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6yslpc | How does a computer evaluate the values of numbers, at the most basic level? | How does a digital computer know the relative values of numbers, e.g. 2 > 1? | Technology | explainlikeimfive | {
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"Yer not alone in askin' how computers represent and work with numbers, and kind strangers have explained: 1. [ELI5: How Binary Code Works ]( URL_4 ) 1. [ELI5: COMPUTER BINARY CODE- or how does a computer work? ]( URL_0 ) 1. [ELI5: How does a computer calculate 2 2 = 4? ]( URL_2 ) 1. [ELI5: How does a computer ACTUALLY work? Like, how does it transfer, read, and display data and things. ]( URL_3 ) 1. [ELI5: How does a basic four-function calculator get its answers? ]( URL_1 )"
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"https://www.reddit.com/r/explainlikeimfive/comments/4rzbze/eli5_computer_binary_code_or_how_does_a_computer/",
"https://www.reddit.com/r/explainlikeimfive/comments/60gsxx/eli5_how_does_a_basic_fourfunction_calculator_get/",
"https://www.reddit.com/r/explainlikeimfive/comments/3g4xwk/eli5_how_does_a_computer_calculate_2_2_4/",
"https://www.reddit.com/r/explainlikeimfive/comments/2ax3k3/eli5_how_does_a_computer_actually_work_like_how/",
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6yt459 | What actually happens when you turn on post-processing in the graphics settings in a 3D game? | Technology | explainlikeimfive | {
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"Post processing is usually just the 2D/screen space effects a developer applies after the image(s) has been rendered by the GPU. This can range from SSAO where the rendered image is thrown through a filter that guesses where occlusion would be to color grading to camera effects like dust particles and chromatic abberation. The commonality is that none of these effects are doing any 3D rendering but instead manipulate the resultant images from the render. The image gets rendered and then for each post effect the devs are using the image as an input to a filter which resultant image is blended onto the original render much like how you can blend between different layers in Photoshop programmatically. The reason many developers do this is because it approximates the look pretty well but applying a 2D effect after render costs much less than if you did it \"for real\" during the render...ssao/hbao is a great example for this. These determine if an object is casting a shadow on to or from itself; which happens when you have concave surfaces or inner corners. Logically, less light can reach those areas because the object itself but it would be far more expensive to do a more precise lighting"
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6yub5d | Why can't your phone use wifi and 4G/3G together? | For example when you start to move away from the wifi source, the signal and speed are getting weaker and slower. So why can't your phone gradually move to using the mobile network available instead of you have to turn off your wifi and move to using your 4G exclusively. | Technology | explainlikeimfive | {
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"[You can do it on Android]( URL_0 ) In general it's undesirable because mobile bandwidth is far more limited. Something like watching youtube in high quality could easily use up all your limit in very little time if you fail to notice. It could also result in you being charged a lot of money, and people tend to hate this kind of thing."
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6yuky9 | How are digital maps made? | Technology | explainlikeimfive | {
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"I know it sounds dumb and simplistic but they draw over top of aerial photos. It's obviously more complicated than that but that is the basics of what they do. Here's an article that digs more into it: URL_0"
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6yuudb | When streaming YouTube with poor Internet connection, why does the advertisement stream smoothly but the actual video is laggy AF? | Technology | explainlikeimfive | {
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"The way big systems like YouTube are set up is that they have a few massive warehouses stuffed with servers (primary datacenters) where it's cheap, and then lots of much smaller servers all around the world (edges). They push the most popular and frequently-used content to the edges, so that the most frequently-used stuff can come from a fast server near to you and serving only other people near to you. Less-popular stuff has to be requested from the primary datacenters, which can be thousands of miles away, serving lots of people at once. YouTube's ads are almost always coming from your local edge server because most users are watching the same small set of ads. So they're always available, always reliable, always fast. Depending on what video you're watching after, it's likely streaming from some place far away, off a more heavily-used machine that might be under unpredictable load, so they can be slower, less available, less reliable. In some cases, for the most popular services, those local/edge servers might actually be *in your ISP's headquarters*, making them really fast and bulletproof. Next time you're noticing this, try streaming the #1 current music video (it should be nearly as fast) and then something really obscure (like your grandmother's 408th video of her cat snoring) and you should notice a similar discrepancy. Of course, ads will always likely be faster even then, because serving ads is YouTube's #1 priority so they'll get prioritised over everything else."
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6yve4t | Why do MRI machines make such loud and strange noises when performing a scan? | I had an MRI scan the other day, and had to wear earmuffs in order to drown out the incredibly loud MRI scan noises. I understand that large machines can make loud noises, but these noises were not only loud, but very strange, almost laughably unnecessary. Made me wonder why the need for all these various noises, what was causing them and so many of them? | Technology | explainlikeimfive | {
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"MRI magnets work by switching powerful electromagnets magnets on and off. They also have a 2nd super powerful magnet which is always on. When the electromagnets are turned on and off, they attract or repel each other and the always-on magnet. This attraction/repulsion causes vibrations which you hear as sounds. (This is basically how a loudspeaker works - you have a magnet, and an electromagnet connected to the speaker cone - you put an electrical signal into the electromagnet and it attracts/repels the other magnet moving the cone). Most types of scan with MRI make a sort of clunking or buzzing noise, but certain types (with strange names like diffusion weighted imaging, or functional imaging) make extremely loud beeping sounds, because the electromagnets are turned on and off so quickly that they produce a high frequency sound. It is possible to have much quieter sounds, by sequencing the electromagnets to only turn on and off gradually. This way, you don't get sudden attraction/repulsion which causes the big vibrations. Most scanners have an option to run in \"silent\" mode, with certain limitations (scan takes longer, images not as sharp, diffusion weighted imaging not available, etc.) There is a 2nd source of noise on most MRI scanners, which is much quieter and always on, which sounds like a strange little birdy tweeting - a sort of rhythmic tick-whoo-tick-whoo. This is the special cooler needed for the main magnet. The main magnet needs to be cooled to a low temperature (about -271 C), and it uses a special device called a Gifford-McMahon cooler which makes this strange pulsing noise. This actually makes noise from moving parts (it's the only moving part, apart from stuff like ventilation fans and the slider on the table).",
"It's either spin the patient or the magnets. After early trials of spinning patients ... they quickly learned spinning the magnets was better.",
"The magnetic forces generated inside an MRI machine are very difficult to appreciate, they are ginormous. The machine itself is flexed by the forces. It can't be made of thicker steel, because steel has magnetic properties. Any conductive metal can cause problems with the image, and so the machine has a lot of plastic structures that resonate with wonderful thumping sounds when the machine innards press on them.",
"Finally one of these I have 1st hand experience with! There's a giant magnet inside an MRI machine that's cooled by liquid hydrogen. When a current is run through this magnet, the magnetic force generated is so strong that the coil of the magnet expands slightly. This expansion happens suddenly and is quite loud. Source: writes code for MRI image reconstruction"
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6ywiz5 | Why does reloading a page sometimes takes ages, but when you close the tab and enter the same adress it loads in a matter of seconds? | Technology | explainlikeimfive | {
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"Web developer here. It can actually be caused by a number of things, depending on the browser you are using as well. Often though it goes something along the lines of this: When you go to a website, your browser will often save the files for the page, so if you do something like close and reopen the tab it can just use the files it saved, instead of having to get the files over the internet all over again. When you just refresh a page though, you're manually saying you want the browser to get the files again, usually cause they may have updated (like if you want to see if new YouTube videos were posted)",
"The modern HTTP spec reuses the same network connection for all requests to the same server endpoint. If you close your tab/browser you make a new connection to the remote server endpoint which is pretty much always load balanced across many individual servers and so you get another roll of the dice to hit a functioning one."
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6yx3q7 | What is the "Wide Color Gamut" RGB space and how is it different from the "Millions of colors" we hear about? | Monitor and TV companies always talk about the millions of colors. But now there's "Wide Color Gamut," which means what, exactly? Why is there so much green in the chat on Wiki? Why is the white point not centered? | Technology | explainlikeimfive | {
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"Any set of primary colors creates what is called a color gamut. It's the range of colors you can make by mixing the primary ones. For just about every electronic display, there are colors in the visible spectrum that just can't be accurately reproduced due to this. This is particularly problematic when you are working across color spaces. For example, you might used digital editing software on a photo, but the ink used to print the photo may use a different color space. So the photo may not come out as expected or you may simply not be able to utilize the full capabilities of printing if you restrict yourself to where the two overlap. The Wide Color Gamut is a color space that allows a wider variety of displayable colors than is used for most electronics currently. This is particularly useful for photographers and graphic artists who could use the expanded color space. However, there is a trade off in that the density of colors is thinned out, meaning the difference between colors that are 1-off for their RGB values are more different than in color spaces with a smaller gamut."
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6yz53i | how does a capacitor work? | What does it do exactly and how? | Technology | explainlikeimfive | {
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"It stores up energy and gives it back, but it reacts differently to different frequencies of the circuit it's attached to. Because it reacts to frequency, designers can create math functions with the capacitor and two other components, the resistor and the inductor. These other two each act differently in the presence of changes in voltage and current in a circuit, and those reactions are predictable with math. So they can make a circuit that blocks high frequencies and permits low, or vice-versa, or more complicated reactions. How a capacitor works is, when you apply a voltage across its two terminals, current (electrons in motion) fills up the capacitor with a charge that's based on the amount of the voltage and the value of the capacitor. It takes current to fill or drain a capacitor, and that current is limited by the circuitry. So there's a non-zero amount of time required to change the voltage and charge on a capacitor. That change in voltage, times the capacitance, tells you the current flowing. Double the voltage, double the current. Halve the capacitance, halve the current. This ability to hang on to a voltage until the appropriate current flows makes capacitors useful in another way. They can reduce power spikes that would otherwise appear at the power and ground terminals of a chip, so if you look at the chips on a circuit board you'll see capacitors, right next to them, protecting those chips from noisy power. A side note, I have a friend who is fond of asking the same question. He answers it himself, \"It works by FM.\" ??? \"F#€ & ing Magic.\" Edit: probably the longest comment I've ever written and it's on f#€ & ing capacitors."
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6z0xxh | How do holo-sights on weapons work? | Technology | explainlikeimfive | {
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"One of the problem with a regular cross-hair sight is that your eye has to be in exactly the right spot for it to be accurate. If your eye is slightly off to the side, then you will be looking 'across' the sight, and will be inaccurate. A holographic sight removes, or at least reduces this problem. A hologram is a 3-D image - it has depth. The things in the holographic image appear to be behind the plane of the image. With a holographic sight, the image is of a targeting cross, dot or circle, and it is made to appear to be a long way in front of the weapon. How this happens is because of what a hologram is. Instead of recording just the amount of light hitting a surface, it makes a record of all the different light rays and their direction. Then, by shining a laser light on the hologram, it can recreate all those light rays, creating the appearance of a distant crosshair."
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6z1etn | Why hasn't battery technology improved as fast as other components? | Technology | explainlikeimfive | {
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"Battery technology has advanced by leaps and bounds in the last 20 years. You just think it hasn't encase the physical size is still same in cell phones. That's due to increased demand by the electrical components. The capacity of those same size batteries are worlds appart. Every year the same size battery gains the capacity to store more and more electricity. Cell phone manufacturers don't shrink the size of their batteries because the CPUs are demanding more and more electricity and battery life of a device is one of consumers primary concerns.",
"Batteries are fundamentally limited by their chemical reactions/functions. A lithium ion physically exists and interacts with other molecules to provide or absorb electrons. It takes up space and weighs some amount. We can improve the tech of the battery to allow more of the useful chemical and fewer metal walls for example, but revolutionizing the battery requires a new chemistry entirely. With computer chips, we make functional pieces smaller so the same chunk of silicon can hold more of them. But we haven't necessarily made the chunk of silicon cheaper or more power-efficient, we can just use a smaller one. There is no similar analogy for batteries, what we want to do *is* to make it cheaper or more efficient for the same size. Something we've never been great at with other pieces of electronics either.",
"We know how to make electronic integrated circuits smaller and thus faster and better. It's a series of improvements of various kinds in terms of optics, process, etc., but it's a continuum over decades. Whereas, if we make batteries smaller, they are just smaller, and hold less energy. We have to change the fundamental chemistry of batteries to make them hold more energy, and that process doesn't advance nearly as quickly. URL_0",
"Ancient? I see you never owned nickel-cadmium rechargeables. Li-ion is like Star Trek compared to that shit.",
"It has improved a lot faster than many people realize. The problem is modern devices like smart phones are designed to last about 18 hours on a charge. You plug them in overnight, use them during the day, then plug them in again at bedtime. As battery life improves, new features, like bright screens, GPS, wireless, 4G, and GPS are squeezed into phone, bringing the life back down to 18 hours or so. Old Nokia 3000 series phones got about 100 hours standby on a 500 maH battery, and that was with the old, power hungry AMPS anology signals. You put a modern 3000+ maH battery in one of those, and you would be charging it once a month.",
"Others are addressing this from a technological perspective so I will approach the economic angle. The mainstream demand for improved battery technology really did not exist to the same extent as it does today. Before miniaturisation and widespread adoption of pocket computers (mobile phones etc) batteries were simply good enough for most consumers. The idea of a pocket pc was still in the realm of scifi for many. Batteries were for things like torches, cars, radios, toys etc and a few extra grams and a slightly bulkier form factor really wasn't a problem for these items. Once consumers saw value in newer technologies and began to demand smaller, faster, longer lasting and more powerful mobile computing devices, battery technology quickly became a limitation and thus more heavily researched as having better battery tech would give a competitive edge to hi tech manufacturers. Now that we have mainstream mass produced high density batteries, we are starting to find applications in a wide range of industries, for example electric vehicles which have become more viable as a result. There was nothing stopping the research and advancement of battery technology sooner, it just wasn't a priority compared to other major research. Parallel streams of technology often behave in this way, feeding into each other and moving in fits and bursts based on new discoveries and market forces.",
"It has. We have simply increase the power consumption rates of our devices at near equal step. If battery tech had not been advancing phone batteries would last about an hour.",
"URL_0 This guy invented lithium ion and contributed to the development of a solid state sodium based battery with 3x the energy density. 10-15 years these new batteries will replace lithium ion."
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6z2a1p | How does the Snapchat map know what people are doing? | Technology | explainlikeimfive | {
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"Not an expert but the most obvious way for it to display these are just information it gets from background applications and or location. Say you're somewhere called 'university' or 'library', if you're within a radius of those buildings your avatar will say studying. As for the listening to music part: it's very easy for Snapchat to tell if you're running a music-streaming app. If you start the app *or* play music, Snapchat can change your avatar in the background simultaniously. Travel with a speed higher than 10-15km/h and it can assume you're driving a car or using public transportation etc. etc.",
"Got a music app open/headphones plugged in? Then you're probably listening to music. Moving on a road in car speed? Then you're probably in a car and so on",
"The app can tell how fast you're moving, what apps are running, and if you have headphones in."
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6z33kj | how come my rack light on my ship (Navy) takes forever to turn on when it's dark, but if I flash my phone screen light at it it turns on immediately? | Technology | explainlikeimfive | {
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"Probably has a photo sensors to slowly come on when dark to allow yourself to adjust. (In emergency wouldn't want to be temporary disoriented by bright light) vs when you shine your flashlight at it you're tricking it into thinking room is already bright.",
"Probably because it is a shit level fluorescent fixture with a shit bulb and over hour ballast. URL_0 When fluorescent fixtures are old they take a long time to activate the phosphors. Sometimes the bulb is has just leaked a lot of its internal gas so it does not work worth a shit. Replace the bulb, if that does not fix it replace the unit. They lose 60% of their brightness in the first few thousand hours so a new one shoud be crazy brighter. I always used civilian warm bulbs so I could read. (the navy ones were fucking blue/white horror generators) In the old days there was a separate igniter unit you just replaced now they are so cheap you replace the unit. I really doubt you have one that old. If it's new and LED ignore me i'm old and haven't a clue. Was in the Nav.",
"Could be photovoltaic cells that can grab some of the light from your phone to turn on quickly, but otherwise, need the ship's power to function. Find some ET3 to explain it to you if you need accurate information about her systems."
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6z39ox | What was grocery shopping like before scanning? | was it really slow for people buying stuff in bulk? how did they handle it back then? | Technology | explainlikeimfive | {
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"I remember this from when I was a kid. Each item was tagged with the price of that item. So when people were adding things to the shelves they would also use the label maker to add the price tags. For bulk items like fruit and similar things you would not tag each item but the cashers would have a price list for the item. A good casher would be able to type the prices into the register at the same speed as average modern cashers who use the scanner. The main disadvantage of this was that it was harder to get a receipt as it was easier to just type the price and not the product name. So most people did not bother with a receipt or just got receipt for \"misc groceries\". It was not that bad for the customers but the problem was that the shop did not know how much they were selling of different items and therefore not how much they had left and how much they had to order. A shop owner would spend a lot of time counting stock and judging how popular different items were so that he could plan for how much he had to order. This is the main reason why they changed to using barcodes. Now they know exactly what products are being sold at what shop and at what time. A lot of times they even know who bought the product. So they have a lot more control and can do more informed decisions when ordering products and for marketing.",
"Items had price stickers on them (placed by employees). The cashier would type the price into the register. It was slower, but only slightly.",
"It depends on how far you go back, but just prior to scanning, it was a combination of things. In smaller stores, clerks were expected to just know the price of everything and might have a book where they could look up prices they hadn't yet memorized. We can still often see this today with produce, although now it is usually memorizing the code representing the item and the computer looks up the price. In larger stores, items would have price tags and these would be manually typed into the adding machine (of whatever sort). Buying in bulk isn't really a problem for this system. You just need to know the unit price and number of units purchased then multiply. Even today, if a customer buys a large number of the same item, it will usually be scanned once and the number of items is manually input. Receipts were often less descriptive and/or were written up by hand. In many places you had to request a receipt because the labor that went into producing one was rather high. Sometimes stores or restaurants with particularly limited supplies would have some manual code-input device which would allow for faster input and more detailed receipts.",
"I asked my grandpa real quick and he said people didn't buy in bulk as much. You'd go to the store and get a loaf of bread, some milk, eggs, and a few other things. People weren't getting heaping grocery carts full of frozen meals and stuff. That being said, yes it was still slower. And the cashiers had to be really good with thier basic maths skills.",
"I am feeling old. When I was little my dad owned a store and the cash register was an old push button one (think old typewriter keys) and made a huge ding and the drawer slammed out of it so step back. We were pretty excited to get an electric cash register. We had every price in the whole store memorized and had to price everything with a price gun. It really isn't any faster now vs back then because you got so accustomed to the machine that you could type one handed without even looking at the key pad while ringing people through the check out."
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6z3chy | What is OpenStack? | Hello friends I have an idea its related to cloud technology,but where does it fit in like Is it a Hyper-visor on which several OS exists? | Technology | explainlikeimfive | {
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"OpenStack is not in itself a hypervisor but is a system for managing and providing services that makes your hardware with hypervisor into a cloud. It is very modular and you can therefore make it work with different technologies and use different aspects of it. To make a cloud you need hardware to run hypervisors, storage, network, etc. and on top of this you need management, authentification, payment, metering, monitoring, logging, etc. and in addition to VMs you might want to provide databases, web services, load balancing, VPN, etc. So OpenStack is a platform to implement the rest of the cloud when you have the basic hardware in place. If you can manually set up a VM then you can get OpenStack to do the rest."
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6z3osc | How do companies know your credit card is valid without charging them? (For free-trials and what-not) | Technology | explainlikeimfive | {
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"It's possible to \"pre-authorize\" a charge, which is done when you place an order that won't be shipped immediately. So they can effectively ask the card issuer \"if I were to ask for $1 from this card, would you say yes?\" without then charging the card."
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6z48d2 | How does the Wacom Intuos's pen's side button work without batteries? | Technology | explainlikeimfive | {
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"It gets power from the tablet, a bit like an RFID chip gets power from the reader. The tablet transmits a radio signal which generates a small current in the receiver in the pen. That's enough power for the pen to transmit a signal back, and the signal includes the state of the button and pressure sensor."
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6z48tv | How did the first computer programmes know what one second is, or any unit of time for that matter when mankind invented the units of time? | Technology | explainlikeimfive | {
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"Well mankind invented computers too, so of course we built them to use the units of time we invented. Computers generally keep time with a quartz crystal. When current is applied to them they oscillate at a predicable frequency. By counting the oscillations the computer can work out if a second has passed.",
"In the *very* earliest computers, time was ignored entirely - they had no clocks and they processed data in batch jobs i.e. there was no attempt to do any \"real-time\" operations. I remember reading about some of the problems faced in early attempts to do computer music - since music is time-based."
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6z5yaj | How does a Bluetooth know what device to send data to. | For example: how does my portable Bluetooth speaker know to send and receive the music data from my phone? | Technology | explainlikeimfive | {
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"Each device has a unique serial number. When you pair your Bluetooth device with your computer, it records that serial number so when it sends out data packets to your headphones, it sends it with a tag that includes that serial number. Then your headphones say \"ah, this packet is mine\" or if it sees someone else's computer sending to another set of headphones, it ignores those packets.",
"All Bluetooth devices come with a passcode that you have to enter to connect it with another device. Although most updated devices do it automatically with the \"pairing\" feature.That passcode is the \"glue\" to making the Bluetooth device connect only with your phone. Once it's connected it flows through radio waves to play whatever information is being sent"
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6z7bw6 | How is it that '.exe' files can have such a small file size, (MB/KB) and be used to install many gigabytes of data? | Technology | explainlikeimfive | {
"a_id": [
"dmt2l3x",
"dmt2hkp"
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"text": [
"If it's a small file that installs lots and lots of data, then in all likelihood it's a downloader which downloads all this data from the internet and then installs it.",
"A file with the `.exe` extension normally contains binary code which can perform arbitrary operations. For example, it could download data from the Internet, or even create an unlimited amount of random data. Do you have a specific example in mind? Some executables contain compressed data that the executable will decompress. Some data is highly compressible, like text, while other data (like video, images or music) is generally not as easily compressed."
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6z88km | I never understood how megapixels work and why the more you have the better the image | Technology | explainlikeimfive | {
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"dmt8cgn"
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"text": [
"A megapixel is a million pixels. An image consists of a big grid of pixels. The more pixels you have the more details you are able to include in the picture. There is also a lot of other factors to determine the quality of an image and it is quite possible to have more pixels then you need. But if you have too few pixels the image gets fuzzy."
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6z8k0o | Why battery level of mobile or laptop increases after restarting the device? | Technology | explainlikeimfive | {
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"text": [
"The computer reports the battery left based on what it is doing at the moment you check. If a device has been on for a while, its been doing more things and has more processes running. After restarting it much fewer processes and resources are being used, so it reports back that there's more battery. Think of the battery level not as a set, specific level, but as \"This is how much of the battery you have left, if you continue doing exactly what you're doing right now.\""
],
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6z8zqw | How does an internet connection become slow? | Technology | explainlikeimfive | {
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"text": [
"Lots of things can have an effect. If many people in your home are using the same WiFi network, the network may become bogged down. Interference can seriously degrade your signal, if there are any big sources of interference between you and the router. Walls, floors, etc can have an effect on wireless signal too. A wired OR wireless connection may be throttled by your provider or slowed down if there is a lot of internet traffic in your area. Outdated modems/routers or damaged equipment (modem, router, Ethernet cables, antennae, cable in the ground) will certainly not help.",
"I have found that in many cases the answer isn't really the answer to this question but rather the answer to completely different question that people don't realize is a separate issue. That question is \"why does a WiFi connection become slow?\" WiFi is so ubiquitous that people think of it synonymously with \"the internet\" but the issues and fixes, while peripherally related, are not the same. There are many answers on the network side that apply to both wired and wireless networks, but a few key answers you will find on the wireless side only because they deal with radio frequency communications. Some of the [predominant reasons]( URL_2 ) have [multiple possible fixes]( URL_1 ), and the reasons can be [fairly dry and technical]( URL_3 ). Key is that a lot of people who should know better (and a lot of devices, too) have it in their head that they need to boost signal to hear above the noise, when in fact they're only boosting the noise. Some of the [most effective devices]( URL_0 ) use the lowest effective power settings to communicate over multiple selective channels, helping alleviate the ridiculous amount of RF noise in crowded places with multiple competing wireless networks like apartment complexes and office buildings. Basically, the answer may actually lie in the question you're not asking--about wireless--and not so much in the answer to the question you asked. If you're not, in fact, conflating internet and WiFi like most people do, then there may be completely separate issues at play. Now to answer the question you actually asked more directly, one way an internet connection becomes slow is when the FCC abandons Net Neutrality and allows ISPs like Spectrum, AT & T and Verizon to throttle your traffic according to their whim and then charge you out the nose to stop doing what they weren't allowed to before.",
"If your Internet provider is a cable company, you share the bandwidth of your segment of the cable with all the other households on that segment. So if everybody else happens to be streaming or downloading, the total demand may exceed the bandwidth capability of the cable, and you will experience a slow down."
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"https://www.geekzone.co.nz/sbiddle/8728"
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6z9191 | How did rulers lead millions of people before there were any fast methods for communication? | Ex. Genghis Khan growing the Mongol empire, or Julius Caesar leading the Roman Empire. | Technology | explainlikeimfive | {
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"text": [
"\"Ruled\" is overstating it, as other posters have noted. If you watch *Game Of Thrones*, you can get some idea of how it worked in medieval times. The exact nature of the rulers made little difference to the average person, and the provinces were self-sufficient and didn't need \"ruling\" on a day-to-day basis. Providing soldiers for armies was one form of \"tax\" imposed by the central government, in return for defence against foreign invaders. In the case of ancient Rome, a Roman citizen could (it was said) go anywhere in the Roman Empire in safety. armed only with the words [Civis Romanus Sum] ( URL_0 ): I am a Roman Citizen.",
"Their method of \"rule\" was different than the way we're \"ruled\" by our federal government. Being just some conquered part of the Roman Empire, for example, was often as simple as \"pay your taxes when we come around asking for it\". Of course it couldn't react very quickly to problems in far off fringes of the empire... but problems wouldn't usually spread that quickly from the far off fringes of the empire, either. There was almost always frontiers that were nominally and militarily part of the empire, but locally under unstable control."
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6z9k4o | How are companies allowed to track personal info of people who haven't signed up for their website when the people they're tracking might be under 13? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"COPPA states that companies aren't allowed to track the *personal information* of people under 13 without their parent's consent. Here's the definition of personal information [from that law]( URL_0 ) (8) Personal information. The term “personal information” means individually identifiable information about an individual collected online, including— (A) a first and last name; (B) a home or other physical address including street name and name of a city or town; (C) an e-mail address; (D) a telephone number; (E) a Social Security number; (F) any other identifier that the Commission determines permits the physical or online contacting of a specific individual; or (G) information concerning the child or the parents of that child that the website collects online from the child and combines with an identifier described in this paragraph. Opening an account on a website generally requires collecting at least one of those pieces of information (usually an email address). Facebook's ad tracking for users without an account doesn't collect any of that information, and they have no way of tying the information they do collect back to an individual's real life identity.",
"Doesn't Facebook have in its terms of use that you must be 13 or older? I imagine it's for this very reason. Plus when you sign up for apps or websites, you generally agree to the use of cookies and all kinds of other data tracking. All kinds of good stuff in the fine print.",
"Lets say Timmy is wandering around the mall. Timmy visits the google store. The google store has a shower at the exit that paints everyone's arm a different color based on what they do in the store and what the google store knows about them. The google store can't paint Timmy's name on his arm, but they are allowed to color men differently then women. There's actually 1000 different colors based on how old you are, gender, and interests. Timmy is welcome to clean his arm, but most people don't because the coloring is not very noticeable. Now Timmy walks into the amazon store. Because Timmy went first to the google store, amazon knows Timmy's age, gender, and interests simply by seeing the color of his arm. Amazon knows Timmy is between 12 and male and lives in a Chicago suburb based solely on the color of his arm! Timmy browses in the amazon store for a shaving kit and some football jerseys for his local football team. The amazon store also paints peoples feet when they leave the store. Amazon has 1,000,000 different colors depending on what a person's interests are or what their actions are. Just like google, amazon can't paint the person's name (even though they know the name) but can paint enough information that is even more useful. Amazon can even claim that they don't know that Timmy was 12 when asked, because no one knows for sure how much they know about google's coloring scheme. Now Timmy walks around the mall for a while, and gets a different body part painted after exiting each store. Each store isn't allowed to paint Timmy's name or super specific information, but each store probably knows Timmy's name and can definitely paint a pretty good picture of Timmy based on his activity in the amazon store or the google store or any other store like the yahoo store or the credit card store or the facebook score. Each store can plausibly claim that they didn't know Timmy's age or name when he walked in or when they painted him (even though they do). In real life, there's paint stores too who help all the stores in the mall paint colors that help them and make sure that each company that uses the whole painting thing benefits by working together. And help provide all the stores in the mall with scanners that help identify all the members who walk into the store and information about them so they can serve Timmy better. There's also a way for Timmy to clean himself before he enters into each store, so that no one really knows what he has been up to. However, because the paint doesn't really tell anyone anything that compromises Timmy's identity, its probably in Timmy's best interest to not stay clean so that all the stores in the mall can serve Timmy better."
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6zai3t | Why does this jpg image move like a gif? | URL_0 | Technology | explainlikeimfive | {
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"text": [
"Turns out that if you take a .gif with animation and rename the file type as .jpg, the code that displays the image still figures out that it's a .gif. all of the animation will still play. If you download the one you gave for an example and check the properties, they show that it really is a .gif."
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6zakar | Why are all car/truck tires black? Can't we get white, red, blue, or other colors? | These would sell like crazy. Most people only ever buy tires when they're worn out. If I could get tires that wear out faster but I could swap colors when I wanted, I'd be all over that. Is there some technical reason why tires are always black? | Technology | explainlikeimfive | {
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"text": [
"We absolutely could get those colors, but the tires would look incredibly dirty after a couple minutes on the road. Darker tires = appearance of being less dirty",
"[They do for bike tires]( URL_0 ), and [they have slow-speed coloured tires available from China]( URL_1 ). Today's tires are largely formed from synthetic rubber plus various reinforcements like wiring. It's black because a toughening addition is carbon black, which is pretty much charcoal and is black as you can get. The result is an excellent mix of flexibility, strength and wear resistance. There's a few ways to make it a different colour: put a layer of something else on top of the black rubber like a coating, put some sort of colour into and through the rubber itself to overwhelm the carbon-black, don't put in carbon-black, or use a non-rubber chemical. We've done the first and you can buy such tires today. \"Whitewall tires\" which have a band of white on the outer facing of the tire, is a classy element of a lot of antique cars. But you can only really put that coating on the parts of the tire that don't touch anything, otherwise it'll just abrade off quickly and look nasty. The second option doesn't work very well because, as you stated, they wear out so much faster. The problem with changing the colour of the synthetic rubber that they use for car tires is it would require a LOT of dye or other colouring to overcome its pitch-black colour from the included carbon-black, resulting in a much weaker tire. Or you could leave out the carbon-black to make it easier to colour something else... and again, much weaker tire. And the final option, a different chemical formulation, would also be weaker and less long-lasting, absolutely killing the tire's life at normal driving speeds. [edited to correct an inaccuracy]",
"Transparent tires were invented, but were too impractical for use (they only looked good it you didn't use them). URL_0",
"The color is because that carbon is added to the rubber. Rubber is white and the first tires was also white since rubber has a off-white color. Early tires was pure white zinc oxide was used as a addetive. That is the reason the the Michelin Man is white, adding carbon to tires stated 14 years after he vas created in 1898 Carbon is today added because it improve strengthen, heat transfer, durability and make it in all way a better tire. So a tire of another color would be worse. There exist tires of different colors but the usage is for exhibition not for road usage since the will wear out faster and be less safe"
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6zcakz | How can Apple deploy the new iOS11 on Millions of new built iPhones in just 1 Week? | Technology | explainlikeimfive | {
"a_id": [
"dmu6knt",
"dmu8alr"
],
"text": [
"Well-designed manufacturing processes is the how. Most of the devices have already been built and loaded with the firmware. With regards to last minute bugs - that's what MR1 is for.",
"Couple of points: 1) The GM has likely been done for a few days by now. 2) We don't know how long they new phones will be released. It could be a couple of weeks or even longer. 3) The GM software as it is has been made available to the manufacturer by now. All they have to do is flash the device before packaging it. That can take a matter of minutes per device and they can do this with multiple phones at once. This is why there is a delay before announcement and release. If they have a critical bug, they release a day one patch to fix it unless they catch it in enough time."
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6zdi02 | How is my dslr able to tell how a picture should be taken when set to auto? | Technology | explainlikeimfive | {
"a_id": [
"dmuh5ji",
"dmuj7di",
"dmuo0sf"
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"text": [
"In short, the camera has a bunch of sensors that measures light levels, colors, focus and etc. The company has programmed the camera to set the settings a specific way for different situations (different inputs from the sensors). The most important settings, imo, are focus, shutter speed, contrast/lighting/flash, aperture (how much light is left through).",
"The real answer is that it often isn't, especially when you're using wide auto focus. The camera makes an \"educated\" guess, but it's just guessing.",
"Recent cameras are pretty smart nowadays. Previously were best guesses via input parameters. But now with a combination of facial recognitions, motion sensors, light and contrast, the camera is pretty good at working out whether you are taking portrait, sport, landscape, macro or night shots. Then it's a matter of applying predefined template for the type of shot. Camera don't get it right all the time, but is getting pretty good. I remember a recent review complained that a M34 system are too sensitive to motion and switch to \"sport\" mode (lower apertures, higher shutter speed, etc) if something moves across the shot whilst aiming at a landscape."
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6zdsn4 | Why are we not yet using fingerprints instead of signatures for contracts? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Fingerprints aren't exactly as unique as claimed, and they're often compared by a guy with a magnifying glass. Print scanners that use a glass plate like the door security type you see in movies can also be fooled by using a piece of raw meat and some cling film, making it register the last print used. It would require a massive fingerprint database that would have to be maintained by someone for everyone else, and registering prints for everyone at incredible costs.",
"First, most contracts are notarized and associated with an open negotiation. So, forgery of a signature on a contract isn't very likely in those circumstances. Secondly, a signature is more quickly matched to a person. This is more of an issue than you think in organizations where you have several people with overlapping responsibilities, such as in a startup. You can know who to ask about the deal by looking at the signature. Can't as easily do that with a fingerprint. Third, since you're worried about forgery, is important to note that signatures signal intent. If a signature is legitimate, it's very difficult to get it on an unintended document. The same isn't actually true of a fingerprint. You leave them everywhere. They can be directly and exactly transferred or copied. The actually oils that make the mark can be picked up and moved with no more distortion than occurred due to the normal stretching and warping of your own skin. Stains and dyes can be adhered or infused into them, making an identical mark to an intentionally made print. Fingerprints are an inferior method for signing a document. That said, they'd be fine for use in addition to a penned signature. Also, fingerprints are messy.",
"Forgery of signatures isn't generally an issue. Unlike the movies, having a \"signed contract\" isn't some magical artifact that makes everything happen. Contract disputes are almost always about whether the involved parties properly followed through with the terms of the contract or whether those terms are legally valid.",
"> Finger prints cannot be forged anywhere near as easily as a signature. People don't really want to dirty their fingers every time they would sign for something, and forgery of any mark is easy enough considering current technology (photography, scanning/printing, etc). Instead the standard for making sure someone is who they say they are is photographic identification via a government issued ID such as a driver's license or passport. If I stick my fingerprint on a lease at the apartment complex office what are they going to compare it against, and how would they even tell the difference? Most people can at least compare a photo with a person."
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6zevh3 | How does the Mars Curiosity rover receive radio commands from NASA if Mars rotates enough to be in-between Earth and Curiosity, thus blocking the line of sight? | Technology | explainlikeimfive | {
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"dmuolzv"
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"text": [
"There are orbiter probes that serve as relays. Currently, the Mars Reconnaissance Orbiter and the Mars Express missions are the primary means of communications relay with the surface."
],
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6zew0l | How could NASA command the Voyager 1 from 6 billion kilometers away? | To quote Wikipedia: > Voyager 1, which had completed its primary mission and was leaving the Solar System, was commanded by NASA to turn its camera around and take one last photograph of Earth across a great expanse of space, at the request of astronomer and author Carl Sagan. My wifi-signal barely reaches my kitchen, and while I understand they can build stronger equipment, how --on earth-- in space can a command be issued from over 6,000,000,000 km away, more than 27 years ago? | Technology | explainlikeimfive | {
"a_id": [
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],
"text": [
"Your wifi signal is generated by cheap consumer electronics, which are specifically limited in power by FCC regulations. Germany's broadcast of the 1936 Olympics was the first radio signal with enough power to escape our planet, and is currently acting as humanities first interstellar announcement at a distance of 81 light years. That was a good 40+ years before Voyager. With 40 years of additional advancements we were able to fine tune the beam so as to point it at a spacecraft, and relay commands to it. Also worth reminding again, the first human any alien species is likely to see, is Hitler."
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6zftwp | When a car's battery runs out, I need to reset the clock and the radio station presets. Every time. But the (equally digital) odometer display remembers EXACTLY where it was. What's up with that? | Technology | explainlikeimfive | {
"a_id": [
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"dmuwiq2",
"dmuxbbn"
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"text": [
"There are legal requirements that prohibit odometer resets during normal operation and service. The odometer data is stored in eeprom memory every mile that doesn't get reset.",
"TL;DR: your clock and radio station settings are stored in a different kind of memory component than your odometer information. The former are kept in a species of \"volatile memory,\" i.e., a memory component that requires constant power to maintain its data. The latter are stored in \"non-volatile memory,\" i.e., a memory component that will maintain its present state, even through power cycling, unless it is deliberately wiped or otherwise changed.",
"I don't understand why they don't save radio station presets in non-volatile memory. It's not like the technology is hard. My laptop keeps perfect time even when the battery is out because of a battery backup that almost never has to be replaced. Things like this really bug me."
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6zgub4 | how do autodimming mirrors work? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"This is how it works in my vehicle (1997 Jeep Grand Cherokee) with an auto-dimming rear view mirror, I'm assuming they're all similar. There's a light sensor on the front (facing the windshield) of the mirror and another on the back (facing you). When the amount of light detected by the rear sensor is X times higher than the amount of light detected by the front sensor, (i.e. it's dark out and someone is tailgating you with their high beams on) the vehicle's computer sends a signal to apply a voltage across a fluid built into the mirror. When the voltage is applied, the fluid goes from clear to a darkish-clear color, which blocks some of the light, so the mirror dims."
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6zhgth | If an alien probe with similar dimensions and operational capability of the Pioneer or Voyager spacecraft passed through our solar system, would we detect it? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"Not a chance, it could pass between Earth and the moon and we'd probably miss it In 2013 a 20 meter Near Earth Asteroid entered the atmosphere and exploded over Chelyabinsk Russia. It was undetected until it entered the atmosphere. Voyager is much smaller, it's main dish is just 3.7 meters Most Near Earth Objects under 100 meters are not yet detected and tracked, we'd never see something the size of Voyager",
"Visually, almost certainly not. If it were built to blast out omnidirectional radio signals (I don't think ours were), it still had power after millions of years, and it used frequencies that we recieve, but don't transmit on too much, we might pick it up. My guess is that it would have to come inside the moon's orbit for us to stand a chance of hearing it, though.",
"It's possible but there are some caveats. The farther away you are from a source of light or radio waves, the lower their intensity will be. So something twice as far away from you, will only be 1/4 as intense (falls by the square of distance). In order for us to talk to our own probes we have to combat this loss of signal over long distances by using a very directional antenna and pointing it in the Earths direction. Kind of like cupping your hands around your mouth to shout in one direction which amplifies your voice. In order for us to detect an alien probe it would need to be very bright, very loud, or very close to us. If it used a directional antenna to broadcast in a narrow beam back to it's origin, if it wasn't pointed right as us we might not hear it. If it had a low albedo (was dark) we might not see it unless it were very close to us. Even finding satellites orbiting the Earth can be difficult without knowing their orbits. It's how spy satellites work. They go in eccentric orbits, are painted very dark so they don't reflect much light, they broadcast seldom to prevent eavesdropping, and they may even have radar absorbing paint on them. Radar however would likely locate a probe if it were large enough, and we happened to be pointing radar at it and listening. Earth based radar installations can project pretty far out there, but we usually aim them at very large objects that we already know are there. To catch a smaller object we would need more listening stations, and more powerful radar scanning the space around the solar system."
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6zjndo | What exactly happens in a hard disk when you defragment it? | Technology | explainlikeimfive | {
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"(no one cares anymore because sdds are cheap now) I MEAN, WHO SAID THAT!?!? So you have a bunch of files and an index file of where your files are physically on the disk. Basically, you reorganize those files so the files are sorta in the same place instead of...well some over here and some over here and so on. this reduces latency and speeds up read speed. If that didn't make any sense (sorry, three beers in) think about it like this...you're packing for a two week trip. You have stuff all over your living place. [Living space = hard drive] Do you want to go to one place for your toothbrush, another place for toothpaste, and a third place for mouthwash? Psh no. That's stupid. Put them all in the bathroom cabinet or shelf. You \"defragmented\" your \"teeth cleaning files\". Or like, you have clothes in your closet, in a couple drawers, in the laundry, in the car, in your friends car, blahblahblah. Put them all in the same room so you can get to them quicker. #DefragYoLife DrunkNijaEdit: In a SSD (Solid State Drive) it doesnt make a difference to defragment the drive because there basically is no latency. In a Hard Drive (spinning disk), you read one file and then have to wait for the disk to spin alll the way around to read the next sector. In a SSD, its like you're on a jet powered library ladder thingy on wheels. You want these five books? Well BAM WOOSH GRAB WOOSH GRAB BAM WOOSH GRAB YAY! Done.",
"Lets say I have a bookshelf in alphabetical order. 1984 Adventures of Huck Finn Crime and Punishment Moby Dick War and Peace I buy the book Great Gabsy, but I'm kind of in a hurry, so I put it at the end. Then I buy Brothers Karamazov, and also put it at the end. Eventually, I'm going to take the time and reorganize my bookshelf and put everything back in order. Your hard drive does the same thing. If I have a file, it might be stored in this sector. If it doubles in size, you would like to put the second half right next to the first half. Its in the most logical spot, and its best location for a mechanical hard drive to access it quickly. But if something else is already there, it can not store the two files together. For time reasons it puts it somewhere else, until you defrag, and give your hard drive the time to move everything around.",
"You can think of a file as a big, blank book. You can write a story in the book, then read it later. You can also erase a story to re-use that page. When you write a long story--save a big file--you pick somewhere to start writing, but you may run into another story's space before you're done. To handle this you just write \"continued on page ###\" and keep going on that page. If that only happens occasionally then all is well. As you use your hard drive more and more you wind up with this happening more. It's especially bad because hard drives are pretty fast at reading or writing in a continuous block, but jumping to a new point takes a relatively large amount of time. I've seen files with well over 1000 of these jumps, and that's a fairly common level of fragmentation. Defragmenting is just going through and copying your stories (files) into sections that are all continuous so that you don't have to make those jumps. It makes reading your files faster, although it's slow since you have to potentially read and write the whole disk. It's worth noting that solid state drives don't need to be defragmented. The whole reason hard drives need it is that they're slow at handling the jump (they have to mechanically move a read/write head, then wait for the platter to spin to the right point so that the data passes underneath the head). Solid state drives are many orders of magnitude faster at this since they're all just circuitry. A defragmentation also does a lot of reading and writing which can lead to extra wear on the drive, but that's seldom an issue these days as modern SSDs can take a *ton* of use before they wear out.",
"Your hard drive isn't actually composed of files within folders. Instead, it's a small number of magnetic disks with tracks running around it (like an old vinyl record, except the tracks are a lot smaller). When you try to write a new file, the computer finds an un-used space and writes the data down. when you delete a file, the computer marks that spot on the disk as un-used. When you create and delete a bunch of files, you can end up with a mostly-full disk with a bunch of small holes in scattered spots throughout. If you have a particularly large file, there may not be a single contiguous space on the disk large enough to fit the whole file, even though there is enough empty space in total. Your computer is perfectly capable of handling this- it can fragment the file into multiple pieces and write each piece in a different spot. The downside of doing this is that reading fragmented files is slow- the disk has to rotate to one spot, read a chunk, rotate to a different spot, read the second chunk, rotate to a third spot for the third chunk, and so on. It would be much faster if the whole file was in one place and it didn't have to keep spinning the disk trying to find the next spot. Rotating the disk takes far more time than reading a block, so a fragmented file will take many times longer to read than a non-fragmented file. When you defragment a hard drive, your computer re-arranges where the files are on disk to clear a single contiguous spot for those big files so it can put them all in one place which makes reading those files much faster. This isn't really necessary for solid state drives, by the way- they can access any spot on the drive quickly, without the need to spin a disk like hard drives, so fragmented files aren't particularly slow on an SSD."
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6zjs8c | Why does running my microwave slow down the internet speed on my laptop? | I've noticed that every time I'm using the internet and the microwave at the same time that the internet slows down considerably or actually disconnects. I assume something about the microwave is interfering with the wifi in my house but I have no idea how any of that works. | Technology | explainlikeimfive | {
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"Many microwaves run at 2.4ghz, that means they blast out a lot of energy at 2.4ghz. Guess what also runs at 2.4ghz? Well, many home networks do (they also can run at 5ghz). So the microwave is screaming really loud at at the same sound as your home network makes, which means it can drown out the signal your computer needs to get wireless.... in other words, your microwave is jamming the signal by talking louder than your computer and router talk, so its hard for them to hear each other."
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6zl7yq | How the long exposure feature on DSLR Cameras work. | More specifically, how do the cameras capture pictures of the night sky? How long does the camera need to "take" the picture? | Technology | explainlikeimfive | {
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"Essentially, the camera is a light detector, and the more time the shutter stays open, the more light info it has. Then, using that info over time, the camera interpolates one image where the spots that were lit the most over time are the brightest and voila, more exposure. The problem with that, however, is that the camera doesn't really know what is real light and what is internal noise, so it tries to assume and remove it. As for how long the camera needs to stay open, it depends on a number of factors such as ISO, chosen aperture, etc. Essentially, you want to keep the shutter open for as long as you can, and darken the image using a high f number. I guess I'd like more info about what exactly your question is about. Something like this explains the camera settings: URL_0",
"Typically I use a 30 second exposure with the lens aperture wide open for a star field photograph. Even with a wide angle lens (21mm), a 30 second exposure will have the stars begin to trail a bit as the earth rotates."
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6zmojb | how does my computer "remember" what I've looked at and where I've been, tailoring ads etc based on those? | Technology | explainlikeimfive | {
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"Your computer does not remember and share a history of where you have been on the internet (it may retain a history for your own use) and it does not select ads for you to view. What it does do is retain a uniquely identifying label which can be used to track it between sites. Websites working together can share what they know you are accessing on their servers between themselves, but they don't know what else you do on other sites."
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6znw86 | Why does a game like Destiny require to be on their servers even when you just want to play solo | Why can't we play the game without an internet connection? If we want to play solo missions or strike, we can't. Isn't this a no brainer? | Technology | explainlikeimfive | {
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"For this type of game it's mostly an anti-cheat feature. Or else you could cheat a ton or create false data in single player mode offline, then log in later and exploit that against other online players using things you didn't earn. But some other games, very notably the disaster of SimCity, used it as a DRM-only thing and didn't truly require it.",
"Destiny isn't designed to be a single-player only game. Its designed from the ground up to be always online. Because of this very little is stored on your console. Your characters and all their gear are stored in Bungie servers, not on your console. The games systems aren't setup for it either. Servers control patrol area chests and public event timers, mission progression, enemy AI and physics, public spaces, etc.",
"It is an MMOFPS with some RPG elements. As an MMO it is designed to function on servers, you do not have the whole game on your device. There is no solo play concept for an MMO and there should not be."
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6zpaoj | Why on TV, do the voices and characters lips become out of sync and what fixes it? | Technology | explainlikeimfive | {
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"Not usually an issue with reliable feeds. Can I assume you're streaming?"
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6zpau8 | How do the components of a computer actually work, I.E. a CPU is just bits of metal, plastic and silicon, how does that actually make the computer work? | Technology | explainlikeimfive | {
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"Computers have two aspects. A mathematical model and physical implementation. First the mathematical model. All computers can be represented by a machine called a turing machine. All turing machines have memory (for example, a series of switches you can turn on/off) and a set of rules they work on. Let's say we have a series of 7 switches and you will follow those rules to flip the switches. Initially they are 0000000 (all off). Let's define the following rules: 1. flip the first 4 digits to whatever you want. 2. Take a look at digits 2 and 4. a. If they are both 0, do nothing and go to the next step b. If only 1 of them is 0, change digit 7 to 1 and go to the next step c. If both are 1, change digit 6 to 1 and go to the next step 3. Take a look at digits 1, 3, and 6. a. If 1 and 3 are 0, go to the next step b. If either 1 or 3 are 1 and 6 is a 1, change digit 5 to 1 and digit 6 to a 0, go to the next step c. If either 1 or 3 are 1 and 6 is a 0, change digit 6 to 1, go to the next step d. If both 1 and 3 are 1 and 6, change digit 5 to a 1., go to the next step 4. Stop, you're done What did we just make? We made a very simple turing machine called an adder. It adds 2 numbers together. Let's try running it. 1010000 After running the machine we get: 1010100 Take digits 1 and 2: 10 in binary = 2 in decimal Take digits 3 and 4: 10 in binary = 2 in decimal. Take digits 5, 6, and 7: 100 in binary = 4 in decimal. 2+2=4! With additional rules you can eventually make something that can do multiplication. With enough rules you can can flip another switch that will make power flow a battery to a light. (a turing machine's memory is just a set of switches right?) when someone pushes a button (once again, a button can just flip a switch!). With enough rules, you can make that light glow at different brightnesses (00 is off, 01 is a little bright, 10 is pretty bright, 11 is really bright). With enough rules, you can make a set of red, blue, and green lights light up with different brightnesses and make a colored light (100000 is red, 101000 is purple, 101100 is bluer purple, Hello color computer screens!). With enough rules, you can make a turing machine that can simulate any possible rule. With enough rules, you can chain together these simulated rules in any order a human wants to chain together (hello programming!). With enough rules reading from various switches (keyboards and mice will flip switches) and simulating other rules (a program) you can play a game or browse the internet (flipping switches on a display). So how does a computer work? First let's look at the rules. How do those translate into the physical world? The rules are scattered throughout your computer... but the biggest concentration of rules sits in the CPU. Transistors in the CPU will take two switches, do something, and will either flip or not flip another switch. There are different kinds of transistors, and we can arrange them so that they can do the rules we made above. In fact, we can make any rule by arranging the right transistors in the right pattern. Then there's the memory. The most obvious ones are your RAM and your hard drive. But your keyboard, mouse, monitor, and even your wifi card are all some form of memory. They either feed a series of switches to your rules, or they are used to show colors on your screen or send 1s and 0s halfway across the planet.",
"I took a course in this several years ago, so this might be slightly wrong, but it should give you a general idea. Lets start withthe CPU, the brains of the computer. In it is ~~thousands (millions? A frickin lot)~~ billions of conections that open and close depending on whether theres an electric current passing through, along with true/false, either, both, neither, and inverse gates. By mixing and matching the gates and the current you can do just about anything. These connections are incredibly tiny, hence the \"microprocessor\" you might have heard about in computers. The hard drive provides the opperating instructions for the CPU in the form of 1s and 0s (one being current, 0 being none) for processing. It stores data between sessions, and while it can be read fast, its not THE fastest in terms of read speed. Inside of a regular hard drive (HDD) are metal disks with slight magnetic charges, to provide the mentioned 1s and 0s. Theres also solid state hard drives, but i dont know exactly how those work. RAM (random access memory) is more like a collection of sticky notes on your desk than a library. You can read and write to it a hell of a lot faster than with a hard drive, but it wont keep that data between sessions. That should be enough to get the picture broad strokes, but if something doesnt make sense lemme know and I'll try to clarify."
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6zr06v | How Is Lossless Compression So Good? (Detailed) | To start off, yes, I know how it works, I know how specialized algorithms can do amazing things with ratios of 25% sometimes when time is not a concern. What I am asking is how it can get below 100% ratio in every situation that you would use it for. The reason why this is confusing for me is because I was thinking and I came up with a formula for testing how likely your file is going to be compressible. Example: Say you wanted to compress a set of 8 bits to 7 bits. 8 bits can represent 256 DIFFERENT values, while 7 bits can only represent 128 values. So that means that half of the files are IMPOSSIBLE to compress, even with 1GB files. So the formula that I made to see how likely your file is to compress is: **1/2^How-Many-Bits-You-Want-To-Compress ** **Now the question: ** How can 7-zip and other apps compress by multiples of mega-bytes when the chances of it being able to are astronomically high? *(This is a shower thought, let me know if I'm forgetting something.)* | Technology | explainlikeimfive | {
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"> Say you wanted to compress a set of 8 bits to 7 bits. 8 bits can represent 256 DIFFERENT values, while 7 bits can only represent 128 values. So that means that half of the files are IMPOSSIBLE to compress, even with 1GB files. You are absolutely correct, and this is the basic proof that not all files can be compressed by a given algorithm. Be proud you understand it, the professor who taught my data compression class did not. And it is even worse than that. Of the half that can be compressed, half can only be compressed by one bit. Have of what remain can only be compressed two bits, etc., etc. Only the tiniest fraction can be compressed to any significant degree. How can we compress anything? Because even a tinier fraction is going to be anything we would ever want to compress. There are about [36,000]( URL_0 ) ten letter words in English, from aardwolves to zymometers. But there are 141 million billion possible combinations, meaning 99.99999997% of them are gibberish. And thats just 10 letters, the longer you get, the lower the sense/nonsense ratio gets. Keeping that in mind, the chances of finding compressible data isn't nearly as astronomical as you might think.",
"> Example: Say you wanted to compress a set of 8 bits to 7 bits. 8 bits can represent 256 DIFFERENT values, while 7 bits can only represent 128 values. So that means that half of the files are IMPOSSIBLE to compress, even with 1GB files. The thing to remember is that the vast majority of \"all possible files\" are just garbage data that don't mean anything. Not every single possible arrangement of 1 gigabyte of data has any meaning. And files that actually mean things tend to have a lot of repetitive data that make them prone to compression. That said, you *are* right in realizing that not all files can be compressed. This generally crops up when someone tries to compress an already-compressed file. They will actually make the file *bigger*."
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6zznkt | When Apple says iPhone X has a "neural engine" what does this actually mean? | How does this "neural engine" differ from a normal CPU, like on the iPhone 7 or an Intel-powered laptop? Specifically, the keynote mentioned that the neural computations enabled their new FaceID system: > We take the IR image of the dot pattern and we push them through neural networks to create a mathematical model of your face. Then we check that mathematical model against the one we stored earlier and see if it's a match. Then later: > ...teams took over a billion images. With that they built multiple neural networks to create FaceID. In the process of building these neural networks, we built Apple's first neural engine. | Technology | explainlikeimfive | {
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"It's a bunch of marketing speak to make it sound mind-blowingly good. They used a neural network for facial recognition. Neural networks are extremely complicated mathematical functions that aim to emulate how a human brain works. It takes tonnes of input (such as the \"billions of pictures of faces\" and will use those to learn and understand what a face looks like computationally. What they mean by a \"neural engine\" is actually just an extremely powerful CPU that was custom-made for the phone and is built into the phone that can perform 600 billion operations per second (supposedly) which allows for the neural network to perform extremely fast and efficiently to improve the facial recognition a lot more."
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7009c5 | Apple just skipped the iPhone 9.. Windows did the same. Is there something I am missing something about the number 9? Is there anything superstitious? | Technology | explainlikeimfive | {
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"Ten is a subjectively significant number so people expect innovation, something new and game-changing. Nine being before this big change might be considered a less desirable and avoided as people wait for ten. In reality of course the iPhone X is going to be the first practical test of a bunch of technology which will be refined in the next version. But the marketing people saw the potential to get the jump on consumer psychology and took it.",
"Rumors which are allegedly less than rumors regarding windows 10, skipping 9, is that there is legacy code and such in the windows platform and using 9 caused issues with something in the system since windows previous had 95 and 98 numbered versions. This may or may not be true, but it would make reasonable sense if it was true. iPhone X as in 10, is because it’s the tenth anniversary phone (the original iPhone was released in 2007). They didn’t skip 9, they just made a creative name for their 10th anniversary."
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701kg9 | Is Richard Hendrick's decentralized internet concept from Silicon Valley possible? | In theory, what technology are we currently lacking that would be needed for it to work successfully? Also, wouldn't it be incredibly insecure, what with everyone walking around with everyone else's private data in a compressed file in their phone somewhere? | Technology | explainlikeimfive | {
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"It's not viable with our current infrastructure and devices. The method described on the show involves using other people's spare processing power and storage to handle information processing instead of a big server owned by a single company. Specifically, they try to use cell phones as the shared devices. The problem is that cell phones tend to have metered network connections and small batteries. So, people wouldn't want a distributed internet eating up their data plan and using up their battery life. The show hand waves this away with Richard's compression algorithm eliminating all of those problems. In real life there are limits to how much you can compress things. But, in general, cell phones are not built for serving data to other users and servers are. Servers are more efficient in terms of electricity costs, storage costs and processing costs. They can simply do those things cheaper per unit than a cell phone can because they were built for that purpose. If there was a magical algorithm that made everything faster, it would help servers more than it would help cell phones. However, the one thing that isn't a concern is security. You can simply encrypt your data before it is sent. So long as you hold on to the only copy of the private key you can be safe in knowing that no one else could get at your data."
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701tbe | Why can modern smartphones record video at such high frame rates while a dedicated DSLR in the similar price does not? | Technology | explainlikeimfive | {
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"Well, that may not be true any more: DSLRs in recent years have better video than they used to, since manufacturers realised that buyers want that too. Ten years ago, video on a typical DSLR was either absent or a gimmick. Now you can get a solid DSLR with lens for under $500 (before rebates), such as the Nikon D3300, Pentax K-S2, or Canon Rebel T6. The Nikon is the cheapest, and it can record 1080P @ 60 fps. The camera in a phone is just one component, but a DSLR camera is a system consisting of a body and an interchangeable lens of higher quality and flexibility than any typical phone camera lens. On a phone you have no control over the aperture so you can't control depth of field. The DSLR camera body is built as a tool for taking pictures, with knobs and buttons for that purpose, not a touchscreen. If you're serious about photos or video, you'll learn that pixel counts and frame rates are only a fraction of the picture. Analogy: if you buy a car, do you only care how big its engine is?",
"Shooting in high frame rate requires a fast processor to be able to handle all of that data coming off the sensor. Smartphones have been integrating faster and faster processors because it makes the entire phone faster. Being able to quickly compress and store high framerate video is a nice consequence of having a faster processor. Up until recently digital cameras didn't need to have very fast processors. The work they did just wasn't that demanding and they would rather put that money into other components. But, as people have started expecting to be able to shoot high frame rate video on their cameras the manufacturers have started putting faster processors which can accommodate that demand."
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702dru | Why is it such a big deal making new games run at 60 fps when a lot of shooters and other games have consistently run at 80-100 fps for years now. | Technology | explainlikeimfive | {
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"Think about a 5th grader in a 5th grade math class. The best students get A's. Above average students get B's. Medicore students get C's, etc. But even the C students in 5th grade know more math than most 4th graders. But they aren't judged by their knowledge of the easy topics they already know. They are judged by the new topics they are learning in their 5th grade class. In the same way, a low cost modern graphics card can run an old game at 80-100 FPS without too much difficulty. It's like a C 5th grader doing 4th grad math problems. But new games have more advanced graphics with more polygons, textures, and details. They require more computing power. So the A graphics cards can handle the new material at 60 FPS, and the C ones try to maintain 30 FPS. As soon as new, more powerful graphics cards are released, new games with nicer graphics are also released. That's why 30 FPS and 60FPS are always the benchmarks.",
"60fps is considered a minimum frame rate to have a smooth experience on PC. That particular number is relevant because most non-gaming monitors have 60hz as their native refresh rate. To get more frames per second than 60 requires turning off V-sync which leads to tearing. But, this is changing with the advent of high refresh rate monitors."
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70408a | Why is a black background and white text still not a norm in websites, apps?! | Technology | explainlikeimfive | {
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"It's because white background and black text has been the norm and is what everyone is used to. It was this way because digital displays replaced paper and ink and had to be similar to get people to adopt it.",
"Because you have to be concerned about accessibility. Not everyone can read dark mode well, that is why its an option. black background with white text is one step away from black background with matrix green text. It hurts the eyes of those with contacts/elderly and people with contrast issues. Look up WAVE."
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704vw7 | What is actually happening when you charge an electronic device? | Obviously the battery is being charged...but...what? | Technology | explainlikeimfive | {
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"Battery is made of two parts, cathode and anode, separated by insulator. Anode is where the electrons are. Movement of electrons (electric current) is what the device does. Every memory access or processor instruction can be traced to electrons going places. That part is complicated so lets get back to the battery. So, the anode is full of electrons and they want to go to the cathode. Why? Phisics tells them to. But there is the insulator in the way and the only way is to go around trough the complicated circuits of the device. Battery discharges. When you charge the battery you are using external power source to force the electrons from cathode back to the anode. Electrons don't want to, but external power source is stronger than their love for cathode."
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707npr | Why aren't the outer cases of phones made of the material added cases are made of? | Or have a an optional ridge that breaks the fall instead of the screen, like, my new phone dropped on asphalt b4 the screen could arrive, now it is drop proof (ish), why not have that built in? that is all i am asking. or have an extra cheap layer on top of screen made of glass that can be replaced? | Technology | explainlikeimfive | {
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"Because people want a \"premium feeling\" device, and/or they want to keep their phones in like-new condition. Apple has been making glass or metal phones since the original iPhone. While these are more fragile, they definitely give the phone a more premium look and feel. And while plastic or rubber is totally adequate, when people are dropping $500+ dollars on a phone, they appreciate nicer materials. HTC has also been making metal Android phones for some time, but the trend has really taken off since Samsung transitioned from plastic to glass on the S6. Now, even budget devices like the moto g5 and my £150 Xiaomi redmi note 3 are made from premium materials. Also, people are gonna put a case on it anyway, just to protect it. I had a moto g2 and that thing had a soft rubber back that was like a case. I dropped it plenty of times, and it held up fine. BUT, it also showed its wear over the years. The bat wing logo got somewhat scratched off, and there were scratches and dings on the corners and sides. If I had kept it in a case, it would have kept its like new condition. Now, if it did have a built in ridge like many cases do, it would have gotten scuffed and chipped. Unlike a case, I can't easily replace what's actually built onto the phone. > have an extra cheap layer on top of screen made of glass that can be replaced? Tempered glass screen protectors are super common and cheap, and I think a few manufacturers do include this. (I believe the OnePlus 3 came with a screen protector pre installed). You can buy them on Amazon for 50c-$1 each, or at a store for $5.",
"Some are. \"Rugged\" type phones meant for outdoor, military use, work sites, etc are on the market and are built with tough cases, dust proof buttons, etc Mass market phones are advertised as being every slimmer & lighter, and not everyone uses a cellphone in such a way as to risk breaking it if it's used without a case."
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709xcd | How do video game coders optimize their games to boost fps and stability? | Technology | explainlikeimfive | {
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"The basic method is they look at how long their code takes to perform each function and look to see if there are more efficient ways to perform that function. If you can do the same action with 5 calculations instead of 10 then you have double the speed of your code. If you can avoid having to read data from a slow hard drive and instead have it available in very fast graphics memory then you can similarly increase the performance of your game.",
"Hey there! I make games for a living. There are many ways that a game needs to be optimized, but the big three are CPU, GPU, and memory optimization. As you might expect, some of these optimizations tend to fight against each other, and all three of them often fight against the overall complexity or quality of the game. **GPU (rendering) optimization** is the process of making your game's graphics simple enough to be rendered very quickly by the user's graphics card / GPU. This is what most non-developers think of when talking about video game optimization, but in many cases, it is actually the easiest and least important form of optimization. Very few games, these days, are bottlenecked by rendering. The main ways that you improve a game's GPU optimization are: * Reduce the complexity of the graphics in your game (reduce polycount, simplify shaders) * Merge things together so they can all be rendered at once (static batching, texture atlases) * Hide or simplify things that don't need to be seen in full detail (occlusion culling, LOD) **CPU (processing) optimization** is the process of making your game's *code* run as fast as possible. This is arguably the hardest and most important form of optimization, and it's also one that varies tremendously from project to project. Generally speaking, though, CPU optimization involves lacing your code with timers and counters so you can see which parts of the code are running quickly, and which parts are running slowly. This is called \"profiling\", and a lot of engines have built-in tools to do it for you. As you profile, you identify which parts of your code are taking the longest to run, then you do one of three things: * Clean the code up to run more quickly. This is the easy method, but there's only so much cleaning up you can do. If your code is already squeaky clean and you still can't get it to run fast enough, then you have to resort to... * Rewrite the code or remove/simplify the feature entirely. Unless, of course, you can find some way to... * Offload the work to the GPU using very specific, clever tools. This is usually not an option, but it's the premise behind things like Hairworks and Flex. **Memory optimization** is the process of making your game take up as little of the user's memory/RAM as possible. In most cases, memory optimization is directly competing against CPU optimization. One of the fastest ways to speed up your code is to start pre-calculating a lot of things and saving them into memory. But if you start using too much memory, the game will crash on weaker computers.",
"It depends on a lot of factors, like what engine or self-built system you're using. For an FPS-related example, if you have a piece of code that checks for collisions, you're gonna have trouble keeping the game speedy if you have to check every object against every other object every frame. So one technique is to subdivide the level, cut areas into segments (a ball in room A obviously can't collide with anything in rooms C and onwards, so ignore those objects) and only check for collisions that seem 'plausible'. It's also quicker to check collisions with simplified shapes: to figure out if two spheres touch, you only have to know how far apart they are and the size of each sphere. So anything you can simplify will help, usually things that need to be done quickly like grenades and projectiles are calculated as spherical. With regards to 'stability', that's more about finding critical problems in the code or situations that haven't been accounted for. So if you find a way to open and close a door 1000 times in one second, and it crashes the game server, that's obviously an oversight somewhere between the inputs system (letting you spam the button that fast), processing the game logic (letting you send the 'open' command 1000 times to the door object), sending that instruction over the network (telling the game server to open the door) and then crashing the server because it only has enough memory to process 256 instructions in one frame. Ideally you'd anticipate this and put limits and safeguards so that the game can handle it, but it takes a lot of time and effort to handle absolutely everything a player could conceivably do."
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70amh4 | Why are manual cars becoming obsolete? | I've noticed that more and more cars are coming as automatics only, and not just everyday sedans, Ferraris and other super cars are basically all automatic. Why is this so? | Technology | explainlikeimfive | {
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"Because to most people the benefits of an automatic outweigh the benefits of a manual. Things like slightly improved(which has been equaled in all but the most infinitesimal ways by automatics) gas mileage, more control, the ability to push start, and \"the feel of driving\" and all that aren't big deals to most people. Not having to constantly move their hands and feet around in order to change speeds is. People like simplicity and ease, and \"push this pedal to go faster and this one to go slower\" is about as simple as you can get. \"Push this pedal and then slightly let up while pushing this other one while using this hand lever\" to move, and \"oh yeah make sure you're watching this dial and listening to the engine sounds so you can keep using that hand lever and other pedal while driving\" is frankly just a tedious pain in the ass to most people who just want to be somewhere else. And while car aficionados might not get it and don't agree, driving is, to the vast majority of people, somewhere between a chore and a necessary mundane task to get from point A to point B. There is no \"fun\" or \"pleasure\" aspect to it. It's that boring and sometimes stressful waiting period between where you were and where you want to be. Driving is the loading screen of life. Best to get it out of the way with the least hassle. Look how much people are eagerly anticipating driverless cars. Not only is the act of driving not fun to most people as is, they're pretty keen on removing themselves from the equation entirely and doing something, anything, else while they're moving from one place to another.",
"Because the benefits of a manual have equaled that of an automatic. Transmission life, gas mileage, price, etc.",
"Are there ? Here in Europe automatic car are still pretty rare. But may-be with modern computer we start to get automatic car that are as efficient and comfortable (from a european perspective) than manual..."
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70aw2f | How does face scanning work with twins? | Technology | explainlikeimfive | {
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"There are different methods of \"face scanning,\" but they all rely on nuances in physical appearance. (More advanced methods use the topography of the face and not just a comparison between images.) They can't distinguish between two different people that look essentially the same, anymore than a lock distinguishes between two people that have subtly different copies of a key. The accuracy of particular methods, and products that implement them, varies. Identical twins also vary in how alike they are--the environment does have an influence on how you look, not just your genes. But it's safe to say there's a significant potential for a scanner to fail to distinguish between identical twins. Ideally, biometric markers should never be relied upon for authentication, because you can't change them if they are compromised. They should be more like a user name than a password. But they can strengthen security if implemented alongside a secure authentication method, such as passwords, a key card, etc.",
"Over time things environmental factors have their affects on twins bodies. Reference: [ URL_0 ]( URL_0 )",
"I dated twins twice. (Twice, I dated a single twin from two unrelated sets of twins.) They don't look *the same* they look **similar**."
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70dmbn | What did humans do before the invention of toilet paper? | Technology | explainlikeimfive | {
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"Wealthy people wiped themselves with wool, lace or hemp, while less wealthy people used their hand when defecating into rivers, or cleaned themselves with various materials such as rags, wood shavings, leaves, grass, hay, stone, sand, moss, water, snow, maize, ferns, many plant husks, fruit skins, or seashells, and corncobs, depending upon the country and weather conditions or social customs. In Ancient Rome, a sponge on a stick was commonly used, and, after use, placed back in a pail of vinegar. Several talmudic sources indicating ancient Jewish practice refer to the use of small pebbles, often carried in a special bag, and also to the use of dry grass and of the smooth edges of broken pottery jugs.",
"Leaves definitely came in handy. The Ancient Greeks would often use pieces of clay, the Romans would use a wet sponge on a stick. The wealthy might afford some nice lace that a poor servant had to wash. Once printing presses became mainstream, using old newspapers or magazines was really popular - in fact, when the Sears catalog switched to glossy paper, they got a huge number of complaints, because of how many people kept a Sears catalog in their bathroom for reading and wiping purposes. But in all honesty... for most of human history, people just kinda stank. A handful of leaves or moss can only go so far, after all."
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70g5tk | How does google maps predict the effect traffic will have on my travel time so accurately? | I often use Google maps when driving and it always seems to accurately predict how long the trip will take, even when there is traffic or an accident. How does it know the severity of the traffic and how this will effect my travel time? | Technology | explainlikeimfive | {
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"When the app is running in someone's device, it calculates how much time takes to move from a to b and if it's out of standards Google send an alert for bad traffic once enough report have been given",
"Because while you are using Google maps, you are reporting back the current situation on the roads - for example if a lot of users are traveling along a particular stretch of road Google knows it will be busy, or of cars are moving slowly then it can tell there is some form of holdup and reroute people to avoid it."
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70hfvd | How do video games play "hide and seek"? The game knows where your position is, how does it act like it doesn't know where you are? | Technology | explainlikeimfive | {
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"The game knows where you are, but the AI doesn't. The AI has some information about its surroundings, but the game engine does not tell the AI where you are (unless it is cheating to make it more difficult). so the AI actually has to look and try and find you normally, using the information it actually gets from the game engine. Not all parts of a video game (or any program) has access to all other parts. The part that handles the AI is distinct from the part that handles the graphics which is distinct from the part that handles player controls. The AI part can't access information it does not own.",
"First you must understand that AI in gaming is used in the loosest sense possible. The AI is typically a term just applied to specific NPC actors within the game. It's simply a series of commands an actor follows in accordance with their surroundings. For every interval of time (cycles, ticks, etc), the actor will check what is around it in the game world. They might have a hearing range that is 2 meters, so instead of asking the game engine where the player is, they'll check if they hear a player within 2 meters of their position. They might have an invisible sight cone(really just a visualization of a geometric function that the actor runs) that projects 10 meters in front of them at 45 degrees, so they'll check if the player falls within that cone. Basically, the data is there and the actors could immediately access the player's location if that was the game designer's intent, but it's not as sporting or immersive as the actor seeking more conventional means to find you, like a clear line of sight or close proximity. Oh, or like a DM and a group of Dungeons & Dragons players. The game engine is like the DM; It knows all the stats, all the player's positions, and determines all the rules governing them, but the players still have to run Search checks and such by the DM. Sometimes a player will just give a DM numbers and the DM will translate that into \"You see a Dwarf\" or \"Hit\" or \"You step in a pile of horse dung.\" I guess you could scratch it up to compartmentalization of information.",
"Imagine you're playing hide and seek with your 3-year-old sister. Your sister is loud and terrible at hiding, so you know where she is every time without having to look. But she likes the game, so you want to play along and not find her immediately. You come up with a simple routine that you can follow every time, which will eventually find her: 1. Pick a random room in the house. 2. Look under every table and chair. 3. Look behind big objects. 4. Open closets and cabinets and big containers. 5. Go back to step 1. Sometimes you'll find her quickly, sometimes you won't, because your routine has nothing to do with where she actually is. You just follow the steps until you happen to find her. Your routine is a simple algorithm. Video games follow much more complicated algorithms, but the principle is the same. They aren't really \"trying\" to find you, they're trying to follow the steps of their algorithms.",
"They explained this for alien isolation. There is one \"brain\" that knows everything and sees where you are, and a second \"brain\" that actually controls the alien. The first brain sends HINTS about where you are without telling the alien too much information.",
"You've gotten some answers but none that are very \"ELI5\". You seem to be confusing the game itself with the enemies in the game. Of course the game itself knows where you are, but it's not against you. It wants you to play and sets challenges for you to overcome. The enemies in the game are the challenges but are bound by rules. As an analogy, the game itself is like a dungeon master in a tabletop RPG. He knows everything about your character and, if he liked, could just bring in an invulnerable dragon who kills you no matter what you do. But there's no fun in that. So the dragon has weaknesses. But just because the dungeon master put the dragon in front of you doesn't mean that the dragon can use all of the dungeon master's power at will. In the same vein, an enemy in a video game can't just access the knowledge of the game at large and know your every move. It's a slave to the game and can only work with what it's given.",
"The game behaves the way the programmer tells it to behave, and a subroutine within the code can only see what you allow it to see. Either it's passed all the information it needs when you invoke it, or it includes instructions to go and look in specific variables or request certain information from the system. It has no initiative, and only looks where you tell it to look.",
"The \"AI\" in video games is just a subroutine that chooses an action based on available information. It won't act on information that isn't sent to that subroutine, even if that information exists somewhere else in the program. So the game engine provides some way of defining the \"senses\" of AI-controlled entities, usually in terms of vision and maybe sound. So if the player character is hiding behind something, with an AI-controlled entity on the other side, then the rules for \"senses\" in the game engine will say that the AI-controlled entity cannot \"see\" the player character, and so the player's location is reported to the AI subroutine as \"unknown\", even though it is clearly known to the physics and graphics parts of the game. The AI will usually have some kind of \"fallback\" behavior in this case, either waiting where it is or walking around on some kind of search pattern until the game engine decides that it can \"see\" the player character. Basically, the AI in the game acts like a different \"player\" from the part of the game engine that basically serves as a \"referee\". The AI, like human players, can only act on limited information, whereas the \"referee\" parts of the game engine know everything that goes on in the game world, but does not cause \"cheating\" because it is impartial and does not act in the favor of either the player or the AI (assuming the game engine is designed to be \"fair\" in that way).",
"Software is designed in such a way that every part of it has to be explicitly \"allowed\" to talk to another part of it by design. Unless the programmers actually * Coded a way for another object to talk to it AND * Coded something into the other object that attempts to talk to the first object Those two things will just do their own thing without any direct conversation. Just because a game has a Soldier object wandering around doesn't mean that Soldier has access to the data that your Player object is storing about its own location. The Solder probably has some attributes such as * Position * Model / animation assets * Speed * Max Health * Current Health * Weapon * AI Rules / script * Etc. ------ Just like your Player object also has some attributes: * Location * Model / animation assets * Inventory * Velocity * Level * Current Health * Max Health * Etc. -------- The AI Script is simply a chunk of code attached to an enemy Soldier object. Rather: A Solider object has an \"HAS A\" relationship with that particular AI Script - The Solider HAS A \"SoldierAIScript\". This script is responsible for controlling what the Solider object does. The Soldier knows it has that AI script and it simply runs the code in that script. Note that this has nothing to do with directly accessing the Player object's \"Location\" attribute - That attribute is probably only being used by the game engine to draw your model and camera in the right place, maybe to trigger cutscenes/events - nothing more. Yes, AI could be coded in such a way to be able to access the player's \"Location\" attribute (though that would probably be bad coding practice unless you're using getters/setters...I won't get into that) but unless that was part of the design of the game there are probably more interesting ways to make an AI for your game.",
"The game isn't going to tell the players where you are if the game mode is hide and seek however if you're talking about bots then thats's a different story. Video game functions aren't all connected together, it's a bunch of different files of code, if you're talking about all the code then it most certainly knows where you are however the code for the bot doesn't know where you are unless you've given it the players location in the code.",
"Have you ever played Dungeons and Dragons? In DnD, the DM knows where the players and the monster are. The DM controls the monsters, but also keeps track of whether the monsters know you're there. It's the same in a video game, the game simulates the AI of the monsters but doesn't tell them where you are.",
"An attempt at a true ELI5: Imagine you're playing hide and seek with your parents. You hide, your dad seeks, and your mom just watches you both. Your parents know where you hid because your mom saw you hide. But as long as your dad doesn't ask your mom, then the person seeking doesn't know. Same in games: a part of the game knows where you are, but the part doing the seeking doesn't ask the part that knows where you are.",
"First of all, /u/amorousCephalopod provided a fantastic answer and this is basically the foundation on which AI lays. I will just elaborate with some encyclopedic knowledge just because I love sharing extra, useless stuff. The simplest implementation AI is based on a principle called the *finite state machine*. What this process really does is map all possible states of a system along with all possible transitions from state to state. In video game terms, let's say we are in a stealth game. As a *guard*, we have an AI agent with the states **Idle** , **Alert** , **Pursue** . The guard also has that imaginary cone Cephalopod talked about strapped on his nose, which the computer invisibly cross-checks for intersection with other game objects. If that other game object *happens* to be our protagonist, the computer will note that. He also has an invisible sphere around him which represent his auditory range and now works to 'capture' the sounds made by the protagonist. Anything outside that cone and sphere is artificially made oblivious to the guard. Think of it like the CPU is an omniscient being, a narrator if you like, that, for the sake of offering a challenge to the player, deprives the guard of that information, instead letting him get it on his own. The above cone and sphere represent the guard's senses. As in a real human being, there's a feedback cycle which accepts sensory input, processes it according to predefined rules, and produces actions. That's *also* a finite state machine, albeit more complex and populated with combinations of choices. So, here are practical examples: * Guard is smoking a cig. Player produces a sound *inside* the guard's auditory sphere. Guard investigates. (IDLE - > ALERT) * Guard investigates. Player intersects guard's vision cone. Guard chases after player (ALERT - > PURSUE) * Guard chases after player. Player hides. Guard gets bored and returns to smoking a cig. (PURSUE - > IDLE) * Guard is smoking a cig. Player intersects vision cone. Guard chases after player. (IDLE - > PURSUE) You get the idea. In fact, this may make you realize how *stupid the AI actually is*. It depends on pre-programmed variables and states to determine the next course of action; it isn't organic. But, as you add more and more complex interactions, it seems pretty darn smart. The computer might know your *exact* position, but for the sake of fun/challenge, lets its AI agents determine it for themselves. As a side note, there *are* ways to make the AI more realistic. In fact, if you've ever played Alien: Isolation, you'll notice that the Alien *adapts to your behavior*. This isn't possible with a good ol' finite state machine, as the name implies that the states are, well, finite. What happens in this case is that there's an algorithm which processes information and creates new states and transitions, according to input and extreme mathematical gymnastics which are way out of scope from this article. This technique is called **machine learning** and is employed in real world applications like self-navigating cars, robotic vision and even Google searches.",
"The game itself is a big collection of code and data. In the data is your position. So yes the game knows. But the AI is a specific routine. It's job is to simulate the actions of an intelligence. In a perfectly implemented example, it is only fed information it could see from it's own perspective. So, for example... a 3d fps game. It renders out what you can see each frame. Some things are behind other things and you can't see them. Everything behind a hill is hidden. So in our perfectly implemented AI, each AI might get a simple version of this pass that doesn't render a frame of video, but returns a list of objects the AI can see, and their visible size - a function of distance from the AI character and the size of the object. A few more steps. Filter this list down to objects that the AI might consider in its logic. The important stuff. Then work out a chance to see them and filter down to objects the AI notices. This could then be passed to another part of the AI that maintains state (what is the AI doing now? Wandering? Searching for ammo? Hunting? Is it scared? Angry? Aggressive? Chasing the player?) and makes decisions. You could do the same with audio. Can the AI hear the players footsteps? What if a plane is passing overhead? Maybe that would mask the sound. It's a bit like calculating a throw for sneak in D & D. Sound like a lot of work? It is. It won't scale very well. If we are checking what are all the things every AI can see and hear constantly then the computer is busy. We are taking up CPU cycles that could be used somewhere else and will make it run poorly on some hardware. Plus writing AI code is actually really hard and time consuming, and incredibly difficult to properly test. So the reality of AI is generally a bunch of heuristics. URL_0 > In computer science, artificial intelligence, and mathematical optimization, a heuristic (from Greek εὑρίσκω \"I find, discover\") is a technique designed for solving a problem more quickly when classic methods are too slow, or for finding an approximate solution when classic methods fail to find any exact solution. This is achieved by trading optimality, completeness, accuracy, or precision for speed. In a way, it can be considered a shortcut. So as we know from the start, the system does have all the information. Fast simple routines that get the AI to appear to simulate the whole process might be convincing 99% of the time. And if they have trouble? The movement routine always gets stuck on a certain type of landscape? Remove that landscape. You can tweak the AI and the world till it works together without getting stuck or doing strange things. But of course the heuristic might be poor. Not everything gets done right. Deadlines exist. At 4am, surrounded by coke cans a bleary eyed programmer might decide that in order to deliver by 9am, the heuristic for \"does the enemy see the player?\" Is when they are within a radius of 40 feet around the AI. Such a system will immediately cause visible issues. In a big open area, the AI wont see the player until they are close. In a building, the enemy will spot you through walls and rush in. Wall hacking AI. The convincing ones are harder to write and sometimes still have weaknesses that get discovered by the gaming community over many iterations. It is worth noting that game AI is generally not *real* AI, which is a whole field of study regarding emulating things that happen in a human brain. The future for game AI is probably in trainable *real* AI."
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70l2mh | How is power different than data to computer storage | So this question was actually asked by my cousin and I realized, I don't actually know the answer. So if data in a hard drive is supposed to be 1s and 0s, represented by electrons, why is there not 1 data+power cable? Why does electricity have to be provided separately then? How is the electrons going into the data side different than the electrons going into the power side? | Technology | explainlikeimfive | {
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"There are a couple things at work. First off, a computer 0 isn't exactly *zero* electricity. Rather, there is a voltage threshold above which is counted as a 1 and below which is counted as a 0. There are experiments with computers that have varied thresholds so that you can have 0, 1, 2, and 3...or indeed, theoretically as many digits as you want to represent. However, there are technical limitations - specifically, you have to have a range of acceptable voltages for each digit, and unfortunately our parts aren't precise enough without spending a *lot* of money to make the computer sensitive enough to be able to tell the difference without making mistakes. But that's not actually important. The important thing is that there isn't really *zero* power, it's just *very low* power - low enough that it won't jump across a semiconductor acting as an insulator. The other thing to note is that on a traditional hard disk drive, the data is not stored as electricity (ie: moving electrons), but as the changing magnetic field on a magnetized spinning metal disk. The read/write head is charged with electricity and can either detect the differences in the magnetic field or magnetize a part of the metal disk. In that way, while there must be power to read or write to the disk, no power is required to store the data once it's on the disk. Other forms of memory, like RAM, *do* require power to store the data. RAM uses capacitors to store a small electric charge that can be read by the computer, but that charge does have to be maintained with power. Very shortly after the power is turned off, the capacitors lose their charge and the data is lost. Solid state drives use transistors to store data in a way that does not require power: however, they wear out as they're used. They also require power to be read, of course. How each of those works precisely is another ELI5, though."
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70ll2b | How does a single microphone pick up sounds to send to a surround sound speaker system? | Technology | explainlikeimfive | {
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"That isn't how it usually works. There are usually a bunch of microphones that are recorded onto many tracks then mixed down for your surround sound system."
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70lnh0 | When a vehicle fails a smog check, why can driving it around an re-testing cause it to pass? | My dad's vehicle initially failed its smog check. The mechanic then had him drive the car for a few miles and re-tested, only to get another failed result. This was repeated 2 or 3 times, until it finally passed. The first time he had him drive it he told him to drive at 30mph, then at 45mph, and finally at 65mph. What was the rationale behind having him do this, and what actually happens inside the car by doing this? | Technology | explainlikeimfive | {
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"Cars have things called catalytic converters that turn really toxic gasses into not as toxic gasses. Catalytic converters work best when they are really hot. Sometimes when you go get a smog check your car sits for a while, causing the catalytic converters to cool down and not work as well. Driving the car around for a bit heated up the converters back to their operating temperature which allowed your dad's car to pass the smog test."
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70lszs | Why is the sigmoid function used in Neural Networks and what is it used for? | Technology | explainlikeimfive | {
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"This is a little more difficult to explain to a five-year-old, but I'll try. Neural networks work by seeing how close to a desired result you are, and assigning a weight to quantify that \"closeness\". For example, if you had an image of a dog, and your computer said that it's 95% sure it's a dog, then it would have a weight of 0.95. Where does the sigmoid function tie into this? You would pass into the sum of the weights multiplied by the inputs into this function. If they are super high, that function will output a value close to 1, while if they are super low, that function will output a value close to 0. Essentially, that function is what tells the computer how sure you are of whether the computer's guess is true or not. The function looks pretty weird, but the main purpose is to tell you how good of a guess your network made. (Bonus info if you know your calculus) The reason it involves e^x rather than some other function is because it's easy to find its derivative. The derivative of the sigmoid function at some point tells you how much you need to change. If you graph the function, you'll find that its slopes tend towards 0 if you go far out enough. So if you are 95% sure it's a dog, you will pass in a very high value into the sigmoid function. Its slope at that point is very flat, meaning that it doesn't need to change its weights that much (weights are the things that the neural network uses to make judgements as to whether it's a dog or not [whether it has fur, color, number of legs, etc.]). Similarly, if it's 5% sure it's a dog, and it's right, it also doesn't need to change that much because it's pretty confident that it knows what a dog is. However, if it's 50% sure, the network is very shaky. The derivative of the sigmoid function at that point is 1, which means that it needs to change by a lot. The network will then alter its weights by a lot to see if it can improve its guesses from there. I hope this answers your question, and DO NOT hesitate to follow up with further questions if this isn't clear!"
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70o6d4 | Why is the use of fully automated weapons (robots) such a moral issue? | Technology | explainlikeimfive | {
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"Using force that can potentially kill someone is a serious thing, and whenever that happens, we want to be able to hold anyone who does this accountable for their actions. When a machine does this, who is accountable? The creator? The manufacturer? The owner? If no one faces serious consequences for a wrongful death, then it essentially becomes a license to kill, and represents a menace to society. On the other hand, we don't want to send computer programmers to jail for unforeseeable flaws in the programs they write. How to protect society and hold the right people responsible has proven to be a difficult moral, ethical, and legal problem, not completely unlike what we are trying to do with self-driving cars.",
"The fear is in creating machines that take it upon themselves to determine what should and should not be destroyed. Drones, missiles, bombs... we have no shortage of things that can kill people, but they all require a person to make the final decision to shoot. Self-guided weapons also have moral issues: the same questions were raised when cruise missiles that came into use. The distinction here is that our current weapons will go out and kill what we tell them to. Fully automated weapons will go out and decide what to kill. I'm not sure if we should create such machines."
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70owzx | how is hd tv easily sent over the air with no loading/buffering but streaming hd video online takes a good internet connection and high bandwidth? | Curious how hd tv is easily sent over the air but hd video streaming online takes high bandwidth and a good internet connection. | Technology | explainlikeimfive | {
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"> Curious how hd tv is easily sent over the air but hd video streaming online takes high bandwidth and a good internet connection. A television broadcast is like talking into a loudspeaker system to address an entire stadium. Video streaming online is like holding an individual conversation with every person in the stadium simultaneously.",
"There is some buffering when receiving video OTA, the buffering happens immediately after tuning. With OTA the stream is always there, and it's always on, all you have to do is grab the first decipherable packet and start deciding, you know the next one will be along immediately because it's guaranteed, furthermore if you drop a packet there is nothing you can do about it, so the stream is encoded to be able to continue with minimum disruption but obvious glitches. With internet streams the computer fetches a bunch of data because it doesn't know for sure when the next packet is arriving, the connection might at any moment stop delivering packets for a few moments, so you have to have sufficient data available to ride the gap and this riding the gap /can/ be invisible if you don't run out of buffer, so streaming video will pause and recontinue from the same location because in some cases you can do it without the user noticing. Why the gaps happen is because the internet is a series of pipes of different diameter.... the wire from your house to the exchange can handle less traffic than the wire from the exchange upstream, so obviously when you request a big file somebody has to rate limit the transfer because the internet itself isn't going to hold huge files in transit, the way that any part of the network shows it's over capacity is to randomly not transmit a packet - so YouTube thinks it's sent you the next instalment, but you never receive it, think of what this would do to a game of chess by post, how do you know that your move has been lost in the post? The answer is to resend your last move if you don't get a timely response, but this delay when viewing video causes skips. The most obvious restriction you can ease is the one between yourself and the exchange, buying fast internet means less dropped packets which means less stalls and a faster refill of your video buffer.",
"Adding on to the other excellent answers here, I will add that traffic and contention are an issue. You are probably aware about how sometimes Internet traffic can get slower based on how many people are using it. This is a major cause of buffering with video streaming, because you're sharing almost the entire length of the connection with many other people. When you watch HD TV over the air, this isn't a concern. Nobody else is using that bandwidth. It's all 100% reserved for the television station. It's a specific frequency range that is legally reserved for them -- so they have all that bandwidth, every hour of the day, every day of the week. Also, it's broadcast, so your TV doesn't have to interact with the source of the transmission -- just pick up the signal and show it. This means that it doesn't matter if one person is watching it or a million. The full signal gets to you."
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70pe2b | Why does the military use mostly propellar aircrafts for cargo instead of jets? | Technology | explainlikeimfive | {
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"Prop-driven aircraft are generally cheaper to produce and maintain. Jets give obvious advantages for smoothness, speed, and altitude. But for a cargo plane, ability to land/take off in a shorter distance, to fly slower and at a lower altitude efficiently, and ability to do all of this with heavy load is more important."
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70sgiu | How are vector illustrations not based on pixels if our screen is made up of pixels? | From my understanding, a pixel is the smallest distinguishable unit on a digital monitor. So how can a vector not be pixel based? Isn't everything that's on our screen made up of pixels? So even if we're using a software like Adobe Illustrator, isn't a vector line made up of a bunch of small pixels in actuality? | Technology | explainlikeimfive | {
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"> So even if we're using a software like Adobe Illustrator, isn't a vector line made up of a bunch of small pixels in actuality? The vector itself is just a bit of math saying \"A line exists between point A and point B\". The resulting line is *displayed* using pixels, but the underlying mathematical representation means that you can display the same vector on a higher-resolution screen, and it would fully take advantage of the higher resolution by being drawn with more pixels. If the image itself were stored as pixels, then showing it on a higher resolution monitor would just make the image smaller, and not more detailed.",
"Rather than using literal pixel data (pixel by pixel with color data for each dot), vectors mathematically define the zones of a particular color. So a line might start at (0,0) and end at (0.35,0.75). The image can be whatever size you want. 10x10 pixels or 100000x100000 pixels. The computer calculates which pixels are part of the line defined by the vector. Vector graphics are independent of pixel count, so they can be made as big or as small as you need them. Vector graphics don't get blurry or pixelated as they get huge. Adobe represents your vector with pixels, but the actual line is more abstract and more \"pure\" if that concept makes sense.",
"Say you take a photograph of your cat and you develop that photograph. When you look at the photograph, it looks realistic. But if you zoom in on the photograph, you'll start seeing pixels. However, if in real life, you simply move closer to your cat and take another photograph, you'll now have a \"zoomed in\" version of the cat but with much more detail than the original photograph. Vector graphics are like the real-life cat. The photograph is a representation of the cat (the pixels drawn on the screen). The vector graphics, as well as the cat, have infinite detail, but the representation (photograph) does not. If you were to draw vector graphics on the screen and zoom in, *without redrawing the vector graphics from scratch*, you'll start seeing pixels. The idea behind vector graphics is that you keep redrawing the infinitely detailed vector graphics in pixels on the screen, thereby giving infinite zoom and details. Basically, you're taking a new \"photograph\" every time."
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70si9o | How do GPS apps such as Maps or Waze know the new formation of roads after construction? | Technology | explainlikeimfive | {
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"It first important to understand how Google Maps gets all if it's data. Some of it's data is pre-programmed into their systems. This is usually used as initial data, especially for testing. Google provides many more features, however. They also show traffic and other information for your daily traveler. A few years back, Google acquired Waze and they use data from the Waze app to enhance Google maps. Waze is backed by a community of users who report cops, traffic, accidents, etc. But Google also injects tracking into their software. Google can access the speed of your car by checking it's locations at two different points and dividing it by the time between those two points. If the speed limit on a road is 50 mph, but every car on the road using Google maps is moving only 10 mph, then there is obviously traffic. Using the same technique Google will track a cars movement. If a car is going off course, then Google will ignore the data, but still store it for later use. If 50 cars go off course, Google's map algorithm will detect this as an unknown road. Google will run several Artificial intelligence tasks to determine what is going on and will adjust their data accordingly.",
"Mostly, they get the information from various government sources, road databases, maps, traffic regulation databases and so on. Exactly what source that is depends on which country it is. In some cases, they also use OpenStreetMap as a source. That update cycle is usually kind of slow, though, maybe just a few times a year, so they also track vehicles. If enough vehicles move along the same line where there shouldn't be a road, they assume there is a road. Once they get a proper source for one of the \"car track generated\" roads, though, it's replaced by the proper road. Remember, roads are much more than just a line, it's traffic regulations, speed limits, lanes and so on."
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70ybnn | Why do people spend so much money on Computer/gaming glasses? Couldn't you just buy a pair of sunglasses? Like with a yellow/orange/gold glass? Please explain what the difference is... ty :-) | Technology | explainlikeimfive | {
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"Iirc, computer glasses are built different to prevent glare and increase contrast, while also protecting your eyes from the Blue Light emitted from digital screen. They usually aren't darkened like sunglasses are, and sunglasses are made to protect from UV rather than Blue Light"
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70yu89 | How do railguns work? | Technology | explainlikeimfive | {
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"A railgun is a device that uses electromagnetic force to launch high velocity projectiles, by means of a sliding armature that is accelerated along a pair of conductive rails. It is typically constructed as a weapon and the projectile normally does not contain explosives, relying on the projectile's high speed to inflict damage. The railgun uses a pair of parallel conductors, or rails, along which a sliding armature is accelerated by the electromagnetic effects of a current that flows down one rail, into the armature and then back along the other rail."
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710w7e | In a network breach (like the one in the news lately), how does the network security team know there's been a breach? | I'm a tech guy, but never really got into the netsec side, and I'm super curious. An article says "security team observed 'suspicious network traffic associated with its US online dispute portal web application...'" The breach had been happening for a while, so how was it suddenly discovered? What exactly is "suspicious network traffic", how did they find it, and how did they not see it earlier? | Technology | explainlikeimfive | {
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"Suspicious network traffic = The web server suddenly passing outgoing traffic to China or Russia. Or lots of odd entries in the server logs. Or a marked increase in traffic in general. Just things out of the ordinary. Why was it suddenly discovered? The odd network traffic. If you're a black hatter and suddenly you've discovered a hole in the network, you want to be quiet and just sniff around to see what you can find without triggering things. Then if you find a motherlode of chewy data, you want to get as much of it out as you can before you're found out, so you crank the outbound traffic to 11 to get all the data out before someone comes along and shuts you down. Or as happens sometimes, you pass on the \"Hey, I just found this hole in the super secret network\" on to your buddies and some jackass comes along and barges in, yelling and screaming at the top of his lungs.",
"A network is exactly like a land you buy. You need to put hurdles and entries so the people allowed to come in and out do so at the places you can monitor and those who aren't allowed still have to get throught the door. A fence is good enough but doors all have locks so the right locksmith can read the brand of the lock( the code of the firewall) and find the one who can unlock it. Once someone onlocks the door, there are still cameras( logs) showing who comes and goes but so does the 1000 other doors open for other apps so until someone actually pays attention to it, they will only see lots of people coming and going on 1000 screens at the same time. Now as for the massive leak there are lots of hearsays including that the tool the hackers used had a solution that was available back in march. Still, there should have been some code used by the sysadmins to manage and notify what is out of the ordinary. Laid back Admins can basically block some web sites as they cause problem or do not fit with the work environment. Strict admins, depending on the size of the company can block every thing then allow access per Mac address( like a device serial number instead of the IP adress that is more of a changeable licence plate). Then they can set and average usage per department and then let themselves be notified if some secret data from specific hard drives is being sent around. In all cases, this is ambarassing that someone got paid while this happened under their watch. You should lurk in /r/sysadmin to get their take on this."
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710y27 | why can xbox one x run some games at 4k60 and cost 500 while a gtx 1080 ti struggles to hit 4k60 on newer titles and cost $700? | Why can the xbox one x run some games at 4k 60 fps and cost $500 while a gtx 1080 ti can barely run newer games at 4k 60 fps and cost 700 dollars? | Technology | explainlikeimfive | {
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"4k doesn't mean shit if you've downscaled all the graphics. Put all the settings on low on a PC and you'll have no problem running the game in 4k. I can look at a pixel drawing in 4k. It's going to look exactly the same in 1080p. 4k is just a buzz word....",
"Because games for consoles are specifically toned down so that they can run at 60fps. Graphically its inferior. The PC game is made to be as good as it can be, and if someones PC cant play it? Tough you need to upgrade your PC. Its the difference in the markets.",
"Very few games run at 4K60 on the Xbox One X. Most are running at 1440p, 1800p or somewhere in between and then upscaled to 4K using a modern technique called \"checker-boarding\", which results in vastly better visuals than old upscaling methods. There are a few exceptions. Forza 7 (for example) will run natively at 4K60, but driving games are always computationally easy - the player's car needs a lot of detail but the scenery is usually passing you at 150mph. The GPU in the Xbox One X is roughly on par with a GTX1070, which costs about £350. Consoles usually cheap out on some critical components like storage and cooling, which leads to their horrendous loading times and (in some cases) high failure rate. It does mean the One X can be sold for £500, though.",
"One of the advantages of consoles versus PC is that the developers making a console game know *exactly* what hardware and firmware are being used. Additionally, the console is designed to do exactly one thing: run games or software that's been designed to run on it. PCs have to account for an infinite combination of GPUs, CPUs, RAM, hard drive types, operating systems, versions of those operating systems, background tasks, etc. The cost isn't just power, but versatility.",
"The hardware of a console is made to do only that, while a PC may have other bottle necks than the graphics card. Furthermore, since the game developers know the exact hardware the game will run at, they'll customize the settings so it runs well. The output resolution may be 4k60 but perhaps they have decreased quality somewhere else instead to make sure it runs smoothly."
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7111l8 | Why can't movies be offered on release date for more money at a premium for home viewing? | Technology | explainlikeimfive | {
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"- You can lend it around and have an entire community see it within the first week. - You can rip it and seed it and have DVD HD versions flood the market within the first week of the movie's release. - The cinema chain that you have a deal with will lose out on ticket sales and food and beverage sales, which will cost you a lot more in the future to screen your movie at their locations due to loss revenue.",
"> I spent a lot of money on my home theater Not as much as [Prima Cinema]( URL_0 ) wants you to though I'm guessing. The numbers are supposedly something like $35k for the hardware plus $500 per movie. Go for it ... or go back to the cinema like everyone else. Movie companies are of the opinion that they make more money with an exclusive-to-cinemas period. Periodically people try to change their minds (there are rumours that Apple is working on this now) but so far, no dice. In addition, cinema chains seem unlikely to go down without a fight and could try to punish any studio that goes it alone."
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711qt1 | When copying files, why does it always seem to start off really fast, but then slows down so much? | When copying files it always looks like it starts off with high speed, but then copying speeds drop dramatically and the graph just looks like a plateau. | Technology | explainlikeimfive | {
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"There is a limit to how fast you can read and write data on a disk. However to reduce the latency of the disk there is usually different types of caches in the pipeline that can speed up small data transfers. This makes the disk feel faster for regular use but does not help for larger file transfers that is bigger then the caches.",
"When you download, you first transfer the files in the cache. The file taken for this transfer is based on the volume of data and that's on this operation that the time of transfer is estimated. The last operation consist to index the files on your HD. This operation takes more or less time based on the number of files. It's not based on your bandwidth but on your cpu. If you download many files it can take more time than account for at the beginning of the transfer.",
"If I'm understanding your question, you're referring to the indicator on your computer that shows you how fast the files are being copied. This can either be a percentage or a time, and at first, the numbers seem to fly by! Once they slow to a crawl, you might be left wondering why. The files copy at the same rate; it is the indicator itself that is changing. It is catching up to the actual rate at which the files are downloading."
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712012 | Trains seem like no-brainers for total automation, so why is all the focus on Cars and trucks instead when they seem so much more complicated, and what's preventing the train from being 100% automated? | Technology | explainlikeimfive | {
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"I've been a Locomotive Engineer for the BNSF Railway for 10 years. The first answer to your question is that the Brotherhood of Locomotive Engineers and Trainmen (Engineers Union) is the oldest in the country at 152 years and we have fought tooth and nail to keep our jobs. That being said, the second answer is a little more complicated. The bulk of modern road locomotives are manufactured by General Electric. A road Locomotive is a six axle 4400 horsepower engine that is meant to travel at track speed between cities. This is opposed to a yard Locomotive which is four axles and only meant to travel at 10 mph in short intervals though it is capable of track speed (up to 70mph). A General Electric Locomotive comes with proprietary software in the locomotives heads up display called the GE Trip Optomizer. The T.O. as we call it is essentially auto pilot. Once engaged, it is capable of speeding up or slowing down the train at speeds of 12-70 mph. It uses algorithms to determine how to handle the train in the most fuel efficient manner while managing \"in train forces,\" but more on that later. The T.O. Uses GPS to determine exact locations to comply with both permanent and temporary speed restrictions. In my experience the T.O. Is accurate within 50 feet which is nothing short of miraculous considering the computer has to discern variables such as train tonnage (weight) both as a whole and individual cars and where they are placed in the train. Also train length and curvature of the territory. Whether or not you are on an ascending or descending grade (up a Mountain or down one). As an Engineer in 2017 I am needed at the controls of a Locomotive for the following reasons. First, T.O. Doesn't always work, nor is it present in all of our locomotives (some are made by EMD.) Second, T.O. Doesn't work at speeds below 12 mph, so I have to start the train out and then engage the T.O. Once I get over 12. Third, T.O. Only works when I have authority to travel at track speed for a great distance. For example, if I have authority for 6 miles or more, I will engage the T.O. If I have to stop at some point within about six miles, I have to take control of the train and get it stopped at the correct location while complying with good train handling procedures. The T.O. Is only able to operate at maximum authorized speed all the time. It does not stop the train. That is the job of an engineer. Imagine a self driving car that can only handle itself on Interstate highways at the posted speed limit and cannot drive down a street with traffic lights and comply with the signals. Same concept. Stopping the train without snapping it in two is the main job of a Locomotive Engineer. It's like a musician making music with an instrument. It takes training and experience. There are two types of brakes used on a train. First are the Dynamic Brakes, which are only found on Locomotives. That is where each axle acts as an electric generator. Imagine a hand crank emergency radio or flashlight. When you turn the crank there is resistance on the handle which is generating power. We use the resistance on each axle to slow down the train by generating electricity. We then literally throw away all that valuable electricity by dissipating it as heat out the top of the engine. It's a tremendous waste but hey, that's how we roll in America. The second type of brakes that we use and probably the biggest reason to keep trains manned is the Westinghouse Air Brake System. Each rail car is equipped with brake rigging which operates entirely on compressed air. There are no electrical components, everything is mechanical. There are air compressors on the locomotives that are connected to each car through the use of air hoses and the entire system is controlled by the engineer at the head end of the train. The speed of the train can be controlled by either taking away air (setting the brakes) or adding air (releasing the brakes). I know that sounds backwards but that's how the system was designed. It is the Westinghouse air brake design that truly throws a wrench into the need for automation. You see, Westinghouse designed this system in the 19th century. That's right, the flipping 1800s. The Titans of industry at the time began to expand the railroads so rapidly that there was only time enough to redesign the system to be more efficient once. That also happened in the 1800s. So that means that in 2017 we still use this system to stop our trains. Every rail car on every piece of track in the United States has this type of brake rigging. And according to federal law, each car has to have tested, inspected and working air brakes BEFORE the train departs it's initial terminal. A Conductor, (that's the other guy in the cab) has to walk the entire length of the train three times before the train can depart, once on each side to ensure the brakes are set and once to ensure the brakes have released. That could be up to 7000+ feet three times (5280 feet in a mile!) The Westinghouse air brake system, although used industry wide, has its flaws. The brakes have a tendency to \"dynamite\" or begin braking without warning. Imagine the brake on the rear car braking a full capacity and no other brakes in the train are working. This type of event cracks the whole train like a whip and the Conductor and Engineer are at the tip. At the very least we'll get greasy face prints on the windshield. At the worst we're looking at a train broken in two or possibly a derailment. In the remote locations that the railroad travels in, it is the job of trained professionals like us to inspect the train, possibly change a broken knuckle on a car (60 lbs), put the train back together (do another air test) and get on our way. In using a temperamental system like this it falls upon he job of a human being to orchestrate the movements of the train through the use of his senses. Feel, what's going on behind you? Is there more slack in the train than you expected? Sound, are the brakes squealing? Is it possible that they are not all the way released? Smell, do you smell hot brake shoes? The smell of burnt rubber? Sight, look back at the train on a curve. Is it on fire? Is there dragging equipment? Taste, what's in my lunchbox? Is it time to put my steak and potato in the engine compartment to heat it up yet? These are things that automation cannot replace, human intuition in the middle of nowhere.",
"Lots of good comments here, about the non-deterministic things that humans do, the stakes (hundreds of passengers), and the remarkable extent to which trains are already automated. However, there's one thing I don't see here yet: How much more efficiency can you gain by eliminating people entirely from trains? If a train carries 500 passengers or 100 cars of cargo, and has a technical staff (i.e. driving, navigating, communicating) of three or four, we're not going to change economies much by eliminating those three or four people.",
"Trains are almost 100% automated. Control of railroad switches is more and more centralized. Building of the rail path is automated. Most of the railroad staff is there just in case the automatic system fails or power outage. Railroad companies know that even if they automatize it further it will not reduce the staff significantly so they aren't pushing for more automatization anymore.",
"The answer depends slightly on the region we're talking about, so I'll focus on the one I know most about, Europe. Things might differ slightly elsewhere. It's also going to be a bit more technical in nature. **TL;DR:** It's much more expensive and difficult to automate trains, because of regulations, the lifespan of the rolling stock, and the infrastructure involved. As others have already mentioned, a huge chunk (if not everything in someplaces) of the actual railway infrastructure is already automated, such as signals and switches. Computers have made humans mostly obsolete there already: We've used to have many and big mechanical systems to prevent mistakes, today it's a single computer easily dealing with large regions of the network. Europe strives to have [an unified system (ETCS)]( URL_0 ) which controls trains (and their safety measures), which means that a train can go from one point of Europe to the other without having to switch engines or even drivers. There are multiple levels, which bluntly put refer to the available technology on the rolling stock and the infrastructure. The lowest level is still using the \"normal\" signals, whereas the highest levels are not using signals at all, but requires trains to have a constant radio connection to a control center. Lower ETCS levels do not offer you much choice in the way of automation, higher levels do. However, this is costly, as you need to upgrade your engines (which can easily last 50 or more years, and are expensive to replace) and add additional security infrastructure (cell towers to provide the radio connectivity). Depending on your geography, the latter can be tricky. So one point is the cost of actually getting a system that we can safely automate. Another one is trust. Put differently, when asked \"Would you like to enter a metal box that's going very fast next to other boxes that are going very fast, and all these boxes are controlled by some computer very far away?\", the answers you would get would probably be rather... conservative. Even with the amount of security we have these days, the software still has (smaller) flukes from time to time. A trained human operator can notice these mistakes and question the computer's decision, something that computers themselves have a harder time to do. Another one is the security bit. Train tracks are often exposed due to their nature, and might even include dangerous zones such as railroad crossings or stations without under-/overpasses. A human driver can see those dangers and act accordingly. More importantly, they can see it on other tracks as well and warn other drivers. Because there's no real guide to how to build rail networks and most of that stuff has grown historically in any case, it's difficult to teach a computer to do that. It gets even worse when you consider that sometimes obstacles are allowed between tracks - for example posts for overhead wires, or signals. In addition to that, the age of the rolling stock comes into play again. One part of being a train driver is to check the train for anything suspicious during the journey, especially on freight waggons. This can include brakes or axles that are running hot, or tarpaulins that have loosened and are now threatening to touch something (e.g. the overhead wires). We have systems on the railway tracks that can detect those, but not everywhere (they are usually placed in front of tunnels or terminus train stations), and they can't detect everything. The rail cars themselves are usually old and feature little to no technology in that regard, especially since they're usually used internationally and regulations (and therefore standards) vary from country to country. Which brings me to the regulations: Depending on your country, railways are more or less regulated. Some of these regulations may make automation impossible, or just way too expensive. Especially if there was no push towards automation so far, chances are that some law changes will be required before you can even start thinking about upgrading.",
"Trains tend to already be fairly automated depending on where you live. However trains tend to also carry a lot of people. Having one person per 200 passengers sit at the controls just in case is a lot less of a burden than having one person per 2 passengers at the helm in cars.",
"I've answered this question once here regarding main rail (non subway trains) here [ URL_1 ]( URL_1 ) To get straight to the point, nothing is preventing them and there are in fact a lot of automated train systems in place in an urban rail setting, some with more automation than others. First off lets see some examples of completely automated systems like the [Vancouver SkyTrain]( URL_0 ) and the [Morgantown PRT]( URL_2 ). Now why aren't all urban rail systems automated? Well there two main reason for it, the first is that there is a massive upfront cost to doing so though I'm sure many companies are working on dropping the cost like crazy and making the automated better. The second reason is unfortunately Unions. There are a crazy amount of extremely expensive automated rail systems both fully implemented and partially that exist but simply are not activated due to unions fighting them. Train drivers will first start seeing more and more of their controls automated before finally just sitting there watching the train controlling itself ready to intervene in case of any issues. Sooner or later though the drivers will lose out of their role and be transferred to a \"train supervisor\" type role to make sure everything is a-okay and to answer questions to passengers. So why don't you know about them? Well the truth is because you aren't the client. No one is trying to sell you an automated train system. These systems are being shown off and sold to the people who own the trains whether they be large private businesses or cities. Cars on the other hand are being shown off and advertised because sooner or later they will be on the market for you. Cars will eventually be self driving, a decent portion of trains (especially urban rail) already are and there's a greater push for it happening behind closed doors than the public sees. In my personal opinion, the majority of urban rain will become self driving far sooner than the majority of cars become self driving.",
"Some are. URL_0 As an example. The \"AnsaldoBreda Driverless Metro\" is in Brescia, Copenhagen, Milan, Rome, Thessaloniki, Taipei, and the Princess Nora bint Abdul Rahman University currently. URL_1 I am sure there is many other kinds of automated trains out there. edit: URL_2",
"Cost, time, and cost-benefit mostly. Automated cars can use existing roads. Automated trains need capable signalling installing along the entire track. From a purely technical point of view,we could have automated trains but if it costs $4bn to upgrade a line, and only $400,000 p.a. in staff costs to run it unautomated, then you could run it for ten thousand years and still save money, so you're not going to do anything else",
"Unions. At least in the UK. The RMT are a bunch of total fucks, and the very idea of the operators reducing the workforce just leads to everyone else going on strike. Currently, Southern want to reduce the amount of jobs the guard has to do (because technology has made it easier) so we've had a year of bullshit strikes from the guards and drivers. They refuse to accept the future.",
"Because the manpower that would be neutralized is so marginal as to be barely worth the investment. You're already hauling tens of thousands of tonnes of freight with a handful of employees. Shaving one or two more off that figure won't drastically reduce your costs.",
"Trains are already largely automated, at least on the road. Two people run most trains in the USA, the Engineer and his Conductor. Together, the monitor/control anywhere from a few cars to several hundred. There are several issues with totally automating trains. Computers are fairly good at handling expected situations, they fail miserably at handling the unexpected. People on the other hand excel at pulling information out of noise and acting. It might not always be the most optimal, but generally it is an improvement. Then we have to look at the possibility of hacking your train system. You can't hack people. While they can be fooled by switch information that is wrong, they'll typically react to a situation where they have conflicting inputs. An automated system might not do as well, or it might be the target of the attack. One final note: In the USA, the vast majority of trains are freight trains. Automated systems might be able to handle decoupling cars, but until robots get far better, those air hoses are cheaper and easier to be coupled by someone walking the train than they would otherwise. Railcars might go in and out of several yards, getting rearranged to meet traffic and their intended destination before finally arriving. At each of those points, the cars are disconnected, and reconnected. This is largely unseen by the public, but it is an important part of the problem. The Bailey Yard near North Platte NE handles some 14,000 railcars/day, a significant portion of which will be coupled/uncoupled as they pass through.",
"Trains... automation... Factorio... cars... trucks? Hey, this isn't r/factorio",
"Depends what rail you're talking about. Urban rail, subways, people movers can be and are fully automated. Since they typically run a standard route with two tracks one up one down then it can be automated fairly easily, relatively speaking. Freight and mainline rail is a whole different beast. (Which I don't know about). I do know that they are starting to implement automated safety systems. The problem with mainline is that you have a massive amount of different trains that share track and often times single track combined with expansive rail lines talking cross country here, the logistics of it don't make it financially viable (yet) The main place of automation for mainline are with respect to safety systems automatic speed control, emergency braking. Systems engineer for Thales rail signaling worked on TTC, Hyderabad, London Underground, Docklands Light Rail and currently working on a project in Qatar that is fully automated.",
"In the United States: 1. Many aspects of train operation *are* [automated]( URL_3 ). For instance in railyards there are automated locomotives for shifting cars around. There's also a thing called [positive train control]( URL_1 ) which allows for slowing and stopping trains automatically if something goes wrong, like if the engineer has a heart attack. We are in the process of rolling this out across the United States (I helped a little!) but it's a big job and there have been some delaying factors. Another part of the issue is that a lot of rail is waaaaay out in the middle of nowhere, so upgrading it with new infrastructure is expensive and time-consuming. That's why a lot of these upgrades have been made on railyards in cities, but not everywhere else. 2. It's not the no-brainer that you think it is. There are lots of unpredictable things that can happen when operating trains. There need to be humans on hand to deal with those things. Also, consequences of a train screw-up are much bigger than consequences of a car crash; consider that a single train might be hauling hundreds of tons of toxic, flammable or hazardous chemicals, and so you need [detailed safety plans in place]( URL_0 ) in case [something goes wrong]( URL_2 ). For that reason, you don't want to introduce full automation out on the rails until you have it worked out really, really well.",
"I am a locomotive engineer for a diesel passenger train in the Bay Area. There is nothing automated about my job. Most switches are lined by a dispatcher. Some have to be thrown by the conductors. I manually control the throttle and brakes, I trouble shoot and manually override things when I need to. On the train with me are two conductors who deal with passengers and open doors. They manually inspect brake when there is an emergency brake application and coordinate reverse moves when need be. We run at 79mph and routinely carry 1,000 passengers. We operate on a line that also has freight on it. They manually cut and build consists all day long, throwing switches and moving equipment back and forth. Automation could take over some if not all of it, but we aren't anywhere near that. Edited the brakes.",
"I know that here in the U.K., a major public opinion is that the main contributor to preventing the full automation of the London Underground is the Trade Unions. Underground drivers have a very active union who aren't afraid to call strikes and fight for their members. It's a question I've often asked myself as apparently underground drivers are on around £50k+ so automating this would seem like a major cost save.",
"There's always going to need to be a minimum of one person per train. I'm still not entirely sure how you could manage a train with less than two, though. I'm a qualified engineer and conductor. Say, you're going along and PSSSSH all of a sudden your mile long train goes \"into emergency\". What do you do? Your train is not going to move. You MUST send a crew member out to walk the train and find out what went wrong. Oh, a half mile back a car ran into your train and derailed 3 cars. That crew member now needs to be in contact with his dispatcher, engineer and yard master if necessary. Action needs to be taken. Directions given. Info needs to be shared with emergency personnel arriving on scene. You are also providing emergency personnel info about the hazardous materials which are in your train. Maybe the train simply broke apart, instead of derailing. The conductor, who just walked half mile of train, needs to replace a broken knuckle and get train charged back up. He may be able to call for a knuckle to be brought to him, but he may have to walk the half mile back up to the engine, walk the half mile back to the gap with the 70# knuckle, fix gap and then walk the half mile to rear of train to conduct an air brake test which would involve twice walking the length of the train to inspect that brakes are set and once for a release. The engineer is, of course, on the engine following directions to back up or come ahead to make the joint and also to set and release brakes. How you'd do this without 2 member crews is beyond me.",
"I just want to point out that it just makes mathematic and economic sense to focus on wheeled transport, seeing as the driver to passenger ratio is so skewed compared to trains/light railway. Here is a rough ratio of passengers to driver Train 200-1000:1 Bus 20-80:1 Car 1-5:1 So for every 1000 passengers by bus you have between 12.5-50 drivers, and by car 200-1000. That is why there is such a focus on bringing these numbers down. Added to this, like many people have mentioned, trains/light railway already are 95% automated and the drivers are really only there as a safety precaution.",
"Think about it not from the perspective of the people using the vehicle but instead from the perspective of the people making the vehicle. There are relatively few trains in the world and they aren't purchased very often. There are billions of cars in the world and people are always buying more. If you want to spend a lot of time and money developing a new automated vehicle, which market would you want to sell to?",
"The idea that cars will be fully automated in anything less that 20 years is farcical for exactly the reasons coming up in this thread. The regulation for how self driving cars will be governed has only begun to be tackled. Most likely, what will occur is we will have a long and drawn out process where trains and cars will both slowy become fully automated concurrently and technology developed for one will feed into the other. Trains will likely be the first to go fully automated and cars will have what will first of all be advanced safety features built in. There will then be a gradual, but slow adoption of this technology throughout the car industry, but there will still be a human driver who will ultimately be in charge of the car. During that time public opinion will build for self driving also. As time goes on, cars will take over more and more duties, the systems will be tested, laws and regulation will be developed etc etc., but we are still a long long long way away from self driving. But no one is simply going to unleash automated cars on the roads without this transition period.",
"Think of it in term of competitive advantage if you will. There's 1 conductor for an entire train so replacing that 1 person only saves you their salary/benefits/pension. In contrast, you need dozens upon dozens of tractor trailers to equal 1 train. Each of those tractor trailer combinations require a driver. Let's say it's 100 trailers to 1 train. That's a saving of 100 driver's wages. So you're getting a 100 time advantage over competitor's in trucking in contrast to a single individual's wages over competitors for rail.",
"I work at a railway and drive freight trains. - repairs - if something goes wrong the engineer can troubleshoot basic problems or sometimes advanced ones with the help of a mechanic over the phone or radio. - repairs extended - if the train derails or is pulled apart (a knuckle or drawbar breaks) someone (the conductor) needs to go back and fix it. Even computer controlled trains make mistakes and break apart, they can be improved in the future but the current implementation isn't perfect. (We already have a partial implementation similar to autopilot for \"cruising\") - departing/yarding - trains need to do some work when departing or yarding that would require manual help until much into the future when the infrastructure is there to be automated. This could be done by people already at the terminals, but you already have the guys on the train so why not them. - software cost. You better believe it won't be cheap for them. Apparently they are working on it in the USA but it is very expensive. I live in Canada and it sounds like they don't want to buy the software. - cost savings - They are only paying 2 employees to run a train. They won't be saving much by getting rid of us. - medical emergencies - you can't have only 1 guy either in the case a medical emergency happens there will be nobody to assist him. You'll probably ask why don't they just call an emergency mechanic when things break. Well trains can have problems in the middle of nowhere, it could take many hours for them to arrive and the mainline being shutdown for any period of time at all is extremely costly for the company. It's better to just pay us to be onboard. (Only 2 of us) I'm also qualified as an RTC and let me tell you that wouldn't be easy to automate. The basic idea of moving and yarding trains could be automated pretty simply, but if anything ever deviates or plans change and the computer needs to problem solve it makes it much much harder. I'm not saying it's impossible, the work being done in the AI field is amazing. But it's nowhere near as easy as you might think.",
"Washington DC Metro has a 100% Automatic Train Control (ATC) system. It had a lot of issues, [including the Jun 2009 train collision that killed 9]( URL_0 ). The crash was due to a faulty track circuit, making one of the trains invisible to the others.",
"Because when I was 6 I went on a steam train and the driver cooked me a sausage on the coal shovel, drivers are ok in my books DOWN WITH THE MACHINES, RISE UP REEEEEEEEE",
"Here's an explanation that's a little more basic. A semi weighs 20 tons, so each driver is responsible for moving 20 tons of weight. A train weighs 20 thousand tons, and there are 2 drivers, so each person is responsible for moving 10 thousand tons of weight. If you only had to worry about hiring one driver to move 500 semi trailers, instead of one driver for each trailer, you wouldn't worry so much about what the salary of the driver costs. tldr - Train drivers are WAY cheaper per ton.",
"A huge factor is unions. I live in Vancouver, which we have a fully automated rapid transit system. There is another one in Scarborough, Ontario, which uses the exact same technology, just with older rolling stock. While the trains are more or less automated, unions firmly opposed the trains being driverless. As a result, the trains retained one operator, who just sits there, monitors the operations of the train, and operates the doors. In Vancouver, we have attendants who mostly just hang out around the stations, acting as security and customer service agents, and are trained (no pun intended) to drive the trains manually in the event something fucks up.",
"To add perspective to answers most people are giving, my dad is a mechanic for the Automated train system at O'Hare Airport in Chicago. The system is complex, but also on a very small scale. There's maybe five miles of track in total, with the train network just bringing people between the terminals. So, the system is expensive. The trains cost more than most, and they are imported to the US, so getting parts can be lengthy and expensive. On top of that, the maintenance schedule is rigorous and costly, with every part having to be maintained at a far higher standard, since the potential loss of life from an accident is very high. To avoid the issue of on track hazards, all of the tracks are elevated, making cost and maintenance far higher. Lastly, there are still people constantly monitering the network from the control room, keeping an eye on the trains and dealing with any emergencies. It works on the small scale, but not without costs. O'Hare installed the trains as much for how \"futuristic\" they made the airport feel as for their efficiency and usefulness. Asking my dad this very question, he says \"The manpower needed to deal with a network like ours on a large scale would be a nightmare. Cheaper to stick with normal trains.\"",
"Looks like a majority of people are focusing on long-haul trains, but I'd reckon that most car use is short distances of within a city, or commutes, both of which would fall under public transit (consider how expansive the London tube network is which allows for commuting into the city). So the real question is why don't people take local transit of the rail variety (LRT, subway), and why aren't those automated. Well some are automated, ex: Copenhagen's subway / LRT. But as others pointed out it may not be necessary, subways can carry a lot of people and require few staff -- it may become necessary/profitable at some tipping point though which we may have hit as indicated by some of them being automated now. As for why people don't take transit I'd argue it's how our cities are set up and our culture. In North America the public infrastructure just wasn't developed as thoroughly and cities spread out more. With a lot of lobbying to develop road networks instead of rail networks (leading to things like the GM streetcar conspiracy), it became a lot more profitable to sell cars and gas than affordable public transit that would be hard to reach everyone in a sprawling city anyhow. So a lot of it was by design, and now has become engrained in culture. In cities where public transit is very effective though it leads to a different culture where taking a car is almost seen as absurd in a lot of cases.",
"Nothing and a lot is preventing the trains from being 100% automated. In Denmark, the subway trains are without any personnel. I don't know the status of other countries. The subway system was built like that form the beginning. That means both the trains, and the surroundings are designed to make it as easy as possible. If you want to have a computer controlled train, you would need to invest a lot of money, so it makes the most sense to wait until the train needs to be replaced anyways. Also, to determine location, and use that to determine what action to take, there is a lot of different ways you can do it. One is GPS/glonass/Doris/compass. But this has several drawbacks. You can loose coverage, and the accuracy isn't good enough. So the trains will have to combine it with other techs. That is usually radar. But radar is mostly good at spotting objects. It can see another train, but it can't read a sign. For that you would need a camera (unless you find another way of delivering this information to the train, such as digital/electric signal). In case you use a camera, then it isn't easy to detect a sign, that stands with a noisy background, in dark, while driving 100 miles per hour. It isn't impossible, especially with today's tech. But you don't have to go back many Years, before it's unfeasible. Now instead imagine surroundings designed for autonomous trains. A subway tube, with completely white walls, and then a red sign. Much easier to detect, and decipher. The point being, that it isn't just the design of the train that has to be made, but also the route that has to be updated. But most likely, it's only a matter of time.",
"One thing I'll add to the masses of good answers is that rules need to be broken. (p.s. I ended up writing way more than I expected, sorry... Also, quick edit: Source - Rail employee for over 10 years but who is leaving so has no reason to defend jobs beyond what I think is legitimate.) Where ever automation exists there is still someone there to do things the computer isn't allowed to do. Automated systems are written with rules to keep people alive, which is good, but the real world involves things that interrupt the operation and application of those rules. Rules arrive because we do something and realise \"Oh, that's dangerous. Let's not do that again.\" As time passes we do more and more things and learn what is and isn't safe and we write rules to factor in all the circumstances we encounter. Eventually, however, we come across situations that haven't been accounted for. A rough example might be; A lightning strike fries all the signalling equipment for a region (so signals, no control of points/switches, etc.) meaning there is no information going in or out of the system governing those tracks. The train may be written to simply proceed using cameras so it knows not to run into anything but trains can't steer and the steering wheel (signal box) has been turned off. With humans in the system we can do things with zero technology. A human can physically change things, can understand input from non rail systems (people and computers), and can think creatively. Obviously things can be, and are, heavily automated but total automation, with zero human input, is nowhere near being available. There are driverless systems in use but they are only small, isolated systems. Imagine a major city network that has various sets of electric passenger trains (to move millions you need a lot of trains so some are new, some will still be from the 80's or 90's), diesel long distance passenger trains, diesel freight, and heritage steam, some or all of which may be operated by different companies/organisations with variable levels of financial capabilities. The longer distance trains may also leave a city, state, country, with automated systems and enter an area with 19th century technology. Finally, in a 99% automated system with only caretaker employees there for the just in case moments you don't want to lose skills and knowledge. A guy on a train whose only job is to help people in an emergency, move objects from the track, or change the tracks will probably be a low skill (and low paying) job with little incentive to actually gain or maintain knowledge and will likely be more of a problem than a help in a crisis. In the first generation of automation the staff will still know how everything works if manual input is needed because they used to do it manually, in a few generations the staff won't know how to bypass the technology and get things working. All in all, automation is entirely possible but will require huge investment (large rail networks are worth 100's of billions in infrastructure and stock), will take an extremely long time to fully implement (new and retrofit), cooperation and consistency between governments, corporations, etc (hell, apple and android still don't play nice), and may not ultimately be 100% automated in a way that still effectively operates. (Also means that one computer may be capable of shutting down an entire network.. bit of a terrorism target). All of this is before you hit unions with power. Train drivers going on strike can very quickly cripple their region (many rail unions are combined with buses so alternate transport may be a real issue) Meanwhile; cars and trucks are smaller, independent, things with a slow and steady real world trial with willing guinea pigs who don't rely on it for their livelihood. Not many personal trains or small, single unit rail companies out there, whereas private car owners and truck companies that can implement alongside their manual trucks are much more willing (taxi drivers aren't exactly rushing out there for automated cars but their companies are). A simple practicality for cars is that they can steer around a problem and a single failed vehicle won't shut down entire roads. A train can't swerve and, unless the infrastructure is there to move trains around a blockage, a single failed train can block and entire line (or more).",
"Fully automated trains have existed for a long time. See [ATO]( URL_0 )",
"You need a railroad for trains and railroads have certain requirements where they can be built (roads are much more flexible in that regard)",
"Executive Management is a no-brainer for automation. Just ask it a question and have it blurt out nonsensical buzz words and send out a memo changing company policy and procedures based on zero data.",
"One big debate on automation of cars, busses, lorries etc is on \"who is responsible\" and at the moment will fall back onto having a person ready to take over \"just in case\". Out of all modes of transportation, trains will have one of the lowest to gain, the cost of a driver against the cost of the rest of the system is minor in comparison. It may be worth also mentioning that train drivers are very heavy united unionised, but I am sure that has nothing to do with it.",
"I currently work for a class 2 freight company. While your standard road job could be automated pretty easily local work like dropping cars off at customers and switching could be a little further off. Most of the customers I deal with have such a half baked rail into their facility I can't see them spending the money to upgrade and get sensors and whatever else they may need to spot cars. I'm sure in the coming years we'll see it but the railroad has such strong unions it will be a bit longer then you may think.",
"Most new passenger train systems are. In some cases, union rules require drivers, whose entire job may be as trivial as initiating braking (but the auto system will do it anyway, if they don't) and controlling doors at stations (which can also be automated, with feedback to prevent accidents obv). This costs more, but not as much as some (/r/Tuiq) have suggested. [MTA alone moves 5.7 million people each workday]( URL_0 ); divide the costs by 1 million and you have the equivalent cost *per car*, assuming roundtrips are counted twice in that number, and assuming most people carpool 2.8/car on average (wildly generous). Freight trains operate with much lower costs/profits, and therefore simply can't justify the automated controls. Yet.",
"In north america, the huge majority of trains are freight. There is also a huge hugs amount of tracks in the middle of nowhere. If a automated engine had a simple mechanical breakdown having the engineer onsite is critical. Often you'll see no less than two engines on a train, this isn't (always) because it needs the power, most of the time it's there so that the train can continue even if there's a complete engine failure on one of the engines. Even with a backup engine a simple tree across tracks, or break lockup, can be handled by a engineer, while a automated system could not handle that. Finally, if the railroad companies have reisgned to the fact that they still need engineers in the trains anyway, why bother automating them any more than they already are.",
"How would automation even work for a local freight? Much of the US for example is in dark territory - no signals, maybe some electronic interlocks at yards or junctions. Trains receive track warrants between landmarks and such rather than to the next signal. Local freight jobs usually involve throwing switches, spotting cars, and doing numerous brake checks. Currently, non-unit train operations are quite costly and sometimes do not even break even as far as operating expense goes. Coal revenue no longer offsets smaller scale services any more, Installing a manual switch for a small local industrial customer already runs $70-90k. An electrically operated one with all the required equipment would likely run triple that cost. What company is going to pay so much upfront when they can just use trucks instead? The point being that so long as there are local freight switching operations, there will be a conductor on the ground and the process will never be automated. Perhaps that conductor could remotely control the train (a system already in place at larger industries and yards) but you will never have human free freight operations.",
"From the comments I've skimmed, most go into extensive detail about the futility of the marginal gains that would be achieved through the automation of train travel. I think this fails to address the very heart of your question - why cars. This believe directly answers the question why trains have not been 100% automated. For arguments sake, imagine if the same level of investment for cars (and the genesis of automated cars) had been placed in trains. I think it would be sensible to assume that train travel would look very different to now. More advanced, certainly. But the way in which populations grew and spread out, as well as the desire of independent movement the car became the obvious better choice. But imagine some parallel universe. Here, humanity stuck with train travel and used cars as alternate, dangerous and labour intensive transport. Train travel would eventually evolve to the state of sublime automation, meeting the exacting needs of the present day. We are excellent at catering to our own needs after all, sometimes at great expense. This is not too far from our own reality with the car. And who is not to say that in the future, with areas of increasingly dense population automated train travel will become a necessity. Automated cars will have greater teething problems than a fully automated train. Currently, there is too great a commercial benefit to be had with cars because it has been the majority's weapon of choice. So if you believe that automated train travel would lead to your preferred world vote with your feet and ride those rails, good sir. Edit: TLDR People prefer cars over trains, so we are supplying the demand.",
"When and where to automate depends a lot of local conditions. In the EU or Japan, there's a lot more centrality to things, so automating railways to at least *some* extent is beneficial. For trains in particular, though, you want to avoid full automation in any people-involving industry simply because computer programs are only as reliable as their programmers, and programmers are not globally renown for the reliability of their code, if you catch my drift. Computer's run trains into each other at least once due to glitches and technical faults. The systems where there is automation are \"mostly automated\" for all practical purposes because of problems like that. A train's not going too many places it shouldn't, so having a conductor handy to work comms and make sure things are (literally) on track is the general extent to which people are involved. But you do want an engineer on both sides to make sure that things are on the *correct* track. Cars are a bit stickier, however. A lot of your automation focus for cars and trucks is coming from the US and other areas where there's a lot of open space and out of the way places. Freight trucks tend to benefit from automation because they have very limited conditions to drive under to begin with, and have tighter schedules, and over here in the US, a lot of our overland freight is done by truck. Having trucks (and train depots!) automated benefits a large number of our industries as a result, so there's a strong push to make that happen. Cars are more or less a testbed that accompanies that same general trend of research, albeit for different reasons. Cars are *supposed* to follow specific rules and guidelines for travel and parking that a fair number of drivers either ignore or blatantly violate. In this sense, automated cars (as a unified roadway system element) would be much safer than random drivers, especially with teens, drunks, and older people on the road as the alternative. Keep in mind that total automation does mean *total,* though. Mixed cases don't necessarily end well for the simple reason that the computer is going to follow its program, however that's been written, and a person's going to do what a person's going to do. Automated cars are safe enough with GPS, but the flagrant disregard for road rules (and tendency toward road rage and tired driving) that living people have means that a car going exactly where it's supposed to at just under the speed limit is actually a road hazard. And we're assuming some effort has been made to improve the accuracy of GPS units. I know some of the ones I've owned have been... questionable. This is all never minding legal liabilities and whatnot."
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"http://www.startribune.com/at-camp-ripley-national-guard-members-train-for-the-worst-cast-scenarios/322904531/",
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7149dq | The difference from DRAM to SRAM | Technology | explainlikeimfive | {
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"Dynamic RAM (DRAM) requires the computer to constantly refresh the data stored in memory. If the power is cut then the memory is cleared. Static RAM (SRAM) will maintain the value without having to constantly refresh it. However, it will still lose its value if it loses power. SRAM tends to be faster but more expensive than DRAM.",
"A memory cell in SRAM uses multiple transistors (4-6) which allow very fast state switching and the memory state requires a constant current to maintain. A DRAM memory cell is pretty much transistor and a capacitor. This uses much less room per cell. And there are ways to refresh the memory with an occasional pulse before the capacitor discharges."
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715hmf | why do subwoofers require more power to drive than higher frequency speakers, when high frequencies are more powerful? | Technology | explainlikeimfive | {
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"Why, exactly, do you believe higher frequencies are more powerful? Subwoofer are bigger. Bigger speakers push more air. Pushing more air takes more power.",
"You are correct in that higher frequencies have more energy. Energy is determined by both frequency and amplitude. Because volume is determined by the energy, to achieve the same volume at a lower frequency, we must increase the amplitude of the sound wave. This is also why subwoofers will have much more movement than your typical tweeters and other speakers that operate at a higher frequency (but lower amplitude). So basically to make the longer (lower pitch) sound waves carry the same amount of energy (volume) as the shorter (higher pitch) sound waves we have to make them bidder in amplitude (the height of the wave, not length)"
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715r4t | Why do airplanes turn by using a banking turn instead of using the rudder? | Planes seem to bank to turn much more frequently than they use the rudder to turn. Is this due to the larger control surfaces that seem to be involved in a banking turn, some wierd aerodynamic effect or is it related to structural integrity? | Technology | explainlikeimfive | {
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"If you tilt the plane, it tilts the direction of upward force from the wings' lift towards the middle of the turn. This means that the force of changing the plane's velocity is applied to the wings instead of the relatively weak rudder. Also, it means that the centrifugal force that would throw passengers and cargo towards the outside of the turn is balanced by the tilt of the floor.",
"They can use the rudder to turn as well as banking, but by banking they keep the inertial forces of the change in direction pushing passengers down into their seats rather than pulling them to the side. Much of the time it is just more comfortable.",
"It's important to note that for planes more so than for other vehicles the direction you're moving is not necessarily equal to the direction where your front end is pointing. The rudder would turn the plane itself, i.e. change its orientation, but won't directly do much about the direction it's traveling - initially, especially if you'd do a large and quick rudder turn in a nimble plane, it'd be like skidding slightly sideways, you won't have *actually* changed your course until after some time the engines (which are now pointing where you turned) and aerodynamics start moving your plane towards the new direction. Banking, on the other hand, immediately and continuously applies a part of the wings' lift to push the plane sideways, to overcome the inertia and make it move in the new direction. For large passenger planes the difference may not be so obvious, but for nimble and fast aerobatic planes, there are a bunch of maneuvers where the orientation of the plane (and thus the thrust of engines) is quite different than the direction of flight."
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715xkx | Why is Linux commonly used by hackers/for hacking? | I've often heard that linux is very popular among hackers, why is that? Thanks. | Technology | explainlikeimfive | {
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"Linux and any other Unix based OS is what's commonly referred to as Open-Source, meaning that the user has direct access to the system's kernel, and can make modifications that they deem fit, unlike an OS that's proprietary, like OSX or Windows. In reality, you'll find that Linux is often used not just by hackers, but by IT workers, programmers, and lots of other professions that would deal with the other side of the tech we use every day. Source: Linux hell yeah",
"It's open source, meaning: * It's free * You can modify it as you wish * You have access to all functionalities Besides that the command line interface in UNIX allows you to quickly access low-level networking commands and use scripts to run them. All of these make it great for any network engineer or IT guy, not necessarily hackers."
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716cfs | Why is 32 bit sometimes referred to as x86? | Technology | explainlikeimfive | {
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"The first mainstream 32-bit processor Intel made was the 80386 (often just called 386) and it was an architecture improvement over the 16-bit 80286. A few years later they do another upgrade to 486 and then to 586, a.k.a. Pentium, which dominated the 1990s, then the 686 Pentium Pro. These chips were mostly backward-compatible, so software written for an earlier version would usually work on later ones. Come the late 1990s, there were grumblings about various reasons to upgrade to 64-bit chips, but this sort of upgrade tends to break backward-compatibility, so there was a lot of feet-dragging. Intel decided that the right thing to do was to just suck it up and use the switch to not need to support 1980s-era software forever; they developed their Itanium line of 64-bit processors. Intel's main rival at the time (and in some ways continuing), AMD, had been licensing Intel architecture to make competing chips, but they developed an architecture called AMD64 with a 64-bit mode *and* could still run software built for the older 386, 486, 586, and 686 (collectively called x86) processors. This fight went on for a while, but AMD64 ended up winning and Intel finally licensed it. For various boring and silly reasons, people tend to drop the AMD portion and call this x64.",
"32-bit doesn't need to be an x86 system (for example, older Apple machines are often 32-bit, but are not x86), but because x86 was so successful it's difficult to find a 32-bit processor that wasn't. Likewise, x86 processors weren't only in 32-bit, but the term \"x86\" was most common when referring to them so it simply stuck. x86, crucially, refers to a *family* of processors that share one important detail: backwards compatibility in the instruction set. The first x86, the Intel 8086 (1978), was a 16-bit system designed to take over for the 8-bit Intel 8008 and 8080 chips. Intel started iterating their naming scheme in the middle, so the next one was the 80*1*86, then the 80*2*86 (often just called the 186 and 286). With the 80*3*86 (a.k.a 386), the processor was increased to 32-bit. When that happened, the backwards compatibility meant that 16-bit programs written for 8086, 186, and 286 systems still worked, but just didn't take advantage of the full capability of the chip. Importantly, the 386 was also one of the first widely popular home computer systems, and that is part of the reason \"x86\" is associated with 32-bit. Further along, the 80*4*86 (486) came out, and was also 32-bit. Then something different happened - Intel wanted a name they could trademark, so the next iteration they released, the 80*5*86 (586) was named the *Pentium* (since the prefix *penta-* means 5). That was far from the last 32-bit processor, but the rise of the term Pentium meant that while geeks knew it was an \"x86\" system, the public would simply think about the x86 ones as the ones they knew, namely the 386 and 486. Now that they had a trademark capable name, they simply iterated on it, with the Pentium 2, then 3, then 4, and more. It wasn't until 2003 that AMD released a 64-bit processor for the masses that maintained the backwards compatibility, and Intel didn't do so until 2005 (which was still named as one of the Pentium series) [Note: Technically its Itanium processors, released in 2001, were 64-bit, but they broke the backwards-compatibility and sold poorly]. What that means is that the modern era of ubiquitous computing crosses the divide between 32-bit and 64-bit both being widely available and familiar to most. And when 64-bit processors came out, the manufacturers didn't just want to say they could run 32-bit programs too, they wanted to let you know in particular that they had explicit *backwards compatibility* with the entire x86 *family* of processor instructions, and any program written for those instructions. Because of that marketing, \"x86\" became more common to hear than \"32-bit.\" And since people had basically forgotten the 16-bit era as being distinct from the programs they saw crop up after the 386 came out, they naturally started to read \"x86\" as *meaning* \"32-bit\" in particular. Of course, the irony is that, because the 64-bit processors are almost universally backwards-compatible with x86, that makes them also part of the x86 family.",
"X86 is the instruction set that 32bit processors use for the most part while x64 is what 64 bit processors use for the most part. Instruction sets being the operations that a processor is capable of and x64 and 86 are standardized instruction sets."
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716m7n | My phone used to be reasonably fast on 4G, but now that LTE is the standard, whenever my phone has to switch back to 4G because LTE isn’t available, it is insanely slow. Why did my phone used to be so much better on 4G than it is now? | Technology | explainlikeimfive | {
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"Carriers have limited amounts of RF radio frequency available to use. Any given bit of spectrum can be used for 2G, \"4G\" (which is usually just 3G HSPA+), or 4G LTE, but it can't be used for multiple technologies at the same time. New spectrum is very hard and expensive to come by. Each generation is more efficient, being able to do more with any given amount of spectrum. Since more and more people are on LTE, fewer on \"4G,\" and those people are doing more and more bandwidth-intensive activities. As a result, wireless companies are \"re-farming\" spectrum in a lot of their markets, taking it away from \"4G\" and putting it towards LTE. (2G will largely be left alone for a few more years, as a lot of legacy business devices still use it, whereas 3G/\"4G\" is mostly just older phones that are being replaced by the natural phone lifecycle)",
"I'm confused here - isn't LTE just a type of 4G?",
"The people that put stuff out for you to download used to compress it much more, because everybody had 4G. Now that everybody has LTE, things are bigger and not compressed as much. They look better with LTE speeds, and worse without them."
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716uyf | How does the repairing of corrupted files work? Is it actually reliable? | For example, WinRAR's archive repair tool - how does it work and how reliable is it in giving you back the uncorrupted archive? | Technology | explainlikeimfive | {
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"There are several techniques, but the general idea is to store some extra, redundant, data. Some techniques can repair missing or damaged data, others can simply detect it. however, you asked about repairing. Let us look at a simple example, with two bytes of data: A: 10010110 B: 11001100 To help with repairing data, we compute the XOR (exclusive OR) of the bytes. If both bits are the same, we produce a zero. If exactly one bit is one, we produce a one: A: 10010110 B: 11001100 ----------- C: 01011010 We then inject that extra XOR byte into the data stream, inflating its size by 50%. Every third byte is a \"parity\" byte that does not directly store data, it is derived from the previous two bytes. Now, when reading the stream of byte, let us assume that one of the bytes is unreadable. Perhaps there is physical damage to the disk. Perhaps the memory buffer is corrupt. Perhaps data was garbled when transmitted over a network. Regardless of the reason, one of the byte is unreadable. If the parity byte is bad, we simply discard it. However, if either of the two data bytes are bad, we can derive them from the other data byte and the parity byte using a property of exclusive-OR: if `A^B=C`, then `A=B^C` and `B=A^C`. A: 10010110 C: 01011010 ----------- B: 11001100 B: 11001100 C: 01011010 ----------- A: 10010110 As you can see, we easily recreated bytes A and B from the other two. If too many bytes are missing, we will be unable to reproduce the missing data. If data is unreadable, but some other data used to recreate it is present but incorrect, then the recreated data will also be incorrect. It may be desirable to combine data parity with a checksum such as [CRC]( URL_2 ) to detect the case where data is present but incorrect. Note: \"parity\" is often used to refer to a [parity bit]( URL_1 ) which is a mod-2 count of one bits in a byte, but can be extended to more bits in this way similar to what [RAID with parity]( URL_0 ) does."
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7176c6 | How do user-visible encryption codes work? | When I go to the WhatsApp encryption code screen of a conversation, it shows me a QR code and a string of numbers basically saying that if they're the same on both phones, then the chat is secure. Telegram does this with emoji in calls saying that if the same 4 emoji appear, then the call is secure. How is this supposed to assure me that the messages/calls are secure? I know there is encryption behind the scenes, but what do these codes and emoji have to do with it? | Technology | explainlikeimfive | {
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"There is a type of encryption where two parties are able to communicate securely over an unsecure line. What's happening is that both phones will come up with a large and random number, so large and random that its virtually impossible for somebody to accidentally guess anybody else's number in any lifetime, never mind accidentally or intentionally guess *your* number. Then they use some math to turn that number into two numbers or keys, one is a private key and the other a public key. The private key is secret and never leaves the phone, but the public key can be given to anybody, in this case your friend on the other phone. Now, when the two phones communicate with each other initially, there is no encryption yet. In order to communicate with encryption, both sides will need a copy of the same encryption key, but since the internet is not encrypted, they can't come up with a shared key without hackers being able to also get it. This is where the public and private keys come in. Both your phone and your friend's will give each other their public keys. At this point, it doesn't if a hacker can see it because the hacker can't do anything useful with only the public keys. Next, your phone will take your friend's public key and use some math to combine it with your private key to produced a new key. Your friend will do the same with your public key and their private key. With this type of math, you both will produce the exact same new key, even though your inputs were different. This new key becomes the shared key for the encryption. Since the hacker doesn't know either of your private keys, they cannot reproduce your shared keys. WhatsApp and Telegram are simply converting your shared keys into a form that is much easier for humans to also verify. If the numbers shown by WhatsApp are different on each of your phones, then its means that some hacker is pretending to be your friend's phone and is ease dropping on your conversation, or you aren't talking to your friend at all, but a hacker pretending to be your friend. Usually this may happen by the hacker intercepting your public keys in the beginning and then forwarding their own public key. Since they cannot guess what either your private key is or what your initial random number was, they give you their own public key and claim that it came from your friend. Now, everytime you send a message to your friend, you are really talking to the hacker who then forwards the message (or changes it) to your friend. However, if you and your friend compare each other's numbers from WhatsApp, you'll notice they don't match and know that a hacker is involved."
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717i0f | How are big open ended games like Skyrim tested to ensure they are (mostly) bug free? | Technology | explainlikeimfive | {
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"If you've played Skyrim, you know the asnwer to this is \"Not very well\". It's basically the same as any other game (or piece of software), though. You have as many people play as much of it as possible and try to create as many expected and unexpected conditions as possible. With open games the magnitude of Skyrim, though, you're never going to get them all.",
"Most of the time there are actually test scripts written to test out specific parts of the game. These are called test units. A developer writes a test unit for a specific action like: pull out weapon, attack once light, attack once heavy, block, put weapon away. While the script is running, either by \"pushing\" buttons on the keyboard or just calling commands directly in the engine, it is also watching the error handler for that specific system. It then logs all of the errors that are caught and generates a report for the developer. With test units a single developer can test the vast majority of the game engine. Usually where these test units fail are in rare or unusual situations and that's where you find bugs in retail releases. Ever wonder why you usually have to do some goofy combo like drink 200 potions, then jump backwards into a lake while removing your armor in the air to get a specific exploit to work? Well it's because the test unit wasn't told to check for that specific scenario to make sure everything works right and what developer in their right mind is going to do that \"just because\". In most cases in addition to test units developers also have actual people play their games. This approach is useful because people are REALLY terrible at following instructions and usually screw up everything at least a few times before getting it right so developers need to test for when things are done incorrectly and make sure it doesn't break the game. Now video games are an interesting type of software because they are incredibly complex (especially open world games) compared to most programs. The more interactive a game is the more code is required to make those interactions work. The more interactive a game is the more fringe scenarios that are possible, like the one stated above. As such, large and complex games also usually feature the most bugs released. So usually they can account for the vast majority of intended functionality between play testers and test units but of course as you're probably aware there are always scenarios that slip through. edits for clarity/readability*",
"An army of playtesters. Of course they can't catch everything in a game of that scale, and Bethesda games especially are not known for their bug-free releases. All of their games have a pretty strong history of jank and bugginess, from minor stuff to real show stoppers. The most common ones get hammered out in patches after release, but even years later there's still a lot of known issues with Skyrim and Obsidian's Fallout: New Vegas needed a battery of patches to even reach \"playable\" status. It's part of the territory when you make a game with so many moving parts."
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717z8m | Why do defibrillators need to be rubbed together right before use? | Technology | explainlikeimfive | {
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"There is a conducting gel that they apply to the paddles. Rubbing the paddles spreads the gel evenly."
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718g4c | How do Enchroma glasses work to allow the wearer to see colors again? | I keep seeing these beautiful videos on the Internet of families buying these glasses for their loved ones, and am just really curious about how they work. | Technology | explainlikeimfive | {
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"Most colorblindness is red/green meaning the two colors kinda blend together. What these glasses do is essentially act like a filter which removes the part of the two colors that \"overlap\", and only allow the wavelengths farthest apart from each other to show, separating the two colors. URL_0",
"They basically filter out parts of the electromagnetic spectrum that cause confusion for people who have a color vision deficiency (i.e. people who are 'color blind'). People who are color blind often have malfunctioning cone receptors that respond inappropriately to certain frequencies of light. This may cause certain colors (like red and green) to blend together and become indistinguishable from one another. It may also make it difficult to see certain colors, like certain shades of orange, pink, and purple. After filtering out the confusing parts of the spectrum, colors typically appear more vibrant (both for people with normal vision and color blindness) and only frequencies of light which are more easily distinguished by people with color deficiencies remain. So whereas, for example, a red object may have appeared simultaneously red+green (like a brown color) to someone with a color vision deficiency, with the glasses it is more easily identified as a red object and much more easily distinguished from objects that are green in color."
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71adbu | If a website asks you to provide an email address and password, what is to stop them from using that password to attempt to get into your email? | Is this one of the reasons why it's suggested to have multiple passwords? Theoretically, if the password is stored in an encrypted state, is that enough for them to claim they could not even attempt it? | Technology | explainlikeimfive | {
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"> Is this one of the reasons why it's suggested to have multiple passwords? Yes it is. This is one main reasons why should use a different password for every website. The other is that it doesn't even require the website to be malicious, it could just be insecure, storing your password in plaintext. > Theoretically, if the password is stored in an encrypted state, is that enough for them to claim they could not even attempt it? If the password isn't stored in plaintext, but instead salted and hashed (not encrypted) then no one can get the original password from the database (unless they brute force it). But it doesn't mean that a malicious website won't store your password in plaintext anyway... Also, [relevant XKCD]( URL_0 ).",
"Stopping them? Nothing, besides human decency and the fear of someone finding out and reporting them. > Is this one of the reasons why it's suggested to have multiple passwords? This is not he reason why not reusing passwords is important, but it also protects against this. > Theoretically, if the password is stored in an encrypted state, is that enough for them to claim they could not even attempt it? They could always safe your real password and use it for nefarious purposes. From the outside, you'd have no idea.",
"There's no technical reason they couldn't do that. There are business and legal reasons why they wouldn't want to but that's a different scenario. Any reputable website should be storing your password encrypted but you first have to send them the unencrypted password so they can encrypt it for you. This is one of the reasons that it is recommended to use a unique password for every site you go to.",
"Nothing which is why everyone tells you not to use the same email and password combination for every website and under no circumstances use them actual password for your email as the password you use with it.",
"I want to make this very clear: This concern is not just theoretical. It is **very real**, it happens every day. It's a type of phishing. That spam-ish looking cat picture wallpaper site riddled with typos that your aunt found on Facebook and wants help making a log-in for? That's the reason that site exists. A hacker in Eastern Europe made it in order to collect emails and passwords, so they can use your aunt's email address to send spam emails.",
"This is indeed one of the reasons why it is recommended to have multiple passwords. With modern tools like lastpass and keepass it is easy to have hundreds of passwords. Most security experts who have studies passwords are even recommending writing down the passwords in a notebook over reusing your password, although this will not help much against friends and family it will help a lot against large scale automated attacks. It is also recommended that you turn on two factor authentication (2FA) wherever possible. This will stop anyone who have managed to get a hold of your password from using it."
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71be3t | How is Google able to provide better search results for a site than that site's own search feature? | Google has to index the entire web, while a site's search engine only has to index it's own material. Why haven't web developers been able to create a standard search tool that works at least as well within their own site as Google? | Technology | explainlikeimfive | {
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"The problem isn't how much data there is to index. The problem is creating an algorithm that shows you the most relevant data for your search terms. Google has thousands of engineers who have been working on their search algorithm for about 20 years now. They are really good at it and they keep their specific methods secret. There's just no way that your company's IT guy is going to be able to develop a search algorithm that's anywhere nearly as good as Google's. Fun fact, Google lets you integrate their search engine into your own site for searching your own data."
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71bzlu | How do Bionic limbs function? | In regards to the recent Nicole Kelly GIFs, I'm curious what how she's actually making this arm work. | Technology | explainlikeimfive | {
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"The go to way is to take a bunch of sensor units, attach them to whatever muscles are left in the stump, and convert their muscle movements into electric signals. These signals are then used for rather rudimentary commands. Hand prostheses for example are either \"pull to open\" or \"pull to close\". If you don't pull, the prosthesis goes back into its default. Imagine that your hand was always closed, but would open when you flex your biceps. Something like this. Now, ever amputation is different. Not only does the prosthesis have to be fitted neatly on the stump of the patient, it also has to be done in a way that it stays in place, but without putting to much wear in the stump. That's one reason for why they are tailor made. Also, in each amputation different muscles in different places will be retained. You need to check where a clever place is to actually put those sensors mentioned above."
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71d9r2 | how do stab/cut proof shirts work? | A buddy of mine works with glass and they recently gave out stab proof shirts, we tested it out and you can not cut through, even with a sharp knife the material couldn't be stabbed through. It feels like normal fabric how does this work? | Technology | explainlikeimfive | {
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"The threads are made out of Kevlar in many protective fabrics. They are knitted into a loop-locking fabric so that there aren't slots for the knife to get through. It's not a cool as chain mail, but much lighter.",
"What brand are those shirts? I would like one!"
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71e2v2 | Can a solar-powered drone stay flying 24/7? | Technology | explainlikeimfive | {
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"In principal yes. the record flight time I could find was 336 hours or 14 days by [Qinetiq Zephyr] ( URL_0 ) But you have limitations like 22.5 m wingspan and a total weight of 53 kg where 2.5kg is the payload. And fly high as it has a Service ceiling of 70,000 ft (21,000 m). Both gliding and battey power is used to stay up at night. Eh altitude is alos neede to say out of loudes. It look that there are som project to use the for surveillance or internet access.",
"In theory, yes. In current practice, no. You'd have to find a way for power output from the drone to be less than the power input from the solar panels. The current rate at which Drones burn energy makes solar power unfeasible. Especially when we consider the added weight of said solar panels. Added weight means more energy required for lift off and sustained flight. We simply don't have the solar tech for it. So two reasons, solar tech is too heavy and it also isn't efficient enough on a small scale to provide that much energy."
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71evgy | How do websites know when I’m on a mobile and when on desktop? | Technology | explainlikeimfive | {
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"Part of the request your browser sends to the webserver is an \"agent string\" which identifies what browser, version, what OS, what version of that and some other details. From those tidbits its fairly easy to determine if you're mobile. For example, my browser here at work [reports via this site]( URL_0 ): > Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 From my phone I get: > Mozilla/5.0 (Linux;Android 6.0.1, < model of my phone > Build/ < build info > etc. etc.",
"Your web browser identifies itself to the website when it makes the request, this is called the \"user agent\" string. You can see for yourself what your user agent string is now, and how much information it reveals: URL_0 Some websites use additional clues, too: * The screen size and resolution * Whether there's touch support * etc. None of these things are 100% reliable but taken together they're all pretty good heuristics."
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71ewrc | Talking to a sales representative he implied knowing my browsing habits, based solely on me visiting his website (or perhaps through my email address). How can I know what advertisers know about me? | PS: I'm a very light Facebook user (no friends, have the account just for the ocasional communication with some companies) | Technology | explainlikeimfive | {
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"When you visit a website, it can store a little file in your pc with some data on it, these are called \"cookies\". Since the introduction of \"LocalStorage\" it was the only way to keep info on the client (you) side. Allowing the \"keep me logged in\" feature to work in any site. But since the ad and user info bussines became a thing, they can be used to track you almost everywhere on internet. That \"share on facebook\" button on a recipe blog? Reads the facebook cookie, identifies you and sends the info to facebook. That adsense banner on a news site? Reads the google cookie, identifies you and sends the info to google. All of this without you being aware and with your consent. What? You didn't consent it? Remember those Terms and Conditions you never read when you created your Facebook or Gmail? Yep. And then they sell that info to whoever wants to buy it."
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71feji | How do lock companies make so many different locks? | I feel like it would be extremely difficult to get a machine to make entirely unique things. | Technology | explainlikeimfive | {
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"Say a lock company makes locks with both 5 and 6 tumblers each, and 2 different key shapes/cross sections, then they'll have a total of 108,864 possible unique locks. If they run out, they can design another cross section which would give them another 54,432 options, or make a lock with 7 tumblers which would give them another 279,936 options. Multiply that by many different lock makers each with their own tumbler sizes and key shapes and you have a very small chance of coming across two identical locks.",
"They don't. The make a decent (but not huge) number of unique locks and figure nobody will go around checking their house keys in every door with the same doorknob brand. If you lined up 100 locks from the same manufacturer as yours, your key would probably open one or two of them. There are enough manufacturers and key types that the existence of duplicate locks is very rarely a problem."
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71gnlb | there was a video I saw that showed a robot using sweeping sonar to navigate, it moved in a zig zag motion. How does that zig zag movement help it compares to it moving in a straight line? | This was the video URL_0 Also I'm not sure how to say this exactly, but what is the robot able to "see"? It's using a ultrasonic sensor, so is it just calculating the different distances that it picks up and its code is telling it not to let the distance get under a certain amount so it moves away to correct it? | Technology | explainlikeimfive | {
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"I'll try my best to explain it to you. For example, you are trying to cross a small road without a pedestrian lane. If you see a car approaching you, you might move in a more diagonal direction rather than in a straight line, in order to avoid the car. You'd also want to watch both sides of the road in order so that you could choose whether you'd like to run in circles or not. Similarly, this device zigzags in order to watch two directions that it could possibly go to; like watching both sides of the road. You are right. It really measures the distance of the echoes that it gets, and if it gets too close (by it's standards), it goes another way. (I made one just like this using EV3 years ago btw)."
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71i8b4 | What's the difference between OTF and TTF fonts? | Technology | explainlikeimfive | {
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"Hi. I make fonts for a living. TrueType and OpenType fonts are mostly the same thing. There are two things that make them different: TrueType fonts are drawn using Quadratic Outlines, which is a very formal way of drawing letters. OpenType fonts use Postscript Outlines which is a much easier way for designers to draw fonts. You can't see the difference when looking at a font, but it's something a type designer has to think about when drawing the letters. The other difference is how each font uses \"hinting\". Hinting is special rules that tell the computer how to show the font on a computer screen. TrueType has lots of rules about how it should look, and because of this, a hinted font will usually look better on a computer screen. PostScript has some simple rules and mostly lets the computer decide how it should look. TrueType fonts can have a .ttf or .otf extension, and OpenType fonts can only have a .otf extension. Most people can't see these little differences, so you can use either OpenType or TrueType fonts. When you're working in a job that uses a lot of fonts you might need to use one format or the other. Graphic designers who work in print usually use OpenType fonts. Web designers usually use fonts that start out as TrueType fonts. And a lot of architects need to use TrueType fonts in their programs. Last thing, kids: fonts take a lot of work to make and a lot of people work very hard to drawn new and interesting fonts. So please use your allowance to buy fonts and don't steal. Adults: - assuming OTF is CFF-OTF/Type 1 outlines, even though OTF is a wrapper around CFF or TTF outlines. - manual hinting is better than no hinting or autohinting.",
"OTF also supports ligatures (e.g. fi and fl as a single character) and choice of uppercase and lowercase numbers, among the things that were already mentioned.",
"TTF stands for **True Type Font** , a relatively older font, while OTF stands for Open Type Font **Open Type Font**, which was based in part on the TrueType standard. Both are file extensions (.ttf,.otf) that are used to indicate that the file is a font, which can be used in formatting the documents for printing. They are distinguished primarily by their different outline formats and the contrasting approaches employed to rasterize those outlines.",
"OpenType (OTF) allows for more advanced use of text/glyphs/symbols than TrueType (TTF). It was developed in a way that allows font develops better, cleaner looks when using more \"complicated\" text use than simple alphanumerics. This includes any use of multiple languages, symbols, mathematical symbols with better support for Unicode. OTF better handles any changes in the positioning, size, and layout of the characters. Simply put OTF is better for advanced typology or use of special characters. They are largely equivalent in their coding of how they represent characters and for standard usage of alphanumeric characters. If you have a choice between OTF and TTF, because of its broader application OTF is preferred.",
"Just to build on what others have said: - OpenType fonts can be used across operating systems (Mac, Windows, Linux, etc.) - OpenType features allow for some very nifty substitution logic, I've used it to give the \"worn type\" look by randomly switching out up to seven versions of the same character. - OpenType fonts can come in CFF / Type 1 or TrueType flavors. The nature of the curves differs slightly, but more importantly, the former will have the .OTF extension, while the latter will have .TTF - it's still an OpenType font, though! The TrueType flavor seems to be a bit more compatible across systems, so as a type designer, I've switched to using the TTF flavor.",
"You may ask why there were two types of fonts in the first place and the reason goes back to the early days of printers, when there were multiple different page description languages to tell printers how to print a page. Adobe's PostScript became a favourite (especially for publishing) and with it PostScript fonts. Apple and Microsoft didn't like having to pay royalties to Adobe to use PostScript fonts, so they got together to invent a new font format, TrueType. This led to the \"font wars\". (Truly, that's what that period was called.) Professional typesetters and service bureaux generally regarded TrueType fonts as inferior, and that was often the case. (Not because of the format but because there were lots of badly made copies of famous fonts in TrueType. Anyone remember those \"1,000 fonts for $10\" CDs? They were TrueType.) Anyway, eventually Microsoft, Adobe, and Apple all got together and came up with OpenType, which was basically a wrapper that could go around both TrueType and PostScript fonts. Windows started offering in-built support for OpenType, whereas previously you had to install an Adobe app (Adobe Type Manager) if you wanted to use PostScript fonts on a PC. OpenType also allowed far more characters than had been the case for PostScript fonts previously, which had been limited to 256 characters.",
"As a graphic designer on Mac: ttf (TrueType Font) is an older font type. Although it can be used on Mac or PC (cross-platform), it is also often used for fonts that are offered for free. Free fonts can be buggy (unpredictable), incomplete (not all characters included), and potentially so problematic that they can screw things up on your computer. Especially if you use a print shop to produce items, there can be issues (missing letters, strange glitches, etc.) when using TrueType. Be careful using ttf. otf (OpenType Font) is a newer font type. It is also cross platform. It often has more available letters/symbols, including different language letters. It can also include special letters called ligatures (for example, \"fi\" and \"ff\" can look strange beside each other so a ligature is a character that looks better to the eye), and alternates (especially in script or handwritten-style fonts, those are different looks to the same letter) that it will place automatically, or that you can select (from a \"glyphs palette\"). OpenType Fonts are preferred by 9 out of 10 designers (and the odd one only likes ttf because they like stuff that's free and/or have never had a print shop bitch about a file).",
"TTF - you get what you see, if you enter text that is printed in an OTF font the spacing can change. If it's readability that can be good, if you're trying to specify a monogram engraving it can be bad. I tried to get a pen engraved with 'SLY' - someones' initials - the engraving kept returning with 'S LY' and after two or three tries I gave up."
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71k2i3 | How do Dyson air fans work and why do they use a ring-shape structure? How are they better than a normal air fan? | Technology | explainlikeimfive | {
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"that there is still a fan in the base. Being in the base, in a housing, it is a fucted fan ans is more efficient because air isnt lost around the blade tips. From there, the air goes into the ring manifold and escapes through a slit inside the ring. This high velocity air lowers the pressure inside the ring and draws more air from the leading area, increasing air volume. Advantages : more efficient fan, fan case makes it quiet, laminar flow travels farther across the room.",
"Think about a leaf blower: you can’t see the “fan”, but you know one is there from the sound. What Dyson did is to make the opening very small and thin, generating a thin fast sheet of air that can blow far. The fan is still in the base, but it’s quiet because the air velocity is multiplied as it passes through the thin opening, allowing dyson to use a quieter, smaller fan. Think of the manifold and multiplier like a garden hose: water flows out somewhat slowly, but if you make the opening smaller (by putting a finger over it) the water sprays out rapidly, in a small stream."
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71kn9h | How do college campuses have the same WiFi network across entire campuses? | How do all the routers connect to the same network? Also in some places on campus my internet works way better than others, so does each router have its own bandwidth? | Technology | explainlikeimfive | {
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"It's called a [wifi mesh]( URL_0 ). There are multiple ways to set up a wifi mesh. From having one wifi access point connect over wifi to a neighbor, to having all access points connect to a central switch over Ethernet. As for why some on-campus locations appear (or are) to be faster or slower than others, that's something you'd have to ask your campus network staff.",
"Large-scale WiFi deployments tend to work quite differently to simple home or small business networks. There are so many Access Points (APs) that they won't fit on a single Ethernet network, they interfere with each other, and users are constantly being passed from one AP to another, sometimes on different networks, as they move around. Also, you can't just have a single password and tell everyone, so you need to implement enterprise-scale authentication allowing users to connect using their username and password. Without going into too many details, enterprise WiFi typically has a central controller box (or boxes for redundancy). The APs are really dumb radios that send and receive all their packets to and from the central controller to be dealt with. The WiFi packets are sent via a TCP/IP protocol so the APs can all be on different Ethernet segments themselves, even though the WiFi environment they present to the users looks like a single network. The central server device is configured to have access to the corporate authentication service (e.g., via Radius) so it can use the same username/password authentication as other IT services on campus. The problem with bandwidth tends to be on the WiFi side rather than the Ethernet network side. Campuses tend to have hundreds of WiFi users, some with multiple devices. In a small space all these devices will be talking with just a few APs with only a small number of non-overlapping WiFi channels available. At 2.4GHz, for example, there are 11 channels (varies by country) but you have to space by 5 channels to avoid overlap, so using only channels 1, 6, and 11 is common. There are more channels (8?) at 5GHz but still not that many. In common areas they will pack in many APs and turn down their WiFi power to try to limit how much they interfere with each other, but this is really a work-around. Also, devices using old WiFi standards tend to slow down the network for everyone. So there's no point stealing enterprise APs; they're totally useless devices without tons of expensive hardware to make them work, hardware that requires expertise to configure and run.",
"The network is deployed out in segments. Think of it like this - each floor of each building gets its own network, and then the buildings have routers that connect all of those networks together, and then those routers connect to the campus' data center where there are bigger routers that handle connecting not only the buildings to each other but the entire campus to the Internet at large. As far as the WiFi goes - when you're deploying a campus-wide network, there will be centralized management of the access points in order to handle things like channel assignments and client management. Every access point is given the same name and to a user looks like seamless coverage, but there will be dozens if not hundreds or thousands of access points blanketing the campus with the same SSID. However, those access points are all going to be working on different channels so as to not overlap signals with each other (either in the general 1-6-11 configuration to eliminate channel overlap or in a 1-4-8-11 configuration to simply minimize it). As well, the central management of the access points will work to try and prevent a single access point from getting overloaded. Throw 200 people into a lecture hall with one access point and the amount of effective bandwidth for users is going to be quite minimal. But if you have ten access points in and around the lecture hall, the server can force clients to disconnect from one access point and reconnect to another access point with a decent signal strength so that you have people on the edges of the hall connecting to access points in other rooms so that each access point gets 20 users competing for the bandwidth instead of 200. Access points can be connected in two ways - wired or mesh. If an access point is wired, as most access points in a campus-level network should be, it will have its own dedicated bandwidth that it can serve of either 100 Mbps or 1 Gbps. If the access point is connected in a mesh configuration, bandwidth management becomes more complex because the access point needs to use its radios for both serving clients and getting their traffic upstream. Why does it work better in some places rather than others? There are a lot of reasons for that. It could be that other users are causing bandwidth congestion - a couple of people connected to the same access point are watching Netflix, so you go to download a file and find that the pool of bandwidth you're sharing is mostly going to serve them instead of you because their usage is more constant than yours. It could be that there are too many users connected to the access point - wireless bandwidth is a shared pool among the users, so the more users there are the more contention there is to try and use the same bandwidth and the more overhead increases trying to separate everyone's traffic. And it could be that you're getting a bad signal - your radio might indicate that you're getting a good signal power, but the wall between you and the access point might be scattering that signal to hell and back in a way that causes both your device and the access point to have to constantly resend data to ensure it's being received properly."
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71nqos | when taking a pic of the solar eclipse with a smartphone, why does a smaller image of the eclipse appear below the original? | Technology | explainlikeimfive | {
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"This is likely due to the lens system of your phone having internal reflections within its structure. The image projected onto the sensor is very bright and might for example reflect onto the inner surface if the lens and be reflected back onto the image sensor a second time.",
"I believe this is because that smaller image is actually the reflection of the eclipse on your camera's lense. If you were to take the picture while tilting your phone in different ways it should appear in different places."
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71oiyi | How does a hypodermic needle not just get gummed up with a core sample of the flesh it pierced into? | Technology | explainlikeimfive | {
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"A needle is shaped so that the flesh goes around the needle, not through it. The front of a hypodermic needle is ['beveled']( URL_0 ), which means it has a slanted shape. You put the pointy side to the skin when you go in, and it separates the tissue so it doesn't go into the hollow part of the needle. It also (usually) makes it less painful as it pierces less nerves on its way through. It's kinda hard to explain, but very simple when you take a look at the cross-section.",
"Former syringe production plant maintenance supervisor here I worked for Terumo before The needle/catheters are immersed in a chemical lubricant to make them slide easily making them less painful Also we randomly sample each batch of needles to a pain test machine to determine if it will be painful Also the tip of the needle is bevelled to lessen the surface area being penetrated by the needle this prevents tissues from clogging the needles",
"It is because the needle is beveled. So there is actually a right and wrong way to insert a needle. If you were to insert a needle bevel side down, it would be a lot more painful.",
"There are lots of good answers here but I have to say, sometimes they do. I donate a lot of blood. I noticed when they take a blood donation they go through a lot more sterilization compared to when I get an immunization. I asked about this and the nurse told me it was not for my benefit but for that of the recipient. Sometimes the needle makes a skin plug that ends up in the donation so they want the skin to be as sterile as possible to avoid contamination of the donation. This is even with a beveled needle though they are kind of large.",
"Hypodermic needles have a beveled tip. This effectively means that the hole on the needle points in a different direction to which the needle is cutting. The shape of the bevel cuts the tissue and pushes it away from the hole. Some needles are designed to plug up with tissue, and these are used to take a sample of organ tissue, and these have a hole at the front edge and a straight cut and sharpened tip. You insert the needle onto the organ, the needle plugs up, and you twist the needle to break off the plug, pull the needle out and push a rod down the needle to extract the plug."
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71p5vw | what kind of applications won't benefit from increased multi-thread performance? | Technology | explainlikeimfive | {
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"One reason is if the application is primarily I/O bound. Adding more threads won't make your hard drive any faster.",
"Applications that only have one thread, of course. Writing a multi-threaded application is a lot more work. The computer can't parallelize tasks for you. Imagine you've written a recipe for a teenager to cook dinner. The teenager is new to cooking. They're great at following directions but they don't really know much about cooking yet so they can't really improvise and they don't understand the purpose. But if your directions are clear it works great. Now the next day they bring a friend. Now there are two teenagers following the recipe. Will they get it done twice as fast? No, for two reasons: 1. First of all, some steps just can't go faster. If it needs to bake for an hour, you're never going to finish making dinner in less than an hour no matter how many cooks are in the kitchen. 2. Second of all, unless you carefully plan out how to keep both of them busy at the same time, they won't actually be any more efficient. You've only got one stand mixer, and if they both need it at the same time, one will be sitting around doing nothing while the other one is using it."
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71ptiq | If there is water on Mars, why can’t one of the rovers be directed to the suspected source and simply confirm or deny speculations? | Technology | explainlikeimfive | {
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"> why can’t one of the rovers be directed to the suspected source and simply confirm or deny speculations? Rovers are extremely slow, you can't just drive them to wherever you want. [Opportunity travelled 45km in all its 12 years on Mars]( URL_0 ) We know (for a long time now) that there is indeed [water (ice) on Mars]( URL_1 ), no need to send a probe there just to confirm it.",
"Because the water is not in a form of lake or a block of ice. It is more like permafrost. Wet martian soil that is permanently frozen deeper under the surface. It thaws a little during martian summer and wetness can be observed flowing down martian hills. Again not a river just water soaked into soil. Soil stays mostly put and the water flows down through the gaps between soil grains. Martian hills are hard to traverse for rovers and their equipment is designed to take relatively shallow surface samples. Also what needs to be addressed is public opinion on what qualifies as proof of liquid water on Mars. Scientists can show graphs, spectrometer findings and maps constructed by orbital probes and say that this is strong evidence but public will remain skeptical. What public wants is a picture of a lake but that is not what they will get.",
"It was a rover than let us know there's water on mars, and completely by accident! One rover, called Spirit, was sent to mars to look around, and one of it's back wheels broke. But that didn't stop the rover, it carried on driving, dragging a little trench in the dirt behind it. In that trench we noticed shiny white stuff, which could be snow. So the rover turned around to get a proper look at it, and Bingo it was snow! Spirit has a partner, called Opportunity, but it's aaaaaall the way on the other side of mars. Using both rovers to look around, we made sure we weren't seeing imaginary things. It seems that if you dig almost anywhere on mars for long enough, you'll find some snow and ice mixed into the dirt. And we thought mars was a dry ball of dust all these years. Turns out, it's a very soggy ball of dirt instead."
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