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8173pt | How do farmers produce millions of batches of coffee/wine that taste the exact same every year? | When you buy a certain bottle of wine or bag of coffee, you expect a certain taste and flavor. Now I'm no farmer, but it seems like it would be extremely difficult to grow millions of beans/grapes that produce the same constant flavor, year after year. Wouldn't there be too many dynamic external factors to account for? | Technology | explainlikeimfive | {
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"It’s not so much about the uniformity of the beans/grapes, as it is about the treatment after harvesting. That’s where the flavor profile can change most.",
"To add to this, most big name “brands” of wine/coffee probably have more processing involved and get their base product (grapes or beans) from several different locations. They also tend to aim to keep their product consistent. However, other “brands” (often the smaller or more fancy ones) actually embrace the taste differences from year to year. That’s why certain vintages are highly sought after. For wine specifically, I suggest you check out the documentary “Somme”. It goes into the details of how the unique weather of each year changes the end product, as well as regional differences and methods used."
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817c0o | Why do public schools (and many offices) exclusively use Internet Explorer? | Technology | explainlikeimfive | {
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"Certain settings in Internet Explorer can be controlled through a Windows Domain environment with something called Group Policy. For instance, you can use Group Policy to enforce the Homepage of IE, whereas Chrome and Firefox would require running extra code on every device to keep the home page set to what you want. Additionally, Chrome and Firefox may allow people to allow extensions to them even if they aren't a system administrator. Depending on the scope of these addons, it just becomes more to manage.",
"Additionally, Many business use SharePoint for their intranet and some SharePoint features don’t play well with Chrome of Firefox.",
"It's easier to choose or develop in-house web applications if you don't have to worry about them working in many different browsers. It's easier to troubleshoot problems if everybody is using the same browser. You don't have to deal with problems where something works in one browser but not in others. Browsers (and their plugins and extensions) are notorious for security problems. If you want to avoid viruses, worms, hacks, etc that exploit security problems, you have to update your software regularly. It is easier to keep one browser up to date than it is to keep several browsers up to date. In tech support, an easier thing to do is almost always cheaper, all else being equal. Internet Explorer comes with Windows. You don't have to make your users or tech support people do anything extra to get it. Users do not like to be told that they have to do things where it's not immediately obvious how that helps them."
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8193bk | what’s physically different about USB versions? | So take usb 2.0 and 3.0 or usb-c, what exactly is it that allows for faster data transfer speeds? | Technology | explainlikeimfive | {
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"For example USB 3.0 has 9 wires while 2,0 has only 4. More wires = more data sent in shorter time. Also 3.0 uses different method of sending signal than 2.0. And for the C version, which I don't know much about. Only info I found is that it has 24-pins and and in the 3.1 version 2 wires can have speeds up to 10Gbit/s.",
"USB2.0 using a differential signal pair to send data one way and then the other. This signal pair historically has had specific allowances made about how poor the connection can be between the host and slave device. In USB3.0 a single differential signal pair is still used to transmit data but a second is used to receive data. This allows for bidirectional data flow between the host and slave which would improve the transfer speed some. The main difference is the differential pairs have much tighter constraints on how good the connection between the devices must be which allows the data to be clocked at a faster rate. This improvement in connection is completed on the PCB, connectors, drivers, receivers and cabling. USB3.0 has an USB2.0 connection in the pinout which is 4 of the pins, and the other 5 are SuperSpeed connections which run at 5Gbps. USB-C is a connector specification only which allows for the USB connector to be connected either direction and was designed to be more future proof then previous generations of connectors. One of the biggest advantages is the support of USB PD which allows for up to 100W of power to be supplied over the cable and has a method for the host and slave to negotiate the voltage and current. u/yashkawitcher mentioned USB3.1 which is really kind of complicated. USB-IF who oversees the specification of USB released an article renaming USB3.0 to USB3.1 Gen 1 and released a new specification called USB3.1 Gen 2 which supports up to 10Gbps using the same connector. When people are talking about these two you may hear USB SuperSpeed which is USB3.1 Gen 1 running at 5Gbps and USB SuperSpeed+ which is USB3.1 Gen 2 running at 10Gbps."
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81ay6c | How exactly does self checkout prevent ppl from stealing, techonologically done, apart from human supervision? | Technology | explainlikeimfive | {
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"One thing it does is weigh the items. If there are more things in the bag than you've scanned, it will summon an employee. This helps prevents you \"forgetting\" to scan something, or scanning something of a lower price. But there *will* be more theft. The question the stores have to consider is: \"is the additional theft worth more than the cost of employing 6 more check out staff?\"",
"Self checkouts main purpose is not to prevent theft, per-say. It’s more of a customer convenience / business cost saving issue. Less humans = less payroll, benefits, etc. Each barcode (upc) has a weight associated with it. When u scan an item, and place it in the baggage area (a scale) the weight increase is measured against what you just scanned. If that weight is more or less than what is programmed / anticipated by the software, it’ll send a message to have an associate to confirm you’re not trying to game the system. It DOES have the potential of stopping people from stealing items they may be too embarrassed to have a human scan for them. But again I think the former are the reasons these machines exist. Also, those machines never need to take bathroom breaks and never talk back to their managers."
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81cn79 | Is image quality capped by the resolution of a screen? | If you have a 12 Mega pixel camera, and you view the photo on a 1080p screen (effectively 2 MP) then how does a better camera resolution (whilst keeping all other factors like light sensor, exposure, etc.) make it a better picture? | Technology | explainlikeimfive | {
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"If we're just talking pixels, then yes. A 1080p screen will only display a max 2.07 Megapixel. However, with higher Megapixel cameras you can take a picture and zoom in. (post processing) without the image becoming blurry. If we disregard focus, lighting etc. So for example, you take a picture of an elephant in the savanna. But you want to have the elephant fill the whole frame. Then you can digitally zoom in and crop and still have a crisp image. Although it will be lower resolution than the original image. I think the biggest reason people use high resolution cameras is so that they can print and display the image on a large canvas. There are canvases that are massive and then you need every Pixel you can get."
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81ctic | Is there any purpose for rocks around train tracks? | Technology | explainlikeimfive | {
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"Yes, Stops crap from growing, keeps drainage/erosion controlled so your tracks will not wash out and cause an incident. Pretty much alotta same reasons why you have gravel driveways.",
"We went over this in class the other day (third year engineering) it’s primary function is reduce vibration. It essentially acts as a dampener. It helps the track from finding its natural frequency and literally shaking itself to pieces. It’s does work for all of the reason above as well but it’s primary use is to stop vibration and transfer it to the ground. However not too well because it can actually be harmful to the building around it if the trains are large enough. Gravel turns out to be more or less perfect.",
"I am a construction manager on railway ( i build tracks). Track ballast has many many reasons. 1) Keeps water away 2) Keeps vegetaions away ( mostly) 3) transfers vibration and weight from trains 4) Keeps track in place in both horizontal and vertical way which is probably the most important part. Especially when track is welded together it has enormous pressure especially in high temp. And if track is not properly filled with balast it can deviate from place. Not only its cheaper than lets say concerete. Its also easier to maintan and its easier to do track maintanance becuase you can just change sleevers, or even the actual ballast. In my country its fraction 32-63 cm. Ask me more if you want.",
"Being in pieces, gravel has some \"give,\" meaning it can compress under the weight of a train. Being rough on its sides, gravel only compresses so far. In addition, water can easily drain through, and it's cheap and local in most of the world. That's why it's been used as *ballast* to hold and cushion railroad tracks almost since railroads were invented."
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81db84 | How does Quick Charge work? | I mean shouldnt it depend on how powerful the adapter is? Or does it have something to do with the type of battery, programming the phone? Is it a marketing term companies use to sell more phones? | Technology | explainlikeimfive | {
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"Fast charge uses a microcontroller in the charger, to communicate with the phone, and the two devices negotiate, and decide what current and voltage to charge at. Despite what the previous poster says, a USB fast charger will only up the voltage or current if the recipient device agrees. This means its safe to use on a non fast-charge device."
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81dq1u | why does notepad on windows save files with an asterisk? | Technology | explainlikeimfive | {
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"The asterisk means: \"Replace with your own text.\" Notepad is one of the simplest applications you can get, and is mainly included as the default application for things like viewing readme files, not much more than that. When you save a file in Windows, and you choose a format from the drop-down list, it gives you not just the name of the format, but the extension or extensions that format uses; for example: * Batch file (\\*.bat; \\*.cmd; \\*.nt) * Java source file (\\*.java) * All files (\\*.\\*) * ...etc. The asterisk is simply used as a placeholder for your own text. Notepad only has the one format in that menu. And, as simple-minded as it is, when you select it in the Save dialogue, it will simply copy the extension into the filename box, placeholder and all. However, it will also highlight that text. You can simply go ahead and type the file name. If you have \\*.txt selected, it will automatically save it as a text file and add the file extension without you having to type it (although you can type it if you want)."
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81g4ov | How it is possible to have a cellphone conversation with a person on the other side of the planet in near real time... | How are the signals able to travel so quickly as to seem nearly instantaneous? I would understand if it was light, but aren't cell signals more akin to sound waves? Sorcery I say... | Technology | explainlikeimfive | {
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"No, they are radio waves. Sound waves are matter moving and compressing, just like a physical water wave. Light, radio waves, and the like, are electromagnetic waves that travel at the speed of light."
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81i7a0 | My tongue at the end of a USB cable attached to my laptop counts as an unrecognized device | Technology | explainlikeimfive | {
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"Yes: the port can detect *something* is attached, but can't tell what it is, because your tongue doesn't communicate via the USB standard :-P",
"Yes. The USB protocol has some back-and-forth where the computer asks the device what it is. That's how a keyboard gets identified as a keyboard and a thumb drive gets identified as a storage medium. When you tough your tongue to the leads of a cable it's enough for your computer to recognize that a device is plugged in, but your tongue does not identify itself according to the USB standard so your computer doesn't know how to talk to your tongue."
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81o4yb | How do websites determine whether or not you have a capital letter, a number, etc in your password if they never actually get the password, just its hash? | Say a website wants my password to have at least one uppercase letter, one lower case letter, and a number. * I try *password123* * That string gets hashed and sent to the website * Supposedly the website only ever has the hash, not the actual string, right? For security reasons? * But if a hash is a nonreversible function, then how does the website know to tell me that I don't have an uppercase letter in my password? Thank you in advance from us all! | Technology | explainlikeimfive | {
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"The cleartext is checked before it's submitted and hashed, usually by a client-side script. That's pretty normal behavior and there's no security risks there. Even if it's submitted in cleartext for validation and your connection is secure, then you've little to worry about. If they've broken the session encryption and can see the password cleartext then there's probably security breaches that make your password meaningless for validation anyway. Overall, it's better to validate it on the client side. Where you should see big warning signs is if you go to change your password and are told it's too similar to a previous one. That means they're storing the cleartext somewhere to compare it against and that's a Very Bad Thing. Catching exact matches to previous passwords isn't a warning sign (since identical passwords will have identical hashes they can compare). Of course, password rules like are, in general, a bad idea. Passphrases consisting of several randomly-selected regular words (\"bovine stoneware eatery drapery rimless nail ogle petty\" for example) are much, much better options for passwords.",
"The clear text* is sent to the server, which processes it and then stores it as a hash. If the client submitted the hash that was stored, the purpose of hashing it would be lost** - anyone who got hold of the hashed passwords would not need to get the original password in order to log into your account, just send the hashed version. *It's clear text within the context of the session, but if you are logging in it should be going over HTTPS, meaning that the whole session will be encrypted. **Assuming their hash/salt is different to other websites, it would at least protect you from them using it on different websites, but you shouldn't be reusing passwords anyway and websites don't really care if they hack your account on someone else's website."
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81o5os | What are NAT Type and UPNP and how do they affect my internet experience? | Basically all i know is what NAT AND UPNP Stand for and they seem to be causing me problems that my isp doesnt want to help me fix | Technology | explainlikeimfive | {
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"Internet communications get where they are going using an address, your IP address, which is unique worldwide. If a message is sent to your IP it will get to you specifically. The address is recorded as 32 binary digits, or bits. The problem then is that there are only 4 million combinations with 32 bits and a lot more than 4 million devices on the internet. To get around this smaller networks will have one IP address facing the internet at the router, and everything inside the network has a local or private IP address. Now when you send a message out to the internet expecting a reply your router repackages it with a special return code and sends it on. When it gets the reply with that return code it knows the reply is for you and not the router itself or your roommates phone. This is basically what NAT does, it translates between the public IP address and the private IP address. This leaves another problem, you have to make the initial outgoing message so that your router can mark it, and now no-one can just send a new message to you first. So how do two people that are each behind a NAT router talk to each other if neither is able to listen? Some routers allow devices on the private network to tell them \"please forward me any messages you get with return code X\". If your program asks for this and the router supports it then it will set up this forwarding rule for you and you are now open to receiving messages and listening to anyone using that return code. The program you use is configured to use specific return codes, so it knows what return codes to send out with. This is, very basically, UPnP. So NAT allows for one public IP address to sit in front of many private IP addresses and send messages back and forth keeping track of which messages are for whom. UPnP is asking your NAT to leave a messaging channel open for you."
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81qg80 | Parsing Data | Technology | explainlikeimfive | {
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"There are many different data formats and the process may be different and/or more complex but here's a simple example: Let's say you have a text file in CSV format (comma separated value) with some customer data (name, age and email): Alice,24,[email protected] Bob,19,[email protected] Alex,32,[email protected] To parse this, you could read the file line by line, split each line at the \",\" and put the three parts of each line into an array, then append that to another array. you end up with an array that has another array for each line, each with three elements in it. Technically that's all there is for actual parsing, building a meaningful data structure from that that is useful inside your program is a separate process called \"lexing\" but very often the two are just referred to as \"parsing\". One way of flexing this data would be to go through the top level array and convert each entry into an data structure called a \"struct\" which is a collection of names fields with their values, like: {name: \"Alice\", age: \"24\", email: \"[email protected]\"} Done."
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81so13 | How limiting is developing software on older systems like Mac OS System 7 or Windows 95 compared to newer systems? | Technology | explainlikeimfive | {
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"Do you mean besides there being almost no user base for an operating system that old? Or that it is no longer maintained by the developer of that OS, so no bug patches, security or driver updates? Or that the hardware it runs on is also likely to be ancient? Or that you won't have access to the latest API?"
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81t81x | What exactly is the process to make lab grown meat? | Technology | explainlikeimfive | {
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"Oh I can answer this! You have to consider what 'meat' actually is. Meat is animal muscle, but even that is a bit vague; muscle is a combination of muscle cells, muscle fibers, blood vessels, fat, nerves, connective tissues etc etc all in completely different ratios and animal types depending on what exactly the cut and animal is. So the obvious first problem is to decide what kind of meat you are trying to make in the lab. Then you need to find out what the exact makeup of that type of meat is. This is annoying time-consuming work, but perfectly possible with the tools we have. The main problem is in trying to copy the 'real' meat. I'll start off; copying an actual steak or any cut of meat with a complex _structure_ is out of the question for the coming decade. The best we can hope to achieve in the short term is minced-meat style; essentially a meaty slurry that includes hamburgers, sausages, chicken nuggets and thinks like that. Muscle is the prime component of meat, so that comes first. So we start with taking a sample of muscle cells from, say, a cow. Then you start growing it. We are far enough advanced in cell culture techniques that you can get a huge supply of muscle cells from animal samples. That is the easy part. The difficult part is to make it 'meaty'. With that I mean including the right amounts of fat and connective tissue. Because of limitations in these cell culture techniques, right now you kind of make a whole bunch of tiny slices of muscle tissue and then mash them together into a burger patty. In 2013, there was a 'tasting' of one of the first lab-grown 'burgers' ( URL_0 ). It doesn't taste quite like meat yet, it tastes like how pure muscle fiber and cells would taste. tldr version; Current procedure; 1) Harvest cells from an animal, 2) grow the cells to huge numbers of muscle cells in thin layers, 3) mash the muscle cells together for something resembling meat. Future challenges; 1) Find a way to incorporate other types of cells as well, 2) Find a way to get 'structured' meat like steaks, chicken breasts and basically all of the 'good' meats, 3) Make the process affordable, 4) Find a way to do the cell culturing without needing animal side products(a). # (a) In most tissue culture techniques, you use a slaughterhouse side-product to give the cells a cocktail of nutrients to help them grow. Obviously this is going to be a problem if you theoretically don't have slaughterhouses any more."
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81vo6y | Why do lights get brighter before they die? | Technology | explainlikeimfive | {
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"An incandescent light bulb works by making a tungsten filament so hot that it glows in the visible spectrum. The main failure mode of a tungsten filament is that it is so hot that it slowly evaporates. It gets thinner and thinner until either on its own or due to a minor mechanical or thermal shock, it breaks. Just before this happens, it can get a *very* thin spot. That significantly increases the electrical resistance at that spot, which makes it get even hotter, and thus brighter. That increased brightness is temporary, since the increased temperature will shortly cause it to melt open and thus fail."
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81x7gt | The difference between source code, and what we download when we buy a game | I'm not even sure I'm asking this question correctly; that's how far removed I am. I remember reading that someone had found starcraft source code and the internet lost their minds when he turned it in. | Technology | explainlikeimfive | {
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"When you write a computer program, you write it using a human readable language, for example C, Java or Python. For example, this is what a basic \"Hello world\" program (a program that print \"hello, world\") looks like in C: #include < stdio.h > main( ) { printf(\"hello, world\\n\"); } Things like \"include\", \"main\" and \"printf\" are instructions for the computer that tell it what to do. The computer, however, doesn't actually know what this code means. Instead, the code first needs to be translated to \"machine code\", which the computer does understand, but is very difficult for humans to read and understand. This process is known as \"compilation\". When you download a game, the game's executable files are already in machine code, after the compilation process was done. This means that you can't really understand how the game works just by looking at the files. However, if you have the original source code, it means that by looking at it you can figure out how exactly it works.",
"Over-simplifying it but it's like the difference between a recipe and a cake. Source Code is the magic ingredients that you put together and then bake (compile) to create a program (executable) that your Operating System (likely Windows) can run. Now, when you look at a cake you you don't know what it's made of but you know the purpose of a cake and how to use it. Of course, if you're a baker then you could likely look at a cake and know what goes in it and roughly how it's made but you'd still need the recipe to accurately re-create it. Same with developers. When you look at a program you can think of all the functions and sub-systems that make it and how you'd go about creating them but you don't know exactly how they were written. I could go into much deeper explanations on both coding and baking but I hope the above conveys the meaning.",
"Another reason why people are excited for starcraft source code is, with it we can now make fundamental changes to the code without the limitations of modding (such as making remastered version, adding 4K support), compile it to newer platforms like the latest versions of windows, linux and mac os...etc. This was exactly what happened very shortly after the source code of starcraft was published.",
"If you think of code as the logic describing what a program should do, then it can be expressed in many different languages. you could describe it informally in English or any other human language (if x is two then do this, otherwise do that. Then do this other thing. Keep doing this until the user presses cancel\"). It can also be expressed in programming languages, which are generally human-readable, looking like a mix of maths and English. For example, the following is a very simple application written in the C++ programming language: #include < iostream > int main() { std::cout < < \"hello world\\n\"; } You could express the same thing in English (write the string \"hello world\" followed by a line break to the application's standard output. Then set the exit code to zero and terminate\"). But the computer doesn't understand either English or C++. It understands its own language of 0's and 1's. For example, the processor in your PC understands the byte `00000100` as an \"add\" instruction. It means \"read the byte after this, and add it to the value stored in register \"A\". So what programmers do is they write their code in a programming language such as C++, and then they run it through a compiler, an application which is able to translate code from a programming language to some other language. In this case, the compiler translates the code the programmer wrote into machine code, the language that your processor understands. In that case, the source code is the code I wrote (the C++ snippet above). And a compiler can translate that into an executable program that my computer can run. So if someone got hold of the Starcraft source code, as you mention, then they would in principle be able to make changes to the source code, compile it, and get a slightly different version of the game. (I say in principle, because while they could do that, they would be missing all the non-code assets. All the 3d models and textures and scripts and audio files and everything else that makes it a game)",
"Think of it like the difference between owning a car and owning all the parts to a car. Having all the parts allows you to see exactly how it works - even if you don't understand it completely. But you can't sit in and just drive it. You need something to build and test it before you can use it. That's what a [compiler]( URL_0 ) is used for.",
"The simplest possible explanation: Source code a program expressed in a language that is easy to edit and understand. This then gets translated in to a language that is easy for computers to understand and is then sold to you in that form.",
"A source code is like a blueprint of a house. It tells the carpenter how to build the house. Obviously, you can't live in a blueprint much like how you can't play the source code. The game you download is like the house itself built by a compiler which is like the carpenter of the house.",
"Not sure if someone has said this yet, but source code has the additional advantage that a human can edit it to change certain features. Yes, you need to know how to program and there’s a chance you’ll break something else by making a change, especially in big projects. Also it allows you to run it on a machine other than the exact one it was released for.",
"Computers understand 0s and 1s. Certain sequences have a meaning to the computer and that's how you tell it what to do. However, those are very basic instructions and it's very hard to make complex programs using just these. So, we made a program that translates a language a bit easier for us to understand, to the computer language. This is a compiler. Then we made even more complex languages that add a lot of abstraction allowing us to make complex operations with simple instructions and to not care about many low level details. These languages are then compiled to the computer language, which results in something really hard to understand. That's why the source is so important, it allows to understand how the program is made to work, the logic behind it. **tl;dr** programming languages add a level of abstraction that allows humans to write complex programs, that's the source code, it then gets translated to the language the machine actually understands, which is really hard to understand, and this is what you usually download.",
"Everyone else is describing this top-down, saying things like \"the computer doesn't understand source code, only machine code\", and I thought I'd try to clarify that a bit with a more bottom-up approach. You can think of a CPU as a machine that accepts instructions and acts based on those instructions. Each instruction is given as a set of bits, where each bit is either on or off, yes or no, true or false. You can think of this as a set of switches. Since you likely have a 64-bit processor, that would be 64 switches. Each switch is connected to the processor. Each instruction is a particular configuration of these switches. These instructions, sets of on/off bits, are usually actually an instruction in less than 64 bits, things like ADD or MOVE, as well as one or two parameters. These parameters might be plain numbers, or \"registers\" (really fast variables that live in the processor), or locations in cache (bigger/slower in-processor memory) or RAM (even bigger/slower memory that exists separately from the processor). So an instruction might be `ADD $1 $2 $3`, meaning add the two numbers stored in registers $1 and $2, and store the resulting sum in register $3. The point is, these instructions are incredibly simple. Inside the processor, there is physical circuitry that, based on which of those 64 inputs is on or off, will perform the desired action. These commands are read in once every clock cycle or every few clock cycles, so a 2ghz (2000000000 cycles per second) will perform on the order of 10^9 instructions every second. So these instructions, built of groups of 64 sets on/off inputs, are what the computer \"understands\". These numbers are collectively referred to as \"machine code\" The human-readable version of these numbers, that might look like `ADD $1 $2 $3`, are referred to as \"assembly code\". Assembly code is effectively the same as machine code, since converting a line of assembly to machine code is a fairly trivial problem; a program that does so is an \"assembler\". As mentioned earlier, these instructions are very simple, and aren't actually structured. If you want to have a block of instructions declared as a \"function\" that other blocks of instructions can call repeatedly, your instructions have to handle all of that manually (store the current instruction's location somewhere, jump to the function's first instruction, then the function's last instruction read's the location from somewhere and jumps back). But modern programming languages are much more complicated than that. They include built in functionality for common tasks, like repeating the same code over and over (a loop) or calling a particular block of code from many other places in the code (a function), as well as things like advanced data structures or common algorithms in standard libraries. So a program written in one of these modern languages is referred to as \"source code\". It's just plain text, and it's easy for humans to read. But in order to get a computer to run it, it must be converted into \"machine code\" by a compiler. Because source code is more complex and expressive while machine code is much simpler, converting from machine code to easily-understandable source code is not easy or even possible. Because of this, most proprietary software, like video games, is released only in machine code form; on top of that being the form you need in order to actually run the software, it also makes it difficult for anyone to actually get their hands on the source code. At the scale of a modern video game or major piece of software, modifying the machine code directly in any meaningful way becomes extremely difficult and time consuming, especially given that a lot of proprietary software is actually specifically compiled in a way that makes understanding the machine code even more difficult than normal (\"obfuscation\"). This means that, while the creator of the software can implement changes with relative ease by modifying the source code and recompiling, anyone else trying to modify the machine code directly is going to have a bad time. (It should also be noted that not all programming languages behave like this. For example, python code is executed without being compiled even though it's a high level programming language, not machine code. In this case, the python source code is read and executed by an \"interpreter\", a program that reads and executes source code without compiling. The benefits here are that the code doesn't have to be compiled first and will run on any machine/OS that has a python interpreter installed. The downsides are that the program will run significantly slower, and the source code can't be obfuscated into machine code as a form of copy protection.) So, tl;dr, \"machine code\" is instructions that the circuits inside a processor can execute, \"source code\" is a program in a high level programming language that's easy for humans to work with, \"source code\" must be \"compiled\" to \"machine code\" in order for the computer to run it, and \"machine code\" cannot be easily converted back into \"source code\". Disclaimer: many statements made in this post have been simplified for ease of understanding, possibly to the point that they are no longer technically correct"
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81y9x1 | Why are smartphone fingerprint scanners so quick and responsive, but laptop fingerprint scanners always seem to be so gimmicky and ineffective? | Technology | explainlikeimfive | {
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"phones dont actually scan your entire fingerprint. that's why you have to tap it a bunch of times during setup, so it can unlock even from a partial print. it's faster, but less secure havent used a laptop scanner but from what i've seen they're bigger than the ones on phones, so it's possible they scan the entire print to be more secure (of course, neither method is very secure since they rely on a data-set you leave on every object you touch)",
"The first phones with fingerprint scanners were also gimmicky and ineffective. The first model I recall with one was the Motorola Atrix. It had the same kind of crappy fingerprint scanner you’d find in laptops. Honestly, they just suck. But to actually be useful, a phone fingerprint scanner has to be *much* better. Logging into your computer is a very deliberate process that you do maybe a few times a day. Logging into your phone is something you can easily do 100 times a day, and often while barely paying attention. Fingerprint scanners didn’t become mainstream on phones until new generations of scanners became available that were far faster and more accurate. They’re better because they need to be better. Laptops will never even *need* the same level of responsiveness since you don’t use them as frequently (though the MacBook Pro at least does offer a model that uses the same phone-quality scanner)."
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820qe5 | How does a cars speedometer know not to increase when a cars tires are spinning? | I'm not very car smart, and this question popped in my head today. Somebody help me out with this one. And too add to this, how would my car know I'm slowing down even when ABS is kicking in? Thanks in advance all! | Technology | explainlikeimfive | {
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"It does not know. It assumes the tires are in proper contact with the ground, and when they are not, it gives an incorrect reading. Future speedometers may be corrected using GPS, but that generally is not done today.",
"I haven't worked on a newer car, but on older cars the speedometer is driven by a cable/gear on the transmission. I'd imagine newer cars do something similar, albeit without the cable. Tire speed is not used for the speedometer. This is why changing tire size often requires the speedometer to be recalibrated.",
"When your tires spin, the speedometer says you're going faster than you are actually going. It only knows about the tires. If you lift a car with a crane and drop it nose first, the speedometer says 0 all the way to the ground. It's only an approximation of your speed, designed to be pretty good in normal driving conditions. Anything else would cost way too much."
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821riy | Why do PC manufacturers continue to release new computers with McAfee or Norton installed even though they slow down computers? | Technology | explainlikeimfive | {
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"They get revenue sharing whenever a user subscribes. also, those brands still carry weight with a majority of non-tech savy customers, they believe these programs are important and beneficial.",
"Short answer: money Long answer: software manufacturer A goes to pc manufacturer B and says \"I'll pay you X dollars for every pc that you build with my software pre installed from here to year Y\". B agrees, contracts are signed, products are made, money flows, you can still delete the useless bloatware, everyone is happy. Until Y year comes and the contract expires B cannot stop installing the software or the kind attorney C, representing A, will make him an homeless man in less than a second"
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824s5w | Why do bitmap graphics lose quality when they are resized? | Cant find anything on Google Edit: Added a flair | Technology | explainlikeimfive | {
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"Imagine you scale up an image with 2x2 pixels by a factor of 1.5, so that it has 3x3 pixels. The image is very simple: It's a white column on the left, and a black column on the right. Now you somehow have to insert a third column into the image: You can either make it white like the pixels on the left, you can make it black like the pixels on the right, or you can choose a color in between the two columns, which is grey. All three options look different from the original image: Either you now have two columns which don't have the same size, or you now have an additional grey column, which wasn't there in the original image. The first two options have a very visible negative impact on image quality, since they can create a staircase effect on slanted lines, kinda like the top line in [this image]( URL_0 ). So usually, you would go with an algorithm that takes the color of all neighboring pixels into account, and finds an average value of all their colors, which would make the line look a bit like the bottom one in the image. This will blur the image a bit, but the overall impact on quality is much less severe."
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825wdc | Why does a 60 inch 4k TV (60HZ) cost roughly the same as a 28 inch 4k PC monitor (60hz)? | Technology | explainlikeimfive | {
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"Are you sure about that? A quick Amazon search shows me that 60'' 4K TVs cost about twice as much as 28'' 4K monitors. URL_0 URL_1"
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826303 | How do physical disk readers identify music "tracks" on the disc? How do they know where to stop/start? | More specifically, if a disc has 12 "tracks" and the disc reader knows how to read it so that it doesn't overlap or combine music, what mechanism allows for this? Are there headers at the beginning of the track or file that allows it to recognize start and at the end for stop? | Technology | explainlikeimfive | {
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"The same way your computer knows how to read files on your hard disk. Audio CDs have a specific format called CDDA for Compact Disk Digital Audio. The format specifies a Table of Contents section that indicates the location of each track on the disk. The CD player is just a small special purpose computer. It has been programmed to understand the CDDA format. So, the program that reads the disk checks the Table of Contents on the disk, sees there are 12 tracks with track 1 starting at location X, track 2 starting at location X + 4:00, etc..etc... When you hit \"Next Track\" it simply tells the CD player to jump to the location specified in the Table of Contents and start playing from there. The same essential idea exists for things like DVDs. A standardized format for laying out data on the disk is adopted, which any device can then use to implement a program for reading data off of it. This is the same way your file system works on your computer's hard disk. The data is laid out in a certain format, with a root directory in a well known location. That root directory is a list of files and other sub-directories it contains. So in the case of your computer file system, the Table of Contents is decentralized, forming a tree structure. In addition the file system itself doesn't specify a format for the individual files, instead allowing arbitrary file formats. The \"files\" in the CDDA specification are of one specific format."
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826o86 | The differences between a guitar/bass amp, pre-amp, head, and PA. | Technology | explainlikeimfive | {
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"**Pre-amp**: electrical signals from microphones, guitar pickups, and so on, are usually very small, and too weak to travel through wires to other equipment or to be used as input to other circuits. A pre-amp is a specialized amp that boosts the signals so they can get to where we need them, usually with high fidelity and very little alteration. **Guitar/bass amp**: Electric instruments go through a sequence of circuits before getting sent to a speaker that converts the electrical signal into sound. A typical amp contains all of those components inside a single case. So technically, there is more than just an amp inside an \"amp\"; for example, most amps have at least some equalization, that changes the tone of the instrument, and most guitar amps contain distortion or overdrive circuits, to create that rock guitar sound. The big picture purpose of the amp is to produce performance worthy sound from the (otherwise smaller) signals produced by the instrument. **Head**: While an all-in-one instrument amp is convenient, once you start to get a little high end, or picky in your sound, or just need to be louder, it makes sense to separate the amplifier part from the speaker part. A head is the electrical components of an amp, sold separate from the speaker cabinet(s). I've heard some people also refer to mixers as heads (see next), but I consider that weird. **PA**: Public address systems are an old fashioned, colloquial nickname for a \"sound reinforcement system\". They vary widely in capabilities, but generally a PA system will have a mixer that takes in multiple inputs (e.g. vocal mic, guitar, bass, maybe drum mics if you're in a large room or planning to record), some degree of equalization and effects to change the sound quality (e.g. artificial reverberation or echo), and outputs to power amplifiers (also called heads sometimes) that produce the power needed to drive speakers pointed at the audience. Sometimes there are also similar components for speakers pointed at the band, called monitors, so they can hear themselves better (there's no way a singer can compete with rock band level stage volume, so they need monitors). Across the full spectrum of music and musical equipment, there's a lot of variation, and given that you have a \"ukelele\", you might not be the typical customer. But the above is at least an ELI5 outline. Edit: formatting."
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8271p2 | why motion sensors don't react to sudden light changes and shadows? | Technology | explainlikeimfive | {
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"Motion sensors use a PIR sensor. PIR stands for Passive InfraRed, which is basically a 1- or 2-pixel thermal camera. Since it's only looking at changes in infrared light (which is emitted by mammals and other warm things), it's not going to notice actual visible light changes."
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828lff | How was it discovered that two pieces of the same metal would bond together in a vacuum if they became in contact, and how do astronauts repair stuff in space avoiding this to occur? | Technology | explainlikeimfive | {
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"I'm not sure about the history of it, but I'd wager that it came up as a theoretical prediction long before anyone tried it. As far as the astronaut stuff: vacuum welding is actually tricky to do. The surfaces must fit together very well, like two finely sanded flat surfaces or something. The surface must also be free of any contamination. Many/most of the parts used in space are prepared in an atmosphere, so the oxygen in the atmosphere will bind to the surface of the metal, creating a thin layer of oxidized metal. This stuff won't vacuum weld unless you were to sand and polish it off in a vacuum."
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82a7x9 | Why does an electronic device occasionally glitch? | Computers and electronics by nature should theoretically respond to the same stimuli the same way every time if they're working properly. Why, do electronics sometimes freeze or do strange things but then a moment later or after restarting it will work fine? Something must have been "wrong" during the glitch, but then how do things work again and what was "wrong" to begin with? | Technology | explainlikeimfive | {
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"There are two main causes for electronics \"glitches\". * **Physical Conditions** - things like moisture and heat can and do often effect electronics. Heat especially can cause computers and other electronic devices to fail. Excess heat causes the resistance values of various circuit components to change. Often those components are used for logic processing so small changes in resistance can cause a processor to crash. * **Programmer Error** - much more common are simply mistakes made by programmers. These mistakes usually happen because programmers didn't carefully test their code for strange inputs from the user. For example, on an application might ask the user to enter their birthday. What happens if instead of a date, the user enters a color. Or the word \"cat\" or a bunch of characters that don't make any sense? Good programmers will detect junk input and handle it some how, some programmers aren't careful. In the real world the kinds of input that cause problems usually are much more complex and happen when one application talks to another."
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82a9wo | why locks can be locked without being closed? (link to pic in description or in comments) | When i was 6-7 i had an old, greasy, rusty lock that i really liked for some reason, and i kept fiddling, by locking and unlocking it repeatedly. At some point i noticed that the lock could be locked with the metal thing outside from the hole, not being closed and so becoming useless as a lock, i thought that maybe grease had something to do with it, or time eroded it in some parts. Anyway, i thought it was a particular of that lock, but years later (now) i have a brand new lock i just bought, so it can't be eroded nor broken, so why it can be locked without being closed? (pic related: URL_0 ) | Technology | explainlikeimfive | {
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"Has to do with the design of the internals of the lock. It was just designed in a way where this happens. Probably locks on both sides to make it harder to shim, but I can’t be sure."
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82akaz | What is holding us back from having batteries that charge significantly faster, hold significantly more charge, or even have an unlimited lifespan? | Technology | explainlikeimfive | {
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"text": [
"Unlimited? No. Batteries rely on chemical reactions to hold the energy that's put into them. As the density of stored energy increases, it becomes harder and harder to hold, requiring more and more cleverness.",
"Batteries use chemical reactions to store and then release energy. Those reactions take time and are effected by heat. The faster you move electricity, the more heat the components generate. Heat causes problems with the reaction the built up junk inside the battery which gets in the way of the electron transfer eventually making the battery useless. The alternative to batteries is using capacitors. They store energy by placing electric charge on thin metal plates. They can be charged very very quickly, the problem is they leak electrons away and so they don't stay charged long enough to be used as batteries. Advances are being made to fix that last part.",
"Physics, chemistry, politics, and economics all play a part in the best answer to your question. Batteries depend on chemistry, and power transfer is limited by laws of physics, so there's the science part of an answer. The economic perspective is that better batteries last longer, so consumers won't buy as many or as often. This goes for replaceable batteries as well as more integrated devices with non-removable batteries or batteries that can't easily be replaced. That also ties into politics, since many politicians (at least in the US) receive a lot of money from the fossil fuel industry, and cleaner power like from batteries would screw up that gig."
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82eetx | How does minmax and alpha-beta algorithm manage to find the best possible solution? | In a game implementation like 4 in a row | Technology | explainlikeimfive | {
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"Simply by playing as well as it can against itself for both sides. ***Let's start with minmax:*** A minmax algorithm starts with some move: and then goes \"OK, for every move I make, what would my OPPONENT do in response?\" It then goes to each of those moves and goes \"OK, for every move my OPPONENT makes here, what is MY best response?\" if it hits a leaf (game over or its depth limit is reached) it records who is closer to winning and by how much, and goes back up a step. If it has tested all the moves, then record the best score of the best move for the \"player\" currently being examined and return that. Essentially, it alternates between maximizing the chances it will win, and minimizing the chances it will win(maximizing the opponent). In theory, once it reaches the initial position again, it will have the best move for himself, because he assumed his opponent played perfectly and thus the best move here is the best possible score it can obtain at all. ***Alphabeta pruning*** Now, as you might have noticed minmax tests every possible move down to some specified depth. This isn't very efficient. A single move can have thousands and hundreds of thousands submoves. Alphabeta pruning is the act of observing the best and worst score the move being observed currently can achieve, and if you see a move that clearly is worse for the player in question, stop looking at all and jump back up a step. The logic is that since the move you just discovered is so bad, the player will never play this branch anyhow, he already has a better option that will be returned. By cutting out all the moves not yet observed in this branch you save time. Now you don't have to spend time and energy checking moves you'll never return anyhow."
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82erc9 | Why are IT Best Practices so drastically different per company? | Technology | explainlikeimfive | {
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"text": [
"URL_0 This web comic explains it really well. Not sure how many more words is needed to get around silly bots removing comments."
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82fets | How do radar detectors work and how do police detect radar detectors? | Technology | explainlikeimfive | {
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"> How do radar detectors work They detect the radio waves emitted from some types of radar guns used by police. > and how do police detect radar detectors? Mostly, visual inspection: they see that you have a radar detector mounted somewhere in your vehicle. Radar detectors themselves emit some amount of radiation, so it is possible to use a radar detector detector that can detect that radiation.",
"Radar works as you might expect: emits a radio wave, processes the reflected wave and measures your speed. The wave is 'compressed' (Doppler effect causes a change in frequency) by moving objects, and the degree of frequency change is used to measure relative speed. A radar detector detects that beam and alerts the driver that radar is being used. A radar detector detector is a bit different. It picks up an EM oscillation produced by the radar detector's electrical components. URL_1 URL_0"
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82fivy | Why do lights flicker, and do all of them flicker? | I understand this has to do with alternating current, but I'm still in the dark. I have a set of Christmas lights in my room and I can *almost* visibly see them strobing. Moving objects look choppy. I then noticed if I change the shutter speed on my phone's camera, it actually picks up certain frames of them turning on and off, essentially flickering. Slow motion video also shows them rapidly flickering. I tested this with my bathroom lights, which I believe are incandescent. They also flicker, but at a much, much faster rate as the slow motion didn't show quite the same intensity. This is weird to me as I always assumed lights were just constant, but now I realize that's a bit ridiculous. If they were always "on" they'd for sure blow instantly right? I'm just looking for more information, this interests me for some reason. Anything to do with how and why, the strobe rates of certain types or lights, and if all lights flicker. | Technology | explainlikeimfive | {
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"Your Christmas lights are cheap AC LEDs. Basically they're two strings of diodes that are pointed in opposite directions with no driver or smoothing components which add costs. The voltage coming in looks like a sine wave going up and down. When it rises to a certain point (~30V usually) the diodes will conduct and create light until the voltage falls below the threshold and they turn off, the voltage continues downward until it hits the negative threshold and the other string turns on. This results in 7ms of full light, 2.66 ms of no light, then 7ms of full light again giving you the strobing effect on moving objects The light in your bathroom is unlikely to be an incandescent if you see flicker (unless you have it dimmed) as an incandescent filament heats up and stays hot acting like a low pass filter, this means that even when the voltage is at 0 it is still producing some light."
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82h0j3 | How do scientists seperate particles from the rest of their groupings? | Basically like how do they shoot off one particle at a time in experiments like the "Gold Foil Experiment" | Technology | explainlikeimfive | {
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"Methods differ depending on what kind of particle you want. For example, for the Gold Foil Experiment, they were using an alpha \"particlse\" (which really aren't particles but are actually two protons and two neutrons). Alpha particles are a product of alpha decay, which happens naturally in some heavier elements, such as Radon (which was what Rutherford used).",
"The one used in the gold foil experiment was the alpha particle (two protons and two neutrons together). Radioactive substances found in nature like Uranium or Radium naturally decay and shoot out alpha particles. If you want electrons, you make a voltage between two electrodes in a gas, or shoot light on a photoelectric substance. Some substances emit electrons when heated too. If you want heavier particles such as ions, there are some chemical reactions that produce ions. In each case, you then speed them up by using electric and magnetic fields in certain configurations, and 'shoot' them."
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82hm34 | Why is an electric toothbrush so much better than a manual toothbrush? | Or is it better? My dentist suggested I start using an electric toothbrush and I’ve been thinking a lot about it. But I don’t understand how a vibrating brush is any better than scrubbing my teeth myself. I feel like presence of technology is always better than its absence because tech is awesome but I find it hard to understand why in this case. | Technology | explainlikeimfive | {
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"It's a bit clearer if you look at it from the perspective of WHY you brush your teeth: to break up plaque. The objective is not so much to get PERFECTLY clean as it is to disturb plaque from forming hard masses that help lead to infection and caries. Let's compare it to washing a car to see the difference. Think of how you use a soapy cloth to get your ride ready for a formal event. The car's a mix of smooth areas and detailed areas. The smooth parts like the hood are easy to clean - long, gentle strokes with your soapy cleaning cloth or sponge, and the dirt comes right off. But the hardest parts to get clean are like the grill, where there are seams and crevices... so you fold the cloth or squish down the sponge, and wad bits of it up into points to make it smaller so it can fit in those spots, and then you scrub it back and forth in that area a bit more. The objective is to make your cleaning tool smaller and use shorter cleaning movements so it hits those seams. [EDIT - see *italics* because I missed something - you also move your cloth in more and different directions too.] Well, with toothbrushes, the shape of the brush bristles can help some with the getting-into-smaller-bits part... but most people don't pair that up the little tiny *multi-directional* regional strokes that penetrate in-between the teeth to disturb the plaque there. They just use the same big scrubbing motions that they use on the rest of the \"car\". Electric toothbrushes vibrate or spin, though. And because these actions create smaller brushstrokes *in more different directions* than most people with manual brushes would use, they allow for a better chance to get in between teeth and around the gumline... and disturb that plaque before bad stuff happens.",
"And don't forget the timer. Mine runs for 2 minutes broken into 30 second spans. 30 seconds for lower teeth outside, 30 seconds for lower inside. Repeat with top teeth. It makes you think about getting all your teeth (and gum lines!) brushed. Before I got an electric I doubt that I spent more than a minute brushing my teeth. My dental hygienist could tell I switched....",
"As it turns out, the attribute of an electric toothbrush that is most correlated with good dental hygiene is whether or not the toothbrush has a timer. Because it turns out that, on average, people brush for about 75-90 seconds when they just brush for the amount of time that feels right, and don't evenly distribute that time across the various surfaces -- but a brush that measures out 4x30-second quarters produces a longer, more even amount of brushing. Beyond that, it doesn't make much difference, among people who have sufficient dexterity to brush effectively. There is *some* evidence that the sonic brushes are somewhat effective at disrupting plaque from areas *not directly in contact with the bristles* -- but to get this effect, you need the area between the bristles and the plaque-covered tooth surface to be covered in liquid, and the area in question needs to spend about 5 seconds in proximate contact with the bristles -- and it isn't clear just how often these conditions are encountered outside the laboratory.",
"Dentist here. The main reason is ease of use. An electric toothbrush is easier to use. That is the main reason. Studies have shown the best toothbrush is the one that gets used, and an electric one is easy to use. Now for the long answer. There have been studies done as to how many times you have to shown someone how to brush the teeth in order for them to go it properly on dental hygienist students. (Do obviously people who care about brushing) and it take 5 or 6 times and months to do it correctly with a manual brush. An electric brush only takes once, and they don't even need to be shown. In addition to that you are supposed to brush for 2 full minutes. When using a manual brush you only brush for about 15-30 seconds. If your trying to go for 2 full minutes (like actually thinking about it) you normally only brush for 45 seconds. An electric toothbrush has a timer in the handle so it's really easy to go for 2 minutes. A sonicare for example will automatically turn off after 2 minutes. (That is literally the only reason I use them personally) As far as which of the electric brushes are better, most dentists and hygienists will recommend Oral B, but will personally use sonicare.",
"I did a lot of research on toothbrush friction during university and the three main carry outs were: 1. Do not wet the brush as this softens the filaments which means they buckle under less force, resulting in less contact pressure. 2. Water acts like a lubricant and cleaning requires friction. Just use paste. 3. Do not press too hard as this can also buckle the filaments. Press too hard and buckle the filaments then you are not brushing with the filament tips (maximum contact pressure), instead you are brushing with the sides of the filaments which produces significantly less pressure. Many modern electronic toothbrushes have pressure sensors to stop you pressing too hard. Buy one of these and don’t wet the brush before cleaning. Edited for better English and cleaner teeth.",
"for men, electric toothbrushes are far superior because they allow you to pee standing up while brushing your teeth.",
"Your question has been answered. But I was always skeptical about it until I dated a dental assistant. She got me nice electric tooth brush and I will never go back. My teeth and mouth feel so much more clean and my teeth have whitened up better.",
"The main difference is the speed. Manually I might get 120 strokes/minute if I really go to town but my electric does about 7200. If we assume the manual has about 4 times the working area then the electric is about 15 times as fast as the manual and 2 minutes with it is like brushing for 30 minutes with a manual.",
"I don't know if it's already been said, but as a power toothbrush user (Sonicare Diamond Clean), there's no way you could replicate 20,000+ brush strokes per minute with a manual toothbrush. The difference after brushing manually and then with a Sonicare is amazing. My teeth feel so much cleaner with the power brush.",
"There are two things that make electric bushes better better: 1: They have a timer. Because most people don't brush long enough. 2: They help create lots of small strokes that are better at getting into the cracks between your teeth. Manufacturer claims, that you should take with a grain of salt: Sonicare: Vibration creates a sonic wave that helps to shake the dirt off your teeth. Oral B: Rotation helps sweep the dirt away from your gums."
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82ijgu | [Technology] Why do electronics slow down over time, even though the processes which they run get better? | Take a phone or a laptop for example. 5 years ago, a new laptop could surf the web, use Microsoft programs, and other small games or applications (Solitaire). Over the next 5 years, the processes and applications don't change, but maybe the web (Chrome, Safari) gets more "advanced", more efficient. Why do computers slow down? | Technology | explainlikeimfive | {
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"The processes they run don't get better, they get slower. The people writing that code make their \"is that too slow?\" Decisions using the latest hardware. Every update adds more code but you notice that more if you don't buy new hardware.",
"Because things do change. Every windows update, every temp file, every saved program changes the environment. You're computer doesn't reset back to factory fresh every time you shutdown. In addition, components physically wear out. Hard drives wear out, memory wears out. Heat sinks get dust and fail to dissipate heat causing component reduced performance or physical damage.",
"It's not the electronics slowing down. It's the computer systems. Windows is a good example, it has a registry which keeps track of important information about the system, like where certain important files are and what software has been installed in the past. Over time the registry gets filled and filled with information that Windows has to sort through. Also many modern programs are designed to be \"memory resident\". This means that instead of loading them from the hard drive into working memory every time you use them, they stay in working memory all the time. The problem with that is that there is far less working memory than hard drive space and eventually Windows has to start juggling things in working memory to make it all fit. The longer you've had the computer, the more of these programs you've installed so the larger the registry data is and the more programs will be fighting for working memory. The electrical components, however, are just as fast as when you first bought them, Windows is just asking them to do a whole lot more than they used to.",
"Moore's law. Processing power doubles every 18 months. But, that means that programs can become twice as complex every 18 months and users won't notice... unless they try to run that software on older equipment.",
"Format your hard drive and start over with a new OS installation. It will be just as fast as when you bought it. It will not have the decay and installations that have bogged it down over time."
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82jvmk | How do phones and cell-towers deal with the Doppler effect? | Technology | explainlikeimfive | {
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"It doesn't matter The Radio waves are moving at 3x10^8 m/s, thats 300,000,000 m/s. If you travel towards a cell tower at Mach 10 you'll be moving 3,430 m/s and change the wavelength by 3,430/300,000,000 or 0.0011%. You're not traveling anywhere close to Mach 10 so the impact is truly insignificant",
"? signals from phones are traveling at the speed of light. in order to get a measurable Doppler effect there would have to be a great deal of movement involved between the signal producer and receiver (but there isn't.)",
"More specifically the variation is so small that it doesn’t change the data. Your phone listens for signal coming in and when the wave peaks you get current, registering a 1. There is a certain amount of wiggle room in these circuits before they register the incoming signal as a bit.",
"Light is travelling so fast that planes, trains, and automobiles are barely moving by comparison. The Doppler effect is, as a result, so small it can be ignored. Astronomers, on the other hand, must think about relativistic Doppler (and gravitational redshift) all the time, because stars are moving at much higher relative speeds.",
"Most of the other answers are correct-ish, but for the wrong reason. They're right in that compared to the speed of light, the difference is small. But when we encode information into the beam using Amplitude (AM=Amplitude Modulation) or FM (Frequency Modulation). That's why radio stations are named \"96.1 , FM\"- that's the frequency the station is on. Then we have to ask if a modulated signal can suffer a doppler shift. The answer is not obvious, but it is yes- but the difference is still tiny for radios([~0.01%]( URL_0 ) ) and doesn't matter. Compared to other noise, this is small potatoes. A lot of early radio tech works in the kilohertz. You could see this, but it's a it a poor range. edit: It does matter for some more sensitive technologies- apparently it matters for 4G/LTE: URL_2 The application is complicated, but the basic idea is simple- if you know how fast you're moving your phone (or how fast the emitter is moving), you can mathematically \"undo\" the doppler shift. The trick is finding ways to know/estimate how they're moving. There's a few ways to do it: One way is to have multiple inputs (ie, multiple towers/antenna). You can kind of \"triangulate\" to correct for the drift. Another is to just literally test it, and develop some statistical models If you want more details, I'd recommend /r/askscience or /r/askengineering , because it's a pretty technical question Here's a previous thread on the topic (from /r/askscience) with more details: URL_1"
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82lzal | How did Ancient Greek fountains work? | Technology | explainlikeimfive | {
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"Gravity my friend, the water was taken from an elevation above the fountain, most likely in a water tank. They would use pipes to transfer the water from a tank down to the elevation of the fountain, the pipes were narrow so that the pressure increased in the pipes. Water is then forced through the pipes into the fountain which gives it enough pressure to create a stream and thus you have a fountain. Not sure what they did with the water afterwards, or how they made the pipes / what they were made of. The system is still in use today, and i've even heard theorys that the egyptians used a similar system to hoist the blocks for the pyrimids."
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82nbi9 | Why does an aircraft carrier store all the planes on deck? What happens if they need to scramble jets? | Technology | explainlikeimfive | {
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"The aircraft are “stacked”, or parked in such a way that they can be quickly manned and in the air. None of them would be in the way of launching. If they were all below, in the hanger bay, it would take hours to get them flying. In states of readiness, most of the aircraft on deck are manned with crews, ready to be in the air in five minutes or less. It’s called ‘Ready 5’.",
"Eighty + aircraft is a lot to store even on board a Nimitz Class Aircraft Carrier. Not all planes are stored on deck, usually those that have impending missions or flights coming up. During Flight Ops, a rescue helicopter is launched in case an aircraft goes down. During Fleet Operations, an E-2 is usually orbiting providing the 'eyes' for the fleet. A CAP of fighters is usually orbiting to provide immediate defense for the ship. Several planes are on deck in 'Ready' Status, Ready 5, Ready 15, Ready 30. ASW Airplanes are ready to launch if needed. During highly intense Air Operations, a Nimitz is the busiest airport in the world, with launches and recoveries spaced two minutes apart. The arresting wires are kept clear to recover planes and only one or two of the catapults is loaded with Ready 5 aircraft. There is a small compartment in the island with a maps of the flight deck and models of all of the planes with their status listed. Some of the planes in the hangers are being stored, some are undergoing maintenance. My knowledge is 30 years old but I don't think it's changed much.",
"A lot of people aren't aware of this but the aircraft carriers have two decks, [forward deck blue arrow and angled deck red arrow]( URL_2 ). Although both can be used to launch aircraft, when underway the forward deck is usually a parking lot. Planes can be parked in such a way that the back half of the plane is hanging off the deck. We call it TOW, or tail over water. You can see in this [pic]( URL_1 ). You can also see in the picture above that the forward deck's catapult is open to launch because of the amount of room created by parking the planes TOW. The planes wings also fold up to make them pack easier. It takes only a few minutes to spread the wings and shoot the pins to lock the wings. You can see [here]( URL_0 ), all the planes have their wings folded.",
"Two main reasons: 1. Operational readiness. It's a lot faster to launch an aircraft when it's already waiting on the deck than having to lift it from the internal hangars first. 2. Space. If you keep aircraft both on the deck *and* in internal hangars, you can keep many more on the ship than if you only had them inside. It's worth noting that not all navies do this. Keeping armed and fueled aircraft on the deck has the disadvantage of a risk of fire breaking out and quickly spreading between the parked aircraft. Check out the USS Forestal fire if you want to see how much damage that can cause.",
"Thanks all, I saw a recent picture of the USS Carl Vinson off shore in Vietnam and it looked like all the planes were on deck, however when I searched I saw other pictures that showed the angled runways clear.",
"They store the airplanes on the deck because it makes them easy to scramble. Just hop in and go. There is an entire division on the ship whose job it is to organize and park the planes and they ensure the planes that are most needed next get launched first. But perhaps the biggest misconception is that aircraft carriers “store” aircraft. Aircraft carriers fly aircraft. Just about everyday, many many times per day, all those aircraft are launching and landing. They don’t just sit there. Flight operations are a sight to behold. To start aircraft get manned and move toward the back of the deck, exposing the catapults at the front so launching can begin. Then they launch a wave of aircraft off. All remaining aircraft then move forward to clear the recovery wires where the aircraft hook on to stop when they land. Then there’s a shuffle to the back to clear the catapults again. And then forward to recover. Then back. Forward. And again. And again. And again. Constantly in motion the flight deck is.",
"To get as many aircraft onboard the ship as possible. They store planes on both the hanger bay and the “roof”. When they’re in the hanger bay they’re stored in a manner to make as many fit in as possible. On the flight deck, however, they are stored very methodically very much like parking spaces at a mall. They back them all in with the wingtips almost touching and their tails over the water. When it’s time for take-off, the pilot just pulls out of his parking spot, onto the “street” and taxis (drives) over to 1 of 4 catapults (2 in the “waist” of the ship and 2 in the bow.) The waist catapults perform significantly more of the launches because they are located in the landing area and this location is purposefully kept clear while at sea. As far as how long it takes to scramble jets it depends on the posture of the ship. Depending on where the ship is and what might likely happen, there is a “ready 5” and a “ready 15”. The ready 5 armed, fueled, hooked into the catapult, and fight crew is strapped in. The ready 15 is fuel, armed, and parked near the catapult, while dressed flight crew wait in the squadron’s ready room. If the carrier is in alert status, there are typically 2 planes both: ready 5, and ready 15. This posture is assumed a lot less frequently than you would expect. A deployed carrier with all its escorts is incredibly difficult to surprise.",
"Planes are stored on deck so that you can have more planes. This was actually a design decision that was originally controversial. WW2 era British carriers had all planes stored in hangar and an armor plated deck to protect them. It turned out that the best protection for a carrier (and the planes on it) is planes in the air, so you want to have more of them able to launch more quickly. Later British designs had planes parked on deck as well. On the other hand, American designs also added armor, since light wooden flight decks led to some rather horrific losses (it's not so much the planes you need to protect, but the ammunition and fuel)."
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82o5d5 | Why does the ISS not melt if the thermosphere is 500°C +? | So I read why space is cold and why the earth is not cold. But reading that the Thermosphere is hotter than 500°C made me wonder why the ISS does not melt. | Technology | explainlikeimfive | {
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"The ISS (or anything else in the thermosphere) doesn't have any problem with the temperature because there's basically no air, it's almost a vacuum. Hot gas heats up cold objects predominantly by running into it, and there's so little of it in the thermosphere that an object sitting there gets collided with sufficiently infrequently that it just doesn't heat up to any significant degree.",
"I recently read astronaut Scott Kelly’s book about his year aboard the ISS, *Endurance*. He talks about this issue. The ISS is subject to both great cold and great heat. Heat is the more serious problem and they have a system of cooling tubes outside the ISS. I believe the tubes are filled with a type of ammonia but I don’t have the book handy to check. The Russian section and the American section use different chemicals to maintain the cooling of the outside of the ISS. At one point Kelly takes a spacewalk to inspect and repair some of this cooling system and speaks about it in depth. I highly recommend reading the book to find out more detail beyond ELI5 level. Or better yet, listen to the book, you can borrow from your local library and listen on your phone. Kelly himself reads the book, which adds to its interest."
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82q632 | What’s the difference between .com .net and .org? | What difference does having a .com and .net at the end of a URL make? Furthermore what exactly are domains? I have a very general idea but I would be curious to know more details. | Technology | explainlikeimfive | {
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"When you buy a domain like URL_0 , someone is responsible for that .com portion. That is called a top level domain. Plenty of people resell them, but one company is ultimately responsible as the authority on them. The original TLD's like .com, .net, .org, etc., were originally administered by the US Department of Defence. They had ideas then about who could register what, such as .org being reserved for not-for-profit's. In today's Internet, most of those TLD's are owned by for-profit companies now. Some are still owned by groups that restrict how they're used (such as .edu), or are still owned by governments (.gov, .mil) that don't give them away. Restrictions will vary from TLD to TLD."
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82q88a | What exactly do developers do when they "optimise" an app to reduce stutters/lag? | Technology | explainlikeimfive | {
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"Could be dozens of different things. Most commonly it is things like: * turning off or removing services that are not needed * moving long requests (e.g. \"go retrieve this data from this remote server\") to the background so the UI remains functional * identifying pieces of code that are taking a long time to run and making them faster",
"Remove dependencies that are not being used. Removing code that generally take large amounts of processing power etc."
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82v4jm | How did Disney animate their early animations (e.g. Snow White)? | I know that they hand drew them of course, but without computers, how was this "digitized" and made available to the mass market? Did televisions play it? | Technology | explainlikeimfive | {
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"So, they were hand-drawn, but perhaps not quite in the way you think. Each frame consisted of many different drawings--you'd have a background, then trees or buildings, then characters, and then sometimes actual faces of the characters--something like that. So then to put it all together there was a device that layered all of these different drawings so that if you're looking at them from the top, they all blend together into one frame (and then if your next frame is the same except that someone is talking, you only have to change out whichever layer is changing the person's mouth). When you have it all set, you then take a picture of the total frame setup, and you have your one movie frame. At that point, it's essentially just like any other picture or part of a movie reel, and can be copied the same way,",
"They weren't digitized until long after computers were invented. They were drawn by hand on sheets of thin clear plastic called cells that were stacked and then were recorded onto film frame by frame. That first reel of film is the master copy and it is then dubbed into the various copies that are sent to movie theaters, and eventually to VHS tapes for home distribution once that tech was invented. Once computers became sophisticated enough that was when they were digitized and distributed on DvD and streaming services."
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82xrpi | How come if you leave your car lights on overnight the battery dies, but you could drive for 10 hours straight with lights and everything on and the battery is fine? | Technology | explainlikeimfive | {
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"When the engine is running, it powers an alternator (a kind of electricity generator) which recharges the battery and lights up the lights.",
"There's a device connected to the engine called an alternator. It uses engine power to both provide electrical power to the car and recharge the battery while you're driving."
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82ygte | how multimeters work | Technology | explainlikeimfive | {
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"What part would you like to know more about? Voltage detection is pretty simple and can be accomplished digitally, albeit through a few voltage dividers to get the voltage into a range where the chip can read it. (Likely 0V-battery voltage) Inside the chip, it will compare the incoming voltage with a known voltage from the battery. If the battery is 9 V, and the comparison is 50% of 9 V, then the chip knows that it is 4.5 V. It also knows which voltage dividers it has used so from that it can calculate the actual voltage. (If it was using a 10x divider and measured 4.5 V, then it knows it's actually 45 V.) Current is very similar. To measure current the multimeter passes the current through a very low resistance \"shunt\" (aka a resistor that can handle lots of current.) The multimeter will measure the voltage on both sides of the current shunt, calculate the voltage drop (V=IR) across the resistor, then back calculate the amperage from there (because the resistance is known.) As for the other functions, I'm not entirely sure. :)"
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82z9n1 | How are large planks/sheets of wood made, such as ones used to make doors or walls? Obviously trees aren't big enough to cover that much wide area often, so how is it done? If there a particular process used? | Technology | explainlikeimfive | {
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"There are absolutely trees big enough to make a door from. But generally they're made of multiple pieces joined together so it resembles a solid piece.",
"Rather than slicing a tree trunk into planks, wood for large sheets like plywood are [peeled off the tree]( URL_0 ). You then taken multiple such peelings and glue them together, with [each layer being rotated 90 degrees]( URL_1 ) from the layers above and below it.",
"Most doors are made of particle board or mdf, which is just compressed wood that was shaped in a mold.",
"They're often either carefully chosen narrower planks glued together to look nice or very thin veneer that's cut from around the log (think of a thin slice of wood as being similar to toilet paper coming off a roll)."
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830vwg | Community Networks (Local Service Providers), How do they get started and how do they provide such reasonable rates? | I’ve heard of certain states and cities which have community networks that enable the community to thrive by providing internet at a reasonable rate — with some providing gigabit speeds for as low as $40 a month, in addition to other services such as voip and television. I imagine the stakes that major companies have in most areas has a lot to do with it but in some of these cities these community providers have been able to provide internet even in areas where Comcast, Time Warner, etc. operate. I have a general understanding of network structure and business practices as I work for one of the major providers but haven’t heard much honest information about the smaller providers. Could you explain why more states and cities don’t do this? What steps are required to start a community network? How do they keep the rates low? | Technology | explainlikeimfive | {
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"> why more states and cities don’t do this usually because the Cable/Internet lobbies the government to pass laws prohibiting it, or sues them in court to block any such attempt > How do they keep the rates low? they are usually run as non-profits"
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831oj2 | What is Google Accelerated Mobile Pages (AMP) and why is it important for the futur of the mobile web? | It seems to be the next big thing but it's hard for me to get it. Thanks | Technology | explainlikeimfive | {
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"it strips all the style elements and other heavy stuff so you get a barebones site that loads faster. whether it's important for the future of the mobile web is debatable since it breaks a lot of stuff including text formatting, but it also saves a lot of data if you dont have unlimited"
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832s0h | Meltdown/spectre thing with cpus | Technology | explainlikeimfive | {
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"There is a bug in the CPU hardware. Using this bug, malware running on your computer can access memory for other programs that it should not be able to access. There are patches, but they have side effects. Your next processor chip probably won't have these bugs, but it might have other bugs.",
"First some background: The further out that you have to go away from the CPU to access data, the longer it takes. So to make a CPU as efficient as possible you want to reduce the amount of time it spends accessing data far away from it. The fastest memory is the cache built into the CPU itself. System RAM is slower than that. While a hard drive works at the speed of erosion by comparison. Since the 90's CPUs have used a technology called speculative execution that basically takes an educated guess as to what your program will need next and pre-loads it. It's not always accurate, but its hit rate is accurate enough to give a significant performance boost. The Spectre/Meltdown flaw is a result of how CPU speculation is implemented. Basically a hacker can write a program to trick the CPU into loading sensitive data into cache via the speculation mechanism and then read it. Allowing the hacker to access information that is normally protected from his view, like a password stored in the memory of another application. \"A bartender takes a guess you will walk into a bar, you don't. He bills your credit card anyway.\" So how do you fix this? The next generation of CPU's will have different architecture that doesn't have this type of vulnerability. But in the meanwhile the Windows and Linux Kernels are being patched to include new software that looks for and detects these kind of memory look ups and stops them. The catch being that this has a significant performance impact."
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8344rz | How do free games (like Fortnite) make profit? Especially for a 3D game which employs alot of artists, developers, etc. how do they pay all of these people and still earn enough money to keep the company moving forward? | Technology | explainlikeimfive | {
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"Microtransactions. They offer a bunch of stuff in game that you can buy. A lot of mobile games get ad revenue as well, but it's mostly in game purchases.",
"Microtransactions and ads. Most of the great free to play games are based off of cosmetics and loot boxes (The thing everyone is currently bitching about) and ad revenue. There's quite a few people lobbying to get rid of loot boxes. Which will effectively do away with good free to play games. (I understand for full price games why it's dumb) micro transactions can be done tastefully out horribly. It's sad when you say the word micro transactions people cringe, but they've paved the way for some great games."
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8358nb | how does that switch on my rearview mirror that helps dim headlights at night work? | Technology | explainlikeimfive | {
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"There's two types. The old style is positional; the new style is electronic. The positional ones came first and have been around for decades. These type of car mirrors are actually two main parts - a true reflective \"mirror\" and a plain piece of transparent glass, mounted at a different angle, that's just in front of it. It relies on how transparent glass still reflects some light, and you can see this when looking up from the base of a skyscraper to see the reflection of the sky's clouds in all of its windows. During the day, the mirror's in the \"NORMAL\" position, and you're seeing the reflection of things behind you by looking at the mirror through the glass. It reflects almost all of the light, so you see pretty much 100% of the light that gets to it, which is great during the day. However, at night, you don't want 100% of that light because of the glare that comes with it... so you flip the tab to the \"NIGHT\" position. This moves the mirror out of alignment with your eyes, but {edit for accuracy} moves the different-angled transparent glass into it so it - and the partial reflection it gives you - stays lined up with your eyes. So the mirror's true reflection points elsewhere now and you only get a fraction of the light that bounces off that different-angled transparent window... and that lower volume of light is much easier to see with now. The electronic version replaces it with an actual dimming process. The switch in this case causes an electric current to pass through a very thin special film on the mirror that causes it to darken. Think of it like one of those cheap solar-powered calculators where the number 8 has seven segments. To get the number 1, electric power flows to the two rightmost segment, turning them black; the other five are \"off\" and thus transparent. In the mirror, applying current to the film just turns the whole surface slightly gray and stops some fraction of the light from being reflected, not turning it outright black but still blocking a lot of the glare.",
"Now I just wish they would invent auto dimming side mirrors :( stop those dam Toyota Corrolas from blinding me",
"Prismatic Wedge! It's a piece of mostly reflective glass and another mirror behind it. When you flip the tab it angles the back mirror up to reflect the extra light away from your eyes. URL_0",
"Mirror has 2 layers. part of the light reflects off the top layer, the rest off the 2nd layer. flip the switch and the back layer reflects a bright part of the light upwards, while the front layer stays and reflects a dim reflection in your eyes. [Picture is worth a thousand words]( URL_0 )",
"There are 2 types: prism and electric. The prism mirrors work by reflecting either off a mirror (in the daytime position) or a piece of glass at a different angle (night time). The electric can work in a number of ways. The one I am most familiar is the \"electrochromic fluid\". It's actually 2 pieces of glass with a very thin layer of liquid between the 2 layers of glass. The liquid is held in by epoxy of some kind. There is an electric current that causes the liquid to darken. This is usually automatic based on light sensors picking up the light of the headlights from the car behind you and comparing it to the ambient light. Gentex Corporation makes a version of these that also features a Homelink module to open garage doors and turn on lights and whatnot since the mirror is already wired."
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835onc | How can concert tickets and big clothing drops seemingly be already sold out at the exact same second they go live? | For context: Was just attempting to get Anderson .Paak tickets from TicketMaster however their site was already displaying that they were sold out at the exact same second they went live. | Technology | explainlikeimfive | {
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"Either someone had access to buy before that, or a lot of buyers were just faster than you. There's many examples of employees buying the entire stock before the sale goes live. And there's also many examples of people making software to buy tickets as fast as possible (seconds) as soon as sales opens, leaving little chance to people who buy manually.",
"Places like stubhub and vivid seats have bots that buy up the tickets within an split second. Im sure here are more companies that do this but those two come to mind. The answer is bots. CAPTCHA? joke. Its easy af to pay some Indian to enter the codes at lightning speed when they popup at his desk. It will screen shot it, send it to him and he puts his answer in the box it moves it to the seller. Sadly this is all perfectly legal and wont change.",
"People have systems in place to buy them all up for profit. Maybe they have a dozen browser windows open, maybe they straight up have bots, it doesn't matter - if there's a financial incentive to buy up a thing and resell it, people will."
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837muy | how 3D movies with polarized lenses are seen in 3D with both images (the one for the left eye and the one for the right eye) are on the screen at the same time | Sorry if it’s hard to understand, but my first language is not English. When you see a 3D movie using the polarized glasses technology, the image for the left eye and the one for the right eye are both on the same screen at the same time (unlike VR headsets that have two screen, one for each eye), but each eye only sees one image instead of the two superimposed images. Also, each eye doesn’t only see one of the two at random, it is intended to see. How does it work? | Technology | explainlikeimfive | {
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"A way to picture what polarizers do is imagine that kids toy which has a square hole and a round hole. Only the square blocks fit through the square hole, and only the round fit through the round. A polarizer has this effect on light. Light can be polarized in different ways (different 'shapes') and then you can make glasses that have polarizers on them (different shaped 'holes'). Your left glass lens will only receive light polarized in a triangular shape, and the right glass lens will only receive light polarized in a circular shape, and the projector has the same filters over its output for the left eye and output for the right eye. Seen without the glasses, your eyes can receive all shapes of light so you see both of them together, put the glasses on and the proper filtering occurs."
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8380z8 | How is old packaging recreated for TV shows and movies? | I'm thinking of shows set say in the 1970's or 1980's but made in 21st century where you see things like drinks cans with removable ring pulls or even pierce-top drink cans. This sort of stuff is easily mass produced, but 30 years later as a one-off? How is it done? Some examples: [Screencaps of food and drink packaging from 'Stranger Things']( URL_0 ) | Technology | explainlikeimfive | {
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"A film or show's property department is responsible for all that stuff. They'll be given a budget to work with and part of their job is figuring out if purchasing an original item is more cost effective then a recreation. For example the walkman's used for Guardian's of the Galaxy 2 were custom made since the first film made the original walkman popular (and more expensive) on ebay. URL_1 A prop's importance to the story also plays a part in how much attention to detail it needs. If its something buried in the background a modern item that looks close enough might work. The walkman from Guardian's works for this as well. The prop had a lot of importance to story so several were recreated by that film's prop team. This is also a good read: URL_0 TLDR; Through a mix of shopping and creating",
"Here is an episode from the wonderful design podcast 99% Invisible that talks specifically about graphic design of products, props, and background for TVs & Movies, including an interview with a graphic designer for the props department. URL_0",
"There are other amusing instances of props being taken and used because they 'look' futuristic or complex to the unknowing viewer. I have worked in audio production for decades. There are countless times I have seen some rack of gear in a futuristic program, but using gear that I work with every day. Because it looks unusual and has lots of flashing lights and weird colors or dials. Chief among these are mastering equalizers, FFT analysis tools, professional pre amps and tons more. A lot of audio gear also appears in medical shows where they figure it doesn't matter or perhaps don't have the budget to get the actual medical gear they are supposedly using. It gets a laugh from me when I see someone adjusting an equalizer dial and a moment later someone else slams the paddles on a heart attack patient or some similar event.",
"On larger budget sets, there is a graphic design team that works within the Art Department (props & set) that remake or recreate a lot of older packaging. Because of various branding and copyright legalities, they can often get away with flipping a couple letters around, inversing colors, or simply asking the company for the rights to reprint stuff for motion picture use (not for sale). As for the physical quirks, like drink cans with removable rings, the props department can do two things: purchase period authentic cans or build their own, like relabeling a soup can. Obviously, buying them is WAY more expensive than building one, so the more authentic ones would be used in close-ups, while the fake ones would be used as set dressings (background props). They are also numerous companies that recreate and mass produce period (time period authentic) props and dressing specifically for films."
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83a6ji | How is putting files in the recycle bin any different from a regular folder? | Technology | explainlikeimfive | {
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"It isn't. The recycle bin is just another folder. The operating system is going to associate meta data to that folder through some mechanic that when you \"empty the trash\", it implies this folder has its contents deleted. That's it. Nothing special. And your user interface has shortcuts, like if you hit Shift + Del, typically the file is deleted without going to the recycle bin. No computer is going to automagically delete the contents of the recycle bin unless you explicitly configure it to do so. This might be done by a network admin on a company or school computer, but this is not the behavior of a personal PC. If you're running out of disk space, the UI may suggest you empty it. On Unix type systems there is a /tmp directory that is temporary, and you can't be sure that anything you put there will stay there. Again, the filesystem doesn't give a shit, it's just another folder, there has to be some higher level program that looks to it specifically and a standard protocol that dictates convention. Typically on a Unix system, the tmp folder can be scheduled to be purged if the disk is running full, or the directory starts reaching a certain size, or it may get purged at shutdown or startup. The kind of data that goes here should typically be cached data where if it were gone, the data could be obtained another way, the /tmp data would just be an optimization. Other things that go in there are lock files, whose presence means some other file is in use, or some process is running. If the filesystem supports locking open files, then the program can open the file and forbid the drive from being unmounted or the file being read or written to by any other program. You can clear this folder and those open files would remain since they're still in use. Not all of this is a best practice anymore because some of what I mentioned has inherent flaws and new features of operating systems can make some of that old fashioned."
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83aa8r | Why is it that in web browsers the address will often have %20 between every word? | Technology | explainlikeimfive | {
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"%20 is the code for a space character. You're not allowed to have spaces in a URL, because otherwise including a url in a sentence like URL_1 upon a time would be really confusing. But if someone puts a file containing spaces on a web server, and you want to access that file, there needs to be a way. So the way you do that is that you put %20 in the url instead of a space. The web server translates the %20 to a space and then looks for a file with that name. Why 20 and not some other number? Every character a computer understands has a numerical code, from the ASCII or unicode standard. You can look up the code for any character and \"escape\" it the same way. For example, try typing r% URL_0 into your web browser's address bar, it will still take you to reddit because %65 codes for 'e'.",
"In the HTTP request, it expects the file to be a single word without spaces. If you have spaces, you have to replace them with a way to represent them. Browsers do this by using % escaped characters. If you do %XX, where XX is a hexadecimal number (characters 0-9 and a-f), you will get the ASCII character of that hex number. In the case of space, it is at character 32, or hex number 20."
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83cysc | How is linear algebra used in machine learning algorithms? | Edit: the two well thought out and informative answers I've gotten so far are making me very glad that I chose electrical engineering instead of computer engineering for a major | Technology | explainlikeimfive | {
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"We use matrices to represent data and relationships between data. We do all kinds of matrix stuff; we multiply them, add them, find covariance, find eigenvectors etc. Multiplying two matrices with say 1000 entries each helps *relate* 2000 units of data in just one operation, multiplication. Matrices make organization in ML easy. Operations just work if you know the algorithm. For a Machine Learning student, matrices are just a way to list stuff basically, but if you can understand the mathematical implication behind matrices and how they affect space, aka Linear Transformations, and other Linear Algebra intuitions, like what exactly are you doing to your data units when you find their eigenvectors, it can help you understand your ML algos better. Other than this, ML tools have highly optimised algos for matrices and if you were to use normal non matrix operations, it'll be much slower. These are the main reasons I think Linear Algebra is used in ML.",
"Many machine learning algorithms, like neural nets, can be represented by what is known in computer science as a [graph]( URL_0 ). A graph is a series of connected nodes, and each connection is assigned a weight, representing some sort of cost or effort associated with moving between those nodes. Internally, a graph with N nodes can be represented as an N x N matrix. Each row and column represents a node, and the values in the matrix show whether the nodes are connected and what the weight of the connection is. If M is that matrix, if node 1 and node 5 are connected with a weight of 20, then M[1,5] = 20. Representing a graph in this way means that performing operations on that graph is equivalent to matrix arithmetic. Computers are very good an linear algebra, and there are many very efficient, time test algorithms you can use to peform these sorts of calcuations quickly."
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83d5o9 | Why do non-rechargable/single use batteries last longer than rechargable ones? | I recently bought a pack of rechargable AA batteries and promptly returned them when I read they had to be replaced and recharged every couple of hours in like a TV remote. Why do non-rechargable batteries last for months? | Technology | explainlikeimfive | {
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"They don't need to be recharged every couple of hours. They need to be recharged after a couple of hours of **use**. In this instance, that would mean pushing a button on your TV remote and holding it down for a couple of hours straight, but you don't do that. You push a button for a small fraction of a second each time you use it. That kind of use translates in to months of life regardless of what type of battery you're using. Rechargeable batteries don't last as long as standard ones, but the difference is not that dramatic, especially in a low-draw application like a TV remote.",
"You had something not quite right. Yes rechargable batteries don't have the same energy density as alkaline batteries, but the should last many months, and alkaline should last years. The chemistries are vastly different, the designs are different. It's a side effect of designing the battery so that you can put electrons back in (and many times at that). They also self discharge more than alkaline. You can leave an alkaline cell on a shelf for 5 years with no use and expect it to work. If you put a charged ni-mh on a shelf for 5 years, it'll not only be dead, you might not even be able to charge it without special conditioning."
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83fktx | Are driverless cars at the point where, faced with a crisis, they can choose to hit a tree instead of a child? | Technology | explainlikeimfive | {
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"No, the self driving cars of today can't make \"lesser of two evils\" decisions. But lets approach this philosophically for a second. What you're describing is a version of the trolley problem where the subject (the car in this case) is required to make moral decisions about which person(s) to kill. In this case, the decision is between the passenger(s) of the car and a child who runs into the road. I would argue that even when cars can determine that it is a living human child that has run into the road, that the car should not endanger the passengers. Obviously the car should apply breaks as soon and as hard as possible, but swerving should only be an action to avert collision entirely and never to decide which thing to hit. This stance rests on a few points: 1. If there's a protocol in the self driving car that prompts it to kill or endanger the passengers, then it can be tricked into killing the passengers. 2. I won't buy a car that might decide to hurt me for some reason. 3. If cars and the software engineers behind them make those decisions, they become liable for those decisions, opening a legal and moral can of worms that nobody wants to touch. Imagine if the car swerves, killing the passenger and 10 old people in order to miss 3 children. Who decides that my life and those of 10 old people is greater than the children? Are 3 children even worth 11 adults? The answer to that question depends on who you ask. It's far better to not force the car to make that decision at all because... 4. Above all else, cars on the road need to be **predictable**. That's the whole point here. The goal of the self-driving car is not perfection. The goal is a highly predictable and safer-than-human driver.",
"These situations don't arise often enough in real life to even consider them. Self driving cars will be so much safer than humans that they will likely never have to make that decision. Must accidents happen due to not paying attention to the road, using excessive speed, not following the rules, or bring in a rush. A self driving car will have none of these problems.",
"No. To date driver-less cars are (like all computers) not aware of the ethical implications of their actions. They will simply do what they are told either explicitly e.g. \"if in a crisis, save the child\" or implicitly e.g. \"minimize the amount of people injured\". Whether it is technically possible to reliably get all the information necessary to make such a decision (there might be a baby in the back seat and crashing into the tree will kill it) I don't know. Nevertheless, the choice of behavior is, at least for now, in the hands of the person configuring the car. Now, is a person at the point where, faced with a crisis, they can choose to hit a tree instead of a child? I don't know. My take on it is that if we were, there would not be so much disagreement on how a car should behave in this situation."
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83fz4p | When a music album is “remastered” how is it done? | Technology | explainlikeimfive | {
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"Mastering is a form of mixing that tends to be very very subtle. During my last month in my recording arts program we handled mastering sessions and songs. This consisted of sitting in a room that had been treated to remove as much room tone as possible (lots of foam and acoustic treatments on the walls to remove unwanted reverb or undesirable artifacts that you would hear and obscure the changes being made). We worked with speakers that were as tall as I was over 6' and that had more individual drivers in them to more accurately replicate the audio files. Fun fact they also cost 90k+ per speaker group. We used high end equalizers and compressors along with very intense spectrum analyzing software that would actually allow us to see where odd noises were occurring and be able to reliably edit them out. the changes we made were minute sometimes as little as .3dB of change to a very narrow band of frequencies. We would also add gain to the frequencies that are above the range of human hearing (over 20khz) this can be a placebo effect but can also help bring airiness to music and give it a more open feel. More often when an old album is remastered the main things they will do is make the audio seem louder. They do this by compressing the overall track which will bring the quieter sounds up and giving the illusion of an overall gain increase to the music. They might also decrease the noise that inherently happened on oldshcool analog recordings hiss pops etc. Finally they can do some of the processes that I discussed earlier to clean up the sound and maybe help bring the track back into line with the original intent or desire of the recording artist and producers. Hope this help!",
"They re-edit the tracks to modern day standard of mastering. Which is much louder than a few decades ago. I'd also suggest you learn about the loudness wars, that is destroying the quality in modern music as we know.",
"Lets say a song has drums, bass guitar, rhythm guitar, lead guitar, a synthesizer, and a singer. It can be difficult to mix those instruments together in such a way that each instrument blends into the mix, but is also clearly heard. For example the bass guitar and drums occupy some of the same frequencies of sound, so a bass drum hit at the same time as the bass guitar hit, masks both sounds. When you mix a track one of the things you're doing is trying to manage how saturated each frequency range is. You do this by using high and low pass filters, EQ, and compression. Using the drum/bass example, you could apply a filter to the bass so it doesn't go quite as low, and another to the kick drum so it doesn't go quite as high in pitch. This gives both sounds some breathing room so they aren't playing over each other. But maybe when remastering the song, they want the bass guitar to reach lower, and the drum sound not to be as bass driven. These decisions are some of the things to consider when mixing a track. You could also apply dynamic compression, which makes soft sounds louder, and loud sounds softer, in order to bring an instrument out in the mix, or blend it into the background more. Each instrument will also have it's own dedicated track, or recording of just that instrument by itself and it's possible to add effects like reverb, or chorus, to just that instrument without affecting any of the others. There are also many more recordings and instrument parts that were originally recorded, but didn't make it to the final song. Sometimes these are added back in when it's re-mixed to give it a slightly different tone. This process of taking a bunch of raw recordings, mixing them, applying effects, and mastering a song, is the job of recording engineers and the producer. Back in the 70's and 80's music often had more variety in how loud or soft different parts of a song were. Many of the songs were mastered for record in order to sound their best on that medium as it was a popular format. When CD's came along they had different requirements for a 'good mix' and so an album might be re-mixed or re-mastered for digital in order to make it sound it's best on that medium. In addition to that, our tastes as music lovers have changed, and people tend to associate louder sounds, with being 'better'. There is a limit to how loud a sound in a recording can be though, so they use tricks like dynamic compression in order to squeeze more sound into the limited space of the track. The result is newer albums tend to be much louder than older ones. Sometimes when an old album is re-mastered, they increase the compression and make the whole song louder. This makes it jump out of the stereo better and makes it 'pop' but it also limits dynamic range, and so the songs tend to be very loud for most of the song, rather than having quieter parts and louder parts. Some people don't like this and there has been push back against that technique. Google \"loudness wars\" for more info. Vinyl is also having a Renaissance right now and because it has different mixing requirements to get the most out it, there are often several versions of a song or album for Cd, Vinyl, or Digital. I've been an independent musician and have a small home studio for a few decades and mixing and mastering music is very difficult but rewarding. A good example of re-mastering is the song \"Kites\" by the band Geographer. [The version of it on the Myth album]( URL_3 ) is very different than [the one on Animal Shapes]( URL_1 ) Especially the drums and synth. The Arcade Fire song \"No Cars Go\" is another one that was much rougher in an [earlier album]( URL_2 ), versus the [polished version in a later album]( URL_0 ). Granted, No Cars Go sounds like it was re-recorded for the 2nd attempt."
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83gekk | How does Topgolf scoring/ball tracking work? | Technology | explainlikeimfive | {
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"The scoring is RFID based. Topgolf balls are specially made with an embedded RFID chip. When the ball lands in a scoring zone, it passes an RFID reader which identifies the ball associated with a player."
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83h5zg | What's the difference between Megabits and Megabytes? | Technology | explainlikeimfive | {
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"One megabyte is equal to eight megabits. Megabits per second (mbps) are generally used to describe the speed of an Internet connection, whereas megabytes (MB) usually refer to the size of a file or storage space.",
"Bit is short for \"binary digit\" which is basically anything that can only be in one of two states. Like yes or no, off or on, 0 or 1. Eight bits is called a byte. 'Mega' is the metric prefix for one million. So megabits means one million bits. And megabytes is one million bytes. & nbsp; Files are usually made up of millions or billions of bytes. Network speeds tell you how many bits can be transferred per second."
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83hz9j | Why are CCTV cameras preferred in building surveilance to normal cameras despite the latter's seemingly better picture quality? | Technology | explainlikeimfive | {
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"> Why are CCTV cameras preferred in building surveilance to normal cameras despite the latter's seemingly better picture quality? A \"CCTV\" system refers to \"Closed Circuit Television\", meaning the video output from the cameras are fed into a \"closed\" network which isn't publicly distributed. The television part refers to the idea that they capture a video stream rather than the single images recorded by a regular camera. Video is superior in that it can capture ongoing actions without missing periods of time; consider how useless a camera that captures an image every second would be in trying to record a shoplifter. One picture they have an item in their hand and the next they don't; what happened to that item? It doesn't matter how clear the photographs are they don't answer that question.",
"I believe it all comes down to memory storage. Modern high res cameras (unsurprisingly) record great quality videos but they require huge amounts of space. A video of several minutes can be upwards of 1GB depending on quality. Multiply this for 24hour days, 7 days a week and a business are looking at Google-/Facebook-sized storage. Lower res CCTV makes this more manageable.",
"Storage space. Cctvs are just regular cameras with lower quality/resolution. A 1080 camera with good quality is a few gigs per hour, less if the processing unit has a good cpu and can so real time compression. Multiply that by 24 hours a day 7 days a week and your storage space requirement becomes unreasonable quickly."
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83k2ox | What's so special about TV studio lenses? | I work with a variety of camera and lenses in the corporate and TV series world including anamorphic, PL, EF, C mount, etc, etc. Why are TV studio lenses so large and box-like? I can't imagine that's stabilization motors considering they're always on posts. | Technology | explainlikeimfive | {
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"The lenses are round. However, they typically have a rectangular shade to keep the studio lights from entering and causing reflections; and they often sport motorized zoom and/or focus controls. If this doesn't explain the type you're thinking of, maybe provide a link or two to some pictures or items?"
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83qrq3 | Electric vehicle charging units compared to gallons of gasoline. | Technology | explainlikeimfive | {
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"33.4 kWh of electricity is about the same energy as 1 gallon of gasoline. [source]( URL_0 )"
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83rzly | Why and how are atomic fountain clocks the most accurate time keepers? | Technology | explainlikeimfive | {
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"Atoms are very small and extremely stable oscillators. The atoms we use for clocks, mostly cesium, can be kept in a little ball in a vacuum by cooling them with lasers. Alas, in the little ball the signal from each atom gets combined with the others in a non-synchronized way. This makes the signal muddy and not as accurate. To improve accuracy, only a few atoms are tossed up from the ball, like the way a fountain tosses a little bit of its water up into the air, hence the name. When the atoms are floating around as individuals, they can be excited and their vibration measured to enormous accuracy. They fall back into the ball, and so the fountain has to knock new ones up to look at all the time. If we could get individual atoms to hang around, that would be even better, but atoms have mass so that's a problem here on Earth. Without the laser stuff they all just settle to the bottom of the vacuum chamber; sad. [This great article on the NIST site]( URL_0 ) has some great youtube videos on how the thing works, with animations and all."
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83spgl | How come—when looking at the light produced on earth VIA satellite imagery, they are always yellow, when in fact, there are lights of all different colors being produced? | Technology | explainlikeimfive | {
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"It's not VIA, it's just via, a word. :-) Anyhow, the answer is simple: most electric lights are actually yellow, so when you look at a lot of lights grouped together from far away, you see mostly yellow light."
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83xb9a | How a cellular network handles IP addresses? Does it just act like a massive router? What is different between internet use via router or via LTE? | Technology | explainlikeimfive | {
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"The whole point of TCP/IP is that *it doesn't care what you run it over*. Wifi, Ethernet, LTE, DSL, Cable, ATM, etc... You just encapsulate IP to run over that network and connect it to a router one way or another. That router is connected to other routers over some *other* physical network but, as long as they both have the same network & speak TCP/IP, packets get routed.",
"Phone talk to the tower they are connected to in frames, that is that take some data, wraps it with a header describing where it's coming from (your phone) and where it's going (the tower), plus information about it's contents. Each frame is then encoded and transmitted via the network. One of the things frames do is tell you what type of data is in it, so it could be a phone audio link, or it could be an internet connection. The frame header will include what type of data it is. The tower will pick out types that needs to be sent elsewhere and send them along, this could be just a different type of frame, saying what kind of internet data is in the packet (like multiple packets, or fractions of packets). Those bits meant for the internet are then sent to a gateway which just reads the internet frames and converts them into actual packets on the internet. That is then connected to a router and firewall which lets the phone access specific applications not on the open internet and lets then do stuff like run NAT (share external IPs between phones). That was the ELI5 overview, and applies to most networks, more details are available [here]( URL_0 ) but it's not ELI5 material unfortunately."
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83xkzr | How do we make water safe to drink? (Including removing the chemicals used make the water "clean") | Technology | explainlikeimfive | {
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"Several ways: Desalination: turn water into steam. Salt and dirt doesn't become steam. Steam is clean. Turn steam back into water. Water is clean and not salty. Reverse osmosis: force water through a tiny screen. Dirt and germs are too big and stay behind. Distillation: pretty much the same as desalination except you start with not-salty water. Minor differences that a 5 year old won't grasp. Filtration: similar to reverse osmosis except use a can of charcoal and other stuff instead of a tiny screen. Minor differences that a 5 year old won't grasp. Chemical treatment: kill the bad stuff by adding bad-stuff poison. Boiling: kill the bad stuff by cooking it.",
"You make water safe to drink by **adding** water cleaning chemicals, mostly clorine-rich ones, though you can use iodine in a pinch."
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83zmx6 | How come upcoming sony phones have 1080p 960fps recording when even high-end dlsr can't do 120fps? | Technology | explainlikeimfive | {
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"DSLR cameras are typically pushed for still photography, adding the feature would cost more time & money while not necessarily getting people to run out and get the DSLR. Meanwhile on a cell phone the more 'fun' bells and whistles like that DO influence decisions to buy. DSLRs are also pushed towards more serious and more high-end camera buyers, and as someone who's worked in that industry... they prefer 'dedicated' gadgets, not multitaskers like mobile phones. If they want to really do a project with high FPS, they're going to go get a movie camera designed specifically (and solely) for shooting moving video."
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841pww | Why do movies look smooth at 24 fps but video games look choppy under 60 fps? | Technology | explainlikeimfive | {
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"A computer frame is a rendering of an exact point in time. A camera frame is a capture of everything over a short period of time (e.g. 1/24th of a second). Lets say a baseball pitcher throws a ball to a catcher. A computer will render the ball as it leaves the pitchers hand, every new frame the ball will appear to \"leap\" a few feet closer to the catcher leading to a choppy video. A camera will instead capture a white blur a few feet long, and the next frame the blur will be a few feet closer to the catcher. You won't be able to see much detail on the ball but it's motion will appear smoother. Poor MS paint drawing of what I'm talking about: URL_0",
"This is subjective at best. I've never understood the movie world's obsession with sticking to 24FPS. In modern action films, fast action scenes look awful at 24FPS it's just not fast enough to capture it properly in my humble opinion.",
"It's mostly down to motion blur. In video games, by default, you see everything in its exact right position at the frame. In a single frame of a film, if something was moving, it's blurred. With a high enough FPS, you don't need motion blur; your eyes do that for you. I've heard rumors that some game developers have tried adding motion blur to their games."
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844rzv | Why do many workplace PCs still run on old software? | Technology | explainlikeimfive | {
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"A few reasons: 1. Cost. Upgrading software is expensive. If an upgraded licence costs $50 that may not seem like much, but doing that for 5,000 machines gets really expensive really quickly. 2. Compatibility. Very often, companies will have custom or specialized software that may not function well with newer software. If the older software doesn't have patches/upgrades, or those patches/upgrades are not cost effective (see point 1) you may need to keep other software downgraded in order to preserve compatibility. 3. Security/Reliabilty. Older software - particularly in the enterprise - can be more secure and/or stable because the bugs and security holes have been patched. Newer software may introduce newer bugs that can compromise operations. 4. Usability. Not everyone is computer literate in a company and upgrading their software may confuse them to the point where they struggle to do their job until they learn the new software.",
"Usually it boils down to the cost. The cost of upgrading canned software like MS Office, SQL, or Exchange can be astronomical. Even $150 x 500 machines gets very expensive very quickly, and that doesn't include the labor. Companies also often have highly customized software like ERP systems or applications built in house that aren't compatible with newer OS's and they aren't willing to spent the time, effort and money to upgrade it. The government in particular are notorious for this. They often don't have the resources to perform an upgrade because they either contracted out the software development in the first place and that company is out of business. Or the people that worked on it quit / were laid off / retired / don't have the prerequisite skill set. So more often than not they sit on the problem until it becomes insurmountable and only then do they make an effort to upgrade. All too often companies are willing to make an upfront investment to develop a system to suit their needs without any real understanding of what will be involved in maintaining it moving forward. Next thing you know they lay off all the developers to save costs... The application is working after all, why do we still need devs? The reality is the cost of IT upgrades don't go away because you ignore them, they accumulate. So more often than not it costs more to upgrade long after the fact then having just done it in the first place.",
"I think you got many better answers then i have, but for me ITs two points: 1) If it does what is suppose to do, why change it? 2) It would cost a lot of money to get it working on newer system but it would still do exactly the same thing.",
"*“Why should we waste money on something that is working fine?”* - Boss",
"In our company locker room, the conveyor belt that dispenses uniforms still runs on Windows 95.",
"Don’t forget compliance, aerospace industries use old software as changing the software means you have changed how you build the item and you may need to get that item re-certified. Until you get the item certified you can’t sell that item.",
"Windows 10 was not free for companies so money. Money is Why. And they have update all the software they use.",
"It's not just the cost of the software as most people are mentioning. In science we use SUPER old computers to work with SUPER old equipment. We have lots of software that won't even run on windows 7. Upgrading to new computers would not only cost us the cost of new computers, but new, multi-tens of thousands of dollar machines as well. Also, integrated serial ports work a HELL of a lot better than the USB - > serial converters. Hell, we still have machines that require the computer to have a GPIB card. (And they still work well so why would we want to replace them.) You get really good at pirating old versions of windows when you're in science. (Go ahead, you go try to buy XP without it being super overpriced.)",
"A lot of times IT departments are wary of upgrading because it might break old software they're using. If you update your operating system you run the risk of breaking any software that hasn't been updated for the new OS yet (or is no longer maintained and won't be updated at all). Even updating individual pieces of software may cause workflow disruptions if something no longer works the way it's supposed to.",
"A huge one is that a business runs on a wide range of software. I had an issue where I had to revert an uprade to W7x64 because a piece of software that was very much needed only existed as a 16 bit app. It was utterly horrifying, but hey.",
"So a point many of the commentators are missing, is unions. Changing software is considered a tool change and as such must be negotiated and as anybody who deals with organized labor knows, it's something you don't want to do unless you have to. People forget with any \"tool change\" often come deals like \"you have to train our people\" and \"you can't doc anybodies performance for the next X years because it's not their fault they missed the deadline, you changed the tool\". For example when we moved from Office 2010 to Office 2013 we had to agree that no union member would be penalized for not meeting any deadline that involves writing anything for one full year after proof we provided them a four hour formal block of instruction on Office 2013 first and unsurprising we still have people years later than haven't met a deadline since. Because you know the upgrade in Office versions was such a massive change that one could no longer write work orders on time. People simply forget lots of organizations simply don't change because organized labor negates any improvement you could possible realize by ~~my~~ making that change."
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844z4g | Dear DJs! I am really curious about what you guys doing on that "table", sometime you "use" them a lot like making some sound effects, sometimes they just let it be and music still come out as usual. Sorry for my English. | Technology | explainlikeimfive | {
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"Let's imagine a simple DJ setup: there are two turntables and in between them there's a mixer. The DJ can play a different song on each of the turntables, and uses the mixer to 'mix' them together. He can select from 0-100 how much of each turntable you hear. Mixers often have options like altering low, mid and high frequencies per turntable. These are the knobs you often see them playing with. Hear a song playing without bass all of a sudden? The DJ turned the low frequencies down! There's a lot more to it, but this is the basis!",
"Everyone is chatting about EQing, but very few have mentioned beat-matching. This is the act of forcing two independent tracks (songs) to match beats so that when you use the crossfader (volume balance between two inputs - the independent tracks) to shift between the two songs, you don't hear a break in the beat. They blend the end of one track and the beginning of another together to make a contiguous \"set\" (a group of tracks beat matched together). Then there is scratching.....",
"The main technical job of a DJ is keeping the music constantly going so there's no silence between songs where people would stop dancing. With electronic music, which is my specialty, this is done by subtly blending songs together as they play. When 1 song is playing, you use your headphones to queue up another song on the other table, and use a pitch control slider on the turntable to match it to the same speed (BPM: beats per minute) as the one that's already playing. Once they're the same speed, you can use sliders on your mixer to start your blend, so both songs are playing simultaneously on the speakers. You also use the Equalizer knobs on the mixer to selectively add/remove song parts during your blend to make it sound more fluid. It's generally not good, for example, to have the bass on both songs playing at full volume at the same time, since it will overload the mix with bass. You do this gradual blend over the course of a minute or so (depending on your style of mixing), and eventually you will have completely faded out the previously playing song, and everyone is now just hearing the new one, without any break in the music. Then you do it all again. You used to have to do this all by ear, but now you have various readouts on a computer or CD player to assist with matching your song speeds more quickly and accurately, as a main challenge is being able to do all this quickly before you run out of time on the song that's playing. These devices also let you do things like loop parts of your songs in real time, to give you different blending options. Now having said all that, a DJ's REAL job is basically being a music curator, in the same way that an art gallery curator is. 90% of a DJ's work is done outside of a club/party. They're researching music, building a collection, practicing to see what songs work together and what doesn't. I've been a DJ for 15+ years and a main thing I've learned is that when you're DJing, you can make a number of technical mistakes and mess up a mix or 2 and people generally don't care (if they even notice) as long as you're playing great tracks. On the other hand, you can be the tightest, most perfect blender in the world, but if your music taste sucks you will be seen as a joke (kinda like when Paris Hilton became a DJ).",
"Think of the simplest set up, a single turn table, connected to a equalizer and amplifier for volume control plus a box of records. A DJ playing on this set up would play one song, including the introduction and ending of the song, pull the record off and replace it and play the next song beginning to end. It works but breaks the flow of the music, especially on a dance floor. So to make a seamless transition between two songs our DJ needs 2 turntables. One to keep playing the current song and a second to cue the next song. When they cue the song they can cut off the intro and get straight to the main part of the song. To transition between the two turn tables they need a mixer in the middle to select which turntable's output they hear and which the audience can hear. Plus adjust the highs, mids and lows so the music sounds in the same range as the other songs they've played. From there it's mostly artistic work to do fancy stuff like scratching, adjusting the speed of the song to try and beat match, etc.",
"Its called E Q-ing, (Equalizer) but most Deejays don't really do it for that reason, they want to look busy, real Djing where they push buttons, create sounds and effects is from touching the record in combination with the mixer fader to make sounds known as scratching, trick mixing, and beat juggling is called 'Turntablism' and not just blending beats from one record to another/blending, and yes they have mixers that have programmed sounds too, like a horn or a beat, chime, bell, et cetera.",
"I'd recommend going on YouTube and checking out some Boiler Room or Mixmag DJ sets. You can see high-quality DJs doing their thing in HD. You'll notice that most are using other equipment besides the usual two CDJs and a mixer. Some house/techno/dnb artists will utilize keyboards and MIDI pads during DJ sets for a much wider range of sounds and effects. Edit: also strongly recommend checking out a set IRL if you live near any good venues. I saw Tycho do a set at a club in Brooklyn last Friday- he was decent, was kinda bummed to see a laptop involved but hearing Open Eye Signal by Jon Hopkins on a world-class analog sound system was a treat. Saw Four Tet do an absolutely fire vinyl set at the same club a few months prior. Edit 2: if you see someone with a turntable emulator on their MacBook repeatedly smashing the air horn effect, that is not a good DJ."
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845b2g | What is reversible computing and what does it mean that it has no "energy cost?" | URL_0 | Technology | explainlikeimfive | {
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"Irreversible means you can't figure out the input from the output. As a simple example, let's say I have two numbers as input, add them together, and get the output 4. Can you figure out the input? No. Could have been (2,2) or (1,3) or something else. Information about the input has been lost. When it comes to energy cost, it seems no one is mentioning what's at work here. There's something called [Landauer's principle]( URL_0 ) which states that any irreversible computation must have a minimum energy cost. Frankly a very fascinating result that connects the fundamental laws of physics with information theory. Now, we're very far from that minimum in practice, but it means that no clever engineering could ever make a computer more efficient than that if we continue with irreversible computing. But reversible computing circumvents that fundamental limit. There's no known physical limit to how efficient we can perform reversible computing, so, as far as we know, it has the potential of being arbitrarily efficient. Fredkin gates is one possibility. Quantum computing is interestingly also reversible (that's not the power of quantum computing, but happens to be one of its properties)."
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8469kq | Why are we not able to make artificial human blood for medical use, or why is it not feasible if we are? | I recently donated blood and the thought occurred to me that this seems like a practice that will one day be unnecessary or looked back on as a barbaric form of medicine. Thanks. | Technology | explainlikeimfive | {
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"[Artificial blood is a thing]( URL_0 ). As you can read on the wiki, the issue is that we don't have a good way of getting it to transport oxygen, which is obviously a pretty vital function of blood. Also, as you can read, clinical trials for that are on currently ongoing.",
"While 'blood substitutes' certainly exist, they're not safe for regular use; haemoglobin (the main component in human blood) *loves* to bond with oxygen, which means that there's almost nothing left to oxygenate the tissues. Free-cell haemoglobin also damages the kidneys, and acts as a vasoconstrictor when it consumes nitric oxide. Researchers have experimented with using stem cells to create 'artificial blood' for many years now, but human trials only started in 2013, and so far, 'pharmed' blood (the technical term for the product and process) is expected to be limited to military use for a number of years.",
"100% artificial blood is a thing, but it's : -complicated to make : 100% man made, -complicated to use : it transports oxygen, but you need to get that oxygen from somewhere, like a bariatric chamber, -complicated to store : has to be frozen and thawed when needed, which takes time, -some had [annoying side effects like heart failure.]( URL_0 ) Hemoglobin based artificial blood is even more annoying because including all of the above, hemoglobin by itself (without the red blood cell all around it) will damage your veins and organs. And finally even if you make something that can transport oxygen it also needs to release it where it's needed, and that's a whole new brain tangler. So yes, producing artificial blood is a thing, it's been a thing since a long time ago, many failed to do it, many more are trying to do it now."
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846l6x | Paging and segmentation in Operating systems. | Technology | explainlikeimfive | {
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"To try put these concepts as simply as possible: Segmentation is the process where memory (RAM) is allocated out in chunks called segments. This allows an application to store various parts of itself and the data that it's working on in different parts of RAM. Imagine you have a big warehouse, but rather than just having a big empty space you subdivide it by filling it with shelves. As an application needs storage space the Operating System assigns it shelves that it can use, but these shelves do not necessarily need to be side by side. So long as the application knows that it owns shelves 567, 3214, and 5678, it can use that space as it sees fit. Paging is the process where memory is moved from one medium to another. So imagine you have two warehouses. One next to the dock (RAM) where you can process shipments quickly, and one in town (Hard Drive) that's considerably larger but slower. The warehouse at the Docks is fast so you want to use it as much as possible, but it just isn't big enough to store everything. So you move contents that aren't needed today out of the way and store them at the other facility until they are needed. The down side being that it takes time and effort to move stuff back and forth all the time."
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84a9o9 | Why are so many old/obsolete/unused assets left in code? | Technology | explainlikeimfive | {
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"When you’ve reached the end of a game’s development cycle, you want to be as cautious as possible, and you want to alter as little code as possible. Sure, assets may be unused or obsolete, but one weird line of code could mean removing that asset breaks some other aspect of the game. You don’t remove anything unless you’re *absolutely* certain its removal won’t affect any other systems."
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84e6lx | How do military guidance systems work when tracking fast moving objects that seem to lock on and track perfectly? | Some of the recent UFO sightings produced by the Military and Navy show pilots following UFO's utilizing their tracking/guidance systems, where the screen locks onto the object and maintains it. Is this an automated process that allows the aircraft to remain on course with it? URL_0 URL_1 | Technology | explainlikeimfive | {
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"In the video, the first part you can see the pilots actually moving (big cross hairs) the ATFLIR's view to keep the thing in view - this is manual or they can slave the view to the aircraft radar to some extent. Next, when that expanding box appears, the system has been told by the pilot to start picking up a thermal thing (this is an infra-red system). the expanding box is the systems acquisition mode. Then the IR spots the thing and then slaves its view; after that its current movement - relative to the aircraft, which the system ALSO knows whats going on - is easy to predict to keep in sight. (not military, I've just worked on enough similar systems to make an educated guess)",
"I am a retired Navy ship Radar technician. I don’t think that tracking is entirely off a radar system, but here’s how detection and tracking works at a simple level. A simple way to understand radar energy is to be in a dark room with a flashlight. Switch it in then switch it off. The bigger your beam the larger your search area was. The photons from the light bounced off the room and back to your eyes, much like a radar antenna receives reflected energy. This is basically how the search mode of a radar works - the radar knows how far away something is by how long it took the energy to return to the receiver after it was transmitted. Now have a person walking through the room and let’s say you have a flashlight that gives a smaller circle, and you point it at that person. We want a small beam here because we don’t want to be looking at other things. Switching your flashlight on and off, follow that person as they walk around the room. This is tracking. The radar computer actually attempts to guess based off all data where the target will be next, and may send beams around your target attempting to get that reflection. Once you have continual reflections back, the radar has an estimation of its speed and which direction it’s headed in. The same as you would do with your flashlight when pointing it at someone moving about the room. Now imagine the radar searching and tracking all the things flying around at a speed that makes it all seem to be happening simultaneously. Flashlight beams everywhere. There are some other factors such as the Doppler effect (good YouTube videos giving examples of this) that will let the radar know if the target is moving towards you or away."
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84gvig | Why do steam downloads on my windows laptop take days when the same game on my MacBook takes 30 minutes? | Technology | explainlikeimfive | {
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"> What factors affect the download speed relating to the OS? None. Whatever you're experiencing is likely a hardware, network, or bandwidth availability issue. All other things equal, you will see zero difference in download/upload speeds between different OSs. For example, if your Mac has a SSD (as most apple computers by default have higher end hardware) but the PCs you're used to using don't, your DOWNLOAD speed isn't being limited but a mechanical hard drive can only write so fast, so the computer will only download the file as fast as it can write it to disk."
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84kv46 | What are the long term effects of using different USB-C wattage chargers on different devices? | With USB C being as popular as it is having different chargers with different levels of power all over the house makes it convenient to just plug my USB-C devices into any of the laptop, switch, or phone chargers I have lying around. Is this harmful to the device? Why do some chargers have variable Volt outputs, and how does this work? The following are USB-C chargers that all get used amongst each other. Cell Phone OEM Power Brick: 5V == 3.0A, 9V == 2.0A (18W) Ultra Book 1 AC Adapter: 20V == 2.25A (45W) Ultra Book 2 AC Adapter: 5V/9V/15V == 3.0A, 20V == 3.25A (65W) Ultra Book 3 AC Adapter: 5V/9V/12V/15V == 3.0A, 20V == 2.25A (45W) External Battery Pack: 5V/9V/12V == 3.0A, 14.5V/20V == 2.25A (45W) Am I destroying everything or are we at a point in time where modern devices and chargers can limit power input and output using USB PD? Edit: Formatting. | Technology | explainlikeimfive | {
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"> Is this harmful to the device? No. Charger wattage is a maximum. If a charger can provide up to 65 W and your device only needs 5 W, then it'll get the 5 W. The only real consideration here is that chargers aren't equally efficient at all ranges, and that higher power chargers are bigger. So a 65 W charger is more inconvenient to carry, and using it to charge a cell phone may waste some small percentage of power vs using a lower power charger. However since phones use very little power the waste can be ignored in most situations. > Why do some chargers have variable Volt outputs, and how does this work? Ohm's law. The amount of power lost by sending it through a cable depends on the cable's resistance (which depends on the thickness) and current going through it. So if you want to send 65W and keep a low voltage, the cable would need to be thick. If you want to have thin wires, you have to increase the voltage. > Am I destroying everything or are we at a point in time where modern devices and chargers can limit power input and output using USB PD? It's all negotiated automatically. The only problem here is that a too weak charger won't be able to charge your laptop, and carrying a laptop charger around to charge your phone will take more room in your pocket for no additional benefit."
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84liak | how and by what means can the origin of the poison be determined, example from the recent poisoning in UK where they know it came from Russia? | Technology | explainlikeimfive | {
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"Certain details of the manufacturing process leave detectable impurities in the chemical. If you have samples to compare them to, you can determine with decent accuracy what lab they came from. The same sort of technique is used in drug investigations. Also, particular ingelredients may be local - as someone else mentioned - making it possible to determine origin. Edit: however, those sorts of things only tell you where it was *made.* Russia has, at times since the end of the Cold War, been a *bit* careless with their military stockpile. Presumably, this is why the Brits gave their unanswered 'deadline for explanation.' as opportunity for the Russians to explain the possible black-market movement of the chemical. They may also have other types of evidence, intercepted communications or some cool spy shit, that indicate direct Russian involvement."
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84pqis | Why do mobile networks have to “bid” for spectrum? Can’t they simply broadcast on it? | Not sure if this is just a UK thing but here mobile networks have to bid for spectrum. Is this like bidding for the right or the technology or? | Technology | explainlikeimfive | {
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"> Is this like bidding for the right Yes, it is exactly like that. If people were allowed to just transmit over whatever frequency they wanted then you would end up with companies and even private citizens all trying to talk over each other and interfering with their signals. Instead the government regulates who can transmit on what frequencies, and sells off the spots to whoever will pay for them."
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84rjhr | We have two ears, so surely two decent headphone drivers and some good software on the part of the game or film can perfectly replicate surround sound? Why do headphones come out with "virtual surround sound"? | Technology | explainlikeimfive | {
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"It is possible to have more or less \"perfect\" surround sound with headphones - it's called binaural recording. But it requires the recording to be made live and in a special way: two microphones are placed inside a dummy head complete with dummy ears to simulate exactly how the sound would reach our eardrums. Binaural recordings also have to be played back on headphones or earbuds - not speakers - for optimal effect. Music and movie soundtracks are engineered for optimal playback on home theater/stereo systems, where some of the sound from each speaker always reaches both ears, but after reflecting around the room and getting \"filtered\" through your ear structure. Virtual surround sound on headphones simulates this effect to convey the illusion that the sound is actually coming from speakers all around you instead of the typical \"inside your head\" sound from headphones.",
"You can certainly get really really close, yeah (though earphones tend to be unidirectional per ear, so realistically you'd need to cram a couple speakers into each cup since they aren't actually inside of your ear). The big issue is with the basic formats: 1) Many things aren't recorded/generated in surround sound. Obviously if they aren't then it can't be played well in surround. This is one of the big features of \"virtual surround sound\" software; turning dual channel into surround by guessing where things are (or knowing in the case of some games with good software interfaces). 2) If something is recorded in surround them it doesn't always transition well back to dual. Often dual will just play the left/right channels and ignore the others, which can make things lose quality because that information gets lost. Some sound cards can work backwards, but notably it's an issue. All that said you certainly can get very good recordings if they are done right with the right recording equipment; check out the \"virtual barber shop\" for a good example of this, it's just that most people don't necessarily record in that particular format because they aren't aiming to produce surround sound for headphones, they're aiming to produce surround sound for theaters."
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84rzq9 | Why does a 20000mAh external battery charge a 3500mAh phone 5 times over, but is unable to charge a 4640mAh laptop once? | Are mAh not a reliable quantitative measurement, like liters? | Technology | explainlikeimfive | {
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"You've likely got a problem of charge rates If you have a 10 watt charger attempting to charge a 9 watt-hour battery in a device that consumes 1 watt then it'll be charged in an hour If you have a 10 watt charger attempting to charge a 9 watt hour battery in a device that consumes 9 watts then it'll be charged in 9 hours If you have a 10 watt charger attempting to charge a 9 watt hour battery in a device that consumes 11 watts then it will never charge and will simply slow the rate the battery discharges Your laptop consumes significantly more at idle than your phone does. Chances are that the battery pack cannot output power faster than your laptop uses it. & nbsp; You also need to convert your mAh into watt hours which is actual energy. Your 20000 mAh battery pack runs at 3.7V and is 74 Wh, your 4640 mAh laptop battery runs at 11.7V(according to google) and is 54 Wh, which makes your laptop battery about 73% the capacity in watt-hours as your battery pack so if the laptop uses power at even half the rate your battery pack charges it at it will never charge it fully.",
"The mAh rating of a lithium battery is not *really* a flat, constant value, it's also based on how fast you're discharging the battery. The more power you draw, the shorter your battery will last **and** batteries are generally given capacity ratings based on their expected usage. A phone is going to draw less than 5W of power while a laptop might run 50W - this can really make it difficult to compare the batteries between the two. Furthermore, when charging these devices, the laptop is going to draw much more power.",
"Generally the phone and laptop are different voltages. I've never seen a charger that works for both, though I suppose it might exist with some very specialized circuitry, but it's not an ideal situation. You see, the work something can do, the energy it has is dependent on both the voltage AND the current, which multiply together to form watts. A gallon of rocket fuel puts out a lot more energy then a gallon of car gasoline. To make the energy in one gallon of rocket fuel, you'd need a lot more gallons of car gasoline. Similarly, there's a lot more energy in a 28v 2000mah battery than in a 5V 2000mah battery. And to get the energy of the 28 2000mah battery, you'd need a lot of 5v 28v batteries (and a system designed to convert them. Just like a rocket won't run on car gas no matter how much you put in, and a car would explode with rocket fuel, you need to match your strength to your use) Batteries are specified by both voltage and by mah. So if your battery has like 2000mah at 5v, and your laptop needs 15v (made up numbers, check your specs) , there needs to be either some circuitry in the battery or the laptop that converts the 5v to 15v. To do this, it needs at least 3 times as much current to get the same energy. At least because there is always ineffeciency in conversion."
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850xug | What is video rendering? | I do not understand what the computer is doing while rendering a video. I just saw a post from a video that took 3 day rendering. And when you upload a video to YouTube, it has to render as well, why? The video isn’t done already? | Technology | explainlikeimfive | {
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"A video file is basically a series of compressed still images that the computer plays back one after another. But when you're editing video in editing software, you're essentially creating a \"recipe\" for how to create a video from a bunch of individual clips, images, effects, etc. Let's take a simple example of filming yourself against a green screen and replacing the background with another video clip. When you create the chroma key effect, layer the two clips and then save your project, you're really just saving instructions that say \"take video A, make all the greenish pixels transparent, and then show video B behind it\". This is not a finished video file, just like a cake recipe along with the ingredients is not a finished cake. Rendering the video is akin to baking the cake. Editing the video in the editing software is like deciding on the cake recipe. As others mentioned, YouTube's \"rendering\" of uploaded videos is really just re-encoding."
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8510l7 | Why can we plug in our phones 1 second before they die and be just fine, but if we plug them in 1 second after they die we have to wait a few minutes? | Technology | explainlikeimfive | {
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"It is to prevent the device turning on and off repeatedly. Maybe you have noticed that a radio or torch with flat batteries can be made to work again, for a little time, by turning it off and waiting a minute or so. They call this the 'rebound effect'. There are chemicals inside the battery, and when flat, there's not much of the chemicals available. The chemicals near the electrodes can then be totally used up even though there are a small amount still available further away. If you stop using the battery, some of these will migrate closer to the electrodes, and the battery will work a bit better, for a short time, until that tiny amount too is depleted. This happens with your phone battery, too. So if your phone turned off because the battery was flat (dropped below 3.0 volts), the rebound effect would soon lift the voltage back to 3.1 or 3.2. This could convince the circuits to turn the phone back on - but the battery is still flat, so would drop back to 3.0 volts within a few seconds. Not only is this bad for the battery, but it isn't good for the phone to die in the middle of starting up (they are reasonably advanced computers, after all), and it isn't a good experience for you, either - it just wasted your time, annoyed you, and you might think your phone is broken, not just flat. So all systems like this use 'hysteresis' - They turn off when the voltage gets down to one point, and won't turn on until it reaches another higher point. This affects you when charging - they phone turns itself off - carefully and properly, before the power has to be shut off instantly to protect it - and won't turn back on until there is at least enough charge to allow it to properly start up. This brings us to one last point - the chemical condition of the battery is a bit fragile when dead flat. So when starting the charge, the system is gentle, only pushing a little electricty through the cell to get charging started. So that first bit of charging, until there is enough power to start it up, takes a little bit more time.",
"When a phone dies, all the ongoing processes are terminated, so it has to go through the whole sequence of booting up again. If you catch it before it does then it never turned off so it doesn't have to start back up again.",
"It takes more energy to start up a phone than it does to just keep it running, similar to a car or a more traditional computer."
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851284 | How is local cable internet routed? | It came to me in the shower, as all good questions do, how is traffic routed on the last mile of cable internet? Is all the traffic sent down all the lines in the neighborhood like electricity, to bounce off or go through an individual modem? Or is there a router on each service pole that points certain packets to certain homes? | Technology | explainlikeimfive | {
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"Your house is part of your nehighborhood cable segment. Everyone on the segment is connected, via splitters and amps, to a cable headend system. The size of the segment depends on the cable company. Bigger segment = fewer expensive headends,but greater amounts of traffic on that segment. Now, every cable modem on the network has a unique hardware address. The headend unit (called a cmts) keeps track of all of the units assigned and subscribed to that segment. Now when an IP packet arrives from the internet, destined for you, the cmts looks at the packet and knows that IP address 3.4.5.6 was assigned to the cable modem with a hardware address of de:ad:be:ef:aa (hardware addresses are usually hexadecimal). So it takes that IP packet and wraps it in a Network frame that it can send over the cable plant with your cable modem address as the destination. The cmts doesn’t have a direct connection to you only. The cmts throws the packet out the wire and everyone can hear it, but everyone but your cable modem Ignores it. If you want to send a packet To the Internet, it’s a bit different. All of the modems on the segment share a range of frequencies to send data back. They share it by transmitting on a certain bit of spectrum at a given time. Lots of modems all waiting their turn to transmit.",
"Mostly the former. The cable system is a broadcast medium. Anything sent in at the head-end goes to all subscribers. Your modem only passes through the traffic that is for you, and encryption protects the privacy of other traffic if you were to sniff everything. I say \"mostly\" because the cable company can put nodes nearer to your house. Those aren't literally routers, but they shrink the size of the broadcast domain. That is, instead of having one CMTS (the opposite device from your modem) serving the whole town, they might serve only a neighborhood."
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853iir | If electric cars are the future, why is interest(funding/research) really picking up today when they have been around for over 100 years? | Technology | explainlikeimfive | {
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"Back then there may have been electric cars but they were too expensive to mass produce and sell. And the electric cars were probably no more better than the fuel driven counterpart as far as efficiency. Also the technology of today has finally reached a point where it's do-able to mass produce and sell. Since we have electric cars that are mass produced... now it is only a race to see who can make them more efficient. The research and funding are geared to newer solutions to harnessing the electricity that powers them as well as finding alternate fuels such as water.",
"Because lead-acid batteries have horrible energy densities. Nickel Cadmium too, anyone who has used RC planes before Lipos knows how blessed we are today. Li-ion only commercialized in the 90s and even now li-ion has a rather low energy density compared to fuel. Batteries (and supercapacitors) are very tricky, a lot that works in the lab doesn't work outside. It also took us a very long time before we knew what to do with semi-conductors, sometimes it takes just takes a long time to improve something enough to make it viable. People are too quick to blame it all on \"corporate greed\". Edit: There's also the problem that batteries lose capacity from discharging, which has improved a lot over 100 years.(cycle durability has increased) Charge/discharge efficiency has also improved a lot over the last 100 years.",
"There are a couple key technologies that are important for electric cars, which just weren't good enough back then. One is of course the battery. Batteries have improved more than fivefold since then - so any electric car would have had considerably less range than today. Then there is power regulation. In a car, you need to be able to precisely adjust the amount of power coming from the motor, which can be done quite easily with a throttle of a conventional combustion engine - but in an electric car, you need to change the voltage. And that is very difficult with a DC power source like a battery. Today, this is done with very efficient and fast switches made from semi-conductors, but 100 years ago, semi-conductors weren't even discovered yet. To get the same result with technology from 100 years ago, you would have to use a very bulky and inefficient circuit to control the engine. Lastly, there's the problem of charging. A large battery needs a lot of DC electricity to charge quickly, making the charging infrastructure very expensive. That's still a problem today, even though electrification and technology in general is much better.",
"Guess battery power has improved alot. That is still the problem with an electric car. They don't have good range."
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855bxe | Why do “selfie cameras” flip a picture, but the rear cameras don’t? | Technology | explainlikeimfive | {
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"By making the selfie camera act like a mirror, it becomes easier to coordinate yourself for your picture. It's all about a postive User Experience (UX)",
"People are used to how they see themselves in the mirror. I think a lot of people, in fact, _dislike_ how they look from another's person's perspective. I know I do. In order to increase user comfort, and especially on apps like Snapchat and Instagram, where looks are very important, developers mirror the image so that the user sees what they would in a mirror.",
"Fun fact: on iPhones, the live preview of your camera in selfie mode is flipped so that it behaves like a mirror and you’re better able to easily handle it (we are taught from a young age to understand what a mirror does and how it behaves). However.... as soon as you take the photo, the image saved to your phone’s memory is unflipped, because otherwise when someone else looks at the photo, they’d realize it didn’t look like you because our faces are not perfectly symmetrical.",
"Selfie cameras flip the picture so our brains interpret the image as a *mirror image.* In a rear facing camera, the image is not flipped. However, you are facing the opposite direction as the camera, making you perceive it as a mirror image."
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855tbh | Why does gps need almanac data? | Been reading about GPS recently but this confused me a bit. Why isn’t time and ephemeris sufficient to triangulate position? Sure it gives the rough position of the satellites so that the GPS knows which signals to listen for, but can it not just listen for all satellites? | Technology | explainlikeimfive | {
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"It could, but that would mean a lot more processing. Almanac data is almost always available, so it is much more efficient to use that instead of listening to everything and then figuring things out from there.",
"You could listen for all the satellites at the same time, but it takes up a lot of signal processing power. GPS satellites transmit almanac data every 12 minutes so your GPS receiver knows which satellites to look for. In military applications it also makes it harder to spoof as military receivers can listen for an encrypted signal and will ignore signals from satellites that aren't supposed to be visible."
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857wge | Which files does an antivirus software scan when doing a "quick scan"? Why are those most likely to be infected? | Technology | explainlikeimfive | {
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"For a virus to do its job it has to be running on your computer not just sitting on the harddrive like a book on the shelf. Sort of like all the open books on your school desk. So a quick scan just needs to scan all the running programs in the computers memory and \"almost\" avoid the harddrive. It ignores the library books and just scans the open books that are on your desk that you are using.",
"It depends on the antivirus product, but generally it skips files that haven't been changed or edited since the last full scan. Quick scan usually still scans the entire RAM, but that's relatively fast compared to how long it'd take to chew through the entire HD worth of stuff."
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859eve | Can leaving a device, such as a smartphone, on a charger after it's reached 100% battery for an extended period of time damage, or have long-term effects on the battery? | Technology | explainlikeimfive | {
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"Your phone and laptop have battery controller chips that regulate charging and discharging to keep the battery within the allowed current, voltage, temperature, and charge range. When the battery is \"full\" the controller will stop charging the battery and the phone will run off the incoming power directly rather than sending it through the battery and back out With modern devices the assumption is that the random charger you plug it into will be garbage so they all have their own controller that will protect them. You don't damage your phone by letting it charge overnight"
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859lx5 | Why are satellites more powerful than wifi? | To my admittedly little knowledge, our satellites are like 50+ years old in outer space but my wifi antenna is brand new and in my house. I can't get my wifi in my drive way YET I can get satellite signal for my GPS anywhere in the United States like immediately. Why? | Technology | explainlikeimfive | {
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"The distance a radio signal can travel is based on how strong the signal is. GPS satellites are allowed to broadcast very strong signals. Your Wi-Fi transmitter is not. This isn't a technical limitation, it's a legal one. The reason your Wi-Fi router's signal strength is limited is that if everyone broadcast really strong signals on the same frequency (and Wi-Fi is only allowed to be on a limited range of frequencies), they'd all interfere with each other and no one's Wi-Fi would work. Think of it like 100 people trying to shout in the same room at the same time, versus everyone having a quiet conversation with the person next to them. Since GPS was set up by the government, it was given its own dedicated set of frequencies and no one else is allowed to have any radio transmitters on those frequencies so everyone's GPS receivers can hear the satellites.",
"GPS satellites broadcast a much stronger signal than your home wifi can. They broadcast on reserved frequencies that nobody else uses while wifi needs to be shared with everyone and everything. They also don't need to receive any data from your phone. It's a one-way system.",
"Satellites are big and GPS only needs your device to *receive* data. WiFi requires your phone to *send* data, and it is a *lot* more data, back and forth, sent via your teensy phone antennae."
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85buhw | How do projector display the color black? | Technology | explainlikeimfive | {
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"text": [
"By using contrast. Your eye adjusts itself to a specific level of brightness, anything a lot dimmer than the brightest thing you can see will appear as black. Imagine taking a glow stick and holding at arm's length towards the sun. It would appear dark, even though it would seem to glow brightly at night.",
"Try this experiment - take two paper towel rolls, one sheet of white paper, and one sheet of black paper. Look through the paper towel rolls at each one (one for the right eye, one for the left eye). Now shine a very bright light onto the black paper, but not the white paper (you might need to put a book or something separating the two sheets). If the light is bright enough, both papers will appear the same shade of white. Black and white only appear different due to their surroundings. You can also look up the checker shadow illusion to see the same effect."
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85czde | How do scientists know anything about distant planets beyond what they look like? | How do scientists know what the core, crust, and mantle of other planets are? Also, just the other day I read about a planet that rains glass made of a specific element (that I can't remember, I'll try to find it and link it in an edit). How do they know these specific little things if our crowning astronomical achievements haven't even left our solar system? | Technology | explainlikeimfive | {
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"text": [
"What we know about planets in other solar systems is very limited; in some cases, what you're reading about is pure speculation--the conditions on that planet are right to let something like the formation of diamond crystals in the atmosphere. What *can* we actually know? Well, in some cases we find the planet based on its gravity pulling on the star, and knowing something about how gravity works, we can figure out what its overall mass is and how far it is from the star. In other cases, we find it when it goes in front of the star and blocks light, which lets us figure out how big across it is. Combining mass and physical size gives us density, which lets us take a first guess as to what it's made of. Knowing how hot the star is and how close the planet is lets us take a guess at how hot it would be on the surface of the planet...though we have to make assumptions about how shiny it is, since very reflective planets would bounce off most of the light and wouldn't get as hot. In some cases, we can see the infrared glow of the planet directly, and measure its temperature that way. If we can see it blocking the star's light, we can look at what kinds of light are getting absorbed right as it starts to move in front of the star, which tells us about what gases are in the atmosphere. Combining all of the above lets us constrain our guesses better, to where we can feel more and more confident about what's probably there."
],
"score": [
15
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
85d9b7 | Why do some games handle alt+tab between them and other applications well, and others handle it really badly or not at all? | Technology | explainlikeimfive | {
"a_id": [
"dvwjwwl"
],
"text": [
"Imagine you run an factory that has a hundred employees, each of them doing different jobs with different equipment. You get on the intercom and say \"Everyone put what you are doing on hold and meet me out in the parking lot as soon as you can.\" Most likely, it would take some people a lot more time to get out there than others. Some people have dangerous equipment that has to be shut down, while others are working more simple machines they can just flip a switch on and walk away. Some people are a bit more careless and will walk out without checking everything a bunch of times, and others will be too worried and want to make sure everything is perfect. Some people may even feel that they simply can't leave their post and so they never walk out. Just like how there are a lot of differences in how each worker will stop what they are doing and walk out into a parking lot, there are a lot of differences in how each program will handle losing or gaining focus. Generally speaking, when a program isn't in focus it will put some of its tasks on hold, but how much they put on hold versus how much they continue to do will vary. Likewise, they have to transition from a state of displaying information and interacting to not doing that or visa versa, and these changes in state require a little bit of work. And different programmers aren't necessarily going to have the same values, so some aren't going to want to optimize these functions as much as others will (generally, high-resolution video games are going to have a hard time transitioning between having focus and not because they take up a lot of resources and the programmers expect players won't constantly be exiting and leaving them anyway, for instance.)"
],
"score": [
9
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
85dcqr | How do apps keep up with updates in OS(android,iOS etc.) | Technology | explainlikeimfive | {
"a_id": [
"dvwkfkg"
],
"text": [
"Well often times they don't bother, but in general os updates are announced in advance and are fairly well documented so devs can get pre-release versions to test their app and keep up. OS updates aren't released as frequently - minor ones only a few times a year and the big ones less so - often times about once per year. Good devs interested in maintaining their app pay attention to whats happening and ensures that there aren't any show stoppers and they can release updates anytime they want."
],
"score": [
3
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
|
85dq3n | Why do photographs have different pixel densities (or even a pixel density at all) if a camera takes pictures by taking a snapshot of light? | For example: two different photographs with the same aspect ratio could have different pixel densities. | Technology | explainlikeimfive | {
"a_id": [
"dvwn54r",
"dvwn20n"
],
"text": [
"The CMOS sensor. It's a big grid of photodetectors, and the lens is designed to focus incoming light to hit the big grid of sensors. Each spot on the grid translates to one pixel in the final product. CMOS censors vary in how big their grid of sensors are and how many are packed into one space.",
"In the world of digital photography it's a question of how the information used to display a picture is stored. A picture has to be encoded digitally in a manner that can be stored on media, like a flash drive. Which means it has to be broken down into a series of 1's and 0's A common picture format like a bitmap (BMP) or jpeg isn't actually the picture itself, but rather a set of instructions on how to re-create that picture on a monitor or TV. Pixel density is the resolution, say 800 x 600, the higher the resolution the better the quality of the image. But higher quality also means a larger size of file. The file will be a set of instructions that reads like: Pixel 1 x 1 - color is 255 16 75 Pixel 1 x 2 - color is 255 16 76 ... etc Where the color is listed as numbers 0-255 RGB (Red, Green, Blue) By reading these instructions your monitor, or your printer for that matter, can recreate the image on a screen by painting the individual pixels the colors specified. Edit: the color I listed is a hot pink for the record, I just picked random numbers"
],
"score": [
3,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
85e5v5 | Why do rechargeable batteries become worse/less effective with time? | My phone for example. Absolutely fine battery lifetime when purchased about 2 years ago. Now - a joke; absolutely horrific lifetime. Why is it like this? | Technology | explainlikeimfive | {
"a_id": [
"dvwrmrp"
],
"text": [
"Batteries work by a chemical reaction that produces electricity. Rechargable batteries work by a reversible chemical reaction, but it isn't *perfectly 100.0% reversible* If it's 99.9% reversible then you're down to 74% capacity after 300 charge cycles and 54% after 600(about 2 years) People like to complain it's planned obsolescence but it's not planned for, it's planned around. You want something cheap that'll work for a couple years rather than something obscenely expensive that'll work for a few decades"
],
"score": [
8
],
"text_urls": [
[]
]
} | [
"url"
] | [
"url"
] |
85fclu | What is a 'dirty bomb' and how do they work? | Technology | explainlikeimfive | {
"a_id": [
"dvx0863",
"dvxfauc"
],
"text": [
"A dirty bomb is a hypothetical (I don't believe one has ever been used) weapon that uses conventional explosive to disperse radioactive material over an area. Basically imagine a bomb wrapped in something radioactive. It's not a nuclear weapon because there is no actual nuclear reaction, but it will still cause an area to be contaminated with radiation. The radioactive material would also not need to be enriched anywhere near the same degree as what would be required for a nuclear weapon.",
"Frustrating that many answers here are almost right but then take swerves in the wrong direction. A dirty bomb is a bomb (e.g., regular explosives, like TNT or C4 or dynamite) that is wrapped in radioactive material. Blowing up the C4 (or whatever) vaporizes and spreads the radioactive material. It is mostly a contamination weapon; it is not likely to immediately kill many more people than the C4 would by itself. The radioactive material is _not_ the same stuff you'd use in a nuclear weapon, and it's not nuclear waste (which would be very tricky to handle). The most likely isotopes people worry about are those that are used in medical applications, because they can be stolen from hospitals. So Iridium-192, Cobalt-60, and Cesium-137 are all fairly radioactive sources used in radiotherapy machines. The fear about dirty bombs is that they would be useful weapons for a terrorist, because in theory they are relatively easy to make (at least compared to nuclear weapons themselves, which operate totally differently and with different sort of fuel), and because people's fear of radioactivity would make them susceptible to mass panic. At the very least, cleaning up a contaminated area would be very expensive. So far nobody has used one."
],
"score": [
9,
3
],
"text_urls": [
[],
[]
]
} | [
"url"
] | [
"url"
] |
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