We live at the bottom of an ocean of air – we call it the
ATMOSPHERE. It presses on us from all directions, and
it's only the pressure of our blood and the air in our bodies that stops parts of us from being
squashed. If we think of the air in the atmosphere to be like a liquid then our ocean of air
would be about 8000 m deep! Obviously if we lived at the bottom of an ocean of 8000 m of
water the pressure would be enormous so the density of air must be much lower than that of
water.
The pressure of the air at sea level is about 100 000 N/m2 (Pa).
This is like having two quite heavy people standing on your head.
You can show the
effects of air pressure either by trying to move something through the air or by looking at the
effect of air pressure on an object containing no air.