Before Carl Sagan became the poet of the cosmos and the voice of scientific wonder, he worked on Project A119 — a classified Cold War plan to detonate a nuclear weapon on the surface of the Moon as a show of American military dominance. The man who would later teach billions to appreciate the "pale blue dot" once helped design a plan to nuke our nearest celestial neighbor.

This episode traces Sagan from his Brooklyn childhood through the classified lunar project, the Viking Mars missions, the creation of Cosmos, the nuclear winter hypothesis, and the "pale blue dot" photograph that became his most enduring legacy.

• Sagan's Brooklyn childhood and his early involvement in the classified Project A119 moon-nuke plan
• The Viking missions to Mars, the search for extraterrestrial life, and the Voyager Golden Record
• Cosmos  ...