History of Graviton

	Revision 5 . . October 30, 2001 6:21 am by Dave McKee [Cut (irrelevant?) stuff on why it must be massless.]
	Revision 4 . . May 9, 2001 7:51 am by (logged).156.219.xxx

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Changed: 1c1

Elementary particle of spin 2 (a boson) that is believed to be responsible for the propagation of the gravitational interaction. Its rest mass is zero and so it moves at the speed of light. If a massless particle did not travel at the speed of light then there would be some frame of reference within which it would be at rest. In such a case, its total energy would be exactly zero and it would violate the principle that everything which exists embodies some form of energy.

Elementary particle of spin 2 (a boson) and rest mass zero, that is believed to be responsible for the propagation of the gravitational interaction, although it has not yet been detected.