Continuing his exploration of the Cosmos, Carl Sagan takes us today on an exploration of interstellar and time travel, the likes of which no human being has ever actually experienced so far.
In order to explain this idea, and after giving a quick lesson on constellations, he goes to the Tuscany area of Italy (home of Leonardo da Vinci and childhood residence of Albert Einstein), and conducts some thought experiments in order to illustrate the strange consequences and apparent paradoxes of Einstein's theory of special relativity.
With a basic understanding of the physics involved, Sagan then turns his attention to the possibility of future travel to other stars and galaxies. Although this is a sound theoretical possibility, the engineering required to make this a reality is still nowhere in the foreseeable future yet, but scientists are already coming up with ideas about how to get started...
Check out the rest of Carl Sagan's Cosmos.