Playlist: www.youtube.com In this four-part series, string theory pioneer Michio Kaku goes on an extraordinary exploration of the world in search of time. He discovers our sense of time passing and the clocks that drive our bodies. He reveals the forces of time that make and destroy us in a lifetime. He journeys to some of the Earth's most spectacular geological sites to look for clues to the extraordinary depths of time at a planetary level. Finally, he takes us on a cosmic journey in search of the beginning (and the end) of time itself. Part 2: Lifetime The most powerful effect of time on our lives is the way it limits us. Our knowledge of death is so embedded in our lives and spirituality that, were immortality possible, would we lose the sense that makes us human? www.bbc.co.uk