Unafraid of the Dark

[2] The episode ends with Carl Sagan's (host of the original Cosmos) iconic speech on Earth as the "Pale Blue Dot.

"[3] Tyson begins the episode by noting how the destruction of the Library of Alexandria lost much of humanity's knowledge to that point.

Tyson then proceeds to describe the discovery of cosmic rays by Victor Hess through high-altitude balloon trips, where radiation increased the farther one was from the surface.

Swiss Astronomer Fritz Zwicky, in studying supernovae, postulated that these cosmic rays originated from these events instead of electromagnetic radiation.

Tyson concludes the series by emphasizing Sagan's message on the human condition in the vastness of the cosmos, and to encourage viewers to continue to explore and discover what else the universe has to offer.