Gravitational waves are ripples in the fabric of space-time caused by some of the most violent and energetic processes in the universe. Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity.

Gravitational waves are generated by accelerating masses, such as binary stars orbiting each other, merging black holes, or the Big Bang. These waves travel at the speed of light, carrying with them information about their origins, as well as clues to the nature of gravity itself.

Gravitational waves are incredibly difficult to detect, as they are incredibly weak by the time they reach Earth. However, in 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected the first gravitational waves from a pair of merging black holes. This discovery was the first direct observation of gravitational waves, and opened up a new field of astronomy.