is a hypothetical particle
that 'transfers' gravitation's force (particles like this are known as gauge bosons
) from its field
. Gravitons have never been observed, directly or indirectly,
however, there have been several theories that use gravitons to explain certain phenomena. For example, a theory that describes black holes
by combining quantum mechanics
, has been advanced by Georgi Dvali and Cesar Gomez, which suggests a black hole is "an overpacked bucket of gravitons".
Because the graviton is a particle that has force (gravity), it is classed as a gauge boson. Other gauge bosons include the photon, the gluon, and the W and Z particles.
If someone found one, it could lead to a theory which would join together the four main physical forces: electromagnetism, gravity, strong force and weak force.