In the last episode of Professor Brian Cox’s epic journey across the universe, he travels from the fossils of the Burgess Shale to the sands of the oldest desert in the world to show how light holds the key to our understanding of the whole universe, including our own deepest origins.

To understand how light holds the key to the story of the universe, you first have to understand its peculiar properties. Brian considers how the properties of light that lend colour to desert sands and the spectrum of a rainbow can lead to profound insights into the history and evolution of our universe.

Finally, with some of the world’s most fascinating fossils in hand, Brian considers how but for an apparently obscure moment in the early evolutionary history of life, all the secrets of light may have remained hidden. Because although the universe is bathed in light that carries extraordinary amounts of information about where we come from, it would have remained invisible without a crucial evolutionary development that allowed us to see. Only because of that development can we now observe, capture and contemplate the incredible wonders of the universe that we inhabit.