The detection of gravitational waves.

Gravitational waves, one of the more exotic predictions of Einstein's General Theory of Relativity, may, after 80 years of controversy over their existence, be detected within the next decade. Sources such as coalescing compact binary systems, stellar collapses and pulsars are all possible candidates for detection. The most promising design of gravitational wave detector, offering the possibility of very high sensitivities over a wide range of frequency, uses test masses a long distance apart and freely suspended as pendulums on earth or in drag free craft in space; laser interferometry provides a means of sensing the motion of the masses produced as they interact with a gravitational wave. The main theme of this paper will be a review of the mechanical and optical principles used in the various long baseline systems being built around the world - LIGO (USA), VIRGO (Italy/France), TAMA300 (Japan) and GEO600 (UK/Germany) - and in LISA, a proposed space-borne interferometer.