Question

Atmospheric pressure is supposed to be very large. Then why is it that we, along with everything else on the earth, do not get crushed under this tremendous pressure?

Asked by: Chinu

 Answer

You are correct about the fact that atmospheric pressure is very large. Indeed, some would say that it is very, very, very large! I guess you know that at sea level that pressure is 14 pounds for every square inch of our body surface area. I don't know about you, but, for me that is a very, very large area!

We are not crushed by this tremendous pressure because we grew up in it. I mean from the very beginning of life on Earth, life grew up in this huge pressure. If we are being pressed inward by this very large pressure we must be pushing out with an equal pressure. This is how all life on earth evolved. In fact, we push out all the time. I am sure you have seen movies in which some characters are pushed out into space. If the movie is done correctly you will see the persons body continue to push outward without anything pushing back. Thus the person explodes! The movie 'Total Recall' has some especially good shots of this happening on Mars, where the pressure of the atmosphere is much less than Earth's.

Now, if you want to see something get crushed under the pressure of a fluid you can go deep into the ocean. Water pressure is much greater than air pressure. Humans can go only a couple of hundred feet, with training, deep before the pressure of the water is more than our bodies can bear. But, you know that there are creatures that can live at great depths without getting crushed; and now you know the reason why.

Answered by: Tom Young, M.S., Science Teacher, Whitehouse High School, Texas

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