Eddie Lavara, age 12, of Sarasota, Florida, for his question:

Where does the water go at low tide?

On a local beach, the disappearance of all that water at low tide seems impossible. Obviously it must go somewhere. Actually, the level of the water is changed by the moon's gravity, as the earth rotates on its axis. As the moon passes overhead, it heaves up a great hump of water over about one quarter of the globe. This leaves a low tidal level on either side    and causes a twin high tide level on the opposite side of the globe.

As the earth rotates, the moon passes overhead around the globe. As it goes, it raises and lowers the four tidal levels. Every 24 hours or so, a high tide and a low tide, followed by another high tide and low tide chase each other around the globe. When the tidal level is low on your favorite beach, there are humps of high tidal water ahead and behind. The extra water is on either side, a quarter of the way around the globe.