Gravity from the ancient Greeks to Newton -- Einstein's special theory of relativity -- The general theory of relativity -- Gravitational waves : their long and difficult history -- The life and death of stars -- Astrophysical sources of gravitational radiation -- Numerical relativity -- A brief history of terrestrial gravitational wave detectors -- The technology of LIGO -- At last: detections -- and many! -- The birth of GW multi-messenger astronomy -- The future