Turn the knob to make the umbrella spin. Watch the hole cut into the edge and you'll see that the umbrella is spinning faster than the waves traveling through it. A wave is essentially a traveling disturbance-a pulse of energy that moves through something. Here, the disturbance is caused by air trapped in the umbrella's folds. Over the ocean, moving air sets also sets waves in motion. A wind-generated wave pulses through the water, but doesn't actually drag the water along with it. If it did, all the water in all the oceans would have been delivered up onto the shore long ago.
audio tour for circular wave umbrella...
© The Exploratorium, 1996