Gravitational Waves: the moment of discovery

In what has been called the most important breakthrough in more than a century, scientists in the United States say they've successfully detected gravitational waves. Dr Siong Heng of Glasgow University is a UK-based researcher who worked on the discovery. He was joined on Newshour by the BBC's science correspondent, Pallab Ghosh.

(Photo: Computer simulation of a collision of two black holes. Credit: REUTERS/Caltech/MIT/LIGO Laboratory)