It takes a little bit of time for the front of the ship to know that the back of the ship is being accelerated forward by the rocket engines, but that is not the same as the tidal effect of gravity.) ...It takes a little bit of time for the front of the ship to know that the back of the ship is being accelerated forward by the rocket engines, but that is not the same as the tidal effect of gravity.) The lack of a tidal effect can distinguish an accelerating reference frame from one in a gravitational acceleration.