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dbtrd5 | How do Qi chargers actually work? (The ones that you just sit your phone on top of) | Technology | explainlikeimfive | {
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"When electricity flows through a coiled wire, it creates a magnetic field. Similarly, when a magnetic field passes through a coil of wire, it creates electricity. As you may have already guessed, a Qi charger has a coil of wire inside that it passes electricity through. Your phone has a matching coil that links up with the magnetic field generated by the charger and uses that to create electricity which it uses to charge itself."
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dbtrtu | how does the ice machine in the fridge make ice? | Technology | explainlikeimfive | {
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"A water supply line fills an internal ice mold and when the water has frozen into cubes a mechanism flips out the cubes into the ice bin. If there's an in-door ice dispenser, there is a flapper in the bottom of the bin and an auger to pull ice forward toward the opening when the dispenser is activated."
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dbv5hd | What is it about the numerical font used at the bottom of checks that makes it easier for computers to read? Why was that chosen as the standard? | Technology | explainlikeimfive | {
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"Even though as /u/joestone points out, these characters are printed with magnetic ink, the font is still important, because whether they're scanned magnetically or optically, the shape of the digits is still what counts. Consider a reader that scans from left to left to right and only looks at three points on the top, middle and bottom of the digits. Whenever all three inputs say there's nothing, that's a character break. Between each character break, the three points will translate to a set of dashes and dots For instance, the 7 digit will make a dash on the top, a centered dot on the bottom and a centered dot in the middle. It's easy for a computer to then take those dashes and dots and find the closest match in a lookup table. EDIT: It turns out that the left to right scan doesn't use multiple signlas, but rather a single signal measured by the total vertical amount of ink in the character as it reads.... this creates a single signal of peaks and valleys as shown here: URL_0",
"In addition to what others have said, observe how all the digits have significant differences to each other. For example, the 5 and 6 have the horizontal line at a different height. This means that you can't modify a 5 to look like a 6 by adding a bit, or vice versa. The top half of the 8 is narrow, so you can't make the 0 look like an 8 by adding a horizontal line.",
"It isnt the font that they use...those numbers are made of magnetic ink. They are ran through a MICR machine that reads those magnetic numbers."
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dbwwg3 | What are floating numbers and why are they stored seperatly from integers in computers? | Technology | explainlikeimfive | {
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"* Computers have a fixed amount of memory. * That means we have to decide how much memory we need to set aside to represent numbers. * Let's say we choose 5 digits. That means we can represent numbers from 0 up to 99999. * What about negative numbers? If we steal one of those digits to represent the sign (+/-) then the we can go from -9999 up to +9999. * That's pretty fancy but what if we really really really need to store the number 0.000000001 ? * We don't have enough digits, right? * Actually if we are very clever, we do. * We use one digit to store the sign (+) * We use another digit to store the number part (1) * We use another digit to store whether this number is greater than( > ) or less than( < ) 1. * Then we use another digit to tell us how many decimal places before the number. * So it would look like this: * \\+1 < 9 * We could go the other way too and store: 100000000 * \\+1 > 9 * This dramatically increases the range of numbers we can store using just a small number of digits. * But as you can see it takes extra effort to code and decode this numbers. * That's why in programming they are different types. * **NOTE** Some of this has been simplified for ELI5, mainly how I mix digits and characters, but this was to avoid having to explain binary which I feel would just further complicate a relatively complicated topic to begin with.",
"Floating numbers are numbers which have decimals, unlike integers which are only whole numbers. I think with separately, you mean in a different format? Since everything is just stored in memory, whether it's an integer or floating point number. The reason why they are stored differently, is because with floating point numbers you need to account for the decimals being there, while this isn't the case with whole numbers."
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dbzd8z | Why do dead cell phone batteries need to charge for a while before booting but dead laptops can boot immediately upon plug-in? | Technology | explainlikeimfive | {
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"Ok geez people. Stop guessing if you don't actually know. The real reason is that they are programmed to not turn back on until the voltage of the battery has recovered a bit to make for a more consistent user experience. The chips inside a cell phone operate at 3.3V, 2.5V and/or sometimes 1.8V. in order for these voltage rails to be maintained you must have more voltage than to prevent what is called a brown out, or basically under the absolute lowest voltage required for the chip to function. Lithium ion batteries are basically 95pct dead at 3.5V or less. 100pct dead at 2.5V. but most phones are programmed to shut off between 3.0 and 3.25V. This is a lot lower than laptop batteries are allowed to go because cell phones are designed to use proportionally less power than laptops. Users also demand every last bit of juice out of their cell phones. So even though the phones can turn back on immediately and be fine, because chargers can deliver about 5Xs as much power as a cell phone can use, a conscious design decision was made to not let the user do this."
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dc0jva | How exactly do magnetic waves become encoded/decoded (ie. on tapes) | I'm fascinated by this article URL_0 Disney used magnetic tape to play commands for animatronics while rocket scientists used magnetic tape to guide nuclear missiles. All the explanations have said that a tape head is able to "read" these magnetic waves on plastic tape but do not go into the actual science/physics of it. Any help? | Technology | explainlikeimfive | {
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"If you take an unmagnetized screwdriver, and put it in a strong magnetic field, it becomes a magnetized screwdriver. The magnetic tapes are similar, they stay magnetized after they're exposed to a strong magnetic field, You write on such a tape by running electricity through a coil of wire in close proximity to the tape, and read such a tape by running it over another coil of wire, so the tape's changing magnetic field will induce electric current in the coil. That signal is then amplified and decoded to do whatever it is you want to do. The plastic itself isn't magnetic, there's a thin film of magnetic material bonded to it.",
"A tape head is a type of transducer. It can convert electric signals to magnetic fluctuations, and vice versa. Basically you have a coil of wire with a gap in it, and the gap is filled with a diamagnetic material, like gold. If you apply a variable magnetic field at the gap, it'll induce an electric current in the coil. If you run current through the coil, it'll create a magnetic field at the gap. When you record, you run a magnetic tape past the tape head. The electric signal comes from your microphones (or your other instruments.) As the tape runs past the head, a magnetic field is \"imprinted\" on the tape, which happens to be the same as the electric signal that came into the tape head. When you play, there's no current in the tape head. As the tape runs past the head, its magnetic field induces a current in the coil that corresponds to the one imprinted on the tape. The coil is connected to an amplifier, and what you hear out of your speakers is the same as what was recorded on the tape."
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dc30e9 | How do logic gates calculate their output? | Do transistors calculate the output? If so, wouldn't transistors be the most fundamental logic of computers? Thanks. | Technology | explainlikeimfive | {
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"Yes, transistors are the building blocks of logic gates, which are the building blocks of computers. But they don't really 'calculate' their output: they're too simple for that. At its most basic, a transistor is a switch that lets electricity flow through it when it receives electricity from a \"control\" input. So for example: `power` `|` `T ----A` `|` `output` The transistor is labeled \"T\". If electricity is put in on input \"A\", electricity will flow from the power supply to the output. If \"A\" is off, nothing will flow to the output. So if we hook two transistors up in a chain: `power` `|` `T----A` `|` `T----B` `|` `output` electricity will only flow all the way to the output if there's electricity coming in on both input A **and** input B. This is an \"AND\" gate. But if we create two parallel paths like two lanes of a highway, and have A and B each control one \"lane\", then electricity will flow through if either A **OR** B is on. This is an OR gate. (Unfortunately I can't draw this with ascii art on Reddit.) ... and that's the starting point for all of computers.",
"If you're interested, I highly recommend trying this online game: URL_0 You start with a nand gate, and combine them for form new gates, and eventually create a basic working CPU (in a digital sandbox).",
"I would highly recommend checking out Ben Eater’s channel on YouTube. He has great videos that explain how computer hardware works, and he does so by building them out on a breadboard, accompanied by diagrams, etc. For your particular question, his 13 minute video ‘Making Logic Gates From Transistors’ ( URL_0 ) takes you through each logic gate in a simple to follow format, and he builds them out with transistors. Other videos of his include building a basic 8-bit computer, RAM modules, and even a video card from scratch with explanations. He’s also now selling kits so you can follow along with his builds.",
"[I can’t believe this hasn’t been posted yet. It is Matt Parker(not South Park) showing logic gates with dominoes.]( URL_0 )",
"Let's define a transistor as a 3 pin device that uses a signal at one pin to control the current flowing between the other two pins. In digital electronics that control signal would either be 1 or 0. With multiple transistors we can connect the transistors in such a way that only certain combinations of inputs at the control pins will allow current to flow through the load. I recommend looking up CMOS gate circuits to get a better picture of how this works.",
"Transistors do ultimately calculate the output. It would be fair to say they are the most fundamental logic element in a computer. Using methods described by other people ITT you can build basic gates like OR, AND, NOR, NAND, XOR, etc. The next step is to chain multiple gates together to come up with something more useful. You can implement a lot of surprisingly complex calculations by doing this. Addition, subtraction, multiplication, and a lot more are possible using only basic logic gates. This is called combinational logic. To take it to the next level you need *sequential* logic. You use a *flip flop* (which itself can be implemented using transistors) to store the output of one calculation. Then you can feed that output into another combinational circuit to do the next step of your calculation. This allows you to chain multiple calculations together. That's essentially what a program is. A list of operations which are calculated sequentially.",
"P1 Introduction So traditional math is decimal-based, or base 10. This mean number representation can be represented by exponents of 10. Notice the bolded. A number like 69 would be represented by **6**\\*10\\^1 + **9**\\*10\\^0. A number like 420 would be represented by **4**\\*10\\^2 + **2**\\*10\\^1 + **0**\\*10\\^0. P2 Binary Binary is base 2. So numbers are represented by exponents of 2. So, 2\\^0 is the right most, 2\\^1 is the second right most, 2\\^n is the n+1 right most. A number like 69 would be represented by 1000101. or **1**\\*2\\^6 + **0**\\*2\\^5+ **0**\\*2\\^4+**0**\\*2\\^3+ **1**\\*2\\^2 + **0**\\*2\\^1 + **1**\\*2\\^0 = **1**\\*64 + **0**\\*32 + **0**\\*16 + **0**\\*8 + **1**\\*4 + **0**\\*2 + **1**\\*1 = **69** P3 Logic Gates & #x200B; Logic gates are, well, what the name implies: logic gates. They just take in two inputs and throw out an output. The two basic logic gates are 'AND' and 'OR'. The outputs are as followed: AND GATE = f(a,b) = a\\ & b; f(0,0) = 0; f(0,1) = 0; f(1,0) = 0; f(1,1) = 1, which makes sense for an AND gate. It should only throw out TRUE or '1' if both are 1. OR Gate = f(a,b) = a|b; f(0,0) = 0; f(0,1) = 1; f(1,0) = 1 f(1,1) = 1, which makes sense for an OR gate. It throws out TRUE or '1' if either a or b is TRUE or 1. There are more gates like XOR, NOT, and NXOR. & #x200B; P4 Adding Decimal adding is simple. 10+9 = 19. You sum up the ones column, and then sum up the tens column. 9+2 is a bit funky, but we know it's 11. It's 11 because since the biggest that a place can hold is 9, we carry over values into the ten column. So, the problem becomes 10\\^1 + 1 = 11. The same concept applies to binary. We want to add A and B, but we have to keep in mind that the biggest digit we can hold is 1 |A|B|SUM| |:-|:-|:-| |0|0|0| |0|1|1| |1|0|1| |1|1|??| We can see that this is pretty much an OR gate but with ?? So what becomes of the ??. We would expect to be 1, but we know that it's not true. It should be 10. Since, we had to carry over the 1. But this is only the 'ones' column, so ?? is just 0. & #x200B; & #x200B; |A|B|SUM| |:-|:-|:-| |0|0|0| |0|1|1| |1|0|1| |1|1|0| Again, this looks like an OR gate, but 1 OR 1 should be 1, not 0! Though it's not an OR gate, this is still a gate, this is actually an output for an XOR gate (where you only want one true value). & #x200B; But, what do we do with the carry digit? Well, we want some form of logic that only does a carry digit when we see 1 + 1. & #x200B; |A|B|CARRY| |:-|:-|:-| |0|0|0| |0|1|0| |1|0|0| |1|1|1| Now, this is just a straight up AND gate. Now we have just made a basic adder (half-adder call it). Meaning we can show A+B with just an AND-gate and XOR-gate. Though, it can only add up to 3 (or in binary '11') & #x200B; |A|B|CARRY|SUM| |:-|:-|:-|:-| |0|0|0|0| |0|1|0|1| |1|0|0|1| |1|1|1|0| To make a full-adder, of which I won't go over, to do math like 19+21, where you have to add the carry value into 1+2 in the tens column, we need another OR gate. You can probably find a break-down of the table somewhere on google. But, in any case, if we just extend a bunch of these adders together, it becomes a simple adder, where the number of digits is based on how many full adders you have.",
"To understand computers you have to understand that everything is built upon layers and layers (and layers and layers) of abstraction. Just like a computer language like C is an abstraction of a more low level form like Assembly (which is itself an abstraction of the pure binary), logic gates are an abstraction of groups of transistors that together do a simple operation. So, if I'm going to design a circuit that adds two numbers together, yes I could go down to the very lowest level and map out every circuit and transistor involved, but doing so would be complicated and difficult to troubleshoot. Sticking an abstraction layer of logic gates in there makes it a much more human tractable problem. In reality a ton of chip design is done by computers these days with even higher level abstractions on top for human readability and input. Verilog for instance more closely resembles computer code than what you might expect chip design to look like. But none of that is a very good ELI5, so let me try again. Logic gates are like Lego blocks, the simple old fashioned ones. You **could** build the exact same models out of only flat Lego pieces and not using blocks at all, just stick the flat plates together until you get the shape of the larger blocks. But no one would want to do that, it would be tedious and you'd likely mess it up somewhere along the line. If you really had to build a whole set out of only flat pieces, you'd probably start by putting flat pieces together into the shape of the larger more friendly blocks that the instructions actually call for. Transistors are the flat pieces, by themselves it doesn't look possible to make much interesting out of them. But when you think about a collection of flat pieces as a bigger block it's easier to imagine making a huge castle from them. So what's more fundamental, the shapes that people build with every day or the shapes that deep down make up those shapes? It's just a matter of semantics.",
"You can make some gates with just diodes, but you'd need a transistor to get the voltage back up near the input voltage. For example diodes in parallel, plus a resistor can make an OR gate or an AND gate. A transistor and a resistor can make an inverter. An AND gate and an inverter is a NAND gate. NAND gates can be used to make all the other gates.",
"here's the tl;dr version: a computer doesn't \"calculate\" anything in any cognitive sense like a human does, it just ends up throwing out electrical pulses that add up in binary to the numbers added, like some kind of automatic electrical abacus. & #x200B; I know people are gonna gripe with this explanation, but I was going for very short and succinct.",
"Compute is probably the wrong word at the level of a transistor. At this level you’re just describing components. Transistors don’t compute as they alone don’t allow you to recognize any mathematical output for a given input. They simply control the flow of electricity. You need wires, at least two transistors, a voltage source, and a voltage drain to create a unit of computation called a gate. A gate is a configuration of electrical components, that’s flow of current represents a mathematical computation on some input to derive an output; it only means something because it can be interpreted by a human. A gate is the smallest unit of computation because nothing smaller actually computes anything, whereas a transistor, like a wire or a voltage source, cannot represent any mathematical process. The two fundamental gates are NOT and NAND (or NOR) and all other computations can be generated from configurations of these gates. Edit: I want to say there *is* a trivial computation that can be performed by just a single wire: the identity function, f(A) = A. This is computed by simply connecting an input pin to an output pin. This is not very interesting and it can’t be used to construct more interesting computation so it’s not really fair to call a wire the basic unit of computation."
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dc4tds | How does a Dry Cleaner work? Beginning to end? | I don't know why I have never questioned this before. What actually happens inside a dry clean store? | Technology | explainlikeimfive | {
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"Drycleaning machines use a product called Perc (sort of like a gasoline solvent) to clean clothes. The machines are a washer/dryer combo so it’s a sealed unit. The solvent keeps clothes from shrinking and getting crazy creased up. Then its the usual pressing machines - one specifically for pants, one for shirts, jackets and blazers and then normally a presser for other stuff plus irons. All the pressers abs irons are steam based and they tend to have a huge boiler to make it all run. My parents owned a Drycleaners my entire childhood, so spent a lot of time there!"
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dc90cv | Networking. What is the difference between layer 1,2,3 switching? | I slightly understand what they do but only by definition. I cannot picture in my head what they are actually doing. | Technology | explainlikeimfive | {
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"These three layers aren’t inherent to switching. They map to the OSI (open systems interconnection) model The layers are *abstraction layers* and just like the best burrito at Taco Bell, there are seven. Arguably the most important thing to know is that communication occurs only on a successful hierarchy of layers. That is, you must have good layer 1 before you have communication at layer 2. And 2 is thus a prerequisite for 3. This is why nerds with gray hair will remind you to always start troubleshooting at the bottom of the stack. The first three are collectively the “media layers” Layer 1: physical layer. The physical cables (copper, fiber optic, etc) Layer 2: data link layer. This is where a data frame is sent between nodes connected by a layer 1. The most common use is Ethernet framing. Layer 2 is where Ethernet functions like spanning tree, ARP, switching, and 802.1q tagging happen. So calling it layer 3 switching is kind of marketing. All switching is layer 2 otherwise it’s routing, just on a switch chassis. Which brings us to: Layer 3: network layer. Simply put this is where IP addresses and packets live and routing happens.",
"As this is ELI5 i'll keep it as simple as possible. Imagine a switch as a box that connects multiple pipes. Layer 1: This switch is stupid and is more commonly known as a hub. Everything that comes in from one pipe will be distributed to every other pipe connected to the box. Layer 2: This switch is a little bit more intelligent. It can see to whom the package is addressed and will only send it to the pipe on which the recipient is connected. Layer 3: Here comes even more intelligence. Layer 3 switches have some managing skills and can do things like prioritize important packages. There are also \"Layer 4\" Switches but this is more marketing speech for Layer 3 switches with a lot of functions.",
"Imagine this as the postal service. Layer 1 is the postman, layer2 is the envelope and layer 3 is the letter inside....( the higher layers would be the layout, font and language used)..."
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dcc2fh | Why do digital cameras and lenses range in price from under $100 to tens of thousands, and at what price point are there diminished returns (for the average person's eye)? | Technology | explainlikeimfive | {
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"* Build quality * Image sensors and processing capabilities (you need processing power to encode video, for example) which can affect video recording capabilities, image resolution and quality, color calibration features, etc * Lenses. A $100 camera is going to have a fixed lens. DSLRs are almost always $400+, usually $600+ and let you swap out lenses which produce a vastly superior picture when you're using the right lens for a situation and know what you're doing. What's the price point at which you start experiencing dimininishing returns? Depends on your definition of \"Average person\". Your average person doesn't own a dedicated camera and uses a smartphone which is good enough for day to day use. What it really lacks is performance in low light, lack of optical zoom, lack of fine, true (as in not software-based) control over stuff like ISO, fstop, shutter speed. Most people are fine enough with this to not spend $500+ on a single purpose device that can't fit in their pocket. Your average photo enthusiast that wants a dedicated camera is likely to be looking at an entry level (~$500-600) or mid range ($700-900) DSLR. A mid-range DSLR will probably do for some professional purposes as well."
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dcdqrn | How does color on a computer screen work? I always thought that color was a way that light reflects on different materials/objects. How does this work on a TV/computer screen? | Technology | explainlikeimfive | {
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"color is determined by the light that enters your eyes. Since most objects don't glow (at least in the visible spectrum) and are mostly opaque, that light is typically reflected from another source. But sometimes the light is filtered through an object (as with tinted glass) or is emitted directly by the object (as with a red-hot piece of metal). Either way, your brain perceives a color based on the light that enters your eyes from that object. Computer screens are a combination of emission and filtering: a back light emits light that passes through a color filter that changes the light's color. The interesting thing about computer screens is that they only have three colors. The way a computer screen can replicate most colors with only three is based on how the human eye works. The human eye doesn't actually have a way to say \"oh, this photon has x wavelength, so it is y color\". Instead, the color-sensing cells in your eye have three variants. Each variant responds a little to all visible light, but each variant also has a \"favorite\" wavelength. Light closest to the \"favorite\" wavelength make that cell respond more than light with a wavelength farther away. The favorite wavelengths for each type of cone are (more or less) red (really closer to yellow-green, but let's just say it's red), green, and blue. Then when light of a certain wavelength is shone into the eye, the eye and brain go \"oh, the Red cells are stimulated X amount, the Green cells are stimulated Y amount, and the Blue cells are stimulated Z amount, so the light must be *this* color\". The thing is, you can then cheat the system by having a red, green, and blue light next to each other, and setting the red light to shine with X brightness, the green light to shine with Y, and the blue light to shine with Z (again, it's a bit more complicated but that's the general idea). Since they stimulate the eye in the exact same way, the brain has no choice but to see it as the same color as before. & #x200B; This general concept is also how things like paint mixing work.",
"They only use blue, green, and red. The saturation or amount of each, tricks your brain into thinking it is a particular color outside of that, but it's not. If you get really close to a screen you can see this. It is trickery and nothing more."
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dcey6p | How does fast charge actually work? Why was this never introduced before? | Technology | explainlikeimfive | {
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"standard chargers works at 5V and up to 2A for most phones. fast charge uses 9V and up to 2A for most phones. the amount of \"power\" transferred is the V \\* A. So by using a higher voltage, it charges faster. this requires a more complex circuit, so it's more expensive. and charging faster always has the potential to wear out your battery faster than charging slower.",
"The speed of energy transfer is called \"power\", and is measured in watts. Bigger batteries means you want to transfer energy faster (increase watts), so you can charge within reasonable time. Power is volt times current. (Watts = volt * ampere) At first, USB was always 5 volt. There's no simple way to make the voltage variable. The variable for charging speed is current. According to the formula, double current is double charging speed. A standard USB port cannot supply more than 0.5 ampere. A new USB charging standard came out allowing more than 0.5 ampere, this is generally referring to as *fast charging*. Well, it was. It's now considered \"normal\" or \"slow\". The next bottle neck was reached when they got to about 2 ampere (10 watt). The USB plugs is not designed to handle more than that, and there's no way to get around that without changing the plugs. But in the mean time, what was considered too complicated (=expensive) before, is now doable. The connection is initially 5V, but there's now several ways that the phone and charger can communicate, and and agree on a higher voltage. It's usually 9 volts, but its can also be 12 volts or even higher. Increasing charging speed by increasing voltage is generally referred to as *quick charging\". Which is slightly confusing because some of the standards are actually called Quick Charge (and are owned by Qualcomm), while the rest have different names. Plus it sounds a lot like fast charging. But it's all relatively simple, because a USB \"charger\" is actually not a charger. It's just a power supply. All the difficult stuff is still in the phone. Then came the new connector - USB C, and it got even more complicated. Competition with Qualcomm Quick Charge is for example Warp Charge. They actually push up to 6 ampere through the cable while staying below around 5V achieving 30 watts, or Super VOOC that goes up to 10V at 5A, theoretically achieving 50 watts. It's really getting really complicated now, because the protocol to negotiate power between phone and power supply is getting increasingly complicated. Both technically and legally. They are also moving at least some of the features needed for charging to the charger. So if you plugin an old fashion \"dumb\" USB power supply, you get good old fashion charging speed. But if you plugin your original power supply that came with the phone, it replaces some parts of the charging circuitry and enables modern super speed charging."
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dchbex | In old cartoons why were the animated pieces of each scene a different colour than the static pieces of the scene? | Technology | explainlikeimfive | {
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"That usually means that the background and other \"static\" images are painted and the actual characters and anything that moves is drawn. They did it to save time instead of drawing out the entire scene over and over.",
"The background ‘cels’ were normally hand painted and created with more detail that were traditionally static or limited in movement. The foreground pieces were limited in color palette (no highlights/shadows) due to the complex movement of the characters. Typically, animation filmed at 24fps (frames per second) was shot in twos, meaning for every second of animation the camera ‘shot’ the image twice. So there were typically twelve drawings that required ink and paint and for the sake of production time they obviously limited their colors. Source: studied animation in college. A great reference is the late Richard Williams’ book ‘The Animator’s Survival Kit.’ The Animator's Survival Kit: A Manual of Methods, Principles and Formulas for Classical, Computer, Games, Stop Motion and Internet Animators URL_0"
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dcloc1 | How come headphones get a loud high pitch sound whenever they get close to something such as a metal detector? | Technology | explainlikeimfive | {
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"Speakers, of which headphones are just tiny ones, are simply a wire surrounded by a magnet. Put electrical pulses through the wire, and connect the end of the wire/magnet thing to a surface that can vibrate, and you have a speaker. Anything that can mess with a magnet or the electrical current in the wire can mess with the sound."
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dcm31o | What are cookies from websites? | Technology | explainlikeimfive | {
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"A cookie is just a bit of data that the website stores on your computer to look at next time you come back. A common and very useful application of cookies is storing what account you logged into so that you'll be signed right back in when you reopen the site. What gets more ethically dicey is when the cookies are being used to store information about you for things like advertising (e.g. storing that you looked at X and then showing you ads about it) without your consent, which is why you see warnings about using cookies on websites.",
"Imagine if, after the first time we met, i’d write down what i knew about you on a post-it note and stuck that on your chest. Next time i met you, i could consult the note to steer our conversation accordingly."
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dcnygo | why isn’t it feasible to use wind or solar power (clean power) to run desalination plants to solve water crisis? | Technology | explainlikeimfive | {
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"Perth Australia does it with wind power. [Cockburn Sound]( URL_0 )",
"Basically money. Desalination requires a lot of equipment and energy to run on a large scale, and solar panels/ wind farms (if the latter is even practical in the area in question) tend to get very expensive.",
"Its not profitable. Solar and wind produce a power output over a year that looks more like noise than constant power. So you can't really calculate with that let alone run a profitable business. Sure it's technically possible but nobody will do it because you can't really make money with it. For a steady clean water output you will need a steady power supply."
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dco438 | How does Google's "Use overtime" feature work? | Whenever we search for a word on Google, we get this graph showing the usage of that word over time periods from the 1800s. How does it work? Where do they get that information from? | Technology | explainlikeimfive | {
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"Google has an index of most of the public internet, and millions of scanned books/documents (google books, google scholar, project Gutenberg, URL_0 , ...). This means that they can simply ‘count’ the use of words over time by going through their index."
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dcqkam | What is Big Data and Data Analytics? | Technology | explainlikeimfive | {
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"text": [
"Big Data is having a large volume of data (like say the data of all Facebook users) that covers multiple aspects/categories (such as browsing habits, likes/dislikes, ads watched, ads skipped, location data, work history, time the app/site is used, post history, etc.) A good video about it. Data analytics is looking for patterns in this data and then doing something with the patterns. For example if I notice that the majority of dog owners ignore Purina ads, but love/watch Chewy ads, I might ask Chewy to pay a higher fee to advertise on my site. I might also notice that the majority of people who have cat pictures on their social media also have a lot of listens to Mr. Brightside on Spotify so I buy ad space on Spotify's Mr. Brightside playlists for my cat toy website. A set of videos about data analysis."
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dcrsit | How do remote control things work? How can I press the up lever on a controller and make an RC car move across the room? | Technology | explainlikeimfive | {
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"Pressing the lever on a remote control device, activates a mechanical switch that powers part of a circuit inside the controller. That circuit then powers a wireless transmitter to broadcast a wireless signal (like a radio) which the antenna on the car picks up. And much like a radio the car has internal electronics which interpret and translate the signal to perform some function, in this case the signal sent when the controller's left lever is pushed up tells the car to power the motor in a forward motion, so the car moves forward. Just like a video game controller, each input on the remote control sends a different signal to the device, which is in turn interpreted into different operations within the car: \"turn the wheel servo's left\" \"engage the drive motor in reverse\" etc. There are a number of ways in which we can wireless transmit input signals: Bluetooth, UHF, RF, Infrared, etc. These are all different methods of wireless transmission, and require the receiving device to be capable of receiving the signals, and then in internal computing circuitry is programmed to understand and react to the received input."
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dcs3le | Why does Braille use raised bumps instead of raised letters? | Technology | explainlikeimfive | {
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"text": [
"Letters and numbers share shapes that are easily mistaken for one another ( 6 G , W VV , O D , etc.). Braille has been set up in a way that minimizes risk of mismatched characters.",
"The pattern isn't that clear to read from a letter and different fonts would use different ridge detail this way the pattern is set, standardised and easy to identify."
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dcs71f | Why mining for Helium-3 is that unprofitable | Is it due to lack of research on application or just overall cost of mining and transportation overcoming it's value? & #x200B; upd: Talking about lunar surface supposingly containing huge amount of helium-3 | Technology | explainlikeimfive | {
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"Well, it costs a lot to mine on the moon. Meanwhile, nobody really wants helium-3 for anything. Like, some He-3 is useful, but we can already breed it in reactors and we definitely don't need that much.",
"Because it's more or less worthless. helium-3 is by weight not really worth much more than the dirt in your back yard.",
"Helium 3 isn't use that much right now and for the foreseeable future. There is really only a few usages for H3 right now and we are FAR from being able to use it for nuclear fusion, and this might never happen. So as long as nuclear fusion with H3 isn't a thing, there is not reason to go to the moon. In the future, when we already have some presence on the moon and nuclear fusion using H3 become economically viable, then in that case H3 mining on the moon could be profitable. But keep in mind that the H3 on the moon isn't really concentrated and more spread out over the regolith, so maybe it will never be worth it to mine H3 on the moon.",
"The cost to get anything to the moon is substantial. You need to send a lot of stuff to the moon to set up a mining operation. You need to send people to the moon to help set it up. If personal are needed to maintain the operation, you need to have a full-fledge lunar base. You need to set up a transportation method to get mined stuff back. The cost of all that far outweighs any profit you might get from selling the products back on Earth.",
"If you were to use it as rocket fuel it would make a lot more sense to mine it on the moon and use it on the moon to launch rockets. But of course that requires a lot more infrastructure."
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dcskqd | How "hackable" are public transportation cards? | I was on my daily transportation route and started thinking about this and since I've never seen anything about it, I figured the chances would be slim. The machines where you buy tickets/rides need to interact with the cards chips somehow to "transfer" whatever you purchase to the card so my question is, how hard would it be to "fake" a purchase as if it had been done in one of those machines? | Technology | explainlikeimfive | {
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"Assuming that the cards use some form of encryption (which they probably do) it would be somewhat tough, depending on the security of the machines themselves. The way these cards usually work is they send an identifier and an encrypted message - basically, they tell the reader, \"I'm card 12345 and here is a message that only card 12345 can produce: aqfeonfqefeqeo\". Thanks to the \"magic\" of private/public key encryption, the card reader can take that code, apply the key it has on file for that card and decipher the message, thus validating the card is who it says it is. This is almost impossible to fake - without the key on the card itself to generate the encrypted message, the reader won't get the correct response when it tries to decrypt and will see the card as a fake. The readers/ticket machines then make adjustments on the central server for that card - crediting or debiting rides depending on the transaction. Since it is incredibly difficult to fake the card itself, the only way to get \"free\" rides would be to alter the transaction records on the server itself - adding rides to a legitimate card by altering the database on the server itself. You could do this by either hacking the ticket purchase machine to add extra rides, or altering the central server to add extra rides.",
"You would have to hack the central system, not the card. All the card has on it is a number, when you purchase or use the card, it uses the number to find the account associated with the card and makes the update in the database, the card itself doesn't change. You could try to alter a card so you use someone else's account, but that is what the chip system is for. Also, if the system is designed correctly, there are millions of times more possible account numbers than actual accounts, so guessing one correctly is like winning the lottery.",
"Depends on the card. Older systems use weak encryption and have been compromised. Never systems have not yet been revealed publicly to have been compromised. The ones that have been compromised have vulnerabilities that allow card cloning, which is generally used to clone a company- or government-issued card, since they are least likely to notice the extra riding. Another vulnerability has been the use of \"master\" cards to access control rooms (for trains), which are themselves clonable. Mag-stripe cards are easily cloned (like subway tickets). I don't think it's terribly responsible for me to go into much more detail.",
"It's RFID. The chip in your card interacts with the device/reader you tap it on. You have a unique identifier in your card, the reader recognises it and links it to the account/balance your unique id is linked to, back in the database at the company or whatever. They're not easily \"hacked\" because the information isn't stored on the card itself, rather, it's in the \"database\" the reader is connecting to.",
"First, let's start with what are called signatures. Electronic signatures work by me giving you information that only I could know, and that you do not know, but can verify it's true. Every time we send each other signed messages, we give a new piece of information, and the signature is unique to the message itself, so you cannot use that signature to pretend to be me by copying my signature. Lastly, if I include the exact time I wrote the message in the message itself, you cannot repeat my message in the future without getting detected because either the signature will be wrong or the message will reveal the fact that it's old. The card effectively has two operations: 1. What is your balance? It will tell you it's balance, signed by the machine that last updated it (including the card's unique name). 2. Set your new balance. This updates what it will answer when asked. Whenever the machine adds or removes balance from the card, it: 1. Asks for balance check. 2. Verifies the identity of the card, and the machine that issued the balance. 3. Tells it to set its new balance. 4. Asks again to verify the update occurred correctly"
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dctj31 | how does a computer program arrange transistors to run a program? In other words, if transistors are so small, how can a computer ever know how to create the circuit required to run a program? | Technology | explainlikeimfive | {
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"A computer does not \"arrange transistors\". They aren't moved around to form circuits to run programs, they already are in the required configuration within the CPU. The CPU is manufactured that way with everything already in place as needed. Computer programs simply interact with the CPU as it is designed to perform their tasks. It is a matter of writing the program in such a way as to interact with the CPU in a desired way, and for that the size of the transistors is irrelevant.",
"Computer programs do not arrange transistors. They are fixed in place. Computer programs are simply a list of instructions which the cpu knows how to interpret and sends current down the correct transistors. Think of it as dominos lined in complicated patterns. You don't need to rearrange the dominos for each pattern, all you need is to be told which domino to push.",
"You're kind of putting the cart before the horse... The transistors are arranged in a way that the programs can interact with them. To put it simply, the program says. 1. Add memory block 1A to memory block 2A 2. If the result is greater than 42, then add result to memory block 1B. 3. If 1B divided by two has no remainder, then go to step 5, else go to step 4. 4. *Some other instructions that do stuff.* 5. *Some other instructions that do things.* All of that is done by the programs instructions triggering a chain reaction in the CPU. Sort of like a Rube Goldberg machine, except the outcomes can be different based on the instructions given to the CPU. Another way to think of it is that the CPU is just a really advanced calculator. Programs punch in numbers and the CPU gives the programs results; Except the CPU does way more than just basic math."
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dcy6dk | How does holding the power button on a computer force it to shut down? | My laptop froze and wouldn't even go into sleep mode. How does holding the power button longer make it completely stop? | Technology | explainlikeimfive | {
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"There is a dedicated chip for power management in the computer. A single press just send a signal to the operating system so it can initiate a shutdown. It start to shut down and when it has done what it need to do it signal the power chip back and tell it to turn off power to the computer. If you hold the button for a few second you tell the power management chip to turn of the power to the the rest of the computer directly. It is there so you can turn it off even if the operating system have crashed and it can't do a controlled shut down. What the operating system do when you press the power, sleep button or closes the lid is user configurable. In windows go to setting and search for \"power & sleep setting\". From here look for related setting to the right or the bottom and \"additional power setting\". Now to the left you have \"Choose what the power button do\" and you can change URL_0 a normal single press on the computer is configured to be the same as selecting shut in the menus.",
"There are various levels of programming and electronics in a computer. At the most basic level is the hardware itself such as the motherboard which all the components connect to. This has a BIOS (Basic Input/Output System) that performs the initialization of the connected hardware. It handles how the CPU, hard drive, etc. all talk to and work together. If a program running on the CPU, memory, and hard drive is having trouble the BIOS is almost certainly doing fine and not involved. That can be told to shut down by the long press on the power button and it can do this without those other components being freed from use by the stuck program."
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dcymot | With the new phones and induction charging my battery level is rarely if ever below 80%, does this affect battery longevity overall? What is the best way to maximise long term battery longevity? | Technology | explainlikeimfive | {
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"The battery level rarely going below 80% is actually good for battery longevity, as batteries no longer have a “memory”. However, new studies are finding that induction charging does shorten battery life. The electricity has to overcome an air gap, which creates heat. Heat is bad for batteries.",
"The best way to maximise batter longevity would be always charging to about 80%, with a cable and not too fast, and charge before it falls below 20%. AccuBattery reports Battery wear of 0.21 cycles for charging 20%-80%, and 0.94 cycles for charging 29%-100%."
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dd0bpf | How SSDs work? Why are they faster? | Edit: thanks a lot people! I did some research on the internet about SSDs and flash memories, but I didn't get them. Thanks for explaining, now I get it :) | Technology | explainlikeimfive | {
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"SSDs have a billion tiny little charge-storing transistors in them. Each of these can be on or off, and thereby store a binary bit. To write them you simply add or remove charge, and to read them you power the transistor and see what comes out. This is simple, elegant, and nearly instantaneous. However, it was impractical until modern semiconductor fabrication got a lot smaller, so instead we used hard disks. Hard disks are spinning disks which have magnetic data stored in them, and this is a comparatively slow system. When you want to read or write a bit, you have to wait for the disk to spin all the way around to the read/write head.",
"It'll be easier to explain if we start with how a traditional hard drive works, and why it's so slow. A traditional hard drive is basically the same as a record player. You have a spinning disk full info, and a little reader arm that runs across it to read the data. In order to find data stored at X location the disk has to spin so that the needed data is below the reader arm, and the arm has to read the data. All of that movement takes time. An SSD is just a series of semi-conductor chips. It's essentially a big, high-density, non-volatile RAM stick. No moving parts, so the the read/write can be as fast as the flow of electrons.",
"Not an expert but traditional hard drives require the disk inside to spin, while SSD's have no moving part, and the data stored inside is immediately accessible like RAM. It is only microseconds for each individual transaction but it adds up over time.",
"Traditional hard drives store their data on several rotating magnetic platters (disks), with drive heads that scan back and forth looking for the data your computer wants. SSDs (*solid-state* drives) instead operate a lot like a USB drive in that they have no moving parts and are much, much faster as a result."
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dd0xtj | How are old movies released in 4k/UHD? | Technology | explainlikeimfive | {
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"text": [
"Many movies can be re-released using the original film, which I much higher quality than the releases from 1993"
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dd2o02 | why does hitting the remote control when it doesn't work suddenly make it work? | Technology | explainlikeimfive | {
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"text": [
"A lot of times the remote doesn't work because a speck of dirt, dust, or corrosion gets between the battery and the connector, robbing the remote of power. Hitting the remote, or popping open the battery compartment and spinning the batteries within the compartment, often jars the dirt loose, restoring power to the remote's electronics."
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dd3ij9 | How do colorblindness glasses work? | Technology | explainlikeimfive | {
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"text": [
"Colourblindness happens when a colour rod in the eye doesn't work or the message from the rod to the brain doesn't work. You have three rods (yellow blue red) and each activate at different levels when light passes them. This is what creates imagery in our minds. All colours we see are a makeup of these three rods being stimulated. When one doesn't work it can moderately be replaced by glasses that change the way light enters the eye because light is made up of colour, by alternating the stimulation of the remaining rods you can create a new colour spectrum for the person to see. Kinda like dumping extra yellow into the mix if you're out of red paint"
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dd4g1j | How does a speaker know what sound to produce from a series of 1 and 0s? | I understand that there is magnet and it vibrates to the current. But how does it actually convert? | Technology | explainlikeimfive | {
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"Great question! They don't. Speakers are analog devices, meaning we cannot supply them with the digital 1 or 0. What we use is a Digital to Analog Converter (DAC) to change our Computer's digital signal into an analogue signal that can be played. This brings up a bunch of other issues like quantization levels and digital filtering though which is a little outside the scope of ELI5",
"It doesnt. And audio program converts the audio file into a sort of rough wave form by sampling. Imagine you draw a sound wave as a sinewave. An analog sound has infinite steps in a sine wave. Since that is hard for computers to do, it measures the height of the wave. How many times the wave is measured determines the audio quality. This is also called sampling rate. The output is a reconstructed sine wave. This is an alternating current. When the current passes through the spool in the speaker it gets a magnetic field. Because the spool is next to a magnet it either gets attracted or pushed away. When the current changes direction the magnetic poles of the spool change sides. This creates a vibrating Motion in the spool, which we hear as sound.",
"Digital signals indicate the level of a signal with binary numbers (0s and 1s) in discreet points in time. Speakers on the other hand are analog devices. The following picture illustrates how analog (1 diagram) signal is converted to digital (2) and then back to analog signal (3). The issue is that when converting digital signal to analog the result is very blocky (3). We use filters that smooth them out and the result (4) is almost identical to the original signal. URL_0 EDIT: How does Digital-to-Analog-Converter (DAC) work? Each 1 and 0 indicates how much voltage must be added together. E.g. 11111111 indicates that the voltage will be maximum. 00000000 indicates that the voltage will be minimum. 00001111 indicates that the voltage will be half of the maximum. In binary code bits go from the most significant bit (MSB) to the least significant bit (LSB). MSB- > 00101010 < -LSB In an electronic circuit these bits indicate which latches should be open and latches send different amounts of voltage to be summed up in the result. Say the maximum voltage is 255, then Bits: 0 0 1 0 1 0 1 0 Volts: 128 64 32 16 8 4 2 1 Result: 32 8 2 = 42 The circuit will add only those volts that correspond to 1s in our code. The result will be 42 volts."
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dd7gzr | Why is it so easy to get the type of results I expected from a Google search for say, restaurants - but so difficult to get concisely relevant results from a search for doctors? | Technology | explainlikeimfive | {
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"1. Restaurants are (mostly) uniquely named and have distinct locations. Doctors do not have unique names, so can be hard to search for like any other non-famous person on the internet. 2. Restaurants use search engine optimization (SEO) and often submit themselves manually to Google for inclusion. Doctors are an occupation and not a business, so do not do this. 3. I don't know how it is in other countries, but in the US you generally cannot just go see any doctor you want. Even if you have awesome insurance, they need to be in your network, so it wouldn't be helpful for a list of all \\_\\_\\_\\_\\_ (orthopedic surgeons or whatever) to be displayed to you in search results. 4. Restaurants always want customers. Doctors do not always want new patients. 5. Doctors are generally employees of a practice/hospital, so the real search results would be the location/business, not the doctor. If you were looking for a roofer, you couldn't get a list of employees from local contractors, you would get business names."
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dd8amz | - why the number key pad on a keyboard or calculator is laid differently than on a phone. | Technology | explainlikeimfive | {
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"They were essentially derived independently. Modern computers are essentially extensions of preexisting more \"manual\" computing devices, such as adding machines, which had established keypads with 1-2-3 on the bottom. Lower numbers are more frequent than larger numbers (especially 1's and 0's), so having those numbers at the bottom near where your fingers are is better. And this pattern has been maintained as these manual machines were replaced with electronic equivalents and through to general purpose computers. When phones were deciding to incorporate keypads, they did user research and testing to come up with a design, and the pad with the numbers at the top won out. No one can really say why they didn't just copy the numbers from existing adding machines and such but it's possible that those machines were considered specialist machines while the phone was intended for a general-purpose audience. Or they just didn't think about it. It wouldn't be the first time we've [we've reinvented the wheel.]( URL_0 )"
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dd8eqf | What can someone do if they have your IP address? Can they see all your internet activity and places you've posted? Can they identify who you are? | Technology | explainlikeimfive | {
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"If they *only* had your actual IP address, they could DDOS you and potentially locate you within a rough geographic area. But that's about it. If they had your IP but also purchased or collected date from cookies and such, they could learn a lot more.",
"This all depends on how sophisticated the party with your IP address is. Having the IP address just is that, an IP address. You can do a lot with it, depending on how sophisticated you are, your connections, access, and resources. It could also be completely meaningless to someone without the knowledge or resources to use it. The NSA could try to track you, setup 24/7 spy surveillance, hack your ISP, sneak into your house when you're gone, yadda yadda. Joe bluejeans can probably see roughly what city the IP address is registered to (which may or may not be your city), which ISP its registered, and not much more interesting than that, other than maybe trying some token DDOS attacks, but they probably won't be successful without a lot of resources."
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ddcwph | How does a company just “shut off the internet” within its borders? | Technology | explainlikeimfive | {
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"A country you mean? Into and out of every country there are surprisingly only a few high bandwidth fiber optic cables. These are used for everything: phone, cell/wireless, internet data you name it (everything gets converted to IP packet switched behind the scenes nowadays anyway). These lines and the junction point/switches and routers where they break out into smaller connections to go the last mile to your house or work are consolidated in one or two data centers at the telcos in your country. Not only that, but usually just one or two telcos actually went and laid the cables, the others in your country just lease bandwidth from those. So when President Junta decides to cut off Facebook because the Rebels posted a picture of him having sexual relations with a burro, the head of the police just has to call one or two telcos and say \"Cut off the internet or we cut off your head.\"... from there, the folks in the network operations center really just have to click a few clicks to disable the links with the outside world. Example: this is the [worldwide submarine cable map.]( URL_0 ) These are the fiber optic cables that run along the sea floor and connect countries via the oceans. Zoom in - quite a few countries are only connected to one, or two of these massive internet backbone/telecommunications cables. Literally if you were to know where to look, there'd be a thickly sheilded cable running up out of the ocean and up the beach to a little shack with a bunch of network gear in it (its a little more complicated than that, but not by much.)... There are terrestrial and satellite links too, but the principal is the same: its expensive to set these international internet/telecom cables up, so they're done surprisingly infrequently. Thanks to the wonder of switched internet packet protocols, if one link goes down (some idiot with a back-hoe), traffic will re-route to another available connection, but its always possible to disconnect an entire country's set of internet connections. edit: and by disable links, usually nothing gets unplugged. All you have to do is disable the routing protocols that allow data traffic to flow in/out of the country.",
"I work in telecom. To shut off say... Alaska. All you’d need to do is unplug 4 cables. It’s really scary to think about considering how vulnerable a lot of places would be without communications.",
"Internet traffic is more like myriads of children running along the paths and through the gates, not like the freely flowing water in the river. You just close the gates and kids stay in, and no kids from the other side can get through either. Sure, it's much more nuanced than that, but ELI5 it's like this.",
"for how decentralised internet is to the end user, it is surprisingly held up by only a few cables. no point in building more. hence, you can cut off access quick and easy if you have the resources of a major world government. i don't know how exactly the ban you are inferring to happened or what it was, but i know that most UK bans on websites ( URL_0 etc.) are just mandates from the government to local DNS services (and ones big enough that they have to bend over backwards) to stop properly indexing said bad websites. they're insanely easy to circumvent.",
"ELI5 (niece practice): The stuff you see on the Internet move around the world by wires, mostly. The wires are controlled by electronics that people control. To \"shut off the Internet\" somewhere, these people just have to use the electronics so the wires in these areas stop working. Now stuff from the rest of the world can't use these wires to move Internet information into these areas because they're not working anymore.",
"Every communication on the internet from point A to point B goes through several nodes before reaching its destination. The path (in term of nodes to traverse) to use is decided by algorithms called Routing algorithms. A governments can decide to tweak these routing algorithms on every node of the internet residing on its territory (i.e. nodes used by its citizens) to make any destination on the internet unreachable (or limit the capability of its nodes to allow only national websites)"
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ddhhol | How did humans deal with cavities before dental care became more mainstream? | Technology | explainlikeimfive | {
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"The only option was to pull out the offending tooth. And with little in the way of painkiller. However, it's worth noting that tooth decay was less common prior to the Early Modern Period (before the 16th century) because there was less refined sugar in the average person's diet.",
"A big part of it is a better diet which prevented cavities from happening in the first place. A lot of tooth decay is a result of a diet containing processed foods especially with a lot of added sugar, sugary drinks, candy in general and hard candy in particular. Bathing the teeth in sugar all the time is a great way to promote the growth of bacteria there. A diet high in unprocessed plants means less sugar for bacterial to thrive on but also consuming a lot more fiber which helps to clean the teeth. Also, modern fruits have been bred to be a lot bigger, sweeter, and juicier. If I remember correctly, carbonated drinks don't help either because when carbon dioxide dissolves in water, it becomes a bit acidic. And people would use twigs and the like to clean their teeth."
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ddmzq4 | Why do different image compression / viewing formats exist and why can't we have a standard format ? are there significant advantages/ specific use cases to some over others ? | Technology | explainlikeimfive | {
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"[Relevant xkcd]( URL_0 ) Today there are effectively three standards - JPEG, PNG and SVG, and each has its purpose. JPEG uses a lossy compression, meaning that some details of the original image are lost. It is mainly useful for naturally created images (eg photographs) because this loss of detail is unnoticeable and because it is optimized for the natural transitions in the image. PNG (and its predecessor GIF) uses lossless compression. It is useful for when you want to preserve all the details, for example for digitally created images and diagrams. SVG is a vector image format. Unlike other image formats which store an array of pixels, vector images store simple objects - points, lines, squares, circles, and such. The advantage is that they are easily scalable (ie you can zoom in as much as you want). This is useful for things like graphs/diagrams and company logos.",
"What we have today is an evolution of formats where each tries to improve on the past. These, I believe in chronological order, include the following: Bitmap (.bmp) - The full fidelity image where each individual pixel is represented by its color code in an array. These are very large an inefficient and therefore seldom used today. Graphics Interchange Format (.gif) - This format tried to improve the size inefficiencies by compressing the data and restricting the number of colors allowable. The beginning image would be processed down to only 256 colors. It also included the ability to support simple animation by stacking an array of compressed images where each subsequent image was stored as the difference from the previous image. Transparency was also an important benefit of this format. Portable Network Graphic (.png) - Between the visual artifacts caused by high compression and eventually copyright issues with the .gif format, PNG was developed that used much more advanced compression techniques to eliminate the visual degradation of GIF files and also support transparency. This is the most popular image format today. Other formats exist, but these three are the primary formats that were most often used. Source : Recovering software developer and general nerd.",
"Shortly: different compression algorithms were developed by different teams, having different copy/usage rights. Being proprietary they were or were not allowed for specific use and/or were allowed under certain restrictions, that some people didn’t want to accept/follow. In time new algorithms were invented, but old formats became so strong (eg. thanks to internet) that it will take time to replace them. Or even won’t happen. Yes, they have specific usage. For example: Jp(e)g - photos, where having the most details and good compression counts. Compression can have different levels thus providing different details (quality, file size). Png 24 bit - could possibly replace jpg Gif - where image doesn’t need many colors (max 256) and/or requires transparency (eg. icons on websites). Also can contain simple animations Png 8 bit - replacing gif except animations And others less popular at the moment or used not on the internet."
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ddni0p | How do pc gamers have an unfair advantage over console players when playing the same game using a mouse and keyboard over a controller ? | Technology | explainlikeimfive | {
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"It's substantially easier to input precise movements with a mouse than with an analogue stick. So much so that PC games usually will not have aim assist enabled by default if it's even available in the game. If you think about how much travel there is in an analogue stick compared to the area you have to move a mouse, you can probably imagine it would be much easier to make fine adjustments with a mouse. In FPS titles and such it could be seen as an unfair advantage as the mouse facilitates greater accuracy with equally skilled players compared to their console playing counterparts.",
"A mouse allows the player to make both huge and very small movements rapidly and accurately. Compared to the turn rate of a thumbstick on a console controller, it is more flexible, and faster, which is a huge deal in most games. A player on a controller will usually not be able to turn around or line up shots as fast or precisely as a mouse user. On top of this, most games have more functions than you have buttons on a controller. A keyboard user can map a LOT of quick commands, and input combinations to the keys on a keyboard, while a controller user might be stuck having to navigate an in-game menu. As an example, a player with a mouse button with 7 buttons (2 normal, clicking the scroll wheel, rolling it up, rolling it down+ the back/forward buttons on a fairly normal mouse) 3 keybinds on buttons for the left hand index finger above/to the right of the movement keys (wasd) and the pinky finger for shift, and the thumb for space is using a LOT of keys while barely moving their hands. If the game allows modifiers (like shift or alt+ the normal buttons) to have separate key binds, you are looking at 9-27 different commands without even using the numbered keys or the rest of the keyboard.",
"Mouse and keyboard provide much more precise controls. Broadly speaking, the humans are not very precise. Let's say we're accurate to within a sixteenth of an inch. On a gamepad, 1/16th of an inch is probably about 5-10% of the total range of movement. On a mouse, 1/16th of an inch is closer to maybe 2% of the total range of movement. Using my estimated figures, this makes a mouse about 250% to 500% as accurate as a gamepad.",
"I play on both PC and console. On Keyboard you can map a lot more buttons to important functions in a given game than you can with a controller, you can get close with a controller if you have something like a Scuff pad which have extra mappable paddles. With the mouse, it's point and click; feels more natural and is typically easier to get better with. You can also have more mappable (doubting if this is an actual word now) buttons depending on the mouse. Console players are locked to certain amount of frames (30-60) while with PC, depending on the build, you can exceed 60 with a lot of games. Low to mid end PC's are arguably more stable at 60 fps than the higher end consoles. In my personal opinion, controller is a lot more difficult to learn for first timers than playing with keyboard and mouse.",
"Controllers are fantastic for games that require timing and press sensitivity, like fighting, sports, and driving games, but suck at games that require precise spacial movement like turning around and aiming, they're so bad at it, that most shooting games use aim-assistance to make up for that. Besides shooters, there's really not much advantage for mouse over controller. IMO the real advantage of PC gaming over Console is the hardware limitation, a PC gamer can go overkill in specs, higher resolution and bitrate does change drastically how you game."
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ddoy9v | growing up I was taught to never bring a magnet near a TV/Computer screen. Now we have phone cases and accessories that are magnetic. How is the phone not damaged by this? | Technology | explainlikeimfive | {
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"In CRT TVs electrons are fired through the TV, hitting magnets, and then giving you your display. A strong enough magnet can actually warp the polarity of some of the internal magnets, messing up that part of the screen. Nowadays, we don't use that technology anymore. Also, the magnets on accessories are pretty weak. I worked at Walmart and we had a pretty strong bar magnet; I could make my phone screen scroll with it, but no distortion.",
"The televisions you grew up with used a Cathode Ray Tube (CRT) as the technology that displayed images on the screen. CRTs use magnetic fields to control how the image would light up on the screen, and this meant they were sensitive to other magnetic fields nearby, like the magnet you held in your hand. Telephones and tablets and laptop computers (and most modern flat-screen televisions) use a different technology for displaying images on their screens. They use a Liquid Crystal Display (LCD) or Organic Light-Emitting Diode (OLED) screen, which is not sensitive to nearby magnetic fields. I can explain in more detail how the CRT uses magnetic fields to create the image, but I wasn't sure you were interested in that level of detail.",
"Use to repair CRT-type televisions many years ago. While a strong magnet can cause the CRT's control electromagnets' fields to warp and cause the picture to be distorted, that's not the real problem (since it's temporary). The real problem happens because when you hold a magnet up to a CRT screen, you can induce a permanent magnetic field in the screen itself because of the metallic phosphors that make the screen glow (the picture you see) when electrons hit it. This would make a semi-permanent change in the screen itself that didn't go away when you moved the magnet away. We had a special coil we used in the shop called a \"degausser\" that was used to clear residual magnetism from the screen. I was always surprised to see how many TV screens had distortions in the picture because of this problem. The degausser got used a lot."
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ddrjme | on game controllers, why is it called *analog* stick but *digital* pad (d-pad)? Aren't all inputs digital? | Technology | explainlikeimfive | {
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"It is digital because the inputs are discrete. You can do UP or LEFT or RIGHT or DOWN. Nothing in between. The stick is analog because you have a continuous range of motion (even if it is broken down into discrete elements on the electronic and programming side).",
"Yes, it's all digital, but \"D-pad\", means direction-pad, as opposed to the joy-stick controller that it was introduced to compete with (think NES vs. Atari)."
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ddrq3n | Why do LCD displays cause headaches and eye strain, while OLED displays do not/take way longer? | Technology | explainlikeimfive | {
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"The LCD display has a backlight, and a filter which changes to colour the pixels a certain way, whereas an OLED has pixels that generate their own light. Lets say you're looking at reddit in Dark mode. On an LCD, the backlight is still having to push light out, and the filter is trying its best to block said light, to make it look black. the net result is a gray colour background, and white light potentially bleeding through the edges. Since the OLED only puts out light where necessary, the pixels actually dont put out any light to make the colour black. the net result is that your eyes absorb a lot less light, which can help reduce headaches. Likewise since the black is actually black, there's a lot better contrast than on an LCD screen. a better contrast makes text 'pop' a lot better, meaning your eyes work a lot less to read text.",
"Do they though ? I've never gotten a headache or any other issue from any screen I've ever used."
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dduy3d | Why do some VHS tapes have fucked up bottoms like this? | Technology | explainlikeimfive | {
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"One thing that can cause this is the playback head being out of alignment. You can try adjusting tracking.",
"Every frame of a video is recorded as a diagonal line over the width of the tape, be it VHS or Betamax. This diagonal angle matches with the diagonal position of the flying head in the players if you have seen the internals of one. Now if your VHS tape, for some reason, has a scratch somewhere, it will show as a messed up line on the screen. And if that scratch runs along the tape for a while or the whole tape, then it will show on that part or the whole of the video. The scratch position of the tape determines where the messed up line on the video shows up. If you still have a VHS player and a spare cassette you can play with, you can try creasing some part of the tape and playing to see the effect. Hope this helps. Lesson to learn - don’t touch or play with the tape inside a VHS cassette.",
"Additionally, when VHS was common, televisions did not typically show the ENTIRE image. The edges were overscanned so you would not see them. This was partially due to inexact nature of CRT displays. These days with LCDs and other such displays, you can sometimes see a line of noise at the top of bottom of the screen on older recordings. On test patterns you will often see boxes a certain amount in from the outermost edge: 3%, 5%, 10% or similar. These are for \"action safe\" and \"title safe\" overscan amounts. e.g. the main action must stay 5% away from the edge because it might get cut off, and any text must stay 10% away."
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ddv5o7 | How did it come to be that gold and silver are considered valuable and even have been used as currency while so many other metals never did? Couldn’t it have been nickel and aluminum instead? | Technology | explainlikeimfive | {
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"In ancient times, gold and silver could be found in almost pure veins. You dug it out, you had lumps of gold or silver you could work. Aluminum requires smelting 4 kilos of bauxite ore to obtain 1 kilo of aluminum oxide, which then requires more processing to become pure aluminum. Pretty much the same for nickel, it requires processing ore to obtain.",
"well, aluminum particularly is hard to mine and refine, it wasn't extracted until the 1800s. Similarly, nickel wasn't recognized as an element until the mid 1700s. There's a couple things that make gold and silver common as currency. They're relatively rare, they're pretty chemically inert and nonreactive (gold moreso). They're also soft and easy to shape. The chemically inert and non reactive are pretty important. it's pretty common for metals to be found in chemical compounds (such as oxides) rather than just by itself. This means that a lot of other metals need to be processed before they can be used. And then they're harder to shape.",
"Aluminum used to be considered extremely valuable. So much so that the cap of the Washington Monument is aluminum as it was more valuable than gold at the time. It was generally used for jewelry. It was the development of the Bayer process in 1887 that made aluminum production inexpensive. So while gold is expensive because it is scare, aluminum was expensive because it was expensive to produce. The reason why there is so much control over the production of synthetic diamonds is because it moves diamonds from the former scarce category to the latter production category and therefore open to cheap production.",
"I can't speak as to silver, but gold is a natural for being considered valuable. It's relatively rare, it's extremely malleable and it never ever ever ever loses its shine or tarnishes in any way. Combine all three and you have a metal that's perfect for jewelry and coinage. It'll never deteriorate, it'll never be common and you can easily turn it into jewelry, or melt it down to remake into new coins as needed.",
"Aluminum was not easy to refine until the 1800s. So economies were pretty well established by that point in time. Nickle has been used for currency. That is why the American 5 cent coin is called a \"Nickle\" as there was a period of time when it was made of nickle. The half dime was the equivalent coin but made in silver. Use of silver, gold, copper, and alloys involving one or more of those metals such as brass, bronze, or electrum have also been in use for a long time as they are relatively easy to refine, durable, and rare but not impossible to collect.",
"There are a couple of key factors. 1. Availability and refining: ease of access to gold ore (scattered all over the world near the surface), ease of identification (it looks gold), and ease of refining (just melt it at relatively low temperature and the gold comes out) makes gold a prime candidate. Compare that to aluminum, which is hard to identify (blue grey) and notoriously difficult to refine, and you have a good pre-industrial metal. But what sets it apart from other metals like iron and copper? 2. Nobility: silver and gold are noble metals, which means they don’t rust or appreciably tarnish, which makes them ideal for coins that are gonna be carried around for a long time in all kinds of conditions. And finally, the most important, 3. Shiny! Gold and silver are reflective, pretty colors that don’t lose their shiny easily (see point 2) I didn’t research this, so feel free to correct me all you like"
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ddxkh8 | What are neural networks and how do they work? | Technology | explainlikeimfive | {
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"First; computers simulate them. They are not (yet) a physical thing, but merely a type of program that computers can run. Now: Neural networks are arrangements of nodes which are connected. Each node takes one or more inputs and gives one or more outputs. Now, a *lot* of these nodes are chained together in a network, where different ones output into each other's inputs. That is the premise of a neural network. By constantly rearranging the connections between these nodes, and functions of each node, we can find arrangements that do what we want. There are a multitude of approaches for how to do this, and I'm not really going to get into that. The interesting thing about neural networks is that they are good at handling organic and difficult-to-describe-in-words data; this is something that standard [if,then] programming has a lot of trouble with. The downside is that, once a complex network has been 'trained', nobody really understands how it works because the arrangement of the nodes has been generated and optimized by statistics and computers without the direct help of people.",
"Hope that's not against the rules, but there is a great video on neural networks: URL_0"
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ddz92f | How are computer languages created? | Technology | explainlikeimfive | {
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"You don't create a programming language. You create a compiler. By defining how your compiler reads in text files and converts them to an application, you indirectly define the syntax needed in those text files needed to accomplish certain tasks. That syntax is all a programming language really is.",
"Computer languages are really just a system of rules. You can create a computer language in your mind right now if you want to. Just create some rules for creating variables, making loops and functions, conditionals, classes etc.. Of course to make the language practical, you need to write a program that can transform a text file which contains text that conforms to the rules you created into machine code that will be understood by the computer. Thats what we call the compiler or interpreter. If you ask how do you create a compiler, then the answer is its just a program like any other program. You create it with another existing language like python or c++ or whatever is your favorite. If you ask how was the first compiler created, then the answer is it was written in machine code. machine code doesnt need compilers because computers already understand it. They understand it because their circuitry is hard wired to understand it."
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de0veb | Why is 2.4Ghz Wifi NOT hard-limited to channels 1, 6 and 11? Wifi interference from overlapping adjacent channels is worse than same channel interference. Channels 1, 6, and 11 are the only ones that don't overlap with each other. Shouldn't all modems be only allowed to use 1, 6 or 11? | Edit: Wireless Access Points, not Modems I read some time ago that overlapping interference is a lot worse so all modems should use either 1, 6, or 11. But I see a lot of modems in my neighbourhood using all the channels from 1-11, causing an overlapping nightmare. Why do modem manufacturers allow overlapping to happen in the first place? Edit: To clarify my question, some countries allow use of all channels and some don't. This means some countries' optimal channels are 1, 5, 9, 13, while other countries' optimal channels are 1, 6, 11. Whichever the case, in those specific countries, all modems manufactured should be hard limited to use those optimal channels only. But modems can use any channel and cause overlapping interference. I just don't understand why modems manufacturers allow overlapping to happen in the first place. The manufacturers, of all people, should know that overlapping is worse than same channel interference... To add a scenario, in a street of houses closely placed, it would be ideal for modems to use 1, 6, 11. So the first house on the street use channel 1, second house over use channel 6, next house over use channel 11, next house use channel 1, and so on. But somewhere in between house channel 1 and 6, someone uses channel 3. This introduces overlapping interference for all the 3 houses that use channels 1, 3, 6. In this case, the modem manufacturer should hard limit the modems to only use 1, 6, 11 to prevent this overlapping to happen in the first place. But they are manufactured to be able to use any channel and cause the overlap to happen. Why? This is what I am most confused about. | Technology | explainlikeimfive | {
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"Can someone explain this question like I'm five?",
"Because in much of the world world, you should be using 1, 5, 9 and 13, to get 4 non overlapping options. The 1-6-11 is used because of the U.S. refuses to allow use of channel 13, or, in Japan, to allow channel 14 to be fully non-overlapping. In addition, there are uses for half-overlapping channels. When a large area needs to be covered, you have 3 non-overlapping channels nearby, and further away you use half-overlapping channels, where the weak overlapping signals won't cause as great a problem.",
"All these answers and not a single person has stumbled on the correct one: Hindsight is 20/20. Remember that when the standard was settled upon, the designers had absolutely no idea how ubiquitous WiFi would become. It would be approximately another ten years before WiFi routers would even start to become household appliances. Zip drives were state-of-the-art, laptop thickness was measured in _inches_, and the concept of a smartphone was about a decade away from public consciousness. People rented VHS cassettes to watch movies at home on their rear-projection TVs, and HD television was for the idle rich. Netflix had just started mailing people DVDs via The Postal Service. Okay, I'm getting a little carried away describing the world of the late 90s, but it's important to remember the designers of the 802.11 standards had to make choices in a world where households rich enough to even have internet access connected to the internet via dialup. No one even conceptualized a world where routers would be so cheap that every single tenant in an apartment building would have their own radio transmitter sitting in a closet gathering dust out of sight, out of mind. Many of the choices they made for the standard naturally assumed wireless internet access would only really be deployed by professional network admins who would have control of all the other routers in range. Why not let them choose any channel?",
"Almost touches on the idea of a prisoner's dilemma -like situation. The standard allows the choice of any channel in the range to best suit the user's wishes. But let's just say everyone sticks to 1/6/11 and those three bands are heavily congested. Anyone setting up a new radio in a congested area will find a LOT of interference centered around each of those three channels. Someone else gets tired and decides that to avoid interference he should select something in the middle of the overlapping bands like channel 3. And suddenly now you have someone who has a relatively clear channel, but now 1 and 6 have some interference from another channel in addition to everyone else already on 1/6.",
"Other WiFi devices aren't the only thing that you might need to work around, it could be other 2.4ghz devices as well as environmental factors.",
"because with channels 1, 5, 9, 13 you get 4 non overlapping channels. not all countries allow all channels.",
"Because that isn't how wireless signal works. URL_0 The farther you are from the center of another network's broadcast, the less noise that network causes. If you have 9 networks in range, you will do better with partial overlaps on 4 of the other networks, than you will with complete overlap with 2 other networks.",
"Two reasons: edge cases where it does make sense to deploy on one of the normally overlapping channels (think single AP deployments in odd RF environments), or other countries where you’re allowed to go up to channel 13.",
"Cause number 1: Freedom. Number 2: FCC actually had a rule saying you can only use 1,6, and 11. But no one had to follow it, and it's left open to use whatever channel you want because there is/was anticipation to use wider band channels (40mhz over 20mhz for OFDM). Which you can see in the wild if you have a scanning tool. If you're curious, you can get Alfa Wifi Scanner software and take a look at the different channels are being used in your area and what their bandwidth is. From that, you can also choose a better channel for you personal device. This is a really smart question for a five year old.",
"Also why the hell when I choose auto channel selection the router chooses the WORST channel and basically never chooses 1,6,11?",
"You should not assume that Wifi is the only thing using these channels. From garage-door openers to (analog) AV-bridges and even your trusty microwave-oven, all kind of devices use this frequency spectrum. I have experienced how an AV bridge (to wirelessly transfer a TV picture from one room to another) could block out the whole middle-section of the available Wifi spectrum, only leaving a bit of breathing space at the top and bottom ends for all 20+ Wifi-networks in a multi-apartment building... (of course, that was totally not *my* device and I absolutely did *not* have to keep it running 24/7 to make sure other devices don't enter this frequencies and cause disturbances for my TV watching pleasure …) In any case: the more flexibility there is in how the channels can be assigned, the better for the quality of service. Today's Wifi devices are pretty smart when it comes to choosing the right channel even under very adverse conditions, so nothing to worry here. (Don't buy analog AV bridges though. Seriously, they only transfer SD resolution and are a pain for everybody. Use a cable instead)",
"I know it's just semantics but you're referring to wireless access points (WAP). Not all modems perform as routers and access points.",
"so if i enable only those channels i will benefit from it because other people use the standard settings ? if so, how do i do that ? thanks",
"The decision to restrict 802.11 to a 72Hz range was a stupid one to begin with. The overlapping channels thing is a mitigation of that. I can imagine the standard changing to what you described, and it would help for some people but it's just mitigation on top of mitigation of a screw-up that needs to be fixed directly. Also, restricting to those three channels reduces flexibility for people who need to fine-tune things to avoid interference from things other than WiFi.",
"Typically co-channel interference is preferable to adjacent Channel interference. With a big exception. Imagine you're at a big family reunion. I'm talking massive. Like Great Grandpa got back from the war and had 20 kids between 3 wives. And each of those kids and theirs kept up the tradition. Now what if they lived in a country with an awesome medical system that guaranteed a long life span and everyone showed up to the family reunion. Now the event planner(cause 804 people goddamn) came up with 3 incredibly long tables. And to keep things organized each table had 1 golden token. Whoever held the golden token could talk 1 thing and could take as long as they needed. -This is how WiFi routers handle co-channel interference. Any router within range(above -80db signal strength) and on the same channel would recognize each other and pass a token to decide who is talking. For most it was fine they would get the token and would say rather mundane things like,\"pass the salt\". But Great Grandpa that glorious mothertrucker would share his war stories and everyone else would be stuck until he was done or forget what he was talking about. - So not only do you have a whole lot of people waiting to talk but Grandpa takes extra time when it's his turn. When you have an apartment complex with everyone on those same channels, everyone ends up waiting. Since 2.4ghz is the oldest standard, you could have computers upto 20 years old trying to use the same channels and they take a long time when it's their turn. Now some people get a little impatient and get up and stand between the tables to hold their own conversations. It makes it a little noisier but it speeds up conversation at the main tables and people can catch up. -This is were adjacent channels are useful. It makes it a little noisier as they're talking over the other channels but it allows the different routers put more tokens in play. It makes the error correction have to work a little harder but data is passed faster. Now if too many people get up it descends into chaos and nobody can hear anyone. So your busy body aunty starts going to these little groups and tells them to sit down. Now you figure instead of sitting at the same table as Grandpa you'll swap tables. -You're experiencing bad WiFi because everyone has set custom channels so you call your ISP. The ISP sends out a Tech and they factory reset your router and it defaults back to 1,6, or 11. They tell you next time it gets slow to reboot it again. This forces your router to jump to the least congested of 1,6, or 11. It's getting a little late and the bar opens up so all the 20-30 somethings jump over there. There's a whole lot of small tables and conversations are going smooth. -5ghz has now come into play. Whole lot more channels and the devices aren't nearly as old. Less congestion and better bandwidth. Now an alternative to jumping channels would be what I call the \"good neighbor policy\". Every router in an apartment complex cuts their transmission strength to 65%. This way the routers don't see as many networks and reduces the number that share the token. The problem with this is twofold. 1. Everyone has to be in on this, so all the ISPs and customers on site have to agree to reduce their signal strength. 2. Large apartment buildings have a lot of concrete. Concrete kills WiFi, and if you're reducing your transmission strength, you're increasing the likelihood of dead spots in your WiFi. When it comes to WiFi there's no winning.",
"The real answer is that the ISM band where wifi operates existed long before wifi existed. The band was split into narrow channels suitable for the various equipment used in it at the time. Wifi needed wider channels. Wifi channel 6 is centered on ISM channel 6, but occupies ISM channels 4 through 8. The three wifi channels fully occupy the US ISM band. Different countries have different ISM bands. The channels line up across countries, but the top and bottom channels are not the same. The wifi scheme in these other countries centers on different channels, with the intention of fully using the available band. The final piece of the puzzle is that manufacturers want to produce one device to serve multiple markets. Which means they have to be able to operate on that market's scheme.",
"I believe it has to do with WiFi using a spectrum band that is known as ISM, or \"Industrial, Scientific, and Medicine\". It is unlicensed so it costs no money to use it (unlike frequencies for Cellular use for band example). The caveat is that it limits significantly the power you can transmit, an if you chose to use it then you must be ok to the presence of other users there (since it's unlicensed). Basically the FCC left these bands for users to behave nice - you can use it for certain applications that don't need to send data very far, or for research, but act nicely; don't try to overpower anyone else nearby and don't whine if someone interferes with your signal within reason. These rules were written before WiFi ever existed, and wifi operators started using these frequencies too; they're so prevalent now that the band is occupied heavily and you experience interference.",
"I'll answer with a quick question. Imagine the bandwidth loss and lag if alll of those channels were bottlenecked further to just a single set of streams rather than multiple outlets? At least with multiple channels, while there is interference the amount of options available can pick up the slack.",
"A modem is a device that converts analog signals to digital, and vice versa. APs are not modems. Switches are not modems. Routers are not modems. Hubs are not modems. Not all Router APs that have coax are modems. Sorry if I come of a dick but stop saying that. Op your analysis is essentially correct, the extra channels exist for 2 cases. One, you live isolated and can use wider bandwidth (20MHz/40MHz/80MHz/160MHz). The other case is for countries where some of the spectrum is already used. The channels available in other countries vary. For legal reasons, APs have different firmwares in other countries to avoid causing interference on gov spectrum. Japan is the only country with Channel 12 and only for 802.12b. You can use custom firmware to use illegal channels if you are isolated enough to not cause issues. In the US you can broadcast 200ft on gov bands if you want.",
"I’ll add here that modems (as they’re used in the Internet access sense) are not WiFi devices (however, WiFi must necessarily have modulation and demodulation as part of the signal path). The box your ISP provided that you’re referring to as a modem is actually several devices inside a single box: the modem that connects to your ISP’s circuit allows interfacing between the ISP’s circuit and the router, as they have different physical layer connections. The router operates at the network layer and its job is to move Internet traffic between your network and your ISP’s network. The router then connects to an Ethernet switch, which is the foundation of your local area network, or LAN. In addition to a couple of internal ports for the router and the access point (more on that in a second), it also usually has a handful of external ports to connect various network devices. Then you have your Wi-Fi Access Point - this acts as a bridge that translates the data link layer between Wi-Fi and Ethernet. In a wireless network, the “physical” layer consists of radio waves (I know, they don’t seem very physical, but physics play a huge part here). Networking is generally referred to in “layers” like a burrito. A theoretical model is the ISO model, which is 7 layers. The TCP/IP model is more practical and consists of 4 layers. Each layer fits inside the data payload of the layer below it. The Physical Layer (1) consists of bits - 1s and 0s. This can be electrical signals on a wire, electromagnetic radio waves (wireless), or electromagnetic pulses of light (optical). This could even be smoke signals or acoustic waves if you got crazy enough. This is the tortilla - it holds the burrito together. The Data Link Layer (2) adds structure to those 1s and 0s by defining how a link carries data. This can be Ethernet, Bluetooth, Wi-Fi, or a variety of other ways of transporting data. layers 1/2 in the ISO model correspond to the single Network Access layer in the TCP/IP model. The Network layer (3) is where interesting stuff starts to happen - this defines specific ways devices on the network talk to each other. This is where IP lives. TCP/IP calls this the Internet Layer. layers 4-7 deal with the actual user data being sent over the network. This is stuff like HTTP and all the other stuff you do on the internet. TCP/IP model calls this the Application Layer. So your internet traffic operates at layer 3, and between you and the server, it goes over a whole variety of layer 1 and layer 2 connections to get there."
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de28fg | how do speakers work? | Technology | explainlikeimfive | {
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"Sound is about pressure waves in air. Anything that pushes air around creates waves. The speaker has a light weight cone attached to a kind of electric motor that moves the cone back and forth. That cone moves the air about, which creates pressure waves in the air - which our ears hear as sound."
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de3vq4 | Since ethernet is so fast and has so much range, why isn't it used everywhere ? | Edit : For wired connections such as videos, or anything that needs a high bandwidth | Technology | explainlikeimfive | {
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"Ethernet has pretty good bandwidth and pretty good speed which is fine for networking but not helpful for many other tasks. Cat6 cable supports 10 Gigabit Ethernet over a distance of 100 meters which seems pretty good until you start comparing it to other standards. HDMI 2.1 will handle 48 Gbps over a much shorter distance, and Display Port 1.4 can do 26 Gbps. These bandwidths are needed for displays as 4k 60 Hz video is a minimum of 12 Gbps and could be higher with HDR. Coax cable was good for cable tv back in the day because while it has less bandwidth than we've squeaked out of ethernet today, it could run for hundreds of meters without a signal booster which was great for running it down streets on telephone poles",
"It's used everywhere in corporate setting when possible. All cubicles and devices like printers and such are hardwired. The places were wireless is used is where fixed wire isn't feasible. Like a inventory scanning device for warehouse. Or a operations management that need to be moving. That's point of wireless. To provide connectivity when you're not fixed at a location",
"It is used everywhere. For Ethernet though, cat5, has about 100m length. Most 802.11 standards support more than enough bandwidth and most of the time the bottle neck isn't if it's a wired or wireless connection..."
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de8244 | Why/how do things still use electricity when they are turned off but plugged in (or just plugged in like a charger not connected to anything)? Where does the electricity go? | Technology | explainlikeimfive | {
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"Engineer here. The short answer is, the electricity turns to heat. Put your hand on a wall wart and it will feel warm. That's where the standby power is going. Now, the reason something like a phone charger still consumes electricity even if it's not charging your phone is because it's not actually off (unless you unplug it from the socket or use a mechanical switch to physically break the electrical connection to the socket). Any time the charger is plugged in, the circuit remains powered up to monitor the output. That way the power starts flowing the instant the phone gets plugged in. A modern phone charger doesn't use much power on standby. Something like 0.1 watts. That's so little you won't even be able to feel that the charger is a fraction of a degree hotter than room temperature while on standby. To put that in context, charging a phone takes 10-11W (a hundred times the power of standby)",
"It depends on the device. Most chargers or small devices these days have a transformer in the plug. This transformer changes the voltage from the larger supply to something more useable. This creates a small amount of heat, and loses efficiency. Every time you change something to something else you lose a little bit. Unless it has an off switch before the transformer, or light, or anything which is physically connected, that little bit of power is lost."
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de9nvl | how does my laptop find so many more WiFi networks than my phone? | Technology | explainlikeimfive | {
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"Your laptop most likely has a better WiFi card and antenna. It's probably more sensitive and can detect weaker WiFi signals. That's all.",
"Laptop wifi antennas usually go around the screen bezel and that way it might have better reception, compared to something that fits inside a smartphone."
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deakq5 | How did people before modern surgery fix broken bones? | Technology | explainlikeimfive | {
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"Splints are a pretty basic technology that has been around a long time. More complex breaks would have just left you crippled",
"For uncomplicated fractures, you don't need surgery even today. You just hold the bone in the proper place and immobilize it with a cast or a splint until it heals on its own. The same was true long ago. More complicated fractures that required surgery just didn't heal and would leave some degree of immobility, and compound fractures (where the bone sticks through the skin) of limbs would result in amputation.",
"To add, modern medicine rarely actually fixes broken bones. Occasionally you'll have procedures like screws and bolts inserted, but most of the time it's just putting the bones back so they're mostly lined up, wrapping it so it doesn't move and let the body heal itself.",
"I was just at the Mütter Museum in Philadelphia and they had a little section about that. Apparently in the late 1800s there was debate as to whether broken bones should have a stable wrap left on for weeks (like a modern cast) or should be unwrapped and re-bound every day. So an interesting period where people weren't quite sure what worked and just tried out both ways until they decided that a longer and more stable wrap seemed to get better results.",
"Not mocking you OP, but I love questions like this. Modern medicine has gotten to the point people just feel like it's always been that way. What did they do? If it was minor, splint is easy and it healed. If it was bad the person was crippled, if it was REALLY bad (think compound fracture) they probably died (maybe from infection, maybe from blood loss). It's like those questions \"what did we do before vaccines?\". They died. Millions upon millions of people died.",
"Depends on the bone. With bones like arms or legs they would just try their best to put the broken bones properly into place again, bandage it with a splint, then hope for the best. In some cases the bones would heal, although often not correctly, while in some other cases they'd get infected or clotted and the person would die or require amputation. With bones such as ribs, hips, and kneecaps which are more complex to fix there wasn't much they could do; a person with a broken rib just had to tough it out from then on, a person with a broken hip was crippled, and a broken knee would likely require amputation. Overall due to the lack of antibiotics and hygiene it was rare for people to survive injuries such as this, even minor ones."
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dedju4 | "Stealth" Drones. How can a drone be "stealthy" if it must be constantly transmitting data in order to be remotely operated? Isn't radio silence a requirement for stealth in the modern battlefield? | Technology | explainlikeimfive | {
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"Radio transmission can be directional. If you put a directional antenna on a drone and direct it to a satellite it would be close to impossible to detect it from below the drone. You might have a chance from a aircraft close and above the drone but that is hard to do Transmission to the drone do not need to be directed to it bout could cover countries or continents and if they are encrypted the would not help in detecting the drone. I would be easier to intercept if you had electronic intelligence satellite in the correct position in space but they are rare and few countries have any.",
"Several ways to do that. The easiest is to not transmit, just program it with \"Follow this path, record everything, then go back home so we can look at it.\". If you need realtime data, you need to transmit. It can be done through very directional antennas. Of course, that is risky, because it's easy to lose contact. It can use fancy techniques such as frequency hopping and burst transmissions. So, they send data in very short bursts, and between each burst, they change frequency according to a secret schedule. This makes it very hard to snoop on or triangulate any locations. ELI5-version would be to compare it to having a shitload of telephones at each end, and use a new phone for every word you send. That would make it very hard for anyone to snoop on, as they don't know which numbers to listen to, and it'll all be very chopped up. Either way, expect heavy encryption and verification protocols.",
"It's very hard to pick up straight em emissions of any kind (radio like you said for example). You don't know the frequencies, polarization, or anything that would help you find the electromagnetic transmissions in the vastness of the spectrum.",
"Theres a concept known as Low Probability of Interception where the radio or radar is made to be hard to be detected. One way is to jump around on different frequencies at a high rate of speed which makes finding the signal hard, another is low power and also irregular transmission lengths. They try to make it look like noise that doesn't seem like a coherent signal",
"Stealth aircraft (planes, drones, etc) means it's \"invisible\" to radar. Through means of material and or design to absorb and or reflect radar. So the radio and or computer signals would not be what makes or breaks an aircraft from being stealthy or not."
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dedx54 | How do Wikipedia pages get written? | Wikipedia is notorious for having unreliable information. But it seems like most of the info is verifiable, and very little is marked in red. Pages are also usually decently written and almost always offer quick and effective summaries on a huge array of topics. Does Wikipedia employ fact-checkers and editors? What is the process of a page being written and finalized? | Technology | explainlikeimfive | {
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"They're written by anyone that wants to write them. There is no approval stamp by an single editor person. Approvals are done by page admins that are volunteers, not wiki staff. Anyone can be a volunteer admin on any topic.",
"The unreliability of Wikipedia is greatly exaggerated. Tests have been made against Encyclopedia Britannica, where they compared a large bunch of articles with the help of some experts. They had the same number of mistakes, but the testers noted that the wikipedia articles were much more detailed and had more content. If you ever find yourself in doubt, check the talk page and the sources. So, how does it work? Well, the idea is that most edits will be benevolent, so if someone does a malovelent edit, it'll soon be fixed, and the general motion will be in the direction of higher quality. To help do this, a wiki saves a history of each edit, so that a bad edit can easily be backed out of. A bad editor can be banned, if need be. The staff/volonteers who manage the site aren't actually editing the content as such, they are more there to make sure form factors, such as language, sources, wiki format and so on is OK, and to make judgement calls on bad edits. So, the ELI5. It's like in society. More people build houses than the number of people who blow houses up. Staff/volonteers enforce building codes."
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def0wx | How can servers let multiple gamers play together in real time? | Gamers can be across the globe yet if you have good enough internet connection you can play with them, see what each other see and do inside the game real-time without delays. | Technology | explainlikeimfive | {
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"There's a lot of very low level detail, but it basically comes down to sharing the workload between the servers and the player's local.machine (the \"client\") and having each connection to the server processed independently of the others so they don't get mixed up. If you're in a game with another person, and they move to the left, the server doesn't send the whole screen. It just sends a message that \"player B moved to the left\" and then your computer processes that instruction and draws the screen for you.",
"There are delays, they're just masked. You always see slightly outdated positions of other players and same goes for you. For other players you are always few metres behind you think you are. That's why sometimes you die behind corners, that's why \"peeker's advantage\" exist etc. It's a massive topic, but too keep it short: what you see on your screen is not what other players see on theirs. It's close, but it's not the same. It matters a lot in fast paced games like Quake for example. There are even examples of players who perform better on LAN than in online matches because of these reasons."
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defjoj | For actual photography, what class of camera's, if any, have smart phones made unnecessary to own ? | Technology | explainlikeimfive | {
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"I would say the most obsolete ones are the [point and shoot]( URL_0 ) segment. They are still better than a phone in some respects -- they have better controls, taking a photo when starting from a powered off camera is hopefully faster, and they have a much higher zoom range, but often a phone is good enough that these things don't matter all that much. A camera you have with you is after all much better than a camera you don't, which means so long it's not impossible to do with the phone, a phone is an adequate replacement. Once you get into the cameras with interchangeable lenses though, those have capabilities that phones don't compare with very well."
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degmkw | how does a file get corrupted? What is it that happens? | Technology | explainlikeimfive | {
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"text": [
"Let's take this analogy: you're making a puzzle. You got the box to show you the image you have to make. You're puzzling and puzzling, everything is going fine. Halfway through someone kicks your puzzle and some of the pieces (this could be any error happening with your pc). Later you want to see the image on the puzzle, only to realize it's not finished. On top of that, you're missing pieces. You could say your puzzle (the file) is corrupted. Now what actually happens is that your pc tries to write a file to your hard drive. If that is being interrupted, it can't write the file in its entirety to the disk, which causes the file to be incomplete and unreadable (thus corrupted). This can also happen while you're updating windows for instance. While it's installing the updates, it asks you not to turn off your pc (because that will disrupt the puzzling process). If your pc does shut down unexpectedly, the updates may not be installed properly, causing your OS (windows) to be corrupted."
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deim70 | Why do empty radio frequency make that sound instead of just being completely silent? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"The universe is very noisy. The sun, every star, all the combined muck our electric and electronics produce, and even the remaining radio echoes from the big bang, make every part of the radio spectrum be full of noise. When you have a channel broadcasting, the signal it broadcasts is louder than the noise, so the signal hides the noise. When there is no signal, your radio turns up the volume in case there is something there. Eventually, the volume (this is called the AGC, if you want to search) is turned up until it is the noise that is loud.",
"* For analog radio equipment, it's difficult to know when a signal is a legitimate broadcast or just background noise. * Also, with analog radio broadcasts, a signal could be very faint and yet still have listenable qualities, so radios don't blank out channels even if they detect mostly noise because the user might still want to listen. * With digital broadcasts, there is identifying information in the broadcast data that tells the radio this is a station. * Without that data, the radio knows it's just background noise."
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12,
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dej6ei | What is Kubernetes, containers, & microservices and how do they all work together? | I’m going into tech sales and looking to understand these terms so I can explain it to my clients. | Technology | explainlikeimfive | {
"a_id": [
"f2vlpdn"
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"text": [
"A container is a self contained application, typically. It can be run on any platform that can run the container service (usually talking Docker here). Useful for distributing and managing applications that would otherwise have complex dependencies. Kubernetes is software that orchestrates multiple containers. Microservices are the services made available through those containers or groups of containers."
],
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3
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dekzpu | Why are phone calls such bad quality when something like a radio presenters voice is so clear? | Technology | explainlikeimfive | {
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"f2wbp6k",
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"text": [
"Available audio bandwidth. A plain telephone circuit is optimized for audio from 30hz to 3000Hz, which is where the majority of audio in the human voice is but not all of it. To add on, most telephone calls these days are digitized and compressed to save transport costs and that compression causes some loss of quality. Now, an FM broadcast signal is much, much wider because it is built to send high quality music (usually up to about 20,000hz) and subsequently, none of the quality of the announcer's voice is lost.",
"Essentially, telephone companies only use as much info for your calls as they need for you to be able to understand the other person and vice versa, whereas radio broadcasts use higher sound resolution",
"Bandwidth is one issue other have brought up but another big one is your microphone and environment. Your phone microphone is just not that good. It can't be, it has to fit in your phone. A professional microphone like what the radio presenter is using is large than your whole phone by like a factor of 10. It also has a pop filter a sound bored and mixer connected. The radio presenter also isn't in some random room. They are in a room that has been designed to make them sound good. At a minimum were are talking foam sound absorbents to stop sound refection, and outside noise. The room is often a special shape as well."
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11,
3,
3
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dem8g7 | What is 'Ray-Tracing' and why can only special RTX Graphics Cards render it? | Technology | explainlikeimfive | {
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"f2wnirs"
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"text": [
"Ray tracing is an expensive computer calculation where essentially every pixel you see on the screen is illuminated by tracing rays of light from it back to every light source in the scene. This means bouncing it off shiny/chrome/mirror surfaces, refracting through different materials, water, coloured glass, lenses you name it. Depending on how many light sources there are and how many transmissive, translucent or reflective surfaces there are, a single pixel can be hit or lit by rays from numerous sources or reflections. This gets computationally expensive very fast. _But wait, isn't this what is done already in video games?_ No. There's lots of tricks that can be used to make the graphics math easier for shadows and stuff. One way is to make a shadow mask of a model - lets use a tree as example. So you take a light and shine it right down on the tree. The shadow that the tree makes is used to create a mask or a 2d shape which can be drawn and maniupulated really quickly. To simulate the shadows moving as say the sun changes position in the sky, that mask gets moved from side to side in line with the sun vs. the middle of the tree. As the sun sets the mask gets stretched. To simulate the branches being moved by the wind, you take that mask and distort it in time with the tree model being distorted. But the shadow likely is NOT being cast dynamically by a complete detailed model of the tree. In ray tracing, it would be."
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6
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demeky | How do screens smoothly scale resolutions that aren't multiples of each other? E.g. playing 1080p or 720p video on a 900p screen, or reducing my phone's resolution from 1440p to 1080p? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"There are complex algorithms that will combine pixels with their neighbors in certain ways. If you have a higher resolution screen being scaled down such that a pixel should be 70% one color and 30% a different color, the calculation would yield a combined color of the appropriate proportions.",
"There are formulas, and basic version is fairly simple. You know coordinates of the pixel, and its color. Coordinates are numbers, color is also numbers: three numbers per pixel, i.e. the intensity of Reg, Green and Blue. You can make a math function mapping any coordinate to color: URL_0 Then you put a new grid of new pixels over that image, and read the color at each new pixel. Or a really simple example. You want to display 720 image on a 1080 screen. Note that 720/1080 = 2/3. Take first pixel from 720 image. It is the corner, so we make first pixel of 1080 screen the same color. Let's assume that color is completely black (0% white). The next pixel in 720 is 100% white. It is 1/720 to the other end of the screen. The next pixel in 1080 is 1/1080 to the other end of thescreen, i.e. it is between first and second pixel of 720 image. But it is also closer to to the second pixel: 1/1080 = 1/720 * (0.6667) + 0*0.3333. 1/720 and 0 are positions of first and second pixels, and 0.6667 and 0.3333 are their \"weights\", or distances of to the second 1080 pixel. So with linear interpolation, color of second pixel in 1080 should use same weights on colors of 720 pixels. 100%*0.6667 + 0%*0.3333 = 66.67% white, i.e. darker shade of gray.",
"A lot of math and programming. Long story short, the system (phone, computer, whatever) has software and sometimes hardware that quickly does the needed calculations to adjust to resolution to the screen. If it does not divide evenly a system of correction is used. Pixels are \"averaged together\" or combined in some way to make a fitting scaled down version."
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"https://wiki.tum.de/display/lfdv/Super-Resolution#Super-Resolution-ClassicalApproaches"
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demnxg | What is the use of recaptcha, why would a robot create a Nintendo account, even if it did why are we stopping it? | Technology | explainlikeimfive | {
"a_id": [
"f2wsa07",
"f2wslid"
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"text": [
"Denial of service attacks on their servers are bad. Spam bots are bad. Have you ever been on a forum where bots got in and made users to spam horrible things or advertising messages. That’s why.",
"Primary reason: bots. Wether data gathering bots or actual people trying to hard crack your site. they NEED access to that info, so now people upped their defense against these bots with method such as a human verification text. Which motivated the bot writer to get past these security, so bots that can decipher text became a thing, and now its like a on going arms war in the digital world. And the end result is the current recaptcha, using a combination of picture and confirmation clicking . This proven to be successful, for now."
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deomn7 | How did we discover bread? Like it seems to be a rather complex mechanism to make bread was this a gradual thing? | Technology | explainlikeimfive | {
"a_id": [
"f2xi04m",
"f2xg9lj"
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"text": [
"Well, we know that people living in the northern part of what is now Jordan were making bread as much as 14,000 years ago, but so far we have no idea who was the first person to make bread, or how they figured it out. And breadmaking could have started much earlier than that, but we can't be sure until we find actual evidence of it. Based on the archaeological evidence that we do have, we know that people were eating various grains and seeds for thousands of years, probably using them to make some sort of porridge, which really just requires putting seeds into water and getting the water hot. So given that some people were already familiar with wild grains, and with cooking them to make them easier to digest (and maybe better tasting), it wouldn't take much creativity for someone to think \"Oh hey, I wonder what would happen if I ground them up really good first and then cooked them\". The earliest bread may have been cooked simply by slapping blobs of dough onto hot rocks around a campfire, a method that's still in use today, in one form or another.",
"Nobody knows for sure but it's likely that people found grinding seeds was a good way to get the hull/shell off it and it's only a small step from there to mixing it with water to make a paste or trying to cook it. Adding yeast probably came later and possibly after the invention of beer."
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17,
4
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depity | when you can buy a 1080p camcorder for a few pounds, why does so much CCTV and shoplifter footage released by the police look so bad? | Technology | explainlikeimfive | {
"a_id": [
"f2xqtgj"
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"text": [
"You generally are only storing about two hours of footage on that 1080p camcorder. The file sizes are pretty huge. A CCTV system needs to be storing days worth of footage, often from multiple cameras. Most stores aren't willing to spend thousands upon thousands on high end hard drives just to store better quality security footage."
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3
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deps6l | why were we all asked to turn off our electronic devices before landing ‘due to poor visibility’ on my flight today? | Technology | explainlikeimfive | {
"a_id": [
"f2xu5m8",
"f2xvhxg"
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"text": [
"The electronics interfere with radar and telecommunication, and if there's clouds and lack of visibility through the windows then they have to rely on radar and other stuff",
"The Federal Aviation Administration (FAA) does not actually prohibit the use of personal electronic devices (including cell phones) on aircraft. HOWEVER, it does leave the power to airlines on the basis that it does not interfere with navigational ability of the plane. During low vis condition, planes will be flying under IFR, meaning purely by instrument. This meant in a large 747, all 450ish people's life depend on the accuracy of the instrument to provide detailed altitude, speed, and location. and THIS IS ESPECIALLY IMPORTANT during take off and landing. As to how it effects navigation? thate because the way ILS (instrument landing system) works. ILS works by sitting in the middle of the runway end and generating 2 EM fields, and if you are approaching off center, it would be more negative/positive, thus making you correct the path toward the neutral, aka, middle. Cell phone generate EM field, thou small, do you really want to risk 450lives landing wrong because of a few moment's convinience? hence, its much more simpler and convinent to just turn them off."
],
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3,
3
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derdmp | What's the difference between a Greenscreen and a Bluescreen | Technology | explainlikeimfive | {
"a_id": [
"f2ydmsz"
],
"text": [
"The colour, that's literally it. A green screen and blue screen are used for the same purpose, to give programs like after effects a colour to focus on to remove from the images. It all depends on what the scenario is. If you are filming on a set that requires blue lights to make the subject match where they will be getting composited into, then a green screen would be better, as if you tried using a blue screen then the key would also pick up on the blue light on the actor and start removing bits of them too. The only real difference is the scenario you use one in."
],
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8
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dermxi | How well does the camouflage militaries use actually work? And if it works well, why? | I don't know, maybe it's cause I'm an ignorant idiot, but the camouflage doesn't look very camouflaged to me. Especially in places like the middle east where they keep going off to. So like explain? | Technology | explainlikeimfive | {
"a_id": [
"f2ygwe2",
"f2ygx2r"
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"text": [
"Camo is not intended to make the wearer disappear. That is more the function of ghillie suits and similar apparel. Camo tends to make the wearer harder to spot. In a situation where two people are trying to kill each other with guns, delaying your opponent's recognizing you for a fraction of a second can be the difference between life and death. Meanwhile, if you just sit absolutely still in good camo, people may not notice you. Even without it, if you're wearing drab colors and you lay down in a bush for a while nobody is going to notice you. The purpose isn't so much to be invisible as it is to *not stand out*.",
"Well it depend if you bring the right camouflage, but keep in mind that camouflage is about breaking your outline in medium to long distance, not 5 feet in front you. Take a look at this video where they show you different camouflage in different desert environement. You can still spot them in most of the shot, but you know where you are looking, it's another thing when you are in a firefight or don't know that people are there. [ URL_0 ]( URL_0 )"
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"https://www.youtube.com/watch?v=tUTIvWge0NM"
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detxh7 | How does my phone figure out how much to delay video so it matches my Bluetooth headphone delay? | When I use my Bluetooth headphones to watch videos on my phone, the phone usually delays the video enough to synchronize it with the delayed sound on my headphones. How does it figure out how much to delay it? (I have other, secondary, questions too: how close does the timing have to be so I don't notice a mismatch? And why does it sometimes mess up?) | Technology | explainlikeimfive | {
"a_id": [
"f2z1c0d"
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"text": [
"I know that other streaming protocols have round trip time synchronization built into them which might be what your headset is doing. Basically your phone sends a packet of audio to your headset and then the headset sends back an acknowledgement of receiving it and playing it. The round trip time is measured and divided in half. This allows your phone to know how long it takes and offsets your video play back. As for the issue with being out of sync that is probably because the packet turn around time is an average. One bad packet, one extra delay and it's all off and needs to be synchronized again."
],
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6
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deumkj | When you’re browsing the Internet on mobile some links will open a new tab when you click on them, but then if you swipe or press the back button to go back a page it will take you back to the original tab and delete the new one; how do some websites do this? | Technology | explainlikeimfive | {
"a_id": [
"f2z601t"
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"text": [
"Because that tab literally didn't have anything in its history, since it is newly created, so going back means removing the tab and returning to the previously opened one. Websites do nothing to contribute to that behavior, it is the browser who does that. What the website only usually do is tell the browser to \"open this link on a new tab\", then the browser handles it from there. It behaves differently on desktop browsers, at least in Chrome which I am using now; as the back button is usually disabled when the tab has no pages to go back to anymore."
],
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6
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deux2r | Why do downloads take so much time? | Why do downloads take longer than like 2 seconds? Couldn't it all just get sucked up like a caprisun? What is the reason for the device to slow the intake of data? Like I'm downloading a game on my PS4 and it's going to take 5 hours, why is that? Thanks in advance! | Technology | explainlikeimfive | {
"a_id": [
"f2z6jz6"
],
"text": [
"Because internet bandwidth works like water pipes, the flowing water is the data. The size of the pipes represent your internet speed and the pressure of the water flow represent how fast the download server is hosting your download. The files come in specific sizes and you need to download each portiom of the data gradually. The bigger the download, the longer the time. You can download a file like sucking a caprisun if it's small and can be consumed by your internet speed quickly."
],
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7
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dezyuj | Why do some recycling points not allow soft plastics like bags and cling-film? | Technology | explainlikeimfive | {
"a_id": [
"f2zxu0j",
"f2zz6bh"
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"text": [
"Recycling plants use systems of conveyors and sorters to move and sort stuff into appropriate categories for later processing. Things like cling film and bags can gum up the works. A lot of recycling places can easily recycle that stuff but it needs to be bagged. So, a bag of bags is fine because it isn't going to waft up into the gears and get stuck.",
"Thin plastic is pretty much impossible to economically recycle. Problem one is to gets jammed on normal conveyer belts and stuff (gets stuck on anything that spins). That can be dealt with, but it adds cost. The bigger problem is economically melting it, it traps air, and it makes it difficult to melt it down into a liquid, heating a pipe and stuffing it into the pipe, as is done with other plastics, doesn't really work, it's so full of air the center has trouble melting, it goes much slower (again adds costs), you could try compressing it, that would probably result in fizzy plastic (really poor quality), you could improve that with a vacuum, but that gets really expensive. And to top it all off, it's thin and traps junk, it's much harder to effectively clean, normal plastic can be chopped up and washed in water. Plastic bags are not cleaned effectively by that, and their thinness means they have much more dirt and stuff per gram of plastic. In the end, they are not impossible to recycle, but doing it is going to cost an order of magnitude more than other plastics, and it will result in significantly inferior plastic. Today soda bottles are barely worth it to recycle, we do it because we want to recycle, not because it saves anyone money. Only aluminum cans are worth it in typical residential recycling. Plastic bags are honestly best just burned as a fuel source after some light reuse."
],
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df59e7 | Why is off-brand toner not good for a laser printer? | I have cleaned several different laser printers and experienced first-hand the yucked-up drums caused by generic branded toner cartridge. Pop in proper genuine toner afterward, and print problems are gone. I was always frustrated with printer companies when I would ask for help, being told, "we can't help you unless you are using genuine toner...you need to use genuine toner to ensure proper printing", but they could never explain *why*. I kind of feel like this could be flagged as chemistry as well, because it's obviously the makeup of the toner...? | Technology | explainlikeimfive | {
"a_id": [
"f317nzw"
],
"text": [
"Why? Because genuine toner and ink have a quality control and standards that are set by the printer manufacturer. Off brands may be as good and cause absolutely no problems, but they may also be made up of nothing but tar and lost dreams of a Scotsman named Dave, and cause your printer to have a meltdown. The only way to guarantee that the cartridge won't cause any issues, and the only way to hold liability for it, is if you use a branded and quality controlled cartridge."
],
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7
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df5faw | Why are drones and jet packs just happening now? | Particularly drones: Why are they just starting to happen now? The concept is simple... they're easy to make... the parts aren't really hard to find/make. Why did it take this long for them to become common/popular? Seems like they could've easily been made many years ago but they weren't. | Technology | explainlikeimfive | {
"a_id": [
"f30zufn",
"f3135ze",
"f311nxn",
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"text": [
"There haven't been any particular breakthroughs in the technology except that batteries keep getting a little bit smaller and a little bit more energy dense and little more cheap to produce, year after year after year, and we've lurched over a threshold where they are now light enough and energy dense enough and cheap enough that compact, battery-powered flying machines are now both feasible and cost-effective to mass-produce.",
"> they're easy to make... the parts aren't really hard to find/make. They're not easy to make small and light enough to fit in an RC drone, however. Yeah we've had things like batteries and rotors for a long time, but they were big and bulky. It took a few iterations of refining the involved technologies to get them good enough for this particular application. It's kind of like why we didn't get cell phones until decades after the first radios, or why it took over a century after the first steam engine was built to make the first steam locomotive. Or why we don't currently have lifelike androids despite having the ability to create AI and various materials that mimic the human body. Sometimes we can have the pieces and understand the concept but still need time to refine them and put them all together.",
"We didn't have the battery technology for long and/or heavy flights back then. * Old-style batteries are heavy and can't generate enough power to lift themselves. * In cases where you had a battery that was powerful enough to lift itself, it wouldn't last long enough in the air to be useful. Now we have small, powerful, and long-lasting batteries.",
"We have had them for decades. When I was a kid they were called RC's because they were remotely controlled. The changes now are in cost and the progress of the computing boards that allow them to now operate without constant human input."
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dfbk1k | Why do smartphones take so long to boot up after they “die”? | Other household electronics power up as soon as they are plugged into an outlet (Pc/laptop, gaming console, camera, microwave etc...) | Technology | explainlikeimfive | {
"a_id": [
"f3249zf"
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"text": [
"Unlike those devices, a smartphone has to load an extensive operating system consisting of perhaps 50 different programs all of which need to be running before it can be used."
],
"score": [
8
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dfcl86 | Why do spam ads bother allowing you to close them? | No matter how annoying, they always have an "X" to allow you to close them. Since they are spamming anyway, why not go all the way and not allow you to close them at all? Is there some kind of law they are following? | Technology | explainlikeimfive | {
"a_id": [
"f32cy28",
"f32dpwe",
"f32bvag",
"f32h9f9"
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"text": [
"By giving you an X to find they ensure that you engage with them on some level, hopefully ramming some aspect of their content into your consciousness. Another issue is that by giving you a method of avoiding them they hopefully keep you from searching out a way to get rid of them entirely such as ad blocking software.",
"It likely has to do with the host site. Most sites or apps aren't going to host ads that cannot be closed. Sure they're paid by ad companies, but nobody is going to use a site or app if when an ad pops up they can't close it.",
"Because they can get data out of which you choose to close. That way, they can target ads which you are more likely to respond favourably to, which means that they can charge more for their ads.",
"There is no law that says the ad must have a way to close it but there are industry standards under which it is considered bad practice. Also, there is no point in having such ads. If you cannot close the ad you might not be able to use the site and you are more likely to not visit it again than if you can close it. This is bad for the site because it does not use ads to annoy you, it sells the ad spaces so that it can earn money. Basically the website has an empty box on the page and it puts it up for sale to whoever wants to show their ad there. It is up to the website owner to pick where the box will be placed and where the X that closes it will be. So, unless the advertiser says \"I will only pay you if my ad will be shown for N seconds\", it does not matter whether you close the ad within 2 seconds or you keep it open - the website gets the money AND gets you to stay on the site (and maybe keep visiting in the future). TL;DR There is no such law but it gives you bad reputation and there is no use in it because website wants both money and you. Source: I work in digital advertising."
],
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dfcm98 | What is kernel memory protection? | I installed Linux on an old machine, and the system displays this message during boot: > Your architecture does not support kernel memory protection What is kernel memory protection? | Technology | explainlikeimfive | {
"a_id": [
"f32ax71"
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"text": [
"When an application runs on your computer the OS gives it a block of memory to use for doing whatever the app does. When you try and access outside that boundary the OS should catch it but many times bugs in code are found where memory can be access \"illegally.\" It's bad when one app can read another app's memory but what if you could read the Kernel's memory??? Some CPU architectures supporting a type of memory management where the OS memory and applications' memory are separated so that when an application asks for an illegal address the CPU just won't allow it. Apps just aren't allowed to access kernel memory because the CPU has them physically separated."
],
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5
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dfdft7 | What is the point of the iPhone’s AirDrop feature? | Technology | explainlikeimfive | {
"a_id": [
"f32frdx"
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"text": [
"It basically is an alternative or a simpler way to share files via Bluetooth. It doesn't require any connections other than the one to the other phone, and works between any iDevice that supports it, such as iPods and Macs."
],
"score": [
3
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dfggux | how come iPhones dark mode is easier on the eyes? | To me, the brighter the phone the better? Or am I squinting and not realizing it? | Technology | explainlikeimfive | {
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"For people with “normal” vision, dark vs bright just a matter of taste as far as we know. Some people with some forms of severe astigmatism find that the light text + dark background can be aggravating for their symptoms, so they’d probably choose light mode instead. The more important light wave is the blue light, that can make your eyes tired, disrupt your circadian rhythm, and may lead to macular degeneration (to be studied further)."
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dfi97e | What are OEM products? | Technology | explainlikeimfive | {
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"OEM - original equipment manufacturer. So OEM ARE authentic products. I think what you meant are \"after market\". Aftermarket products/parts are ones that are either made under license by the OEM ($$ in exchange for original engineering drawings, specs etc.) or are reverse engineered. If I drive a Chrysler/Dodge car and I buy only parts from Mopar, I'm buying OEM parts. If I get new fancy rims from Fastco, thats aftermarket."
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dfkna7 | How did a block of TV sets in the 80s pieced together form only one moving image? | Technology | explainlikeimfive | {
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"Using a splitter. The incoming signal would be fed to a box that would handle how to divide the signal then give each tv it's portion of the whole image. The splitters were bulky from what I remember and caused a slight lag."
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dfmq7e | Why are tiff files so large? | I have a Panasonic G85 that produces 18MP raw files. But if I edit in PS, even without adding layers, the resultant tiff files are around 150MP. Where is all this extra data coming from? | Technology | explainlikeimfive | {
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"> 18MP > 150MP I'm guessing that the first is actually meant to read MP, while the second should probably read \"MB\"? Because \"MP\" means \"MegaPixel\" (million pixels), while \"MB\" means \"Mega Bytes\" (million/ 2^(20) bytes). So let's take a look at how much that actually is: 150/18 = 8.333… So for every pixel, there are eight and a bit bytes used. Let's just call it an even eight and attribute the rest to metadata (when was the photo taken, what were the iso, shutter etc. settings, maybe GPS coordinates, etc.). Depending on your colour scheme (RGB/ CMYK/ RGBa/ …) and bit-depth (8-bit/ 16-bit/ 24-bit (\"true colour\") / …), this leaves between one and two bytes per pixel and colour channel. That actually sounds very reasonable. Heck, it isn't even enough to give you true-colour RGB - that would need 3\\*3=9 bytes per pixel (three colour channels, each of which having a precision of 24 bits = 8 bytes). & #x200B; The reason other formats like jpeg or png will generally produce far smaller files is that they utilize (lossy) compression, which simply means that they don't save a colour value for every single pixel but instead try to save space by doing thing like saving \"the next five pixels all have this colour: \\[…\\]\" (very simplified)."
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dfq9q1 | How can an online mobile application still be accessible offline? (IE. Youtube App can still play some videos even if you are offline) | I heard spotify has this as well | Technology | explainlikeimfive | {
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"You have to indicate what items you plan to access, and it downloads them while you are still online, then saves them in your device's internal storage for later playing."
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dfrm8j | Why are space missions to moons of distant planets planned as flybys and not with rovers that could land on the surface of the moon and conduct better experiments ? | Technology | explainlikeimfive | {
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"A flyby only requires acceleration to escape velocity from earth, then some more to send the craft on its way. A lander or orbiter also requires massive fuel with the spacecraft to slow it down again as it approaches the target, and to match orbits with the target. It's not technically that much harder, it's just that the fuel weighs so much, and reduces experiments, sensors, and whatnot that they could take with them.",
"OP obviously never played Kerbal Space Program. The ELI5 answer is, you're flying at these planets/moons super fast, and to land on them you'd have to slow the fuck down. But in space things don't stop unless you use a ton of fuel.",
"For most planets we don't have a big enough rocket to send a large probe in a timely manner. The 500 kg New Horizons probe was launched on an Atlas V 551 which can send 19 tons into orbit, but because it would need to be going fast to catch up to Pluto it couldn't be too heavy or the rocket couldn't get it up to speed If you make your payload twice as heavy then you need a rocket that has twice as much fuel to get it to the same speed. Landers are big so they'd require a lot of fuel, and slowing down to land will require even more. We just don't have big enough rockets to land large rovers on most of the outer system moons",
"Cuz they're more expensive and way harder to plan, lower chance of success, it's basically a way bigger risk. For gas giants like Saturn, Jupiter etc there isn't much \"land\" it's just really really thick atmosphere so the rover doesn't got much to rove on... Also the further away from Earth you go, the harder it is to communicate and control the rovers, so a fly-by which is pre planned is way more efficient.",
"You are missing intermediary steps with orbiters and stationary lander. First compare a flyby and a orbiter. New horizon passed by Pluto at a speed of around 14km/s you can compare that to orbital speed for low earth orbit that is 7.8km/s or even better to orbital speed around our moon that is at around 1km/s. So you need to reduce the speed by 23km/s. A rocket that launches stuff into low earth orbit only need to accelerate by a bit less then 10km/s. The atlas V that launched it from the ground only . So the acceleration to get into obit around Pluto is close the total amount that was needed to get there from the surface of earth. The probe only had internal fule to accelerate 0.29km/s or 1/100 of what was needed for orbit. So we can launch stuff that is large enough to have enough fule to slow down and get into orbit and at the same time travel there in a resonable time that in this case was 9 years. So the only option was a fly bye or nor mission at all. For the planets Saturnus and closer we have launched orbiters that have stayed around them and visited the moons. The moons might just be flyby because to get into orbit require more fuel then just a flyby and you have a limited amount of fuel so the number of maneuver are limited. Now for a orbiter vs lander comparison. A lander with a rover or not will provide a lot more data of the location they land but just for that location where a orbiter get more data but for the whole planet and moons. So it is a very precise data for a single point or data for the whole planet. So both is done and initially you use orbiters to get a overview and then you might know where landing is a good idea and how to land. A orbiter is cheaper then a lander because you do not need to build the complex lander. A stationary lander smaller and cost less then a rover that can operate for a longtime. You can look at earth and ask why we have weather satellites and other earth observation satellites when we can be on the ground. Some data you can only get from orbit and you can get data from larger ares quite simple. The same is true on other planets. For the gas gigants landing is not a option because there is not ground to land on or at least none where any probe can survive. So \"lander\" is a short singe observation and it had been done with the Huygens probe in Saturnus. The rover on mars have not traveled far. Opportunity that if I am not mistaken have the record of 45.16 kilometers (28.06 miles) after 15 earth years when last contact was made so it is very small areas you can examine. So flybys are a lot cheaper and something the only option for a resonabel travel time. Orbiters are better then just a single flyby and you can do flybys of a loot of moon on Jupiter and Saturnus on a single mission. Leanders provide more data of one location and not data or everywhere else where a orbiter have less data of perhaps the whole object. So what you do depend on the goal",
"It's very easy to shoot a bullet. It's very difficult to attach thrusters to the the bullet to make it land where we want it and how fast we want it to.",
"The first mars rover mission, with the Opportunity rover cost $400 million. & #x200B; The second mars rover mission, with the InSight rover cost $828.8 million. & #x200B; The third mars rover mission, with the Spirit rover cost $400 million. & #x200B; That's a total cost of $2.5 billion. & #x200B; It's a lot cheaper to do a flyby, because then you can also do another flyby of something else instead of dropping it all in one place. & #x200B; In the mean time, we've spent about $5.9 trillion on stupid fucking wars since 2001, which kinda eats into the space exploration budget (and the education budget and the infrastructure budget and all the other budgets).",
"Because to get out there, you need to be moving really fast. Way too much \"delta V\" to slow down to a point where they can land. Also, due to the extreme distance, it would take way longer to send and receive movement signals from a lander - the martian landers only move a few meters at a time (I think).",
"Hey Bobbi, the reason we do rocket flybyes is because the rocket is going so fast it's too hard to slow down. Remember Bobbi, all the force we used to get the rocket going that fast has to be slowed back down just to land and it requires a lot of tricky things to happen just right. So instead we just look out the window and take some pictures.",
"Lander's have made it to the moon, Mars and venus. The venus lander didn't last very long. Mercury is far too inhospitable the only other planet we could put a lander on would be pluto as the rest are gaseous planets. There are moons to those planets, such as Europa or titan, but the tech isnt advanced enough to perform any science on those that would return enough info to justify the cost of the mission.",
"The simple, non-scientific answer is: Money. It's much cheaper to fly by. Who is gonna spend billions to send a rover to a distant moon and why? The cost/benefit doesn't make sense.",
"You can fly by a lot more planets than you can land on, and it costs less to fly by a given planet than it does to land on. If we had the resources, we'd land everywhere.",
"In addition to the other answers, rovers need power. Solar is not reliable enough for distant missions, which means they need to use Radioisotope Thermoelectric Generators. These generators require Plutonium 238 which is a rare, expensive, synthesized material.",
"A flyby means you only need to speed up. A landing means you need to speed up and slow down again. This means you need to either use the moon's atmosphere to slow you down, or carry enough fuel to do the job. Carrying enough fuel means the rocket must be much, much larger, which is impractical. Therefore, landings are only really done where the atmosphere is thick enough to slow the craft down enough. Think Mars and Titan.",
"You have to go reeeealy fast to get anywhere in the solar system in a reasonable time. That means you have to then slow down to get into orbit of that thing. The only way to slow down in space is to turn around and fire your rocket backwards, which means you have to take a lot of fuel. Fuel is really expensive. So it's actually cheaper to send a few flybys of different places than to sent a rover to one place.",
"Planetary protection, we currently do not have the required processes to ensure we build clean machines, we do not want to contaminate the planets/moons, not until we have proven life can exist first. I forget the terms and jargon, I studies this a few years ago, but essentially a lot of countries signed an outer space treaty that includes planetary protection. This has 5 levels, level 5 being you can not land anything. Level 1 is more like the moon, you can land whatever you want. This is why we have never landed in any areas that could have life, such as the ice caps of Mars or the oceans of Europa. We need to ensure we build a clean vehicle, which remains clean in space, and on landing of the planet.",
"Play ksp bro. I can't believe how quickly I can answer this question thanks to 1000 hours of Kerbal space program. Simple answer is cost. Obviously if cost was of zero concern, we would over engineer and do everything we want but cost is a limitation. Every space mission is risky. Thing may not even get out of the atmosphere. Having a probe do flybys means they can use minimal thrust and use gravitational pull to redirect their craft to hit multiple targets with minimal cost. Landing means a lot of additional cost to land a rover and we don't really have a great system for getting it back. So a flyby probe can be relatively low cost and get us lots of data on multiple planets or objects. Where as landing a rover would be a huge cost for very specific data on a planet or planetary body. So we start with flybys and we learn and we make decisions about if we want to invest more money into getting more data from a specific object. Think Mars. Now we have rovers but it didn't start with rovers. It started with flybys and orbiting satellites to provide data on the planet and eventually we determined, hey we can definitely land a rover and get more data. But if we just blindly sent a rover, who knows if there are conditions that allow for landing. Who knows if the atmosphere or planetary weather will allow for a rover to survive. It's too much cost for too high a risk."
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dfrrki | Why can't we just copy and paste a code for a videogame from a certain platform to another platform instead of rewriting it? | Technology | explainlikeimfive | {
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"Code languages are an abstraction, a way to tell another program called a compiler what order to put the 1s and 0s in when actually writing and executing the code. Different hardware has different compilers which handle things differently. For most applications this doesn't matter, but for video game consoles which are trying to maximize game experience for minimum cost, the limitations of the hardware matter a lot. A game meant to run with a certain amount of dedicated graphics processing just won't work with less, and might not work with more if the more is structured differently.",
"How you accomplish something is usually platform specific. While the internal logic of the game will remain the same (or at least fairly similar) the interface between the game and the device will vary widely, the the extent that almost all of the coding will concern that. That said, there have been attempts to insulate programs from the hardware differences. COBOL was an early effort, but there are still differences between COBOL on different platforms. More recently, Java, which interfaces with the Java Virtual Machine is also oriented to accomplish that. OTOH, speed constraints often require that device specific programming will be included since device independent code is usually radically inefficient.",
"No one in their right mind is rewriting an entire program when porting it (except maybe if you port truly ancient code or so). If you are porting a game you are in fact keeping the overwhelming amount of code and just \"copy it over\". Only a tiny fraction (in terms of lines of code) needs changing. And often that is compartmentalized away in some kind of abstraction layer/library. BUT software is absurdly complicated with enormous amounts of edge cases. So any small change to something as fundamental as the the operating system/hardware interface can throw lots of hard to debug wrenches into the machinery. So really what actually happens is that you get the software compiled and running within the first week and then spend months chasing infuriating subtle bugs.",
"Think how many things the game has to deal with at once: - Loading/holding all of the assets (pictures, shapes, sizes, and animations of things in the game) - Drawing those for the player - Taking input from the player - Sending that info to a server if multiplayer - Running calculations like - Checking angles for fired shots - Running AI - Calculating physics for characters or objects - Changing values of health, ammo, etc - Moving the characters around And that’s just off the top of my head. That’s a tremendous amount of work, and if any of those things take a noticeable amount of time, the game is unplayable. So each of those things has to be done as fast as possible, especially given that many of them will have to be done dozens or hundreds of times a second. To accomplish this, game programmers can’t use code that you might be familiar with—languages like Python might be nice to code in due to their plethora of built-in tools and the fact that the code is readable by a human, but it’s far too high-level for the speeds we need. Imagine trying to narrate a movie in English as it’s happening. Just because of the constraints of language, the fact that you have to come up with the words and have the listener hear and parse them, etc., there’s no way that you could describe everything on screen in perfect detail. Instead, the programmers use very low-level code—that is, they give the computer direct instructions like “move the value from $memoryAddressA to $memoryAddressB and then add 8”. The downside is that they have to know how the computer thinks and works intimately, because they’re being as raw as possible. They also use as many tricks as they can to save space or time. For instance, in the old GBA Pokemon games, “shiny” pokemon just had the colour scheme of the Pokemon that was next on the master list. When the computer went to look for the colours of the Pokemon, if the “shiny” value was true, they just went to the address of the regular colours and added 1. But—and here’s the answer to your question—what happens if they try to use that same trick on a console that saves data differently? Maybe it’s saved the colours in chunks all over, and when you go one slot over from a colour scheme, you end up in a completely different section of the data and get garbage results. Then the whole code breaks! Since the programmers are relying on such intimate, subtle details of the language, architecture of the system, or hardware, they can’t just plop the code into another setting because the assumptions they made or optimisations they found almost certainly won’t work—and in fact would break the code, if it even ran at all."
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dftd63 | Why do some old wires (e.g. headphones, charging cables) work when put in some positions but not others? | Technology | explainlikeimfive | {
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"Every cable you have is actually numerous small metal wires bundled together. The issue you've described is called a short in a cable, which means some or all of these wires have broken, so the connection is broken when they aren't correctly positioned.",
"Wear, tear, and rust. Electricity is finicky - if there is no good connection on the connector then it cannot flow. If the wire is severed, a gap in the circuit, it is referred as an open circuit. If the wire touches an alternate path to ground (that has less resistance) it is referred as a short (taking a short-cut around the circuitry) Sometimes we can twist the cables just right that a good connection is made and then it works and other times it doesn't connect correctly"
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dftpf2 | Why does a core only have two threads in a processor? | Technology | explainlikeimfive | {
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"It doesn’t. At any given time in a modern OS there are hundreds to thousands of threads running on just a few cores. The difference is whether the nuance of threading is handled at the software or hardware level. Running multiple threads on the same core in hardware is done through a design called Simultaneous Multithreading (SMT, also branded as “hyper threading” by Intel). SMT is a higher level exploitation of something called “pipelining” where multiple instructions run at the same time on the hardware. Pipelining is a lot like doing laundry. If you have multiple loads of laundry you don’t wait for one load to be washed then dried, you start the next load in the washer while the dryer is running the previous one. In the same fashion, a processor has a lot of hardware in each core and not all of it is used for a single instruction. It has additional logic to allow different instructions doing different things to utilize the hardware in a way to maximize the instructions per clock cycle (IPC). SMT exploits pipelining to allow multiple threads to execute on the same core at the same time, as opposed to the switching between threads to be handled by the operating system’s software. There are trade offs though. The logic for SMT takes up physical space on the chip. The reason it’s limited to two threads per core is mostly because the additional logic for more than two would take up more space and power than you’d benefit in speed up. That’s about it."
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dfugjq | How do those sunglasses that let people with monochromatic or colorless vision see colors? | Technology | explainlikeimfive | {
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"Some persons colour vision problem is that the colours that the different types of light-sensing cone cells detect overlap too much. For these people, glasses that absorb much of the overlapping colours can allow the two different types of cone cells detect different amounts of light, allowing the brain to better determine colours."
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dfum7l | How is it that two different images, but same resolution, can have different storage size? | Technology | explainlikeimfive | {
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"Compression. If an image is for instance pure white, you don't need a huge file that goes: pixel 1: white pixel 2: white ... pixel 1000000: white You just write an image that effectively says: pixels 1 to 1000000: white In practice, compression gets a good deal more complicated than that, but that's the basic principle. And of course it varies depends on content. For instance with the above scheme if each pixel was a different color, the compression would be ineffective.",
"Digital compression algorithms! There are a bunch of different ways to do it. A common method is the only store the differences Let's say you take a picture of a cloud in the sky. There is a lot of white and a lot blue. We don't need to store red and green info in the picture cause its never used individually Additionally the same blue and same white are re used, so we can just say where the blue is and white is rather than : blue here, white here, blue here , blue here, ..."
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dfwjg8 | How did people in the middle ages keep their swords from rusting in the rain? Did people just not fight if it was wet out? | Technology | explainlikeimfive | {
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"Simple, regular maintenance, after using the sword they didn't just throw it back in the scabbard and hang on the wall at home until the next time. It would be wiped dry, re-sharpened and oiled before storing it. A sword is not going to fall apart immediately after getting wet, seriously rusting would take weeks of neglect.",
"Rust isn't instant. Metal needs to get wet and stay wet for the rust process to start up. Fight in the rain then dry your sword off afterwards. Then oil the blade anyway to keep a layer between the metal and the rain.",
"Rust doesnt imediately destroy a weapon, and you can polish it out even if it gets to you, so fighting in the rain is not impossible (even if it isn't exactly fun.) The most common form of rust protection for weapons are oil, grease or wax, anything that forms a barrier against water. Wiping the blade down with an oily rag, or a piece of greasy sheeps wool is usually plenty."
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dfyb8j | How are game consoles and other computer devices able to turn themselves off and on again after an update? | Technology | explainlikeimfive | {
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"Well, technically the device is never really powered off. The CPU and the power supply are linked by some input/output lines and so there's some limited control the CPU (via the motherboard) has over the power supply like \"go into low power mode\" or \"go to standby\".... which just keeps the CPU running at slow speed and contents of memory in the RAM and so on. But in the case of a reboot for say a Windows update. - computer operating system downloads the update. - inserts commands into its startup scripts to run the new code instead of the old - sets a flag at the end of the startup scripts that if it gets to this point it must have worked ok. Otherwise roll back the changes after another reboot. - tells self to reboot - CPU pretends like its shutting down, powering off and on again - follows its startup scripts - it worked, removes that flag/check Literally there are commands like \"reboot\" or \"shutdown -R 'now'\" to shutdown or reboot the operating system. These in turn end with commands for the CPU to literally turn itself off and on again.",
"There are a few different shutdowns that happen when you shut down your computer, and a few different levels that a computer can be \"off\": * Physically unpowered: No power cord or no power coming from outlet (sometimes due to a wall switch or a power supply on/off switch). This is the true \"off\" state. * Powered but shut down: This draws a tiiiiny bit of power that monitors just the power button, and sends a predefined command (held by a really small memory chip, generally) to turn on the power. * Operating system not loaded: This is the \"boot to bios\" option, where you change things like the CPU clock or clockspeed if you're a power-user. But this is best left alone by 99.9% of users. Generally, if you don't interrupt the BIOS startup sequence (that is a preprogrammed set of steps) it will find your preferred boot media or go through your boot order to find an operating system on the first available storage device (this is why, in older computers, you'd get a \"non-system disk or disk error\" message if you tried to boot up with a disk in your floppy or CD drive; the CD and floppy drives were typically first in the boot order, but if there is nothing in them, it moves to the next. That error is saying that there is a disk there, but the BIOS found nothing that looked like it could be loaded into.) * Operating system loading/\"booting from disk\"; the BIOS has recognized a storage device with an operating system that it can boot to, and it sends commands to load that OS's boot instructions into RAM to be executed so that the OS can load and let you use the computer as a consumer. * \"On\": Functional and waiting for you to use it as an end-user. When you \"shut down\" it goes through these stages in reverse, stopping at \"Powered but shut down\"; you have to hit a physical switch for that last bit. What an operating shutdown does is basically take all of the changes you've made to the operating system's initial state, wipe them (except for new installs that go into the OS's load instructions now) and pulls all the data for the OS from the \"fresh\" copy. But I digress; when you \"restart\" your computer sends a signal to the bios that says \"I'm going to unload myself from memory, and the last thing I'm going to do is send this signal, when I do, run through startup sequence again, kthx.\" so it gets into that \"Operating system not loaded\" state, and then kicks the BIOS into re-loading the OS, without ever going through the last 2 phases where it's truly without power.",
"The operating system has different code for restart and shutdown options. As long as a device is receiving electricity, it is never truly “off” and data is retained in the chipset. For a restart option, that data is used to initiate the startup sequence, while a shutdown option does not.",
"The simple answer is that power isn't controlled by a physical ON/OFF switch like electronics had up through the early 2000s. Part of the internal computer ALWAYS has some power as long as it's plugged in. A part of the console's program tells the system which parts of the system to power down and back up. It's all digitally controlled now."
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dfzrgb | Why do some devices get permanently bricked? Since no hardware is getting damaged while fiddling with the software, doesn't it stand to reason that it can simply be fixed by reverting back to its original state? | Technology | explainlikeimfive | {
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"There is a layer between hardware and software called firmware; this has to do with low-level operations that get hard-coded onto a small chipset (previously the BIOS, now there's a new format that I can never remember) that does what's called \"bootstrapping\" (that is, preparing the processor to load and read data for the operating system from a 0-power system. Internally, at a hardware level, this fundamentally changes and alters some pathways, and so if you lose, say, the \"turn on the display\" pathway due to a botched firmware update, it's really really difficult to get that fixed."
],
"score": [
5
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dg0uq7 | How are screens with higher resolutions able to reduce energy consumption when adjusting to lower pixel counts, when the same amount of diodes are still present? | Technology | explainlikeimfive | {
"a_id": [
"f3a76hb"
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"text": [
"The screen itself will most likely keep using the same amount of energy assuming you don't change the brightness or anything, but the computer controlling it will use less energy because it has less processing work to do. Lower resution means fewer pixels, and that means the graphics processor won't have to do as many calculations to drive them. This lets it slow down its processing speed, produce less heat, and consume less power."
],
"score": [
3
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| [
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dg2ndv | If you're not supposed to leave the US and just bought a plane ticket out the country, when exactly do the police find out and how fast can they act? | Technology | explainlikeimfive | {
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"f388hx2"
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"text": [
"Asking for a friend? Not an expert and here is just a guess. Tickets booking don't ask for passport information right away, hence I believe police won't know. But when you check in, then the data must be tallied against a no-fly list and the person can be denied boarding. But the no-fly list is for serious criminals and terrorists. I would be surprised if there is a central database of minor court orders to not leave country. The severe consequences if need to return to the US could be the deterrence."
],
"score": [
6
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dg3zl4 | Why can the cursor on a PC go off screen to the right and bottom but not to the top or to the left? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"The point at the end of the cursor is the exact location of the mouse, which means the rest of the cursor icon is not taken into account. So that exact point is at the end of monitor, which appears as if the mouse went off the screen when it really hasn't, as far as the OS is concerned.",
"The point of the cursor is at the top left and it is the reference point of what you're actually pointing at and it is the thing that really has to reach all points on screen and the rest is just an animation. So at the top and left side it will hit the bounds and stop with the animation on the bottom right still visible but when it hits the bounds bottom and right this animation being bottom right of the actual point moves out of bounds/isn't displayed anymore.",
"In reality, the cursor is a single pixel big. This pixel is bound to the screen. With a standard cursor, this pixel is located in the top left of the arrow, at the very tip. The cursor you see is just an image attached to that pixel. Since this pixel can't leave the screen, when you move to the right or bottom, the pixel is still on the screen (albiet at the very extreme edge) but the rest of the cursor image is off the screen. Going to the top or left, since that pixel is bound to the screen, the image of the cursor can't go off.",
"You can go into your mouse options and set your cursor to a crosshair, which naturally clicks at its center. If you do so, you'll be able to put half your cursor off of every edge - and at the corners you'll only have a quarter visible. It's purely a convention steeped in what's proven to be useful that the mouse pointer doesn't actually surround the single pixel to be clicked, but instead minimizes the obscuring effect to a portion of a single quadrant."
],
"score": [
66,
13,
9,
3
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dg5sa5 | Why can gaming PCs run hundreds of FPS (Frames Per Second) but no matter what console you have, you can never get an FPS number as high as that? | Technology | explainlikeimfive | {
"a_id": [
"f39ftji"
],
"text": [
"Expensive, high performance parts. Think of the cost of a console. It’s around the £300-400 mark, thereabouts. You’re not going to build a gaming PC that can play the latest releases at 144FPS for that price. The same goes for a console. Concessions have to be made to keep the cost at a price point consumers want. The second problem is that a console’s hardware is set long before it’s released. It could be a couple of years between the hardware specs being finalised and the console hitting the markets. By which point it’s inevitable that the hardware is already outdated. A third problem is cooling. If you have a console near you, take a look at it. There’s probably not too many vents, and the ones that are there are small. It’s a small form factor, and it’s hard to keep cool. Your average gaming PC has much more space for large fans, heatsinks etc and as such is able to handle the heat of more powerful components better."
],
"score": [
10
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|
dg7ncq | Why did VHS tapes show a blue screen on the TV when they started up? | Technology | explainlikeimfive | {
"a_id": [
"f39utbq",
"f39x67r",
"f3a22rt"
],
"text": [
"That was the VCR, not the tape itself. It's the precursor to the HDMI no signal screen. Used to be blue.",
"That's not the tape. That's either the TV or the VCR telling you, \"I don't have anything clear enough to show you right now.\" I remember when that was a new thing. Before that, we saw a black screen with white lines or scrambled black and white dots.",
"The blue screen was not from the VHS tape, but rather from the VCR. In many cases, VCRs would be hooked up to the TV with a coaxial (RF) cable. The VCR would generate a NTSC video signal on channel 3 or 4, which you would view by turning the TV to channel 3 or 4. In most of the US channel 3 was reserved (no broadcast signal) for this reason. When the VCR turns on, there was a desire for it to send some kind of signal to the TV so you'd know it was hooked up right. Otherwise the TV would just show static (if using coax) or a black screen (if using composite). Thus, the blue screen. Easy to generate without complex circuitry (remember, VCRs were mostly analog devices) and it let you know the VCR was on, you were tuned to the right channel, and things were hooked up correctly. Later VCRs would then overlay text onto that blue screen or the video image such as PLAY / STOP / etc so you could control the VCR using the screen."
],
"score": [
37,
12,
7
],
"text_urls": [
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dgb5m4 | Why did old TVs have be set on channel 3 if you wanted to play anything linked to it such as a VCR, DVD player, or game console? | Technology | explainlikeimfive | {
"a_id": [
"f3ajjfe",
"f3akl7r",
"f3aw1jr",
"f3avf4c"
],
"text": [
"The game consoles had a built in “video modulator” that took the video/audio and basically had a miniature tv station transmitter inside them. TVs at the time usually just had an antenna input, they didn’t have countless video input ports like TVs do now. So the only way to get video from your game console was to pretend to be a TV station.",
"The signal frequency of the input. If you go further back, when tv’s had a tuning dial, you could tune your NES into the B/W 12” portable. The console/vic20/whatever output a signal at whatever frequency and your TV picked it up as though it was coming from an aerial.",
"There were TVs that were \"cable ready\"and those that weren't. Not being cable ready meant you got channels 2-13 VHF and 14-60 or 80 someodd UHF. Channel 3/4 was chosen by game mfrs cuz a console with a direct wire feed could drown out any station, plus, channel 3/4 were chosen cuz they were likeliest (from broadcaster's view) to have interference from other tv signals. The FCC had to dance around when assigning tv stations to broadcasters due to other stations in nearby cities, and 3/4 got the most interference, so were least often assigned to actual broadcasters.",
"When I was a Kid, we had 2,4 & 7 for NBC, CBS,and ABC. Then we had the Canadian channels3, 5 & 9."
],
"score": [
75,
7,
6,
4
],
"text_urls": [
[],
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dgdl9t | Why does phone autocorrect sometimes forget simple words? | Example: I was halfway through typing the word “different”, and only got suggestions for “differences”, “differentiations” etc but “different” appeared in quotation marks as though I was inventing it. | Technology | explainlikeimfive | {
"a_id": [
"f3auw16"
],
"text": [
"ELI5: phones today use a variety of machine learning techniques to try and guess what you're about to type. More often than not, these algorithms sacrifice accuracy for speed since phones have limited power. Fuller explanation: autocorrect has been making progress for a while now. Your phone has language models built on massive datasets but also builds a dataset just from you. It tries to learn and anticipate what you're going to say and it uses that predictive bias against whatever you're actually typing. Once recently I was trying to type something like \"Denmark\" which is a very difference shape than \"differences\" but my phone was absolutely certain I was trying to type differences. Differences is a more common word by far than Denmark, so it figured that the chances of me meaning to say differences was way higher. This particular concept is called Bayes Theorem. Also if you accidentally decline a suggestion, your phone will remember that for a short time and not suggest it again. Usually."
],
"score": [
4
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dgeayr | why the new electric Volkswagen car will be able to charge within 15 minutes but phones can still take hours to fully charge | Technology | explainlikeimfive | {
"a_id": [
"f3azf4e"
],
"text": [
"Your phone needs to be handheld, portable and small. Your car doesn't. Your car can have active fans cooling, liquid coolant. Your phone can't. Your car charger can have access to a 100kw power supply, your phone is limited to the 1500 watt circuit in your house."
],
"score": [
8
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dgeb7u | iOS WiFi Sharing | Technology | explainlikeimfive | {
"a_id": [
"f3b09ar"
],
"text": [
"Your phone knows the wifi key, theirs doesn’t. But you exist as a contact in their phone, so it uses the same technology as airdrop to contact your phone and present the question to you about sharing the pass code."
],
"score": [
5
],
"text_urls": [
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| [
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dgh1lq | Whats a cookie in the web? | Technology | explainlikeimfive | {
"a_id": [
"f3bfgvy",
"f3bmfx0"
],
"text": [
"When you visit a website, it stores a little data file on your computer. That's the cookie. It might be used to record what you looked for last time, for example, or other info about who you are and what you did, which it can use later on -- even if you go away and come back later, unless you've cleared your cookies.",
"Eli5: Imagine you are at a store where all the goods are kept behind a black wall. There is a shopkeeper behind that wall, but you can't see them and they can't see you. Let's say you need to run out to your car to get your wallet, but you've already picked out a bunch of items. You want to tell the shop keeper to keep these items safe for you, but they don't know what you look like. So the shop keeper writes on a little piece of paper some secret information that would be very hard to randomly copy and a list of the items that you had. When you return, you show the shop keeper with ticket the shop keeper gave you, and the shop keeper recognizes you and gives you all the items back to keep looking around the store. When you leave, the shopkeeper says they are running a rewards program and gives you a piece of paper before you leave that uniquely identifies you so that the shop keeper can look you up next time you come in and make sure you get all the benefits. You leave the store, but you keep the piece of paper to present the next time you are shopping there. Imagine now that these papers can automatically add new information to themselves, \"client picked up a vacuum cleaner and marveled at it, but did not buy\". \"Customer waited for 1 minute at the till before canceling purchase\". Furthermore, you don't even need to ask for them from the shopkeeper, and you dont need to show them to the shopkeeper, this behavior happens automatically when you leave and enter a store. Every store will say \"do you consent to use papers\", if you continue then they will do it without asking again. When it returns this information to the shopkeeper as you leave, the shopkeeper thinks, hmm this person wants to buy a vacuum, but they did not purchase one. Imagine now that this shopkeeper has many different stores, some are for entertainment or other purposes, but all maintained somehow by the same shopkeeper. You come to one of their establishments and they automatically collect your papers. Suddenly one of the advertisements that was on the wall changes from dog food to a vacuum cleaner, the exact model you were looking at. You are your computer, the shops are the websites that you interact with, the shopkeeper is the server you are talking to, and the pieces of paper are the cookies. Less ELI5: Originally they were designed as a way to authenticate users to maintain sessions (a fancy word for not completely resetting all the content of a web page when you leave and come back, things like shopping carts) and maintain bits of information. The thing to remember is that both the client side code (web page you interact with) and server code is written by the same people. So whereas in our example, the shop keeper had to give you the paper, and you had to choose to return the paper, this behavior is automated by the seller, and the seller doesn't have to tell you what they are maintaining about your visit. The only authorization you have when you enter a store is \"do you want to receive papers that remember you and enhance your experience?\" (do you want to enable cookies?) Nowadays these cookies maintain MUCH more information than people may like, but they can only collect information from you that A) the browser will give freely or B) interactions with their site This is why it is important to check what information your browser freely shares. You can modify this to keep a stronger privacy and ensure the only thing sellers are taking from you are interactions with their website. Edit: note that one of the features of private mode or incognito mode is limited cookies. Some maintain the cookies until you close the browser, some will not save them at all. But they never use existing cookies. Browse around on some of your favorite sites in private mode and interact a bit. Leave the sites (maybe close the window and reopen in private) and come back and notice how many quality of life features disappear. The sad part is that most sites are hardly functional without cookies. Simply disabling them isn't really an option for most users."
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