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7swi3g | Why is pausing a video represented by two vertical bars? | Technology | explainlikeimfive | {
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"It's probably derived from ceasura, a notation on music and poetry to pause. It's represented by double bars (||)",
"It all has to do with how tape moves past the tape head. Play is an arrow to the right because that's the direction the tape moves in order to play. Fast forward uses two arrows because the tape is moving faster. Reverse and rewind are similar, but in the opposite direction. Stop is a square because the tape isn't moving and is pulled away from the tape head. Pause is reminiscent of the capstan pins that hold the tape against the tape head."
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7sy7rq | Can AIs really learn things? | I've been watching videos about AI Technology, like the debate between Sophia and Han. The whole thing seems so odd and scary to me. Can AIs really learn things? How do they do this? Are the researchers just feeding them certain information and then saying specific phrases to trigger a response they programmed? How do we know it's not just some person typing in replies through a robotic voice? Here's a link to the debate if anyone hasn't seen it: URL_0 | Technology | explainlikeimfive | {
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"You may be interested in Alan Turing's landmark 1950 paper [*Computing Machinery and Intelligence]( URL_0 ). It is not technical and is readily accessible to the layman. In it, he introduces the concept of the famous Turing Test, but often overlooked is his treatment of various arguments about why machines cannot be intelligent. In it, he considers the arguments and points out none of them really draw a clear line between humans and machines, a most can be applied to humans as well. If you claim that computers are merely responding to input and thus not intelligence, you can make the exact same claim about humans.",
"Software developer here, I've written a couple AI in my time, most relevant to your interest being a neural net and a genetic algorithm. Though I am by no means an expert, I do have some cursory insight and knowledge. > The whole thing seems so odd and scary to me. Why? It's just software, not consciousness. While these are clever algorithms, they are nothing more than that. They can be used to put on an elaborate show, but they can't put on a show by themselves on their own accord; in the end they do have some very strict limitations, and they still will for some time. But even the idea of a crazy sentient AI that wants to wipe out the human race is absurd. One of the most fundamental properties of consciousness and life itself is an implicit imperative to survive. An AI cannot survive without humans. It exists in the virtual world and we exist in the physical, it is entirely dependent on us to maintain it's hardware and provide it electricity. If, in some wild Sci Fi alternate universe it is granted access to automate physical manufacturing and does eventually manage to develop the technology to be physically independent, it still has to overcome being massively outnumbered and against independent systems. It would be limited by bandwidth, protocol, and hardware - it would have to hack such a system like anyone else, and you can't hack a missile because the airforce doesn't share their WiFi password < /s > . The future of AI is going into specialized hardware. Google built a 1,000 node computing cluster to simulate the most sophisticated AI at the time, and some MIT guys managed to trump that on a single purpose built FPGA. CPUs and GPUs, even on super computers, really are no match whatsoever against a single purpose built processor. This also implies that AI, if ever it were to become sentient, can't just leech into every device conceivable and take it over, expanding it's consciousness. Most computing hardware fundamentally doesn't even work that way, and the rest of it just cannot support the computation requirements necessary. > Can AIs really learn things? In a very loose, liberal interpretation of what that word means, yes. We form memories by establishing connections between neurons in our brains, and strengthening those signal paths. Most neural nets have fixed paths, and just concentrate on path strength. The human brain has some 100 billion neurons, our AI neural nets have hundreds or thousands. And since they're not conscious or sentient, it really is just modeling a math equation. The way we use them, computation isn't performed except in response to input. So you feed in a picture, some numbers are multiplied and normalized, and the output is \"dog\". > How do they do this? A perceptron is a type of AI neuron. If you imagine a cell, it has a number of inputs (dendrites) and a number of outputs (axions) which are the inputs to other neurons. The output of a perceptron is *the sum* of a weight, w, times the input value x, per dendrite. So each input has it's own weight, you multiply the two together, add the results all up, and that's your output to any number of other neurons. Math. That's it. That's how simulated neurons work. The inputs would be, say the intensity of each of red, green, or blue, per pixel, of a picture. They learn by changing the value of the weight. The weight is the memory part of the perceptron. The weight changes as a function of the current weight and the value of the input. This is a bit of calculus called the Sigmoid function, though it's not the only one. If I recall correctly, since it's been years, I think the sum of all the weights = 1, so each weight will likely be fractional. So inputs with a huge weight are going to contribute more to the output sum than paths with a small weight. And the bigger the input value the greater the weight increases, and vice versa. > Are the researchers just feeding them certain information and then saying specific phrases to trigger a response they programmed? Most of the research is for image recognition, faces, objects, brand names, greater context... Like you can go beyond \"man\", \"dog\", \"ball\", \"grass\", you can write an algorithm that outputs \"man playing fetch in a park.\" You do this by setting up your AI, then feeding it input telling it \"this is a man playing ball in a park.\" The AI builds an impression of this in it's neural net, among its weights, so that it maps to that output. Other images that are similar will trigger the same mathematical relationship and hit the same output, or not. The AI may get an image wrong sometimes, but you can just tell it so, and it will impress that image as test data, conceptually \"I've been told this image maps to that output\". Of course, there's no thinking going on, it's just equations. > How do we know it's not just some person typing in replies through a robotic voice? You refer to the Turing Test. Can an AI fool a human? You can't be sure. We call the human behind the curtain a Mechanical Turk. If you can't tell the difference, does it matter?"
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7sydme | difference between game engine and render engine | How exactly can a game engine churn out 60 FPS while it might take something like eevee or lux up to multiple minutes to render. I get that the latter are more realistic, but does this really make that big of a difference? | Technology | explainlikeimfive | {
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"Imagine a simple room in a video game with a glass of water on table and a lamp on a desk on the other side of the room. The video game is going to show you the basics of what I just described. A fully rendered scene would show: * realistic shadows * realistic reflections in the glass * distortions of things behind the glass because of the glass and water * light bouncing off the glass from the table lamp would create a second light source and shadows from it * etc. None of those things are all that important to the gameplay and would make the game slow to a crawl. Yes, some games appear to have some of those features, but they are really \"faking it\" by taking shortcuts."
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7syi3j | How do smartphones know how to rotate correctly when "Auto-Rotate" is enabled? | It always interested me since I got my first smartphone years ago. | Technology | explainlikeimfive | {
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"There's a tiny weight suspended in springs inside your phone, it can measure where the weight is. This weight and measuring thingy is called an accelerometer, because it can only measure acceleration, gravity for example.",
"[This]( URL_0 ) is what they typically look like",
"They have an accelerometer in them. Basically, it measures acceleration. Your phone uses it to tell which way the ground is (it detects the acceleration caused by gravity) and your phone rotates the screen appropriately.",
"There's a device inside that uses a component with mass that gravity pulls on called an accelerometer. It measures the direction of gravitational force in three dimensions, as well as how strong that force is. So it can measure if you're walking as well as measuring which direction relative to the earth's core the face of the phone is pointing. The phone also has a magnetic compass built in, which helps when the phone is perfectly perpendicular to the gravitational force, but rotating on its x-axis. It doesn't always get it right however; the phone defaults to portrait mode, and only switches to landscape if the rotation/gravitational pull passes a predetermined threshold. Any other acceleration or working within strong magnetic fields will also confuse it."
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7syu8i | How do anti-virus scanners "quarantine" viruses to prevent them from working? | Technology | explainlikeimfive | {
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"Details depend on the individual anti-virus software. Quarantine sounds very fancy/advanced but most AV use very simple techniques to \"quarantine\" viruses. I'd say following steps will be sufficient to \"quarantine\" malware * Tell operating system to stop the malicious process * Move the infected file, e.g. an `.exe` to a \"safe\" location The safe location is just a directory where users don't normally go. AV might take additional steps to make the file unrunnable. A simple way would be to rename the file from `.exe` to `.exe.virus`. Windows uses filename extensions like `.exe` to determine what to do with a file. Changing that file extensions means, that Windows does not recognize the file as program anymore and will not attempt to run the virus. The important part here is, that all these measures are easily reversable. In case the AV has falsely flagged a legit file, the \"quarantined\" file can be quickly restored.",
"It just moves the file to somewhere where it won't be run automatically. Viruses aren't magic, they're just code. And that means they can't do anything by themselves. Someone needs to actually execute that code. Like any program on your computer, they do nothing *until you run the program*. Viruses typically work by placing or modifying files in specific locations where other applications will try to load and execute them. If an application is looking for \"RedBlimp.dll\", it will search certain directories, so if you place your virus there under that name, the application will load it and try to execute it. And so, if your AV scanner simply moves the file from wherever it is to \"c:\\blah\", then no applications will try to execute them, because that's not one of the directories applications search in. So the virus won't be executed, which means it'll have no effect."
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7syzst | When a clock is say, five minutes ahead of time and we reset it, why does it return to being five minutes ahead? | EDIT: To be more specific, I'm referring to how the clocks don't go further than that five minutes. I've had an analog clock in my kitchen that's ten minutes ahead for years and I gave up years ago resetting it because it always works its way back to being ten minutes ahead and remains there. | Technology | explainlikeimfive | {
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"The timing mechanisms(?) are off, so a minute or an hour on your clock is not the same as a minute or hour in real life, so gradually over time it begins to get further and further out of sync. Then someone notices it is out of time, resets it and the process starts again.",
"When a clock is \"off\" it's always off. But not in the context that it is always 5 minutes fast or what not. Rather, for each second that passes, it is measuring a bit more or less than a second. So even when you correct it, it begins to move out of sync again. Over time, the discrepancy widens, and at some point it is great enough that you notice and fix it.",
"Depends on the type of clock you're talking about. Mechanical watches that are hand wound slow down as the energy stored in the main spring is released. Same with automatic watches that self rewind as you move your hand. Plus these watches are mechanical devices, lubrication or lack of it changes the friction, possibly slowing down the watch, wear and tear and other factors can change the accuracy over time. As for quartz watches, similar issues, batteries wear out, quartz crystals used to keep time might not be built to the same standard (manufacturing variance), and probably other factors."
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7t096h | How can I run multiple programs simultaneously if I only have a single core processor? | I was browsing through some old computer specs, and this question just came up. How is it physically possible that one processor can do two or more things at once? | Technology | explainlikeimfive | {
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"Your OS is able to give each program a slice of time on the CPU, and stop it once that time has passed, to pass control to a new program. So every program shares that CPU with every other program, and also with the OS itself. Run more programs that need CPU, and everything will slow down. In reality a program may have multiple different tasks running at the same time - these are often called threads, and the OS gives each of these tasks a timeslice as well. The processor has, built into it, the appropriate machinery to allow the OS to suspend and resume different tasks.",
"It doesn't actually runs two things at once. Instead, it runs one program for a shirt time (like, 1 millisecond), then pauses to and switches to another program and runs that for a short time, etc etc. The actual implementation is a bit more complicated (for example each program actually has several threads which are like mini programs that also run \"concurrently\").",
"So it's actually running one thing at a time, but it's doing it so quickly you never notice. Imagine each program is like a guy waiting to get into a club so they can hang out with you. They're all standing in line, but there's only one bouncer to pat them down and check their ID before they can come in. If it takes 30 seconds per person, you can clearly see each person enter the club one after the other. But if it takes 0.001 seconds for the bouncer to pat down each person and let them in, as far as you can tell they all appeared in the club at the same time. That's what's happening with your programs. Your instant messenger can't get a new message until your browser finishes loading, but because the browser instructions take a fraction of a second, you never notice the wait. It gets even more exciting, because programmers have done some very tricky things over the years. To go back to my bar analogy, imagine that the first guy gets patted down and then can't find his wallet. Instead of the bouncer waiting there, the first guy steps aside so that the second guy can step forward. Then when guy #1 finds his wallet, he steps back into line and carries forward. The applications are written in such a way that they \"share\" the processor in as efficient a way as possible."
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7t0oc3 | How is money transferred digitally from bank to bank? | I feel like this is one of those questions where the solution is obvious, but you end up thinking about it wrong and are unable to come to the right conclusion. Maybe I’m just an idiot, but nobody else has been able to answer this for me. Okay, so you take cash and deposit it into your bank account. You buy something online and the seller lives thousands of miles away from you — maybe even in a country that doesn’t use your currency. What happens to the cash? It obviously can’t be transported to the receiver’s bank every times you make a purchase. How does the bank work out these kinds of transfers without accidentally creating money or losing it? | Technology | explainlikeimfive | {
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"There is a special network, called SWIFTnet, that connects the banks. The Society for Worldwide Interbank Financial Telecommunication (SWIFT) uses a standard protocol (ISO 9362) to identify each bank and transmit encrypted payment orders. Each bank is part of a collective that reconciles these orders each day. So if you spend $100 on some fine German product, your banks collective has an order to send that $100 to the German's bank. It tries to find a cancelling transaction, where some German bought $100 worth of US stuff. Then they can send your $100 to the German's seller and the German's euros to the company you bought stuff from. At the end of the day, if it can't match perfectly, some dollars have to be changed for euros on a currency exchange. Since that involves fees, the banks work to avoid it so they can make more money.",
"To add to u/WRSaunders's answer: > What happens to the cash? Transfers between banks generally don't rely on cash. In fact, most of the money in the world is electronic, with no physical bills or coins to represent it. This actually isn't a problem, since \"money\" is just an abstract token that we use to represent the value of things. In which case it doesn't really matter if that token is physical or not."
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7t1c7s | How does one prove that data (such as text Messages) recovered forensically is actually the data it is purported to be? | Specifically, when data is "recovered" forensically (which I understand) how does an individual (or group) present that data to someone and remove any doubt that the "data" wasn't just planted, made up, or otherwise fabricated to serve whatever purpose they need it to serve? What mechanism is in place to say, for example, that this "text message" was indeed recovered from the text messages on a phone after they were deleted. | Technology | explainlikeimfive | {
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"Like all evidence, any recovered electronics would follow a chain of custody - a legal document which records the sequence of custody of the piece of evidence. So long as the chain of custody is intact and the people on the chain are trustworthy, the evidence should be considered secure.",
"you place trust on each person thru the chain of evidence. from the collecting officer to the lab tech to the attorney. each person can fabricate evidence and place it into the chain...but rarely do they have a stake in the result of the case that makes the risk worth it."
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7t76y3 | What happens when a program is installed on a computer? | Technology | explainlikeimfive | {
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"Think of a program like hiring someone to work in your mansion. If it's your personal chef, they need to unpack their equipment (knives, pots, pans, etc.) so they can perform their function. These resources are indexed so the chef can remember where (what shelf) he put them so when it's needed he doesn't have to go rooting around boxes to find them. Once you've created a space for your program, other programs and dependencies know where and how to interact with your chef. Your operating system will oversee a series of handshakes with other programs to introduce the new comer and let the chef know what resources are available to him as part of the staff. The butler will tell your program when and how many to expect dinner, your chef will tell the wait staff the menu for dinner so they know how to set the table, etc. It's a complex process but that's the boiled down version el5 version.",
"For a piece of complex software to run, it may need many different pieces. For example: - Executable code (i.e. the actual machine instructions). - Other scripts that are not executable code. - Pictures, sounds, and such for the software's interface. - Localization/translation information. - User-modifiable configuration and preference files. - Internal caches or databases. - Documentation, example files, etc. - A place to keep user-originated files or documents. Depending on the operating system, there is a logical place for each of these pieces and a typical method of installing them. For a real example, take my favorite text editor, Sublime Text. It's available for Linux, Mac OS, and Windows, it has a *lot* of pieces: - Several distinct pieces of executable code, including the program itself, a complete Python runtime, a plugin host, and so on. - Icons, images, etc for the UI. - Dozens of built-in “packages” providing various text editing features, including Python scripts, configuration files, and much more. - A user-accessible directory for the user to put their own packages, plus a “User” package with the user's preference and configuration files. - Cache files with an opaque binary representation of some files from packages. Sublime Text is available for all major platforms, and it hews closely to the standard conventions for each. Broadly speaking, a working Sublime Text installation consists of two directories of files, one with the base functionality that only changes when you update the software (executable files, built-in packages, etc) and another directory with user-serviceable and temporary files (preferences, caches, etc). How these two directories are established depends on the platform: - On Windows, you install it by running an installer program that moves various pieces to their intended locations and registers the program with Windows in various ways (e.g. telling Windows where to look for the executable “entry point”, icon, etc). Generally, it will install the program directory into `/Program Files` and the user data directory into the Windows-standard location (`~/AppData/Roaming/Sublime Text 3`). - On Linux, you generally install it via a package manager, which is a kind of automated universal installer. I presume that the package manager does basically the same things as the Windows installer in this case. The locations of the installed directories will depend on your Linux distribution (because it's not Sublime Text that specifies that, but the package manager). - On the Mac OS, you just download the “Sublime Text.app” file to your Applications directory. This is a Mac-specific thing that deserves some explanation: the `.app` is really a *directory*, not a file, but when you double-click on it, the Mac OS looks for and runs an executable entry point at a standard location inside the .app. When you run Sublime Text for the first time, it will create a user data directory at the Mac-standard location (`~/Library/Application Support/Sublime Text 3`). (Note: In Windows and the Mac OS, Sublime Text is installed as a traditional desktop application, not through an “app store” or the like.) The best cases to contrast are Windows and the Mac OS. In both cases, you end up with an application directory full of non-user-serviceable bits. On Windows, this might be at `/Program Files/Sublime Text`; on the Mac OS, it will be at `/Applications/Sublime Text.app`. The key difference is that the Mac OS has the abstraction that a `.app` directory looks and behaves like a single file to casual inspection. This has a couple of benefits: - A novice user is very unlikely to peek inside the .app and open or install the wrong thing. There's no need for an installer, because manual installation (by dragging the `.app` to `/Applications`) is very easy to do right and fairly hard to do wrong. - There is no need to register the application metadata (icon, name, executable entry point, etc) with the Mac OS, because this information is listed in a standardized file at a standardized location within the .app (`*.app/Contents/Info.plist`). In addition, you (or the OS) can find all of the applications on your computer by finding all of the `.app` directories. Now, some Mac software *does* require installers, though it's pretty rare these days. The biggest offenders are Adobe and Microsoft, and their software is certainly widespread. Other cases where you'd need to run an installer are if you're installing some kind of general framework like Java that many other programs would want to use. --- Suppose you want to “install” a selection of plants for your garden. How you do this depends on what OS (hOrticulture System) you're running: - On Windows, you order a plant, and a gardener from the nursery comes by. They'll decide where to put the plant and where to store any supplies you need. Probably they won't dig up any of your other plants in the process. - On Linux, you have an expert personal gardener. You tell him you want a certain plant, and he'll find it, order it, figure out the right spot in your garden for that plant, plant it there, and store the extra supplies in the shed indexed by plant type. (If you want an exotic plant your gardener doesn't know about, you'll have to tell them where to get it first.) - On the Mac OS, there's no gardener. You order a plant and it's delivered to your front porch in a custom-made pot. You simply drop it into an empty spot in your garden and it's done. If you ever look in your shed, you'll see that it's stocked with supplies."
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7tbkee | When Windows first loads and everything is going extremely slowly for several minutes but task manager doesn't show anything taking up much CPU or RAM, what the hell is it doing? | Technology | explainlikeimfive | {
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"Look at your I/O (Disk usage), most of the time, that is what is slowing down your windows startup the most. That's why so many people buy SSDs, they are much faster than regular hard drives (but obviously more expensive)."
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7tci36 | How were wooden ships made waterproof in ancient times? | Technology | explainlikeimfive | {
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"Caulking such as horse hair, clay or cloth was poked between the wooden planks to fill gaps. Pitch or tar was applied to the outside to help waterproofing. Also boats then, like now, aren't water tight. The bilges would always collect some water. Bailers would use buckets to bail out the bilge water. Today this is done with pumps or stern hatches on some small dinghies/yachts.",
"Tree resin is an excellent waterproofing agent, and very helpful when binding wood together to create a boat. Sometimes they would use pitch and tar (a resin composite) instead, but resin was the preferred method for many cultures.",
"1. Make it out of a naturally water-resistant wood, like pine or cedar. 2. Shove bits of old rope and other similar materials between the boards. 3. Cover whatever you can in pitch or resin. 4. Still expect it to leak, and to spend an annoying chunk of your time bailing water out/repairing leaks.",
"Tar/pitch was also used; basically painting/caulking the hull until it kept out most of the water (though some would still get in 9/10 times). Also the whole ‘swabbing the deck’ thing wasn’t a big deal because it was dirty; it was a big deal because wet wood swells to a larger size than dry wood, and larger planks means less space between them, which means it’s less likely to let water in, should it get splashed suddenly",
"There were and are two main techniques of planking. Carvel is where you fit the two butted sides together with a good fit and as slight a distance between planks as you can and they lay flush upon the frames and present flush to the outside world. Then, depending usually on the size of the vessel, either cotton or oakum is driven in the whole length of that seam very very tightly packed. Once the boat hits water, the planks will swell and compress the cotton which is already in a narrow channel, and the seal will be waterproof. This may take a few hours to days depending on type and state/age of wood and cotton and also length of time out of the water. Lapstrake or clinker is what you see in Viking ships. The plank above lays over the edge of the plank below. They are both steam bent then carved to receive each other before being fastened together on the boat. They are fastened with rivets which, in the act of riveting, create further compression of the wood along the very accurate fit. A watertight seal. Both kinds have a rabbet carved into the keel and stem and sternpost (whole spine of the boat) with a complex bevel to receive the garboard (first plank), and cotton caulking along the seam of that rabbet exposed to the world. Pitch is often poured into the keel at the lowest point around the sternpost so that water which will inevitably get in, from seeping or over the gunwales, will find its way there by gravity but not rot the wood as is sits waiting to be bailed. Pitch can be applied many places and often is for degrees of repairs. Source - am boatbuilder.",
"How ancient? Techniques changed. A lot of it had to do with wood swelling. Fitting dry wood together then launching it pretty well kept things dry as the wood would swell when it got wet. Pitch was used sometimes. Sphagnum moss other times.",
"I'm not a boat builder, I believe it's mostly the result of tight fitting joints that can't move. If you fit two pieces of wood together with a smooth joint, and ensure they can't move, when water causes the wood to swell, they will not leak. I have a wooden chest with simple dovetail joints on the ends. It's in a building that was once flooded with 11\" of water after a storm. The blankets in the chest were dry when the water receded because the joints were tight to begin with, and when the wood got wet,they swelled, further tightening the joints. Also, remember the term \"bail\"? When your boat leaks, and they all do to some extent, you have to remove it.",
"I'm from Santa Barbara, CA and here the indigenous peope known as the Chumash used oil that would naturally seep out of the ground at beaches to caulk their canoes. The Chumash were a very sophisticated group, they lived on the Santa Barbara channel islands (~30 miles off shore). What I think is crazy though is that oil naturally seeps out of the beaches here, no wonder it was originally a hot spot for oil drilling.",
"I sailed on a wooden Gloucester fishing schooner called the [Spirit of Massachusetts]( URL_0 ) from Maine to Puerto Rico, for 4 months during the fall of 2008. When we encountered rough weather or major sea/air temperature changes the ship would leak like a sieve. If needed the watch officer would call to manually pump out the bilge. We would insert this metal rod into a pump port on the deck and by actuating the rod up and down manually drain the bilge. This could take anywhere from a few minuets to hours in rough weather. On one particularly rough and leaky leg of our journey, after arriving in port, we noticed that the high sea state had stripped almost all of the tar pitch out of the spacing between the planks on the deck. Repairing this involved cutting out the damaged tar, repacking the void with synthetic wadding, and then pouring new boiling hot pitch into the space to seal the deck. Doing the whole deck on a 136' ship was a major pain in the ass to say the least. You have no idea how much a wooden ship leaks in rough weather until you are on one. After one day of that you more or less give up any hope of ever getting dry. I remember on one occasion waking up in bed, wearing my full foul weather gear, watching streams of water run down the inner hull and just pooling in my bunk. It was a great experience and I loved every second of it, but i'll stick to flying and the comfort of my climate controlled flight deck.",
"Napoleonic era ships (and beyond, sailing ships) were never water tight, exactly. They had huge crews and capstans on deck to run pumps available 24/7 and the ship's carpenter (or whomever else) kept track of how much water was coming in at any given time. Once a few feet or so was in the bilge, they pumped. Often leakage was considered a good thing for keeping the bilge (where the water collected) \"sweet\" and for drowning rats. Even modern wooden sailboats are rarely (modern, meaning, planked vessels caulked with cotton) totally watertight. A certain amount of weeping is considered more or less par for the course. A traditional wooden boat is basically a basket of sticks with the gaps filled in with hammered-in cotton or oakum (frayed apart hemp rope) and fayed (covered over) with seam compound (in the old days, pine tar and white lead, or tar, etc). When the boat is built the planks are relatively dry when it's launched, then the planks swell and put a huge amount of force on the seams which strengthens the boat immensely.. The planks are supposed to touch on the inside edges, but the outer 2/3 or so of a plank is a shallow V-groove where the caulking goes. When the planks swell they put a fair bit of pressure on the caulking as well. However, all traditional wooden boats \"worked,\" ie, moved, under sail and while the caulk moved with the planks, eventually slow leaks happened. The older a wooden boat gets, generally the more it leaks until refastening/re-caulking/re-planking/re-framing is needed. Some cruder European ships in the very olden days I believe were totally covered with tar. Also small Irish boats called Curraghs were covered in animal skins and tar. Inuit kayaks are made of tightly stitched walrus skins that tighten like crazy when they get wet, and have to be kept wet or they dry out and/or rot. Boatbuilder here. Ps as somebody pointed out, past a certain point wooden hulls are not viable. They just can't be made stiff enough and \"hog\" (the ends fall, or the middle humps) and leak, and basically suck. With the invention of plywood, though, they were able to make big and very fast boats around WWII and after (PT boats were a kind of plywood--two plank layers on the bias with a waterproof membrane between) much lighter than the equivalent in a planked boat.",
"Not necessarily how they made the ships completely water tight but when they assemble the ship, they left slight gaps between the beams so that as the wood expands when it gets wet it creates s tight seal. Other wise the wood would split and break if packed tight together",
"Not the case for ships, but canoes: The native Americans would line the outside of the canoe with bark and form it to the ribs of the canoe. The bark would provide the waterproofing necessary, and they would keep the bark in form by \"stitching\" it to the body of the canoe. Source: URL_0",
"You sink a wooden boat and the water swells the wood and make its water tight . Source: am wooden boat",
"They used bitumen. Bitumen or pitch is a residue of distilled petroleum. The black top tar asphalt is composed mainly of bitumen, and has excellent water repelling properties.",
"Koreans used pine wood and the technique of interlocking joints that would swell when soaked and become stronger. Wooden nails were also used because iron would rust. Fun fact, they found remains of the ships that the Koreans built for the Mongols when they went to Japan and found that the Koreans had purposely done a crappy job. Not sure if you were interested in that part of the world but there it is",
"There's some kinds of wood like Teak which get stronger on absorbing water. It has been used to make boats in India. Also, balsa logs have sap in them which prevents water from being absorbed beyond a certain depth.",
"On an episode of Fixer Upper, they describe shou-sugi-ban which is a Japanese method of charring wood to make it resistant to mold, water, insects, etc. I don't know if they used it for boats though. In the episode they use it on a guy's house boat.",
"Paying tar on the bottom hold of the ship also helped to keep water out. This was probably the worst job on the ship since the bottom hold, or Hell as it was called, was a dank, foul smelling, hot place to labor. Hence the phase, \"you'll have Hell to pay\".",
"Wood swells a bit when wet. Some woods more than others. Selecting a wood that was buoyant when wet was important. On the inside of the ship, tar was usually used to seal up any cracks or holes that would form. This tar would have to be reapplied routinely or the ship would take on water.",
"Covered wagons of the mid-19th century borrowed the concept for boats but for keeping rain water out. In the Tommy Lee Jones movie The Homesman if you look carefully, when they procure the newly crafted wagon you can see the side paneling had descent gauge rope that was tiled through the boards. The wood and consequently the rope would expand during storms and keep water from accumulating inside. Probably not advantageous by today's standards but we are spoiled by comparison."
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7tea2j | What is the process behind film and video game remasters? | Is it just an easy cash cow where minimal work needs to be done or is there a complex/delicate process to it? | Technology | explainlikeimfive | {
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"The answer is: It depends, there is no general answer. * There are remasters or \"HD versions\" that are really low effort. Some just replace some textures, re-make some HUD-elements to work with modern resolutions/ratios and that was that. * On the other end of the spectrum are basically re-implementations of the original, with new textures, new orchestral audio, new (in times entirely) voice acting, technical recoding, new bugfixes, etc. The effort is still much lower than making a new game, as all design and art is there - just creating some new version of the art is easier than coming up with it in the first place - is there, a lot of the code can get reused etc etc, but still a lot of work goes into it. Most remasters are actually somewhere between these two extremes. Usually it's some technical adjustments for modern resultions, some re-doing of old images, textures, some new graphical effects, maybe a bit audio. Often the \"new\" version contains all patches, DLC/add-ons that have shown up, at times community work (patches, some mod-idea), maybe some fixes for old bugs (but no complete round of new bug fixing; priority is usually to get it to run \"at all\" on modern operating systems and that is mostly it). To answer the posed question: compared to creating a fully new game even doing a complex rework it is an easy cash cow. ;)",
"If it's a remaster, it's pretty close to completely re-implementing the entire game. Audio can usually be re-used, but that's about it. Art assets will need to be retouched to be compatible with the new engine, and potentially redone if it's been a while since the original. Scripts can likely be ported from the original. How intensive that will be depends on how different the new engine is to the old. So, in terms of cost, it's definitely cheaper than creating a new game from scratch, but it's also a lot more expensive than you'd probably expect."
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7tgaco | How do restaurants with trackers know where you sit with pinpoint precision? | I always wondered how those tracker badges with numbers worked. Not the ones that buzz and you pick up your food, but like in Panera for instance where a server finds your table and gives you your food after you ordered it at the front. It looks like they aren't looking around or anything, not like they wander, they come straight to my table knowing where I sat. Is it able to broadcast feet-accurate location? How does it work, if anyone has worked in a restaurant with those tracker badges? | Technology | explainlikeimfive | {
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"There is another device attached to the table that can tell it the table number through short range wireless (RFID). The system associates a tracker's ID with the order number. When the tracker is places on the table, it reads the table number from the RFID tags under the table and sends it to main device, along with the tracker's ID."
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7tmoh7 | The real-world problem Blockchain technology solves | Technology | explainlikeimfive | {
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"Transaction verification without a third-party. There are lots of transactions done in business/real estate/etc. that rely on cumbersome methods of verification, often involving manual effort by a person. Being able to skip that with something that's cryptographically trustworthy would be a plus. Think of a blockchain as a distributed ledger, that can be quickly verified by any party involved. There's lots of uses for that."
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7tmurb | How does transparent TV work? | I'm talking about something like this: URL_0 | Technology | explainlikeimfive | {
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"Short answer: The same as your black screen TV, just with transparent material instead of the black material. Less short: OLED displays have [a bit of space between the diodes]( URL_0 ) that make up the pixelsand while they need some of it for the circuits, there's still room there that can be made into glass. So if you were in person it would look shaded, but under heavy magnification you could see all of the black dots of the inert diodes. This is just the beginning. It's already possible to make flexible screens, and to make screens that don't light up. Imagine animated clothing. Imagine buying TV screens by the foot like fabric.",
"That TV is apparently using OLED technology. This is similar to an LCD screen, except it doesn't require a backlight, and therefore it doesn't require an opaque material to reflect and defuse the light from behind the screen. While LCDs work by filtering light passing through them, OLEDs generate their own light internally instead. OLED screens require two electrodes for each cell. Typically the front electrode is transparent, and the rear is opaque. There's no real technical reason this *has* to be true though, so I would assume they simply made both electrodes transparent. While I'm sure there's all kinds of very complex engineering that went into making the mechanism of the screen hidden from a typical viewing distance, there's no huge mystery about the basics of the technology."
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7tn1m1 | If a 3.5mm audio jack is also referred to as a 1/8" jack, why is a 1/4" audio jack also referred to as a 6.3mm jack? | Technology | explainlikeimfive | {
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"> [The outside diameter of the \"sleeve\" conductor is 1⁄4 inch (6.35 millimetres). The \"mini\" connector has a diameter of 3.5 mm (0.14 in)]( URL_0 ) The 1/4\" jack was defined as being a quarter inch because it's an old American invention dating back to the 19th century. Calling it a 6.3mm plug is an accurate conversion. The 3.5mm jack was invented much later and is defined as being 3.5mm. Calling it an \"1/8th inch\" connector is not terribly accurate but it conveys the idea that it's \"half\" of a quarter inch connector. Americans aren't really all that picky and, since nobody has to actually create phone plugs/jacks, it's not important for the common name to be accurate. It also rolls off the tongue better than a \"9/64ths connector\""
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7tn671 | if you listen to music on your phone, does the loudness make a difference in battery life, while using headphones or speakers on your phone? And if yes, is this a significant difference? | Technology | explainlikeimfive | {
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"Yes it makes a difference: louder music means more energy to produce it, and that's gotta come from somewhere. Unless your speakers are powered (can't tell by your question), that power comes from your phone. No, it's not a significant difference, in that your wireless connections (wifi, bluetooth, cell), screen (the screen is probably the biggest one), and processor consume much more. If you're using powered speakers, it's actually draining less of your battery than if you used the built-in speakers cranked up."
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7tnqyf | How come when you look at lights (I.e. phone, pc, tv) before you go to sleep it takes longer for you to fall asleep? | Technology | explainlikeimfive | {
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"The blue light messes with your melatonin levels and makes your body think it’s daytime and shouldn’t be sleeping- that’s why night-mode on most devices is a red-orange tint, rather than blue",
"As others have said, light (especially blue) suppresses your production of melatonin. Melatonin regulates sleep/wake cycles. Blue light filters/ melatonin supplements can help.",
"The human body and most other animals no doubt. Have what's calls a circadian rhythm. Otherwise known as your body clock. The body is great at using the level of light to determine it's actions. Think back to caveman days. A sleeping man is a easy target for prey. Most of our prey would be sleeping at night. Hunting at day. The human body uses light as a basic tool know when you sleep and when to get up. So by sitting in fake light. (Not sublight) from a bulb or tv or phone. It confuses the brain and it's melatonin levels. Causing you to think it's still lights so don't sleep. A top tip to getting to sleep is to just lie in a dark room with no phone or tv. Relax. And the brain is slowly know it's time to sleep. Blue light filters will help. But still it's best to remove light."
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7tq601 | How did the gun from the Nintendo game Duck Hunt work? | Technology | explainlikeimfive | {
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"IIRC the screen would flash every time you pulled the trigger. Based on reflective light bouncing off angled light gun, game could detect where on screen the gun was pointed.",
"URL_0 Basically the gun can sense if you're aimed at the right colors on the screen."
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7trxit | social engineering | Edit: in terms of computer science | Technology | explainlikeimfive | {
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"It's a euphemism for lying to and scamming people in order to bypass the security of a computer system (as opposed to finding exploits in the software that let you hack the system). When dealing with \"important\" systems, like on a corporate network, the *people* you give access to the system are the biggest weakness. All the firewalls and security in the world won't do any good if a sysadmin lets a stranger into the server room or somebody sweet talks the passwords out of users with elevated permissions.",
"For ELI5 I think this is best explained by example. I call up your company's help desk and tell them I'm a new employee and I need the host name for the VPN. They give it to me. I call up an administrative assistant and tell him that I'm from IT and there's a problem with her computer and I need her login and password to fix it. Now I know the VPN entrypoint akd I have login credentials to use it. I didn't have to use any specialized computer security knowledge or hacking, I just asked a couple of people for some information while lying about who I am. Works more often than you think."
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7tshkm | How is nuclear Fallout removed? | For example in places like Fukushima or Chernobyl, which have been (at least by official stations) "cleared" of Fallout and made inhabitable again, how exactly is the nuclear fallout and the radiation there removed? | Technology | explainlikeimfive | {
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"By removing whatever was contaminated. They usually go and remove some centimeters to meters of ground, put it in bags and then dispose these bags as radioactive waste (which means that there are warehouses and storage areas full of this shit that waits for science to find a solution of where and how that stuff can be finally deposited...)"
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7tstgo | OLED burn in. We know how it happens, but why does it happen? Do pixels fade away over time or what? | Technology | explainlikeimfive | {
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"Yes pretty much, over time (and over use) the pixels age and their properties degrade. As long as all pixels are getting roughly the same use, you will not notice this, but you are actually getting the same \"burn-in\" over the whole screen. It's not necessarily a \"fade away\" though, they will lose max capacity, so on white it will seem like they have faded, but the same pixels may show brighter on dark, so it's more like a loss of dynamic range then, how the burn-in presents itself can vary..",
"It's the biggest reason I won't buy an oled tv until they're the same price as lcd. Yes, the picture is way better... But I can live with an ok lcd picture if it lasts basically forever. The last thing I'm going to do is promote this new idea that it's ok to replace your electronics every few years.",
"Okay let me just start off by doing a simplified description of the difference between a traditional LCD screen and an OLED screen. In a LCD screen you have a single light that acts as a backlight and is similar to an old projector bulb. Over that is a filter layer that is able to obstruct certain wavelengths of the backlight at each pixel, this creates the image. This is why LCD black is considered bad, there's still light there the filter is just blocking as well as it can. OLEDs on the other hand instead is basically made of a tons of super tiny LED lights. So each pixel in an OLED display will have a red, green and blue led that can be turned on in various combinations to make the colors you need for each pixel. (I know pentile arrangement and all that but that's needless complication right now) So think of a LCD screen as a big white light box that we then put an arrangement of filters in front of to make a display. The OLED is more like arranging a bunch of christmas lights into a square to act as pixels and display things. So with the LCD if we want to display something like a circle, we would put clear filters in all the areas we wanted a circle and black filters around the outside to prevent light getting through. With the OLED we would turn on just the lights in the square grid that make up the shape of the circle and leave the others off. Now both can display the circle and they have their ups and downs with darkness ability and other aspects but of course what we are concerned with is the idea of burn in. Burn in comes, as we know, from things being in the same place on the screen. Say we had the christmas light grid and put the circle on it and left if there for a really long time. All the lights that were part of the circle will be constantly on and aging, which also means losing a bit of brightness. Eventually those lights will get worn a lot and will be far dimmer than brand new lights. The problem is that the lights that were outside the circle stayed off the entire time the circle was being shown. So the lights outside the circle are basically new and shine at full brightness, while the lights inside the circle have been on constantly and have gotten dim. As a result, if you now turn on all the lights at the same time, you will still see the circle but it will be made up of dim lights surrounded by brighter lights. Same thing with OLED displays."
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7tt7mg | Why is cell phone service non-existent in basements or certain buildings? | Why is it that most basements and some buildings have no good cell reception? | Technology | explainlikeimfive | {
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"text": [
"Concrete can block cellphone signals. It is thick/dense enough to stop cell phone frequency waves from passing through it."
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7ttkp2 | Why do the colors on your computer screen become distorted when you apply pressure to the screen? And what determines what color these distorted pixels turn to? | Technology | explainlikeimfive | {
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"You're using a liquid crystal display. This means that there's a sheet of liquid crystals in between a bunch of other screens and filters, and behind all of that is a light. When you apply an electrical charge to liquid crystals you can change their shape, and when that happens the direction and color of the light as it passes through can be changed. But you can also change the shape by pressing on them through the filters. Because this is much less precise than you can get with an electric current, it sort of warps into a blob of colors instead of a coherent image. When you remove pressure, the electrical current takes back control and forces the liquid crystals into the correct shape again. Its hard to predict the colors since you have to take into account the previous configuration of the liquid crystals, the amount of pressure you're putting on them, the location of the pressure, and the type of light and filters used in the display. So it usually just creates a strange gray sort of color."
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7ttnim | How does one encode data into DNA? | There's a video floating around about our newfound capacity to encode data into DNA...but what does that process look like? | Technology | explainlikeimfive | {
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"an inkjet printer embeds short fragments of chemically synthesized DNA onto the surface of a tiny glass chip. To encode a digital file, researchers divide it into tiny blocks of data and convert these data not into the 1s and 0s of typical digital storage media, but rather into DNA’s four-letter alphabet of As, Cs, Gs, and Ts. URL_0"
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7tway5 | Why do washing machines have glass windows whereas the dishwashers don’t? | Technology | explainlikeimfive | {
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"text": [
"Washer machines has a load level, also, requires some supervision of the activity [i.e. Trying to open the door when water level is hight]. Dishwashers can't be \"overloaded\" neither visual inspection is needed."
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7typo4 | Why is there so much innovation & improvement with Cellular technologies & speed(3G, 4G, 4G LTE, 5g), but not with wired speeds? | Over the past 10 years, there has been tremendous improvement with cellular speeds. It used to be that cellular internet was good for text-based webpages, and that was about it. Nowadays, in many cases people have cellular internet that's faster than broadband available to them. What are some of the reasons why cellular internet makes such huge strides while wired internet speeds have hardly budged in most regions? | Technology | explainlikeimfive | {
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"> What are some of the reasons why cellular internet makes such huge strides while wired internet speeds have hardly budged in most regions? Because with cellular internet, you have to wire a few cell towers with high-speed wired Internet, and then the rest is wireless. For wired to-the-home Internet, you have to run high-speed cable *to every single house*. The infrastructure cost is orders of magnitude more expensive. And in areas without a large population density, companies don't think that they can recoup the cost. So long story short, wired Internet is much faster than cellular Internet, but it's just too expensive to replace all of the cables in many areas.",
"I love a good anti-ISP circlejerk as much as the next guy, but this really isn't true. If we are looking at coax/cable speeds, [DOCSIS]( URL_0 ) (the 'language' that your modem uses to send data) has seen *massive* jumps in speed. > Nowadays, in many cases people have cellular internet that's faster than broadband available to them. This is really more a question of what people are willing to pay. I'm a little bit of an 'old' here, but in the late 90s, my first employer paid ~$500/mo to have a dedicated T1 (old tech / pre-cable) put into the study at my apartment. It reliably got me 4-5mbps up/down. Today I can get 1GB for $149/mo and higher speeds are coming in the not too distant future. And if you *really* want it, you can get a dedicated fiber link to your house for ~$500-$1500/mo (plus equipment) that can see speeds of up to 10GB.",
"I think there may be more going on than you may give the wired world credit for. At the time people were on 2G flip phones, their wired internet was, what, 10 meg down, with tons of people still on 1.5 meg DSL? Nowadays wired lines are getting gigabit speeds in some areas, with 100 meg not that uncommon. That's a pretty big jump. So perhaps the better question is--why is it not as obvious? The monopoly/duopoly mentioned is a part of it. There's more competition in the wireless space, so those companies blast advertisements all over the place about how much faster/more advanced they are. The cable internet company? They may well have speed upgrades available, but they don't have to constantly pound you with the option, so you may not notice it. Also, to use a driving analogy, going from 20 to 60 mph on a freeway will often seem like much more of a speed change than going from 60 to 100, even though its the same amount of change."
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7u1sfg | why did older bikes have one large wheel in the front and a smaller one in the back | Technology | explainlikeimfive | {
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"Before derailleur drive chains and geared hubs that allowed a varying ratio between the rider's legs' rotation and the wheel's rotation became common, the only way to change that ratio was to use a different sized wheel (a larger wheel requires a greater effort to turn, but moves more per turn). (Such a setup like you describe could also me manufactured relatively simply, as the cranks were fixed to the wheel: no ratcheting mechanisms or chains needed).",
"In addition to the gearing issue, large tires provided a smoother ride over pothole ridden streets. Dunlop's pneumatic (air filled) tire made this less necessary in 1888.",
"Think about your old tricycle: the pedals were connected directly to the wheel. One revolution of the pedals meant one revolution of the front wheel, meant you went forward X distance. X would be the circumference of the wheel. A bigger wheel would mean you could go further with one revolution (but you'd need to push harder to get started). Since your legs can only go around the pedals so fast, if you want to go quickly, you're better off with bigger wheels, since your legs don't have to move as much, they just have to push harder. The downside is that it's harder to get the bike moving to start with, and much harder if not impossible going uphill. We have long since solved the problem by connecting the pedals to gears, so that the number of pedal revolutions per wheel revolution can be varied depending on the gear.",
"Before chain drive was invented on a bike, you had to turn the wheel directly. A single gear chain drive bike has a specific gear ratio to go a specific speed if you turn the cranks a specific speed. Without that gear ratio, you would need a larger wheel to do the same thing.",
"When you ride a bike, the wheel is like your big round foot. Instead of your normal foot taking normal steps, your wheel foot spins around! Every time the wheel spins it's like taking a step forward. Move your legs around and the wheel spins. With a bigger wheel, you get a bigger step for each turn, and so you move faster. So, the front wheel of those old bikes would be just about as big as the rider could get their legs over, so they would go as fast as possible. It made the bikes more dangerous to ride because you had to climb up on them instead of sitting lower like a modern bike.",
"Because gears and chains didn't exist. Without this, the only way to turn a wheel is to attach the pedals and cranks directly to the centre of that wheel. Since they're attached directly, one turn of the pedals equals one turn of the wheel, unlike a modern bike where one turn of the pedals usually equals several turns of the wheel. With a small wheel, that means your legs turn very fast but you don't go very far. A bigger wheel goes further in one turn which is more comfortable, as well as easier and faster. The size of this wheel is limited only by the length of your legs, since you have to be able to reach just past the centre to push the pedals down past it. This is why all these bikes are usually of a similar size. Now, you also need a second wheel so that you have something to make balancing and turning easier, as well as to stop you simply tipping forward when you pedal. However, since it's not attached to the pedals, it doesn't matter how big this wheel is and a smaller wheel is usually less bumpy."
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7u4jbn | how medical students spent 1500 hours dissecting a nervous system without the cadaver just rotting before they could finish. | Yeah, that blows my mind. | Technology | explainlikeimfive | {
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"The cadaver is kept in formalin (a chemical that prevents rotting and other forms of degradation) for a few days to “conserve” the body. Once ready the cadaver can then be taken out of formalin tubs and used for dissecting.",
"Many anatomy classes have labs that have cadavers that have been around for years. Keep them cool and spray them down with a solution that I can't remember what it was/is called to preserve them."
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7u4umz | How storage companies like Dropbox keep files safe if all of your files are stored in one gigantic cluster that other users use | Technology | explainlikeimfive | {
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"Imagine Dropbox is a giant storage facility, like the ones where you can rent a storage locker and put all of the things from your attic. To prevent people from trying to break into others' storage units, customers don't actually get to enter. If you want to store stuff you just walk up to the front gate and hand them a box, along with your ID, and they store it for you. Later when you want to access it, you give them your ID and ask for the box by its name, and they retrieve it for you. With this model, they don't really need separate storage lockers for every user. They just need to do a really good job of keeping track of who owns which box, and never give a box to someone who isn't authorized to open it. The boxes could be in one giant room, organized alphabetically by name. All that matters is that the boxes are tagged with names and owner IDs. In this analogy, Amazon is simply leasing them the land where they bought the storage lockers. That has no effect on their security.",
"As other users pointed out, you don’t have access to the storage system. You interact with software they created that handles user identification and access controls to files. The free 5GB on S3 is part of the free tier, so only true for the first 12 months. Also Dropbox completed migration out of AWS in 2016, they have their own storage backend now. Google “dropbox s3 migration” and you’ll find a few articles that talk about it.",
"It really doesn't matter. Whether Amazon gives Dropbox separate buckets or one bucket, Dropbox only allows their users to access the files that user uploaded. AWS is like a massive self-storage facility. Now if Dropbox rents out one whole warehouse that's already divided up into closet-sized units, or installs their own closets into a massive empty warehouse, they still issue their users a lock and key to where they can only access the closet they have permission to."
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7u6ttl | why almost no smartphone protective case has a cover for the camera glass? | I mean it as a flap ([like dust covers]( URL_0 )), not a transparent layer. | Technology | explainlikeimfive | {
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"A decent quality smartphone will have a hard protective layer (e.g. gorilla glass) over the lens so it doesn't get scratched. It will resist scratches pretty well. On the other hand, smartphone cases are made of cheaper materials, usually some kind of plastic, and are much easier to scratch. So if you had a case over the lens, over time, there would be a bunch of scratches in front of the lens, all your pictures would come out blurry and terrible. Also, even if the case is nice and clear with no scratches, it will tend to add distortion, extra glare, and so forth to your photos. So bottom line is, they make a cut-out for the camera so your photos aren't potato quality."
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7u6zke | why do news anchors/cameramen still use bulky shoulder mount cameras when camera technology has advanced so far with things like gopros and their video quality? | Technology | explainlikeimfive | {
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"While camera \"bodies\" are getting smaller, things like high quality lenses, professional cabling interfaces, microphones, operator controls, and viewfinders/monitors are still the same size since improving their technology doesn't always mean decreasing their size.",
"Retired camera op here: There's still the matter of mass. While smaller, lighter equipment is great for less effort packing around in the field, a full size-ish camera has the advantage of increased mass which makes for smoother, steadier image capture when you're working handheld. Any little movement shooting with a lightweight rig will tend to result in a shaky picture. With a heavier camera the small movements are somewhat cancelled because of the effort to move the larger mass. Newton's First Law: An object at rest wants to stays at rest.",
"There are a number of reasons: * Stability--shoulder mounted cameras are much more stable than small handheld cameras). The difference is significant enough there is a cottage industry making shoulder mountings for those tiny cameras. * Controls--gopros have a fixed fish eye lens) large cameras can often zoom like [this]( URL_0 ). While news cameramen don't often use the zoom lens in a shot, they often use the different focal lengths available. * Battery life--The large shoulder mount allows a battery that powers the camera for several hours. * Storage--The large camera allows storage of several hours of high quality video. * Video quality--While both might shoot a 1080p signal, the news camera keeps [most of the data]( URL_1 ). Cheap cameras drop most of the captured color data (like the image on the left while the large one can keep an image like the one on the right. For viewing footage, both are usually good enough, but the images on the left will show if they are heavily edited or color graded (made to exactly match colors of other footage). There are also some nice to have features like better mikes, better cabling, and much better viewfinders that all require more space.",
"Those bulky cameras also have a lot more features that smaller cameras don't always have, eg. The ability to have 4 different audio channels, SDI out for live hits, dedicated toggles/switches/buttons that allow the operator to quickly adjust settings on the fly. They are also fairly robust and hold up better to abuse when you have to use them everyday. Plus it gives you more of a presence when out shooting news, cops and fire are less likely to give you a hard time when you have a big news camera with you. Source: shoot news for a local TV station.",
"Because that technological advancement has also been made in the shoulder rigs making them even better. Every advancement made in the small cameras has an equivalent in the big so the big are always going to be of higher quality, and so the better choice unless you specifically need a small camera.",
"Smaller cameras aren't as good as you make them seem. There are numerous visual artifacts that don't appear in larger ones. Plus larger cameras are easier to shoot handheld.",
"It's a question of ergonomics, flexibility, and quality. Firstly, it's easy to carry around something on your shoulder all day. Your body is taking the weight. Holding a little camera up by your arm would leave you aching after about ten minutes. You also want a viewfinder that covers your eye, so you're not having to shield an LCD screen from the sun all day. Secondly, gopros are quite limited in what they can do, and how fast you can do it. Think about what a news cameraman has to do on an average day, and how fast they have to do it. There's something right in front of them that they need to capture. Suddenly there's something 30 metres away they need to grab while it's still happening. Now they're following someone inside a house, and the lighting is changing dramatically. The camera operator has to continually adjust their camera to get the best image in those scenarios, and you can't automate those things and get a good result. There's the big obvious one of zoom, but you're also manually focussing, and there's also a bunch of things that will change the exposure (iris, gain, ND filters, etc). Some of those you can't even do on a gopro, let alone quickly. Think about having controls they can reach up and use blind, versus a little camera with a fiddly little on-screen menu system. One of those things can happen in less than a second, and utilise muscle memory. The other one might take 30 seconds, in which time you've missed the bad guy running out of court. Thirdly, gopros aren't actually that great for video quality. Video quality is about a lot more than resolution - the physical size of the sensor and the lens are the big differentiating factors.",
"Am a camera op. Something that hasn't been mentioned as a reason why a live broadcast might choose to use older/bulkier equipment: they work and they can take a beating. This is very important for live broadcast.",
"Getting all the right pieces required to make professional video for news requires certain things: high quality lens, plug-ins for video and audio on separate channels (ins and outs), a decent viewfinder that actually shows an image of what you’re recording accurately... But the most important is a shoulder-mount ENG (electronic news gathering) style camera. The reason shoulder-mount is still the most popular is because of the improvisational nature of the news. You have to react to anything at any moment. A DSLR gives a film look with a creamy background when shooting video, but the controls are laid out to be more still photo-friendly. This makes it so quick adjustments I can make with my ENG camera are often buried in menus on a DSLR. And without more expensive and time consuming gear, shooting with a DSLR without a tripod is not exactly steady video. With an ENG, my shoulder and my body can stabilize my shots and I can keep shooting while adjusting settings and keeping my shot stable and in focus. This feature is a must for live TV whereas I can’t look down at my DSLR settings in the middle of a live shot while zooming and pulling focus. We use DSLRs, but as a second or third camera for big interviews. I honestly use my tripod as much as I can, but there’s several key moments where you NEED to shoulder the camera or tripods are not allowed. And without a tripod/mount, any smaller cameras are inferior to ENG shoulder-mount cameras in live situations, sports, improvising, and any time where major adjustments to settings have to be made while walking backwards (confrontations, perp/court walks, politicians). Those examples are the bread and butter of news. So, don’t expect to suddenly see DSLRs out in the field with news crews. Shoulder mounted is king. Source: Shot news since 2008 and also some production work.",
"You don't have to worry about batteries. In college I covered sports for the paper. Got to know all kinds of photographers/videographers/sound guys/cable guys/broad cast etc. I needed 4-6 go pro batteries to cover a game, several SD cards, and since it wasn't my primary camera running one added a lot of work. Broadcast cameras can run off multiple batteries so you can hot swap them without stopping recording, Multiple card slots, some take SSDs which are needed when you have to offload footage ASAP and get it published. You don't want to wait on a dinky little usb 3.0 card reader and a micro SD slot. You need to Ingest, organize, cut and publish that footage 15 minutes ago. They can hook into a variety of audio sources, work either wirelessly or wired. Most live broadcast use wires since they're not prone to failing or interference the broadcast cameras get a specific line on the field they get to use so their cables are mostly out of the way but it's something that you just work around and respect. Gopro's suck in low light they have tiny sensors you just can't compare a 1/2.3-inch 12mp sensor (GoPro) to a dedicated 2/3\" 2.2mp (Broadcast) camera. You might think that only having 2.2mp is a bad thing its not. The camera natively captures 1920x1080 it's got massive pixels with more surface area to collect light compared to the tiny pixels crammed into the smaller 4096 x 3072 resolution sensor. Broadcast cameras don't need digital zoom or need to take stills they only need to shoot 1920x1080 video. Yes there are higher resolution cameras for film/broadcast but 99% Are 1920x1080 if it's for TV. Some/most also utilize 3 separate CCD sensors instead of one CMOS chip to capture video. Having those large physical controls makes shooting a lot easier you don't have to fiddle around with any touch screens or tiny buttons you can just let muscle memory takeover. They wouldn't be spending [$40,000 on a single camera]( URL_0 ) if there was a cheaper option that did the same job. Also the infrastructure that all these broadcast cameras plug into has been around for ages and isn't changing very fast. When you travel from stadium to stadium with various cameras and gear. When you get there you need to be able to plug in get set up and start filming. Not dicking around with adapters and unfamiliar infrastructure. We do see smaller cameras in use on things like the pylon cams and that's awesome. The NHL is also putting cameras on the Refs for some killer shots. But a small camera is just the only option there.",
"I had a professor in film school that said if you want to work with the most cutting edge equipment get into sports. If you want to work with stuff that uses duct taped to stay together, get into the news broadcasting",
"I’ve never seen a GoPro with manual iris, focus and zoom control. Or one that can be white balanced. Edit: two users have shown me evidence to the contrary. The more you know.",
"There’s also the “these guys must be pros with a camera like that” factor. If you’re going to give an interview and your walk up to a bunch of journalists who are you going to go to? The person with the expensive pro looking kit, or the GoPro?",
"Watch the barrel scene in the second hobbit movie The Desolation of Smaug. It used GoPros and you can instantly tell the quality is not as good as the rest of the film which used higher quality and bulky cameras as you said. Other posts have good technical explanations but this should serve as a good simple explanation.",
"Because the smaller cameras and GoPro devices are not broadcast quality. Lenses aside they shoot in a more lossy format. Where as a Sony fs7 or Ursa Mini Pro shoot much better 4K and HD",
"Lots of great answers below. One thing I didnt see mentioned in much detail is the balance of the larger cameras. Something that is a real problem with smaller cameras made these days. ENG (Electronic news gathering) style cameras are extremely well balanced. Maybe a little front heavy so that when it sits on your shoulder you can operate all day without getting too tired. A improperly balanced camera will wear you out in 5 minutes flat. Most new cinema cameras (RED, C500, Blackmagic) are just sensor brains and electronics that you plug a bunch of crap into and have a crap balance to work with. The ARRI Alexa / Amira are balanced right to the sensor and when you add a lens you can adjust the slide plate quickly and get awesome balance quickly. It a large bulky heavy camera but wont wear you out nearly as quickly as a RED that is half the size and weight. That said, the new C700, Ursa mini, varicam are heading in the right direction.",
"Australian Cibrian John Safran once said he has a friend who is a cameraman and he uses a big one because when he arrives at a shoot with a little handicam the client usually thinks he's not a professional without a big one. So he purposely uses a big one for the look.",
"I’m certainly no expert with regards to this, but my father works as an engineer at a local news station (he’s the one who fixed the cameras and other stuff when they break) and over the years the cameras have definitely gotten smaller and lighter. When I first started tagging along with him to work in the early 2000s one of those portable field cameras would have been bigger than me if you stood it up and probably weighed at least 20-30 pounds (I was too small to even try to lift one so I’m basing this on seeing adults struggle to lift them). The cameras they have there now are about a foot long with the standard lens, weigh 5-8 pounds and record to dual SD cards. Like others have said, it’s easier to get a steady shot with a shoulder mount camera than with a handheld so that’s why they’ll probably bet progressively smaller, but not necessarily shorter.",
"GoPros are crap. They are amazing for being small and generating fairly decent images on full auto, but they don't offer much in the way of manual controls, lens options, frame rate options, etc. And the video quality is only good because they do more than they should for being so small, but compared to professional cameras they look awful and are barely functional. The excessive rolling shutter artifacts alone are pretty appalling. They are also difficult to hold steady for long periods of time. And then there's the part where its difficult to view a live image to see what you're shooting. Professional cameras are designed to sit on your shoulder, which takes all the weight and allows you to focus on moving the camera with your hands and arms instead of supporting with your hands and arms. They take professional lenses, which zoom and focus manually, where a GoPro has a fixed wide angle lens and that's it. Pro cameras have controls laid out such that the operator can control it without having to look at any of the controls: everything can be done by touch. A GoPro has a couple of buttons and a somewhat complex menu structure. A pro camera can be operated quickly. The only thing you can do quickly with a GoPro is start and stop it. Everything else takes more time than a news cameraperson can afford. In other words, tiny cameras are great for specific things where you can get away with setting them up once and letting them roll on the same shot while on complete autopilot. That results in a certain look. It's not a tool you would use while chasing someone down the street, or interviewing an individual, or covering a fire from a distance.",
"Stability, stability, stability. Even a professional SLR used for video is light, and so the human body can swing it around with very little effort. A heavier camera takes more intent to move, which is desirable, because the human visual system only really compensates well for its own head bobbing. We have accelerometry for ourselves, not for the guy holding the camera. This is getting addressed with digital filters, but not as quickly as you'd think. Also, if you want a camera to be able to get any sort of zoom, the physics sort of require larger lenses. But that just explains why they're not camera phones, not why they're not SLRs.",
"The kinds of cameras you see used on the news are call eng (electronic news gathering) this is a design type of camera they are also packed with features that allow a very high quality recording by one person. Technology had come along way and independent camera people will and so shoot on dslr and large sensor cameras but most mainstream news company’s still buy their crew eng cameras as it is guaranteed to do the job it’s a purpose built tool. Dslr cameras are a lot smaller but have bad audio can not record longer than 30 minuets and have short range lenses. An eng camera uses a lens with a servo and a zoom range of around 18-200mm if not more with a fixed aperture this kind of lens dose not really exist in the small body camera world and when shooting news flexibility is everything. Source- I am a filmmaker who used to work in news, now I use smaller cameras and shoot corporate films. Edit- auto correct purpose was porpoises.",
"Actually there is a slow shift in movie productions towards smaller cameras. But it's slow and not as extreme as using gogpros. The gopro actualy is a bad example. You cant attach audio, can't zoom and the quality and distortion is still pretty awefull. But there are prosumer cameras like the Lumix gh5s or Sony a7r3 which are very small and offer without doubt far better quality than needed for TV. But there are a lot of reasons for the established, bigger cameras. Btw, the image quality is often not that important factor. 1. more, faster, more reliable Connections. Especially on TV you need a good video out, like SDI. Hdmi cant be as long and the port is not sturdy. 2. better audio interface, you can use multiple mics with XLR inputs (which is widely used) and record and level the audio in camera. Audio is extremely important. 3. things like bigger batteries, wifi connection, bigger battery, BIG ZOOM RANGE etc can be included. They are also very stable on the shoulder, compared to a handheld device (there are lots of rigs for small cameras to get the advantages of big cameras). Sensor stabilisation cant achieve the same. Also enough space for bigger storage like dual SSDs which are faster and better for higher quality video feeds with less compression. 4. bigger cameras can manage heat from the sensor better for longer recording. They also tend to be mkre sturdy (but this could also be achieved with smaller cameras, so that's not a reason for big cameras) 5. it gives you credibility on scene. You can't go and film an accident with a dslr. But the most important thing is reliability. This is greatly undervalued in the amateur sector. If you are live on TV (or any professional movie production) you just can't deal with unreliable, overheating, not weather sealed, small prosumer cameras. And you don't want to hassle with extra cables or adapters to get a working audio/video feed.",
"Key grip with a journalism degree here, the news guys have cameras that are built out by the manufacturers to a price where a camera op can have a bag with batteries and media and shoot all day. That means a zoom lens with a built in zoom control ($$). the media outlets have standards of quality (mbps) and the codec needs to be something you can edit quickly to meet deadlines. The big advancements in digital cinema cameras (arri,red,Sony, black magic, Panasonic, canon have I missed any?) are in the sensors and brains of these little square boxes. If I were to go and buy a RED dragon with a whopping great sensor to shoot news I would need a laundry list of crap that go with it just to be able to give media to the poor editor who has to deal with the workflow. Red lenses (which are all primes I think)$$$$ A follow focus with rings for each lens $ Red batteries $$ A red battery charger $ A red monitor touchscreen thing A little arm to hold the monitor A handle for the camera A dovetail plate to mate to the tripod A rail system to hold the dovetail Handles that attach to the rails A shoulder pad thing so I can hold the camera Pelican cases for All the pricey gear A camera assistant to label media, grab batteries, swap lenses, and berate on occasion. Oh yeah, and a sound guy who can monitor and mix audio, cuz there’s too much going on for a camera guy to mix a lavalier, handheld, and/or shotgun mike while pulling focus, iris, and framing a shot. P.s. A pair of cuffed skinny jeans and brown leather boots so you can call yourself a DP like the reality hacks. P.s.s. Also dont buy a red. They don’t get skin tones right without a bit of color correction from the DIT first. P.s.s.s. Also, If you do get a red, and I’m your key grip, I’ll hang a pair of white Oakley’s on your camera cart.",
"And why does security camera footage still look like I’m watching something out of a gameboy? It’s always so grainy, why can’t they fix the quality on security cameras?",
"Video resolution alone doesn’t define overall picture quality. Just take into account that the highest resolution that cable TV can bring to any television set (whether it’s an old tube TV from the 50s, or a fuckin 8K Smart 4D Vizio Samsung Disney Phat Raptor) is still to this day majorly only 720p, not even 1080. Professionals use professional equipment because there are *endless* specific controls on those cameras that consumers don’t want or need to worry about. Trust me, you’d notice if one day, all the news stations started shooting with GoPros and iPhone cameras. You couldn’t quite put your finger on it, but you’d know the quality was lacking in some way.",
"I once worked with an industry DP (using Arri Minis for his cameras) who stated that he didn't believe DPs or camera operator would have jobs in the future because the cameras would be able to capture EVERYTHING and it would be up to the director/editors to decide everything in post. I certainly don't think he's entirely right, but it was interesting to hear an opinion like that from the source. The truth is that at a very high level (i.e. in high budget films, and to a lesser degree in network programming) the camera operator is functionally similar to a dolly grip (who holds on to the cart that pushes the camera) and is functioning less and less like a photographer as camera technology advances. However, this is not at all true when you are talking about other types of camera. One reason news \"shoulder mount\" cameras are big and bulky is of course cost; even a pretty standard nowadays Sony FS7 still costs upwards of $10K US, so you're probably going to hold on to your cameras as long as you can, especially if you're not trying out new styles, which news shows rarely do. Another big reason they are \"bulky\" is because making a camera (even a small camera like the FS-7) portable, battery operated, and connected to the DIT, focus puller, and gaffer adds a LOT of weight and size to the base unit. [This image]( URL_0 ) of a rather small camera only has half of the modules attached to it that I am used to seeing on a network TV show. The lens attached is a nice one, not one you'd typically see on a news camera, but news cameras can have large lenses at times, too. The battery is obviously one of the biggest problems if you want to be running around and not have to worry about losing power. So, why not just use a go pro then? I think the main kicker here is in the dynamic range, to be honest. The sensor in even the most expensive go pros is more similar to a cellphone camera than it is to a professional camera sensor because a lot of it's use has been predetermined by the manufacturer. Production level cameras generally provide the camera operator/gaffer (and more importantly the editor) with many more stops of dynamic range. This is important for many reasons, but mainly, it allows you to worry less about exposure and getting a correct image when you're in the field, because you can shift the exposure compensation on the fly/in post without losing any colour detail. It is absolutely *imperative* in news to be able to capture usable images in all sorts of lighting conditions, from volcano eruptions to night-time bar fights. So consider the difference between a jpg and a bitmap file. In production we use raw files. You can use raw files with many modern cellphone cameras, and I think the new gopros can too, but without an appropriately high dynamic range it doesn't really matter. So this is what the DP meant when he lamented that camera operators and gaffers wouldn't be needed anymore. Because he saw a future where cameras would be able to capture ALL of the light almost perfectly, and you would be able to change everything in post, which is simply something that a cheap camera is nowhere near good enough to think about doing right now. Lastly, and while this might not sound like a big point, to me, it's HUGE! Consider the movement of a camera. If you're into movies at all, you know what I mean when I say that the *movement of the camera speaks to you*. News cameras are shoulder mounted because *that's the way we want them to be*. We want our street reporting to be... well... street! The perspective and shake of a shoulder mounted camera is VERY hard to replicate. I've seen overweight industry camera ops go to insane lengths (think *millions* of dollars) to try to implement technological \"bobble\" devices to replicate the particular balance of organic bumpiness to stability that a typical shoulder mounted news camera gets you, and FAIL. It's super easy to spot a fake, if you're looking for authenticity. So ultimately, don't expect to see vlog style videography from your news casters, because vlog style is a style that they aren't interested in. They're into \"news\" style, and that involves shoulder mount cameras.",
"You may enjoy this YouTube series where Vox explains how the BBC films Planet Earth II by explaining the history of their cameras and the effects they wanted from them: URL_1 I also found this article when looking for it, where National Geographic talks a little to the Verge. URL_0",
"Lens quality, XLR inputs for professional mics, ability to attach to a camera control unit back in the van so the technical director can adjust settings. The cameras themselves are heavier and provide for more points of contact with the camera operator for greater stability. Plus, at the end of the day, news is a business. If the cameras are still working and the reporters are able to use them easily and meet their deadlines, there’s no reason from a business standpoint to upgrade. A local station here still uses Panasonic cameras that save to antiquated (albeit somewhat more stable) P2 camera cards. A whole 35 minutes of 720p video can fit on a 16 gig P2 card.",
"In addition to what’s been mentioned: broadcast cameras are designed for live broadcast. They have outputs for connection to a switchboard and for voice communication between a director and the camera operator. Consumer cameras like a GoPro or a DSLR don’t have these outputs, and wouldn’t integrate with a live broadcast infrastructure. Another reason is that drastic change to an industry doesn’t occur quickly, especially when that industry has been around for awhile. People and systems are set in their ways, and it’d be expensive and risky to make such a drastic change, even if in the end it’s cheaper (a broadcast camera can exceed $100,000, and operators are paid several hundred per day here). Source: camera operator and videographer",
"No one has mentioned that the smaller and lighter the camera, the less steady it is, the more shaky it is. When you're 'running and gunning' in an in-the-moment situation like a building fire a tiny GoPro or even a HandyCam will end up looking like the Blair Witch Project. For this reason, when [ENG]( URL_0 ) camera manufacturers came out with the first memory card based cameras, they literally kept the same form factor and replaced the internal tape assembly with a dead weight. That said, at my station we use both full-size cameras and medium-sized HandyCams, but we use GoPros and now drones for special shots. It really depends on the nature of the shot you're getting, the piece you're producing, and whether the reporter has to go out in the field solo and shoot themselves. Our reporters even have a phone app to use in a pinch, if say, they coincidentally end up proximate to a breaking story while off duty, etc.",
"There's a few reasons, beyond the main ones I've seen people post here which is weight for stability and peripherals. As an ex-ENG (news) cameraman, I can tell you that a GoPro was a constant piece in my arsenal, but it really only came in to use maybe 5% of the stories I shot because shooting news stories is mostly a reactive skill, not a proactive one, and the set-up time for smaller cameras doesn't lend itself to shooting news often. Shooting with DSLR-type cameras and mini-cameras typically require you to change the environment to suit the shooting style of the camera (for instance in a nice, controlled studio). With a GoPro you need to scout a location that will give you the shot you require, set-up the camera, and either check the set-up or hope you've gotten it right. Most news sotries are evolving as you cover them, you often don't have the luxury of stopping filming to set up a camera for a single shot. DSLR's are not good at rapidly handling shifting environment changes (light change as cloud pass overhead, going from indoors to outdoors, even just light level changes room-to-room), and many of the smaller cameras rely on servos, which have a delay time. News cameras are specifically set up to be as quick as possible in reacting to changes in environment, they are designed to change to suit the environment, rather than changing the environment to suit the camera. This, however, requires fairly large lenses and the body needs to be large to match.",
"(TV camera op) The biggest benefit of larger cameras for me is the weight. Being much heavier means I can swing it around and get a much steadier shot than if I was holding say a DSLR or GoPro. Also, having a third point of contact on my shoulder is invaluable to stability. When the camera is on my shoulder it feels more like an extension of my arm than something that I have to hold out in front of me. When working in a high pressure live broadcast nobody wants to dig though layers and layers of menus to change a setting, so pretty much every control possible is given a physical button or dial, and that takes up space. Another thing to mention is that there’s a lot more to consider when talking about image quality than resolution. While a GoPro might be be able to shoot 4K video, it’s not capable of keeping every bit of data, so you end up with terrible compression. Larger cameras can also house larger sensors, which improve low-light performance and help get a shallower depth of field (a way to measure how much of the image is in focus). Larger more expensive cameras also have better dynamic range (a measure of the camera’s ability to display dark things and light things in the same frame), which makes them more versatile in the field. Here’s a fun fact: even though they shoot in 4K, most live shows still broadcast in 720p, and most people are never the wiser. TL;DR: Bigger cameras are more stable and have more buttons. Also, resolution isn’t everything. This video is only mildly related but useful and entertaining. URL_0"
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7u8cp4 | How does a Virtual Private Network protect my data and computer on a public WiFi network? | Technology | explainlikeimfive | {
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"Let's make an analogy. You have a postcard you want to send to your aunt. You write \"Greetings from sunny Alaska!\" on it, and put it in the mailbox. The USPS picks it up, and posts it to your aunt in Florida. But since it's just a postcard, anyone can pick it up, read it and change it. This is normal HTTP: you send something without any safety to someone else. Obviously, you're not going to post important stuff over something that can easily be read by anyone. This is why we have HTTPS. To continue the analogy, HTTPS is sending the same postcard to the same aunt, but you send it in an envelope. This way, you can't just open it up and tamper with the contents: people will notice that it has been opened. HTTPS works because you encrypt the contents and send them over to wherever they need to be. It's this encryption that makes sure your bank credentials aren't read, or your passwords aren't sniffed out (this is why you NEVER use a site that uses HTTP on a login page, or even has HTTP when you need to log in. You can now get an HTTPS certificate for free, so there's no excuse to not use it!) And a VPN is like sending the postcard to your friend Bob, who then sends it to your aunt. For internet traffic, it means you are sending your requests to another server, who then forwards them to the correct address. Why is this useful? If you do this for all your mail, it now appears that you only send mail to Bob, and nobody else. Even if your mail is in an envelope, the USPS can still keep track of how often you send mail to whom. Let's say you're a married man who has an affair with his secretary. You send her love letters quite often, and the USPS notices that you are sending her a lot of mail. A malicious employee could then possibly blackmail you."
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7u8epd | Why does the Magic Eraser work better than a sponge? | Technology | explainlikeimfive | {
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"Since my first response was deleted, a magic eraser is basically just a chunk of melamine foam. Melamine foam is abrasive. It's like a fine sandpaper. So when you are using the magic eraser, you are essentially scrubbing the surface, instead of just wiping the surface."
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7u8yjw | why does the Australian government fail to provide a sufficient upgrade to our broadband network even with the knowledge that the Internet will be as vital as the electricity grid was in the 19th century? | Technology | explainlikeimfive | {
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"Most of the people that make the decisions in the Australian government are the kind of people that don't think the internet is important. They are the types of people that buy the newspaper every day. If it's not something they grew up with, they don't really care about it. They are set in their ways, and they fear change. There is also no real motivation for them to do anything about it. Any actual upgrades worth having will take decades (how long has the NBN been going now?), and the party in control only cares about what they can take credit for in the current term (because they know full well they may not get another term next time). Think about how the internet has been working for a very long time. It has mostly been proivided using an existing copper wire telephone network, that has been in place for a very long time. Most of this copper phone network is all connected in the crapest way possible. Find an older apartment building, made some time in the 70s, then find the MDF for the phone system somewhere in the basement. It will be bare copper wires wrapped around bare metal termination posts, with no insulation, and not a drop of solder holding it all together (or any other form of positive fixation). [Here's one I had the pleasure of having to deal with a few years ago.]( URL_1 ) Apparently there was nothing wrong with this system, and the connection issues were a problem with my modem or plain old operator error... [Ever seen one of these on the side of the road?]( URL_2 ) Care to guess what ther are? These are accessible connection nodes for the same copper phone network. They look very similar inside as the MDF pic I posted above. They use slightly newer technology though, called a [punch-down]( URL_0 ) terminal. This uses no insulation just like the older system, and it uses nothing but the pressure of the wire forced between two metal tabs to make the connection. It is used for one reason and only one reason, that being it is extremely quick to use. But just because it is quick doesn't mean it is good. The issues with the NBN are simple. The original idea was to install a completely separate system that specifically **DID NOT** use this crappy old technology. It was supposed to be fibre-optics to your house, Australia wide. Then the ruling party of the government changed, and the new one decided that the proposed plan was not required. They figured the people didn't really *NEED* super fast and reliable internet (see the start of this rant), so now we have super fast internet that stops around the corner, and then it's connected to your house using the same crappy old copper phone network. I would go on, but this should be enough to show you why we are only ranked 55th in the world for internet service, and why it's not going to change any time soon."
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7ub6u8 | Why do CG movies like Coco only get 2K upscaled releases on 4K Blu Ray? | If it’s all 3D rendering, can’t they just export the original content at 4K resolution? Is it because textures in the original render were only made to look good at 2K? Or because these projects are started so far in advance that they didn’t predict the industry was heading toward 4K? | Technology | explainlikeimfive | {
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"You can't \"just export it\". It's a massive undertaking. I found a quote that for Monsters University, the rendering time was 29 hours per frame. This is of course massively parallelized, so rather than working a frame at a time, they're going to do say, 5000 frames at once by dedicating a lot of hardware to it, and finish it in a month. Setting up such an operation takes real work and effort, you don't just randomly decide \"Oh, it would be nice to increase the resolution\" and do it. Also, raytracing scales linearly with the number of pixels, so 4K takes 4 times longer than full HD to render. So if their hardware rendered HD in a month, releasing 4K is going to take about 4."
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7ub9dj | How is brute forcing a password directly related to hashing? | As I understand hashing is an algorithm that produce a string of character and numbers based on input. However, unlike encryption, the algorithm isn't created with the intention of allowing the user to find the original input. I know that databases store passwords after they feed them through the hash algorithm because it safer that way. I understand all that, but I don't understand how hashing has anything to do with brute forcing the passwords themselves. Sorry if there are any spelling and grammar mistakes. I wrote this in a hurry. | Technology | explainlikeimfive | {
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"So what you do step (1) Steal the hash data base so you have user names and the hashes for the passwords that go with them (2) Start hashing potential passwords and comparing them to the database. (3) if you get a match you found a password that works with that user name, try it on that server or in other places (people reuse passwords and usernames all the time) Step (2) is where you brute force. If you have no idea what potential passwords to try you just start with AAAAAAAAA then try AAAAAAAAB etc.",
"> As I understand hashing is an algorithm that produce a string of character and numbers based on input. It's a bit more than that, and it's not hard to understand... Hashing is a mathematical function that *maps* integers from an *infinite* number space to a *finite* number space. For illustration, suppose we have such a function that will take an integer of any size and map it to an integer between the values 0 to 9. What would this function look like? It can be as simple as taking the remainder of integer division by 10! Remember remainders? Before you learned long division in second grade? Take any integer, a whole number, divide it by 10, don't go into the fractional representation past the decimal point - once you get a number that can't be divided by 10, you're done. And that's your hash! All numbers can be hashed into this space. 7 hashes to 7. 17 hashes to 7 as well. 326 hashes to 6, because 10 goes into it evenly 32 times... Of course, that's a lousy hash algorithm. But it demonstrates all the important principles. It's not reversible, because with a hash of 7, what number produced it? There are infinite possibilities. Your password is an arbitrary number of characters, but down low, in the hardware, those characters are just numbers *enumerating* the characters in an *encoding*. ASCII and UTF-8 are two such examples (that intentionally overlap). Capital A is 67, capital Z is 90, lowercase a is 97, lowercase z is 122. All the symbols, every period and comma, and even the symbols for numbers themselves, the characters 0 through 9, are all enumerated, and your program maps that number to a table of graphics for each character (essentially). This means you can think of your password as a sequence of numbers, and how you interpret it, you can think of it as a singly large integer of some arbitrary size. So you can hash it. Also notice that multiple inputs can map to the same hash. This is called a collision. In terms of passwords, so long as I find a password that matches your password's hash, I don't care if it's the same or not, I'm in your email. So you want a space that's big enough, and an algorithm that will distribute hashes across the space evenly. So brute forcing a password is trying to find a password with a matching hash to your password, if not your actual password itself. This is the hard, naive, desperate way to do it, and no one really does it this way because it's not effective. What computer criminals do is spread trojans on computers so that they have a fleet of \"bots\", computers secretly under their control. They can instruct these machines to do anything. They're not interested in your data, but your processing power. Not only do they send spam or attack computers, they produce *big ass tables* of hashes to passwords. If I can compute every possible hash for every possible password, the problem of breaking into your online account becomes easier - all I have to do is steal your hash from the service, and *look it up*. Now I know your password, now I can login. Typically, logging in and pretending to be you, typically in an automated fashion, is preferred, because it draws less attention, it's easier to pilfer valuable information, and allows the attacker to utilize these resources if they can't gain direct control of the machine. These are called rainbow tables, and they're utterly gigantic. Terabytes, easily. And they tend to brute force compute every possible password, incrementally. So 'a', 'b', 'c', then 'aa', 'ab', 'ac'... Every additional binary bit *doubles* the size of the table. Because they're limited by compute time and storage, the goal, then, is to have a password longer than what's in the rainbow table. So if they compute all passwords up to 24 characters, have a password 25 characters. They have to go through 8 doublings (8 bits to a byte, 1 byte for a UTF-8 character), to be sure to include yours. There are nuances to all this, of course, but this is the *basic* gist."
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7ucnlq | How does steel affect a MRI, or magnetic resonance imaging, while using it? | I'm curious since this article about a man who died a couple of days ago in Mumbai, after being sucked into an MRI machine. | Technology | explainlikeimfive | {
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"The key word is *magnetic* resonance imaging. There's a giant magnet spinning around the machine. If you bring a steel anything anywhere near an MRI machine, it'll get pulled towards the magnet, slamming into the machine's outer case with incredible force. If you're between the steel thing and the machine, you're not going to have a good day. The force of the object slamming into the machine is also likely to damage the machine leading to a rather expensive repair.",
"The MRI machine is comprised of a large magnet, and just like any magnet will attract metallic objects. Which is why no metallic objects are allowed in the vicinity of the MRI machine. The strength of magnets is measured in Tesla ( 1 Tesla is equal to 10,000 gauss) and most MRI machines in the field are of 1.5T (3T magnets are also seen). To put that into perspective, the earth’s magnetic field is approximately 0.5 gauss. So 1.5 T magnet is equal to 15,000 gauss (approximately 30,000 times the magnetic field of the earth). Once a magnet is engaged, it's quite a task (expensive and time consuming) to stop and start it again. So if a patient is wheeled into the MRI room with a regular wheelchair or an oxygen cylinder, it's simply sucked in and can cause injury or death."
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7uebqv | How do people who specialize in computer forensics retrieve data on a hard drive that has been formatted or magnet wiped? | Technology | explainlikeimfive | {
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"Reformatting can be as simple as deleting the file system and rewriting it. That won’t delete any of the data, just remove knowledge of where it is. Secure formatting will rewrite all the bits and is not recoverable. Magnets generally aren’t strong enough to ruin a drive, those that are will do so by physically bending the case or disk. The easiest way to securely delete a drive is to encrypt it and throw out the key.",
"When you delete files, they aren't actually deleted. The location where those files are become labeled as safe to overwrite. Until your computer actually saves something new over that location, the \"deleted\" files will remain. Formatting your hard drive doesn't completely\"delete\" the data either.",
"This is becoming increasingly impossible. SSD drives store data through what I'm going to simplify as a \"floating gate transistor\". These transistors can hold a charge, like a wool blanket in winter. And they can hold that charge for a looooooooooong time, it can easily be a decade. When a drive writes data to this medium, it will do so in whole blocks of them at a time, typically 4 KiB. Even if you're only writing 1 byte to a file, a 4 KiB block is getting zeroed, and then your non-zero bits are \"pulled up\" to store a charge. That said, when you blank a block, that data is gone forever and there is absolutely no way of recovering it at all. There is nothing \"residual\" forensics can pick up on. The only reason that's not entirely true is that to preserve the lifetime of these gates, and for performance, the drive won't blank a block just because you deleted a file. The \"record\" of the file is what gets removed, and the data contained in that file is left abandoned until the drive reuses that block for something else, some other file. Until that block is reused, your old data is still there. As for magnetic disk drives, the good ol' hard drive as we've all known it, same thing - the drive isn't going to do work it doesn't have to, and will simply abandon blocks and sectors on the platter until it needs that space, it only deletes the record of the file having existed. Now, with these drives, even if you overwrite the block, forensics may still be able to recover the data. This was far more true of old drives than drives of even a decade ago. I mean old drives, pre-2000. Older even. The way this is *theoretically* possible is because you have an electromagnetic head that physically moves over the surface of the platter and emits an electromagnetic field to change the magnetic polarity of the surface of that disk. It's not perfect, and there could be surface area outside the intended trace along that path that also had it's surface area polarized. You would need millions of dollars in equipment and specialists to read across the surface of the disk with high precision probes looking for this slop. The problem is, there's only 3 ways to increase data density on magnetic disks - more platters, smaller write areas, and more tracks. Manufacturers are doing all 3. So now you're writing data more precise, and more data densely packed on the platter. It's getting too hard to find the magnetic slop between the tracks because there is almost no wasted space on a platter these days. I remember an open challenge of a drive that had one text file on it with a simple phrase. The file was deleted and overwritten with zeros in a single pass. The challenge would tell you exactly where on the disk to look for the file. All anyone had to do, to win a few thousand dollars, is take the drive and recover the phrase. It stood for years and no one would byte, because no one could do it. This was 2006-ish. I don't know if that specific challenge remains open, but I'm sure others do. It should be forever only \"theoretical\" that data off such a drive is somehow recoverable. Most forensics out there use publicly available and free data recovery tools. These programs look at the abandoned and empty spaces, especially of magnetic drives, to find abandoned bytes, and the algorithms employed are able to deduce which groups of bytes belong together and in what order, to reconstruct documents and pictures. Notice that even shitty encryption can foil top agencies like the NSA, who had to beg Apple for a means of unlocking a phone of some criminal suspect (they said no, and a 3rd party had a hack for that specific make model, and software version - they were able to charge whatever they wanted because they were the only ones who could have done it, and it was by complete happenstance). So it's not hard to defeat, and these so called \"forensics\" are really just IT guys who know nothing more than how to type in a command. 99% of them are stopped dead in their tracks by the inherent behavior of new technology and good, basic security practices that are increasingly becoming the default."
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9kf1ry | How does a single speaker produce multiple frequencies simultaneously to play music? | Technology | explainlikeimfive | {
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"Have you heard of the principle of wave superposition? If a speaker is producing 10 different pitch sounds, you could draw them out individually and “add” them together to get what the resultant wave looks like. That’s what the speaker is actually doing; producing that combined waveform.",
"Speakers work just like ears but in reverse. You can hear 10 different pitches because all those pitches vibrate the air at different frequencies and when they hit each other they add together to make a more complicated soundwave. Your brain uses pattern recognition to pick apart the complicated soundwave into several individual pitches. Speakers vibrate in a way to produce complicated soundwaves, which your brain then picks apart to \"hear\" different sounds as if all the instruments were playing around you and their individual sound waves were colliding in the air",
"It would be more helpful to ELI5 how we perceive sound first. We don't perceive sound waves the way our ears physically receive them, like what we're used to a sound wave looking like (Those spikey, noisy graphs where the horizontal axis is time and the vertical axis is basically the movement of the speaker.) What we hear is the power in each frequency. Imagine instead, a graph where the horizontal axis is the note (frequency) and the vertical axis is the power (loudness) of that note. We here the note G as a spike on that graph at that G frequency. With that in mind, you can imagine how much easier it is to identify 10 different notes being sung at the same time. It's basically just 10 different spikes on that graph. Hearing the notes with our ears is as easy as looking at the spikes with our eyes. Back to your actual ELI5 question, speakers produce the sound wave I first described. That's what actual sound waves are, a mess. Our brains just convert them to something more meaningful. AMAZING POORLY EXPLAINED RELATED FACT: Our brains are not sensitive to changes in phase (shifting a sound wave backwards and forwards in time). You can shift the phases of all 10 of your singers around all you like, creating a COMPLETELY different sound wave, and we cannot tell the difference. At all. Basically, our brains are so amazing at extracting frequency and power information from sound that we don't even perceive the original sound wave. If that doesn't amaze you it's definitely because I explained it badly. Please nag me to re-explain if you're interested."
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9kga27 | How does my radio know which frequencies are stations? | When I hit the "seek" button on my car's radio, how does it know when to stop? | Technology | explainlikeimfive | {
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"The electronics basically tune through every frequency, and listen a micro-second to see if there's a signal. When it comes through the antenna, the signal is a frequency of voltage, and \"no signal\" is basically a flat voltage; if you could hook it up to an oscilloscope, you'd basically see the difference between the spikes (of voltage) and the flat line (no signal). So basically it's just that the electronics can check each frequency very fast.",
"It's basically an algorithm that can detect how clear a radio station is. It can detect if it's mostly white noise and then skip over it or if it's getting some real sound and will lock onto that frequency. That being said it's not perfect. It's very easy for you to find a station using seek wait just a few minutes and it won't be able to find it again if you're in a spotty area."
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9kjscm | The term 'overclocked'. If something can be over clocked, why isn't that just the new maximum speed? | Technology | explainlikeimfive | {
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"There are always inpurities and small scale defects in silicon wafer chips. Usually these don't cause problems at slow speeds. But as you increase clock speed (the frequency / rate at which bits flow around your chip) the impact of these impurities increases. So what they do is they make each chip then they'll run it through some tests. If it passes at 2.4 GHz, then they try for 3.5 GHz and so on. The speed at which the chip consistently passess is its new base speed. At least this was how it worked back in the days of Pentiums and 486s.... a 66 MHz chip was the same as a 100 MHz chip it just had more flaws and couldn't run as fast. So overclocking is simply driving a slower rated chip... faster. With the caveat that it will use more power, and possibly the fabrication flaws might cause it to randomly stop, glitch or reboot.",
"The reason is that manufacturers have stricter standards than your average user so there's room for overclocking if you are willing to risk system instability. The other thing is that manufacturers clock their chips to work with the stock Heatsink Fan (HSF) that they include with the CPU. A higher default clock speed would likely lead to the CPU overheating on the default HSF. Modern CPUs throttle back when they detect overheating to prevent permanent damage. So users who want to overclock have to spend money on better cooling solutions than just the stock HSF. In the past every CPU could be overclocked but then Intel caught onto the fact that they weren't making money from this. So they locked most of their CPU's to prevent overclocking and made some overpriced chips that were unlocked available so that they could profit from this enthusiast market. These are the Intel K series of CPUs. I'm not sure whether AMD allows overclocking across it's entire range or not.",
"Max speed is different then max safe speed. Overclocking means you are setting the speed above the recommended safe maximum.",
"The chip often isn't designed or quality assured for the higher speed, so it's not guaranteed to not cause damage or make errors (crash) it's like a car manufacturer having a recommend \"max revs\" to ever put a car through to maximise the engines life, but then people tinkering and messing with the engine to push its power output even higher (with increased risks)"
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9kotfu | how does a camera autofocus and know what to focus on ? | Technology | explainlikeimfive | {
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"There are two main autofocus types. Phase detect autofocus is used by SLRs when not using live view. The image coming through the lens is split and then the lens is moved until the image comes back together perfectly. This is also used in newer mirrorless cameras using dual pixel technology. Contrast detect autofocus works by ... Detecting contrast. Imagine a black square on a white background. When it's perfectly in focus, you will have a perfect black pixel next to a perfect white pixel. If you defocus the square, you have shades of grey between the black and the white. That is how contrast detect works - it seeks to have as much contrast between edges as possible. It's used in mirrorless cameras and SLRs in live view. How the AF system knows what to focus on depends on the settings. If you leave it on full auto some pretty sophisticated code takes over to detect likely objects like faces or moving things. If you use a more manual mode to select focus it just uses whatever is under the focus point.",
"A camera is composed of a sensor and a lens in front of it. The distance between the sensor and the lens determines the distance at which a subject appears 'in focus', let's call it focus distance. The lens can move back and forth to change the focus distance. With manual lenses, it's up to the camera operator to change the position of the lens until it reaches the position that produces the desired effect (subject in focus). With autofocus, the user chooses a portion of the image that they want to be in focus; then, the camera sends some light rays in the environment and, based on the properties of the light that it receives back, estimates that distance between the sensor and the subject. Finally, it adjusts the lens position so that subjects at the estimated distance appear in focus."
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9kpbx8 | The difference beyween AMOLED and P-OLED? | For example, the Pixel 2 runs AMOLED screen while the Pixel 2 XL runs P-OLED? What's the difference? | Technology | explainlikeimfive | {
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"AMOLED stands for \"active-matrix organic light-emitting diode\", where the AM part means that each LED has an individual transistor driving it, hence \"active\". Practically all graphical displays these days are active-matrix. The OLED part doesn't specify what kind of organic molecule is used as the light emitting material. P-OLED is more specific type of AMOLED display that uses an organic polymer (=plastic) as the light emitting material.",
"A P-OLED is much simpler and thinner than AMOLED (just Samsung's name for Glass OLED), see this image: URL_1 In the real world however, P-OLED might have a bit more durability since it's not glass-backed, but AMOLED can use plastic too, so it's really a toss up. URL_0",
"Display engineer here. P-OLEDs can flex. One is made of glass and the other plastic. A *substrate* is the material a display is built on. If you make that display out of glass, it will be very hard but not able to bend. If you make it out of plastic, it will be lighter and possibly able to bend (depending on the other parts). An LED screen is made of - a substrate (stiff layer everything is built on) - LEDs (tiny, efficient lightbulbs that are the pixels) - traces (small wires connecting the lightbulbs) - the transistor matrix (tiny switches controlling which lightbulbs are on) Flexible screens are hard. Not only does the substrate have to be flexible, but so does everything else. The LEDs (which act like tiny lightbulbs) have to either bend or the wires connecting them have to. Samsung recently figured out how to get those wires to bend (essentially, they are coiled up zig-zags like old landline phone cords). So now plastic substrate OLED screens can flex.",
"It sounds like P-OLED uses a plastic polymer in one of its layers instead of a more common glass material. From what I can tell this makes it more flexible in the manufacturing process and possibly more durable. AMOLED is a Samsung marketing term for what seems like a fairly standard OLED display."
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9kphql | How do solar panels work? | Technology | explainlikeimfive | {
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"Well, light is made up of a thing called ~~protons~~ photons. Some materials, like silicon, out there have a photoelectric effect, which means they can take these photons and use them to bump off electrons, which can then be picked up by a magnetic field, which is what all electricity is.",
"Think of electrons as balls and photons as more balls. Throw a ball at a ball and the ball flies away, a “tube” can collect these balls! Search for the photoelectric effect if you are interested in the physics side of it"
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9kqbrq | How does my “Maps” app know where traffic is and how congested it is? | Technology | explainlikeimfive | {
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"They get it from ZipDash. In 2004, Google acquired ZipDash, a company specializing in realtime traffic analysis. It feeds their realtime map data, and is used by Waze and others. Apple maps doesn't disclose their sources, but it's probably one of them."
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9krpqy | How do car horns make sound | Technology | explainlikeimfive | {
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"When you shake a thin piece of metal it makes a noise as it pops back and forth. Car horns shake a diaphragm (often metal) usually with a solenoid that switches very fast, to make the constant buzzing instead of just one or two pops."
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9ktyvf | How do mics on phones not pick up everything that plays through speakers? | Technology | explainlikeimfive | {
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"The phone knows what it's playing it out the speaker and is able to subtract that from what comes in the mic"
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9kwk5j | How can glass be cut using a laser? | Technology | explainlikeimfive | {
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"Glass absorbs some of the energy from the light that passes through it. Look through a piece edgewise and it will look green or blue as a result. With a laser you can put a huge amount of energy into the beam. Even if the glass only absorbs 1%, a good CO2 laser can add enough energy to melt the glass under the beam."
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9kwkp2 | The relationship between a wifi router's signal strength, and the speed/throughput of your connected devices. | For example, if you're subscribed to a 100Gbps internet connection, but your wifi routers' signal strength is just 60%, does it mean your connection can only go as fast as 60Gbps? Overly simplified example, but you get the idea. | Technology | explainlikeimfive | {
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"Okay, so, imagine you and a friend are sitting alone in a room. They say \"hello Crow, fine evening isn't it?\" You probably heard them just fine didn't you? Good signal strength. Now you and your friend go to opposite ends of a gym. He says that again but without saying it any louder (Wi-Fi transmission only has so much output power). Maybe you caught it all but may be you say \"what?\" a couple times first. Took time to get the message didn't it? Now you two go to a crowded bar and he's 20 feet away and says it. You probably keep saying what a few times before you hear it clearly. This is like having a ton of devices on similar channels on Wi-Fi."
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9l1283 | wireless cellphone battery charging | Technology | explainlikeimfive | {
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"Current flowing through a wire generates a magnetic field. Conversely, if a moving magnetic field encounters a wire, current is induced. Alternating current flowing though a coil of wire in the charger creates a constantly moving magnetic field surrounding it. The phone has a pickup loop in it which converts the magnetic field back into electric current and charges the phone. It's called \"inductive coupling\" and the phone/charger system basically make up an \"air core transformer\" (good keywords if you want to read further.) Magnetic field strength drops very quickly with distance, so these types of chargers only work efficiently at close range. Induction cooktops work the same way, except the current is induced into the pot instead of a pickup coil, and the electrical resistance of the pot causes it to dissipate power and become hot."
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9l22e4 | how does a fit bit know when you are asleep and what stage of sleep you are in? How accurate is it? | Technology | explainlikeimfive | {
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"it tracks your movement while you sleep. If the wearable has a heart rate monitor, it uses that as well to further it's accuracy. Generally speaking, the more you move in your sleep, the less accurate the readings will be. But overall, some studies were conducted on sleep trackers, like the Jawbone and others, and it was concluded that they're pretty accurate with sleep tracking. & #x200B; Also, to this point, no matter what your sleep tracker says, it cannot accurately tell you about your REM, or deep sleep, stages. For this, it needs more sophisticated equipment like eye tracker, brain waves, etc...They try to do as accurate a job as they can with movement and heart rate to measure REM sleep but it's not really that accurate.",
"Wow first time that I can talk about something I've worked on. I've worked on machine learning with sensory mobile devices (like fitbit or your phone). Generally most devices have only three sensors: an accelerometer, a gyroscope, and a clock. Using these three devices you can measure 7 different values at a given time (XYZ acceleration, XYZ angular acceleration, and time). By gathering several data points you can then get a sense of movement and associate certain combinations of acceleration and time as types of movements (lets call these different features). By performing experiments in the lab with people you can fit these features (predictors) to an observed action. Now you have a model that takes in predictors and outputs an (estimated) action. Depending on the model you'll have a wide range of accuracy but overall it's pretty good. Another way to think about is linear regression (or y=mx+b) where x is a predictor and y is an action. Except we have hundreds of x's.",
"Similar question to the original. The new apple watch has fall detection. My father wants to get me one since I have epilepsy. How does it know you've fallen?",
"the fitbit I used was accurate if the measurement involved movement: but inaccurate interpretation if there is no movement. Most nights I spend 60-90minutes lying very still trying to get to sleep. This non-activity was recorded by fitbit as sleep. It isn't.",
"I was recently at a lecture on sleep health with a scientist who just studies sleep. She told us that if you're an active sleeper it's useless and even if you're not it can only tell that you're sleeping, not what sleep stage you're in.",
"#Answer backed by science: --- They're basically trash at sleep tracking. The first author of [this article]( URL_0 ) does a good bit of his work on validation of health/fitness wearables. There really isn't a great way to track sleep through motion, so no matter how \"good\" they get, or how much they \"refine\" their sleep measuring algorithms, if they use the same method (accelerometers) they won't ever be that great. They're also not great at tracking calories burned, but that's another argument. Their most accurate (and useful) metric is heart rate - and you can buy electronics and make your own heart rate tracker for like $5. That said, health wearables have a pretty great ecosystem, are pretty motivating, and are also just cool and interesting. Sooooo if you want one and think it can help you change your health habits, I'd say it's worth it.",
"Anecdotally, I mentioned that I’ve been wearing a Fitbit to my sleep doctor who treats me for my sleep disorder and her immediate response was “those aren’t very accurate”. As for how it works, it can only sense movement and heart rate so it would track your heart rate drop for deeper sleeps and for REM sleep, it would most likely be a higher heart rate with low/no movement. Overall, I imagine it’s kinda like weighing yourself everyday to track your health, it can give you a decent idea but is mostly just a rough estimate.",
"FWIW, I have a Fitbit Charge 2 and it does NOT track my sleep with any degree of accuracy. It usually says I've slept 1 or 2 hours a night. You will find many people are very disappointed with sleep-tracking not working as advertised if you peruse the Fitbit forums.",
"It doesn't know. I do sleep studies and EEGs everyday. My co workers and I always chuckle a little when a patient comes in with their fit bit sleep tracker statistics.",
"It uses the same mechanism of movement equating to steps to track if you are asleep. If you are moving in bed, apparently you aren't sleeping. So it isn't really accurate at all. It doesn't accurately track steps either. It is a ballpark estimate. Because according to my fitbit, sensitive setting means I sleep 1 to 2 hours per night. On regular setting, I sleep 20 hours per day.",
"Weird to me this is 7 hours in and the question hasn’t been answered. I’m a psychologist with particularly expertise in sleep. There are 4 stages of sleep, REM, and then Non-R.E.M. stages 1-3. We move around quite a bit particularly during non-R.E.M. stage 2 where we spend most of our night. We don’t move at all (unless there is a disorder) during REM stage, otherwise we would act out our dreams. Our muscles actually go into a state of paralysis during this stage. Anyway, I think the sleep trackers are bullshit because the level of movement during your sleep is not 100% correlated with the stages."
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9l35dp | Why is Apple's spellcheck so much worse then any other spell check? | Technology | explainlikeimfive | {
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"What makes you think it's so much worse than the alternatives? Samsung's autocorrect is also legendarily awful. Unfortunately we're not very good at making these systems be both lightweight and smart enough not to get in our way."
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9l3j89 | How do MRI machines work? | I've tried reading the Wikipedia article and get lost having to read a separate article on _every_ term used in the info. | Technology | explainlikeimfive | {
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"Really oversimplified explanation: 1. suspend body in really strong magnetic field, forces water molecules to line themselves up in specific direction 2. at same time, zap water molecules in body with a radio wave, causes them to wiggle against magnetic field direction 3. wiggling water molecules give off their own radio waves, slightly different for each kind of tissue. Record it all & use computer to reconstruct 3D picture of it.",
"You know how a spinning top wants to be straight up? Even when you push it (a little) it is happiest when pointing straight upwards. The top even makes a little \"woosh\" sound when going back up again. Well your body is full of these tiny spinning tops of different sizes that are happily spinning around. You can make these spinning tops spin the same way using a really big magnet (they now all point the same way and spin at the same speed). Using a radio we can give some of the tops a little push and listen to the tiny \"woosh\" sounds the tops make to hear where they are located. Edit: If you want to delve a little deeper take a look at this (short) [book: MRI made easy]( URL_0 ) (link immediately downloads). It's written with non-technical people in mind and very complete and understandable given how insanely difficult the subject is.",
"Here is my ELI5 of this, because I think that the math of how this works is simply beautiful. You are made up of atoms. All different kinds of atoms. Lots of these atoms are hydrogen. Hydrogen is a special atom cuz it is so simple. It acts like a spinning magnet cuz it is so simple. Now normally, all your hydrogen atoms are pointed random directions, so you aren't magnetic. But if we put you in a strong enough magnetic field, the field it'll push and pull on these magnets. They line up. It makes all the atoms point up or down. But half of them are pointed up, and half of them are pointed down. So while they are lined up, they cancel each other out, so they still aren't magnetic. However, since they are lined up now, we can \"wack\" them with another magnetic pulse. This turns all the magnets to the side. Suddenly they are all pointed in the same direction! You become briefly magnetic, and we can listen to that with an antenna. However we only wacked the atoms, the big strong magnetic field still wants all the atoms to line up. And our atoms are still spinning, just like a top. So, just like a spinning top after getting wacked, the atoms rock around as they line up again. This causes them to ring. Because all the atoms are so simple, they all spin in approximate unison. If you are next to your neighbors you can sing louder and longer than someone by themselves. This gives us a weird coral note. By wack again in the middle of the note, we can get other notes, sort of like playing the song at a faster tempted. Sometimes we have to wack really fast (this is what makes all the noises in the MRI machine). Once we get a picture of all the notes over time, and with different pulse intervals, we get a chart of the chorus that your body made. By literally looking at the magnitude of the notes Harmony we can put together the picture of you!",
"If you put a really powerful magnet on something that has water, that water will act like a compass, and point to the direction of the magnet. Then you use another magnet to push that water, it causes it to act like a spinning top, and will rotate. With enough water spinning together, it behaves like a magnet itself, and you can read how strong of a magnet it is. Now next to different things, water rotates either quickly or slowly, that allows us to distinguish between one thing to another. That encompasses what's called NMR (Nuclear Magnetic Resonance). MRI is taking it one step further. We want only a small set of that water to do what we said, so we use another magnet to choose only part of it. How that's achieved is a bit more than 5 year old level, but basically we listen in to only what we want each time. We get a really distorted picture that we need to understand how to rebuild into a picture that you see. It's not like X-Ray where you get the entire picture in one go.",
"This is a fairly complex subject, which requires many years of education in Physics to properly understand. So the explanation given here is not wholly accurate. Electrons have a quantum-mechanical property known as \"spin\". This spin can be positive or negative (think of it as spinning left vs. right). Normally, this spin is undetectable - it doesn't change any of the measureable properties of the electron. When an electron is \"excited\" (meaning it has more energy than it's lowest level state), it will eventually \"de-excite\" and give off one or more photons (bits of light). These photons have very specific wavelengths, so you can measure the light and know exactly what the excited state was and how it transitioned back to its low state. You may have seen this yourself - have you ever seen the chemicals that you can throw into fire to change its colour? The energy from the fire excites the atoms in the chemical, and these chemicals were chosen because some of the bits of light given off are in the visible spectrum - so you can see the de-excitation. Now what does this mean for MRIs, and why does electron spin matter? When you apply a strong magnetic field, the energy levels of the electrons change slightly. One spin will have more energy, one will have less. This in turn changes the wavelength of the emitted light. The handwavey part here is that the MRI is able to combine all of this information together to be able to \"see\" what materials are where in your body. And because it uses powerful magnetic fields, metallic substances will shift and move and heat up as the fields change, which is why they're always so careful to make sure you don't go in with bits of metal, especially inside your body. EDIT: I've got this partly wrong entirely. MRIs work on the proton spins of the hydrogen atoms of the water molecules in your body, not the electrons. It still works based on the spins of the particles, but the excitation and emission here is flipping the spins to all be the \"same\", and the de-excitation is when the spins flip back.",
"yes its a small miracle which has to occur each time we get a \"routine\" mri for headaches or something. Scientific insights from multiple, at least 4, separate nobel prizes went into enabling us to look with beautiful accuracy through half an inch of solid bone at your brain in exquisite detail all without any ionizing radiation!",
"The simplest explanation is that we know magnetic lines travel in a specific path. If you control the magnetic source very very carefully and can measure any changes in its direction and strength very very accurately you can then use this to detect different things. It gets REALLY complicated but the general gist is we know what’s in a human body and how each thing acts (muscle, bone, etc) with a magnetic field. This allows us to pass magnetic lines through a person and get an image of what is where to a fairly accurate degree. That’s as best “like I’m five” I got for you.",
"To add to the physics explanations, the reason it is so useful to visualize soft tissue is that it is exploiting the spin of the hydrogen atom and two very abundant substances in the body are hydrogen rich: fat and water. Different imaging sequences use different timing to make different types of tissue to appear different. While X-ray and CT imaging are looking at density of tissue, MRI can characterize tissue based on the appearance on each sequence. Inflammation shows as water on imaging, think of swelling.",
"Everything consists of atoms, including you. Each atom in turn consists of a nucleus and some electrons flying around it. It turns out that many (but not all) atomic nuclei are actually magnetic, you can really think of them as absurdly tiny, absurdly weak bar magnets. The strength of this magnet depends on the type of atomic nucleus. The second-strongest nuclear magnets are common hydrogen nuclei. This is convenient because water contains hydrogen, and your body is mostly water. Unfortunately, nuclear magnetism is (almost always) too weak to just measure with a magnetic field sensor, we have to get more clever than that and use magnetic resonance. If you place a magnet in a strong magnetic field, it will try to align itself along the magnetic field. Now suppose this magnet can rotate freely in 3D, imagine it's mounted on gyroscope, and we misalign the magnet. The torque on magnet due to the magnetic field will cause it to rotate (\"precess\") about the magnetic field. The frequency of this rotation is equal to the strength of the magnet times that of the magnetic field - this is called nuclear magnetic resonance (NMR). There is very little friction affecting this rotation, it typically lasts for around one second. Now we have a rotating magnet, like you do in a bicycle dynamo or a generator. This means that if we wrap a coil of wire around that magnet, it will induce an oscillating electric current! We can measure this current using some electronics - this is the MRI receiver. Since we know the magnetic moment of a hydrogen nucleus, the frequency of this signal tells us the magnetic field at the position of the nucleus. The amplitude of the signal at each frequency tells us how many hydrogen nuclei experience this same magnetic field. But how do we misalign the magnets in the first place? That's easy, we \"hit\" it with an additional, weak magnetic field that oscillates at the NMR frequency - this is the MRI transmitter. The best picture for driving a resonator at its resonance frequency I have is imagine a child on a swing. You can get huge swings by giving it gentle periodic pushes at the right frequency. Ok, so we can measure how many nuclei experience which magnetic field strength, how does this help us? Well, the largest part of an MRI machine is actually to control a strong magnetic field, and magnetic field gradients (i.e. to make the field slightly stronger in one direction and slightly weaker in the opposite direction). This means that the NMR frequency spectrum alone can actually be used as a one-dimensional image in the direction of the gradient! But how do we get 3D images? We have to get clever with turning the three gradients and the MRI transmitter and receiver on and off at the correct time. For example, you can do \"slice selection\" along the z-axis by first turning on a strong gradient along z and then pulsing the transmitter at a specific frequency - then you only \"excite\" nuclei whose NMR frequency matches the transmitter frequency, i.e. those in a narrow slice perpendicular to the z-axis. While the nuclei are still rotating, you turn off the z-gradient and you turn on a weak x-gradient and turn on the receiver. Remember, you have a whole second to do this, so plenty of time. Now, the frequency of the NMR signal corresponds to the position along the x-axis. This is called frequency-encoding (along x). This gives you a two-dimensional image already, and there are more tricks with gradients to give you a three-dimensional image. Clever people have figured out how to time gradients, transmitter, and receiver to image more complex things like fluid flow. To increase the image contrast, we can make use of the fact that the time for which the nucleus precesses is different in different tissues. So by adjusting our timing sequence, we can suppress or enhance signal from different types of tissue. By using a \"contrast agent\", which for MRI means a strong, molecule-sized magnet, we can affect this timing as well."
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9l3s15 | Why does the moon look so big in person but very small through a camera lens? | Technology | explainlikeimfive | {
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"In reality the moon is very small as seen from earth. A dime held at arm's length will completely block it from view. The reason it appears so large when you look at it actually gives us insight into how the brain determines size of any object. It uses context clues and compared it to other objects in the field of view. But high in the sky, or on a distant horizon the clues are not typical, so your brain mistakes the size. A video of an Ames room illusion might help you grasp what I mean by context clues helping assign size to a object. URL_0",
"Depends on the camera lens. When you see those images of a gigantic moon over a horizon line, the photographer was using a very long focal length lens (200mm or longer), set at a fairly deep aperture for depth of field (f/8 or higher) on a very sturdy tripod and a long exposure.",
"Focal length and perspective. Wide angles male the moon appear smaller because it takes up a smaller percentage of thr image. While a telephoto shows the moon as a larger percentage of the image."
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9l40jb | From a purely technical perspective, what has to happen for the National Wireless Emergency Alert System to send text messages? | Technology | explainlikeimfive | {
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"Curious too. Because my phone didn't get the alert. So obviously something on the phone has to support something"
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9l4ib8 | How was the first computer language programmed? | Technology | explainlikeimfive | {
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"Think of how humans learn to write as we grow up. At first, we drew little pictures in crayon, right? A little tree or a doggie or a stick human. We knew that the picture was of a doggie, even if Uncle Elroy could never figure out our art. Then, we added details as we aged and drew more complex pictures of doggies, with collars and stuff, and our ability to draw got a little more complex. Then, the big moment: someone taught us simple strings of letters - hey, \"dog\" is the same concept as a picture of a doggie. And then we started stringing words together. That's how computers got language... except they started with on/off switches, not pictures. A computer is a tremendous number of on/off switches that you can string together in the same way letters can be string together to make a word. Two on-off switches can make up to four \"words\" - 00, 01, 10, and 11, when 1 is \"on\" and 0 is \"off\". Four switches can make 16 words! Add more switches and you get WAY more words. Some of those collections of switches can be places to put stuff, and others can be instructions, and others can be pointers, and others can send information to computer screens or printers... but let's just talk about instructions for now. You can set up an instruction set by telling the computer's electrical switches to do certain things when it hits certain patterns. For example, in a three-switch computer, if it gets switch combination 010, it goes and gets the settings of two other switches, and if it sees 101, it compares those two other switches to see if they're the same ON or OFF value. That's a computer program without a single english word in it. 010 010. Hard to read, so let's make it easier to read by making the computer do a 010 whenever we type \"get\", and 101 if we enter \"compare\". Now we have a computer language, with two words - \"get\" and \"compare\" - exactly the same as how we know \"dog\" represents the same thing as our little doggie picture. And you're on your way. More switches, more words, more complex languages... and so on."
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9l4xwc | Why do many 911 call recordings sound muffled and grainy when almost all other wireless communications sound clear? | Technology | explainlikeimfive | {
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"A lot of it is because they're putting several calls down the 911 line at once and have to use compression and multiplexing. There's a certain amount of bandwidth one can put down a wire at any given time. In order to put multiple calls on it at once, they filter out unneeded frequencies and change modulation and pitch and what not, and then will convert them back so they can be heard. That causes massive quality loss.",
"Many states redirect 911 funds to other endeavours. Usually that 911 fee that's on your phone bill doesn't go to the 911 services.",
"To add to all the other perfectly legitimate answers- sometime an audio engineer will add just a bit of hiss/pop/grain to a recording if it's *too* clear, because it's audio shorthand for \"you are listening to a recording\".",
"All calls over POTS do. It's a factor of the bandwidth used by the call, and the telephone system is set up for the 300-3000 Hz band to come through clear, so that's what the tapes are set up for."
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9l5l35 | how did the presidential alert work? | Technology | explainlikeimfive | {
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"Cellular networks have had a feature (for Amber Alerts etc.) for some years where they can send SMS messages to every subscriber unit (fancy term for \"phones\" and \"mobile devices\") in their entire network... with the capability to restrict it to a certain geographic area (e.g. only cells with the metro Chicago area). In this case it was an all American carrier, all coverage msg. _How does a carrier know your phone is in its coverage?_ Your phone is constantly listening for and talking to cell towers using the same cell technology its designed to support (GSM, 3G, 4G, LTE whatever). When you roam into coverage of a new carrier, the radios at the base of the nearest cell tower will query your phone for some identifying bits - your IMEI, carrier ID etc. There are boxes in the cell network which do the work of determining a) are you allowed to use _this_ network? i.e. is this your carrier or is there a roaming arrangement with your carrier? b) is this cell the one that gets a strongest signal to your phone? (if not find a better one and hand off the call to it). So not only does a carrier's network know your phone is within its network, it knows what cell you're currently talking to. Furthermore, triangulating comparative signal strength from adjacent cells can pinpoint your cell to within a few feet. So they know where you are. However, its unlikely the government is tracking you. The presidential msg was simply \"send this to every subscriber unit in your CONUS coverage network.\"",
"Think about a local radio station you listen to. They always ask callers where they are located because they are broadcasting a signal with a general range but have no idea of the recipient's exact location when they received it."
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9l68r5 | How does heart rate sensors measure oxygen saturation | Technology | explainlikeimfive | {
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"You're talking about pulse oximeter. And it's done by shining a red light and a infrared light into or through the skin. Blood with oxygen in it and blood without absorb this light differently. By measuring how much light is absorbed we can make a ratio of oxygenated to deoxygenated blood."
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9l7h9h | how is the government able to send a mass text to every phone? (Presendential alert) | Technology | explainlikeimfive | {
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"It's not a mass text, it's an emergency alert sent out by FEMA though an already existing protocol for distributing emergency alerts to mobile devices, in a similar fashion to AMBER alerts",
"All phones made in the last decade or so come with software pre-installed that lets the government send messages. Phone manufacturers have had to do this by law for a while now.",
"It's part of a test of the national emergency alert system. It's built into comms infrastructure like cell towers and other stations so national agencies like FEMA can send out a message if necessary",
"In the US, the system is called the Integrated Public Alert and Warning System (IPAWS): URL_0 It is a combination of at least four other types of emergency warning networks, some of which date back to the 1960s. The smartphone messaging support was fully implemented in 2012. The message is pushed out to the network and then any phone that is connected to it receives the message."
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9l8n7j | When sending a photo to a powered off mobile phone, where does the photo “stay” until it can be delivered? | Technology | explainlikeimfive | {
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"ELI5: The photo is stored on a server; specifically a Multimedia Message Service Center (MMSC) until your phone downloads the photo. & #x200B; Longer Answer: MMS messages are delivered using a combination of SMS and WAP technologies. When a mobile phone receives an MMS message, what it is actually receiving is an MMS notification message which it receives over SMS (WAP Push). This MMS notification message contains header information about the MMS message, and a URL pointer that the recipient must fetch in order to retrieve the content of the MMS message. This URL pointer is a dynamically generated URL for the MMS message content which is stored on the MMSC."
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9la0wx | Why haven't we explored the ocean? | Technology | explainlikeimfive | {
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"Basically: 1) it's so big 2) water pressure is a killer for equipment 3) so is visibility Everything that needs a laser, e.g. mapping the \"shape\" of the bottom of the ocean floor has basically already been done. It's the in-betweens, such as \"what is like life at this specific depth?\" that is hard to answer because you first have to come across an area with life in it at that depth (kind of like standing in the middle of a desert and deciding what way to turn to head back to town... you know it's out there somewhere, but where?). Then, you have to get equipment down there, have it survive, and have it capture something meaningful.",
"The ocean is very large, and a lot of it is dangerous to humans. Every 33 feet down you go, the pressure increases by 14 psi. Jump off a 10 meter platform and you'll feel the pressure on your ears and nose as you touch the bottom of the pool. The deepest parts of the ocean are over 36,000 feet, at that depth the pressure is about 15,000 psi. Even the smallest failure in the seals on the windows and doors will quickly become fatal. Bathyscaphe Trieste in the 1960s went down to that depth, it took them 4 hours to descend, and one of the outer windows cracked at around 30,000 feet. They only could spend 20 minutes at the bottom before having to surface again. Coming back up took another 3 hours. Not a lot of exploration time, much of the sea is like that, go down, maybe get an hour or two of bottom time, then come back up. and that's only the ocean floor. There's 30,000 feet of water above, and there's life at each depth level that lives very differently."
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9lh5hr | what is different about upload and download speeds that makes ISPs give you fast download but barely any upload speed? | Technology | explainlikeimfive | {
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"If an ISP can provide you with X amount of bandwidth, they then have to decide how much of it is divided into download and upload. To make your upload bandwidth higher, they would have to reduce your download bandwidth. The average user will value a higher download speed more, so that's generally what they provide. You can find ISPs that offer better upload to those who want it though.",
"I think the idea is so that you don't try to run a larte server out of your house or use it to create a guerilla network. With limited upload speed both are impossible.",
"Depends on the tech you're using. The real answer is the average consumer uses much more download than upload. For the ISP, it's a cost issue, and largely dependent on tech. For one, upload is generally cheaper for an ISP to provide because their peering agreements typically focus on how uneven their traffic is. If their upload is equal to their download it's generally free to peer. So extra data uploaded actually reduces the price of their download. Now, where tech matters is how upload is actually different from download. On a regular ethernet connection you typically have one pair of wires for download and one pair for upload, so you just get equal (symmetric) bandwidth because each side has an equal, dedicated, area. With shared tech it's different. Wireless tech might have a shared channel where you can send or receiver, but never both at the same time. I think most out there allow whatever direction you want at any point, but sometimes you want to enforce upload time and download times, so you might apply a policy that reflects actual usage to get the maximum utilization, and that would typically mean giving everyone more download than upload. With cable modems the issue is you have channels, 125 usually on cable TV, the modems get so many Mbps per channel, and will select a chunk and bond them together to get a connection. Each channel can only transmit in one direction, and each channel is shared with everyone on your node and TV. So in real life you'll have channels for example, 1-80 for TV, 81-99 for PPV, 100-125 for modems (all made up, each ISP chooses how they deal them out), of that they select 100-105 for upload and 106-125 for download. All the modems on the node use all those channels at once and share the available bandwidth. Doing this gives maximum bandwidth because if it was a 50/50 split you'd be short on download and have loads of unused upload."
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9li9qp | how do we know that a dinosaur had a bone fracture while alive? | How is it that paleontologists are able to determine that a dinosaur was injured while alive and not a case where the body of the dead animal was crushed after death? | Technology | explainlikeimfive | {
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"Because bones grow back together imperfectly, leaving telltale signs like offsets or calcium seams.",
"You can get boo boos on the inside that heals to a scar too; no matter what race you are or when."
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9lin2q | What is the difference between primary and secondary, and difference between master and slave hard drive? | I looked up on the internet but can't really find anything that I can understand. I know that there is primary master drive (on all computers, and the rest as optional drives (primary slave, secondary master, and secondary slave). But what's the difference? | Technology | explainlikeimfive | {
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"Master and slave? In 2018, it's something to be ignored. It's a relic of ancient PATA two-inch-ribbon cable technology, when the cables were so big they had to connect not one but *two* hard drives to the motherboard. In fact, it's a relic of the earliest days of that technology when the drives had to be instructed whether they were \"master\" or \"slave\" by placing a little jumper across the \"master\" or \"slave\" pairs of pins. Later did they learn to figure out if they were on the first or second position of the PATA cable, and configure their own damn selves. Now everything is SATA! And SATA is one for one, and SATA doesn't care about ordering. Everything is configured in the BIOS. Disclaimer, I was born in '95 and invite any old timers to tell me where I'm all wrong.",
"Not only were there Master and Slave on the IDE cable (with matching Master/Slave jumpers on the drives), but there were usually always two IDE ports: Primary and Secondary. You'd usually always install your bootloader onto the Primary Master drive. The boot order otherwise was usually: Primary Master Primary Slave Secondary Master Secondary Slave",
"In the simplest terms, Primary (master) is the drive that contains your operating system, or \"boot\" drive. Secondary (slave) is usually used for extra storage. Back in the day, you indicated which drive was the primary by setting a little jumper switch on the drive, which would let the computer know which drive contains the Operating System when it starts up. Edit: grammar..."
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9liqwi | How does a projector project black colour on a white screen? | Technology | explainlikeimfive | {
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"text": [
"It doesn't. It projects nothing and since there are bright colors all around it, your brain interprets it as black but it's actually the color of the screen with no light on it."
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9ljj5z | Why do you need "administrator permssion" on your own computer, and why arent you already on administrator mode? | Technology | explainlikeimfive | {
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"It's a safety feature. Even if you are an administrator it's dangerous to be in \"administrator mode\" all the time because then any program you run could make changes to any part of your system, potentially without your knowledge. A lot of malware did this. By requiring you to explicitly give permission when you or some program attempts to make administrative changes, it makes sure you actually intended it.",
"It’s a countermeasure to stop programs from installing without your permission, and if you have other users on the PC you can prevent them from installing programs without your permission. All of this is basically just added security built into windows itself. Also, you can with a little bit of tweaking in the user settings turn this feature off."
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9lk85b | Please explain to me the recursive neural network model in Machine Learning | Title Thanks guys | Technology | explainlikeimfive | {
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"So the goal of a recursive neural network is to make a lot of inputs into a small output. Example: I have an image: 50*50 pixel (2500 pixel total). I want to know if the image represents a tree (Yes/No). So from 2500 colour-values I want to go back to just two possible outcomes. First of, we have to realize that a colour-value is nothing but a number. (Typically three, how much red, how much green and how much blue do you need to mix in order to get that colour). Additionally \"Yes / No\" can also be represented as a number. (Yes = 0, No = 1, for example). This means our problem \"Is the image a tree?\" just is: Calculate the correct number (for yes/no) out of a lot of numbers. This is done like a tree (from graph-theory, think a pyramid). At the bottom you have a lot of numbers. They are filled with the colours of your image. Above them in the next part of the tree you have fewer numbers. They are calculated by weighting the numbers below. (Simplified: Number_1 = 0.5*Colour_1 + 0.3*Colour_2). 0.5 and 0.3 would be the weights here. Those fewer numbers get even fewer in the layer above and then again will be fewer until only one number is left. If the number at the top is smaller than 0.5, then you say the image is a tree, otherwise you say it is not. This would be a recursive neural network. The machine learning part here is to actually find the optimal weights, so your calculation results in a number smaller then 0.5 if the image actually shows a tree. This is done by feeding the network testdata which is in turn used to calculate good values for the weights (because those determine your endresult.) This calculation is done by picking the numbers in a way your prediction is correct as often as possible for the testdata. The idea is, that if the numbers work well for a sufficient amount of testdata, they will work well for new data as well."
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9llap5 | What is Passenger Load Factor (Occupancy rate) and how does it help an airline? | This is the wikipedia explanation but I need something more explanative. "Passenger load factor is an important parameter for the assessment of the performance of any transport system. Almost all transport systems have high fixed costs, and these costs can only be recovered through selling tickets. Airlines often calculate a load factor at which the airline will break even; this is called the break-even load factor. At a load factor lower than the break even level, the airline will lose money, and above will record a profit. " | Technology | explainlikeimfive | {
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"It is a fancy way of saying “how full is the plane”? Full plane make big money Empty plane make small money Airline prefer big money",
"The number of passengers they need to still make the trip profitable. Imagine you drive from one city to another and it costs you $20 in gas. If you invited people to carpool with you in exchange for $5 each, you would need four passengers to break even with your fixed cost of the trip. Any fewer and it still costs you to take the trip."
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9lmolw | What’s the difference between internet browsers. Aside from appearance and customization, what causes the mechanics of different browsers to work better on certain websites? | Technology | explainlikeimfive | {
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"So, technically the components of websites (HTML, CSS, and JavaScript primarily) are standardized, but it's still up to the browser makers to actually implement those standards. These standards are being updated all of the time, so some browsers that are quicker to update and designed to be fully featured (e.g. Chrome, FireFox, Edge) will support these updates while older browsers or ones designed to be light won't support these updates. A web programmer has to know what sort of features are supported while writing code in order to support their target web browsers. Sometimes programmers will target a specific browser and not update their website to work well with other browsers.",
"Browsers have something inside them call a rendering engine for drawing the HTML page. A surprising number of browsers use an open source technology called WebKit to do this. WebKit was developed by google and put in the public domain. The Chrome browser has moved on from WebKit. Safari uses WebKit. Firefox uses a technology referred to as Gecko. It's the difference in these and other engines that affect the speed of your browser and any (fewer nowadays) differences in the display of pages. Another factor is how the javascript is executed by the browser. Or better what javascript engine is used in the browser. There are a dizzying number of these used in different browsers. Here is a deeper description. URL_0 Then there is the CSS engine used by browsers. For some it's integrated with the Browser Engine. Others not. It's complicated. You take the permutations of these and you get the wacky world of browsers and why some work better and others not.",
"TLDR: Some browsers will run faster, have more features (for the user and developers), and be more considerate of you’re privacy than others The browsers purpose is to show you what the people who made the website want you to see. In order to do this, they have to convert the stuff coming over the internet to things you can see and do on the page. The process, however, is not completely standardized. Modern browsers like Chrome, Safari, and Edge have more “optimized” ways of converting this that allow it to do things faster and more efficiently. They also implement features that make programming those websites easier so developers will make websites optimized for that specific browser. This is why a lot of websites just won’t work or run very slowly in Internet Explorer, because it doesn’t have the latest and greatest features that modern browsers do. Browsers will also have more features for the end user in plain site. Chrome, for example, has a HUGE selection of “browser extensions” that people can download to make the browser more suited to that individual. A lot of modern browsers will also allow syncing of website passwords between devices as well. Browsers will also disclose private information differently to websites. The latest version of Safari, for example, boasts only showing the website what it needs to know so they can’t track you. Chrome, on the other hand, is ran by Google so you can imagine that a browser made by an advertising company is going to want to show a little more information.",
"It's like the difference between Ford and Toyota cars. There is a common specification, the laws that regulate cars in this analogy, but different products are built and marketed to decision makers. Sometimes the specifications are narrow, the laws on seat belts or air bags in the analogy, and all the products are about the same. Sometimes the specifications are broad, so you have faster cars and slower cars or electric cars and gasoline cars and diesel cars. Some manufacturers have business arrangements that they use for leverage in the market, like Toyota Motors Financing in the analogy. Like cars, browsers are different because they have different parts inside and different engineers made different choices in their design and construction. Different products exist because there is a competitive marketplace and several suppliers are competing to produce the product that gets them market share most cost effectively."
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9lnksl | How come when 3G was new it was cutting edge fast connection but now that LTE is out whenever I only have 3G connection nothing works at all? | Technology | explainlikeimfive | {
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"When LTE is out it's either because of congestion or bad signal strength. So when you drop down to 3G, so are a bunch of other users. Also, most towers upgraded to 4G LTE, leaving a small portion of its capacity for 3G.",
"For the large part, if your phone is falling back to a 3g service, it is an indication that it is unable to establish an LTE connection to the same towers. 3g bands tend to carry slightly longer, but at those distances the quality of the connection isnt great to begin with. 3g services aren't used as a primary network connection because WiMAX and LTE exist now.",
"A couple reasons... fewer devices were competing for bandwidth between devices and cell towers back then. The speed at which smart phone has increased -- numbers and use per device -- has skyrocketed over the past 5 years or so, and the addition of new cell towers can't always keep pace due to zoning, NIMBYism, time and cost to install, etc. Additionally, apps, websites, etc. often want to take advantage of the best technology capabilities, so they build apps and sites that are more robust, doing more, use higher rez images and video, do things that requiring more bandwidth and processing. Which is great if you've got a modern device on a fast connection but can bog down if you're trying to use when there are limitations on connection speed or your device is a couple years old."
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9lpab9 | Why do computers slow down and take longer to perform even basic functions as they age? | My macbook pro is from 2012 and was a high end 13 inch model at the time. I've had one major repair done to it. It has slowed down a lot. Video editing is difficult at best and takes so much longer than it should in general. Even basic emails/chrome use has become slower. I know planned obsolesce is a thing. I haven't updated it past OS Sierra. Do other computer companies do this too? Why does it happen? What is happening? | Technology | explainlikeimfive | {
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"It is because today’s software requires better and bigger hardware to run. When you bought the device it was top notch, but now software is designed to run on hardware that is a lot more powerful.",
"Don't know if you've upgraded the software, but Chrome for example becomes is a memory hogging beast.. Each version getting worse... But that also has to do with developers targeting newer hardware... At some point your old machine can't handle the requirements of the new software",
"Your computer isn't a single tasker. It's multitasking. Every program you have running is available to be wanting to do something. So while you may have chrome in foreground, MacOS updater, Adobe Acrobat updater, time machine backup, etcetc are all running in the background. In addition, your cpu is auto controlled to be slower if it's getting hot. If you've not cleaned the internal heatsink, it could be not dissipating heat properly. If addition, parts of your computer do wear out. Hard drive, memory do wear out from usage and heat cycles. That means your computer hardware is technically less capable than it was years ago",
"There's a number of factors involved here 1. OS Wear and Tear - OS's generate and accumulate a lot of garbage data during their regular operation. Applications, drivers, services, updates, etc. The older a computer gets the more crap is usually running in memory. These changes accumulate incremental performance hits. 2. Applications Improve while the hardware doesn't - Updated versions of applications are built to take advantage of advances in hardware. So updating an app can make it use more CPU + memory. That fancy new GUI interface sure does love to eat RAM! Also on a side note developers are really notorious for making code that uses resources very inefficiently (because RAM is cheap right?) but that's a different argument entirely. 3. Lack of maintenance - The average person doesn't do any regular maintenance on their machine. Clearing cache, defraging hard drives (irrelevant with modern SSDs) uninstalling old apps, stopping services, etc. A computer is like a car. If you don't change the oil and top up the fluids regularly it will keep on running but it sure isn't good for it. 4. User perception - Truth be told a lot of what I see is people complaining about their machines performance compared to new fangeled laptops and tablets that their friends + coworkers + family are using. A freshly imaged PC with Windows XP runs just as fast as it did when it was brand new. But that was 10 years ago, and you're used to better performance today.",
"***:Software*** Optimization and efficiency are moving targets with computers. The older an installed program is, be it the operating system or really anything that updates, the farther your system is from stock behavior. OS patches, application errors and subsequent hotfixes, etc are all written and QA'd with the median of configurations in mind. In an enterprise environment, we call this slowdown Image Drift or Configuration Drift. Links: URL_0 URL_2 ***:Hardware*** In addition to heat related issues, blown capacitors, or other actual physical malfunctions, one thing that people have not mentioned is microcode patches to the CPU. Spectre and Meltdown both have a direct impact on CPU performance and this variable didnt exist when the computer was new. These are near-permanent changes to the hardware. Links: URL_1 URL_3"
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"https://superuser.com/questions/375160/which-malfunctions-cause-old-computers-to-slow-down-and-crash",
"https://blogs.technet.microsoft.com/secguide/2008/06/30/configuration-drift/",
"https://www.phoronix.com/scan.php?page=article&item=linux-419-mitigations&num=1"
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9lqrvl | How does a computer know what the programming code of an app means? | I know that the words "draw" or "add" means certain things. Still, I cannot comprehend the mechanisms that turn code into executable stuff on a computer. How do programming anguages translate into I's and O's that work on the computer, and how do they know what to translate? | Technology | explainlikeimfive | {
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"Each language has a special program called the Compiler to convert it into binary, or an interpreter to do the same as the program runs, for every line one at a time. The latter takes longer, but is less complicated for the programmer.",
"on its most fundamental level a computer CPU has a set of containers you can put numbers in (called registers). some are used to hold the address (a number) of a place in memory to get data from, others hold the place in memory where the CPU is getting instructions from. others just hold numbers that are being involved in sums and operations that actual execute the program being run. the way data flows from memory to these container in controlled by binary switches. (activating a certain transitor switch will cause the address in container \"A\" to be retrieved from memory and that number put into container \"B\" for example). this is simplified, but the basic gist. every clock cycle, the current instruction that the instruction pointer is pointing at is loaded into the CPU. its particular combination of 1's and 0's act like switches. some cause pathways to be activated and data to be retreived as mentioned above. other combinations of switches will cause, for example, number contained in \"A\" to be added to number contained in \"B\", or number in container C to be put into memory pointed at by container D, or change the program instructor to whatever's currently held in container E. (which has the effect of \"jumping\" somewhere else in the program) doing these basic flow controls causes each instruction to be physically performed and the results stored or acted upon. each of these operations has a basic physical reality (literally the presence of a \"1\" in an instruction in a certain place causes a certain transitior to be opened which causes a point in memory to be connected to a point in the processor) some of these basic operations can be scaled up and [visualised using mechanical systems like wooden switches and ball bearings for data]( URL_0 ). this is how a computer fundamentally processes information; it's broken down into a small set of very basic operations that are executed very rapidly and add up to very complex behaviour. but fundamentally the physical process of computing can also be represented at everyday scale mechanically. it would just be really impractical to do so!"
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9lsk5i | What is the difference between TCP and UDP? When and why do you use which? | Edit: Thank you everyone, this really helped! | Technology | explainlikeimfive | {
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"TCP is a robust protocol. I send you packet 1, you acknowledge, I acknowledge your acknowledgement, I send packet 2.. This is great for ensuring that a packet arrives but adds overhead and sometimes you don't need to ensure a packet arrives UDP is a bit more YOLO. I send you packets 1-999 in rapid succession, if you miss one then you can let me know and I *might* resend it, I might not. UDP is commonly used for streaming video to make the best use of bandwidth. Worst case you lose some packets and you get some blocky artifacts in a few frames, no biggie. I could tell you a UDP joke, but you might not get it",
"Theres a visual that I always reference to describe that behavior of packet flow: TCP = drinking out of a water bottle UDP = pouring water in your mouth",
"The short oversimplified answer is TCP has a way for the recieving end to send an acknowldgement back that it got the data. UDP just sends it and hopes for the best."
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9ltjvr | How and why is Flash a security threat on a computer, and what makes it different from other programs? | Technology | explainlikeimfive | {
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"There is a major difference and that is that the program was downloaded and executed automatically when you loaded a web page. You need to download and install regular programs so is it a lot harder to convince someone do that compare to be executed automatically. The page was not necessary one that that the hacker had controlled over as you could include flash i a advertisement on another site. But compare to a program you download Flash was more secure. The program was not executed nativ but was run in a virtual machine with limitation. They can be relative secure like the one that java script in your browser. But flash could do more and was not developed with enough security in mind so there was may problems with it and many exploits was discovered. So any exploit that was discovered could be used in a ad on another website. People did not update fals when there was a new version so know and patched exploits could be used for a long time."
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9lx3wi | How do files/code get corrupted? | Technology | explainlikeimfive | {
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"Corruption happens for lots of reasons. Think of each file as a million light switches. The order in which the light switches are on or off tells the computer what is inside the file. & #x200B; If the light switches were stored I'm a giant steel box then whenever you went to look at them they would be in the same order. In a perfect world, someone could open that box, copy the order of switches into a new box, and then close their box for a perfect copy. & #x200B; Imagine if you started to copy the switch order to a new and something interrupted you, or the box you were copying from was removed. If this was towards the end of the switches, you would think you might think you had a copy, but would be missing pieces of it. This is how files can get corrupted while copying though most programs have a method to verify the switches were copied correctly. & #x200B; When something on your computer is running, it stores those switches in a temporary box that is really fast to change, but also really sensitive. Imagine if you shook the box with a bunch of rocks in it. Theres a chance that while you're shakeing the box, one of the rocks would hit a switch and change it at random. This is what can happen with data while it's in memory, sometimes background radiation can hit one of the electrons and change it. & #x200B; Every time you save or retrieve data there is a chance that someone along the line some piece of hardware will incorrectly read the data or incorrectly write the data. Computers do a lot to check if this happened and correct it, but occasionally something will cause an undetectable issue and that is viewed as corruption.",
"Underneath the model of digital signals, it's really an analog world. Circuits assign meaning to low voltages (zero) and high voltages (one), but voltages near the middle will look like zeros to some circuits and ones to others. Circuits have amplifiers that try to take small analog errors on their inputs and eliminate them, driving outputs back to voltages that are clearly ones and zeros. However, these circuits are themselves built in an analog world, where the threshold between ones and zeros, amplifier gains, transistor saturation, logic function delays, power supply voltage and similar characteristics vary due to manufacturing variation, focusing error, microscopic dirt on the chip and the like. Signal-to-noise ratios are kept normally high enough that digital errors are rare, but variations from ideal behavior large enough to cause errors happen. Most computers make no attempt to correct individual errors in computation, except for data stored in memories and possibly in caches. One particular problem that leads to corruption is circuit delays. As discussed above, after manufacture, logic circuits have varying delays for many reasons as described above. We build computers to be fast. Really fast. Really, as fast as we can make them. We rely on clock signals to capture logic signals once the circuits have computed a result, but a circuit that's too slow will cause the wrong answer to be captured when the clock signal arrives. That's why overclocked computers can result in corruption - they're being operated beyond the point at which the logic signals have settled to their stable values. Disk drives have servo circuits that try to keep the read and write heads on tracks for the best signal-to-noise ratio, and when the heads are little out of place, the drive reads values that are a little off, and once a written zero comes back as a one, or vice versa, raw data has been corrupted. Disk drives in particular rely upon error-correction coding, so individual errors and some combination errors in the raw data can be detected and corrected, but once the error rate gets too high, that corruption gets passed out of the disk drive.",
"the other commenters already listed the most common things when it comes to hardware/software failure, but there's also another kind \"sorry, the data was corrupted\". it mostly occurs when certain service providers (say, ISPs) realize they fucked up on something they were forced by law to record, for example, blatantly lying to their customers. there seems an extremely high chance of data corruption in this scenario."
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9lxi0l | What causes color to change on a laptop when you tilt the monitor? | I've noticed that the color pink on a laptop screen can become either red or purple from tilting the monitor a certain way. What causes this and how does it work? | Technology | explainlikeimfive | {
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"Your laptop utilizes a liquid crystal display, or LCD screen. Quick physics recap. Light is a wave. This wave can go up or down, or left or right, or any combination. An LCD screen works by first filtering the light so that all light goes up/down. Then, the light is send through liquid crystals. These have the interesting property that they change the orientation of the wave depending on whether or not an electric current is applied. After that, there's another polarization filter. So, to recap. There's 1 filter, then a crystal that can change the orientation, then another. By deciding whether or not you change the orientation, you can make sure that the light passes, or doesn't pass. Now, to answer your actual question. Under certain angles, this may not work. What's happening is that you're seeing light that isn't supposed to pass through the filter, and not seeing light that is supposed to pass. Edit: This is a much better, more detailed explanation. URL_0"
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9lxl07 | How does a Credit Card machine work during flight? | Technology | explainlikeimfive | {
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"It doesn't, it connects when the plane has landed and all the payments are processed then. This also means you can use a card with no balance and it will be approved. A lot of budget airlines only accept credit cards now for this reason."
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9lyj80 | Why are horizontal monitors the norm when most of the content is scrolled vertically? | Technology | explainlikeimfive | {
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"That's the way we see content best. Our eyes pick up a wider field of vision than long. So it feels unnatural to see things with a longer field of view than wide. It's why when you go watch an Imax the screen fills the whole rooms walls but doesn't stretch as high into the roof of the building.",
"We have two eyes, one beside the other on a horizontal plain. If our eyes were set on a vertical plain, vertical monitors would make more sense."
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9m17en | Why does installing files take longer than uninstalling files on computers? | I had the Anaconda program used for programming platforms like Python but recently uninstalled it. I noticed that the uninstall took < 5 minutes whereas when I first installed it, it took ~20 minutes. It led to me questioning why installs take far longer than uninstalling programs from your computer, especially if the files are hold data in the GB range. | Technology | explainlikeimfive | {
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"Uninstalling, or just generally deleting files, is a very quick operation. Instead of actually removing the data from the disk, it just removes the file from the filesystem and marks the space where it used to live as available for reuse. This is why you can \"undelete\" files. You just have to figure out which blocks on the disk used to hold the file and recreate the directory entry. You have to be quick though because some other file might get written over those blocks.",
"When installing a program, the files must be written to disc, and the usually aren't in place already (aka they must be extracted from a compressed archive or downloaded from the internet.). Uninstalling a program usually just involves deleting a few files and changing a few references to no longer include the program, which is a lot less work to be done, since the files themselves don't have to be overwritten."
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9m1gn8 | How Do Those Mugs That Never Spill Work | How do those cups that cant be tipped over but can be lifted up like normal work | Technology | explainlikeimfive | {
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"Not very well. It's basically a suction cup on the bottom that holds it in place for minor taps, but lifting it releases the suction. If you've seen a cup with a sort of lever for fast release like on a windshield GPS or something, it's exactly like that.",
"Maybe you mean the ones that have an extremely wide bottom but a narrow top? Can you link to an image or example?",
"I'm so disappointed. I thought this was some Executive Desk Gadget that microscopically controlled the cup so you literally could not spill it. So this is very disappointing."
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9m1pxx | Where do files go once they’re deleted? | Technology | explainlikeimfive | {
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"Initially, nowhere. When you delete a file your PC simply deletes the entry in its tracking system that tells it where the file was stored. The file is still technically there until the PC needs to save something else later, and overwrites this now “free” space. Edit: To take this to ELI5 levels. Your hard drive is like a big warehouse, and your computer keeps a big list of exactly where everything is stored. Works haul items to and from the warehouse as needed, using that list. When you delete a file, you remove that item from the list. The stuff is still setting there though. Later though, when the workers need a place to store new data, they look at the list, see that space as empty, and blinding dump the new stuff into that space (which in this case magically makes the old stuff disappear).",
"Basically all it’s doing is allowing the computer to write over it. When computer store something they store a series of bytes that are not allowed to be written over. When they are “deleted” the bytes are allowed to be written over, basically causing the “file” just to be changed to something different"
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9m3aay | What is system administration? | As far as I know, system administration is about maintaining, configuring and extending software, in contrast to building it from scratch. But am I missing something? What exactly does a system administrator do? | Technology | explainlikeimfive | {
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"It's a somewhat dated term in modern computting but basically it covers the maintenance of servers used to host applications and environments. That maintenance includes supporting and repairing the underlying hardware if needed (which may be coordinating service calls). In general its making sure the servers are running correctly. Tasks can range from basic configuration management all the way through writing and deploying software (either the coffee the syaadmin had written or software from vendors or software the company that owns the systems writes). Creds: I've been a sysop, system administrator, systems engineer, and SRE over the last 30 years. Humor bit: basically all those are different names for the same job. :)",
"In a ELI5 sense, think of a sysadmin as a bus driver. He hasn't built the bus (that's the engineer's job), but he has a pretty good idea of how it works, knows how to drive it and can change a tire if needed or maybe hot-wire the ignition if it won't start properly. He knows how many passengers can safely ride the same bus at once, and over time he gets to know all the little quirks of the engine and so adjusts his driving style accordingly. He is in charge of keeping the bus running along smoothly, as otherwise the passengers (i.e. the users) will start complaining. If the ride is bumpy, he might be able to adjust the suspension in order to fix the problem. But if the suspension has been built in a way that doesn't let you adjust it, there's nothing he can do about it either. And if the bus needs an oil change every few days, all he can do is stock up on oil so he has enough when he needs it. So when enough problems accumulate, he can try to convince his boss that they should buy a new bus."
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9m3hq7 | What is a capacitor? How does it compare to a battery? What are it's advantages and disadvantages compared to a battery? | Technology | explainlikeimfive | {
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"To add on to the other answer, capacitors have a much lower charge density/energy density than batteries. Meaning that a capacitor of the same size/weight as a battery would contain far less energy. Capacitors, however, are able to discharge the stored energy much faster than batteries (hence they are used in camera flashes).",
"A battery can be thought of as a capacitor, with a chemical storage method of replacing the charge. A capacitor has two surfaces, separated by a dielectric so charge can't jump from one surface to another. The surfaces have a different amount of electrical charge, with one having more electrons, and hence being more negative than the other surface. As electrons flow from the surface with more electrons, through the circuit, to the surface with less electrons, the voltage across the capacitor drops very quickly. A Battery is similar, with the follow exception. The barrier between the electrodes is an insulator to electrons, but allows ions to flow between the electrodes. When an electron moves from the negative electrode, a positive ion (atom or molecule that loses an electron and now has a positive charge) moves through the barrier to the positive electrode. The incoming electron from the circuit couples up with that ion, and the ion becomes a neutral atom or molecule rather than an ion. This way, even though the battery is providing power, the net charge between the electrodes stays constant, until you run out of atoms or molecules to Ionize for new electrons. If you recharge the battery, you move those ions back to the negative terminal. BTW, this also works with a negative ion moving from the positive electrode to the negative electrode, but for the ELI5 version, you don't have to worry about it. So, in the capacitor, the voltage across the capacitor drops dramatically. In a battery, the voltage stays constant until you run out of ions that carry the balancing charge.",
"A capacitor is less efficient at holding a charge when removed from the circuit it's been installed in. Batteries can be easily removed from an electrical circuit without losing their charge."
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9m3xbh | How do scales measure body fat + hydration + bone + muscle? Is this just bullshit or is there some truth to it? | Technology | explainlikeimfive | {
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"The type of scale you're describing generally measures the electrical resistance or conductivity of your body, which combined with your weight and some preprogrammed models lets it make an educated guess at what your body consists of. If your body was made of only two tissue types and all human bodies had the exact same shape, this would give a perfectly accurate result. As it is, there's no way to tell the difference between a person with extremely fat legs and a skinny upper body versus someone with lean but average legs and an extremely muscled upper body. The scale assumes you're probably at neither extreme and so gives you the hydration etc. numbers that the electric conductivity would indicate for an average person. Oh and I should mention, the sweatiness of your feet has far more influence on the measurement than your actual body composition."
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9m5fcu | What is the process for movies to film scenes at major sites that are usually crawling with activity? | Film crew of reddit how are scenes filmed like in 28 weeks later when the two kids are traveling across the bridge and there’s no other cars or even boats moving for that matter? Or another example is the amazing spider man 2 fight scene in Times Square. Just curious how hard it is to do this and what’s the process to do this. | Technology | explainlikeimfive | {
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"Money. They just pay into the local economy and get to shoot there. The city area will get notified in advance. City workers help close off the area needed while filming as everyone flocks to watch the filming happen. Win win for all.",
"You file a permit with the city and pay them tons, heaps of money for the right to film (which the city is happy to have free money), and you generally film in the early morning daylight when traffic is lower, if possible. The city and police along with you will block some of all of the area to shoot then reopen it as normal. There’s nothing too intense about it, cities have very standard stuff in place and are used to doing this.",
"I addition to the other comments, which are all correct, another trick they use is to find a street that looks similar to what you need, and dress it up until you hit the 12 foot level and then do CGI above that. I read about that technique being used on the HBO series \"The Deuce\" which mostly takes place in the seedy version of Times Square in the 1970's. Since it's all cleaned up and a shiny friendly tourist spot now, there was no way to shoot there even if they did rent it all out. So they just found other areas of Brooklyn, Bronx, Queens, etc which had the same 1970's look and then CGI'ed the tall buildings. CGI is getting better and better every year and it's gotten to the point where you can't really spot it anymore in scenes with buildings, etc. It's usually still painfully obvious however when they try to do animals or people or anything moving.",
"For Hollywood movies in big cities they do pay. However, in smaller cities sometimes you can just ask and the city will effectively pay YOU to shoot in their city. My dad makes movies as his hobby (SUPER low budget) and he got a city in his area to block off a street, give him access to (parked only!) police cars with the lights on, and access to a few normally restricted areas for his latest movie. All he had to “pay” was to give the city manger a 5 second cameo. As with all things real estate, it’s just location, location, location.",
"For 28 Days Later where they filmed in the middle of downtown London ([ URL_0 ]( URL_0 )) They filmed at 4 in the morning before major traffic hit. They also blocked off all their places, shot a take, let a bunch of cars through, re-blocked, and over and over again. So they only really have like 30 seconds at a time. They were also able to use multiple small cameras to get multiple angles in one take which cut down on production. It helped in that specific film that they were shooting on MiniDV cameras so they didn't have to spend a million years on setup, they could go quickly and nimbly from shot to shot without doing a bunch of lights. Contrast that to the opening of La La Land where they had to wall off the freeway AND put a bunch of cars there and a crane AND shoot a massive musical number. That took 3 days of shutting down a major LA freeway. If you are thinking that that is insane because the city loses major traffic arteries etc, you're right! The locals just deal with it."
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9m9vtj | Difference between copy constructor and assignment operator in object oriented programming | Particularly C++ | Technology | explainlikeimfive | {
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"A Copy Constructor is used to initialize a newly created object with data values from an existing object. So that's Existing --- > New Assignment is simply writing over data values of an existing object, so that's a relationship between an Existing object and an Existing object."
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9mb2qe | Firewalls | What is the process of making a firewall for a website? | Technology | explainlikeimfive | {
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"A firewall controls the flow of traffic into and out of a network based off certain security policies. With regard to a website, a firewall would allow all, or most addresses from the internet into the network and route them to the computer that contains the web pages. It will only allow that traffic to communicate over a particular port, based off of the needs of the site. Think of the bouncer at a bar or night club that's 21+. You can come in if the bouncer checks your ID and you are the right age. Otherwise, they'll stop you. Also, he allows you into the club, but you aren't allowed to go into the managers office where the safe is."
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9mblmu | Why is an i5 processor faster than an i3 processor if they have similar clock speeds? | Technology | explainlikeimfive | {
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"Multicore can theoretically improve performance. In practice, it does not because scheduling multiple cores is a nearly intractable problem on a general purpose O/S. If you look at the CPU time on your multicore processor, you'll notice almost all the work is being done by a single processor. Multithreading is a much more significant element. What multithreading allows you to do is have multiple threads ready and when one thread stalls, the other can consume CPU time that would otherwise be wasted. Caching is even more significant. The reason those threads get stalled is largely due to 'cache misses'. The memory in your L1 cache is hundreds of times faster to access than your main memory. As a result, any time a program requires a read from main memory, you're left with your CPU idling for hundreds of cycles. Better cache performance and techniques like multithreading (above) and branch prediction can prevent this. Specialized sub-processors also help a great deal. Unlike multiple generic processors, sub-processors solve the scheduling problem by forcing the software to run on certain, specific processors - processors optimized for those sort of problems. Vector processors for graphics are the most common example, but floating point math processors predate them. In the future, you might see even more of these sub-processors to deal with other common, time-consuming tasks. Smaller footprint and more efficient instruction sets can also make processors faster. It may seem like electricity moves pretty fast, but saving a few millimeters here or there makes a huge difference when you're talking about gigahertz speeds. Lower power can also help. A major limitation of modern processors is heat. Lower the power and you lower the heat. Unfortunately, you also increase the interference - which can be addressed by better channel coding (within limits).",
"Think of the processor as a workshop. Inside the workshop, woodworkers represent the cores of a cpu. Multiple workers are going to get jobs done faster than just one guy In fact, it has been proven that multiple, slower workers will complete tasks more efficiently than just one really fast guy. This is why single core CPUs with seemingly high clock speeds have long been outdated by slower clocks with more cores.",
"The exact reason depends on which version i5 and i3 you are talking about but generally it comes down to more cores. The i3 may have the same clock speed but the i5 has more cores which means more workers. Think of cores like number of cylinders in an engine. A v4 engine could have the same rpm as a v8 engine but generally the v8 will have a lot more power at the same rpm. Don't let them fool you with talk of threads, hyperthreading (possible number of parallel processes basically) only adds about 30% performance. So the i3 could have 4 threads and the i5 could also have 4 threads but since the i5 has 4 true cores it'll be a lot faster than the 2 core 4 thread i3 since 2 of the i3 threads are not true cores."
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9mdb64 | Why are computers able to perform much more complex calculations than we are, even though they aren't as powerful as our brains? | Technology | explainlikeimfive | {
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"Computers are actually performing *less* complex calculations than we are. Our brains are not wired to perform simple tasks precisely. They're wired to perform complex tasks imprecisely. That's why we can instantly identify a photograph of a famous person, but it takes tremendous computing resources to do so. It's also why you can approximate the square root of a 10-digit number almost instantly but can't fill the digits beyond the first one or two with any precision.",
"Computers don't really do complex calculations. Everything they do comes down to some combination of these: * If the input is off/on, do/don't output a signal. * If input signal A is on and input signal B is on, then output a signal. * If either input signal A is on or input signal B is on, then output a signal. * Store a number. * Retrieve a number from store. What makes them good at calculations is: * The combination of these operations into complex programs (written by humans) * They can do billions of these operations a second * They don't get tired There are many complex operations that *we* are much better at than computers, such as recognising millions of different objects, understanding spoken language and making art. These are much, much harder to break down into the simple steps above.",
"Computers only do very simple single operations in chains, which can then form more complex calculations at as an end result. There are two main different types of instruction set (instructions being the performable operations) which are RISC and CISC (Reduced Instruction Set Computer, Complex Instruction Set Computer). Internally even CISC is still RISC, it just allows developers to select more complex tasks which are then internally broken down to the smaller components. Your brain isn't wired to deal with gigantic arithmetic operations, which is why a calculator is a hell of a lot faster than you are at large calculations. For these same reasons, breaking down tasks that humans generally find easy such as facial recognition (barring particular brain disorders that prevent people from doing so) into simple arithmetic is incredibly hard and requires gigantic data sets and generalised patterns. This is why software that recognises say animals from images, still has a margin of error even just differentiating dogs from cats, whereas even a young child can instantly tell you whether a photo is a dog or a cat. Our brains evolved in a way that helped our survival, and for most of that million years or so, being able to quickly multiply two numbers together was a lot less useful that discerning whether that guy holding a spear is from your tribe or a different one. Computers have been designed to fill the gaps where our brains are not as capable of quickly providing information.",
"Powerful depends on the context. They are significantly more powerful at performing simple arithmetic, which all complex calculations can be broken down into. That's what processors are best at, calculations. Technically it's all they can do, we just assign extra meaning to some calculations that result in pictures, video, audio, etc. It's sometimes helpful to compare brains to computers to better understand them, but they are fundamentally different. If you try to compare them too closely, like in your question, the comparison stops working. That act as more of a metaphor for each other than an actual similar structure. You might even be able to argue that computers *are* already objectively more powerful than our brains, we just haven't written software capable of emulating sentience yet. Doing it the first time will be incredibly inefficient so it requires orders of magnitude more power to do it the first time. After that we can refine and optimize it so it takes less processing power and memory to achieve similar or even better results."
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9mdop1 | Is it real that when you left the refrigirator door open It consumes more energy? | Technology | explainlikeimfive | {
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"text": [
"It does cost more electric because your letting the cold out so it has to use more power to try and keep it cool BUT it is never going to be noticeable on the electricity bill unless you leave it fully open all day in temps with 20c and even then it's going to add maybe 25p per day, BUT here's my question who on earth goes to the fridge and leaves the door open regardless of whether it costs more electric it will make your food go off sooner and not be cold, I have never met anyone that opens the fridge and leaves it open it litterally makes no sense",
"Yes (but not very much), and the reason is pretty simple. With the fridge door closed, the thermodynamic system is mostly closed -- (almost) no energy in, (almost) no energy out -- and so the guts of the fridge don't have to do a ton of work. But every time you open the door, some of the cold air inside escapes, replaced with relatively warmer air from its surroundings. The condenser and compressor in the fridge then have to work to take the heat from that air and vent it out the back, increasing the energy consumed. The amount of air that's exchanged this way isn't very much, because the air inside the fridge isn't moving around a whole lot. You'll actually spend more energy putting a plate of hot food in the fridge than you will opening the door several extra times, because the food is directly increasing the humidity and temperature of the internals!"
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9mewkh | Why or why shouldnt we update windows? | Technology | explainlikeimfive | {
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"text": [
"This is a good question, and fits into the overall maintenance plan for your home. Windows have a lifespan of about 20 years. When they fail, they tend to let moisture in between the panes and can cause the surrounding wall structure to rot. As windows need to be replaced, it can be a good idea to update the overall scheme of the house to something more modern. However, the challenge becomes either replace them all one-by-one, which is easier on the budget but can lead to mismatched styles, or replace them all at once, which can be multiple tens of thousands of dollars of work. If, however, you mean on your computer, you generally should update Windows, though with some caveats. The updates will often be bug fixes, including, potentially, important security fixes. However, some of the updates are less about providing you with more and better behavior and more about Microsoft trying to control what you do and how you do it. Since Microsoft updates have handy numbers attached to each of them, you can pick and choose which to update. Follow along on some independent tech boards, like here on Reddit, and you'll get an idea of which updates to avoid.",
"Old windows let out cool air and head, making maintaining a comfortable temperature in your home difficult. Update to insulated windows and save on your heating and air conditioning costs. You're welcome.",
"For a standard consumer user, you should just upgrade whenever the little box pops up. For institutional IT departments, it's not so simple. You've got to make sure that every core software package you're using - many of which have far more stringent demands than conventional consumer software - is still compatible with the changes. You've also got to make sure you have training resources in place for any significant revisions to the O/S - moving from Windows 7 to Windows 10 means you need to retrain large numbers of employees on the tools necessary to do their job. For an advanced private user, you may have to sit down and evaluate your outlier programs. If you've got applications that you ported over manually from Linux, there's a good chance you'll break something with a major Windows overall. If you've got some widget you downloaded back in 2007 and hasn't been maintained since, O/S updates can cause all sorts of problems. If you've got programs that are narrow niche open source, the latest and greatest version of your O/S may break it in strange ways - graphics drivers are a classic culprit in such affairs."
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9mhsr2 | if https is a secure connection why is it recommended not to do anything data sensitive on an open WiFi network? | Technology | explainlikeimfive | {
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"These days it's not very common, but poorly-programmed websites often did the login process over https, but then all of the regular communication over http. Facebook was notorious for this a while ago. So you would log in over a secure connection, and get a session cookie, which was then transmitted over plaintext and could be copied by anyone who could see your traffic in order to hijack your session and act like you. Or, the ELI5 version: you go to a club and open a tab. At this club, to open a tab, you give an employee your credit card and they put it on file, then hand you a piece of paper saying \"I'm stringlesskite.\" Any time you want a drink, you just show them the little piece of paper. But someone looks over your shoulder and sees the paper, and makes their own copy of it. Now they can show that piece of paper saying \"I'm stringlesskite\" to the bartender and get drinks on your tab.",
"Because you don't know whose wifi network you're connected to. It could be running a so-called \"man in the middle\" or MITM attack. In which you find that you're not actually getting a secure connection all the way to the remote site you're trying to reach, but merely as far as the wifi router. & #x200B; & #x200B;",
"There's a few reasons, the biggest one is called a \"man in the middle\" attack. Let's say you want tosend a package, and you want the package to have a combination lock on it so you know noone can open it. You send a letter to the recipient, asking for a lock only they have the combination to, so you know noone but them can open it. This is how computer encryption works, you only have the lock. Only the recipient has the key. Pretty secure. But when they send out the lock, someone else (let's call them the shadow man because it sounds cool) steals it first, then sends you their own lock, which they have the code for. Now it's set up. Whenever you try to send something to your intended recipient, the shadow man can unlock your package, looking at everything inside as if you never picked it in the first place, then they can lock it with the proper lock and send it on, the recipient will just see their own lock, so nothing seems wrong. Now our analogy breaks down a little because in computer science, the \"lock\" is a number, which you can lock as many items with as you want, while in real life it's a physical lock, so lets pretend they sent you a bunch, all with codes only they know) Now, when you get a reply, the shadow man can do the same in the other direction, opening up the lock *he* sent, and relocking it with the \"proper\" lock. At both ends, everything looks fine, since it's all locked up with the locks you asked to be used. But in the middle. Someone is looking at all your stuff. Now, to wrap it up, how does this apply to open wifi networks? Well, to do this someone needs to be able to get to your package before it's sent to the recipient. So this would be like an untrustworthy post office. Someone in the post office is the one opening up your packages before sending them. Your home wifi network is different, that's the post office you know and trust not to do that"
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9mmb7n | How does Delta limit their free Wi-Fi to just messaging apps? | Technology | explainlikeimfive | {
"a_id": [
"e7fpjmb"
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"text": [
"They can block certain protocols or websites through a configured setup. This let's them block, for example, https:// but allow magnet, xmpp, or ftp. They probably also block vpn protocols but there are ways around that..."
],
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3
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9mnam0 | The latest fad is blue light blocking glasses to reduce eye strain from screens. Wouldn't it just be more effective just to change the color temperature on your monitor to reduce blue light? | Technology | explainlikeimfive | {
"a_id": [
"e7fwdsz"
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"text": [
"More effective? Maybe not. Similarly effective and has no cost? Absolutely."
],
"score": [
13
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9modll | What does it mean when you "overclock" a processor? | Technology | explainlikeimfive | {
"a_id": [
"e7g2es3",
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"text": [
"Each processor is rated with certain frequency (e.g. 3MHz). This means it can do 3 000 000 basic matematical opperations in one seccond. Doing this calculations generates heat (due to electricity flow). If processor is working with it nominal frequency it should be possible for him to work continuosly with stock cooling. You can make processor work with higher frequency (this means it is oveclocked), but this generates more heat. You must consider putting better cooling system in this case. Kind of opposite to oveclock is throtling. If processor reaches high temperature it can be set to make fewer opperations per second. This means less heat generation, some manufacturers (especcialy in mobile devices) decide to implement such feature. But it obviously means less performance.",
"Overclocking in the context of computing devices refers to making them \"run faster\" than originally intended. More specifically it is the configuration of computer hardware components to operate faster than certified by the original manufacturer, with \"faster\" specified as clock frequency in megahertz or gigahertz"
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9mspyv | What makes gain different from volume? | I know gain generally adjusts the volume. But what makes it different? Why adjust gain instead of the volume slider? I’ve never been quite sure of what exactly gain means or does. | Technology | explainlikeimfive | {
"a_id": [
"e7h19sm",
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"text": [
"Firstly gain can refer to any signal whereas volume usually refers to acoustic energy (ie sound), & #x200B; If you're talking about an audio console, then the function of the gain knob and the channel fader are slightly different. & #x200B; The gain knob is at the top of the channel and it amplifies the signal as soon as it gets into the mixer. Then it passes through the rest of the stuff in the channel which is usually a hi-pass filter, some EQ filters, auxiliary routing, a pan knob, and then down to the channel fader. & #x200B; The basic idea is to use the gain knob to adjust the incoming signal so that it's at a standard level. You do this will all the incoming signals so that they are all at the same level. & #x200B; Then you use the channel fader to adjust the relative amounts of each input in your mix. & #x200B; For example you'd use the gain knob so that all the guitars and keyboards are at the same level. Then during a song if you want the guitar to stand out during a solo, you use the fader to bring it up above the sound of the other guitars and keyboards etc.",
"Gain implies amplification. Volume is signal volume. Gain will distort signal if cranked up, as the stress is on the amplifier, as it maxes out, the SIGNAL becomes dirty (overdrive the amp means less clarity) Volume will distort speakers if too loud. The quality is clear up until the speaker reaches max and cant move properly to make the sound. Same stuff, different components. Overdrive the amp and turn it up too loud? You just get buzz or hum (instead of gain only which gets crackly/distorted as quality drops, or volume only where the speaker starts hitting flat) (Really dumbed down)"
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9mthzo | What exactly makes the indicator lights on some electronic devices stay on for a while even though you unplugged them? | Technology | explainlikeimfive | {
"a_id": [
"e7h7mqg"
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"text": [
"Capacitors. When you have a solid state device that needs DC power for its circuits and you want to power it from the AC outlet, you need a power supply. A power supply contains a transformer, to change the voltage, a rectifier to convert AC to bouncing DC, and a capacitor to smooth the DC. The capacitor works by storing electricity from the peaks to fill out the valleys. When you turn it off, the circuit stops using power, but the capacitor is still full-ish. The indicator slowly drains the capacitor, because it uses much, much less current than the whole device's circuits."
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21
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