What is it that causes the final parsec problem? I know one problem I see. From our frame of reference, at the event horizon of a black hole, time stops. It should take an infinite amount of time for them to merge. Maybe that is the cause of the final parsec problem. I have another question about black holes. What happens to dark matter when it collides with a black hole. Are black holes partly made of dark matter? I would think they must be.