In the final episode Professor Cox travels to Iceland to witness the delicate splendour of a moonbow, the band of colours unleashed when moonbeams are cracked open by the spray of a waterfall.
Brian visits the site of an enormous outpouring of lava to explain why hot things glow red, and how the different colours of light energy from the Sun transform the plains of the Serengeti in Tanzania, and drive the great migration of humpback whales to the Caribbean each year.
The way light interacts with the stuff of our planet paints it in myriad colours, but understanding how points the way to hunting other Earth-like planets far out in the Cosmos.