Release Message:  Stephen Hawking explores all the possibilities, warping the very fabric of time and space as he goes. From killing your grandfather to riding a black hole

Description:  The promise of time travel has long been one of the world's favorite scientific "what-ifs?" Hawking explores all the .possibilities, warping the very fabric of time and space as he goes. From killing your grandfather to riding a black hole, we learn the pitfalls and the prospects for a technology that could quite literally, change everything.