# Apparent non-aberration of gravitational waves

Since GR assumes that gravitational waves travel at speed $c$, we expect we would be able to some day detect an aberration effect similar the that of light. Of course, gravitational waves are so tiny in magnitude, we haven't yet unambiguously detected them, so aberration measurements aren't yet possible. However, planetary orbits appear to behave as if gravitational waves have "infinite" speeds, since they aren't seemingly affected by the finite time between where a planet is currently located and the time lapse from Sun's force.

Can someone explain why planetary orbits behave as if gravitational waves have Newtonian-like "infinite" velocities? I'd appreciate a response that doesn't resort to tensor notation.

Similar lack of simple 'delay' happens with electromagnetic fields. When you have a point charge moving with constant velocity, the field does not work as if it had some lag. You can play with this applet to get the idea: http://www.cco.caltech.edu/~phys1/java/phys1/MovingCharge/MovingCharge.html

In electromagnetic field, the past motion of the field source makes the field at distance be as if the motion was continued at same velocity to the present time and then the field was propagated at infinite speed.

Note that this does not happen due to some extra rule; that's what the field equations naturally work out to.

With the general relativity, AFAIK, that sort of 'extrapolation' works not only for speed but also for the acceleration, so that if you have an object moving with constant acceleration, you won't be able to distinguish GR from instantaneous propagation. The delay effects in GR are, consequently, very small.