NOVA scienceNOW

Lightning

Clip | 9m 8s  | Video has closed captioning.

Experts aren't sure what triggers lightning, but suspect cosmic rays from outer space.

Aired: 10/01/05

Rating: NR

Problems Playing Video? | Closed Captioning

Funding for NOVA ScienceNOW is provided by the National Science Foundation and the Alfred P. Sloan Foundation.