n. (context physics English) A postulated fluctuation in spacetime that propagates as a wave at the speed of light
Gravitational waves are ripples in the curvature of spacetime that propagate as waves, generated in certain gravitational interactions that propagate outward from their source. The possibility of gravitational waves was discussed in 1893 by Oliver Heaviside using the analogy between the inverse-square law in gravitation and electricity. In 1905 Henri Poincare first predicted gravitational waves (ondes gravifiques) emanating from a body and propagating at the speed of light as being required by the formalism of spacetime. Predicted in 1916 by Albert Einstein on the basis of his theory of general relativity, gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation. Gravitational waves cannot exist in the Newton's law of universal gravitation, since it is predicated on the assumption that physical interactions propagate at infinite speed.
Gravitational-wave astronomy is an emerging branch of observational astronomy which aims to use gravitational waves to collect observational data about objects such as neutron stars and black holes, events such as supernovae, and processes including those of the early universe shortly after the Big Bang.
Various gravitational-wave observatories (detectors) are under construction or in operation, such as Advanced LIGO which began observations in September 2015.
Potential sources of detectable gravitational waves include binary star systems composed of white dwarfs, neutron stars, and black holes. On February 11, 2016, the LIGO Scientific Collaboration and Virgo Collaboration teams announced that they had made the first observation of gravitational waves, originating from a pair of merging black holes using the Advanced LIGO detectors. On June 15, 2016, a second detection of gravitational waves from coalescing black holes was announced.