New Ideas Are 'Guilty Until Proved Innocent'

 In June 1980, Luis and Walter Alvarez and their associates startled the scientific community by announcing that dinosaurs had not died out be-cause of gradually changing environmental conditions 50 million years ago. Instead, they said, mass extinctions took place when an extraterrestrial body slammed into the Earth, throwing a pall of dust and ash over the planet that lasted for years. Initially skeptical, paleontologist David M. Raup helped analyze data on marine fossil extinction that c

David Raup
Oct 19, 1986

 In June 1980, Luis and Walter Alvarez and their associates startled the scientific community by announcing that dinosaurs had not died out be-cause of gradually changing environmental conditions 50 million years ago. Instead, they said, mass extinctions took place when an extraterrestrial body slammed into the Earth, throwing a pall of dust and ash over the planet that lasted for years. Initially skeptical, paleontologist David M. Raup helped analyze data on marine fossil extinction that changed his mind, eventually arguing for a 26 million-year cycle of extinctions that probably were tied to solar system or galactic forces. Others continued to refine the theory, postulating the return every 26 million years of Nemesis, the hypothetical small companion star of our Sun that sends comets from the Sun's Oort cloud hurtling toward our planet, altering its ecology. Raup's new book "The Nemesis Affair: A Story of the Death of Dinosaurs and...