This is a project to build and operate a Laser Interferometer Gravitational-Wave Observatory (LIGO) and to continue research and development of interferometric detectors of ever higher sensitivities. The proposed LIGO includes interferometer installations of 4-km arm length and support facilities; these installations would be located at two widely separated sites in the continental United States and would operate in coincidence for the detection of gravitational waves. The LIGO project is a joint effort of scientists at the California Institute of Technology and the Massachusetts Institute of Technology and includes collaborative programs with scientists at Stanford, University of Colorado, and other institutions. The observatory will be operated as a user facility, open for use by the national community, and will become part of a planned worldwide network of gravitational- wave observatories. The proposed LIGO is based on almost two decades of science research and development. The ultimate objectives of the LIGO program include (1) tests of Einstein's General Theory of Relativity---in particular, measurement of the velocity and polarization of gravitational radiation and studies of the domain of highly nonlinear, dynamic gravity, and (2) the opening of an observational window on the universe that differs fundamentally from that provided by electromagnetic or particle astronomy.
