system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Air weighs 14 pounds per square inch, yet we don't feel it crushing us. The notion that internal pressure somehow acts as a counterbalance just seems to mean that we're being crushed in both directions. Shouldn't we feel this massive weight on us?
gpt
If it helps, we're already "crushed." Our species evolved on this planet; we evolved "resistance to crushing of 14.7 psi_a" as part of the process, because otherwise our ancestors would've died.

With regard to the physics, most of our body is water, which is relatively incompressible, so that's not a hazard. What the barometric/atmosphere pressure *does* push on is the pockets of air in our lungs. Coincidentally, those pockets of air are *also* at about 14.7 psi_a (except we're actively breathing in/out), so the net force of the atmosphere on our lungs is basically zero. This means that there's no crushing at all; both sides being pushed the same means no net force to collapse our lungs. And our bodily structures, as mentioned above, evolved to survive that pressure, so they won't be damaged. Hence, we are crushed into a ball by outside pressure because we have internal pressure to resist it, and our individual cells/parts don't get crushed because they are individually strong enough to resist this pressure.