Gravitational Forces with Strongly Localized Retardation
  We solve the linearized Einstein equations for a specific oscillating mass distribution and discuss the usual counterarguments against the existence of observable gravitational retardations in the "near zone", where d/r << 1 (d = oscillation amplitude of the source, r = distance from the source). We show that they do not apply in the region d/r \approx 1, and prove that gravitational forces are retarded in the immediate vicinity of the source. An experiment to measure this retardation is proposed, which may provide the first direct experimental observation of propagating gravitational fields. 
Thomas Chen, William D. Walker, Jurg Dual (ETH Zurich, Switzerland)