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dgjfiv | how do programmers know where to look when updating apps? | For example the latest Reddit update is this one. “Fixed an issue where clicking links would cause the app to crush” how would they know where to look to find the code that is causing issues ??? | Technology | explainlikeimfive | {
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"They start by looking at the clicking links section of the code and reading it for potential issues. Then they make a change and see if that fixed it.",
"System generated crash reports, user submitted bug reports, internal testing teams etc. It usually starts by someone experiencing unexpected behaviour. Then either the user, tester or system report will alert the company that there is a problem. Tech people will try to replicate the problem and determine which bit of code is responsible for the problems. They'll make a change, test and release the fix. Though generally many bugs are fixed and grouped together in a single release so you don't have to update the app several times a day/week.",
"Mostly 3 ways. 1) By looking through the section of the code that handles the process that is crashing. 2) By looking through the logs to see if there are any exceptions, errors or information that can help track down what area of the code is causing the issue. 3) By running the app through debugging software that can give tons of information on what's going on with the code as it's being used. Sort of like the above \"Looking through the logs\" method, but with tons more information."
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dgjxa3 | Do people who edit videos (to remove something on the scene, for example) need to work at each individual frame/second? | Technology | explainlikeimfive | {
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"Most of the tools you use in photo editing you can use in video. The difference is you need to animate the effect over time. So if a part you're painting out changes from the beginning or the shot to the end of the shot, you move the effect, or the edges of the effect, from point a to point b. Adjust in the middle as required. Computers can automate a lot of it. Faces? A computer can recognize a face and paste in your new face effect on top and track that effect all over the screen (FaceTime and other video chat effects do this in realtime, automatically)"
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dglfyx | Why can houses being built be rained in and on and it not be a problem? | Technology | explainlikeimfive | {
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"Assuming you're talking about the wood-frame construction typical of the United States and Canada (which is used to some extent all over the world), the answer is that all the materials used in that phase of construction are rated for exposure to the elements (for a limited period of time) without being damaged, rotting or fostering mold. For the plywood sheathing for the walls/roof and for the subfloor, that means these materials are all \"Exposure\" rated. This is distinct from \"Exterior\" rated, they won't stand up to being permanently part of the exterior but they're fine for a few rainy days. URL_0 If you do get extended rain or snow, you could indeed have a problem. Depending on the phase of construction the builder may be able to cover the materials with tarps or plastic to mitigate this, but for major projects the PM or foreman or construction manager needs to keep a close eye on the weather, to avoid having to rip out and replace materials that can't be sufficiently protected. At some point, of course, you'll need to start installing materials that aren't exposure rated. That happens once the rest of the structure is complete enough that it can be \"dried in\". For a wood-frame building, this means the frame is completed and all walls and the roof have been covered with (exposure-rated) plywood or OSB sheathing, and tar-paper, roofing felt or equivalent has been applied on top of the roof sheathing. At that point, door and window openings can be covered with plastic sheeting so that interior rough-in work can be completed and interior finish work can begin. Doors and windows can be installed at this time, while insulation boards (r-board, rigid foam insulation, there are various types) are installed over the OSB panels on the walls. The exterior can then be completed with the final roofing (tile, shingles, etc.) and exterior cladding (vinyl siding or similar). Source: framed houses for a while before I joined the military, worked in the construction industry for the US government after I got out, do a lot of DIY projects for myself."
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dgnwhb | How do barcodes work? | Technology | explainlikeimfive | {
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"They’re Morse code for scanners. The width of the bar and the amount of space between them can give information. There are many types and styles, but at their most used (products at the store) they send the UPC # of the product. The computer does the task of looking up the number to find the name, price etc."
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dgpyqp | How are millimetres of rain measured? | Title. 10mm isn't much but 10mm of rain is a fair amount. How is this measured? | Technology | explainlikeimfive | {
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"Any straight sided mm-gradiated cylinder. Diameter wont matter provided it is straight and not funneled/flared. A wider container catches more but needs more to fill to the same depth, as this relationship is linear for this shape ,we ignore it. Edit: my answer describes a basic type you might have in your garden. See the other excellent responses for more precision devices.",
"There are two major kinds of precipitation gauges. One is called a tipping bucket, the other is called a total precipitation gauge. Either type of gauge is installed in an open area and surrounded by a windscreen. The windscreen is designed to deaden the wind around the gauge, so that rain doesn't blow past the opening. A tipping bucket has two tiny buckets inside of it on a fulcrum. When one side of the bucket fills, the bucket tips over and empties, so that the other side can fill. Each time the bucket tips over, a switch closes, and the data logger records the tip. The bucket is extremely small. Like, 0.1 mm of rainfall makes it tip. They're useful for figuring out rainfall intensity - which is the rate at which rain is falling. A total precipitation gauge is a giant bucket on an extremely precise scale. Water falls in, the scale weighs the bucket. The scale is calibrated for the diameter of the bucket, to work out the mass increase and translate it into a depth. The scales are so precise, you use pennies to calibrate them. Those are kinda the basics. My source in this is that I used to install weather stations for work.",
"Imagine a large flat plate that catches rain and funnels into a tall narrow graduated cylinder. All you need to know is how much rain you collected and how much surface area you collected it off of ( and, optionally, over how much time). Since a millimeter is tiny, you can scale the surface area of your rain catcher up to be as enormous as you want."
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dgq0xn | When modern computers connect to Wi-Fi, do they still essentially do the same screeching thing as dialup, only quicker and silently? | Technology | explainlikeimfive | {
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"Sort of yes and sort of no. That was essentially a handshake: the two systems negotiating what connection characteristics, communication protocols, etc., they could use to talk to one another. That still happens, but the process is very different. Modems screeched and shrieked because they used sound to transmit data--they worked over the standard voice phone lines--but wifi uses RF signals instead (and modern networking software uses electrical pulses).",
"The screeching noises from dial-up was known as a handshake - it's the two devices figuring out what they're capable of doing so they can find the best common ground for communications. This occurred because dial-up was limited to a range of frequencies within human hearing capability since they had to use audio telephone lines. If you picked up a handset while a dial-up session was connected, you'd hear what basically sounded like static as the modems talked to each other - the audio didn't stop, the modem just stopped sharing it. Handshaking is an integral part of ALL networking, and basically everything does it. The process will vary from technology to technology as to how it's implemented, but it's basically a device saying it is present and looking to connect, another device acknowledging that connection, and then a series of exchanges to find out the most effective way to communicate given the restrictions on both devices. Here's an article talking about how wifi devices sort out encryption between them - [the 4-way handshake.]( URL_0 )",
"Not really. Dial-up is what you get when you want to send 1's and 0's, but you're told you're only allowed to send sound. So it literally worked by turning data (1's and 0's) into sound, and then from sound back to 1's and 0's. The screeching is what you get when you play the sound out loud. With modern networking tech this intermediate conversion into sound no longer exists. As an interesting exercise you could probably come up with some sort of \"audio visualization\" of WiFi signals as sound, but it not be a natural artifact of the communication protocol.",
"Yes they do, except instead of using the phone to carry the transmission it uses the WiFi frequency. But it’s really the same thing, just faster."
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dgq21o | How was the electron beam in CRT televisions aimed and moved with such speed and pinpoint accuracy? | Technology | explainlikeimfive | {
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"This is really interesting, actually. The timing was driven by the 60hz ac power supplied to the TV set itself (50hz in PAL countries). Analog circuitry took this timing and, in conjunction with the analog radio waves received, scanned lines and frames (called fields)."
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dgs35l | Can fighter aircraft detect when they’ve been “locked on” like in the movies, if they can, how do they know? | Technology | explainlikeimfive | {
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"Yes, it's absolutely possible for a fighter craft to know it's been locked onto. In order to home in on something, you have to know where it is, and one way to know where things are is to use *radar* -- that is, send out a beam of radio waves that bounces off of objects and comes back to the transmitter, painting a picture of what's around it. A radar system has to scan the entire sky, so the number of times the radar track hits a target aircraft in a minute is relatively low. When a radar system sees something it wants, it turns on a different radar that scans much more quickly to provide more accurate tracking data to the missile. Aircraft can determine how quickly they're being painted by radar; if they're being painted very rapidly, that probably means a radar-tracking missile has acquired them. There are other types of missile guidance that are harder to detect; heat-seeking missiles, for example, don't rely on signals bounced off the target, so an aircraft can't know one's on its tail.",
"Think of radar like a flashlight in a Dark room. You can see what the flashlight beam is on, but the flash light can be seen from a long ways off. When the radar warnings detect radar that is of a certain type, the pilot can be alerted. The bandwidth of energy of a radar emitter have a specific fingerprint making them pretty easy to identify.",
"I'll add some more to what others have said. Modern fighter jets (3rd gen and onwards) are equipped with an RWR systems (radar warning receivers), which are essentially a set of antennas mounted around the aircraft. Those antennas pick up radar signals, identify them and display them to a pilot on a screen in the cockpit. RWR system not only has a capability to detect a lock, but it also picks up all types of radar signals, so it can also be used to locate a radar source which isn't locking you. NATO use a code \"nails\" to describe a regular radar signal and \"spike\" to call out a lock. It's important to remember that the only difference between a lock and a normal signal is focus and intensity, so the RWR can easily recognize between the two. Now, the more complicated bit is that modern fighter jets are equipped with a system called TWS (track while scan), which allows to lock an aircraft without \"spiking\" it. So a locked plane will still receive a \"nails\" signal but won't recognize it as a lock. On top of that, Fox 3 missiles (common nowadays) are equipped with their own radar, and don't rely on a donated lock to track their target, therefore it's entirely possible and common to fire a long range missile without actually locking the target. Such target would only receive a lock warning once the missiles radar activates, which leaves little time for reaction. All of that above refers to radar guided missiles. Heatseaking missiles (much shorter range) do not send radar signals and are therefore harder to detect, though if you're close enough to be on a receiving end of one, you propably have visual on the enemy and you're able to visually identify a launch. Some aircraft (e.g A-10, C-130) are equipped with heatseeker detection systems but they're relatively rare. If you have any more questions about modern (or vintage) air combat, fire away.",
"If I shine a flashlight in your eyes, do you know I'm shining a flashlight into your eyes? Yes, if your eyes are open and the light being emitted is a frequency your eyes can detect. RADAR is an acronym, standing for radio detection and ranging. Radio waves are electromagnetic radiation, like visible light. If an aircraft has been 'locked on' to by a tracking RADAR, that means (in a simplified way) that a 'flashlight' of radio-wave light (it can also be done with lasers, some using infrared light, aka, LIDAR) is being directed at the aircraft and is tracking the aircraft as it moves -- as a target it has been 'painted' or 'illuminated.' If the aircraft has sensors which are sensitive to (can pick up) the frequencies of radio waves (or infrared laser) being used, then yes, it can detect the tracking, like picking up an FM radio station. ETA: SPEEEELLLINGK",
"Radar can be detected. It's basically radio waves, we've been able to triangulate the position of radio emitters for decades. The British found that out the hard way in the Falkands War. They went down there with active radar on nearly everything they had but the Argentines had an American-made AWACS (Airborn Warning and Control System) that could detect active radar from twice the distance that radar itself could detect things. This is why the Argentine airforce despite being outnubered and outdated could inflict so much damage on the British naval forces. the Argentines were literally hunting for sources of radio transmission and the British had them equipped on everything they brought",
"Yes. Fire control radars used for tracking are like a flashlight. If you're lit up by the flashlight beam, then you know that you're being tracked.",
"Here in late 2019, you can't fool a heat seeker with a \"hotter\" source. You CAN make your decoys mimic your engine's heat signature. The best you can hope for, with \"dumb\" decoys, is to blind the heat seeker. SOURCE: never flew a plane. Don't know jack shit about how things work. Broke my thumb with a big Estwing hammer. Read a lot of scifi.",
"Also, it's not just fighters that are equipped with sensors to alert them that they have been locked on to. Pretty much every military aircraft made in the last few decades and many ships and ground vehicles have the same suite of sensors"
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dgvlty | When my car is turned off, the gas gauge needle is well below the empty line. Does this position of the needle represent “true” emptiness of the tank, or does the line represent this? | Technology | explainlikeimfive | {
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"To know the fuel level. A float, like in the back tank of a toilet is used. It send a electrical signal to the needle on the dash of the car depending where the level of fuel is in the tank. Once the car is turned off the electric signal stop & the needle goes to let's say negative 5 on a scale of - 5 to 10. 10 being full tank. If the needle only went to 0 there would be no wiggle room for reserve fuel, and slop in the needle, when the guy who installed the needle to have it totally right on zero. etc. Your car is not totally out of fuel when the needle get to the zero line. It's just time to get more fuel."
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dgvnqs | How to use the M (memory) buttons on a basic calculator. | I use pretty basic calculators at work to do a lot of simple statistics and I’m always writing down the numbers I get after each part of the equation. I’m pretty sure there is a way to do all of this without having to write anything down, but I was never taught and never learned how to fully use the other functions of a calculator. Help? | Technology | explainlikeimfive | {
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"It depends on the calculator, but some work like this: The memory can store a single value. This value starts off as zero. The M+ button adds the currently displayed value to the memory. That means if the memory was previously clear, it now stores that value. M & minus; subtracts the currently displayed value from the memory. MR displays the contents of the memory. The value in the memory remains in the memory. MC clears the memory, resetting it to zero. So, here's an example of how you could use it to work out the hypotenuse of a right-angled triangle where the other two sides are of length 5 and 12: (memory initially clear) 5 & times; 5 = (value displayed is 25) M+ (memory now stores 25, and 25 is still displayed) 12 & times; 12 = (value displayed is 144) M+ (memory now stores 169, and 144 is still displayed) MR (display changes to show the number in the memory the) & radic; (display shows the answer: 13) At the end of that calculation, the memory still contains 169, which you can recover again by pressing MR, or delete by pressing MC. Some calculators might have buttons to swap the displayed number with the number in the memory (so instead of losing the displayed number, as MR does, it replaces the number in the memory) or ways of storing and recovering more than one number. Of course, you wouldn't do something as simple as this using the memory, but this illustrates the idea. A more realistic usage might be adding and subtracting the results of several complicated calculations."
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dgz5w6 | Why is there a delay with connecting a Bluetooth device to a different device? | If you connect for example a speaker to a phone regularly. It will pair in 2-3 seconds. If you try and connect it to a laptop afterwards, the speaker will pair in 6-7 seconds. Now if you suddenly change and regularly connect the speaker to a laptop instead of the phone. Vice versa will happen. Why is this? | Technology | explainlikeimfive | {
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"When a device changes Bluetooth association like you describe, two things are happening. It's terminating the connection to the first device, and performing the handshaking protocols to connect to the new one. If it isn't actively connected to a different device, there's nothing to disconnect from."
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dgzoc7 | How does fiber optic internet work? | How is data turned into light and how can data be transmitted with light? | Technology | explainlikeimfive | {
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"Fiber is just a transport medium for light, just like how copper is a transport medium for electricity. Within some manufacturing specs, intrared light will travel down a fiber optical cable as it snakes and bends through (typically) underground conduits and comes out the other side without much distortion. So rather than treating voltage vs no-voltage as 1 and 0 for binary transfers, we treat light and no-light as 1 and 0 instead. And now we have a means of sending and receiving data over longer distances than we can with copper (while retraining signal integrity). Over short distances or where running lots of strands is reasonable, a single connection will be made of 2 fibers, one for transmit and one for receive. Alternatively two different wavelengths of light can be used, one on each side, and a single strand of fiber can be used in both directions. Most \"fiber to the home\" installations do that."
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dh2fj6 | Why do antivirus programs "quarantine" threats instead of just removing them? | Technology | explainlikeimfive | {
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"It basically comes down to: *they could be wrong*. AV programs use predictions as one form of detection. In case this prediction fails, the program does not delete the file. Allowing the user a chance to recover it.",
"No program works perfectly. The people who make antivirus programs can’t guarantee that the ONLY things their programs will react to are real threats. They do the best they can, but something that’s not meant to be deleted might be caught. So they put in a fail safe. The program quarantines everything it thinks is dodgy...but a human has to look at all of the quarantined stuff, and confirm that it IS all dodgy, before anything can be permanently destroyed.",
"Threats can sometimes hold your files hostage or sometimes they can be a false positive. So if it automatically removed it, something might not function correctly."
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dh4qcj | How are "binned" CPU's or GPU's different from their "lower-quality" counterparts? | When a chip manufacturer makes a chip like a CPU, they occasionally "bin" these chips. Some of them are inherently better than others. What about those binned chips makes them better, though? If I were to take two CPUs with the same make and model and crack them open and smack them down under a microscope, what about the binned CPU would make it better than its lesser sibling? | Technology | explainlikeimfive | {
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"CPU making isn't a perfect process. A lot of it relies on purity of the silicon wafer that's grown in a lab. Impurities in the wafer may degrade performance. Secondly, the lithography process in which the chips are made isn't perfect. It relies on the traces to be etched on to the silicon by exposing it to UV light. Think of an overhead projector in school with a transparency on it. The areas that are black on the transparency don't react with the solution the silicon is submerged in while the areas that are clear cause the solution to react with the silicon. A CPU maker ideally wants 100% of the chips on the wafer to work, but some of them don't get etched correctly so parts of the chips get disabled and maybe you get an i3 instead of an i7, or maybe you get a 2070 instead of a 2080.",
"the chips coming out of a generation but different amount of cores are same blueprint. The blueprint makes...let's say 8 cores. When the chip factory makes cpus using the blueprint, some cpus come out defective. A 8 core cpu came out with only 5 good cores. Rather than throwing those in the trash, the 4 cores are chosen and marketed as a medium tier 4 core cpu. If all 8 cores came out good, then it's sold as a 8 core cpu.",
"Everybody who’s posted so far has part of it correct, but they’re missing what enthusiasts are looking for. Sometimes, the manufacturing works out better than expected. Rather than allowing the price on i7s to go down due to increased supply, they’ll lock out extra cores/cache/whatever, and sell a perfectly good i7 as an i5. Sometimes, particular runs (identified by serial numbers) are known to have come out better than average. You buy an i5, and have a decent chance that if you unlock the i7, it’ll still function perfectly well. Because it was only put in there because the i5 “bin” wasn’t full enough.",
"CPUs are tested when manufactured. Depending on the speed they safely hit before giving errors or which cores or threads outright fail due to a manufacturing defect, a chip might be a core i3, i5 or i7 of varying speeds. Sometimes you get lucky and the chip actually runs well when overclocked, sometimes you don't get lucky.",
"They are binned if they are purposely made to get lower results. For example processor x fails the test for x processors if they bin it they label it as processor y and disable some parts. So basically you get processor x but its only possible to use it as processor y",
"So you make 1000 CPUs, but you have to test them to make sure they all work. If they pass all of the tests they're great quality and get sold as A tier components. If they can't quite pass all the tests, then they'll get ranked as a B tier component and so on. All of the components as basically the same, but for various reasons the A tier perform better than the C tier.",
"Random variation in the materials and process. If you make a thousand burritos, you might find a few don't come out as good, and a few are exceptional. Even though you follow the same recipe every time, you can't control every variable, like what the weather was like the week before your peppers were harvested, or what the soil PH was in the field the wheat for your tortillas came from. CPU manufacturers will spend billions on trying to get the best results consistently, but there are dozens of different steps, and it can be very difficult to figure out what you did differently that made an improvement or caused a problem."
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dh4sxx | How are sports broadcasters able to pull accurate and very oddly specific stats instantly about what has happened on screen? | Technology | explainlikeimfive | {
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"They have a pretty significant (and good!) research team working for them behind the scenes before and during the game that feed them this type of info. They also have lists of players, stats, and all sorts of stuff sitting in front of them in paper and on computers to give them all types of info when events occur",
"Sport announcers are only a part of a larger team. The team includes a director and many researchers. When a play happens, the researchers start to look up facts relevant to the play and the info is sent to the announcers. The director might have some ideas and asks the researchers can if they can find a stat of the thing that came to his mind. For example, if there is a fumble off a punt, all the researchers will start to look up punt fumble return stats, such as how the team ranks compared to other teams, find out who has the most punt return fumbles, find out the temperature of the game when the last punt return fumble took place, etc.",
"High quality broadcast teams have skilled spotters and research teams that feed them stats through the game. Poor ones, like the ones in Canadian Football, will have pregame research done on a player and regardless of what happens, only ever talk about that one player they researched. Even if the game doesn’t dictate they put the focus on that player."
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dhbe7u | How does the “overhead car view” camera work? | Technology | explainlikeimfive | {
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"Some software stitches together all of the other camera views to make a view of the whole area around the car.",
"Look carefully, you can't actually see anything on top of the car (it's just a stock image to add perspective). There are a bunch of cameras on the sides that have their images stitched together to give what is around the car.",
"Can someone explain this question to me, does it mean Google Maps Street view why the cameracar isn't visible?",
"I have a Nissan Qashqai with 360 degree view.. there are cameras in the front grill, rear tail gate and pointing down from both wing mirrors. The picture of the top down car on the screen is just an imposed graphic, not the actual car and the feed from each camera is stitched together in the right place according to the car graphic which makes it look like a top down view."
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dhd4s8 | how exactly a digital camera works. I understand that it's a lens that reflects light but then, how does that get out through wires then into a piece of digital file? | Technology | explainlikeimfive | {
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"A lens refracts light. It creates a small upside down image. It does so on to a sensor. Which is actually a whole collection of small sensors. 16megapixels = 16,000,000 individual sensors. Each one reads the piece of the image that falls on it, recording its brightness and color. More photons hit the sensor the brighter the piece. And color of the light changes the voltage output(I think its voltage). All the data is sent to the computer and is processed into an image that you can see."
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dhe2aq | Why are most coins in the world circular? | Technology | explainlikeimfive | {
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"It is a convenient shape, for stacking, for machines (counting and vending). A circle is the same size in every orientation you take it",
"It is a security measure. Coins used to be a specific amount of precious metal, gold, silver, or copper usually. People used to \"clip\" coins, shave off a little bit of the metal to keep then try to spend the coin at its full value. You do that enough times and all those little slivers can add up. Circular coins make this harder to do, as the round shape makes clipping more obvious and you can only take a small amount. Later, ridges called *milling* were placed on the edge of the coin to make clipping every more apparent.",
"In addition to the other points people have made, round shapes don’t poke you, don’t poke holes when in you pocket or purse. Also sharper corners would wear down over time.",
"It's like that for a few reasons. In the older times, coins would be stamped and formed by pressing a bit of metal, so it ended up in a shape that would resemble a circle (imagine pressing a bit of dough with a stamp, the corners will be rounded, or it'll be completely circular. Currently we have circular coins for either cultural reasons (they've always been like that) and because it is convenient. A circle is a very convenient because it has no corners which may be weaker, it has only one orientation when flat, so it can be stacked and carried easier and it certainly doesn't poke you. Also, it can contain sizable detail inside of it without using as much material as a square coin would. A number for example of equal size on two differently shaped coins would consume less material on a circular one (unless it's shaped around the number).",
"In 1969 the heptagonal 50 pence coin was introduced in the UK. A pressure group, the 'anti-heptagonists' protested against it. Their leader Essex Moorcroft said \" I have founded the society because I believe our Queen is insulted by this heptagonal monstrosity. It is an insult to our sovereign, whose image it bears.\" [ URL_0 ]( URL_0 )",
"Judging from [this picture of a Roman coin]( URL_0 ), that appears to be (roughly) the shape you get when you squeeze a bit of silver in a press.",
"I bet you posted this after todays certain post, huh. [ URL_1 ]( URL_0 )",
"European coins used to be round for the same reason pizzas are round. If you want to create a roughly uniform shape from a ball it's far easier to make it a flat disc. As european coin making frequently relied on making coins from blanks that had been repeatedly hammered to make them flatter the round shape was the easiest to produce. Chinese coins tended to be slightly thicker, very small and fully cast. To get around the problems with casting and later keeping them from getting lost chinese coins had a square hole in them. This square hole allowed them to be securely mounted while the mold-edges were filed away, and then you could thread them on a string to prevent them from getting lost.",
"All of those reasons, plus you also get the most area for the least material, so you have plenty of surface to imprint your security image on. As metals have become more expensive than the currency they represent coins have got smaller to save on material and the circle is the most efficient use of material to get large area from less material.",
"We have a saying. Money needs to roll! ( we need to spend money) We can't fucking roll money if they are square or triangle now can we? The guy who invented the triangle way back when was stoned to death by circular shaped stone things by the inventor of the stone wheel.",
"Some answers here are incorrect. It's not for security reasons, as shaving a circular coin is not particularly harder than a square one, and they were circular long before people stopped weighing them in transactions. The risk of the coin containing less silver or gold than it should was never a real concern as weighing is easy. Having a recognizable mint pattern on it was more about guaranteeing the composition of it. It's also incorrect that they were pressed. [Plenty of ancient molds have been preserved]( URL_1 ), and we can see it's not the case. In reality it's probably because a a circular coin retains its shape better over time (corners chip easily). It's also another layer of authentication. The most important feature of a coin is that you can easily see its authentic, which makes transactions quicker and more reliable. If I see the [Athenian owl]( URL_0 ), I can safely assume I'm looking at an actual Athenian drachma made of silver. I can weigh it if I think it's a bit worn, but generally speaking it makes things easier. It's easier to chip out a rectangle or a triangle out of a piece of metal, than it is a circle, so that's another aspect of guaranteeing authenticity - that this coin came from a real mint.",
"There are some modern coins that aren't circular...?"
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dhjf61 | How do electric cars save so much pollution even though majority of the power used to charge the cars are generated by coal or other natural gases? | The ratio? How much better are the cars even if they are being charged by those power sources and are they even better? | Technology | explainlikeimfive | {
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"A cars engine is way, way less efficient than a giant power plant. Even if it's ultimately powered by coal, an electric engine is way cleaner than a gasoline one simply because of the scale and the increased efforts to not waste heat at a giant power plant.",
"Power plants get plenty of flack, but the truth is that they're a miracle of modern engineering. Not only are they incredibly efficient (making as much power as possible from as little fuel as possible), but there are all sorts of equipment and processes in place that \"scrub\" the air as clean as humanly possible. Compare this to the combustion engine of your car. It's cheap, highly inefficient, and dirty as all get out. For the exact numbers and ratios, you'll have to do a bit of research on your own.",
"Because electric cars require are much more efficient than normal cars, able to [realize 59-62% grid-to-wheels energy efficiency, while conventional cars only get 17-21% tank-to-wheels efficiency]( URL_0 ). This means that EVs incur far less emissions than a normal car on a per-mile basis.",
"Engineering Explained on YouTube did a video on this. If you converted a Tesla Model 3’s energy consumption to miles per gallon, it comes out to about 133 miles a gallon. Compare that to the best hybrids or gasoline cars. Even if EV receive their power from coal, they are WAY more efficient at using than power than gasoline engines.",
"In general, they're not. When you do an entire life-cycle analysis on electric cars and comparable gas vehicles, there's no clear winner. Some factors people tend to overlook: - Electric Vehicles are heavier than gas vehicles. This means they consume more power. - Electric Vehicles perform poorly in non-optimal weather. Most comparisons are based on Southern California weather, rather than the norm for the rest of the world. - Electric Vehicles require almost twice as much carbon emissions as conventional cars to manufacture. Moreover, these costs are related to the battery - which must be replaced multiple times during the vehicle's life."
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dhjqbd | How come smart devices like Alexa, Google, and iPhones (Siri) aren't triggered by TV commercials that say "Hey Google..." Or "Hey Siri..."? | Technology | explainlikeimfive | {
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"Your \"smart\" device is actually pretty dumb. It's brain power is all in the cloud, so it's relatively easy for it's manufacturer to manipulate. A great real world example is Alexa and South Park's episode about it. The creators of South Park really went out of their way to fuck with Amazon, so the episode was full of Cartman ordering stuff. During the initial airing of that episode A LOT of Alexa's responded to Cartman's voice on the TV and ordered stuff that their owner's didn't want. Amazon has a whole team devoted to this, who immediately sprang into action. During the initial airing of the episode thousands of orders were placed by mistake. By the time of the repeat episode a few hours later, they had already taught Alexa globally to ignore Cartman's voice. A side effect of this, if the guy who voice's Cartman legit tried to order via an Alexa using the Cartman voice, the device would ignore him.",
"This used to happen. So now they transmit a sound that is brief or out of our hearing range that indicates to the smart device to ignore the next signal to activate."
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dho6ao | What are the differences between TN, VA, and IPS panels? | Technology | explainlikeimfive | {
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"text": [
"[See here] ( URL_0 ), not sure if there's a more up to date post."
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"https://www.reddit.com/r/buildapc/comments/92mb7r/updated_monitor_buying_guide/?utm_medium=android_app&utm_source=share"
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dhopvw | How does your phone know what time it is if it's battery dies? | Technology | explainlikeimfive | {
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"In general, a dead phone battery isn't completely dead. It's just very low. The battery still has a bit more power in it, but using it damages the chemistry, so the phone doesn't. Besides that, phones can get the time from the phone network, or the Internet. A sim card isn't absolutely required to interact with the network, by the way. It's required for billing, but for instance emergency services are available from any provider, even without a sim card. I'm not sure if getting the time also works that way or not, but it could be.",
"Clocks use very very little power so the phone shuts down before all the juice is gone, or there is another small battery used just to keep track of the time.",
"Mobile phones, like computers, also have a RTC (realtime clock) that keeps track of that. This part can actually fail since unlike a computer, in which the RTC is powered by a coin battery, it cannot be replaced on its own. This is pretty rare though; I've only seen it twice, and in both cases the phones were more than 5 years old."
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dhpzdt | why are there WiFi networks that still don't provide internet, even at full signal; and what is the point of such networks if not to connect to the internet? | Technology | explainlikeimfive | {
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"Some devices use a temporary WiFi network so others can connect to them wirelessly to set them up. Or it might just be a malfunctioning router that can't connect to any wider network.",
"Communication between devices inside the network. If you have 10 devices(like smart lamps, for example), they can all communicate through the WiFi network, regardless of whether it's connected to the internet or not. The same applies for computer and wireless printers, smart home apps and devices, the list goes on."
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dhsgm6 | How do character models in video games nowadays move so fluently and realistically? | I can tell they probably aren't animated traditionally, so what do the makers of the game do to achieve that realistic movement? GTA and the latest Guitar Hero games are good examples. | Technology | explainlikeimfive | {
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"Many use motion capture software to get a very precise idea of the movements and then just add small adjustments later. Other than that advanced hardware just made fluent and realistic animations easier to achieve.",
"It isn't just motion capture! The technology that drives transitions and blending between animations has improved. As computers have become more powerful, game designers can increasingly use more sophisticated logic to blend a larger set of animations together in real time. Character animations are more memory intensive than you might expect, but modern gaming consoles and computers have far more memory than ever before. Now you can keep things like start and stop animations in memory, ready for use instead of just blending from \"idle\" to \"walk\" like we used to. Little things like this give characters a sense of momentum and weight. Additionally, we can now afford to blend in physics driven animation to help ground animated characters into the world.",
"I think there are motion capture suits they use to make it realistic, basically put the suit on a fella, point a bunch of cameras at him, get him to do the thing you need doing and boom, Put it in some software, rig it on the model and tweak where tweaking's needed and you've essentially got it done. But the stuff needed is expensive so you'd see it more in triple A games. For indie studios that don't have enough for the suits and stuff I think there's plenty of stock animations to base it on and knowing anatomy can help alot too."
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dhuqdp | What makes video game snipers feel so different from game to game? | In Overwatch, I have very little problem aiming as Ana (hitting enemies, I know allies have larger hitboxes), and I can hit bodyshots easily as Widow. In Warframe, I can be flying around as Volt or Zephyr, and can hit headshots on most enemies while going faster than a smart car. In Team Fortress 2, I can't hit anything. I was lucky with a headshot, maybe a couple bodyshots. | Technology | explainlikeimfive | {
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"Hit boxes, default sensitivity, some snipers have bullet drop off, verticality, and different guns .. lots of factors play a role in how comfortable it is to snipe in one game vs another game",
"It comes down to many factors. Big ones tend to be ranges, mouse movement, player movement, and hitboxes. More arcade-y games like tf2 tend to have very fast players which makes sniping far more difficult. It also has tighter collision boxes, which means your targets are smaller anyway. Another big thing is that different games handle mouse input slightly differently, and players who aren't used to it can find these subtle differences very confusing. Yet another thing is the scope of the world - if you compare sniper ranges in tf2 (probably about ten to twenty yards or so) to sniper ranges in ArmA (100-2000 yards), you'll start to see why those two games may feel different. Another one: Bullet mechanics and firing delay. Different games have bullets follow different arcs or even straight lines, and may even have a bit of travel delay. Animations are also a big thing - in less arcade-y games such as the game Verdun, whenever you move your weapon your sights glide slightly in accordance which means that quick and sudden movements result in skewed aim. You have to learn to compensate for this, and it will be different or nonexistent depending on what games you play. Ex: tf2 does not have it, and in ArmA it is very powerful and changes depending on what gun you are holding.",
"TF2 golden rule for snipers. Wait when the target walks to your corsair, don't chase the target with your corsair. It will take time to adapt but you'll become extremely above average. Train a little more and you'll become a pro.",
"Because of differing bullet magnetism valise and hit boxes. Basically, how far away you can shoot from the head and it still being a headshot varies game to game."
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dhyfo7 | Why using RFID on IDs considered a bad idea? | Technology | explainlikeimfive | {
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"text": [
"An RFID circuit doesn't have an on/off button, so it is always triggerable when your reader is in a 1 to 1.5 meter distance from it. It's like you are always holding up your passport for everybody to see."
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di1mfj | Why does speeding up a video cause the audio to become high pitched? | Technology | explainlikeimfive | {
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"text": [
"Sound is waves. Sound pitch is determined by how many of those waves hit you every second. Double the speed of the video, double the waves every second, double the pitch."
],
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3
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di9vk4 | How does capital letters in username not matter? | As title, password is capital & lowercase letter sensitive. Why is username different? | Technology | explainlikeimfive | {
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"text": [
"a developer can set if they want something to be case sensitive or not. Login and user names (not passwords) are usually not case sensitive to make it easy on the user logging in and so that there is no confusion among users of the site about user names. For example, they don't want people to confuse these user names, which all are really similar, if they were case sensitive it would be hell: reddituser, Reddituser, reddiTuser, REDDITUSER, reddituseR, RedditUser -- if it was case sensitive, these would all be different accounts but thats hard to tell. If its not case sensitive, only one user can have the account. and so on... it would be quite confusing if usernames were case sensitive."
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diarpn | How do software developers name their builds? | Technology | explainlikeimfive | {
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"text": [
"Anybody can pick whatever format they want, but in general, versions follow the major.minor.revision scheme. Major: Major, incompatible releases. 0 is for a product not done yet, 1 is the first official release, 2 happens when they basically revamp the product in such a way that it's a new thing to sell. Minor: Minor changes like new features and such improvements. Revision: Bug fixes \"Alpha\" means \"this is an extremely early version of what we want to do, it's missing a lot of functionality, and it probably barely works. Development is far from over\". \"Beta\" means \"this is almost what we want to release. We need the general public to try this out and see if anybody runs into trouble. It probably doesn't work perfectly yet, but this is very close to the final release, and all the planned features should be there.\" \"Release candidate\" means \"this is what we're going to release officially if nothing goes wrong. If it does, we'll fix it and have another release candidate\"."
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dic37k | What is the importance of 7nm processors? | I’m usually really on top of things like this (I’m really into new tech and consumer electronics), but I must have gotten lost somewhere. I see a lot of companies like Apple and Microsoft as well as Youtubers like Linus Tech Tips talk about the importance of the introduction of 7nm (or below) processors, but I have no idea why they’re important and what they add to the future of technology. Does it just result in smaller processors? Better performance? Thanks! | Technology | explainlikeimfive | {
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"text": [
"it's self explanatory. fit more transistors on a wafer and you can make more chips per wafer (each one becomes cheaper) or you can put more transistors on each chip and thus increase processing power while passively reducing heat production and energy consumption (by means of ykno, smaller transistors that require less power). The term 7nm is a myth, though. It refers to nothing on the transistor itself. 7nm AMD is not the same as 7nm Intel which is not the same as 7nm qualcomm. It's just a corporate simplification to sell shit.",
"yes. smaller processors. better performance. imagine drawing a schematic with a bingo marker. your lines will big and fat and you won't be able to make many wires. now use a sharpie. better lines but still pretty fat. now use a fine tip marker. you're able to make more finer lines than ever before. each of those lines will carry electricity. and you can make the components smaller and less distance and resistance for electricity to travel."
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difkyt | Why is the presence of speed cameras always announced by speed limit signs around them? Isn't the point to secretly catch people speeding? | Technology | explainlikeimfive | {
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"The initial purpose of the police is not to catch as many people as possible but to prevent crimes from happening in the first place. When they tell you in advance that there will be speed cameras, you're less likely to drive too fast, which is their objective.",
"Isn't the point to stop people from speeding?",
"There *is* a law in Maryland that they have to be marked with \"adequate notice\". URL_0 It varies by state. As for *why* it's part of the law, there must have been convincing arguments when the laws were drafted. URL_1"
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difmn9 | Why do the cameras at self checkout isles make the person look 10x worse than they do in real life? | Technology | explainlikeimfive | {
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"They're slightly curved, to expand their field of view. That fish-eye lens distorts the image a bit and makes our features look exaggerated. With humans, just a little bit of distortion can make a person look pretty weird, because we're very used to the normal proportions. I've got a longer nose, and some of those lens angles turn me into Cyrano de Bergerac.",
"It does? You mean I don't ctually look like that? Oh, Thank goodness!!!!",
"Another reason is those cameras typically use a sharpening filter to make details pop out. These details help law enforcement identify someone but are also very unflattering by exaggerating any little flaw. I have slight bags under my eyes but grocery store cams make look like Gollum.",
"As someone who use to work behind those cameras and watch grown adults make faces and dance unaware that someone is actually in a dark room watching them act silly... The quality is often crap because the store buys crummy products. As said before me, some tend to have the fisheye effect and others have a sharpening feature... which neither really help with the overall quality. Also, the cameras/monitors at self checkout are often there just to deter theft. If someone is aware that they are being watched and recorded, they are *theoretically* less likely to steal or perform credit card fraud. *former Loss Prevention Officer"
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difnyb | How do phones know the difference between just pressure being applied to the screen, or a finger? | Technology | explainlikeimfive | {
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"text": [
"the way a modern phone touch screen works is by measuring the change in capacitance caused by the presence of your finger near the screen. Capacitance is a measure of the ability for 2 conductors to store some electrical charge between them. For example, if you have two metal sheets laid parallel to each other, and you charge them, then attach an LED, the LED will not immediately go out. some of the electricity stored in the plates will flow to the LED and make it light. Dry plate capacitors like that kinda suck, because the air inbetween is not a good store of electrical energy. To improve the 'capacitance' of the plates, we can add a better 'dielectric' material inbetween them. Dielectric materials are insulating, so the electricity cannot flow between the plates, it is just stored in the dielectric. By using a good dielectric, and rolling the plates up tight into a tube, we can make a capacitor like you might see in a circuit. With that in mind, a phone screen does actually use a dry plate capacitor to sense your fingertip. Since the phone isn't really concerned with the amount of energy it can store, the parallel plates work fine. The phone senses the capacitance of the plates, and when your finger goes near it, the dielectric properties of your finger cause the capacitance to go up. Your phone can detect the change in capacitance, by using the capacitor as part of an oscillator. the oscillator circuit controls its timing by charging and discharging the capacitor over and over. As the capacitance changes, the time taken to charge and discharge changes. this can be measured by a chip in your phone that uses the change in capacitance across multiple parallel plate capacitors to triangulate the position of your fingers and send it to the CPU of the phone. So the chip that senses your capacitance can know roughly how dielectric your finger is, and things that don't match up to that can be rejected. Actually there isn't much that's more dielectric than your skin, so fingerprints show up MUCH stronger than say, the fabric in your pocket. Certain plastics, rubbers, and metals can accidentally set off this system."
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dih3y8 | Why do AM radio stations pause for ‘station identification’ periodically? If they just have to say the station number and call sign, why the need for the extended pause? | Technology | explainlikeimfive | {
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"text": [
"FCC regulations require radio transmission to identify themselves regularly. But why the pause? A lot of AM programming is syndicated nationally, more than one radio station is broadcasting the feed. The pause is used to allow local stations to override the feed and comply with the law. For live broadcasts, they often can't predict when the pauses will occur, so they are extra long to allow time for the local station to react."
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dihtoj | Algorithmic door locks, how do they generate specific door codes based off of a day and time? | I work in the hospitality industry, and my company is looking into using algorithmic door locks for our more remote properties. When the door locks are set up, you enter the current time and date, so there is an internal calendar and clock. These locks will generate a code based off of a customers check in day, time and length of stay. I am assuming there are pre-loaded numbers based off of a date and time. You can then use an app, that will tell you what a specific customers door code is. That customer can only use the code starting at a certain time on their check-in day, and stops working at a certain time on their check-out day. My understanding is, that the app and the door lock have the same algorithm, so the app knows exactly what the lock is "thinking", even though they aren't connected. What I don't understand, is how the code is generated for a specific guest? Especially if they are staying for more than one day. How does the lock generate a "random code" that only works for that customer, for their entire stay and stops working at a specific time on their check-out day? | Technology | explainlikeimfive | {
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"It doesn't generate a random code for the customer's multiday stay, but instead gives the customer a series of numbers, one for each day, so that when their stay is over their numbers are also up and so can't use the lock anymore."
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dij2er | How does a single wire control every pixel an entire TV screen. How can it convey enough information for that many pixels, sixty times per second? | Technology | explainlikeimfive | {
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"If you're talking about HDMI, there are many wires inside, with three separate pairs of wire operating together to carry the image information. The original (2002) spec had each pair carrying 1.65 billion bits per second for a total of 4.95 billion bits per second, but the total, has gone up regularly since to 10.2 (2006), 18.0 (2013) and 48.0 (2017). FullHD is 1920 & times;1080 or two million pixels but usually there are only 24 or 30 full frames per second (60 fields interlaced is the same pixel rate as 30 progressive frames per second). The each pixel takes about 12 bits to describe. Multiplying this out gives 1920 & times;1080 & times;30 & times;12=0.75 billion bits per second. So you can see that a broadcast high-definition picture easily fits into even the oldest HDMI standard. The newer, higher-speed standards have come about because of things like 60 progressive frames per second, 4K, 8K, and other quality improvements. As for how the cables can handle such fast data rates, they are manufactured using shielded twisted pairs and mostly only at short lengths. While HDMI seems faster than similar wired Ethernet cables, mostly that's because Ethernet is usually designed to work over long distances and its cables aren't shielded.",
"Short answer: By turning on and off incredibly fast. Let's take a radio signal running at 100 kHz. That's 100,000 waves every second. Let's say you can communicate a pixel with a hundred waves. That's still 1,000 pixels. Now, 100 kHz is super low for TV. 10 mHz is more reasonable. That's 100,000 pixels. Easily enough for old TV. Now, consider that you can have almost as many frequencies as you want running through a single cable. Each frequency can carry a *lot* of pixels. Collectively, that's a lot of data.",
"There are several wires inside an HDMI cable, and just like you can download gigabytes of info per minute, the cable can send a lot of information in a short time. \"Digital\" TV means that the screen has (computer) memory and it matches each pixel to a memory byte, so 60 times per second the pixels just glow according to the brightness that's in their associated memory. So the job of the HDMI cable is to convey to the screen's memory which areas of the screen should be white, black, or other colors. The information is [compressed]( URL_1 ) via the MPEG standard, so with the reduced size from the compression it can be transmitted across wires much faster. Part of the compression is that only the parts of the image that \"have changed\" are transmitted, which is why a poor internet connection looks [like this]( URL_0 ) and not like static like with the old analog TVs. Otherwise, 60 times / second is \"slow\" in terms of electronics speeds. Computer processors nowadays operate at 3,000,000,000 times per second.",
"in the simple sense because it's transmitting data fast enough for the tv to update the entire screen 60 times per second. a more complex answer would be that the one hdmi cable is actually many wires internally, and each wire has a different role. some send data, some are for power and ground, and others are for protocol specific things."
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dijjty | Why do phones lose connection when flying? Isn't airplane altitude well within cell tower range? | Technology | explainlikeimfive | {
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"For a couple reasons. 1. As u/AllReligionsAreTrue guessed, towers focus their antennas towards the ground, so they send and receive less well to things at high altitude. 2. Your phone is a relatively low power transmitter, and you're inside a sealed metal tube. That's pretty much a worst case scenario for trying to get a signal through. 3. The cell network *really* can't handle a device moving at very high speed. Cell service works by handing your call off from tower to tower as you move, and there is a lot of complicated techno-wizardry that goes on to make that all seamless to the user. That means there are a lot of assumptions made in the system, and one of them is that you won't be moving at mach 0.8 and bouncing to a new tower every 10 seconds. Start doing that, and the system stops working.",
"* airplanes fly 6 or 7 miles above the ground, which is at the practical limits of a mobile phone's range * phones are digital, so even a little loss of signal results in total loss of communication * big metal tubes block a lot of the signal * you are flying so fast even if you do get a signal you will lose the connection to that cell tower in a matter of seconds * coverage is clustered around cities and highways, planes often fly over areas without coverage * cell towers are optimized to receive ground signals",
"Altitude, signal directionality, and simply less cell tower density as a plane flies over more sparsely populated areas."
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dipgdv | Why can’t displays/monitors show the color true cyan? | Technology | explainlikeimfive | {
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"The term \"true cyan\" is a little misleading. Cyan is a color, and there is a narrow range that's called cyan, and part of that range isn't displayable on monitors. [This graph]( URL_0 ) shows the overall space of colors and the triangles producible with a monitor (most of which are a sRBG triangle). There is some cyan outside this triangle, but also some purple and coral.",
"The majority of humans have 3 types of cone cells. A perceived colour is how much each type of cone cell is stimulated. Each one has it's [response curve]( URL_1 ). The cyan wavelength stimulates mostly S & M cones. It's possible to \"fake\" that colour by using different wavelengths with the right intensities so the cone cells have the same response. We have 3 cones, so we can reproduce a large portion of the possible tristimuli with 3 wavelengths. Hence the use of 3 primary colours (RGB in additive synthesis, CMY(K) in subtractive synthesis). But it becomes much more complicated once you go beyond ELI5. [Relevant XKCD.]( URL_0 )",
"This is a limitation of additive color. When you start with black, adding light in the form of red, blue and green, colors on the intersections of the color wheel are hardest to produce (cyan, yellow, magenta). Black, which is the absence of additive color is just the screen, hence even harder to produce. With subtractive color: when you start with white, you take away light by adding pigments. The hardest colors to produce here are green and orange, which is why most commercial printers will use a “spot” color to better render these colors. And white is just the absence of pigment, so the best white is the the “whiteness” of the paper. It’s also why black is part of the process as CMY will not produce a true black."
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dirl6n | How are IMEI numbers tracked? | > Someone mentioned IMEI pings do not carry location data with it so it seems that someone can avoid tracking as long as they keep location off. Of course you can use nearby cellular towers to figure out a general location as well but what happens in the case where location and cellular data are turned off + there is no inserted sim. > Will wifi be enough to track the device - without the use of "find my iphone" or google's version for android (assume those aren't set up) and without the use of 3rd party apps sending that information (although OEM apps are valid). In case my questions below aren't clear, the above may better describe what I would like to know. --- I'm relatively tech savvy so you can ELI18, instead. I'd like an actual technical explanation, if possible. Things I want to know: How is IMEI transmitted: through wifi, cellular, or location? If I have just wifi on, does IMEI do anything? If I have just location on and no wifi or cellular, can I be tracked through IMEI? How about location + wifi? Does IMEI itself give location info? Or is IMEI used just to identify an item and then location + cellular is used to track? How about when wifi/cellular is active but location is off? How does IMEI get registered? Does a device need to be first connected to the internet and connect to the servers of the device manu to register? Is it technically "off the grid" if it has never connected to the internet. | Technology | explainlikeimfive | {
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"okay so I am just going to answer your questions and not go much further then that.... IMEI's are only, by default transmitted through cellular. If you have wifi on you will likely still broadcast to the cell tower unless you specifically turn off the cellular antenna. If your phone is an \"airplane mode\" and you have turned on your GPS antenna then you should be able to use GPS just fine, but it might be slower then using network based techniques. If you turn on the wifi the GPS could be faster, but you can't be tracked through IMEI if your cell antenna is off. No the IMEI itself cannot give a location. GPS isn't needed to determine your location at all. that can be triangulated based on your signal strength based on your proximity to cell towers. Your phone MIGHT transit metadata to that could conceivably have GPS coordinates to a cell carrier, but as far as i know that is unlikely. Generally, for the purpose of figuring location triangulation is good enough. There really is not \"registration\" IMEI's are serial numbers and their can either be a database of them that a carrier is allowed to use and then once a sim card handshakes transmits that IMEI the carrier will say \"this IMEI is good/bad\" and that is the whole of the registration process. Some carriers do not care what the IMEI of a device is and will not check it against any database EXCEPT for the lost/stolen/not paid for blacklist. NOW I AM SURE that there are people out here that are going to throw a million conspiracy theories out here. I am just telling you how its meant to work. Law enforcement will regular set up fake cell towers to intercept metadata and unencrypted info associated with any IMEI's that connect to the fake cellsite, but in reality that data is just limited to the unencrypted metadata allowing them to instantly collect that data without a warrant. That data does should not contain location data (it is not required by organizations that set the GSM standards) Also your IMEI is regularly transmitted to third party services like google and apple to identify your device easier. But that data should be encrypted but obviously available with a warrant. Technically, so long as you never activated the cellular radio on the phone or kept it off regularly it would remain \"off the grid\" or as close a possible. However third party services might still see your devices IMEI. I would say that if you kept your cell antenna off it should remain off the grid even if you use wifi and GPS as you could not have your location \"triangulated\" based on cell tower location. Simply removing the sim card is not good enough, the cell antennas MUST be off.",
"IMEI is the International Mobile Equipment Identity number. it's basically just the serial number of your phone.",
"IMEIs are specifically for cellular communication. The majority of non-cellular wifi devices don't even have an IMEI to send."
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dix2l9 | How can web browsers securely store passwords, if other browsers can import them easily? | For example, I save passwords for web sites on Google Chrome, and installing Firefox offers to import those passwords. If Chrome was storing them securely, surely Firefox shouldn't be able to access them so easily? | Technology | explainlikeimfive | {
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"They are not stored securely. But, they are stored conveniently. If your security risk is from someone with physical access to your computer, **you are screwed**. If your security problem is some script kiddie in Belarus, then the key is to have long, random, unique passwords. This is the problem for 99.4% of the people on the Internet, so that's the problem the browser folks set out to solve."
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dj58zq | Asymmetric cryptography | Hello everyone, I'm currently trying to understand the system behind asymmetric cryptography or public-key cryptography. I know how it basically works, but so far I'm not really understanding it in depth. The metaphor I stumpled mostly upon ist the one with the lock and the key. A sends out his public key - the lock - which, as soon as it is closed, can only be opened with the key that A keeps - or be decrypted with his private key. My problem with this metaphor is, that from my understanding, you don't "lock" something inside a box - like a letter in plain text - but rather "transform" the words in the letter in some gibberish which doesn't make any sense until you "transform" it back. So for me I explained it to myself like a math equasion: You have a simple number and transform it into a long term with variables, that only you have the values for. But how is it possible \- that you can give out a public key, which is not decryptable without the private key, but still encrypts the message in a way it can be perfectly decrypted by the right key without knowing it? \- that you can't decrypt it with the knowledge of the public key? If it has enough knowledge about the private key to encrypt something for it, shouldn't it be able to also decrypt it? & #x200B; Maybe I'm on the wrong track with thinking about this like a mathematical problem. If so, please let me know. | Technology | explainlikeimfive | {
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"The lock analogy is an analogy, that's not how it works (which is actually the case with all analogies). Some problems in math are easier than others. If I have two numbers A and B, the best algorithm for multiplying them to calculate C is much easier than the best algorithm for factoring C into A and B. This isn't a \"secrecy\" thing, it's a property of mathematics. Knowledge of mathematics could change, and in reality quantum computers might actually change our understanding of the best factoring algorithms. You're right to think of this as a math problem, but the analogy doesn't have enough fidelity to do that wort of analysis.",
"You're right that it's a math problem--the key and lock metaphor is just that, a metaphor. The basic idea behind all public key cryptosystems is this: You have a message M. I give you a public key k, and you do some math to M using k, making it unreadable. I have the ability to reverse your math with my private key d and get M back, but it's really, really hard to calculate d if all you know is k. The most well-known public key cryptosystem is called RSA, so I'll use that as an example. It's one of the simpler cryptosystems, but the math still isn't going to make sense if you're not familiar with number theory, so this is an oversimplification. You have a message M that you want to encrypt. Think of M as a number. Even if it's a long message full of text and images and video and whatever else, it's all just 1s and 0s--just one really big number in binary. Since M is a number, you can raise it to a power, M^k. This encrypts the message--turns it into another number and makes it impossible to read without decrypting it. If I want to decrypt it, I have to raise it to another power, d = k^-1 , because (M^k )^d = M^kd = M^1 = M. So I choose k to be the public key and tell everybody, and calculate d, my private key, and keep it secret. Everybody can encrypt messages with k, but nobody knows d so nobody can decrypt them. So why can't anybody else just calculate d? I mean, it's just k^-1 = 1/k, right? Well, like I said, I've been oversimplifying. We're not doing normal arithmetic, we're doing what's called modular arithmetic. I'm choosing a number n (which is also part of the public key), and whenever anything gets bigger than n, we're dividing by n and taking the remainder. So, as an example, let's say M is 6, k is 2, and n is 10. M^k (mod n) = 6^2 (mod 10) = 36 (mod 10) = 6--the remainder you get when you divide 36 by 10. (This is just an example so you can see how mod works--k=2, n=10 is not a valid choice of numbers for RSA). But n isn't 10. It's a really big number, the product of two really big prime numbers that only I know. Because of certain properties of modular arithmentic, it makes d = k^-1 (mod n) really, really hard to calculate unless you can factor n. And n is going to be really, really hard to factor. And when I choose n this way, it also turns out that for any M < n, you get a unique M^k (mod n), so it's reversible. So when you want to encrypt M > n, you're actually going to split it into smaller chunks and encrypt those separately. It all relies on certain properties of modular arithmetic that aren't really ELI5. If you're interested in all the details of the math, look at the Wikipedia page for RSA."
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dj5icd | Why aren't electric cars being developed so that depleted batteries can be swapped out for charged ones? | Technology | explainlikeimfive | {
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"There are all sorts of issues with this. First of all battery technology is evolving very quickly. Your swap out idea imagines that these very expensive batteries can just sit around for a while and it won't really matter. But the reality is that a five year old battery is obsolite and you want it to have obtained its absolute maximum use in that time (not be sitting in stock on some garage shelf). Second the batteries are very heavy and very large and travel very fast. Safety means that they thus need to be very well secured which makes swapping them out a difficult proposition. Like imagine if the engine of your car could be removed in 15 seconds. Third these batteries have odd wear characteristics. You wouldn't want to swap out your nicely maintained fresh battery for a two year old one that got slapped around like a model at a Weinstein party.",
"They aren't exactly easy to remove.. Additionally what do you charge people? Could I bring in a 4 yo battery and swap it for a new one at the same price? Will the reverse happen? That's also quite a bit of startup cost for the business that is running this. URL_0 Edit: I have been shown to be incorrect regarding difficulty of battery swap. It seems the only barrier is logistical and lack of demand"
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dj74s6 | What's the point of CVC or CVV om Credit Card? | If online transaction only need card number and CVC/CVV, then when the card is stolen there's no additional security layer? | Technology | explainlikeimfive | {
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"Probably to prevent the card from being used if you only got a stolen number from a website without CVV",
"The CVV/CVC is there to protect against people who get the card number/account information without getting the physical card. In the case that your card is physically stolen, you can just report it stolen and your credit provider can stop all transaction involving the account/card number. Thus even with the CVC/CVV the card is useless.",
"From the CVV, no, that sort of security is provided by a PIN. The purpose of the CVV is if your **number** is stolen, by someone reading the magnetic strip or getting it from a data leak.",
"> If online transaction only need card number and CVC/CVV, then when the card is stolen there's no additional security layer? It depends. Some vendors use AVS (Address Verification) that ends up being mostly invisible to the end user. There's also additional layers like 3-D Secure (Verified by Visa/Mastercard SecureCode, etc.), which may require users to authenticate themselves when using a particular card online. Some banks are starting to issue cards that have CVVs that rotate - Bank of America currently has a pilot program for debit cards where the card actually contains a battery and a small LCD screen, where the CVV changes every 6 hours. Stealing the card number and CVV without physically having the card will mean expiration for that CVV."
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dj76j8 | How do a handful of GPS satellites handle the millions of users every day? | Technology | explainlikeimfive | {
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"text": [
"GPS is a one-way technology. The satellites do not get requests from GPS devices; they broadcast a precise signal that all devices can listen to. Devices can then compare the signals from multiple satellites to determine their location.",
"GPS satellites broadcast information, they don't really receive information (except from very specific things like whoever owns the constellation sending information to them). So they don't \"handle\" any users so-to-speak, they simply shoot out radio waves and users who are trying to listen to it can pick them up and do something with them. It's like radio stations, there is no back and forth communication, just a tower that sends out radio waves that anyone can listen to. Individual users don't send anything back to the towers so the towers don't have to handle receiving anything.",
"GPS is passive. The satellites broadcast a signal for anyone to receive. The GPS receiver can receive these signals from any GPS satellite without sending any feedback.",
"GPS is like radio station. it broadcasts out. it doesn't matter if there's 1 person listening or 10million people listening. the receiver is doing all the work of translating the radio waves into music or data.",
"Same way a radio broadcast \"handles\" users...they don't, users handle them. GPS satellites broadcast a simple signal, basically just their ID, position, and current time, and don't receive anything from GPS devices. The device receives the signal from multiple satellites, and does some math to figure out exactly where it must be."
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dj8wdr | In graphics programming; what exactly is a texture? | Technology | explainlikeimfive | {
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"text": [
"A texture is a 2D image that is applied to a 3D object (could be a 2D object depending on the style of your game but usually 2D uses objects called \"sprites\") to give it some appearance desired by the developer. There's a lot of more intricate details such as texture mapping (this is the actual process used to wrap the 2D image around a 3D object), special texture maps (like bump maps, parallax mapping, reflection mapping, specular mapping, etc) which are used typically in addition to texture mapping to change how an object is rendered on screen, but the basics of \"what is a texture\" is simple a 2D image drawn onto a 3D object. Think of the peel of an orange. The orange itself is your 3D object, the peel is the \"texture\". If you remove the peel in one piece and lay it flat on a table, it's your 2D texture which can be wrapped around the 3D object (the orange). If you wanted to break it down further, the orange color and any coloring blemishes of the peel is the texture, and the bumps you see (the physical texture of the peel) would be more similar to something like a bump map (which can be used to make textures appear to have depth, despite being a flat image)."
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djbapk | Vector Graphics | I understand that the beam is manipulated directly, and that’s what makes it different from raster, but I don’t understand how that would work or why it works and how it knows what order to do things in or why it requires different hardware or anything. | Technology | explainlikeimfive | {
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"text": [
"Do you mean the old oscilloscope-style vector graphics or the modern of vector graphics?"
],
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djdr31 | How were TV broadcasts able to be hijacked and why don’t/can’t they happen anymore? Instances such as the infamous ‘Vrillon’, ‘Max Headroom’ and ‘Captain Midnight’ incidents. | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"When TV was analog radio waves, an analog transmitter of sufficient power could send a signal to nearby receivers. This was called \"pirate TV\". Today, TV is digital, and for the most part constrained to cable TV company fibers. You could transmit, and may be picked up by that one person with an antenna, but all those Comcast people can't get your signal without tricking someone at Comcast to add your signal to the lineup.",
"In the case of Max Headroom, someone with inside knowledge was able to hijack the STL (studio to transmitter link) signal, which is how stations get their programming from the studio to the transmitter. By knowing the frequency and direction, and by having an STL transmitter, they were able to put their own programming on the air. I’m that case, whoever did it must have had at least a camera, an STL transmitter, and a big-ass antenna pointed towards the Sears Tower in Chicago."
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djerwt | How do touchscreens "know" when skin is touching them, and/or how do they know it's just a conductive glove? | Technology | explainlikeimfive | {
"a_id": [
"f44ngkz"
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"text": [
"Touch screens typically detect capacitance. A metal glove will have way more capacitance than your finger, and so the screen knows that something is not right. Capacitance is basically an object's ability to hold electric charge. Large, conductive things have the best capacitance. If you picture the big dome on top of a van de graaf generator, that's meant to have a lot of capacitance. Our bodies have a sort of mid-tier capacitance."
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djjk6n | How do rocket scientists know for sure that the payload is not going to crash into a space junk while being deployed to space ? | Technology | explainlikeimfive | {
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"text": [
"They track every piece of junk they know of. But once you are out of orbit, space is beyond huge. Here's a example. When putting a probe out into space, and it has to pass through the asteroid field, they don't even have to check they just launch it through. Because even in the belt, there is so much 'space' you'd probably only hit one if you deliberately tried.",
"US Strategic Command is mandated to keep track of every object orbiting earth larger than some size (a few centimeters). Once you know the orbit of an object (with various telescopes radars, and space based telescope) you can predict the path of the object. They can then plan the path of the spacecraft to avoid these as much as possible. While in orbit, If any detectable object is within a a certain radius of the path (maybe a kilometer or so?, distance would be based on what the precision of the measurements and given a safety factor) they can perform a small maneuver to adjust the orbit slightly. Edit: oh and rocket scientists can also generally guess where the smaller undetectable (but still sometimes* hazardous) debris might be (or guess where all types of debris might go in a hypothetical collision) based on qualities of the orbit that the source of debris was in, and where within the orbit the debris inducing incident occurred See “Gabbard Diagram”"
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djkonh | how does google earth have such sharp images and 3d buildings correct to the number of windows if satellites are so high up? | Technology | explainlikeimfive | {
"a_id": [
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"text": [
"When you use Google Earth satellite view and zoom in, what you're actually seeing is images from various different altitudes. Once you're close enough to see building details, this is likely an image taken by airplane or helicopter.",
"Satellite view is a wrong name for it, it's aerial view: The photos are made from a plane flying relative low.",
"The highest zoom picture on google maps are taken by aircraft not satellites. Many detailed 3D Models of buildings on google maps were actually user submitted and created from photos taken from various perspectives and assembled by hand, but google retired submissions for buildings for google maps a few years ago. Now it is just done with algorithms. they take a whole lot of pictures and infer a topographical map from that and than apply the images they took and paste them over the map. This is why on google Earth some buildings have weird stuff with perspective going on. Google has a video about the process up here: URL_0",
"Google and other map providers use a variety of sources to create their maps. They'll use satellite imagery, aerial imagery and terrestrial imagery to create the different levels of resolution. Having worked in aerial surveying previously, I suspect that the limiting factor for resolution on Google maps is bandwidth and storage, not the image acquisition side of things. Creating 3D buildings is trivial with enough images and something to scale off of. Since the buildings are created using photos of the buildings themselves, having the incorrect number of windows would be strange, though not impossible."
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djkx7k | Why is a .zip file smaller than the file that gets extracted from it. | Technology | explainlikeimfive | {
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"Because redundant data is compressed. The algorithm recognizes patterns and describes the patterns instead of spelling them out. An easy example: Imagine there is a file with this content: `10101010101010101010101010101010101010101010` You can replace this file with something like `\"10\"*20` (or whatever the number is, I didn't count it). The result is much smaller. The algorithm is capable of recognizing much more complicated patterns and the zip file simply contains descriptions of those patterns. If you have a file with no patterns or no patterns that the algorithm can recognize (like an encrypted file or an already compressed file), the zip file might even be larger than the file it contains.",
"A lot of these replies dont adress your actual question. Picture each letter in this sentence as 1 kb of data. “I went to the store and ate lettuce”. Thats a lot of letters. One way to think of Compression is to imagine translating each known word into a single character (simplified). So instead of that long sentence it would be somethjng like 1 7 3 6 9 7” significantly reducing the number of letters. It gets more complicated when instead of words it even translates combinations of letter. So the letter sequence of “T” followed by a “O” like in to, and store, are now represented by a single character. So you can use the code for more than one word. You do this enough and you represent the same information with much fewer characters. Edit: the reason why you have to eventually unzip the file to use it is because the program does not know the code used by the compression software. Unzipping is translating code back into its original data."
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djmg4d | I've been told that satellite radio, some TV broadcasting, GPS, etc. all "bounce their signals off a satellite". But if satellites are in Earth's orbit, how does the signal bounce off then if they are on the other side of the earth or out of a clear path? | Technology | explainlikeimfive | {
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"Simplest answer first - There's more than one There's not just one (for example) DishTV satellite. They have enough satellites to ensure coverage for the areas where they offer services. Secondly, for the services that offer coverage in specific area, their satellites are in what is call \"geosynchronous orbit\". Meaning, they are moving at the same speed that the Earth is turning, so that they stay in the same relative place"
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djnb0b | How were VHS tapes mass produced? | Technology | explainlikeimfive | {
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"Pretty much the same way that you would duplicate a tape at home: Read the video from one tape, and write it onto an empty casette. However, they were using automated machinery for this process. Since reading and writing tape also degrades the quality, they were using a very high quality video tape as a master to read from, instead of another video casette.",
"They used high speed dubbing machines. Here's a video of [it in action]( URL_0 ). They work basically the same way as a home VCR, it just works a lot faster. A high quality master copy is read at a very high speed, then a bunch of rotating magnets transfer the signal continuously onto huge reels of blank tape that's running at the same high speed. That tape is then trimmed and spooled onto the reels inside the cassettes. It's a deceptively complex process. Tapes are a lot more expensive to manufacture compared to optical discs. Hence why they quickly disappeared after DVD players became affordable.",
"If you mean how was the recording transferred onto the tape, I believe they used a process where a master tape was pressed against the blank tape, and locally heated to transfer the recording. This can be done at higher speed than just playing the master and recording it onto the blank! I think the master had to be \"negative\", eg recorded with a reversed magnetic field."
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djntjq | How does the flash bang work and what's the feeling being flash banged? Does it really work like in FPS games? | Technology | explainlikeimfive | {
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"> Does it really work like in FPS games? During army basic training I was, accidentally, flash-banged. The platoon had set up a bivouac for the night and we expected to be 'attacked'. I got to sleep for the first watch so naturally I was awoken by said attack. Some shots and then a flash bang landed about 3-4m from my head. When it went off I was completely incapacitated. I wasn't blinded because I had turned away but I was stunned. Someone I vaguely remember is standing a foot in front of me and appears to be yelling but I can't hear him. He goes away and I look around. Apparently I'm in a wood and I'm cold. There are people running around. I recall something about a gun, oh there it is, I get the feeling I should pick it up. The other guy comes back, still yelling. Now I recognize him, he's the platoon sergeant. I try to say that I can't hear, but I have no idea whether any words came out so I point to my ears and shake my head. I remember the flash-bang so I point to where it was and he sees the debris and realizes what happened. It was a good 10 minutes before I could hear again even partially. I still had to stand my turn at watch.",
"It creates a bright flash of 7 million candlepower that temporarily blinds you for a few seconds, and causes you to see after-images for several seconds after sight returns. It makes a loud bang over 170db that disorients and disturbs the fluid in your ears which causes loss of balance. I’ve never been flashbanged so I can’t say how accurate or inaccurate it’s depiction in FPS is, but in the sense that in games it makes it hard to see, aim, and move for several seconds is accurate.",
"For whatever reason the ones in video games are single bangs. All the ones I've seen in service are 9 bangs. Ive done plenty of 9 bang inoculations in a dark room and I'd say that video games really over egg the effects.",
"A flashbang grenade is basically just a tube filled with pyrotechnic powder (usually powdered aluminum/magnesium) attached to a fuse and a bursting charge. When the fuse ignites the charge it explodes and propels the powder out of the tube and into the air. A split second later the powder ignites and creates an incredibly bright flash and a strong pressure wave. Being anywhere near one when it goes off is extremely unpleasant. Being within the effective range, especially in an enclosed space, results in temporary deafness, permanent hearing damage, temporary blindness and blurry vision, and loss of equilibrium. Basically it makes it damn hard to hear, see, or move around for a few seconds. As pyrotechnic devices flashbangs can be very dangerous. They have the potential to start fires, throw debris at high velocity, and cause serious burns."
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djo3iw | Why media system in cars is like 10 years behind the rest of software world, even in a completely new cars with new media systems. | Technology | explainlikeimfive | {
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"Well, for one, your vectors for software update are limited. Not a lot of head units allow software updates and those that do usually you can't just slap a USB stick in.... wait, theres no USB slot.... and press a button to update. Usually its restricted to update by dealers and so on. So, like games for older console units, waaay more testing before release because you can't push out an update later to fix bugs like you can with connected devices. Further, to reduce the scope of testing you want to strip out or eliminate as much extraneous functionality, chrome and bells and whistles as you can. Secondly there are tons of UX rules for how small text can be. If Im not mistaken there are federal automotive guidelines on how bright the text has to be, how readable, font sizes etc. etc. So you can just slap windows on a Surface tablet and be done with it. And as above, since you are now governed by federal automative laws (and there are more than you'd think), you have to get certification etc. and that means testing. I worked at a Bluetooth device manufacturer and we had to test interoperability with some car head unit software makers. While Bluetooth standards are... well... standards, it doesn't mean there aren't tons of areas where bugs and quirks shake out. I remember we found a bug with one of our devices that ONLY appeared on particular versions of the head unit OS ONLY on certain vehicle models (aka the head unit model)... and only if the car had a certain luxury feature. Think like your Bluetooth call dropped if the sat nav kicked in AND you had cruise control on. I know, weird shit. So testing, testing, testing. Plus, the whole head unit OS has to be realtime. Yes, under normal circumstances your phone or tablet is real-time-ISH, but its not. If some bad application takes 100% of your CPU it can brick your device until you reboot. Can't have that happen on your car. So testing testing testing. Lastly, once you have a platform that is tried and true, you don't want to mess with it save for required OEM customizations. Thats why there's relatively few players in the head unit OS market. QNX (now part of Blackberry) for one and Microsoft... and Microsoft (imho) sucks. Adding new features to a tried and true foundation that is used across a lot of brands is a rather serious endeavour. Same kind of reason why you don't have a lot of variance on avionics packages; if it works, don't dick with it. Especially when its mission critical and you can't update it easily.",
"You gotta remember that the car is mostly about the driver and not the passengers. There are a lot of safety and laws around distracted driving. Car manufacturers are slow to make a change that will make then look careless and create an unsafe vehicle."
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djomt3 | Why do traditional alarm clocks snooze for 9 minutes each time, why not 10? | Technology | explainlikeimfive | {
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"URL_0 Because some people a long time ago decided ten minutes was too long, so they geared the snooze to 9 minutes"
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djukpo | Why some portions of software installs take longer than others? | ELI5 Why some portions of software installs take longer than others? Today I was doing a software update for my phone. The first 32% installed really fast (matter of seconds) but then the rest seemed to crawl and move really slow. Whole install probably took 10 minutes. But based on the first 32% I was expecting it to take 3 minutes max. In my mind the percentage on the status bar would be based on the total size that needs to be installed. So if 100MBs needs installed each percent is 1MB and it should all move the same speed. Why is this not the case? | Technology | explainlikeimfive | {
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"That's because not every install is as simple as just copying data from a compressed file from one location to another. Sometimes it needs to schedule updates of files that are open, sometimes it needs to decompress large files that are far larger than their compressed size, sometimes other things are going on in the background. The issue with giving definitive answers here is that the reason why installations might slow down for different softwares will change for each software, there isn't one overarching cause."
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dk06c3 | For what reason do banks not employ two-factor authentication to ensure the authenticity of transactions? | Technology | explainlikeimfive | {
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"Some banks do offer 2FA tokens. My mother is an administrator for a small business and has one on her keyring for all work transactions. The administrator for a small business that I work for has one on her keyring for work transactions also. Both businesses are with different banks. Many banks offer 2FA via SMS or downloadable apps. My bank sends me an SMS code for payments to any payee I'm transferring to for the first time or for payments over a certain amount. I would say your bank is just behind the times or has decided that the cost and risk involved with implementing it is not worth the hassle. It could also be that their primary customer base has not expressed any desire for a 2FA setup."
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dk06k4 | When money is exchanged and stored electronically, what stops one from hacking this system to create virtual money? | Technology | explainlikeimfive | {
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"The Fed has a register of how much money every bank has as well as how much money changed hands between banks every day. Every bank has a register of how much money it has, as well as every transaction it had with another bank. At the end of every day the Fed checks with banks to make sure that their register and the bank's registers look the same. If they don't, then go through their transactions to see where the error is. Because money is a zero sum system, an error in one registry means that registry doesn't match any of the other registries. This means its easy to figure out where the error is by just looking at whose registry is out of sync. To \"hack\" the most basic implementation of this system you need to simultaneously hack 51% of the registries without anyone knowing that you've done so. Then you have to consider that banks don't just have one registry that they're constantly changing. Every day they're backing up that registry into a separate storage. This means that simultaneously changing 51% of the registries *without being caught* isn't good enough because the fact that 49% of the registries don't match will cause people to go look through the backups. To successfully hack the system under real world conditions you need to hack every single registry on the planet, as well as the backups, simultaneously. That's not really possible to do. That being said the system has been hacked before, but those hacks work by hijacking the payment processing system to pull money out as cash before anyone notices. Once someone notices they can just fix the registry, but if you've already withdrawn the money as cash then its gone. In a purely electronic system that can't happen, but we aren't there yet. [See, for example, the SWIFT thefts that are believed to have been carried out by North Korea a few years ago.]( URL_0 )"
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dk2l23 | How does a computer restart on its own? | Technology | explainlikeimfive | {
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"Your motherboard contains a crude operating system referred to as the BIOS or Basic Input/Output System. You often see the actions of this when your computer first starts as it sometimes displays information about your computer hardware, or manufacturer logos. The responsibility of the BIOS is to initialize the various hardware components necessary to start the computer. Once this has been achieved, it will attempt to initialize any operating system it can find on your mass storage device (SSD/HD). It locates this operating system by looking for something called the Master Boot Record which by standard can be specifically located. Your operating system communicates with the hardware, at some level, via the BIOS. This is a simplification, but this allows the operating system to be restarted. In essence, the last thing your OS does before shutting down is to tell the BIOS to reset, as opposed to issue the command to cut power. The bios, upon receiving this message will restart the initialization process. TLDR: Windows/Linux/MacOS, etc. sends a command to the BIOS which takes over the final reset, resulting in rebooting the whole computer."
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dk5eym | How does a pulse oximeter measure the blood oxygen levels without actually taking blood? | Technology | explainlikeimfive | {
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"One side of the clip has a light and the other has a sensor. When you clip it on your finger, it shines both red visible light and infrared light through you finger and it hits the detector on the other side, after passing through your finger. Hemoglobin is the protein in red blood cells that carries oxygen. Saturated hemoglobin (full of oxygen) and unsaturated hemoglobin (not full of oxygen) absorb different amounts of infrared and visible light, so by comparing the ratio that the sensor detects to the ratio that was emitted, it can tell how much of the hemoglobin in your blood is saturated and how much isn't. Edit: As others have pointed out, it can only tell whether hemoglobin is saturated or not. Someone with carbon monoxide poisoning will still show normal saturation because the hemoglobin is saturated with carbon monoxide. (Edit to this edit: apparently newer pulse oximters can measure carbon monoxide as well). Edit 2: A lot of people are asking about the kinds on watches or other fitness devices. My description above is for the [finger clip pulse oximeter]( URL_0 ). The ones ones on watches and whatnot work the same way, except the light is reflected back instead of passing through the finger.",
"It's a colorimeter! ELI5: it looks at the color of the blood in your finger and can see how much of it has oxygen based on what color it is.",
"I'm a nurse. I'm not necessarily an expert on exactly how it works but I have a basic understanding. Basically the little red light that the finger clip lets off goes through your finger and hits the sensor on the other side. Using the power of science the sensor can tell how much of the light was absorbed by the blood going through the finger, and it uses this to math out what percent of the hemoglobin has something bound with it. Hemoglobin (the part of the blood that carries oxygen) absorbs different amounts of light depending on if it has something on it or not and the computer can use that to figure out what percentage of the hemoglobin is bound with other compounds. It's a handy tool for a quick reading but it isn't perfect and has its drawbacks. If someone has fingernail polish on the light won't go through the finger properly and you won't get a good reading. Similarly, if you're really cold or have poor finger circulation for some other reason there won't be enough blood going through to get a reading. In that case, you need a special probe that can be stuck to the forehead or somewhere else to get a reading. Another problem is that it can only tell you how much oxygen is bound to your hemoglobin as a percent of total hemoglobin. So if you're bleeding out or your hemoglobins low from something like anemia, the sensor will read as though you are properly oxygenated even if your cells aren't getting enough oxygen. For example, say your hemoglobin is crazy low, like... 2 (normal is roughly 12-16 for females and 14-18 for males). If you're still breathing ok the sensor will read 100%. But that doesn't matter because 2 hemoglobin isn't enough to give your body the oxygenation it needs even if every bit of it is bound with oxygen. One other issue with it is it only reads what % of your hemoglobin has *something* bound to it. Not just oxygen. Hemoglobin binds to other things besides oxygen. A common example is carbon monoxide. The reason for this is that if you breathe in both oxygen and carbon monoxide, Hemoglobin will bind to the carbon monoxide *before* it binds with the oxygen. This has to do with chemistry and whatnot but basically the hemoglobin has a greater affinity for the carbon monoxide than it does with the oxygen. So if you end up in an ambulance with carbon monoxide poisoning and they put a pulse ox on you, it will probably read as normal. This is because the machine just reads that the hemoglobin has something bound to it, it doesn't realize it's something that you can't breathe. Pulse ox's are a good tool but their just machines that can be fooled and have problems. True low readings are bad and should be treated, but high readings don't necessarily mean the patient is ok. That's why there's a common saying in healthcare to always treat the patient and not the machine. People get super caught up in treating numbers like O2%, blood pressure, etc. without looking to see if those numbers match what the person is experiencing. If your heart monitor says the person's heart isn't beating but they're sitting on the edge of the bed talking to you, it's usually wise to troubleshoot the equipment before trying to do CPR.",
"It shines a light through your finger, on the other side of an eye that's really sensitive to color. The color of blood is different when there's oxygen in then when it's not in there. So the eye can see the color and determine how much oxygen is on the blood.",
"Oxygenated homoglobin really likes to aborb infrared light(specifically wavelenght = 940nm), but allows red light(660nm) to pass through. While, deoxygenated homoglobin allows more infrared light to be passed through, but aborbs red light. There are specific sets of lights and sensors that only work on those wavelenghts, and ignore the other. We fire off light and measure how much light gets on the sensor. We can now divide those amounts and get the ratio of saturated blood cells in our bloodstream.",
"Came back to all these fantastic explanations! Thanks, y'all!",
"The clippy thing shines a finger, or earlobe, with two lights (Infared and Red light) like a flashlight followed by a detector that absorbs light from your blood."
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dk71lr | Why are phone screens so hard to see when you film them? | We can see them very well, but cameras seem to have a hard time capturing them. Why? | Technology | explainlikeimfive | {
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"The screens have a refresh rate, where the entire screen is converted from one image to another like a flip book. The faster the pages flip, the better it looks to us. Cameras record in a similar way, taking pictures at a quick pace. Which when shown rapidly makes a movie, like pre-digital theater projectors. These picture flips/frame rates are usually different or started at different times so that the camera takes it's snapshots between screen refreshes causing a flickering. I believe there is more to this if someone else wants to add on or correct me."
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dk94po | How does Spotify's "Discover Weekly" work? | The title. Basically is it custom tailored on what I listen to? Is there a lag time from when I listen to music to when it will affect the playlist? What all factors into the playlist? I assume its made via an algorithm but I wonder what all goes into it and how it works, simply speaking. I have some background in coding but not much and not related to this sort of work, so an explanation somewhat beyond the most simple explanation would be awesome! | Technology | explainlikeimfive | {
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"So I’ve heard a few things about it, but this is still just my best guess. Spotify tries to recommend you music you’d like based on what other people are listening to. Through their playlists functions and general listening stats, they can assign value to songs with respect to your preferences . For example, let’s say song A appears in one of your playlists and a playlist of someone else. Spotify can find songs related to song A in their playlists , increasing a suggested song’s recommendation value. My guess is this value is only increased if a recommended song appears multiple times along song A in multiple playlists. Every quality of a song you could think of is probably used in some regard to recommend music."
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dk9vo4 | Why do gaming apps like Steam and Origin update so often? | Often times, there's no visible change to the app. I realize content needs to change, new games are added, etc... but I feel this can be done via a simple config file or database. If it's for bug fixes, why can't they bundle them together and release them once every few months? | Technology | explainlikeimfive | {
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"because software is complicated. and it runs on a wide variety of environments. some customers run in environments where they encounter bugs. other customers don't run in those environments. a release is made to fix the program so it runs bugfree in all environments. they release it fast because it solves those customer's problems immediate. how would you like it if your Steam crashes every day and they waited for that fix to be bundled in the next release 6 months from now?",
"You can just read what the updates are here [ URL_0 ]( URL_1 ) As you can see, various security vulnerabilities, UI bug fixes, improvements that would be unnoticeable to you unless it was pointed out, features you may not care or know existed, etc. Bundling all those updates together every few months is a great way to create more bugs that take more time to untangle as is harder to figure out which update unintentionally broke something else.",
"The more changes you include in a release, the higher the chance that one of them will go wrong. It's far easier to figure out what went wrong in a week's worth of changes than in two months' worth. It can also help the users be happier: you get less backlash if you break one thing than if you break 4 in one big release. It's also a good thing to be able to \"fail early\". You want to know your new direction isn't the right one as soon as possible, and not after months of work have been done in the wrong direction. Really whether to make frequent releases or not is a matter of personal preference. Steam has an easy time making frequent updates as it's all online by nature anyway, so why not? Other programs get a lot of offline use and there frequent updates might not work so well."
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dkjbfn | How does 4k video transfer work | This kept me awake all morning. If 4k video is approximately 8 million pixels and each pixel is approx 3 bytes of data, them that is about 24MB of data. If most movies are 30fps, them that is about 720MB per second bandwidth needed to transfer just the video. But somehow a 4k movie is transferred over Netflix at less than 25 MBPS? Am I not getting full 4k? | Technology | explainlikeimfive | {
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"If you were transferring 30 unrelated images per second, that would be the case. But videos are not a bunch of unrelated pictures. Videos are s sequence of lightly changed pictures. So, what we do is compare the first picture to the next one, and get the difference between them. That's what we send. Look up compression algorithms for video",
"There is this mathemthical technique used on the video to compress it. if for example you have 1 second of exactly the same black picture you could just as easily say \"do this black picture 30 times\" which would cost way less bandwidth than in detail describing the same black picture over and over and over again 30 times. this is basically how they do it, you can do an lot more advanced stuff such as if an black square was moving over an white background you could mathematically describe \"move black frame 2 pixels to the left every frame\" instead of having to detail every pixel individually again. All the above would be considered \"lossless\" compression, because you can recreate the exact origin from the compressed data. but an near perfect picture is good enough for almost everyone, so with a lot more of clever mathmathics we can make files even smaller at the loss of details. some mathmethical algorithms for example focus on detail in faces and hair because people watch that the most, while the background is a lot more blurry because its just not as important to the scene. this is also why bluray is visually superior to any streaming, it almost always has much more MB per second to work with and can thus use an compression that loses less of the original image.",
"I'm no expert, but a lot has to do with compression. For one, a 24/30/60 fps video isn't sending a full image for every frame, more like a full image every few frames (an i frame) and several 'move these pixels around a bit and leave the rest alone' frames (p frames - note that I may have gotten those backward). That, and there's data compression to shrink the images from a straight up 8 million pixels with individual info down to a much more manageable file with less accurate data. Difference between a .RAW file and a .PNG. That's why blacks and dark grays look like shit on streaming shows and movies: Most compression handles those shades very, very poorly.",
"Imagine you made a picture out of pieces of colored paper, every time something changes you only move the pieces of paper you have to, this means that most of the pieces of paper don't have to be downloaded 30 times a second. This is sorta how video compression works, another thing is where there isn't detail the pieces of paper can be bigger, because it's all the same color, so instead of cutting out 10 pieces of blue it sends \"blue x10\" instead of blue blue blue blue blue blue blue blue blue blue. This is similar to how image compression works. Hope this helps."
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dkl0ks | If all we had to do to get better TVs is fit more pixels into one screen, why did it take up so long to get up to 4K? Couldn’t we have started squeezing in those extra pixels way sooner? | Technology | explainlikeimfive | {
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"Absolute maximum resolution isn't a useful metric for televisions Affordable resolution and screen size is a far more useful metric. You can buy an 8k TV today but the cheapest one is only 65\" and will cost you $3k. We could make a 16k TV but if it costs $100M to design then even selling it for $100k would still require 100 people to buy it just to break even, and there just isn't enough demand for a TV the price of a high end luxury car. It took a while to get the price of large screens where 4k will make a difference(55\" and up) to get down to a price where most people were getting them, and then it took time to get the 4k adder to come down to a mainstream price point. It'll take a few more years before 8k comes down and there still won't be a use for it when it does. TV are sent the data they need to display, this is different from computer games that render it on the fly at whatever the requested resolution is. The result is that getting a 16k TV and showing 4k content on it will only be marginally better than just having a 4k TV. As there is basically no content available above 4k right now then there's no reason for someone to buy an 8k or 16k TV. Normal people look at technology and wonder if we *could*(the answer is usually yes) but engineers designing that technology are forced to ask if they *should*. If its not going to turn a profit then you're not going to make more than 1 as a sweet demonstration unit for marketing.",
"To make a better TV (where better=higher resolution) you need two things: more pixels and content with more data. Play a VHS tape on your 4K display, and you'll see sad, blurry images. Play a DVD and you'll see better, blurry images. Without good content to play, 4K TVs are worthless. Image sources with higher resolution were demonstrated back when they weren't affordable. This applies some pressure on content producers to make higher resolution content, so they start planning. A DVD won't store enough data, so they develop bluray discs to store more bytes. Sometimes the idea dies out (talking about you 12\" laserdisc) and sometimes there is a market. Only when there is affordable content **AND** affordable displays do you have a market where folks can make money. Even today it's far from clear that 4K is enough better than 1080P that \"everything is going to be 4K\" in the near future."
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dkphy7 | Why can't 32-bit programs be run on a purely 64-bit machine i.e. macOS Catalina? | If 32-bit programs are run on less data, why does that prevent it from running on a machine with higher capabilities? | Technology | explainlikeimfive | {
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"Since I never had trouble running a 32-bit program on 64-bit Windows or Linux I assume that would be just MacOS then",
"64-bit operating systems need a compatibility layer to run 32-bit software. On Windows this is called [WoW64]( URL_0 ). This compatibility layer needs to include 32-bit implementations or wrappers for all the host operating system's APIs the app expect to be able to talk to. A 32-bit app doesn't know how to talk to a 64-bit networking library when it wants to look up URL_1 , so this compatibility layer provides that 32-bit interface, either as a completely separate 32-bit version of the networking library, or as a custom made wrapper on top of the native 64-bit version. None of this is particularly trivial to build or maintain. Because Mac users are less reliant on legacy software than Windows users, Apple decided it was no longer worth maintaining the macOS 32-bit compatibility layer (I'm not sure what it's called). I know relatively little about the macOS ecosystem, since I primarily develop in Windows, but I think it's a bit naïve to assume Apple had no reason to deprecate this functionality other than as a callous \"fuck you\" to users. Apple transitioned all their users to a 64-bit OS a decade ago, so the amount of useful software built only for 32-bit versions of macOS is already negligible. Conversely, Microsoft still offers 32-bit versions of Windows, so lots of Windows software still only targets the lesser variant.",
"32 bit programs can't really interact with 64 bit code. 64 bit is a newer standard, so 32 bit programs aren't aware it even exists. This means that 32 bit programs need 32 bit support libraries to work. If those are removed from the OS, 32 bit programs fail to run. So for instance if a program needs a library to decode MP3 files, it needs a 32 bit version of it. In OS X a lot of such things are included with the OS. If the OS stops doing that, the apps can't work anymore.",
"While I can't comment on macOS specifically, there are a number of reasons to remove 32 bit support. * The OS needs to understand the system calls of 32 bit applications which is a lot of compatibility code in the fundamental operating system components. * Apps still have dependencies, like in windows there are DLLs provided by the system itself, that applications require to run. Both 32 and 64 bit versions would have to be provided. Omitting the 32 bit versions reduces the size of the install and how much work is done in testing updates. * 64 bit systems have existed long enough now that there shouldn't be many applications left that don't support 64 bit mode and hence are 32 bit only. Overall, it means less disk usage (and hence less downloading) and less development work for the software maker to do. 64 bit programs can still do anything a 32 bit program can do. In fact it can do it better since there are fundamental hardware updates available such as more CPU registers which should result in faster code."
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dkqpgh | x64 means 64-bit but x86 means 32-bit? | Technology | explainlikeimfive | {
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"Back in the 70s Intel released a CPU called the 8086. They followed that up with the 80186, then the 286, 386 and 486. Each one used an instruction set built on the previous one, which meant for the most part software written for one would work on newer ones. This family of CPUs and the instruction set the used became known as x86. Eventually they made the jump to 64 bit (it was actually AMD which first did this) which became known as x86-64. Then people just shortened that to x64.",
"TL;DR: Neither means either. x86 is an instruction set (\"CPU language\") named after Intel's early processors which tended to have numbers which ended in \"86\" (8086, 8088, 286, 386, 486, Pentium [aka 586]). These processors became very popular and so x86 has been used (incorrectly) to refer to 32-bit processors. AMD then extended the x86 instruction set to include 64-bit features. They called this \"x86-64\" and the industry shortened this to \"x64\". There are 32-bit processors that don't use x86 and there are 64-bit processors that don't use x64. The terms only apply to processors that are compatible with those instruction sets. This is one of the reasons why certain programs don't run on other computers.",
"x86 refers to the x86 instruction set architecture family, which itself draws the name from Intel's 8086 microprocessor. There were x86 chips both made for 16-bit and 32-bit systems. The 64-bit version is named x86-64, which is then shortened for x64.",
"x86 refers to the historical Intel architecture evolved through a line of Intel’s 8086, 80186, 80286, 80386 and 80486 processors. So, “x86” here means “a set of 32-bit processor instructions evolved from Intel processors ending with”86”. “x64” is a short for “x86-64” which means “the 64-bit version of that historical instruction set”."
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dkr118 | How do grocery carts KNOW and lock upon leaving the premise/crossing the "yellow line"? | Technology | explainlikeimfive | {
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"There are lots of different mechanisms. The two common are: 1. for those that use a marker in the road to indicate, there is typically something giving of a signal buried beneath that line that when in proximity of the cart causes the cart to lock. 2. some use an RF signal that causes it lock based on the signal getting weak (distance from transmitter)."
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dku3dc | How do cable companies or satellite services get their program descriptions into their online guide and who writes them? | Technology | explainlikeimfive | {
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"Most use an company like Gracenote (think a commercial version of IMDB without ratings but has future programming) as a base. It has program names with descriptions, when it will show, what channel, and even art. Then for services like DirecTV and Dish they add any special programming they have (like music channels, Pay per View) then encode the guide as part of the signal you receive as while watching TV on every cnannel. Over a few minutes you download 2 weeks of guide content. Source: I work in the industry and have built Set Top Boxes Side Note: most new set top boxes are internet connected so they just download the guide on demand. However if you have one that is not internet connected you can sometimes watch it build the guide. Just unplug the box for 30 seconds, plug it back in and once you see tv open the guide. Most cheeper units will have missing pieces and then over a minute or 2 you will see pieces get filled in.",
"I work for Gracenote. Without divulging any confidential information, large teams spread across the globe are continuously sourcing program information from various broadcast networks (broadcast TV channels only) and writing show descriptions that show up on your cable TV/set top boxes which gets consumed by end-users. PPV TV information also is a part of what we do. The new-age hybrid set top boxes pull this information by means of APIs and the lag you see depends on the speed of your internet connection."
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dkvs7o | How does Noise Canceling work? | Technology | explainlikeimfive | {
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"Sound travels in waves, with a certain amplitude and frequency, which dictates the pitch and volume. Active noise cancelling, like you seem to be describing, has an external microphone that picks up what sounds are approaching the headphones. Then it generates a (usually white noise) sound that is the inverse of the incoming sound in order to 'drown out' the noise. An easy way to visualize it in a text-only format would be using a digital signal. Incoming sounds : 1 0 1 1 0 1 1 0 1 Cancel-out sound: 0 1 0 0 1 0 0 1 0"
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dkwcjv | What is the problem with IPv6? The IT crowd doesn’t seem to like it. | Technology | explainlikeimfive | {
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"That's because the IT Crowd is a TV show and not a networking team. Before everything was standardized on IPv4, the world ran on Thicknet, TokenRing, FDDI, ArcNet, Ethernet and on SNA, IPX/SPX, IPv4, DecNet, OSI (for the short time that it existed). And everybody who was neck deep into it didn't like the others and made jokes about them. < - There is your IT Crowd reason. Currently the world is standardized on IPv4, TCP and Ethernet (Even the fiberlinks get terminated by the providers on Ethernet) and we have the same groups of people who make jokes about new things because they are different to what they know: IPv6 instead of IPv4, QUIC instead of TCP, Jumbo frames instead of the small Ethernet frame size etc. if you want to know why IPv6 rocks: Technical reasons: No more subnetting, auto addressing, local link networking. Management reasons: End-to-end connectivity, global unique addresses by default. (Everybody who has ever done a merger and acquisition knows that they are hassles with IPv4 and as smooth as possible with IPv6: Global unique addresses). Sources: Running IPv6 since 2001 via a tunnel, running native IPv6 since 2009."
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dkyw45 | How do you "dumb down" an IA to play games on easier settings ? | Hi there ! Say you are playing or Age of Empires, against the computer. What mechanisms are used to ensure that the computer doesn't win everytime ? It knows where every unit is, can give WAY more commands per second than you, calculate the outcome of moves faster, and unlike SOME human player won't fumble around trying to get the walls to look really fancy or align soldiers perfectly because it has OCD. So how do you get from "teaching the computer to play" to "teaching the computer to not play too hard" ? Does it "have" to wait for you or make mistakes ? Is it limited to a few patterns, like sending X units every X minutes ? It seems a little too rigid for me, especially for newer games... Thank you ! | Technology | explainlikeimfive | {
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"You can limit the number of actions it can execute in a time frame. I.e. \"hard = it can send 1 action per second, Easy = it can send 1 action per 2 seconds\". You can limit the resources it gets. I.e. \"Hard = every worker brings back 15 gold, Easy = every worker brings back 7 gold\". You can limit the knowledge it has. I.e. \"Hard = it can see entire map, including into fog of war, Easy = it can only see in fog of war\". Etc etc. Essentially you are not tuning the \"difficulty\" or AI, rather you're tuning the handicap that you're giving either yourself or the AI, to better match your skill. Some AI are smarter than others - for example, look for articles that talk about AI in F.E.A.R., or for the Starcraft AI championships (as well as DOTA2/SC2 Deepmind AI)."
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dl0nvu | How exactly do “Binaural Beats” or “brain music” work? Is there real science behind this? | Technology | explainlikeimfive | {
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"They don't. And there isn't. It's all placebo, basically. URL_0 \"So, in summary, binaural beats certainly do not work the way the sellers claim, but there's no reason to think they're any less effective than any other music track you might listen to that effects you in a way you like.\"",
"No. Also, changing the tuning of middle A doesn't make the music \"resonate with the natural frequency of your body.\"",
"They're relaxing and good for mediation. Everything beyond that is the actual science of meditation. That's it.",
"Theres nothing too crazy about binaural beats. The name gives off the vibe that it messes with your mind in some way. Its a sonic occurrence when you have to two low-frequency sine waves that are slightly out of tune from each other. For example, if you have one sine wave at C1(~32Hz) and a second playing at B0(~30Hz), you hear a combination tone the same that you would hear any two notes being played at the same time. The difference is that because lower notes and therefore lower frequencies have longer wavelengths, you’re able to distinguish the peaks and valleys that are being created through the sound going in and pit of phase much easier than you would be at a higher frequency range. Brain music on the other hand is a much more broad term that could mean anything from lower case music (drones/ambience/binaural beats/etc...) to meditation style musics. The difference is that binaural/isochronic/brain music is mostly placebo while traditional meditation music (singing bowls, easy listening, yoga music) is good for relaxing. My personal thoughts to why binaural beats are consistently thought of to have certain ‘powers’ in the mind is that it IS a strange sound for people who don’t hear it often. And typically when you have a sound system that can faithfully produce low frequencies, you get a more powerful sound being produced. (Feeling your headphones, or seeing your speaker cone vibrate) But just the same as standard music, you shouldn’t be listening to it at an unreasonable volume because you CAN damage your hearing.",
"while \"brain stimulating\" music might not work the way companies advertise it to, habits can be formed very nicely around various triggers such as sound, smell,... So if you listen to a specific type of music, while doing a specific action or activity, you can create a link between those two things. So when you hear/do one of the two, it can trigger a reaction. So you could create a link between \"piano music\" and \"reading\", and feel like you want to read when you hear \"piano music\". too lazy to look for sources though, so do your own research on this",
"The CIA actually declassified a report called project Stargate which dealt with quickly inducing people into a trance like state. Primarily they wanted to do this for experimentation into metaphysical means of warfare (training psychic soldiers). Sounds batshit, but if you look into it they were able to achieve some interesting results. Anyway most binural beats are garbage, but project Stargate made an interesting discovery about listening to an approx 7hz frequency (6-8hz). The beat over the course of a couple minutes made your heart synch up with it which produced a vibration in your brain that would fuck up electrical signals on the outer parts of your brain. This would create a way to rapidly induce a trance like state where your extremities would go numb. The goal being able to perform astral projection with quicker results for noobs. I tried listening to a 7hz frequency and I swear to God it blocks your thoughts. You have to actually put your will into thinking, it's weird. It's like white noise and drowns everything else out, and yeah your limbs go numb faster when you feel your heartbeat relax. Spooky shit.",
"Binaural beats are an auditory illusion created by playing two sine waves at different frequencies on either side. It creates the illusion of a subharmonic frequency equal to the difference between the two frequencies. There are no further special properties, it's just a sorta cool auditory illusion.",
"Down to science, our brains respond to music. Fast music makes us want to move faster, slow music makes us want to chill. Binaural beats though, their aim is to play beats that match certain tone frequencies our brain does stuff at, how accurate they are can be questionable. This makes them incredibly subjective. I know people who swear by them, I personally can't stand them. They're good for tasks that require focusing on one distinct thing like meditation. They're simple and consistent so you can stick with the patterns. For most people, the actual beats per minute will make the biggest impact and the tone will be just another subjective side of it.",
"Binaural beats are a real, physical phenomenon, not just some sort of illusion. [Here]( URL_1 ) is the soundwave formed when you combine 440 Hz and 441 Hz. It looks like a normal wave, because at first the crests and troughs of the two waves are in sync and build on each other. But if we [zoom]( URL_0 ) out, we see the wave start to fall out of sync, until eventually, one wave is high while the other is low and they cancel each other out. After, the waves come into sync and build on one another, back and forth, creating the binaural beat. And even though 440 Hz is too fast for us to individual changes in wave amplitude, the sync-desync process takes a full second, which is easily audible. The closer the frequencies, the longer the binaural beat.",
"When folks say binaural beat they are talking about projecting an isolated sound frequency. An isolated frequency will effect the frequencies of a persons electromagnetic field through sympathetic resonance. Very basic concept of how it works but works it does. See below. Work cited. A vibration is a periodic “wiggle” in time. A wave is a periodic “wiggle” in both space and time. The source of all waves is something that is vibrating. Light and sound are both vibrations that propagate through space as a wave, but are two very different types of waves[2] Sound is a mechanical wave that propagates through space as the vibrations of a material medium - solid, liquid or gas. Sound can’t travel though a vacuum - a medium must be present for the vibrations to exist. Light (electromagnetic radiation) is the vibrations of electric and magnetic fields. It is self-propagating and no medium is required, hence, it can travel through a vacuum[2] Wave–particle duality is the concept in quantum mechanics that every particle or quantum entity may be described as either a particle or a wave. It expresses the inability of the classical concepts \"particle\" or \"wave\" to fully describe the behaviour of quantum-scale objects.[3] Albert Einstein on particle waves,”It seems as though we must use sometimes the one theory and sometimes the other, while at times we may use either. We are faced with a new kind of difficulty. We have two contradictory pictures of reality; separately neither of them fully explains the phenomena of light, but together they do”.[1] To better understand think of reality as a liquid, a sea of particles. As the particles vibrate waves are formed. The variance in oscillation of the waves is what our eyes/ears perceive and this perception is how our minds create reality. So now that everything is vibrating how does one vibration effect another? Sympathetic Resonance: Consider some physical body that can be set into motion by an impulse, and continue to vibrate for a period of time after the impulse before coming to rest. Examples of such bodies would be a tuning fork or a violin string. If these bodies have a preferred frequency of vibration, then a series of very weak impulses – that is, impulses that are too weak to initiate vibration on their own – will cause the body to vibrate provided that these impulses are delivered at the preferred frequency (Helmholtz & Ellis, 1954). Furthermore, the vibrations of one body can serve as the set of weak impulses that can set another nearby body into vibration. For example, if one strikes a tuning fork, its vibrations will cause vibrations in a nearby, similarly-tuned tuning fork. This latter phenomenon – in which the vibrations in one object produce vibrations in another – is called sympathetic resonance. [4] In Itzhak Bentov’s book “Chasing the Wild Pendulum” he references an experiment where there are multiple grandfather clocks with pendulums starting at different angles. After two days the energy transmitted by one clock had all pendulums swinging in phase or together. Pg 25 The Hindus Buddhists and Jainists all believe that the cosmos is vibrating at a certain frequency 🕉 OM. OM is the creation. You can study the science behind OM here: URL_3 Listen to the OM, bring yourself to balance, existence begins to flow If parts of your mind or body have fallen out of phase listen to the healthy frequency and through sympathetic resonance it will restore your EMF to its optimal frequency or the frequency most in tune with the cosmos. And everybody should read Bentov’s books Chasing the Wild Pendulum and A Brief Tour of Higher Consciousness. mind=blown [1] Albert Einstein, Leopold Infeld (1938). The Evolution of Physics: The Growth of Ideas from Early Concepts to Relativity and Quanta. Cambridge University Press.CS1 maint: uses authors parameter (link) Quoted in Harrison, David (2002). \"Complementarity and the Copenhagen Interpretation of Quantum Mechanics\". UPSCALE. Dept. of Physics, U. of Toronto. Retrieved 2008-06-21. [2] URL_0 [3] URL_2 [4] URL_1",
"[Well here is a study which looks at the effects of Binaural Beats of pre-op dental patients anxiety levels]( URL_0 ) My own personal experience is thus. My sister was struggling with insomnia so I did some googling to find things that might help her. Amongst the things I found were Binaural Beats. Not wanting to advise her to try something I hadn't already tried I promptly spent the next three days listening to BB as I lay in bed waiting to sleep. I chose a video on YouTube that had good reviews. The video was ~15 minutes long. Normally I would lay 30-40 minutes in bed before drifting off. I found I wasn't asleep on the first playing of the track but by the end of the second I was. I found that I dreamed vividly. Something that doesn't happen often being a daily user of cannabis. For three days I did this, using the same track. After the third night I figured I should give it a break as I wasn't sure as to whether it was safe for my brains health. What I found in the next few months was that my brain had developed a 'switch' to fall asleep. I didn't need the BB but I could fall asleep much quicker than normal, and it was a conscious decision. It was like I was lower the gear in my brain into sleep mode. Although the vivid dreams didn't persist. Make of that what you will.",
"So these didn't pop up as some sales fad like essential oils or vitamins. They were discovered and verified by EEG monitoring the brain waves of several subjects to see if their brain frequencies changed while listening to them. They did, and in fact, they began to normalize to the frequency of the beat. [Source.]( URL_2 ) Try firing up all the washers in a laundromat for an example of what's happening. They will start out individually, but within a few minutes the washers will sync up and appear to be making a singular noise all together. Also, women living close together often see a synchronization of their menstrual cycles. When you use *actual effective binaural beats properly* what is essentially happening is each ear hears a tone that are slightly offset from each-other. The disharmony is noticed by the part of our brain that puts the sounds together, and the \"beat effect\" is a by-product of your auditory cortex's attempt to rectify the disharmony. That beat is created inside your brain, and is effective at synchronizing your operating frequency to it. We physically note a change in \"mental alertness\" when observing our brains sliding into Theta or Delta waves. A \"beat\" on a guitar string, or even a binaural beat heard through a mono system will still sound like it has the beat, but will be mostly ineffective at harmonizing your brain's operating frequency to it. I use [ URL_0 ](https:// URL_0 ) almost every day. Without stereo headphones it's useless. People saying it's fake are wasting their time watching hypnosis youtubes that AT BEST are totally inert. There is plenty of science behind them. OH and for my own experiment results? I used to play CS:GO every day and had a baseline of performance. When I began to use [ URL_0 ](https:// URL_0 ) set to \"Active\", my performance, and thus my stats, improved drastically starting day one! I tried putting it on \"Fear\" which helped me more in the first 5 minutes of playing, then left me feeling exhausted. Probably because it got my adrenaline pumping hard and fast which left me with an adrenal crash."
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dl1r78 | What are neural networks and deep learning? | Technology | explainlikeimfive | {
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"Deep learning is a type of artificial intelligence and neural networks are mathematical models used to facilitate deep learning and other types of machine learning. At a very basic level, a neural network is a map of mathematical functions called nodes connected by pathways. At one end of the map, we pass in some input, like numbers from a sensor, etc. The first node calculates some output based on the inputs (ex: add all the inputs together and output a 0 if it's negative, or a 1 if it's positive), and passes that output to other nodes so they can use it as an input in *their* calculations. You end up with sometimes thousands of these little nodes doing calculations on the inputs they've received, and spitting out some answer to other nodes. When the last node in this huge chain spits out something, that's your answer. With enough inputs and enough layers and layers of nodes, we can actually find out a lot about patterns in data. The math behind huge neural networks can be almost impossibly complex, but they are actually not so hard to understand at a very basic level.",
"Think of an artificial neural network as a simulation of a biological brain, but for a computer. It's a way that a machine can process data, that’s inspired by our own brains. But, instead of our human neurons and synapses, a neural network uses nodes and layers. Meanwhile, deep learning is a subsection of machine learning. The idea is for the computer to ‘learn’ independently. (Without humans telling it what to look for.) In order for it to be able to 'learn' like this, it has to copy the human brain. Which takes us back to artificial neural networks. So, basically, deep learning is a massive artificial neural network."
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dl64kw | What is AWS and what sort of work is involved? | Technology | explainlikeimfive | {
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"Alcohol withdrawal syndrome is a set of symptoms that can occur following a reduction in alcohol use after a period of excessive use. Symptoms typically include anxiety, shakiness, sweating, vomiting, fast heart rate, and a mild fever. More severe symptoms may include seizures, seeing or hearing things that others do not, and delirium tremens. Symptoms typically begin around six hours following the last drink, are worst at 24 to 72 hours, and improve by seven days. Benzodiazepines are effective for the management of symptoms as well as the prevention of seizures. Certain vitamins are also an important part of the management of alcohol withdrawal syndrome. In those with severe symptoms inpatient care is often required. In those with lesser symptoms treatment at home may be possible with daily visits with a health care provider.",
"In the past, companies would have physical computers in specially cooled rooms that ran important functions such as serving websites, email servers or other specialised software. As the complexity of software increases and the way we consume content evolves, so does the amount of infrastructure required for these companies to work effectively. For many businesses and startups, managing this infrastructure is just something they generally don't want to do. Cloud providers such as AWS (Amazon Web Services), Google Cloud Platform (GCP) and Microsoft Azure (AZ) offer the same infrastructure, without the long term commitment and complications involved with running it yourself. So instead of managing physical servers and networks, replacing faulty components and so on... all of it is controlled over the net using the cloud providers infrastructure instead. Usually these cloud providers aim to simplify consuming common services, by wrapping up functionality in services that abstract away even more complexity. Examples include Amazon S3, which provides a way to store arbitrary bits of information and even serve it over the web globally, all without needing to really think about the disk it's stored on."
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dl6guu | What is the difference between a load balancer and a reverse proxy server? | Technology | explainlikeimfive | {
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"A load balancer directs incoming traffic/sessions to different nodes in a cluster or other grouping of similar servers in order to keep the load on any given server to a reasonable level. A reverse proxy server directs traffic to different servers based on what kind of traffic or session it is. Load balancer: I have 12 Citrix servers, each of which is capable of serving an application session for a user, and each server provides the same applications. The load balancer assigns individual sessions to each server based on its current unused capacity to keep the load on any one server from getting high enough to interfere with performance. Reverse proxy server: I have 12 servers providing different services (database, web content, application, etc). The RPS assigns individual connections or sessions to each server depending on what the incoming traffic is requesting, so that DB requests go to the DB server, web requests go to the web server, and so forth."
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dl788e | In 3D video games, why do character models start to stretch way out and spaz around when they're corrupted? | I see this 3D modeling phenomena in glitch and corruption streams all the time. At some point, the character models will begin to stretch out way more than they are supposed to, sometimes going off camera. Not to mention sometimes they look like they're seizing. Why does this happen? | Technology | explainlikeimfive | {
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"They don't always, bugs can manifest in very different ways. So, this can be one of a couple of things, to my knowledge. First, it could be an animation bug. It'd be really impractical to build a 3D character from a series of 2D images, so they don't. Instead, 3D models have a \"skeleton\" inside them, which is basically a bunch of nodes that the model wraps to. This skeleton can then be manipulated to animate the model. For example, in a walking animation, the animator will create some 'keyframes' of where each 'bone' of the skeleton needs to be at each time, and then fill in the intermediate frames. The animation's end result is usually a set of mathematical instructions saying \"bone X is here and in this orientation. By 300 milliseconds from now, it needs to be over here and in this orientation\". If this data is corrupted, the animation interpreter doesn't really know what to do. The animation is saying \"Bone X needs to get 10 miles away in 300 milliseconds but the rest of the model needs to stay in the same place.\" That is obviously something it can't do, so it stretches the bone to let one end of it be 10 miles away while the other end is still anchored to the model. Since animations are made up of a bunch of this kind of instruction, a sufficiently corrupted animation looks like some abomination seizure since every frame the bones all need to be in completely different places. The other thing could be model issues. A model is a bunch of triangles basically, all defined by a series of numbers that describes their location and relationship to other triangles. If one of these numbers gets messed up temporarily, it can result in one part of the model becoming a big-ass spike."
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dl7ve0 | When inside a large group of people (at a stadium, concert, festival), why does your phones internet data stop working despite having full bars? Why does such a large presence of phones in one area limit every phones’ usability and ability to even simply send a text message? | Technology | explainlikeimfive | {
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"Here's another stadium related analogy... the stadium is designed to accommodate the capacity they let it. There are enough seats, they have sightlines, there are many bathrooms and food stands. You can easily and quickly get to your seat as the flow of people is spread out. This is why you see 5 bars -- the overall system can handle the capacity and proximity. Now, you know how that huge crowd of people come to a slow crawl when all trying to exit the stadium at the same time? Suddenly, the system that could handle the overall capacity bogs down when everybody wants the same thing. This is why you get no/slow data even with 5 bars.",
"Bars only represent the strength of the signal you’re receiving. It does not show you the congestion level of the cellular band or how overloaded a cell site is with everyone’s phone trying to talk at once.",
"Full bars represent your close proximity to a cell tower. But so is everyone else at the stadium/festival. The difference is like you taking a crap in your toilet and 100 people trying to crap in a toilet at the same time. Sure, you are close to the toilet but good luck getting your crap through.",
"The number of bars tells you how close the cell tower is. But the cell tower can only handle so many phones. If it can handle 1000 phones and 20000 people are in the stadium, most will get no useful service.",
"LPT: when this happens, go into your settings and turn off LTE. Your phone will switch to a slower (but less congested) network and you’ll have service again.",
"Think of bars as lanes on a highway. 5 bars = 5 lanes open. 1 bar = 1 lane open. Now, during rush hour even when 5 lanes are open, traffic is usually at a standstill. Same with data, it’s a data-jam basically.",
"Something I can answer! I work in a related field. Hopefully this doesn’t get buried. The receive signal you see on your phone is how good the signal is from the “control channel.” The control channel directs traffic and give you a voice channel assignment when you’re trying to make a phone call. All those bars tell you is how good the receive sensitivity is of the site that your phone is registered to. So that’s what that means. Think of the control channel as a data cable between your computer and your router, but instead that data cable is a radio frequency. The frequency is dependent on the carrier, but that’s how you maintain a data connection between your phone and the site. So your phone maintains a connection to that site via an radio frequency. Part one done. The control channel broadcasts and your phone listens to that control channel for information. Step two: making a call. When you dial your BFF’s phone number a few things are happening. When you push that button to make the call, you’re sending an information packet to the control channel saying “hey I want to make this phone call.” The control channel acknowledges your request and looks for a voice channel for you. There’s a varying number of voice channels available at a site depending on how many users need access. The control channel goes through and finds you a voice channel and sends that back to your phone. The call is set up and a bunch of background network stuff happens to deliver the voice from point A to point B. Step three: call ends. On the cellular network, when you hang up, that voice channel you were using becomes available for the next call. So on and so forth. Now this is happening with hundreds of devices at any given time. Most cellular can manage voice and data on the same channels. Using the control channel, your data and voice is all being managed by that control channel and it’s also delivering information to your phone. The control channel tells your phone “hey guy/gal call incoming on channel X/text is in inbound” and vice verse. So why do they get congested in stadiums? Because there’s 10’s of thousands of people trying to send data and/or voice calls and the cellular network is doing its best to keep up. When your text hangs it’s because it’s cueing your text. Someone was there before you. You’re essentially waiting in line. Voice is different. You just won’t get a channel and won’t be able to make a call. You typically won’t get any indication this is occurring. But I assure you it’s trying it’s best. Sidenote: This is why cellular networks are terrible in high call volume situations. Especially emergencies.",
"Cell phones are just fancy radios. When it comes down to it, just like only one thing can be broadcast to your car radio on each “channel”, cell phone radios have the same limitations, but with a lot of fancy work to let them manage and share the same space without getting in each other’s way. Imagine a room where a few people upfront are answering questions and have megaphones, and when you want to ask a question you ring a quick bell that doesn’t interfere (too badly) with the people currently talking, but just letting them know to get to you when they are next available. Now, if there are way to many people trying to do that at the same time? The people at the front just get a chorus of bells ringing constantly and can’t hear the questioners and so the “system” grinds to a halt. You can still hear the megaphones just fine (you have good signal strength) but they can’t get any connections completed because then questioners can’t be heard over all of the people indicating they want a connection when’d one becomes available. The solution to this is to break people down into different rooms so that they don’t interfere with each other. As more and more people use cell phones, companies have been making each station smaller, so that those same bands (or channels) can be reused by someone else farther away. Radio stations do this too, but need hundreds of miles separating the channels, which is why each city has different channels in use to not interfere with neighboring ones. But once you get down to a very very small area like a stadium, the signals from one side can still reach most other users in the stadium, so you can’t reuse frequencies once you get down to that smallest area and everyone has to share the exact same spectrum. Everyone is stuck in the same room together that wasn’t designed to take that many questions all at once and adding more speakers or bigger megaphones doesn’t help at all. One of the main advantages of the next generation of cell service, 5g, is that it *doesn’t* carry far at all, and will help break those minimum sized crowded rooms up into smaller ones because you can use frequencies that don’t get interference or connections from even 200 ft away, and so you can put a ton of stations out that only talk to the people in each section of the stadium, kind of similar to how Wi-Fi can handle very dense populations at conventions by having tons and tons of shorter range devices each serving a small chunk of the total.",
"There is a finite uplink speed from the cell tower that feeds the stadium. Whether it is 2 gbps or 20 gbps, the carrier's business decision is going to be to provide the best service at the most likely volume of traffic demand. If a huge game exceeds that demand, there's no quick solution that will relieve the issue. The uplink speed is what it is.",
"Everyone in the stadium (phones) can hear the announcer (tower) over the crowd, and the announcer can hear the crowd itself, but she can't hear any of your individual conversations.",
"You ever see that gif of the girl being pelted with hotdogs? She's the local cell towers, and the hotdogs are you and everyone else trying to use the network.",
"Imagine 10,000 people trying to walk through the same doorway at the same time, and they're all hauling a 2x4 horizontally.",
"Could anyone explain why I (with Verizon) could barely send a text, meanwhile my friend (with ATT) had no problem texting and uploading a photo.",
"Think of your phone as a person yelling everything so loudly that it can be heard miles away. It says everything just right, and the person listening miles away (the cell phone tower) has very good hearing, so usually it works very well. But, if a thousand people are all yelling at once, eventually it doesn't matter how good the cell phone tower's ears are, it will just sound like a loud buzzing sound, just like the crowd does when it's cheering or booing the sports team. The tower can't hear you, so neither can the Internet. URL_0"
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dl8c4m | Google Stadia | Technology | explainlikeimfive | {
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"It's a video game streaming application/ console. If you don't have really good internet it won't work properly. You play the game directly from the cloud instead of downloading it to a console.",
"The goal is that you can effectively stream games, requiring only internet, the dongle, and a TV to play instead of a full console or powerful PC. Before Netflix streamed movies you needed a device to decode the DVD/VHS to display the movie. No installations, little hardware requirements. I'm signed up, and I'll reply with first impressions if I remember."
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dlb0zx | Do products like Nespresso machines actually need to be regularly "descaled?" | Is this just a marketing tactic for consumers to purchase "descaling solution?" Is every 6 months or so actually how often a machine like this needs to be descaled? | Technology | explainlikeimfive | {
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"I use diluted vinegar in my coffee maker. Cheap and easy. I don’t know about those that have pods."
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dlbuz1 | Who is the owner of all the .com domain names? When I'm paying for one, what does the company actually do in order to generate it for me? It's not like they've already have it and they'll just hand it over to me. It never existed in the first place. | Technology | explainlikeimfive | {
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"Websites are just files on a computer somewhere. That computer has an address, just like your house. But people would rather use a word in the browser to go directly to the site, not the series of numbers which is the address of the computer. And so when someone types in the name, a computer out in the internet needs to convert the word into an address of the specific computer the relevant files are stored in. Someone needs to keep that list and allow for changes, otherwise there would be difficulties reaching the site you want. But people all over the world need the list to be available, so there are computers out there that have all the address information. And they need to be all the same, that way you know what to expect when you use a specific name, no matter where you are. And this is a complicated thing, so smart people have to make sure it always works. And they also have to make sure that if someone wants a name to correspond to their computer and no one else's computer, someone needs to make sure that there are no names used twice. And there are so many people wanting an internet lookup name for their website that it is an important job with lots of work to do, and someone has to pay those people. And if these names were free, big businesses would buy up all the possible names, and you couldn't get any names because they are all gone. Some companies figured out how to get a name registered on the list, so they help others do it, but they need to be able to buy food, so they have to be paid.",
"It's the equivilant of paying to be listed in the Yellow Pages, if you are old enough to be familiar with that. All computers and other devices on a network get an IP address that is like a phone number and the internet is one giant network. If you want to communicate with a computer, you can use it's IP address. You can even put the IP address directly into your web browser and it will work if the device has a webpage setup to answer anything that tries to \"call\" it. Think of that website as an answering machine. When you say, type in the address for reddit in your browser, what you are really doing is consutling a directory to find out what IP address reddit has it's stuff parked out. Theres another big computer somewhere that holds all the stuff for reddit (and possibly other websites, but reddit is big enough to have its own) called a server and you are actually contacting that computer and asking it to hook you up with it's answering machine. It spits out the website you are using now and sends it to your computer. So when you buy a .com (or any other domain) you are paying for the right to use that address to name whatever IP your website used and that domain name is listed as belonging to that IP in every address book online. So, ip = phone number, domain name = name of the person using that phone number. Your web browser automatically looks up and dials the number for you and the other computer says hello by sending you a web page.",
"You are paying for a public Domain Naming Service to redirect people to the webpage associated with that name.",
"These are great answers. But, how could people start selling them? Like how did the founder of GoDaddy just start selling them?",
"the legality of it is fussy - ICANN could be said to be the group which owns all the domains of that type - as well as any others. URL_0 above is a list of \"registrars\" who ICANN trusts to register domains safely and properly for reasonable users. The fact that child porn domains aren't common to the point where neither me nor you have ever seen one could be largely accredited to them. maybe. who knows. some companies, like alphabet inc, will directly register a domain from ICANN. because they can. anyway, icann's standard is what almost all public DNS' use as the standard."
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dlj067 | What causes physics to appear realistic in animations / CGI? | Subtle things like how does one convey weight in movement, jumps, gait etc.? How does the human eye identify something as being readily computer generated (when done badly) w.r.t movement? | Technology | explainlikeimfive | {
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"There are basically three ways you can try to make something appear realistic: 1. Take what we know about how the things behave, use (or create) mathematical formulas that describe that movement, and implement those things in a computer program: Pros: Can be quick, easy, and cheap; Cons: the quicker, easier, and more cheaply you decide, the less realistic it appears. Even then, the math here doesn't always encompass everything. 2. Use a form of artificial intelligence to learn about reality in an attempt to emulate it. Pros: Over time can come up with some eerily accurate things. Cons: Expensive and time consuming. 3. Slap sensors on the thing you want to emulate. Make it do all the things you want to emulate and record the information. Pros: Is about as real as you can get. Cons: Only really good for humans. How can we tell when things aren't realistic? Well, you have an entire life spent looking at the real world. Your brain, outside the tiny nubs that run your body, is basically a squishy pattern recognition machine. So when it sees a pattern that it thinks it knows (a human being) but that pattern doesn't behave the way it should (unrealistic depiction), it throws off alerts basically telling you something is wrong. This is known as the uncanny valley and why things like zombies and super realistic robots are \"creepy.\" They're close enough to being a human that our brain expects them to be human, but off just enough to throw up red flags."
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dlmb0l | Why are there still BLACK BARS on the top and bottom of some TV shows and movies despite viewing them on a widescreen TV? | Technology | explainlikeimfive | {
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"The aspect ratio of the source material doesn't fit or match the aspect ratio of your screen. A widescreen HD TV is 16:9. Old non HD TV was typically 4:3. A lot of movies now aren't filmed in 16:9 they're filmed in an even wider 21:9 aspect ratio, so they still get \"letterboxed\". As to why movies are still filmed in this (and other) wide formats, I can't tell ya.",
"Because different movies are shot in different shapes. Some are made extra-widescreen so that in order to show the whole image, there will be some blank space above and below.",
"Cinema is often shot at 2.39:1 (that was intentionally wide in order to differentiate films from 4:3 television). When it was relatively new, movies could be considerably wider. A few movies from the very wide era, remain classics today. Your 16:9 television was picked as a compromise between the classic movie format of 2.39:1 and the then 4:3 standard of TV. The idea being that there would be bars on each type of content but the bars would average out to being smaller than if other sizes were used. TV pretty quickly matched the new screen size, and some movies followed, while other movies are still shot in the older wide formats. In both 4:3 and 16:9 television formats, movies can be shown with black bars, or cropped to fit the narrower screen. Broadcasters make a choice based on what they believe their audience would prefer.",
"At the risk of repeating what others say, here's my version, with how I understand it, and my own questions: So originally movies were filmed in the ratio 4:3, where for every 4 inches wide it's 3 inches high. Let's call this \"square.\" So we're talking about like the old silent movie and black and white days. The \"square\" is the shape of pictures and film reels, so it all made sense. The TV's came out so logically they made them the shape of movie screens. Then the movie business was afraid of losing customers to the convenience of TV so they started filming wider screens to offer a grander experience. But that meant there was no one standard any more and you had different ratios all over the place. Thus black bars. Then widescreen TV's came out because now they had to catch up and because there's no one side for movies they came up with 16:9, which is kind of in the middle of everything. So that's gonna mean different size black bars for different movies. & #x200B; What I don't understand is NEW TV shows that have black bars- this must mean that TV show producers are choosing to film wider screen than what fits on common TV's. Which I don't get.",
"This may explain part of the reason: Most TV shows and commercials are shot with an aspect ratio (height vs width) that fits your wide screen TV. However, some movies old and new are shot in a wider aspect ratio. If they showed the movie on your TV the sides of the images would be cut off. So you can see the whole image (as it was meant to be seen) they put black bars at the top and bottom.",
"It's already been said below but yeah it's just about aspect ratio. It's funny because movie trailers will sometimes play in full screen for my 21:9 monitor and cover the whole thing, BUT in a lot of cases I still just end up with black bars because a lot of trailers are exported at 16:9 making the black bars kind of.... artificial I guess.",
"Your display has a native aspect ratio(width to height ratio), most likely 16:9(or 1.78:1) but this may not be the true aspect of the content you are watching. Anamorphic wide screen is 2.39:1 for example is much wider. Now to fit that into your screens 1.78:1 screen without scaling and distorting it you will need the black bars to preserve the original picture and not stretch it out and distort it or crop out any footage to fill the screen. Same goes for if you are watching 4:3(square video designed for tube TVs) on a 16:9 flat screen only this would be called pillar box and have the bars on the sides instead of stretching the square out into a rectangle to fill the space.",
"Sometimes, if what you're watching is old enough to predate actual widescreen TVs, back in the day of 4:3 DVD the black bars were part of the content to create the illusion of a wider picture in your normal non-wide TV. Then when actual widescreen was a thing some lazy/careless publishers never picked up the master content and just transcoded the old stuff resulting in what you're watching encased in a black box. Some modern TVs are smart enough to recognize this and zoom in, but resolution is still lost.",
"The other replies here have talked about how movies are often shot in an even wider aspect ratio which requires black bars on a regular widescreen TV, but there's also another very annoying reason. When you set up a widescreen show or movie to appear on a 4:3 screen you need to add the black bars. If you then take this 4:3 version of the show/movie and display it on a widescreen it will not necessarily fit on the screen properly. More likely it will be stretched to fit, leaving the black bars and distorting the picture. This was very common when widescreen TVs were first becoming popular since a lot of people didn't know better. It still happens a lot when people connect an older device (ex. a VCR or an old DVD player) to a widescreen TV without properly adjusting the screen ratio.",
"Cinematographer & Director here! ***ELI5 version***: Different image sizes can show scope and scale differently, and make you feel different things emotionally. Sometimes that choice means that you get the black bars on your screen so you can see the film how the filmmakers intended. ***Filmmaker version***: The aspect ratio is indeed the \"why.\" As others have said, older TV's (pre \"flat\" screens, for the most part) displayed an image that was 4:3. Most TV's these days are 16:9, but many movies and occasionally TV shows are often filmed in wider formats of 2.35:1 to 2.4:1. When the wider images is played on a screen that isn't that wide, then the bars get added (\"letterboxing\"). Filmmakers feel like different aspect rations suit their creative vision, is why they are still shot that way. *21:9 is not a format that we capture in specifically, and instead is the ratio of some screens that you can purchase*. This video explains it well, I feel: [ URL_0 ]( URL_0 )"
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dln6ik | How do domain servers (like at a company) and subdomains in Active Directory overlap with website domains/subdomains and DNS servers? | This question may sound dumb but I’m trying to understand this concept. I just assumed these two things aren’t related but I’ve been reading an introduction to networking concepts and apparently “domain trees” include subdomains and involve DNS servers. My understanding gets about as complex as this: Domains are website names you buy. A DNS server is used to tell people your/other people’s domain name is located at this IP address where it is being hosted so that your browser can find the website using only the URL. And a domain like you would have at a job is a collection of computers where the accounts are managed by a domain controller server. The accounts are server side and can be logged into any computer on the domain. The domain certifies that you are who you say you are and in active directory you can tell someone what resources they can access, like another server, which checks that you are who you say you are if the domain controller confirmed it, and then it checks if your identity is allowed access the resource. I’m sure I’m wrong on a lot of stuff here but I’m trying to iron it all out. Now these two different instances of using this vocabulary word I always assumed was coincidence and the concepts weren’t related. But what I’m gathering seems to imply otherwise. Can someone help break this down for me? | Technology | explainlikeimfive | {
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"Ok, so basically, it works like this: When you register a domain, they enter a record for that domain that points towards your DNS server. That DNS server lists the IP addresses for the various services and subdomains you hold. AD is more than DNS, but it is a necessary component. Just like the public domains, your AD domain uses DNS to direct computers to the correct resources. You can use a public domain in your private network (or a subdomain of that domain). Think of domains as a human readable format for IP addresses. In that sense, it functions the same way for private and public domain names. To answer the actual question. The DNS server that is responsible for the domain will respond to DNS requests regarding your domain. How your computers on your network handlenit depends on of that domain is listed in your local DNS server. If it is, it will just use the info from the local server, if it is not, it should make the requests of the authoritative DNS server. I could make a DNS entry for Reddit on my local DNS server that points to 127.0.0.1. That would make reddit unreachable from my network (as long as they are using my DNS servers)."
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dlo3v7 | Why do computers beep? What causes the noise, and what made beeps the universal sound of computer? | They're everywhere, seeming since the advent of electronics beeps have been used. Why? | Technology | explainlikeimfive | {
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"They are made by a tiny speaker, either on the motherboard of the device itself, or in the case itself (wired to the motherboard). Originally, beeps were used because they are very easy to create. Run voltage through a speaker wire at a specific wavelength and, bam, a beep. Much, much easier to do than complicated sounds like speech or music. As to _why_ they beep, the beeps tell you that the computer is doing something without needing a display attached - beeping when the computer boots up tells you the computer booted up _before_ the display drivers initiate, so you can at least know the motherboard is booting.",
"When something is wrong with hardware and it cannot boot normally, the pattern of beeps can hint you what part exactly malfunctions. If your PC beeps when everything is OK, then, well, it's just another pattern, telling you that the parts, one by one, are OK. So in that case if something isn't right, someone who knows the beeps code can listen and figure out like \"uh-huh, the chipset is OK, the CPU is OK, oh, the RAM isn't, let's check it\".",
"Characteristically, a beep is a single tone that has a simplistic waveform, usually a sine wave or square wave. These types of audio signals are really easy to generate with super super basic hardware (think 1 or may be 2 transistors max, plus a few resistors and a capacitor) and so they've been used for decades in electronics, for signalling things like errors (a beep is hard to ignore) or things like button presses."
],
"score": [
10,
7,
3
],
"text_urls": [
[],
[],
[]
]
} | [
"url"
] | [
"url"
] |
dlo52p | why do some regular bedside digital alarm clocks go out of sync by a minute or two over th eperiod of time? | Technology | explainlikeimfive | {
"a_id": [
"f4sh3fr",
"f4spidi"
],
"text": [
"Cheap crystal oscillators I bet. The easiest way to get an oscillating frequency wave (that can be squared into pulses used as a digital circuit 'clock' is to use a quartz crystal. If you put a voltage across one it sends out a wave at its resonant frequency.... and its resonant frequency depends on its physical characteristics, namely its thickness. So the cheaper a crystal, the less care in its manufacture, lower tolerances in maintaining its thickness. So maybe a crystal is supposed to drive a circuit at 60 Hz, but is crappily made so it resonates at 59.6 Hz. That would cause a drift over time since the digital clock is essentially counting these clock ticks. Maybe 60 = 1 second or whatever.",
"Also, the AC frequency of your electrical network provider has to be stable, if it's 51Hz instead of 50, the base frequency used is wrong, and thus all the \"analog\" AC to DC conversions frequencies will be off. It happens with my microwave here in Europe since we started \"importing electricity from abroad with this issue"
],
"score": [
10,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
dlp3wh | why are display sizes constantly increasing? | Technology | explainlikeimfive | {
"a_id": [
"f4svygw"
],
"text": [
"Cost and demand. The cost to produce high quality large screens (and high quality very small screens) has drastically declined, in addition the types of screens we have now, such as LCD/LED screens can be made much better (And smaller) for consumers than the giant CRT screens of the past that would take up half your living room and weigh hundreds of pounds. A 55\" TV used to be a gigantic monster and absurdly priced. Now that same size TV can be made in a thin, light panel and have even a better picture than ever.. and be made a cost that was wildly unthinkable in previous days. You can even find top quality LCD 55\" TVs for stuff like $300! In older days that same TV would have been not as good and cost many thousands of dollars In the same vein, we've got much better and cramming tons of quality into a smaller screen. In one time, a portable 1\" LCD was amazing and the top of technology and bigger screens were insanely expensive. Consumers wanted bigger screens, and companies (like Samsung) developed technologies to make high quality small screens, as such we've seen an abundance of very low cost, very high quality portable screens for things like phones."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
dlq9vp | Browsers sometimes won't load page because there's problem with certificate. What are these certificates and who issues them? Why it's dangerous to open page with invalid one? | Technology | explainlikeimfive | {
"a_id": [
"f4tbclw",
"f4tbt1h",
"f4tnatc",
"f4tq4vj"
],
"text": [
"Certificates are basically ID's for websites. They are issued by a certificate authority that is trusted by other organizations, like the DMV with your driver's license. Your browser knows what companies it can trust to issue certificates, and can follow a path back to validate that a certificate is legit or not. The issue with opening page with invalid certs is that if the cert is invalid, you have no way to know whether or not the site you are trying to visit is actually a legit site or not.",
"**Certificates** are certain digital proofs issued by Authorities like - CA (Certificate Authority) to companies that host websites on the internet. They provide a proof to your browser that yes this site is what it claims to be (the browser crosscheck with that issuing authority). For ex: Yes this is a legit reddit site. Browsers have a way to verify that the proof provided is correct and valid in terms of the longevity of the certificate (dates). It's dangerous to open a site without a valid certificate because of **Phishing** scams - where people make a duplicate site of the original, in order for you to punch in your passwords and other important information. So the Browser will warn you if it sees an invalid or expired certificate.",
"> What are these certificates It's identification - e.g. \"this is URL_0 \". > who issues them? A Certificate Authority (CA) \"signs\" them, cryptographically vouching for the ID. Browsers have a list of CAs and a public key so they can check to see if that signing / vouching is legit. You can run your own CA and sign your own certificates, but that's not worth a lot until you get everyone to trust your CA. > Why it's dangerous to open page with invalid one? Say some site says it's URL_0 , but that vouching doesn't check out. You might log in and someone takes over your account. Not fun, but not as bad as if it happens with your bank's web site. **Edit: Here is a great [presentation]( URL_1 ) on these concepts and some problems with them. It gets a bit technical, but Geoff Huston makes it fairly accessible. Almost everyone will come away being a bit more paranoid about this stuff.**",
"As others have said its basically having a \"trusted\" party vouch for a site. Invalid certificates can be for a variety of reasons, but 95% of them will be because the site didn't provide a certificate that is credible with a \"trusted\" party. Generally this is a big indicator of illegal activity as its easy to get one. The cases where certificates may be invalid but not for criminal activity relate to technical issues on the side of the website host that require someone to clean-up before the site is valid again."
],
"score": [
17,
7,
6,
3
],
"text_urls": [
[],
[],
[
"reddit.com",
"https://www.youtube.com/watch?v=09fNjMur1Gs"
],
[]
]
} | [
"url"
] | [
"url"
] |
|
dlr5fk | What exactly is happening when an ISP sends a refresh signal to your modem? Why does it sometimes improve the connection speed? | Technology | explainlikeimfive | {
"a_id": [
"f4twml7"
],
"text": [
"Over time, the modems at both your end and the ISP end react to noise on the line by slowing down to maintain a stable connection. Resetting the calibration settings on a noisy line can temporarily make the speed faster when it goes back to the default starting speed, but the speed will just decrease again if the underlying reason for the poor line conditions isn't resolved. This is an issue with both Cable and DSL connections, but is more pronounced with DSL, especially if the modem isn't kept powered on continuously for 10 days when the line is first installed (or subsequently reset)."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
dltkm3 | What is happening behind the scenes when a commercial on television is suddenly cut short after a few seconds before it even finishes? Is someone somewhere deciding to switch to a different commercial for time reasons? | Technology | explainlikeimfive | {
"a_id": [
"f4u9rod"
],
"text": [
"Most commercials, both on TV and radio, are now automated. Trigger signals are sent using a subcarrier (part of the audio feed or video feed that is not normally visible or audible) and that triggers a computer. Most shows you see on TV have a mix of both national and local commercials. That's so both the national network and the local station make money. For a typical commercial break, there might be 2 minutes of national commercials, followed by two minutes of local commercials. So when the show goes to break, first you get to see national commercials (at the national network feed center). Then after they play a trigger tone fires and the local commercials play (from the local station). If there are no local commercials, then two more national commercials play. But if that trigger tone is late slightly, or the computer is lagging a bit, then after the two national commercials, you'll start to see the third national (filler) spot, but when the local computer kicks in, it starts showing the correct local commercial and the national one gets cut off after only a second or so. On the radio, you can actually sometimes hear the trigger tone, it sounds like that strange electronic bleep that was at the end of some cassette tapes back in the day. That's why sometimes you'll also see a commercial repeated. If Kellogs has bought national air time, plus local airtime in selected markets for their new Boysenberry Frosted Flakes rollout, then sometimes they will accidentally air in the same commercial break, as the local station rarely knows what national commercials will be playing ahead of theirs. Hope this all makes sense."
],
"score": [
18
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
dlwywf | why aren’t keyboards just abc etc, and instead qwerty? | Technology | explainlikeimfive | {
"a_id": [
"f4uqxcd",
"f4ur4xn",
"f4ur4un"
],
"text": [
"It's a leftover from typewriters. The [Sholes and Glidden typewriter]( URL_0 ) used a ring form with typebars on them for each letter. When you hit two letters next to each other rapidly however, the typebars would collide with each other and cause issues inside the machine. This is where the QWERTY-layout came from. The letters are placed in such a way that letters that are frequently next to each other in the English language are spaced apart to ensure such a collide doesn't happen. This way the amount of collisions is minimized. While this is no longer a problem for computer keyboards, they kept this design (probably because people were used to it).",
"To my understanding, when typewriters were first created they used a keyboard placement that was created to make typing as fast as possible. However due to the keys being physical, fast typers caused a lot of jams. Because of this, typewriter manufacturers spaced out the common keys with the less common to slow down typing speed. Because this fixed the problem, it became the standard for keyboards, and that transferred to computer keyboards. Which is why we have the QWERTY keyboards. Some modern manufacturers have recreated the initial keyboards for those that wish to teach themselves the original key placement for faster typing. These keyboards are known as DVORAK.",
"Keyboards derive from typewriters. Early typewriters worked by smashing bars with little stamps on the paper. However, due to the compact building method, you couldn't press two keys next to each other in a fast pace without jamming the bars into each other. One bar had to go down first before another one in the same area could rise. The keyboard layout was designed to spread out the most used keys into different areas so that jamming was minimized and you could type as fast as possible. That's no longer a problem for modern typewriters or computer keyboards, but the layout is still around because people already know how to use it."
],
"score": [
16,
5,
4
],
"text_urls": [
[
"https://en.wikipedia.org/wiki/Sholes_and_Glidden_typewriter"
],
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
dlxk5m | What does it mean to achieve Quantum Supremacy? | How is it different that the current Super Computers? | Technology | explainlikeimfive | {
"a_id": [
"f4uxsl5",
"f4uwlau"
],
"text": [
"In short, they performed a calculation that would have been impossible on a regular supercomputer in any reasonable time frame. Regular computers work on data stored as 0's and 1's, precisely, and must do one operation at a time per processor. Quantum computers can store data in states that are 0ish and 1ish at the same time. When you check the state, you'll get either 0 or 1 randomly depending on the amount of 0-ness or 1-ness each one had. A quantum computer can manipulate this quantity in a controlled way, and doing so can require many fewer steps. I think in Google's case the calculation they were performing was simulating a quantum system, which quantum computers naturally excel at. It can be done on a supercomputer, but the amount of data and processing required scales exponentially with the size of the problem, whereas on a quantum computer it scales linearly. Google is claiming the problem they solved was so large none of our existing traditional computers would have been able to solve it in anyone's lifetime",
"Imagine you have a toolbox. Inside the toolbox you have a hammer, a hand saw, a screw driver, and some nails. Quantum Supremacy is like you have just bought a roll of duct tape to add to the tool box and used it for the first time to tape two metal rods together that were rattling annoyingly. You could have used the hammer and nails to nail those two metal rods together but that would have really, really, sucked to do. But it would be technically possible. But you have just shown that the duct tape works, and is much, much, much better at this specific task. Anyone who tells you that duck tape will replace hammers and nails for every task is crazy and that isn't what this means. This is just adding another tool to our tool box and showing it works as advertised."
],
"score": [
15,
5
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
dlxs9g | What does this chip do? | Technology | explainlikeimfive | {
"a_id": [
"f4uuilg"
],
"text": [
"It looks like one of those stupid mugs that play music or say something when you lift it up. It’s a simple circuit board that has a tiny piezo electric speaker. Nothing nefarious, just tacky. Let me guess the mug is like Christmas themed or birthday themed or something"
],
"score": [
4
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
dlxwoi | Why is the sound quality of waiting music on phones worse than quality of spoken voice when theoretically it shouldn’t even involve any analog to digital kind of conversion ? | Technology | explainlikeimfive | {
"a_id": [
"f4uv5tn",
"f4uw8mx",
"f4uvqm7"
],
"text": [
"Phones are optimised for frequencies in normal human speech. Music often falls outside of that range.",
"The answer was posted in r/bestof five days ago: URL_0 URL_1",
"Phone calls use only enough bandwidth to make speech reasonably intelligible. The original reason for the low sound quality dates back to analog telephony where they simply couldn’t transmit high enough frequencies for treble very far through the thin copper wires. In modern digital telephony, the low quality remains as a method to help prevent network congestion. It saves a lot of network capacity while being just clear enough for speech. Music usually contains a much wider spectrum of frequencies than a single voice does, so most of its details get stripped away over the phone. Some networks offer telephony in higher sound quality if the phones support it."
],
"score": [
6,
3,
3
],
"text_urls": [
[],
[
"https://www.reddit.com/r/bestof/comments/djsuvf/lordvadr_explains_why_telephone_hold_music_always/",
"https://www.reddit.com/r/AskEngineers/comments/2dwj84/why_does_hold_music_always_sound_so_terrible/cjttw1m/"
],
[]
]
} | [
"url"
] | [
"url"
] |
|
dm59k0 | Why do big V8 drag cars make that constant revving noise when they are idling? | kind of sounds like the engine is revving up a little bit at regular intervals of~1 sec? | Technology | explainlikeimfive | {
"a_id": [
"f4x93i7"
],
"text": [
"Its the result of having something called a radical camshaft. URL_0"
],
"score": [
4
],
"text_urls": [
[
"https://www.answers.com/Q/What_is_a_radical_camshaft"
]
]
} | [
"url"
] | [
"url"
] |
dm833r | How does 'fuel efficiency' work with electric cars? I keep seeing Wh/Mi, but what does that mean? Is a high wh/mi better than a low, or is it the other way around? | Technology | explainlikeimfive | {
"a_id": [
"f4ydl1i"
],
"text": [
"Watt hours are like gas. If you had a battery with 100Wh then you could hook a 100 Watt light bulb to it and the bulb would run for 1 hour. 200 Wh battery would last 2 hours in the same setup. 100Wh/mi means that you can drive 1 mile on that 100Wh battery. 200Wh/mi means that you can only drive half a mile on that same battery. (Or 1 mile on a 200Wh battery) Lower Wh/mi is better."
],
"score": [
8
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
dm9ksj | Why does taking an old battery in and out of the remote usually makes it work again a while longer? | Technology | explainlikeimfive | {
"a_id": [
"f4yqowv"
],
"text": [
"It could also be a dirty contact that is cleaned by removing the battery, or there might be a microprocessor in the RC that needs to be reset by removing the power supply"
],
"score": [
11
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
dm9vwd | . Why does slapping the remote make it work? | Technology | explainlikeimfive | {
"a_id": [
"f4ytfia",
"f4yw4xi"
],
"text": [
"There are flexible metal contacts holding the batteries in place and transferring electricity. These wear over time and become less flexible and/or get covered with leaking battery acid and build up corrosion. Hitting the remote may reestablish electrical connection by moving things slightly or breaking some of that corrosion free. Sometimes enough corrosion or other junk (food crumbs) gets under the buttons so hitting the remote moves whatever is shorting or blocking a button contact.",
"Because the battery is nearly dead but corrosion that has built up on the ends is preventing them from working. Slapping the remote, or swapping the batteries around rubs off enough corrosion for the minimal current needed to work the remote."
],
"score": [
10,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
|
dmb1l0 | How are compact cameras able to deliver a better optical zoom with similar quality than a dslr camera? | I jumped on the dslr train about 7 years ago but was disappointed by the lack of versatility, unless you dump thousands of dollars into lenses. My mother, on the other hand, bought a $400 compact Sony camera and it vastly outshines my Nikon DSLR. She gets 30x optical zoom whereas to get something similar for my camera, I'd have to spend hundreds to a thousand dollars, while having a gigantic arm-sized lens on the camera. The thing that gets me is that it doesn't seem to be much of a difference in quality. (I could be wrong as I haven't had my own lens to try.) I don't know if this sub allows posting of videos, but I'll link a video in the comments using my mother's camera as an example of the zoom. | Technology | explainlikeimfive | {
"a_id": [
"f4z0m35"
],
"text": [
"Smaller sensor. Compact cameras usually have a 2/3 inch sensor while DSLRs usually have an APS-C sensor or larger, which is 3-4 times wider and taller than a 2/3 inch sensor. The smaller the sensor, the smaller the other optical parts of the camera need to be, mainly the lens system. So a DSLR lens needs to be 3-4 times larger (and longer) than a compact camera's lens."
],
"score": [
5
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
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