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?

Anything that isn't at the center feels a pull towards the center. For this reason alone, more stuff ends up there and more potential for a supermassive black hole.

That isn't to say that there aren't BHs with thousands of solar masses floating in spiral galaxy arms.

All of that is somewhat correct, but it's a bit more complicated. The central supermassive black hole (SMBH) often forms fairly early in the universe, and won't get dragged around very much, because it is the biggest single object in the galaxy. It would likely form at a local peak in the matter distribution (where there are a lot of stars and gas) when early stars blow up as supernovae and their remnant black holes all merge. There are also large black holes in the center of many (all?) globular clusters, which end up there for the same reasons.

But we still don't have a complete picture of when the SMBH forms relative to the galaxy. But the basic idea of: big things are in the center, big things don't get pushed around, big things attract more big things and grow bigger, is a good way to look at it.

__________________
"What do you care what other people think?" -- Richard Feynman
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." -- Feynman, at the conclusion of his Challenger report

Big things don't get pushed around?!What about that recent discovery of a supermassive black hole of 100 million Solar masses that after a merger is being hurled out of its galaxy with a velocity of 2700 km/s?

Ok, how about: "big things don't get pushed around, except occasionally by other big things due to general relativistic effects when they merge." Better?

__________________
"What do you care what other people think?" -- Richard Feynman
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." -- Feynman, at the conclusion of his Challenger report

OK, that's much better .

BHs are such pushovers!

Pro wrestling on a galactic scale.