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Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation. [7] Newton's law of universal gravitation , part of classical mechanics , does not provide for their existence, instead asserting that gravity has instantaneous effect everywhere.
Measurable emissions of gravitational waves are expected from binary systems (collisions and coalescences of neutron stars or black holes), supernova explosions of massive stars (which form neutron stars and black holes), accreting neutron stars, rotations of neutron stars with deformed crusts, and the remnants of gravitational radiation ...
acoustic radiation, such as ultrasound, sound, and seismic waves, all dependent on a physical transmission medium; gravitational radiation, in the form of gravitational waves, ripples in spacetime; Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated
Gravitational waves can be emitted by many systems, but, to produce detectable signals, the source must consist of extremely massive objects moving at a significant fraction of the speed of light. The main source is a binary of two compact objects. Example systems include:
Alternatively, if gravitons are massive at all, the analysis of gravitational waves yielded a new upper bound on the mass of gravitons. The graviton's Compton wavelength is at least 1.6 × 10 16 m , or about 1.6 light-years , corresponding to a graviton mass of no more than 7.7 × 10 −23 eV / c 2 . [ 18 ]
The speed of gravity (more correctly, the speed of gravitational waves) can be calculated from observations of the orbital decay rate of binary pulsars PSR 1913+16 (the Hulse–Taylor binary system noted above) and PSR B1534+12. The orbits of these binary pulsars are decaying due to loss of energy in the form of gravitational radiation.
General relativity also predicts novel effects of gravity, such as gravitational waves, gravitational lensing and an effect of gravity on time known as gravitational time dilation. Many of these predictions have been confirmed by experiment or observation, most recently gravitational waves.
Gravitation, also known as gravitational attraction, is the mutual attraction between all masses in the universe.Gravity is the gravitational attraction at the surface of a planet or other celestial body; [6] gravity may also include, in addition to gravitation, the centrifugal force resulting from the planet's rotation (see § Earth's gravity).