Science: Did Comets Kill the Dinosaurs?

In the evening around the Leuschner Observatory in Lafayette, Calif., a few enterprising rattlesnakes slither out to toast themselves on the asphalt parking lot, which retains the warmth of the sun long after the air has cooled. Inside, a 30-in. telescope begins a laborious computer-controlled search of the heavens, covering only a tiny patch of sky during the next six hours of darkness. And the following day, at the nearby University of California campus in Berkeley, Physicist Richard Muller, like a seer divining entrails, scrutinizes the new batch of video recordings from Lafayette. He seeks a sign of a dim star...