What if our creations turn against us? The idea of creating life has fascinated society since the earliest days of science fiction. From HAL in 2001: A Space Odyssey to the Cylons of the reimagined Battlestar Galactica and the world of The Matrix, this is a journey that asks - what does it mean to be human?

This Time Travel Special journeys from H. G. Wells The Time Machine through ideas like The Grandfather Paradox and The Butterfly Effect, to the professional time traveler that is the ever popular Doctor Who. Steven Moffat, David Tennant, Karen Gillan, and Neil Gaiman offer a unique perspective on the Doctor. Furthermore, Edward James Olmos reveals the hidden meaning of the language he created for the vision of the future that is Blade Runner, while Bob Gale and Christopher Lloyd take us behind the scenes of Back to the Future.