I was thinking about the supermassive black hole that is theorized to be at the center of our galaxy, and indeed, at the center of most galaxies. If that black hole is continuously consuming the stars, planets and gas around it, given enough time, will it not consume the entire galaxy that orbits it? Or is there a size limit for black holes? Do they just keep adding mass as long as there is matter and energy to consume? Does this include dark matter and dark energy? Are they affected by black holes like ordinary matter? I have more, but the next questions depend on the answers to these. Thanks for any help.