'Sound' of the gravitational wave

Scientists have detected gravitational waves that could offer a window on the origin of the universe.

First proposed by Einstein 100 years ago, these waves are ripples in the fabric of space-time that are produced when black holes collide and stars explode - but until now, they had never been directly detected.

As announced at a press conference today, the international Ligo Collaboration recorded a historic signal on 14 September 2015.

The BBC’s Pallab Ghosh explains the sound of the wave that the team detected.