Unafraid of the Dark

Today on Far Future Horizons we present "Unafraid of the Dark” the thirteenth and last episode of the Cosmos: A Spacetime Odyssey hosted by Neil deGrasse Tyson.

The installment explores the mysteries of dark energy and dark matter, as well as the contributions and theories of Swiss astronomer Fritz Zwicky.

Great Library of Alexandria

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

Victor Hess

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.

Fritz Zwicky

Swiss Astronomer Fritz Zwicky, in studying supernovae, postulated that these cosmic rays originated from these events instead of electromagnetic radiation. Zwicky would continue to study supernovae, and by looking at standard candles that they emitted, estimated the movement of the galaxies in the universe. His calculations suggested that there must be more mass in the universe than those apparent in the observable galaxies, and called this dark matter. Initially forgotten, Zwicky's theory was confirmed by the work of Vera Rubin, who observed that the rotation of stars at the edges of observable galaxies did not follow expected rotational behavior without considering dark matter. This further led to the proposal of dark energy as a viable theory to account for the universe's increasing rate of expansion.

Vera Rubin

Tyson then describes the interstellar travel, using the two Voyager probes. Besides the abilities to identify several features on the planets of the solar system, Voyager I was able to recently demonstrate the existence of the Sun's variable heliosphere which help buffer the Solar System from interstellar winds. 

Voyager Golden Record

Tyson describes Carl Sagan's role in the Voyager program, including creating the Voyager Golden Record to encapsulate humanity and Earth's position in the universe, and convincing the program directors to have Voyager I to take a picture of Earth from beyond the orbit of Neptune, creating the image of the Pale Blue Dot.

Carl Sagan

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.

The finale reveals a recording of life on Earth - the final message on the golden record of the space probe, Voyager. The episode ends with Carl Sagan's (host of the original Cosmos) iconic speech on Earth as the "Pale Blue Dot."

If you want to learn more about the scientists mentioned in this and other episodes in the series here is a very good reference page ~ The Scientists of Cosmos: A Spacetime Odyssey.

This episode of Cosmos: A Spacetime Odyssey can be purchased from Amazon Instant video.

Cosmos: A Spacetime Odyssey ~ Unafraid of the Dark
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