Having explored the wonders of the solar system, Professor Brian Cox steps boldly on to an even bigger stage - the universe. In this episode, Brian seeks to understand the nature of time and its role in creating both the universe and ourselves. From an extraordinary calendar built into the landscape of Peru to the beaches of Costa Rica, Brian explores the cycles of time which define our experience of life on Earth. But even the most epic cycles of life can't begin to compare to the vast expanse of cosmic time. For instance, just as the Earth orbits the Sun, the solar system orbits the entire Milky Way galaxy. This orbit takes a staggering 250 million years to complete. Ultimately, Brian discovers that time is not characterised by repetition but by irreversible change. From the relentless march of a glacier, to the decay of an old mining town, the ravaging effects of time are all around us.