The eighth episode of Cosmos, “Journeys in Space and Time,” returns to the style of earlier episodes with a specific topical focus: space and time (rather obviously). It’s an information-heavy installment that takes place for the most part in Tuscany, where both Leonardo Da Vinci and a young Albert Einstein did their intellectual work. The episode begins by discussing the constellations again and uses that as a springboard to discuss issues of distance, perception, and the speed of light—all considering the stars and our relationship to them. Sagan illustrates the connections between space and time by diving into a discussion of travel to the stars and the problems posed by the general theory of relativity (time dilation, etc); that leads into a set of thought experiments on time travel and speed-of-light travel. It’s also, as might be clear by now, one of the more science-fiction-friendly episodes.
[Onward.]