \"anode\" or \"negative side\" and \"positive side\", respectively. Between these plates is an unstable chemical that given the chance wants to react with the cathodes and anodes, releasing electricity as it does so. The reaction will only proceed if the battery is placed in a circuit where it can push it's electricity through the circuit. In other words electrons need to be able to leave the battery via the cathode plate and fresh electrons need to be pushed into the battery via the anode. If electrons can't leave and be replaced, the chemistry can't occur and the battery remains charged. Overtime, as the electricity is produced, the chemical reaction slows down and eventually stops, in other words, the battery is \"dead\". The chemicals in some batteries can be reset by applying an electric charge, backwards. They can then be reused and recharged again and again. Other chemistries don't allow this and once depleted are replaced."
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nukaeg | why is it unhealthy to stare at phones for long periods of time (like on social media) but healthy to read books? | Technology | explainlikeimfive | {
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"Instant gratification is one concept related to this question. When reading a book, your brain is engaged in an activity that requires critical thinking and patience. To find out the ending to the book you have to finish it. The brain is ultimately rewarded with the satisfaction of completing the book and interpreting its meaning. This is delayed gratification. Social media is an activity that requires no critical thinking. It rewards your brain every 5 seconds by giving you “stimulating” information rapidly. This is instant gratification. One fear is that we are losing our ability to simply exist in our own skin and we use the instant gratification of phones to distract our minds. Also, it’s possible to have an actual addiction to social media.",
"Because smart phones are the popular technology. Go back a generation or two and kids were told they'd ruin their eyes from too much reading and they should go outside instead. Go forward a few generations and people will be told it's unhealthy to spend too much time on the holo deck and they should be using their phones instead.",
"it’s just the mental health component of excessive social media use that is bad. A lot of people cannot handle constantly comparing themselves to others and seeing everyone’s life highlights while they scroll through it on a tiny phone. I also believe the human brain cannot handle being exposed to so many people’s lives and feeling a little involved in it.",
"A few things. The main ones I can think of are quality, light, and positioning. Quality: books go through a quality control process. Books have publishers and editors who have the job of making sure the books are good. The language is correct, and the facts are true. Meanwhile, a load of the internet doesn't have this. So, on average, books are better intellectually than the internet. Obviously there are exceptions. The are a lot of really good, stimulating things online. And there are a lot of books that are pure mince (50 shades of twilight). But on average, books are better (at least historically). Light: screens can mess up your sleep cycle. They give off blue light (as part of the white light). This tricks your brain into thinking it's daytime, making you less sleepy. This is why looking at screens before bed is bad. Meanwhile, books just reflect the light in the room. Positioning: phone screens are small. This means we hold them close to look at. This can strain the muscles in our eyes, which can cause damage.",
"Staring at screens is unhealthy for many reasons, it can cause eye fatigue and headaches due to the flickering and blue light emitted by screens, that books do not. A screen to you looks flacid and constant, but infact if you take a slow motion camera it is actually constantly flickering and emitting \"blue\" light which is highly fatiguing on the eyes. Books do not do this at all, as they are, well not screens. This is why blue light lense glasses are excellent for office workers especially, it blocks out the Blue light and can deter headaches and eye strain."
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numje5 | how early manually operated elevators worked | Ok so in the beginning there were no computer chips, and so the elevators had to be controlled via a dial manually inside the elevator, requiring an elevator operator, right? 1. Where was the power source? Was it on the lift or at the top of the shaft. If it was at the top of the shaft, how was it controlled, and if the motor was in the lift, then how was it powered? Was it via batteries, was there a set of switches that let you control the motor at the top of the shaft, or whatever? Was this constantly shifting wires/ pipelines dangerous? 2. How did they know where to go? Was there some kind of pipe where they could shout orders? I know that on every floor there's a button I can press, but what did they do when there was no button to press? How did they know where to go? | Technology | explainlikeimfive | {
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"Elevators work like a pulley, there’s actually two shafts. In one shaft is the elevator, in the other shaft is a counter weight that weighs similar to the elevator. Both hanging on a cable. Then a motor just spins that cable which does as much force as you’d think because of the counter weight, you don’t have to lift the whole weight of the elevator. For how the operator controlled it, there was a lever connected to a circuit that would tell the motor to rotate one way or the other, causing the elevator to move up or down."
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nunz3c | How did the Antikythera machine actually work? | I know there were cogs that predicted eclipses but how do cogs predict eclipses?? | Technology | explainlikeimfive | {
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"There's a fantastic YouTube channel where a guy is re-creating the machine by hand using only tools and methods available at the time. It's called Clickspring. He goes into a lot of how the machine works. Basically, all celestial motion is circles, and those circles happen at different rates. The earth rotates on its axis once per day, the moon rotates around the earth once every 30 days, the Earth goes around the sun once every 365.25 days, and the Earth has an axial tilt of 23.4 degrees. That means that depending on where the Earth is in its revolution around the sun, the sun will appear higher or lower in the sky. So what we need to find is a situation where the moon is between the earth and sun, the sun is at the right height at that time of day, and the observer is on the side of the Earth that's facing the sun. By using gears sized proportionally to each of those rotation times, you can track the movement of the Earth, Sun, and Moon in relation to each other at any point in time, then its just a matter of turning a drive gear an appropriate amount for the passage of time, and you can observe when the conditions for an eclipse will be met.",
"The machine modelled the movements of the earth and moon around the sun do that future alignments could be predicted. The cogs modelled the relative speeds of rotation."
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nus6q0 | What's the big deal about MIDI 2.0? | Why is the update to MIDI so important? What are the implications? | Technology | explainlikeimfive | {
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"MIDI 2.0 will enable a number of features currently not possible with 1.0, in particular, the MIDI signal can now be 2-way on the same cable, where previously you needed individual \"in\" and \"out.\" Because of this feature, the additional feature of \"profiles\" is possible. For example, if you plug a physical mixer into your DAW, the DAW can ask the mixer what it is, and the mixer can tell it \"I'm a Mixer!\" And the DAW will automatically map the faders, knobs, and buttons in your on-screen mixer to the appropriate corresponding items on the hardware. Another thing worth mentioning, 2.0 will be 32-bit, enabling better resolution of note velocity and even +/- cent tuning, per pitch. This enhances the \"realism\" of human expression when trying to capture it digitally. There are more features worth listing but hopefully this gives you an idea :) TL;DR the 2.0 update increases data resolution and provides quality-of-life improvements to everyone who uses MIDI.",
"Currently the implementation of MIDI 1.0 and the various revisions date back to around 1983 when the specifications for MIDI was implemented allowing various instruments to talk to one another, however the 1.0 protocol is only able to support up to around 34 notes of polyphony before you get drop off, but can be stretched, but usually only has around 2 or 4 different pressures of velocity that can be supported. Currently MIDI 1.0 is either 8-bit or 16-bit of information which is why some keyboards just are loud no touch control, while some are pretty good. MIDI 2.0 will allow two-way communication so two instruments no longer have to run in \"Master and Slave\" configuration usually in midi 1.0 your keyboard is the Master and the computer is the slave, accepting the information while the MIDI keyboard sends the signals. MIDI 2.0 will allow bi-lateral transmission between instruments and computers. So it should actually be able to support USB C, that said if you look at instruments such as the DX7 and its various revisions you will see that they have a MIDI in, MIDI Out, and Passthrough so it can be the master instrument controlling another MIDI enabled instrument, or be the slave following the another instrument or just allow you to dazy chain instruments together. Also this should allow much better things such as pitch control, the new DAWs for MIDI 2.0 should allow instruments and the program to communicate easily by requesting information to assign it. It also will allow the use of subharmonics allowing instruments to pull of feats that are not heard in western music by allowing each key to serve as a pitch bend in some. From what I heard it should make after-touch a more common add on."
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nuudpd | why do digital thermostats have both heat and cool settings, as opposed to a singular temperature control | (e.g why does 70 degrees on “cool” feel colder than 70 degrees on “heat”)? | Technology | explainlikeimfive | {
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"Depends on the thermostat, but generally cool is connected to an AC unit while heat is connected to a furnace. When heat is on the temperature might go above the selected temperature and when cool is on it might go below the selected temperature. It would be extremely inefficient to make the temperature be exact since a house has a pretty large volume. Thus the heating/cooling system is more of a greater than/less than system.",
"Instructing the system to repeatedly cycle between heating and cooling modes to maintain a narrow temperature range would consume A LOT of electricity/fuel as the system would potentially be running nearly constantly. While on a hot summer day, you really don't want to run the heater just because the AC ran a little longer than necessary.",
"There are two interesting parts to this answer. The first is covered by most of the other comments, in that it would be impractical to maintain the temperature at exactly one degree (e.g. 70). Instead it makes more sense to have a cool setting - \"keep it at least as cool as 70 degrees\", and hot setting - \"keep it at least as warm as 70 degrees\", to allow a little wiggle room. The other portion not covered in the other comments (at least so far) is that how cold or hot it feels is based on more than just the absolute temperature. Other interesting factors include things like direct sunlight, air flow, humidity, and air pressure. Besides the seasonal differences you may have for these that make you feel like 70 in the winter feels different than 70 in the summer, AC also serves as a dehumidifier, contributing to an AC induced 70 feeling different than a heat induced 70.",
"The same reason why analogue thermostats have them. \"Heat\" turns on the furnace and \"cool\" turns on the AC unit. Which is the same reason why one feels colder than the other. On heat the thermostat is trying to reach its sets temperature so the vents are blowing hot air. On cool the opposite it happens. In order to reguajte the temperature of the whole house the thermostat is place away from vents. So a room may be cooler or warmer than the set temperature when the thermostat turns off.",
"When you're cooling, the air conditioner is also dehumidifying the house. When you're heating, the heater does not dehumidify. This is why the same temperature will feel different.",
"70 is the goal temp, but HVAC systems use much cooler or much hotter air to efficiently get the temp to that level. An AC might blow 40 degree air, while a furnace blows 100 degree air. Each does do until the hot/cold air mixes with the ambient air to hit the desired temp. Also, an AC turns on and cold until temp drops to 70, while a furnace turns on to warm until it heats up to 70."
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nuw6l0 | How can IP Address be used to determine the location of the device? | I’ve seen social networks being able to track my device’s location “through my IP address,” and other websites’ privacy policy stating that they collect data such as IP address to determine your location. How does it work? | Technology | explainlikeimfive | {
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"Blocks of IPs are assigned to specific internet companies. Those companies publish Geolocation data for each of their network blocks detailing the general idea where the IP is located.",
"A little more clarification as this will undoubtedly become a bit more confusing as you think about it more. The location is returning to you is the location of your ISP. If you are in a smaller suburban town a few miles out of the city, the website will still think you're in that city because that's where your ISP is. When you commit a crime online and the police track your ip, they look up the ISP that IP is leased to and get a warrant to get the customer address of that IP address from your ISP and come for you. That is the only way to get a real, physical address from an IP."
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nuw98g | How does Apple’s “spatial audio” or other “3D audio” work when there are only two speakers? | Technology | explainlikeimfive | {
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"Humans locate sources of sound in space through frequency response cues (i.e., the bass/midrange/treble balance; for example, noises heard from far away will sound more muffled due to air absorbing the upper treble), the difference in time it takes for a sound to reach one ear before the other, the way the sound changes as you move your head around, and the difference in loudness between ears. Headphones and earphones can only simulate the last one and (to a much lesser extent) the first one because instead of letting sources of sound interact with your outer ear and other body parts naturally, you're piping sound directly into each ear. However, those interactions can be turned into a mathematical model by measuring how sound changes as you move a sound source around either a real or dummy human head (called a *head-related transfer function* or *HRTF*). You can apply this HRTF to audio digitally to simulate listening to something from speakers or live when listening to headphones. Also, sound bounces around real rooms, whether it's a home theater or an auditorium, which creates its own changes in when and how sound waves reach the ears. This can also be simulated through digital processing."
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nuxuib | How does my tv service provider determine which channels I get? | Technology | explainlikeimfive | {
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"Essentially all channels flow (or can flow) to your box at all times and you get only the filtered ones, depending on what you’re paying for. The TV box has a chip in it that acts as a filter. Your TV provider creates a custom config for the device (your very own filter) they put at your place, in-line with your service plan. To know which device is yours, they rely on the on-site tech that installs it to enter its ID in the system next to your name."
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nuy7vv | How do phone calls work? | Like …. I get the premise of the receiver and the sound is transmitted via radio waves…. But when you say it out loud?? We somehow trap our physical sound inside radio waves which you can’t physically see or touch and that transmits almost instantaneously and someone can then hear it ??? HOW | Technology | explainlikeimfive | {
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"To break it down at a general level: 1. Your voice makes the air vibrate. 2. The air makes a microphone vibrate. 3. The microphone turns the vibrations into electrical “vibrations”. 4. The phone interprets the electrical signal digitally. At this point, it’s sort of like an MP3 file. 5. The digital audio gets sent to the other phone. 6. The other phone plays it back just like a music file (and it’s almost exactly the inverse of steps 1-4!)"
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nv1s13 | How are status pages for major CDNs and major backbone providers designed to be up even though the provider is down? | Technology | explainlikeimfive | {
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"The computational requirements for a status page are extremely low compared to a full website such as e.g. reddit or facebook. It's extremely cacheable, lightweight, and read-only. There's no user authentication or policy enforcement logic. It's also, for obvious reasons, hosted on separate infrastructure from the main site. Furthermore, even during an outage event, a status site is going to receive less traffic than the actual site, since only a more savvy subset of the users will bother checking the status page.",
"The most obvious way to implement this is to host the status page with a competitor using completely independent infrastructure. Another trick which can be implemented is that if any part of the status page fails in some way it will just fail by showing the service as failed. So for example with todays fastly issue when the front end servers worked but the backend network had issues the frontends can be configured to show a status page with everything failing if they can not find the back end servers. This obviously does not work if there is any errors very early in the pipeline but at that point it is likely a problem with the clients network provieder anyway and the status page would be of no help.",
"A park you visit could be closed, but the signs at the perimeter and leading to it will still be there. It's much like this. The status pages are kept specifically in heavily redundant places, sometimes reside in multiple places, so that they can always be reached, and not at the same physical location as the site itself.",
"I can answer this as it's my job. I manage a large CIRT (Critical Incident Response Team) who provides critical incident services to over 45 companies, I believe its the largest CIRT in the western world at least. I see from a lot of your comments that you are looking at internal hosting solutions, **dont**, look at the already established industry tools in place, consider something like [statuspage]( URL_0 ) (and also take a look at ops genie, its magnificent)."
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nvc0vq | How do phones (and other devices) show the exact date and time even after being switched on after a while? | My phone was switched off since the past hour and I switched it on right now and I realised how normal it was for It to show me the exact present time and date and I wonder how. | Technology | explainlikeimfive | {
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"It has a battery-backed clock on the inside. You don't *have* to sync your time with the internet, and you don't always have an internet connection. If you don't, the phone still keeps relatively decent time while it's on. How? There's a circuit somewhere in the phone that serves as a clock. It might even be part of the CPU. One neat thing we figured out a long time ago is certain crystals vibrate at predictable frequencies when you run electricity through them. That's why you see a lot of watches say they have a \"quartz movement\". Both watches and computers take advantage of this. So basically a tiny quartz crystal gets installed in a thing that can count how many times it vibrates. Then some electricity is applied. The person who designed the circuit set it up so once the right number of vibrations happens, a \"tick\" happens. That \"tick\" might be once per second, but usually it's much faster so smaller amounts of time can be measured. The smallest amount of time that can be measured is whatever one vibration of that crystal takes. So even when your phone is \"off\", it's probably still running a tiny circuit that updates the clock. This only takes a teeny tiny amount of electricity. Many simple watches can go 3+ years on one battery charge. So your phone can stay off for a long time before that clock circuit drains the battery. PCs have this too. If you open most cases, you'll find a small watch battery attached to he motherboard. This is used to keep the clock running even when there is no power. There's also a battery inside some early Game Boy games like Pokemon Crystal that had a clock. By now many of the batteries have run out and those clock-based features don't work anymore if you turn off the game! Pretty much anything that has an \"off\" state and keeps the time is likely using a small battery-backed quartz clock to do so. These clocks aren't always the most accurate, though. Very accurate ones are more expensive. That's why computers tend to sync with an internet time source. My last PC could be as much as 5 minutes wrong if it went a day without internet connectivity.",
"Even when turned off, there is still a little bit of power being used to keep some fundamental operations of the device running, one of them being the system clock.",
"Turning your phone off does not cut the power to everything in your phone. Mostly just the screen and main processor. There's still a lot going on after you've powered it down.",
"There are a few different ways: * Some devices like TVs are never completely \"off\" - even when you turn the TV \"off\", there are some circuits that are still powered, such as a \"realtime clock\" chip. * Some devices like computers will have their realtime clock chip powered by a watch battery, so even when you unplug the device it will still keep track of time. * Some devices like your phone or your TV's cable box will just connect to a network and ask a dedicated timekeeping service what time it is. * GPS navigation devices get their time from the GPS satellites every time they connect."
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nvn82v | How can one companies 5G be “better” than another? Doesn’t 5G refer to the speed/strength of the connection? | Technology | explainlikeimfive | {
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"It all has to do with \"coverage.\" 5G is a *standard*, agreed upon by industry. The only difference has to do with how close you are to a 5G-capable cell tower (signal strength), which determines just how much you'll be able to do. Anything anyone says apart from that is...marketing drivel.",
"5G is a minimum standard. Specifically, it's the fifth generation of standards for cell networks (hence 5G). It's not so much a specified speed as it is an agreed-upon set of technologies and protocols that allow different networks and devices to work together. These technologies and protocols are more advanced than the previous generation, and as such networks built to that standard will deliver better speeds than networks built to 4G standards. Put another way, we're moving from horse-drawn carriages to automobiles. Some automobiles will be faster than others, or more reliable, or more luxurious, but they're all cars in the end. As long as you've got brakes, headlights, taillights, rearview mirrors, windshield wipers, and so on, you can register your car, slap on a license plate, and drive your car on public roads. 5G networks are the same way. As long as they're built to that standard, they're considered 5G. Yes, 5G marketing to the end user mostly just emphasizes connection speed, but coverage is also a big factor in what makes a network \"better\". Both also vary wildly according to the frequency used by the cell tower you're connected to: higher frequencies mean higher connection speeds, but higher frequencies also have a shorter range and are more easily blocked by trees, walls, windows, etc. Some networks are built out faster than others or prefer higher or lower frequencies. All these factors mean that the quality of a 5G network can be highly variable; even the quality of the *same* network can vary highly by location.",
"You may confuse the G in 5G to be short for Gb/s or GHz as these terms are used in other technologies. But in cell phone terms the G stands for generation. 5G is a collection of different protocols and standards set to replace the 4th generation ones. The actual speed you get depends on a lot of factors such as the distance to the cell tower and the spare capacity of that tower.",
"5G refers to the technology they use- these are the 5th generation cell technologies. It's an important component of speed, but speed can also depend on a ton of other stuff, like the radio frequencies they use, how close you are to a cell, and how many other people are on a cell. For example, Verizon has spent a lot of time setting up high-frequency 5G. Using higher frequencies makes it much faster than using the same technology at lower frequencies, but the tradeoff is that it doesn't travel as far so they need way more towers to get good coverage. As a result, Verizon only has 5G coverage in and around cities. T-Mobile, on the other hand, has been focused on the lower frequency 5G. As a result, even though your phone is doing the same thing once it connects to the radio tower, T-Mobile has much broader 5G coverage while Verizon's got a faster connection if you manage to connect.",
"One factor is that 5G uses different frequencies of light (referred to as spectrum). The cell towers are a lot like a lighthouse where it's shining a really bright (but invisible to your eye) light. Different frequencies of light interact with physical objects in different ways. To some frequencies of light, a brick wall is like a glass wall and will just pass through it. Others will go right through you like a glass version of you. Glass would be opaque to some of them. Some can really only go through the open air, the moment anything solid gets in between it stops the signal (the light from the tower). In the US, spectrum is managed by basically selling it to different carriers. AT & T owns a range of frequencies part of the 5G standard. Verizon owns a different range. T-Mobile a different set. They generally interact with physical objects the same way but there will be differences. Some frequencies are better than others. This means that for places like cities the companies have to pay special attention to how their spectrum for 5G interacts with buildings and humans to correctly position their cell towers.",
"While 5G is suppose to be faster then 4G, the advantage 5G has is access to higher frequencies. Think of frequencies as highways. The lower the frequency the less lanes it has, but what isn't used to make the other lanes is used to make the highway longer. The cars on the highway is the data being sent to your phone. A 1 lane road 100 miles long (low frequency) can't support as many cars at once, so it takes longer for 100 cars to travel on it. As the frequency increases more lanes are added, increases how many cars can travel at once, but it also makes the road shorter. So while 100 cars can travel quicker, then can no longer travel as fast. 5G adds support for really high frequencies that cell phones never really used before. Think of it like a 100 lane highway. Now those 100 cars can go at the same time, but the road is now only one mile. The trip is done way quicker, but now you gotta be real close. Low band 5G will be faster then the 4G LTE already using those frequencies eventually (short answer on eventually, not enough lanes are being given to 5G to be noticeably faster in some cases), and high band 5G is unimaginably faster then anything your cell phone has ever done, but the frequency is so high, that if you can't physically see the cell tower you will not be able to take advantage of the speed."
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nvrhi2 | Why do GPUs perform better than expected at higher resolutions? | I've always wondered about this but never found a satisfying answer that I could understand. To put some context and clarity into the question, 3840x2160 is 4 times the pixels as 1920x1080 which means one would expect a GPU's performance to be quarter of what it was at 1080P for example dropping from 120 FPS to only 30 FPS at 4K. But what actually happens is that the performance drops to 35-50% of the original performance at 1080P instead of the expected 25%, the same thing happens at 1440P, why does this happen? and why does it improve generation over generation? Also why do "bigger" GPUs from the same architecture scale better to higher resolutions than "smaller" or cheaper dies despite having similar core configurations and the same architecture? For example, the 3080 scales better than the 3070 and the 2080 scales better than the 2070, etc. Additional Note : The only odd exception to that rule is the 1080 which actually scales worse than the 1070 and was the worst scaling card in the spreadsheet I made, I wonder why it behaves that way. | Technology | explainlikeimfive | {
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"Not all the computations done on the GPU is done per pixel. A lot of the computations are done per vertex. Since the scene have the same number of vertixes no matter if it is rendered in HD or 4K this part of the computation is the same. So you would expect that the performance of the actual rendering dropps as the resulotion decreases but not linearly with the number of pixels. That being said you can often get away with lowering your graphics settings when rendering in lower resolution which will lower the number of vertixes in the scene as not all the details will be visible. And this will cause the performance to increase to something more similar to the expected result.",
"Not everything is harder at higher resolutions. Subject to all the myriad ways developers might go about implementing these effects, here are some things that might be barely or unaffected by render resolution: * GPU-based physics calculations, including how water looks * streaming world assets (buildings, trees, etc) in and out of video memory * shadow and reflection calculations, and anything else that usually has its resolution set independently by a separate game setting When increasing the resolution by 4x, all the things that are resolution-dependent get 4x harder, but this isn't everything. As for why beefier GPUs do better, I'm not sure, but I assume it's because the resolution-dependent features end up eating more of the pie when you have less overall. There's also to consider that lower end cards may run into memory limitations at high resolutions, since cutting back on expensive VRAM is a significant part of getting reasonably priced entry level cards profitable.",
"There is a lot that happens before the GPU even begins thinking about pixels. It is doing all sorts of triangle transforms and what not and the pixel count only matters at the Rasterization step, the very final stage of the graphics pipeline."
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nvruuf | Why does the iOS keyboard periodically forget common words? | Technology | explainlikeimfive | {
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"I think it's less that it forgets it, and more that it values it's own damn suggestions more than what you're actually typing. It's one of the things I like least about iOS currently. Like, the autocorrects for curse words is one thing, but when it assumes one word because it's more common, it's infuriating."
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nvskdu | How do Proof of Stake (PoS) block chains not create a broken system where the people at the top hold all the power? | I’m definitely missing something really simple but in my understanding the point of crypto is to decentralise and move towards a fairer financial system. Does PoS not just reverse this and put all the power back in the hands of a few? | Technology | explainlikeimfive | {
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"I mean, there’s not much difference between Proof of Work and Proof of Stake. Big players that can have more “stake” could already do more “work”. Decentralization doesn’t mean that big players can’t exert influence. A 50% attack was always a concern with Bitcoin and cryptocurrency overall.",
"I don't think that has ever been more than a sales pitch for crypto. And yep, as far as I know you are right. It does. But I suspect the difference is not really that great. Until blockchain can be sustainably utilized on a large scale without being an energy and resouce drain of monumental proportions it will keep being a hybrid between a ponzi sceme and a bubble.",
"The idea of PoS is the same as PoW. You invest money in the thing, and in return you get some back. The difference between the two is where you invest your money. In PoS you invest it digitally, in PoW you invest physically with computer parts / electricity bills, etc. In other words, PoS works off of the same idea as PoW, people with a lot of money can invest that money to make more money, and the fear of that investment being worthless keeps them from messing up the blockchain. To get even more ELI5: In Proof of Stake, you put up a \"stake\" in the form of coins. If you do something bad, you lose your stake, but while you have your stake up, you earn a percentage every now and then. In Proof of Work, you buy a bunch of PC parts, and try to do a whole bunch of math faster than anyone else. If you do something bad, then all the work you just did will be wasted, which wastes money. In both the incentive is there to keep person from doing bad thing, and in both the more money you put in, the more you get out."
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nvta9v | How is the mobile phone signal different for each phone? | We always hear somebody say their phone has no signal. It's always confused me how some phones receive no signal yet there could be somebody right next to them with full connection and no signal interruption. I know the location, obstructions to cellular towers etc. are factors in limiting signal, but when both people are in the exact same spot what else is at play here? | Technology | explainlikeimfive | {
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"Two phones may be subscribed to different providers. One of the providers may have technical issues or just have a cell tower far away. Additionally, two phones may be from different manufacturers and have different sensitivity to low level signals."
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nvwl9a | how hard drives work. What in their design creates the “space” or capacity that each one has? | Technology | explainlikeimfive | {
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"A typical hard drive works by having a number of discrete magnetic switches on a spinning disk. These switches can be switched between 0 and 1 using a precise magnet - think about an old record player, where the vinyl disk is the hard drive disk, and the pin head is the magnet. It works like that. The head can move over each switch and determine its charge (reading it), or alter the charge of a specific switch (writing it). Charges are either positive, or negative, which we can assign as 1 and 0, thus allowing us to use binary encoding. To increase capacity, you need to increase the number of switches on the disk. You can do this by making a larger disk, or improving the technology so the switches are smaller. In modern systems, physical hard drives are getting replaced by solid state drives - this is because SSDs have less latency and quicker access time, can hold switches much more densely, and are more resistant to physical impacts since they don’t have moving parts. In an SSD, semiconductor cells are used in an integrated circuit to store data. These cells are organized into floating gates for flash memory - essentially, they are set so running the circuit provides information on which gates are open and which are not. Thus, for an SSD drive, like an HDD drive, the storage capacity is based on how small you can make those switches/gates, and how many you can fit on a certain area. Usually, this doubles every two years as it has since the 70’s."
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nvwnqw | How does stealth technology still work for aircraft? | Stealth tech was invented decades ago, and the premise is that it reduces a plane's radar signature to that of something very small - like a bird, or an insect. Ok. Fair enough. How come it still works? Wouldn't modern radars just be programmed to look for the hummingbird flying at 600 mph? | Technology | explainlikeimfive | {
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"The problem is sensitivity. How far away can a radar system detect a hummingbird? If it can't actually detect a hummingbird-sized object until pretty close (say 5 miles), then the stealth will have done its job. Modern air-to-air missiles and guided bombs can be launched from over 10 miles away from the target; so long as the stealth fighter can get close enough to launch, it has succeeded.",
"There is a constant battle between new radar tech and new stealth tech. The technology hasn't just been stagnant for 50 years.",
"The idea isn't to blend in with the birds. The idea is that you can't see hummingbirds from 100km, but maybe only from 3 or 4.",
"One of the problems is discrimination - ie trying to find the \"true\" signal from the background noise. You can always try to amplify a response to try to pick out something from a return signal but it ends up amplifying both the noise and the \"true\" signal. This is not a very simple problem to solve. Ultimately, there is a limit to the power emitted by a radar and a practical limit to how much amplification and filtering in the radio echo before it becomes swamped with noise. For example, if a radar tried to pick up objects the size of birds, then every bird flying will trigger a response leading to hundreds if not thousands of false signals.",
"Radar sweeps are FULL of clutter, false targets, ghosts, and noise. Once you have a small enough primary return you effectively blend into the background clutter and it's impossible to discriminate you from the other million little tiny random returns popping in and out. Radars try their best to filter out that sort of clutter, so you might just get caught in the filter and wiped away from the screen entirely. Radar operation is a lot more complicated and difficult than games portray."
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nvxa2y | why can't we just use some part of normal storage as RAM? | Technology | explainlikeimfive | {
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"We do. It's called swap space. It's a last resort because even an SSD is hundreds of times slower than RAM. A hard drive is a million times slower than RAM making the problem even worse. But honestly it's not needed as much in these days of fairly cheap gigabytes of RAM."
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nvxxpn | what differences does lossless audio have on the sound of music, specifically on Apple music? | With the new release of lossless audio on Apple music, I'm wondering what noticeable differences there is to the music you're listening to. Is there a benefit/advantage to listening to the lossless version of a song vs the other? Edit: are there any noticeable effects for casual music listeners with basic audio equipment like Apple brand headphones and such? | Technology | explainlikeimfive | {
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"The media itself is only half the equation. If you have your phone plugged into a cassette adapter in the shitty 2-channel 10-watt tinny radio of an 80s Dodge truck, you will reap zero benefit. Imagine it like hooking up a 4K BluRay player to one of those old CRT TVs that came in a big wooden cabinet. Lossless audio is for audiophiles/enthusiasts who have invested in equipment for a fuller listening experience, whether it's high-end headphones or a full-on proper home stereo system or a car with a nice Harman Kardon stereo in it. That's the places where you'll see some difference with lossless audio. If you don't have high-end equipment or have an obsession with audio quality you'll probably do just fine with the non-lossless that takes up less storage and less bandwidth."
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nvydbx | How much 5G cell tower radiation dissipates within 3 feet of antenna? "Read description" | I understand that radiation from 5G towers are not of danger to the average person, but rather workers exposed for long periods of time and close to antennas. But 5G towers have labels warning of not entering within 3 feet of such an apparatus. My question then being, how much radiation from a 5G antenna dissipates within 3 feet? | Technology | explainlikeimfive | {
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"Others have answered the power question, but I’d to emphasize that these transmitters are **non-ionizing** radiation. The only thing they can do is heat you up. They can’t cause cancer or mutate your DNA or anything else scary you could think of.",
"The most import thing regarding the workers is the simple fact that they don't work on the tower when the tower is powered on.",
"Just to add it’s not just 5G towers, any microwave link has the same issue. In the old days when we used to work on public buildings roof areas we had to do a course as at one of our client sites you could effectively cook yourself if you weren’t smart."
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nvzjjb | Why did thatched roofs not rot and collapse from the rain and damp? Or if they did rot, how frequently were they replaced? | Technology | explainlikeimfive | {
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"They did rot, but because of how they are layered on the roof, it sheds water pretty efficiently (that's how they didn't rot quickly, water shedding ability and tight layering protecting lower layers) and a well thatched roof in modern times can last 50 years before it's beyond use. Historically, at least in parts of England, a new layer of thatch was added to the aging/weathered layer and some houses have been found to have seven feet of thatch on them with the oldest layers being 500 years old.",
"Present tense, not past. Some of the thatched buildings in my village are 400+ years old and it’s not a particularly old village. Here most people get their thatch replaced every 25 years or so, but you can just get it spruced up a bit rather than replacing the whole lot at once.",
"The thatch was sometimes treated with linseed or flax oil. It dries to a waterproof hard coat. I was a roofer and my co-worker was from Poland told me this.",
"Thatched roofs use things like straw because they have an incredibly large C:N ratio. So the high carbon and low nitrogen make it slow decaying. Hence straw lasting so long"
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nwbsuc | Why do animated films take some much computer power to create but don't need hardly any to play as a movie? | Technology | explainlikeimfive | {
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"Simple answer is that it takes a lot of computing to imitate lighting and effects, but the result is a single frame that is tiny as far as computers are concerned.",
"Do you mean 3D animated films for example? It’s because in film format, all that is being done is replaying video frame by frame in 2D, as with any other video. When making the things in the film though, you need to actually be able to render the things in it via a computer and modeling software, place it accordingly, animate it, etc. In short, everything is fully rendered in its raw format in 3D prior to being turned into a film. A film is just a series of 2D images/frames consisting of what the people making a movie want you to see. A similar comparison would be taking a photo of something in real life. Without taking a picture, you could walk behind someone and see the back of their head, what is behind them, things quite far away and so on. If you take a picture of someone though, the camera did not take a picture of the back of their head and what is directly behind them and such. You only see what the person who took the picture decided you could see. The rest is not in the photo. It’s not being “rendered.” This logic is also used when it comes to streaming video games in order to play them rather than having the game’s files and such on your computer and being rendered by your graphics card. A service will have the game running on THEIR hardware which responds to your input. The gameplay is recorded and provided you have very good internet, since all that is happening is that you are being streamed video from a game playing on another computer, you don’t need a good graphics card to play that game. Just good enough internet to watch a stream of it, because all you are “rendering” is 2D video at whatever resolution. If you download a movie, you are not downloading all of the assets that were created via modeling software and such in order to play it back.",
"To render a frame, you simulate light randomly bouncing around a scene. You start with the light source, cast rays in all directions, and a few of them end up in the camera after bouncing around the scene(technically you can start at the camera and go backwards, which I believe is how most of the ray tracing renderers actually work, but still most of the rays you cast don't end up at a light source): . The longer you let it render, the more realistically it mimics real light. At the \"camera\" you just count how many of those light packets end up in each pixel, and that's what you record and play back. Basically, the same reason it's much cheaper to play a movie from film than it is to re-create the set and have the actors play it out for every performance. You don't have to re-do the hard work because you recorded what the result was."
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nwd5lz | the difference between the rockets of today and the rockets during the Apollo era? | Also, what has changed to make landing a rocket back on Earth doable as to before? Could it have been done with 70's technology? | Technology | explainlikeimfive | {
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"Technically, the rockets themselves are not baaaaasically that much different, but it's now possible to put light, efficient computers on these rockets to perform the necessary control work. Back in the day it was not an option to put a huge, heavy, expensive computer on a rocket when it was simply cheaper to let them burn up and crash.",
"The big changes have been to the fight computers and the engines. The computers of today are far faster and much smaller, and have the added benefit of things like GPS for targeting landings. As for the engines, landing requires at least one engine to relight. Until fairly recently, first stage engines may or may not even be capable of lighting a second time. Even the Shuttle main engines, which were reusable, required extensive drying between firings. The Falcon 9 landing sequence requires the center Merlin engine to light 3-4 times in a matter of minutes, and be able to handle the heat of reentry as it does it. Starship is even more taxing, as the Raptors are also running what appears to be the most advanced gimbal program ever made.",
"I mean all the basic principles are the same, just some things are improved. It's kind of like the difference between a car from the 60's and a car made this year. Now we have lightweight composite materials, better computers for guidance systems, improved engines, some new welding techniques, and better computers for designing rockets and testing those designs, but a rocket is pretty much always a rocket. There's a reason the SLS looks pretty much like the Saturn V. The only major new thing since then is methane fueled engines, but even those engines still operate on the same principles and have the same parts. And sure, there's no reason why landing the 1st stage of a rocket from the 1960's couldn't be done, it would just have required a huge, heavy, expensive guidance computer and it wasn't worth the effort."
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nwi644 | How are synthesised voices (Alexa, Siri etc) made? | I’m assuming there needs to be a baseline with some voice actor, but with such a *huge* database of vocals and responses...how are ‘AI’ voices actually produced? | Technology | explainlikeimfive | {
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"There are several ways this is done. I worked in a commercial system in the early 2000s but not a whole lot has changed since then. Your idea is one of the more popular ways of producing natural sounding speech. A large amount of audio is recorded by a single speaker, and then chopped up into tiny bits and then put back together in different combinations. Older systems like this would use full phonemes (the basic sounds of speech) like the “s” sound combined with the “e” sound to make the word “see”. This was unnatural because there’s always some mismatch at the start and end of the sounds. By cutting the recordings into smaller pieces the speech can be made more natural sounding when it is put back together. This process of cutting up the recordings takes a lot of time although it can be sped up by using machine learning and speech recognition techniques with some human intervention. We needed about 6 hours of quality recordings including all possible sound combinations multiple times to make a new voice. Less than that would work but 6-12 hours would give the best results. There are other ways of producing speech that involve mathematical models of the human speech system. This is how some of the earliest computer speech was produced in the 70s and 80s, but it is less natural sounding (like the speech synthesizer that Stephen Hawking used) Finally more recently there are AI/machine learning generated voices that use neural networks or other “deep learning” techniques to generate the speech sounds. All of these techniques can be combined to make very good sounding voices these days. When I was doing work in this area some of the biggest challenges were around making the tone and cadence of the voices more human-like. We are still not all the way there but I am really impressed by the progress that has been made even in the past few years.",
"My mum has got ALS and as she’s losing her speech we recently digitised her voice so she can talk through that in the future. All she had to do was record 60 sentences with a budget microphone, send it off and a few days later they sent back her digital voice file and now when she typed anything it talks like her.",
"I saw an article some years ago who interviewed the woman who provided the voice for Siri, and she said that at the time she didn't even know it was going to be for an AI, and that they basically just had her make a lot of sort of \"nonsense\" noises that were pretty much broken down words/syllables. Because there was so much she did it for a while I'm pretty sure.",
"I worked at Google. Actually helped with Google assistant's voice (provided some voice clips for fun). What they do is hire a voice actress, and basically get them to read the dictionary several times with differnt inflections for each word. My meager addition was just an hour of reading random phrases so that the AI can help mix in non professional inflections into the mix so she doesn't sound so computerized. Ultimately that project was scrapped because the research shows that people like computerized voices. Anyway, now that you have a huge database with all words and different inflections, you feed a few billion hours of captioned audio to a machine learning algorithm, which processes each phrase and learns the right inflections on how to pronounce each word given its position and context in the sentence. Then, all you have to do is give this AI a sentence and it'll spit out the right inflectioned words 99% of the time. That's the majority of it, there are algorithms for constructing words that aren't in the database but the accuracy is something like 90-95% rather than 99.5% so they don't use that."
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nwkwy9 | How do heat-seeking missiles work? do they work exactly like in the movies? | Technology | explainlikeimfive | {
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"Early ones were really simplistic and just pointed the missile to the hottest thing it sensor could detect, be that a planes exhaust, the sun or flares (decoys). They had limited steering ability and only worked when shot at a plane from behind it (called \"rear-aspect\"), and even then weren't that reliable. Modern ones are much much more sophisticated. They have high-resolution infrared cameras, can detect and track planes from all angles, ignore flares, plot efficient intercept courses, are much more manouvrable and fully integrated into the planes targeting systems. A modern AIM-9X for example can be given targeting data from the planes radar or helmet mounted sight prior to launch and can track a target up to 90° to the sides (of boresight), allowing pilots to shoot at targets without having to point their own planes nose even close to it.",
"One thing usually gotten wrong in movies is that most missiles, including many if not all heatseekers, have a rocket engine that burns only for the first few seconds of flight. Hence, kinetic energy of the missile starts getting lower once the engine shuts off, and the missile is less maneuverable and therefore has a lower chance of hitting a maneuvering target at longer range. Therefore, maximum range and maximum effective range can be quite different. Some missiles do have sustainer rocket engines to maintain propulsion over a longer period of flight but I can't think of any heatseeker missiles with sustainerers.",
"When in doubt, assume the movies are portraying everything incorrectly. In this case, the big difference between the movies and real life is that missiles are wildly faster than planes. The classic visual of a pilot frantically dodging while a missile follows just on their tail is nonsense.",
"I still haven't seen an explanation of the \"heat-seeking\" logic of the problem that I really like so here's my attempt. Starting with the old IR (infrared) missiles it's fairly simple. If you take an IR camera and point it at the back of an engine it there will be a very obvious hot spot. ( URL_0 ). Because the difference in temperature between the engine/its exhaust and the environment is so large its easy to identify that as a targeting point. That is why the earliest missiles could only be fired from directly behind the target where they could see directly into the engine where the largest temperature difference would be. Then versions were made where they could detect the difference using just the exhaust instead of the engine core which greatly expanded the angles they were usable from, but still weren't effective if the exhaust was out of line of sight. Flares exploit the simplistic nature of this temperature difference logic by creating a larger temperature difference so the missile tracks them instead. To combat this engineers changed what the IR camera is looking at essentially. With better sensor technology the missiles no longer look at just what is the brightest thing in the field of view, instead they look for airframe heating. As a plane flys it encounters air resistance which is essentially friction between the plane and the air. That friction heats up the plane (this is part of why the fastes aircraft require special materials). The temperature difference between the friction heated aircraft and the rest of the sky is measurable but still fairly small. There can certainly be other things in the missiles field of view that have a larger temperature difference, so the missile has to know what it's looking for. To solve this these missiles have a form of image recognition built into their computers so that they can recognize aircraft shaped temperature differences and target those specifically. That makes it much harder for flares to fool these missiles while also allowing the guidance computers do a better job figuring out where the target is going so the missile can get there first. Others have covered this in other ways but \"Do they work exactly like in the movies?\" No. If a missile goes past a target will it turn around to try again? No, at that point it has been defeated. Will a missile chase for over a minute while right behind a plane very slowly getting closer? No, most missiles travel far faster than the aircraft they're targeting and aren't going to slow down to give you time to think. Can you out maneuver a missile? Yes... But it's very very rare and will usually leave you in a very vulnerable position to the next missile. There are methods to reliably defeat missiles, but that isn't one usually.",
"Historically they have been pretty simple, The first ones didn't track at all and just exploded when they got near something hotter than the empty sky, then the seeking ones were invented long before computers so they were just a rocket that had a ring of infrared sensors around the nose that would turn the rocket vaguely towards whatever was hottest. And they didn't really fly around chasing things as much as they would sort of vaguely auto correct a shot that went near a plane to a shot that hit the plane. Now that computers are a thing and missiles cost hundreds of thousands of dollars, they do act more like cartoon missiles where they can fly around chasing things all over. The line between missile and drone gets smaller by the day.",
"The missile knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it can obtain a difference or deviation. The guidance subsystem uses deviations to generate corrective commands to drive the missile from a position where it is in to a position where it wasn't. And, arriving at a position where it wasn't, it now is.",
"As Scott O’Grady pointed out, they are much, much faster than depicted in movies. Like no time to react at all fast and one nailed him brought the plane down.",
"The robot eyeball sees a hot thing and is all like \"ah that's hot\" and then gets the extreme desire to kill the thing",
"Video cameras are sensitive to infrared (heat radiation) as are with light. You point a camera forward, without infrared filter, and feed the video to a calculator. Any time the heat source is not in center, the calculator steer the missile until it is centered again. The result is the missile chases heat. The tech behind better “cameras” and navigation calculator/computer/AI is what makes modern missiles able to see further, and being distracted less by flares. Another difference is that you can have a camera that looks around like a human eye allowing the missile to lock and track targets on very extreme angles. Depends by the movie. The computer searches an amount of heat and its “frequency” on specific ranges. A missile computer will not chase the sun (too hot) or a little fire (too dim), it will not chase a flare if it doesn’t match the same target frequency (what in lightwaves we call color, exist also in infrared). Each heat source has specific frequency range, think about red orange and yellow fire. Very early missiles were simpler and easier to fool.",
"So not sure if this analogy works but. Let's say you're in the dark trying to find a friend. Say your friend shines a torchlight around you. You fix your eyes on the torchlight and walk towards the person until you reach him. In this case, your eyes are the infrared sensor in the missile's nose and the torchlight is a heat source (and aircraft engine/afterburner). You/sensor lock onto the torch/heatsource and guide to the target. Now that was just one heat source. In reality there are a lot more background sources of heat (the sun, heat decoys/flares countermeasures). Which can confuse you. So if another friend wants to trick you into guiding to him in the dark. He just shines another torch which might make you walk to him instead. Modern heat seekers like the Aim-9X/Python 5 are designed to be able to somewhat distinguish between decoys and the actual target heat source. Hope this helped!",
"\"Heat Seeking Missiles\" is an antiquated term. These missiles were designed in the 70-80's to follow certain heat signatures given off by afterburners and destroy something above a certain temperature. This was when 8 bytes was a lot of experimental software with no direction or backing. Movies make all of this look way more sophisticated than it is/was. [Chaff]( URL_0 ) wouldn't be an adequate deterrent if this was as smart as Bond films make it out to be. Newer tech within 5th gen fighters and drones basically make this worthless for future air battles unless they can detect missiles from much further away than current abilities."
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nwpz4b | Why do software installation or updates always go very fast up to 90% complete, then the last 5-10% takes so much longer? | Technology | explainlikeimfive | {
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"You shouldn't really listen to anyone here. The answer is that it's implementation dependent. Maybe the engineer wrote it so that there are four steps of 25% each. Copying files is maybe step 1 and is super fast. Step 2 is a big database operation and is slow... etc. Maybe the steps are totally fake. Maybe there is a simple timer that moves the progress up 10% every second until 99% where the last percent is actually dependent on something. Its completely unique to the person who programmed it or a commonly used installation software.",
"Basically, the computer has no idea how long it's going to take. It knows there is X number of steps and how far a long It is for each individual step and its going to try and predict how long it's going to take based on the information it been given by the dev inatally. There might also be a psychological explanation as well but I'm not sure Edit: [tom Scott explains it so much better]( URL_0 )",
"That first 90% is you dumping a moving box all over the floor The last 10% is putting everything away nice and neat",
"I've actually developed loading bars for applications before. 99 times out of 100 a loading bar is set by dividing the number of tasks to accomplish by the number of tasks already accomplished. Rarely is there any consideration to the length of time it takes to do a task. If there is, it's a best guess. Not many people want to pay for time studies to get it to be a realistic loading bar. They just want a notification of progress so they don't think the application is frozen. Just for kicks and giggles. I have done a time study on an application loading and normalized the loading bar to be fairly accurate as a countdown. On the computer I was developing with. I transferred the application to a user's computer and it was way off. (Maybe my HD was fast or slower than the user's, or their network connection was flaky. Who knows. There's a million reasons). Not saying you can't figure it out, but no one is going to pay a developer to do it.",
"The progress bar is nothing but a guesstimate. So the first 90% is guessing, the last 10% is the installer realising it is way off.",
"TL;DR Most software \"loading\" bars are fake. Meaning they don't actually show the precise percent of the progress. It's a guesstimate! Source: Me! A manager in software testing with just over 10 years of experience",
"Computer aphorism: The first 99% of the install takes 99% of the time. The last 1% takes the other 99%.",
"It's not a linear process but to make things \"user friendly\" interfaces are made with an assumption that things indeed are linear. The code that shows you \"% done\" only knows about the tasks that need to be done, not how long each task will take. So if the early tasks are very simple tasks, but the latter tasks are very complex tasks, it will appear to slow down as you see a % done being calculated.",
"Think like you're carrying a box with lots of toys in it. You need to take it from the living room to your room and place all them in the right spot. Someone decided 90% of the work just carrying the box, 10% is putting them on place. But carrying the box is quick, you can do it in a minute. Putting the toys in place takes a lot longer, maybe 4 minutes.",
"An accurate progress bar is difficult to code and are not critical so many are done as a last minute best effort. There are examples in the past of progress bars that were designed to go up to a set percentage over a period of time independent of the actual state of loading. Once the time was done, it would stay at that set percentage until everything was loaded. This caused a lot of frustration as computers became faster but these programs refused to start until at least 10 minutes went past. TLF5YO: Progress bars are hard to get right but as long as it is moving everything is going to be okay."
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nwrj84 | What is a register in computers? | I know when a program is running it uses registers to load and execute on data. However I keep hearing about hardware registers. Are there other kinds of registers outside of the CPU registers? May be registers that are available to other hardware modules or shared between hardware modules? I am thoroughly confused. | Technology | explainlikeimfive | {
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"Registers are simply active data storage areas. Nothing particularly fancy about it. Registers are available in many types of ICs and come in many varieties. For example, you can have status registers, control registers, data registers etc. The reason to give them names is because the function of these registers have to be very carefully explained in the data sheet for the ICs and it is just convenient to give them a name. Registers are typically not shared (since they are implemented internal to an IC). Unless you are poking deep into the HW and chips (eg writing drivers etc), there is rarely any reason to interact with HW registers (and attempts to change register settings without knowing EXACTLY how they will change the function of the hardware is very unproductive) Go pick up a few data sheets of some simple control ICs and you can see how they explain register settings etc."
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nwukmi | what is HDR (High Dynamic Range) | I just don't get the technical explanation. It's not just a wider color gamut. It does something more/else but I just can't seem to understand it.. | Technology | explainlikeimfive | {
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"If a scene has bright stuff and dark stuff in it at the same time, it can be hard to photograph. If you use a slow shutter speed, so a lot of light reaches the camera, you'll get enough light to see detail in the dark areas, but you'll get too much light from the bright areas, so the bright stuff will just be solid white. If you use a fast shutter speed, letting only a little light in to the camera, you'll get a good detailed image of the bright stuff, but the dark areas will just be solid black. You can't really capture both the bright details and the dark details in the same image. HDR is like taking two images, one that captures the bright details and one that captures the dark details, and then merging them together. That way you get detail in both bright and dark areas in a single image.",
"It's not just about more colors. It's also higher contrast. Meaning, with proper HDR you can have very bright and very dark objects **in the same frame**, and be able to see more details in both extremes."
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nx0kky | why does it take "up to 10 days" to be removed from an email list if it is all electronic? | You'd think it be instant | Technology | explainlikeimfive | {
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"It is often instant. If they say it may take up to 10 days, it could be for different reasons. More legitimate reasons might be that emails are scheduled to send ahead of time, and their system doesn't edit the list of recipients for scheduled emails when someone is removed. Less legitimate reasons might be because the page where you remove yourself from the list has intentionally tricky wording, so people often check a box that's actually indicating they want to stay on the list thinking it will do the opposite. If they believe it won't take effect immediately, they won't notice the problem at first and may forget about it entirely.",
"Mass email Campaigns are usually scheduled 1-2 weeks in advance and are essentially locked on their sending list when they are first generated. This is just how most mass mailing systems work. So when you unsubscribe, it will prevent you from going on any newly created emails, but ones that are already locked to go will not remove you.",
"It may not be all electronic. We keep our list manually. Both subscribe and unsubscribe requests are handled by a live human being who somehow needs to sleep, eat, take vacation etc. it is a small list and there are few requests (five a week maybe) so there is little value in automation. The manual system is also a nice way to ensure more “enthusiastic” colleagues don’t have easy access to the list."
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nx1gzd | How do prosthetic hands of amputees who were born without, or lost their hands know which finger to move? | Technology | explainlikeimfive | {
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"It's two different cases. If you have a hand and lose it, you have all this neural hardware that no longer works. With the prosthetic it's a matter of transferring that structure to a new outlet. If you've never had one, then you have to build the ability from scratch. Either way, it's many weeks of difficult physical therapy, just like a baby learning to control its hand, lots and lots of reps are needed.",
"I'm over my head on this, but in a general sense the brain is plastic and universal enough to gradually make sense of new data. It was interesting to learn that the human brain can make sense of sonar or ultra violet rays if there was a peripheral device with a proper connection. It was originally thought that certain areas of the brain controlled certain peripherals. Yet research has shown that if a brain is damaged another part of the brain can learn to control the area. Again, I'm only relaying what I have read. I like your question.",
"Not really an answer, but I've seen a video of an experiment where they attached a 6th finger (it was a second thumb I think, on the other side of the hand) to peoples hands and taught them how to use it. Despite never having 6 fingers on any hand, people were quickly adapting to it and were even finding new applications for such an extension. I would assume it's the same for amputees, even those who never had a limb. Brain is an amazing thing man."
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nx7h02 | How does headphone impedance work? Are harder to drive headphones objectively better? | A lot of premium headphones require a lot of amplification to be heard, and I don't get why that's the case when many other headphones sound great even though they have low impedance and can be driven by something like a phone. | Technology | explainlikeimfive | {
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"High impedance headphones were designed for recording studios where a bunch of people would have their headphones plugged into one source. The headphones were designed with high impedance so it wouldn't overload the amplifiers. Because they were designed for recording studios they were by nature higher quality. Audiophiles started using them for home use because they were higher quality. There really isn't any reason why low impedance headphones can't match the quality of a high impedance headphone.",
"\"Hard to drive\" does not really describe the role of impedance accurately. What impedance says is \"how much of the power is in the voltage, how much is in the current\". Low impedance means you can drive a lot of power with relatively small voltages, which is why low-impedance headphones work more readily with the audio outputs in computers and portable devices, which rarely deal with voltages higher than 5 volts, and frequently less than that (yes, computers have +12V lines, but they are used mostly for motors and to convert to voltages of less than 3.3V in VRMs), whereas high-impedance headphones need a specialized amplifier that can do higher voltages to get appreciable levels. Since cables are in series, any power lost in the cable is proportional to the current squared, so high-current loads are more likely to need beefy, low-loss cables. That is why even low-impedance headphones tend to have a higher impedance (usually along the lines of 32 ohms) compared to 4-ohm or 8-ohm speakers. You can use beefy wires for the speakers, but with headphones, wire weight may be a concern for usability, so it makes sense to shift the load more towards voltage; especially if you are using a headphone amplifier - if not, you are limited by the source's max voltage again. Finally, the impedance of no headphones being connected is essentially infinite. Most amps control voltage, so the higher the impedance (and the lower the current draw, accordingly), the less the headphones can interfere with the amplifier's behavior, which is important in the situations /u/empty_coffeepot mentioned."
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nxakb8 | What exactly happens when a WiFi router stops working and needs to be restarted to give you internet connection again? | Technology | explainlikeimfive | {
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"Routers are essentially tiny, low-power computers. They have their own operating system in there and everything. When the OS is first started, it's in a 'clean' state where everything is configured and working properly. All the services are in place, all the connections are set up, everything is green. As the OS works, over time it might encounter problems. There might be errors. Some of those can be easily recovered from, some not. Some of them don't cause any problems, some of them interfere with the router's function, slowing it down or outright preventing it from doing its thing. Restarting the router returns the OS to that initial clean state where everything is working again.",
"It’s been a few years since a tech friend explained it to me. Iirc, he said something like when you power off/ unplug the device (most devices that use computer chips for that matter), it ‘drops’ everything it was doing. Essentially all the electrical signals flying around cease to be; including the ones responsible for whatever corruption is occurring. When you power on/ plug in, it’s like a hard reset. Again, it’s been a few years since and I’m certain there are much more knowledgeable folks lurking who will be happy to correct me but that’s the gist of what my non-tech-savvy brain could retain.",
"Answer: Imagine a router to be like a post office. And data like the mail going through it. One day, a particular large/deformed/mispositioned mail got stuck on the conveyor belt and blocks the entire operation of things from going on. And the post office has no idea how to take that mail out of the queue. So everything gets stuck. Restarting the router is like clearing out the entire room, people, mail and everything, and running a super strong air blower to poof every mail, stuck or not, out of the post office. Then the people come back in to work and mail het processed again without a care of whatever happened before the restart.",
"Long time embedded software engineer in telecom here. As many have discussed, these routers will have a small computer inside them. Actually, many have two or three separate computers, for example a CPU for the cable mode, a CPU for the Wi-Fi, and a CPU for the overall router function. If \\*any\\* of these CPUs get into a snit, the overall function can fail. Also the CPUs talk to each other, and if the communication between the CPUs (that you can't see) fails, then the device function will fail. Most of these CPUs will be running Linux, but some will run obscure operating systems you've never heard of. None of them are running Windows. The most common issue is just plain buggy software. Even if we are talking about Linux, it may be using a very old kernel, old libraries, obscure libraries, etc. The manufacturers go cheap on these things, and once it \"works\" there is a tendency never to upgrade anything again. One more issue can be chipset compatibility between the router's Wi-Fi radio and the clients. This is especially bad for brand new versions of the standard (Wi-Fi 6) but can happen on older versions too. So the problem here is just too many cheaply made moving parts. You have multiple CPUs talking to each other, one of the CPUs talking to your ISP, one of the CPUs controlling the Wi-Fi radio hardware ... and everything potentially running an ancient unsupported version of Linux. This is why most pros in the industry don't use these low cost integrated devices at all but instead use a solution like Ubiquiti Unifi. (Which has its own set of problems, see r/Unifi). One more thing: there is lots of discussion of accumulated Wi-Fi errors (FEC errors). I am not aware of any process where accumulated FEC errors would lead to failure. Wi-Fi is designed to gracefully handle stations drifting in and out of range or hanging around on the fringe, this in itself shouldn't be an issue.",
"One issue is down to memory leaks. When you write some program, such as the OS on a router, it needs to keep track of info (variables) such as a list of IP Addresses, list of connections etc. Each of those variables need to take up space in memory. & #x200B; What should happen is that when a variable is no longer required it is removed from memory thus freeing up memory to be used for other variables. The problem is if the program is poorly coded or has a bug then sometimes things don't always end up getting cleaned up and over time you run out of memory - either causing some sort of crash or making things run very slow. Restarting the device will clear the memory completely and remove all the junk in there.. **ELI5:** Memory is like a jar you add marbles (data to be stored) to. What should happen is any marbles (data) no longer needed are removed but this doesn't always happen and eventually the jar overflows (crashes) and the only solution is to completely empty the jar by restarting your router.",
"The real reason why you have to restart a router is that no-one from the designer to the knowledgeable friend who can help you troubleshoot issues want to spend any time on the thousands of issues which might be the root cause of your error, when a very quick and simple fix is \"restart the router\". It's easy, it's quick, it gets the job done. All the reasons given in other answers are just possibilities in a sea of possibilities. A router is a cheap computer, it has all the bug potential of a computer with all the fragility associated with cheap hardware.",
"For me it was NAT table overloading from trying to connect to too many P2P peers on a crappy modem, spent some money on a decent one and haven’t restarted in over a year",
"ELI5: Start counting at 1 and don’t stop. Keep going past 1000. 10,000. 1,000,000. Now pretend you lost count eventually. You don’t know where you were, so you have to start over. A router does the same thing, only it keeps trying to remember where it lost count, so you have to restart it to tell it to start at the beginning again.",
"Someone has written bad software. Restarting the router causes the shitty software to restart and will then run again for a while. If you buy a good router/modem it will not need to be restarted until it breaks. Here you can see the uptime of my router. And it's not 1 year 2 months because I had to restart it. It's 1 year 2 months because I moved apartments. URL_0 // Master of Engineering Computer Science ( I have distanced myself from scientific language and nowadays instead go with the word \"shitty\" a lot)",
"There can be many reasons for why a wifi router stops working. It can be due to a sudden change in the power current, it can be due to overheating and it can be due to random faults or bugs. Basically restarting a router makes it stop whatever it's doing, take a step back and try again from the beginning.",
"Many WiFi routers are underspec. The piddling couple megs of ram, and the same chip from 20 years ago running brand new software. In one case, the power supply died due to brownout. Couldn't power the transmitter. In another case, I think the chip couldn't handle the overhead of a firewall, and spontaneously died",
"Pay attention to those that tell you that it's cleaning cache, flushing stuff such as DHCP leases, etc., maybe even cooling a little. But the horrible, eldritch and cosmic truth is that the great ones are running their tentacle-ish fingers through your house, in another dimension, disrupting the signal. Because those little bastards, no matter when, where, how or how expensive they are, sooner or later they will fail. PS: Use CAT6 cable. It is Cthulhu-proof.",
"The router has sort of handshake protocols between the isp site and your PC. Sometimes one side has a glitch and is left hanging. Power of closes all protocols and restarts new ones. Hope that is simple enough.",
"Software dev here, but here's how I understand it. Imagine you're having trouble trying to understand a problem in an exam or on a project. Is it not better to take a step back and start again rather than going round in endleas circles and crash your brain?",
"More often than not its a cache issue, basically your router has a pretty shitty little brain that fills up quick, sometimes it's hummdrumming along, and a request comes from a device and your router goes \"um, I'm sorry... What??\" turn off turn back on and your router is all like \"oh yeah, I was routing... Silly me\" Other times it's a dns resolver issue where you're actually connected but for some reason your router can't find the dude he usually asks for directions on the Web, and just sort of gives up. A thousand moving parts, a thousand reasons why.",
"the modem is usually what needs to be reset, when you have a mis-configured connection the easiest way to get it resolved is to unplug it for then plug it back in. this will allow the modem to restart its setup and perform all the checks that it needs to make sure you have upload and download functioning properly. the modem will send and receive some data packets to perform these tests and it will check the data for errors as well. if all is well it should successfully allow you to use the internet on your computer once again. & #x200B; If the internet was open to anyone with a modem device, a lot of these checks would be skipped because a lot of these checks have to do with whether or not the address is a paying customer or not. if you no longer have service and try to hook up your modem, it will simply reject all your attempts to connect.",
"The software running on routers often needs to store some information in memory to work. Might be a package of information coming in through the internet. Sometimes the program doesn't really know beforehand how much memory it will need to do that, e.g. this might depend on some dynamic input. So the software needs to find some free chunk of memory in it's hardware where this information fits, this is called dynamic memory allocation. Now what sometimes happens is that programmers forget to free that memory again. Even though it's actually not needed anymore, it's task is done, the program forgot to tell the system allocating the memory that this chunk is not needed anymore. If this happens often enough (e.g. after the router has been running for a few weeks) there won't be any more free memory in the hardware. So when the system tries to allocate some chunk of memory it needs it can't, there is no free, unused chunk left in the hardware anymore. It's all taken up by some old data which is technically not needed anymore, however was never cleaned up. So the router can't allocate the memory it needs to perform it's function, so it basically hangs or stops working. Now the memory we are talking about is not persistent, it's cleared after power off. This is fine, the router doesn't (and shouldn't) remember old internet packages. So restarting the router resets the system to a known state and clears up all the unused garbage. The same can also happen with computers or smartphones. The only difference there is that every Programm there has its own chunk of memory, so you only need to close the program, not restart the whole device.",
"ISP tech here. Important note- router and modem are two different concepts. Most isp will provide you a gateway, usually including both those and an emta(landline service). A modem is the decoder, a \"(mo)dular (dem)odulator\" which translates rf, light, dsl broadband whatever you want from binary(just the raw signal being turned from 0 and 1 into usable data packets.) The router is kind of more like the brains or controller of your network. The router assigns local ips to your devices in the home as you only have one actual ip address through the modem. Meaning the router is what let's you hook up both the Amazon alexa, smart TV, and Xbox at once. A modem would only let you have 1 thing because it doesn't route traffic- only blasts it out at full speed. Heres the eli5 on that: Think of a water irrigation system for sprinklers. The conduit in which the water comes from is the modem, and all the pipes leading to individual sprinkles are the router. Only this time its wireless water. So as for your question- why do modems and routers time out? Well it gets tricky and tbh I don't think any of this is simple enough for an eli5 but here goes. When your internet service cuts out its either the router or the modem. But 99/100 times its a service issue with the modem. With fiber to coaxial (copper antennae) the field which im most familiar with, there are 2 important signals types, your transmit (up) and recieve(down). Normally when a modem \"times out\" meaning going down and no longer demodulating, its because somehow the transmit was affected. This transmit can also be measured in the time It takes for the modem to communicate back with a central hub system, cmts is what we call it. When your transmit is too high, which is worse than low(exclusions apply), and takes too long to communicate back you can get a timeout. There are also multiple transmit carriers, and while the modem can function on just one, it usually comes with a plethora of issues. On a side note, the downstream is your raw bandwidth capability and brevity of it. Here the best eli5, and if anyone's interested for more pm me- Think of it like the CMTS, central hub, is at the end of a long highway. And the modem is one of the many cars on the highway. Lets say this highway has 4 lanes(your transmit carriers). Lets say traffic is bumper to bumper but everyone is going the same speed lets say 50km/ph. Everytime a lane of traffic is blocked off, or closed, (your carriers being impaired or unusable) all the traffic in that lane has to squeeze into other lanes, therefore slowing everyone down, and some people get run off the road. If the car takes to long to reach the central hub, it says I can't wait anymore, and sends it back to the start. When you restart your modem you are effectively unjamming the traffic and putting your car back on the road, but if a physical cable impairment still exists the lanes will still be blocked off. Maybe your car doesn't get run off the road this time, and makes it to the end, but its not guaranteed."
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nxf560 | Where do internet providers get the internet they're providing? | Technology | explainlikeimfive | {
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"The internet is a communication network, not a substance. I blame all the silly water analogies for making a lot of people thinking this. They don't get the internet anywhere, the collective interconnected ISPs and the computers connected to their networks *is* the internet.",
"Most people will connect through an ISP who is a Tier 3 provider. Tier 3 providers are buying capacity off of Tier 2 (for local) and Tier 1 (for international) providers. They can run there own data center which will include the hosting for their email servers and websites but many ISPs are outsourcing even that nowadays. Tier 2 networks will have peering (i.e. free) or interconnect (i.e. cross payments) agreements with other networks within the country to provide access to what is essentially the local internet. Tier 1 networks will interface with the international data cables. So essentially if you are setting up an ISP you need to have an agreement with a telecom provider to supply the last mile access to the client, agreement with a Tier 2 network for local bandwidth and Tier 1 for international.",
"It's more like, the internet is water, flowing between ponds and lakes and oceans along rivers, and the internet service provider is the company that builds the pipes to deliver that water to your house and pump sewage water out. In more technical terms, the \"Internet\" is just a bunch of computers storing data around the world and they are connected via cables and radio signals and the internet service provider is adding a line that connects you into that.",
"They put a bunch of computers in a room and connect them together. Then they connect their computer room to other computer rooms in different places. That allows them all to talk to each other so you can access information regardless of which computer room its stored in."
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