On September 14, 2015, scientists from the LIGO Scientific Collaboration and the Virgo Collaboration observed the collision and fusion of the two black holes by directly measuring their gravitational waves. This detection came 100 years after Einstein developed the general theory of relativity that predicted gravitational waves, and 50 years after scientists began searching for them. This discovery has truly profound implications, and opens a new window on the cosmos. Gravitational waves provide unique information on the most energetic astrophysical events, revealing insights into the nature of gravity, matter, space, and time. David Reitze talks about how they made the detection and discusses how gravitational astronomy promises to change our understanding of the universe. SPEAKER: David Reitze, Executive Director of the LIGO Laboratory at the Caltech and a Professor of Physics at the University of Florida Presented by Sydney Ideas on 11 April 2017: http://sydney.edu.au/sydney_ideas/lectures/2017/david_reitze.shtml