As the title says, do we have to have black holes for the universe to run? Every galaxy has a suppermasive black hole at its center. What if there were a star at the center of our galaxy? I guess it would have to be so big but that means the star would soon run out of energy and then explode, i.e Supernova? And what if there were nothing at all at the center of our galaxy. No black holes, no stars, nothing?