Why is our time limited? And does it have to be? Could our age-old dream of immortality ever be possible? In episode two, Michio Kaku explores these questions and meets some of the key people involved in the cutting-edge research into ageing. He travels to the amazing Methuselah tree, which is almost 5000 years old and still producing new pine cones. He discovers that time does get faster as you get older and, under hypnosis, he goes in search of his lost time, stored as memories. But it only proves that lost time is really gone forever.

• Michio Kaku