For the first time, physicists have observed ‘ripples’ in the fabric of space-time called gravitational waves. The collision of two black holes is seen in this still from a computer simulation. Image credit: SXS. Gravitational waves — ‘ripples’ in space-time produced by some of the most violent events in the cosmos — were predicted by Albert Einstein in 1916, when he showed that accelerating massive objects would shake space-time...