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Carl Sagan (November 9, 1934 – December 20, 1996) was a popular scientist, skeptic, astronomer, and media personality. He is perhaps best known for the PBS television series, Cosmos. Sagan saw no reason to believe in a personal God or anything beyond physical reality and the laws that govern the universe. He did not consider himself an atheist because he could not disprove god.
Sagan feared the reason why humans have not found evidence for extraterrestrial civilizations could be that technologically advanced extraterrestrial communities destroyed themselves. He was concerned that humanity should not destroy itself.
Sagan was founder of The Planetary Society.