丁香园AV

Synopsis

If we look at some of the largest masses in the Universe that are accelerating, such as two black holes orbiting each other, Einstein's theory of gravity predicts the production of 'ripples' in space-time that would propagate outwards. This ripple is akin to ripples in a pond when a stone is dropped in. These ripples are called gravitational waves. The production of gravitational waves was predicted in General Relativity in 1915, actual proof of their existence was not found until 20 years after Einstein's death (1955), with the discovery of a binary pulsar system which has two very dense stars orbiting each other. The rate at which the stars were approaching each other was described precisely by General Relativity's gravitational waves mechanism. Fast forward to 2015, and we finally have the first direct measurement of these waves at LIGO, providing further confirmation of General Relativity.