In the early 1900s, Albert Einstein developed an idea - called Relativity - that changed our understanding of reality. It explained how both space and time were flexible - and how the Universe was made of a four-dimensional fabric called space-time. This single idea gave us a new way to understand the force of gravity, explained how the stars were born and introduced us to the concept of the big bang. And, in the hands of Stephen Hawking, it allowed us to understand the most extreme monsters in the Universe - black holes. This two-part BBC documentary explores how two of the most famous scientists of the 20th Century transformed our understanding of the Universe - thus changing the world.

Physicists Leonard and Sheldon find their nerd-centric social circle with pals Howard and Raj expanding when aspiring actress Penny moves in next door.

This series explores the lives and work of noted modern-day astronomers, taking the viewer into the farthest reaches of outer space in search of black holes, quasars, dark matter, gravity waves, stars and evidence of planets outside our solar system. Intriguing celestial phenomena are examined from the perspectives of the experts: the men and women that are uncovering the secrets of the cosmos. Further, the series focuses not only on professional achievements, but on the scientists' personal lives as well.