Cosmologist Sean Carroll attacks — in an entertaining and thought-provoking tour through the nature of time and the universe — a deceptively simple question: Why does time exist at all? The potential answers point to a surprising view of the nature of the universe, and our place in it. (Filmed at TEDxCaltech.)

A physicist, cosmologist and gifted science communicator, Sean Carroll is asking himself — and asking us to consider — questions that get at the fundamental nature of the universe. Full bio »