Carl Sagan was an American astronomer, cosmologist, and science communicator, best known for his ability to make complex scientific ideas accessible to the public. He played a key role in popularizing science through his books, such as Cosmos, and the television series of the same name, which inspired millions to explore the universe and appreciate the wonders of science. Sagan was also a passionate advocate for the search for extraterrestrial life and contributed to various space missions, including Voyager. His work emphasized the importance of critical thinking and skepticism, encouraging people to question the world around them and seek evidence-based answers.