Gravitational waves are waves in the curvature of space caused by rapidly moving masses. These waves are predicted by the theory of general relativity but have not yet been directly observed, although small changes in the orbital timings of the close pulsar PSR 1913+16 provide indirect evidence of their existence (Thorne, 1987). The gravitational waves considered here are those caused by binary systems similar to, but larger than PSR 1913+16, where two large masses orbit each other.
Gravitational waves are transverse waves; the displacements caused are perpendicular to the direction of motion. The pattern of displacements for the two polarities are shown in Figure . These displacements could not be detected by accelerometers placed around the test rings in Figure 1 because space itself is distorted, but a displacement will be detectable across the ring. These displacements distort the earth as a gravitational wave passes, and the response of the earth to these displacements will be detectable if the gravitational wave is large enough.
Figure 1 The distortion caused by the + and polarities at various phases of gravitational wave cycle. The dotted line is the distorted ring and the solid line is the reference. The direction of propagation is into the page.