Why doesn't atmospheric pressure crush us?

[anonymous99]

H

 

[anorlunda]

So why do you think a balloon does not explode or collapse?

 

[anonymous99]

So why do you think a balloon does not explode or collapse?

Hmm. Maybe the fact that it's hollow would change the internal stresses it develops? Not sure.

 

[anorlunda]

Hmm. Maybe the fact that it's hollow would change the internal stresses it develops? Not sure.

Our bodies are soft and partially hollow. Continue thinking about the balloon, and I bet that you'll answer your own question.

 

[OCR]

Our bodies are soft and partially hollow.

And not all that attractive to some. . . .

.

 

[russ_watters]

If I applied 1 MPA to both ends of the cube, I would still expect the bar to get crushed despite the forces balancing because of the massive internal stresses it would develop.

That's true, but a cube has 6 sides, not 2 and that matters here.

Let's say the cube is made of weak plastic full of water. If you apply a lot of force to just two sides, you will indeed squish it.

 

[ZapperZ]

Summary:: The usual explanation I read online is that the internal pressure of our body equals the external atmospheric pressure so the forces cancel out. But say we had a solid bar. If I applied 1 MPA to both ends of the cube, I would still expect the bar to get crushed despite the forces balancing because of the massive internal stresses it would develop. So when there's 1 bar of pressure acting on us both from the inside and outside, why doesn't the same happen?

H

Isn't this more of a BIOLOGY question? You don't appear to realize that our cells have internal pressure that prevent them from collapsing from atmospheric pressure, and that our blood veins have internal pressure (which many of us older folks are trying to get as low as possible, with the help of medication), etc... etc.

Zz.

 

[DaveC426913]

The solution can also be understood by looking at it the other way around.

Start with a puddle of 80kg of water. Does it get crushed? No. It's in equilibrium.
Encase the 80kg of water in a flexible membrane. Does it get crushed now? No.
etc.

The contents of human body were always at one atmosphere. Encasing it in a membrane and standing it upright changes nothing.

 

[hutchphd]

Our bodies are not balloons. They are water balloons. And water is nearly incompressible. Put a water balloon in a pressure chamber and increase the pressure...nothing will happen. Notice this does not hold if we decrease pressure because the water in the balloon will outgas (this causes the bends) or boil (causing a mess in the air lock of the spacecraft )
Yes we do have lungs (and GI tract) , but they are sort of "outside"of the sealed part of corporate us,

 

[Lnewqban]

This fragile creature happily lives under a pressure 120 times greater than the atmospheric pressure.

 

[sophiecentaur]

our cells have internal pressure

. . . .and so has any other object that doesn't have a totally rigid envelope (e.g. a submarine). Our cells were formed under pressure, from water and chemicals that were also under pressure and so it's always there and there will be no 'damage'. Any gases inside or outside the envelope may be absorbed or released is there is a pressure change. Under very high pressures, the forced solution of some gases (Nitrogen, for instance) can damage the body's chemistry (Nitrogen narcosis, for instance) and when pressure is reduced, bubbles can be formed as gases come out of solution, causing damage sometimes (decompression sickness or the bends, for instance). The system remains stable until while (!) pressure (or temperature) stays within limits.

 

[Mister T]

We are crushed by it, and the way we feel is the way it feels to be held in place by the atmosphere. Without it we would vaporize. Violently.

 

[jbriggs444]

We are crushed by it, and the way we feel is the way it feels to be held in place by the atmosphere. Without it we would vaporize. Violently.

We do not have enough energy to vaporize violently. We would outgas, chill and eventually dessicate.

 

[sophiecentaur]

We do not have enough energy to vaporize violently. We would outgas, chill and eventually dessicate.

That’s true (I remember a good sci-fi adventure where the crew successfully breathed vacuum during an in space transfer. Not evidence of course) but there will be / could well be gases trapped in voids which would expand and give problems. Divers, coming to the surface from deep water need to breathe out or breathe naturally constantly. Holding your breath can result in a lungful of trapped air that won’t vent. Nasty.

 

[kuruman]

You can model cells as water balloons, their skin being the bi-lipid membrane holding mostly water. See here what happens to water balloons in a vacuum.