Prototypes of laser-interferometric gravitational wave detectors have been built and are operating at both institutions. Gravitational waves are ripples in the fabric of space and time produced by violent events in the distant universe, for example by the collision of two black holes or by the cores of supernova explosions. Gravitational waves are emitted by accelerating masses much as electromagnetic waves are produced by accelerating charges. These ripples in the space-time fabric travel to Earth, bringing with them information about their violent origins and about the nature of gravity. Albert Einstein predicted the existence of these gravitational waves in 1916 in his general theory of relativity, but only now, in the 1990s, has technology become powerful enough to permit detecting them and harnessing them for science.
Scientists therefore have great confidence that gravitational waves exist.
Joseph Taylor and Russel Hulse were awarded the 1993 Nobel Prize in Physics for their discovery of this binary pulsar. LIGO will be used for research into the nature of gravity, and it will open up an entirely new window onto the universe. It will thus be a scientific tool both for physics and for astronomy. General relativity describes gravity as a manifestation of the curvature of space-time. This description has been tested and proved correct in the solar system, where gravity is weak and changes slowly due to the orbital motions of planets and their satellites.