Jim Al-Khalili's new two-part physics documentary Light and Dark had a scope that seemed just a little ambitious for two hours of television. "Light and Dark is essentially the story of everything we know and everything we don't know about our universe." So that's pretty much everything, then, Jim? Yet rather than the confusion of ideas you might expect, Al-Khalili's documentary illuminated a scientific story with its own, rather beautiful, internal logic.
We began with Euclid's 3rd-century BC discovery that light moves in straight lines, and continued chronologically, through Galileo's paradigm-shifting invention of the telescope and Newton's experiments with prisms. In the past 30 years, said Al-Khalili, we have looked out into the Universe and seen as far as it's possible to see, in both space and time.
And there we might have reached a comfortable conclusion, were it not for part two next week and this intriguing tease: "The vast majority of the cosmos can't be seen at all... and by exploring that darkness, we've come to realise that we've seen virtually nothing." That's the trouble with these physics documentaries: the more you learn, the less you understand.