gravitational waves

Ripples in the structure of spacetime, which may occur singly or as continuous radiation. They travel at the speed of light. According to General Relativity theory, massive objects subject to accelerations or changes in shape will emit gravitational waves. Gravitational radiation is emitted most intensely in regions of spacetime where gravity is so strong that General Relativity must be applied and where the velocities are close to that of light. In practice, this means that collapsing stellar cores or interactions of bulk matter with black holes are the most likely sources of gravitational radiation. Rotating neutron stars and binary star systems also emit gravitational radiation, and this mechanism of energy transfer plays an important role in the evolution of close binary systems. Support for the existence of gravitational waves comes from observations of the only known binary star believed to consist of two neutron stars (though pulsed radiation is seen from only one of them). A slight decrease in the orbital period is accounted for precisely if energy is being carried away by gravitational radiation at the rate predicted by General Relativity. Several experiments have attempted to detect gravitational radiation, but none have yet succeeded. Major technical problems remain in achieving the degree of sensitivity required in a detector.