Carl Sagan hosts a thirteen-episode tour of the universe, from the surface of Mars to the edge of the observable cosmos, written with his wife and collaborator Ann Druyan. Sagan stands at the Library of Alexandria's ruins to talk about Eratosthenes measuring the Earth's circumference with a stick and a well, then moves to the Ship of the Imagination, a special-effects vessel that carries him past Saturn's rings and out to distant galaxies. Episodes cover the evolution of life from single cells, the history of astronomy from Babylon to Kepler, the workings of DNA, and the possibility of intelligent life elsewhere, tying each topic back to how humans came to know it. The Cosmic Calendar compresses the entire history of the universe into a single year, placing all of recorded human history in its last few seconds. Sagan's narration stays personal throughout, treating wonder and skepticism as the same instinct. The series became one of the most watched public television programs in the world and set the template every science documentary since has borrowed from.