Software has logical ‘states’ that work best when they flow into each other as planned. If you have a bug and get into a weird state, powering down and up sends you back to the known initial state, from which things should progress as expected.

A lot of effort in embedded software goes into not getting into bad states and if you do, recovering, but sometimes mistakes are made, or management cheaps out and bugs remain.

1. wipes the temporary memory (volatile). A program may have hit a loops (tried to follow instructions, but got lost and is now going in circles looking for a line of code that doesn't exist). If you shut it down, all those processes stop running, and the system starts each program over from scratch so the program knows "where" it is.

2. Most modern computers have a bunch of software dedicated to checking both software and hardware problems when it starts up. It can fix a lot of these.

3. Sometimes the issue is the user, not the system. Restarting it gets you back at the beginning of your task, and maybe you'll pay closer attention and get it right this time.

4. some updates don't apply until after a restart happens - these updates may fix your issue.

5. it kills all running program. You might have started something in the background that is taking up a ton of resources and causing the problem that you aren't even using. restarting will shut that down and let the programs you want to run have the resources it needs.

When things run for a while they can have mess ups

Most startup processes on most items have a startup process which runs a very basic start of default services or actions.

By simply just turning the power on and off it allows the startup to run again and essentially reset and have no issues because it starts up correctly using the basic default startup parameters.

Easiest way I have explaining it is it's like a zipper that went a little off track. Sometimes the only way to get that zipper right again is to undo the whole thing and start from scratch.

The little errors in software are like pubes getting stuck in your fly. Sometimes the zipper or software still kinda work, sometimes everything will be off by a bit, and sometimes it just fails completely and you have to start again.

Well, it doesn't. Yes, it resets the state to the known good (see other comments), but it most likely doesn't fix the actual cause of the problem, but rather hides it.

Its "the best" because its very fast, everyone understands what to do and you dont need to figure out what even went wrong or how to fix it. Most things could be fixed without a restart but it requires knowledge, time and access to the device. So why try to use valuable time from someone with knowledge if a restart also works.

Imagine a computer like a person. As you get tired you start to make mistakes. The more tired you are, the more mistakes you make and those mistakes stack up and lead to other mistakes. Little brain facts, clumsiness, not paying attention, etc. Sleep is a good reset of your mind and you wake up well rested.

Computers are similar. They start to have little mistakes as temp memory gets filled up over time. A power cycle resets that temp memory and clears any junk. Gives the computer a good night's sleep.

It's a very simple process to understand. Most powered devices are designed to automatically configure or arrange themselves in a way that prepares them to perform whatever work they're intended to do. They're also often designed to return to a state when turned off that allows them to do the work needed at startup to prepare for use.

That work often requires a sequence of steps or has a number of parallel steps that are intended to occur in an order to achieve the device's purpose. Sometimes things can happen the push those steps out of order or into conflict, and trying to go back and sort out what exactly went wrong, correct it, and then correct all the subsequent steps that may have been impacts is impractical.

When you turn the device off, it returns to that pre-startup state, and turning it back on restarts all those steps it automatically does to prepare for use, and as long as whatever set of circumstances caused the original problem don't happen again, the device can return to normal operation.

Simply put, there are constantly numerous processes running in the background on your computer that you probably aren't aware of. All of them constantly use your computer's memory to some extent. They read and write stuff in your computer.

Now, there are two types of memory on your computer, volatile, and non-volatile. Volatile memory gets deleted when you reboot your computer whereas non-volatile stays in place.

Generally speaking, your computer has two types of memory, ROM, which is your long term storage (though the term ROM, which is short for read only memory, is kind of inaccurate, as it implies that you can only read what is stored, but not write to storage, or in other words, you can access the file, but not modify it), and RAM, or random access memory, which is your working memory.

Now, ROM is always non-volatile, but RAM isn't. RAM is, however, faster than ROM, which is why both types are used. Sometimes, what you need is the ability to read and write quickly rather than the ability to store a file long term.

What's any of this have to do with these processes running in the background? Well, as they run, they may store data in your RAM that just doesn't get deleted. Afterall, even the most avid PC users rarely let their PC run continuously for more than maybe 12 hours, so leaving some files undeleted in a place that gets reset anyway after a few hours isn't a big deal.

However, in the odd situation where this does break something, you can just reboot your PC and that solves it. Same thing with many other software programs. They store various types of settings in RAM. Often times, these are settings are things you're not even aware exist, because they run in the background, without your computer ever letting you know they exist in the first place. If something goes awry, restarting the computer will often fix it for the same reason.

Sometimes you need to not only shut down, but yank the power cable.

After shutdown, some components may still get power, I would guess to keep them warm and ready for reboot.

I've seen router problems which persist after shutdown / reboot, but fixed by unplugging the power for a minute before reboot.

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it is not the best troubleshooting method we have, not by a long shot. but it is the easiest one that still is able to solve some (or even most) problems. because of that it is always the first go-to method before trying something more involved like deciphering logs or error codes to try and understand the source of the problem.

Not just computers, but most complex machines tend to have some kind of "memory". Stuff like jukeboxes could work way before we had computers, they used circuits we call "electromechanical" to basically accomplish what computers do with bigger, bulkier components.

Let's stick with a physical example. Some motors are very precise about how far they'll move if they recieve power for specific amounts of time. So robot arms and other things that need to do repetitive motions follow a "program" that's really just them applying power to the motors in specific patterns. But if something goes wrong and a gear slips, that can muck everything up. That means the arm didn't move as much as it should have, so from that point on the program's just a little bit wrong. If it keeps happening, the robot arm won't be doing what it's supposed to and is likely going to cause damage to something.

The startup process for these kinds of machines involves getting it into a "known state". For this kind of motor, it means there's usually physical barriers that stop the motor from turning too far in one direction. So to get it in a "known state", when the machine starts up it will turn the motor in that direction until sensors tell it that it has reached as far as it can go. (Or, it turns for an amount of time guaranteed to put it in that position.) Now the system "knows" where the motor is again and is safe.

(More sophisticated motors have more sensors and can tell where they are, but they cost more and don't make this explanation work so well.)

That's kind of what can happen with computers and more sophisticated machines, too. Their program or even the circuits may have tiny problems that cause tiny mistakes. Those mistakes may not be harmful for the first few hours, which is why the developers didn't notice them. But over time those tiny mistakes might add up and start causing the program to do weird things, sort of like how if the gear for the robot arm slips the program is now incorrect because the arm is not in the position it should be.

The reason you have to sometimes leave it off "for about 5 minutes" is interesting. NORMALLY a good computer should go through all of its memory and set it back to a safe state when it starts up. But that can take a long time so it's a step that might get skipped. But most memory doesn't "hold" its value for very long if the power is not on, and eventually ends up in the known state anyway. So if the program doesn't clear memory at startup (or if there's a bug that causes it to miss some memory), turning off the power for long enough to make ALL of the memory reset can fix that little issue.

So it's kind of like if after you turn off the robot arm, you manually manipulate it into the "safe" position before turning it on. That makes sure it's in the state the program expects.

Think of a grid-like city, and you have to go to the supermarket starting from your house, you follow directions to get there but one time you make the wrong turn, and you get lost therefore you can't arrive to your destination.

When you turn off and on, is like you're transported back to your house and you can start again to follow instructions to arrive at your destination. It's almost the same with computers and devices.

Agreed! I think your comment is a well articluated version of my understanding. But I want to know the deep, deep rationale behind it. It seems so crazy to me that in our advanced technology world that the best troubleshooting is to turn it off and on again.

Well, you see, it's all about the magical power of the "off" and "on" buttons. When you turn something off, you're essentially giving it a chance to take a breather and clear its head, so to speak. And when you turn it back on, it's like giving it a fresh start, a clean slate. It's like sending it off to IT rehab for a quick reset.

Plus, let's face it, sometimes the machines just need a good kick in the circuits to get them going again. And what better way to do that than by turning them off and on again? It's like a gentle reminder that they're not the boss of us, we're the boss of them.

Of course, it's not a cure-all for every IT problem, but for those pesky glitches and hiccups that seem to crop up out of nowhere, it's a tried-and-true method that never fails. So go ahead, give it a try. Turn it off and on again. You might be surprised at just how effective it can be.

Moss

Because computers a really good at following instructions. They love following steps. But if something goes wrong and they get off of those steps it’s very hard for them to find their way back into them. But if you force the computer to start over at the beginning, chances are it will complete the steps just find as long as nothing goes wrong.

So turning something on and off again is essentially just saying “hey, you messed something up but you can do this, I’m gonna put you back at the start, try again.”

There are two types of memory volatile and non-volatile. Volatile means that it gets erased if it loses power and non-volatile means it stays if it loses power.

When your computer loads a program it loads it into volatile memory as it's a lot faster to access and make changes to. However, because it's making changes to it, it might do something weird that causes the program to mess up to either that specific program or something else that interacts with it.

By "turning it off and on again" you reset all of the volatile memory and reset it to its initial state, before it caused that issue for itself.

The scale tilts a bit and some of the force is applied "from the side" and not paralel with the spring.

That's the eli5 part.

To be more specific, it will only measure a portion of the straight down force vector.

Yes and no - water on a flat surface with an open edge doesn't drain at the same speed as water on a smooth slope. You can build up a shallow pool on each ledge that will spilling over the open side. With enough rain, the effect will be overcome and it will basically end up the same and with light enough rain, some of the water will get trapped on the roof and evaporate off but in the middle it should work.
I don't really feel like digging out my old fluid dynamics notes to try to calculate it out but the basic principle makes sense

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Bermuda is a rock in the Atlantic Ocean 600 miles east of North Carolina.

The roofs are made of limestone and the ridges channel the water in a pattern across the limestone in an effort to clean it, then it lands in a collection barrel.

> Surely rainfall is even over a surface regardless of terrain and therefore a ridged roof would collect the same amount as a smooth slopes roof?

Of course. It's the cross sectional area of the roof that matters, not the surface area. Imagine that there is no wind, and the rain is falling straight down. It's not going to make any difference whether the rain falls on a flat roof, a tall A-frame roof, a mansard roof, a hip roof, a roof with ridges, or a smooth roof.

Bermuda is primarily a limestone island. The original roofs on houses were made from limestone slabs quarried on the spot. The pit that the limestone slabs were quarried from became the cistern in which the rainwater was collected. Being somewhat thick, these limestone slabs gave the roof a stepped appearance. Over the years, this stepped appearance became the norm for what roofs were supposed to look like. Modern Bermuda roof systems are made to look like the old limestone tile systems because that's what people expect.

Long story short, the ridges are aesthetic, not functional.

P.S. Bermuda needs to collect rainwater because there are very few other sources of fresh water on the island. The government mandates that at least 80% of the roof needs to be dedicated to harvesting rainwater.

A scale works by compressing something and measuring how much that thing is compressed. In an analogue scale, that's usually a spring that turns a dial when compressed. In a digital scale, its usually a wire with a current being run through it - when the wire is compressed, the wire's resistance increases so the amount of current flowing decreases.

When you put a scale on a hard surface, there is nothing under the scale to compress, so 100% of the compression is focused on whatever inside the scale is measuring compression.

When you put a scale on a soft surface, like a carpet, the carpet functions as a continuation of the measuring surface inside of the scale. IE, some of the compressive force being applied to the scale is instead applied to the carpet, reducing the amount of force on the internal components of the scale.