What are gravitational waves?
Scientists have detected gravitational waves that could offer a window on the origin of the universe.
These waves are ripples in the fabric of space-time that are produced when black holes collide and stars explode.
The waves were first proposed 100 years ago by Albert Einstein, as a key prediction of his Theory of General Relativity.
The BBC’s Pallab Ghosh explains what the discovery means for the future of science.