Cosmos: A Spacetime Odyssey

Episode 04 - A Sky Full of Ghosts. Tyson begins the episode by explaining the nature of the speed of light and how much of what is seen of the observable universe is from light emanated from billions of years in the past. Tyson further explains how modern astronomy has used such analyses via deep time to identify the Big Bang event and the age of the universe.

Tyson proceeds to describe how the work of Isaac Newton, William Herschel, Michael Faraday, and James Clerk Maxwell contributed to understanding the nature of electromagnetic waves and gravitational force, and how this work led towards Albert Einstein's Theory of Relativity, that the speed of light is a fundamental constant of the universe and gravity can be seen as distortion of the fabric of space-time. Tyson describes the concept of dark stars as postulated by John Michell which are not visible but detectable by tracking other stars trapped within their gravity wells, an idea Herschel used to discover binary stars.

Tyson then describes the nature of black holes, their enormous gravitational forces that can even capture light, and their discovery via X-ray sources such as Cygnus X-1. Tyson uses the Ship of Imagination to provide a postulate of the warping of spacetime and time dilation as one enters the event horizon of the black hole, and the possibility that these may lead to other points within our universe or others, or even time travel.

Episode 04 - A Sky Full of Ghosts

Go to Cosmos: A Spacetime Odyssey Home or watch other episodes:

Episode 01 - Standing Up in the Milky Way
Episode 02 - Some of the Things that Molecules Do
Episode 03 - When Knowledge Conquered Fear
Episode 04 - A Sky Full of Ghosts
Episode 05 - Hiding in the Light
Episode 06 - Deeper, Deeper, Deeper Still
Episode 07 - The Clean Room
Episode 08 - Sisters of the Sun
Episode 09 - The Lost Worlds of Planet Earth
Episode 10 - The Electric Boy
Episode 11- The Immortals
Episode 12 - The World Set Free
Episode 13 - Unafraid of the Dark