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Why doesn’t air pressure crush humans down into the ground?
I understand the internal pressure of our organs balance the air pressure. But air pressure is about 15 lbs/square inch. And the average surface area of humans is around 2600 square inches. Thus, the total pound force of air on humans is about 39,000 lbs. If you weren’t in air and a 39,000 lb object we’re on top you, you’d be crushed. Sure it’s spread out but only by a small surface area.
Let’s say there is a 39,000 lb weight above you whose underside takes the shape of your body. You’d still be crushed right?
Essentially the underside would wrap around your whole body.
But if you were to place a 20 ton weight on top yourself, (a weight that completely wraps around your body, excluding your underside), it would crush you. Let’s say this weight is water inside an invincible bag so it can take the shape of your body. Let’s say water is compressible and the volume of the bag were small. The pressure would be the same, about 15 psi. It would crush you.
Let’s say you’re lying down on the ground and a 40,000 lb weight is spread out on top you. This is pretty much the same situation. I suppose the weight would feel like half of 40,000 lbs. Or imagine someone who is twice the height of the average human and the weight is on top them. They’d be crushed in either of these scenarios.
- Anonymous1 month ago
Because humans have evolved over hundreds of thousands of years enduring ≈ 14.5 psi.
Recreational divers (nonpressurized suits) can reach 40 meters, which is approximately another 4 atmospheres, for a total of 5*14.5psi ≈ 72 psi. Even at that pressure, the risk is from other than crushing. Structurally, humans can survive deeper dives (greater pressure).
As for your water shroud example, it's not at all clear to me that, properly executed, it would crush you. I'd argue against it.
- az_lenderLv 71 month ago
Yes, and if you put a piece of cheese on the ground, why isn't that crushed too? Because (DUH) the internal pressure in the cheese balances the air pressure. The absolute pressure in a tire may be about 48 psi, which is 33 "psig" -- gauge pressure, which is what a tire gauge will show. Remove the external air pressure suddenly and a human body will explode. That's what would happen if you suddenly stepped out of doors from your space shuttle.
- MorningfoxLv 71 month ago
The air is all around you. It pushes up as well as down. The air also presses down on the dirt (or floor), which pushes right back.