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I think I have a pretty decent handle on physics, I'm a Mech Eng, and have a big interest in space.

I read a lot of books, and watch a ton of documentaries, and just about every one of them says due to the very high pressure on Venus, it would crush you. Even NASA says so:

https://www.nasa.gov/audience/forstudents/5-8/features/F_The_Planet_Venus_5-8.html

My question is a simple why? Why wouldn't pressure just be on all sides equally, and the body being mostly made of (largely) incompressible water and bone not just sit there at 90 atm (ignoring the various other nasties)? What exactly would cause you to be crushed? I tech dive, I've been down to 4.5 atm, literally dozens of tons squeezing my body, and I'm fine because the fluids compress almost imperceptibly and push back. Does everyone just have this wrong even NASA? Or does it just made a good sound byte and they aren't aware of the finer points of pressure/force balance? This seems to me almost like a high school level blunder. Or am I missing something big?

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  • $\begingroup$ Is your only criterion for being crushed that the total physical volume which your body occupies is substantially reduced? $\endgroup$ – J. Murray May 5 '20 at 18:58
  • $\begingroup$ Your tech dive uses a pressure equilibration technique, does it not? Why does the air mixture in your bottles have to be non-toxic at high pressures do you think? Your machinery on your back allows your internal body pressure to equilibrate with the surroundings. If you have something like that on Venus, you might be fine, mechanically, at an internal body pressure of 92 bars. But as the answer points out, various other things can happen with your biochemistry exposed to 92 bars pressure. So no, you, a diver does not know better than NASA. $\endgroup$ – AtmosphericPrisonEscape May 5 '20 at 21:05
  • $\begingroup$ Equalization is for the eardrums. You hold your nose and blow causing it to pop your ears letting you equalize the tiny bit of air in your ears. The air has to be non toxic for oxygen toxicity and nitrogen narcosis. These are chemical issues, not physical. It needs to be high pressure not to equalize the body, but your lungs when breathing. Record free divers go down to 100m (10atm) on a breath hold. The pressure squeezes them and reduces their lung volume only as air spaces are compressible, bodies are not. I think squeeze would be more appropriate. Crush is when a piano falls on you. $\endgroup$ – Seadog May 6 '20 at 1:13
  • $\begingroup$ Your body is mostly water. and solid bones. Think back to your university thermodynamics courses. If you take a liter of water, and put it in a pressure tank at 100 bar, what does the volume become? About 0.9996 L. Explain specifically why (aside from the small volume of lungs) why the body would act differently. Don't just cop out with an appeal to authority. $\endgroup$ – Seadog May 6 '20 at 1:24
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Note that record deep dive exposed the diver to 33 bar (eqiuvalent to 660 tons of weight pushing on the body surface of ca 2 m²), yet the diver survived without harm. In my opinion, you are right that the trouble with high pressures are not "being crushed", but range as numerous "other nasties".

This would mean that the NASA page, as well as many other popular pages, use a wrong term. There are, however, pressure effects on the living tissues including possible denaturation of proteins, which deep-ocean fishes need to face, as noted on the scienceabc website. Yes, this page uses the unexplained word "crushed", too.

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  • $\begingroup$ Yeah that website doesn't really make sense to me. Going down to 33 atm with 330 tons is okie dokie, But on order of magnitude more, and that's when the problems start? I agree is it was only on front and back you'd be crushed, but since it's all around, you'd be little different than an air breathing whale diving several kilometers down.. $\endgroup$ – Seadog May 6 '20 at 1:34

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