It's 100 years since the publication of Einstein's great theory, and arguably one of the greatest scientific theories of all time. To mark the occasion, Brian Cox takes Robin Ince on a guided tour of General Relativity. With the help of some of the world's leading cosmologists, and a comedian or two, they explore the notions of space time, falling elevators, trampolines and bowling balls, and what was wrong with Newton's apple. It's a whistle stop tour of all you'll ever need to know about gravity and how a mathematical equation written 100 years ago predicted everything from black holes to the Big Bang, to our expanding universe, long before there was any proof that these extraordinary phenomena existed.