Scientists at MIT and Caltech are collaborating on the LIGO Project (Laser Interferometer Gravitational-wave Observatory), building two large installations (one in Hanford, WA, and the other in Livingston Parish, LA) that together will detect gravitational radiation from space. Each L-shaped interferometer has arms 2.5 miles long; laser beams sense minute mirror motions at the ends of the arms caused by gravitational waves from astrophysical sources (the collision of distant stars, for example), and the resulting signal carries the signature of the event.
The mirrors are supported by elastomer and steel isolators and controlled by precision servo-systems to minimize background vibration from passing vehicles and other human activity, as well as from ocean waves that constantly pound the earth. The interferometer is housed in a very clean vacuum system to avoid contamination of the mirrors and to eliminate fluctuations in the optical path length because of residual gas.
Scientists hope the detectors (projected for completion in 2000) will provide the first direct evidence for gravitational waves predicted in Einstein's general theory of relativity. An astronomy based on study of gravitational waves (which, unlike light, are not impeded by clouds and other intervening matter) will allow a deeper understanding of supernovae, the coalescence of orbiting binary stars, the oscillation of black holes, and as-yet-unimagined astrophysical catastrophes. MIT's part of the project is headed by Professor Rainer Weiss of physics. Funding is provided by the NSF.
A version of this article appeared in MIT Tech Talk on March 13, 1996.