Asklemmy

The electric field one is also interesting, because the cable length doesn’t actually determine how long it takes to turn on. All that matters is the distance between the power source and the device. Electricity travels at the speed of light, which means we can measure how long it should take to travel down the wire.

But let’s say you have a 1 light year long power cable, made out of a perfect conductor (so we don’t need to worry about power loss from things like wire resistance or heat). Then you set the power source right next to the device and turn it on. The logical person may say that the device would take a full year to turn on, because the cable is one light year long. Others may say that it will take two light years to turn on; Long enough for the electricity to make a full circuit down the cable and back to the power source again.

But instead, the device turns on (nearly) instantly. Because the wire isn’t actually what causes the device to turn on. The device turns on because of an EM field between itself and the power source. The wire is simply facilitating the creation of that field. The only thing that matters is the distance between the source of power and the device. That distance, divided by the speed of light, is how long the device will take to turn on. If the device was a full light year away from the power source, it would take a full year to turn on. But since the device is sitting right next to the power source, it turns on right away.

Doesn't it have a much bigger population than Aus? Wikipedia says that California has about 39 million people and Australia only 27 million.

Australia feels like a small country stretched around the perimeter of a genuinely impressive quantity of absolutely nothing.

This is also why trees are so fucking crazy to think about. It is impossible to pump water up a hose more than ~32 feet. Like it’s literally physically impossible to stick a pump at the top of a tall building and suck water straight up a pipe. You need a complicated series of pumps and one-way valves to pump it up in stages. Because you’re not really “sucking” the water up the pipe. You’re just lowering the pressure in the pipe, and atmospheric pressure pushes the water upwards to fill the low pressure. After 32 feet tall, the top of the hose/pipe will be a perfect vacuum, atmospheric pressure won’t be able to push liquid water upwards any farther, and the water will just begin cold-boiling in the top of the pipe as the liquid water turns into gas (steam) to fill the vacuum.

But tall trees can move water all the way to their leaves by using only passive capillary action, and suction created by water evaporating out of their leaves. The capillary action is created by tiny straw-like fibers that run all the way up the tree and are bunched together really tightly. Due to surface tension, water is able to “climb” the capillaries as the surface tension fills as much surface area as possible. Then at the top of the tree, as the water evaporates out of the leaves, it draws up fresh water to fill the void.

But that means the bottom of the tree should need to support the pressure of all of the water above it. But it doesn’t, because the surface tension holds the water stable inside of the trunk.

Therefore a graduated cylinder that is 10m tall needs to resist the same amount of force as a dam 10m tall regardless of how much water is behind the dam. Even a thin sliver of water 1mm thick and 5m tall has the same force as a 5m lake behind the dam.

Technically only the pressures are equal, and the actual force will be linearly dependent on the area of the dam (or the surface area of the cylinder). That's why you can make a tall water tank with relatively thin walls, but an actual dam will have to be quite thicc to handle the tensile/compressive stress (depending on the shape of the dam).

Thank you. Your hypothetical question has been a nagging, unresolved background radiation in my mind for decades, but I’d never gotten around to investigating.

That is accounting for static bodies of water, wouldn't there be force generated in a dynamic situation? Ie the flow of a fast river? Or if the lake is large enough tidal forces? I'm sure it's negligible levels but still something that must be accounted for?

While I think your point is true that its much more abstract than people realize. When I worked at a bank and we disbursed loans and credited/debited fees it was from "GLs" (General Ledger?) which were basically just separate accounts to help keep track. Like we had a "member service" one which was for basically anything with good reason. One time someone did a very large amount but he just basically got told to do it a different way.

Its all just in a computer. I could've accidentally credited someone a million dollars but it would've been realized when I tried to close my drawer and balance everything out. And the branch would have to be balanced at the end of the day so I assume the bank did as well.

On a related note banks take out loans from other banks. I think a lot of people don't realize that banks have savings accounts so they have money to lend.

Which is why a "run on the Bank" or "Bank run" is unsustainable for Banks these days.

Gulp..."was"?