Gravitational waves: A new kind of information about the universe

The first direct detections of gravitational waves are confidently expected by 2017-18, and with luck could happen earlier. Regular observations will test general relativity stringently and will provide a wealth of information about black holes and neutron stars, about stellar evolution, and eventually about the extremely early universe. This information is of a different character than anything we have so far: gravitational wave detection is like listening to the universe rather than looking at it, and its sources are typically dark in electromagnetic waves. As with listening to everyday sounds, we may find that we can hear many things that we can't otherwise see. The talk will review current and planned detectors on the ground, in space, and using probes like pulsars and the cosmic microwave background, and will describe the new physics and astronomy that might accompany the operation of these detectors.