Why do people, submarines, and essentially everything that dives too far into the water get crushed? I get that it’s the weight of the water, but shouldn’t the pressure just come from the top and not everywhere, as if there were a weight on you?
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Water (and other liquids) transfers pressure in all directions simultaneously and equally. Imagine you have a glass of water, and you put a tightly fitting piston into it and start pushing the water down. Obviously the side walls of the glass will just break at some point, and water will pour out. This is generally not what would happen if there was some solid object in the glass instead of water, that’s why liquids and solids are different. So in case of a submarine the walls of the submarine are the walls of the glass and the weight of all the water above it is you pushing down on the piston.
When you smash something against a table, the smashing is from you pushing down and the table pushing up.
The weight of the water above you is pushing down, and the water below you is pushing up, thus you crunch from both sides.
Edit: and all around. The water is being compressed everywhere so it’s also trying to squeeze into you from the side, if it can.
It’s not weight, it’s pressure. Think of water as really dense air. When the pressure inside the submarine is significantly less than the pressure outside, it compresses. You can replicate this at home by sucking the air out of a plastic bottle. Same principal. One thing submarines do to combat this, is slowly increase the internal air pressure so there is less of a differential. This has to be done slowly, to prevent it causing problems for the humans inside. Likewise when they come up to the surface, they need to undergo a decompression process. Just like when scuba-diving.
It’s a matter of pressure differences I think. Think about how a space ship is pressurized and how the air is trying to get out in every direction. It works in reverse when the pressure is greater outside the object than in. Technically yes it is pushing down on it, but liquids don’t have a ridged structure, so it’s going to try to fill that lower pressure area from all directions.
The universe loves entropy, so every system is being acted upon in order to try and equalize. I don’t have a degree on this topic though so I’m sure someone can explain it better.
It is exactly like having a weight on you. You focus on the weight on your shoulders but you feel it in your feet too, right? Same thing, just water is all around you not just right on top.
Water moves.
If you push a balloon full of air into water, the water around the balloon is trying to be lower than the air (which is what makes it feel like the balloon is being pushed out of the water). If it can’t do that, the shoving of the water pushes on whatever it can shove(the bottom and sides of the balloon) maybe deforming it, but definitely pushing.
When you’ve pushed the balloon all the way under the water, the water above it is slightly helping weigh down the balloon by pressing on the top, but there’s not enough friction and without your hand there, all the pressure from below and the sides would push the balloon through the water above because the water flows around it. The important thing to think about here is the fact that the water above and to the side is also pressing down on the water just to the side of the balloon.
As you get deeper and there is more water on the top, the weight of is is pushing on the balloon, but it’s also pushing on all the water around the balloon. That water really wants to go somewhere and everything around it is water also under the same pressure… except this balloon of air that does NOT have the same amount of push back, so the balloon gets pushed/squished.
When it comes to people/submarines, we are not balloons. We have bones or steel. This means we can take certain amounts of pushing without breaking. Unfortunately if the pushing gets too strong, the bones and steel break causing a very fast collapse/ implosion.
Hope this helps.
The pressure would just come from on top of you if the water was solid. But water isn’t solid…it will shear and distort continuously in response to pressure if it can. Among other things, this means the water wants to go any direction it can when squeezed from above. If you put something in it’s way, like the size of a submarine, it will happily push on that.
Water (and other liquids) basically have to transmit all pressure equally in all directions because, if they didn’t, they’d change shape until they were. Solids don’t work like this, solids can resist shear and compression (up to a point) without continuous deformation.
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