Who Speaks for Earth?

Through the use of special effects we retrace the 15-billion-year journey from the big bang to the present. We also hear the tragic story of the martyrdom of Hypatia, the woman scientist of ancient Alexandria.
This is the famous episode on nuclear war in which Dr. Sagan argues that our responsibility for survival is owed not just to ourselves, but also to the cosmos, ancient and vast, from which we spring.