Sagan was a science communicator, which meant he taught people about science. He felt like the general public was losing interest in science, so he wrote many books and appeared on television to make it popular again. He mostly talked about planetary science and topics related to space. One of his most famous works includes. "Cosmos: A Personal Voyage. Cosmos" was a television series about many different scientific topics, which Sagan co-wrote and narrated. It made him very famous outside the world of science. 