That gravity propagates as a wave is a consequence of Relativity. To date we have no direct detections of gravitational waves, but we have detected energy loss

That gravity propagates as a wave is a consequence of Relativity. To date we have no direct detections of gravitational waves, but we have detected energy loss in a binary system which is consistent with theory. http://en.wikipedia.org/wiki/PSR_B1913%2B16 http://en.wikipedia.org/wiki/PSR_B1913%2B16