Humans once thought the stars were campfires in the sky and the Milky Way "the backbone of night."
In this fascinating segment Dr. Sagan takes us back to ancient Greece, when the basic question "what are the stars?" was first asked. He visits the Brooklyn elementary school of his childhood, where this same question is still on students' minds.
click here to see where to watch or .
Ready to Watch Cosmos, Season 1, Episode 7?