A Swiss mathematician named Daniel Bernoulli, who lived from 1700 to 1782, discovered that when flowing air changed its speed, its pressure also changed.
The concept is that there are two types of pressure: static (stationary) pressure, and dynamic (moving) pressure. Bernoulli's principle tells us that air that is moving at high speed has lower pressure than still air. The air moves around the ball to create a pocket around the ball of low pressure air. When the ball moves to the side of the pocket, it will be pushed back in by the higher pressure air. And the upward force from the air stream keeps the ball aloft. It's quite a cool effect!

An airplane wing is designed based upon Bernoulli's discovery. This tells us that when air is still, it has more pressure than air in motion. If air must travel over an obstacle, as motion increases, the air pressure decreases. In motion, the pressure or exertion of that air becomes less. The faster the air moves over a surface, the less pressure it has on the object.

THE AIR RUSHING OVER THE TOP OF THE WINGS ALLOWS THE AIR UNDERNEATH TO "LIFT" OR PUSH AN AIRPLANE INTO THE SKY! Pretty neat huh!

This experiment and other similar air pressure experiments may be found at the “Back of Poster” area of the AIA resources page, or go directly to a more extensive experiment at: http://www.nasm.si.edu/exhibitions/gal109/LESSONS/TEXT/TEASERS.HTM