As we, and Stephen Hawking, stare into the night sky at the countless billions of stars, the question arises about the likelihood of aliens. Are they out there?
Cosmologist Stephen Hawking explores the world's favourite scientific 'what if?' Is it possible to travel back and forth within the fourth dimension, time?
Professor Stephen Hawking traces the life span of the universe from the Big Bang to the ultimate cosmic implosion, all mapped in stunning CGI.