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Experts still aren't sure what triggers lightning, but they suspect cosmic rays from outer space.
Topic: Planet EarthPlanet EarthBrand: NOVA ScienceNOWNOVA ScienceNOW

Program Description

(This video is no longer available for streaming.) What causes lightning? The mystery has confounded scientists for centuries, but researchers like Joe Dwyer are hot on the pursuit of an answer. At the International Center for Lightning Research and Testing in Florida, Dwyer and colleagues use rockets to lure down lightning bolts, the better to study them. And to test a hypothesis—that they're triggered by cosmic rays from outer space.