I was sitting around wondering why there seems to be a supermassive black hole at the center of nearly every galaxy. Why the center? Is it like panning for gold, where the heavy stuff falls towards the middle? Like if you have a supermassive black hole orbiting a galaxy, it's going to gobble up stuff as it goes around the galactic nucleus and gain mass for everything that falls in it. As it gains mass, would it's orbit grow smaller and smaller until it's just stuck at the center of a galaxy? Would a massive black hole loose orbital velocity in order to conserve momentum since it's mass is increasing with time?