The spread of nuclear weapons to unstable third world countries means that despite the dramatic improvement in US/Soviet relations, we are living in a time of unprecedented danger of nuclear war.In 1982, Professors Sagan and Turco made known their discovery of the concept 'nuclear winter', a widespread cold and dark, resulting in agricultural collapse and world famine, that would be generated in even a 'small' nuclear war. It was a landmark discovery that revealed in the starkest terms how vulnerable our civilization is to the long-term environmental effects of nuclear war.Carl Sagan, Pulitzer prize-winning science writer, and Richard Turco, tell the personal story of their findings, and how, despite the much-heralded thawing of the Cold War, there are dangerous inadequacies in nuclear policy and doctrine that need to be addressed.Introductory music from the original score for COSMOS: A SpaceTime Odyssey composed by Alan Silvestri, used with permission from Cosmos Studios, Inc. and Chappers Music. All rights reserved. Special thanks to Fuzzy Planets, Inc.