In September 2001, Victor Pasko spent 20 nights on a roof in Puerto Rico, waiting for storms powerful enough to spawn the mysterious middle-atmosphere electrical events known as red sprites and blue jets. Pasko, a Penn State electrical engineer, sat on a wooden hatch cover on the flat concrete roof of a laboratory on the grounds of Arecibo Observatory. In front of him, his laptop projected a stream of images from a tripod-mounted low-light video camera, also on the roof.