Comment Re:4th Dimension? (Score 1) 236
Because of relativity this long-term gravitational effect has to move linearly with the objects through space, so it would kind of wobble with the galaxies when they moving relative to each other. When the galaxies collide the past gravitational effect would keep moving linearly.
Objects of all sizes would have this effect. But since planets moves around stars and stars don't move straight for long either the gravity can not build up over a long time, as it can on the scale of galaxies.