VAN FLANDERN ARGUES.
One can even argue that these c-gravitons/graviphotons may also be the equivalent of the long postulated aether that light and electromagnetic waves propagate through.
He further demonstrates that gravity acts essentially instantaneously at a speed orders of magnitude greater than light speed, because the measured motion of distant celestial bodies is not affected by delays in the transport of light between them. Hence, gravity acts by a different mechanism than electromagnetic attraction/repulsion, which both act at the speed of light. He then argues that wave/particle duality is a consequence of the interaction between light-speed entities and non-light-speed entities. An implied consequence is that a Grand Unification of all four forces, weak, strong, electromagnetic, and gravitational, is not possible.
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this seems a controversy of what is accepted, ie speed
of gravity and forces can not be unified.