He spent most of his career as a professor of astronomy at Cornell University, where he directed the Laboratory for Planetary Studies. Sagan was a popular public advocate of skeptical scientific inquiry and the scientific method he pioneered the field of exobiology and promoted the search for extra-terrestrial intelligent life ( SETI).

His papers, comprising 595,000 items, are archived in the Library of Congress. Sagan also wrote a science-fiction novel, published in 1985, called Contact, which became the basis for a 1997 film of the same name. A book, also called Cosmos, was published to accompany the series. He also co-wrote and narrated the award-winning 1980 television series Cosmos: A Personal Voyage, which became the most widely watched series in the history of American public television: Cosmos has been seen by at least 500 million people in 60 countries. He wrote many popular science books, such as The Dragons of Eden, Broca's Brain, and Pale Blue Dot. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books. Initially an assistant professor at Harvard, Sagan later moved to Cornell, where he spent most of his career.

He argued in favor of the hypothesis, which has since been accepted, that the high surface temperatures of Venus are the result of the greenhouse effect. He assembled the first physical messages sent into space, the Pioneer plaque and the Voyager Golden Record, which were universal messages that could potentially be understood by any extraterrestrial intelligence that might find them. His best known scientific contribution is his research on the possibility of extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation. Carl Edward Sagan ( / ˈ s eɪ ɡ ən/ SAY-gən November 9, 1934 – December 20, 1996) was an American astronomer, planetary scientist, cosmologist, astrophysicist, astrobiologist, science communicator, author, and professor.

Cosmos by Carl Sagan