Derek Boyd, age 8, Of San Diego, Calif., for his question:

Why is lightning forked?

Lightning is a flash of electricity. It is set off in a storm cloud, and it cuts a path for itself through the damp, rainy air. This air tries to stop the piercing lightning. The flash has to move this way and that to cut a path through the storm cloud. This is why lightning dodges back and forth and Why sometimes the streak splits apart into forked branches.

Each flash of lightning is usually fast flashes, one after another. The first flash cuts the path through the damp air. The flashes that come along afterward follow the same path. But all the flashes, one after another, happen faster than fast, and the lightning is over in less than a second.