The Speed of Gravity

It is well known that gravitational interactions between bodies in all dynamic systems are always taken to happen instantaneously. In fact, a finite gravity speed would give rise to the aberration phenomenon, whereby the gravitational acceleration vector would be directed toward the retarded position of the source, not toward the instantaneous one. It is experimentally ascertained that gravitational effects do not present aberration (unlike the electromagnetic ones). This is why astronomers can calculate orbits using instantaneous forces.