In the exhibit Balancing Ball, a beach ball sits suspended above an air compressor shooting air through a traffic cone.

What’s going on?

When the ball is suspended in the air stream, the air flowing upward hits the bottom of the ball and slows down, generating a region of higher pressure. The high-pressure region of air under the ball holds the ball up against the pull of gravity. When you pull the ball partially out of the air stream, air curves around the ball and flows outward. This outward-flowing air exerts an inward force on the ball, in keeping with Newton’s Third Law: For every action, there is an equal and opposite reaction. Similarly, the downward flow of air beneath a helicopter exerts an upward force on the blades of the helicopter.