The human body works best at atmospheric pressure. This is because the inside of the body is kept at a similar pressure, mostly thanks to the blood pressure that your heart maintains by pumping. (Actually, doctors measure your blood pressure in terms of how much higher it is than atmospheric pressure--usually about 120 mm Hg.)

Atmospheric pressure is especially important for keeping the right amount of oxygen in your blood. At lower pressures, your blood might not dissolve enough oxygen, while at high pressures, your blood might have too much. Mountain climbers (who often travel to high places that have lower pressure) and scuba divers (who spend time at high pressures underwater) both have to be aware of how different pressures will affect their bodies.

This question is really interesting because it seems so counter intuitive. There is a kilogram of air pushing down on every square centimeter of Earth, so how come we aren’t crushed. There are a few things that protect us, and the first is that air isn’t just pushing down on us from one direction. Air is all around us and pushes on us from all angles. While it may not be perfectly even, all of these different directional pressures keep us from being crushed flat. If you’re really thinking you’re probably now wondering why we aren’t then crushed to a small ball since air pushes from all angles, and that is because we have air inside of us also. The air inside of us exerts an opposite pressure outward from us, balancing out the atmospheric pressure. Because of this balancing act, we get to stay upright and inflated rather than crushed by the weight of our atmosphere. Thank you for the question!

Thank you for the great question.

I’m at sea level right now in Santa Barbara, so about 60 miles of air separates me from outer space. It turns out that the column of air that’s above us when we are outside weighs about 2000 pounds. That’s like having a small car above you!

So why doesn’t all this weight crush us? Well for one, the air molecules above you (oxygen, nitrogen, and other gases) are all moving around in random directions. This means that the force exerted by the air is distributed pretty much evenly – some force is pushing up, some force is pushing down. Because of this, the pressure on the surface is reduced.

A second reason is that life on Earth has evolved to account for the atmosphere’s pressure. The pressure inside of our body (in places like our ears, stomach, and lungs) is kept equivalent to the air pressure outside of us. This prevents us from getting crushed!

Bonus information: Life at the bottom of the sea encounters a similar problem, but with pressures up to a 1000 times more crushing than at the beach. Animals at these extreme depths are again adapted to their environment, for instance they are often small and have minimal skeletal structure. In fact, studying these animals is very difficult because they do not survive the relative lack of pressure should we bring them up to the surface.

So, the atmospheric pressure is pretty high. The weight of air above you is about the equivalent of the weight of a small car. However, all of the stuff that makes us up such as blood, bones, and tissues are also exerting a lot of pressure. In fact, our body exerts the same pressure as the atmosphere so the forces cancel out! That’s why you don’t feel a difference. An interesting animal that has to deal with a lot of pressure is the deep sea angler fish which lives at depths of over 3000 feet. So how does this fish survive a pressure of 90 times atmospheric pressure? Well, its body exerts the same pressure, just as in the case of humans. An angler fish could not survive at atmospheric pressure since it’s body is at around 90 times atmospheric pressure so the forces wouldn’t balance. We do perceive some degree of atmospheric pressure changes such as when you fly in an airplane and your ears “pop” as you take-off. The pop is due to the decreased air pressure as we ascend into the sky as your ear tries to equalize the internal and external pressure.