Thread: Do galaxies obey newtons law?

I've been thinking, say that galaxies collide and they both move off from each other for a while. Then at a distance, say several 100,000's of light years does not gravity take so long to interact with each other that the centre of gravity is distorted from where it should be? I mean by definition, if the masses of two objects are close, say a light second away, then gravity can act almost instantly. But when there are hundreds of thousands of years for that gravity to travel, would not the interacting gravity of both objects be telling the two galaxies to move towards a space they are no longer in?

They obey Einstein's laws.

Such an effect would indeed exist - and it makes for an interesting thought experiment - but keep in mind that colliding galaxies move toward each other at speeds hundreds of times slower than light so I can't imagine it would be observable to an astronomer.