Sagan, Carl Edward

▪ 1997

      U.S. astronomer and exobiologist (b. Nov. 9, 1934, New York, N.Y.—d. Dec. 20, 1996, Seattle, Wash.), studied such diverse aspects of the solar system as the conditions of planetary surfaces and atmospheres and the possibility of extraterrestrial life; he stimulated popular interest in these subjects through his enthusiastic writings, lectures, and televised presentations. An avid reader of science fiction as a boy, Sagan developed an interest in astronomy early in life. He studied at the University of Chicago, where he earned four degrees (A.B., 1954; B.S., 1955; M.S., physics, 1956; and Ph.D., astronomy and astrophysics, 1960). After graduation he lectured at the University of California, Berkeley, and at Harvard University before moving to Cornell University, Ithaca, N.Y., in 1968. There he became director of the Laboratory for Planetary Studies and (1970) professor (from 1976 David Duncan professor) of astronomy and space sciences. Some of Sagan's earliest theories about planetary conditions concerned Mars and Venus, predictions that were confirmed by unmanned space probes during the late 1960s and '70s. Sagan was involved in designing experiments to be carried out on a number of these planetary missions. Intrigued since his graduate-school days by the question of the way that life on Earth originated, Sagan conducted experiments showing how various organic molecules could be produced from a simulated gaseous atmosphere of primitive Earth. Sagan's willingness to speculate about the possibility of life elsewhere in the universe helped to gain credibility for the search for extraterrestrial life. He also perceived the threat that the nuclear arms race posed to humanity, and in 1983 he coauthored an article warning about the possible consequences of a nuclear exchange. Although scenarios, such as an atmospheric cooling dubbed "nuclear winter," predicted by the authors were shown to be unlikely, the article spurred discussion of this serious topic. Sagan was a prolific writer of popular science and won a Pulitzer Prize in 1978 for The Dragons of Eden: Speculations on the Evolution of Human Intelligence. His passion for science was contagious, and his ability to inspire others to share that interest became evident when the TV series "Cosmos," a program he narrated and helped to write, began airing in 1980 and became an immediate success.

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