the theoretical quantum of gravitation, usually assumed to be an elementary particle that is its own antiparticle and that has zero rest mass and charge and a spin of two.
(grāv'ĭ-tŏn') A hypothetical particle postulated in supergravity theory to be the quantum of gravitational interaction, mediating the gravitational force. Like all force carriers, the graviton is a boson. It is presumed to have an indefinitely long lifetime, zero electric charge, a spin of 2, and zero rest mass (thus travelling at the speed of light). The graviton has never been detected. See also supersymmetry. See Table at subatomic particle.
postulated quantum that is thought to be the carrier of the gravitational field. It is analogous to the well-established photon of the electromagnetic field. Gravitons, like photons, would be massless, electrically uncharged particles traveling at the speed of light and would be emitted only by highly accelerating, extremely massive objects such as stars. Since gravitons would apparently be identical to their antiparticles, the notion of antigravity is questionable.
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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online. Cite This Source