Dave Aplington, age 11, of Peoria, ill., for his question:

How high up is the lightning?

Summer is the season when cumulonimbus clouds build up thunderstorms over our heads. Before the storm, the sky is usually bedecked with flocks of fluffy white cumulus clouds floating perhaps three miles above the earth. Then they begin to pile up into a misty mountain of foggy white and gray. The misty mountain becomes a thunderhead or cumulonimbus cloud, growing darker with each passing moment.

The top of the storm cloud reaches up to six or seven miles above the ground. It is a turbulent battleground of tremendous energy, and this energy generates the flashing lightning. The flash may start near the top of the cloud, seven miles above the ground. It may streak across lawer levels in the cloud, or it may begin six or seven miles up and reach right down to strike the ground.