Eric Cloud, age 11, of Jefferson, South Dakota, for his question:

How does lightning get started?

Lightning is electricity and electricity is electrons in motion. These tiny negative particles are attached to the positive nuclei of gaseous air molecules. In the frantic turmoil of a thunderhead, air molecules are bashed and smashed around from all directions. Countless electrons get brushed off and swept away. Each electron that departs takes with it one charge of negative electricity. This leaves an air molecule with one extra positive charge.

As more electrons are swept away, opposite charges build up in different parts of the cloud. And opposite electrical charges attract each other much more so than opposite magnetic poles. When the tension reaches a critical point, the opposite charges in the cloud are discharged in flashes of lightning. Meantime, if the storm is a wild one, its winds are wiping off more electrons and creating more electrical charges.