Monster of the Milky Way
I recently watched 'Monster of the Milky Way' on PBS. I was surprised that astrophysicists were surprised to learn that there were monster black holes at the center of many galaxies. When I learned, years ago, that there was a monster black hole at the center of the Milky Way galaxy, it occurred to me that galaxies were like giant solar systems. Solar systems form in large part because of a mass, like our Sun, with a great deal of gravity, attracting smaller bodies. Galaxies, I think, form the same way with black holes, or some other body with heavy gravitational attraction, attracting solar systems. Some galaxies, the ones without black holes at their center, must have some other mass at their centers which attract and keep solar systems and other matter in it's orbit.
An interesting thing I learned from the show is that black holes merge to form larger black holes and galaxies merge to form larger galaxies. Of course, since at the heart of many galaxies is a black hole, when the galaxies merge, the black holes at the center merge as well. And of course, when the black holes merge, they become larger and have a greater gravitational attraction. And, scientists calculate that our own Milky Way galaxy will merge with the Andromeda galaxy billions of years from now.
I wonder...the universe is expanding. If galaxies continue to merge, there will, of course, be fewer galaxies in the universe. But also, their black holes will become much more massive and have much more gravitational attraction. If the galaxies continue to merge, there will be fewer and fewer galaxies in the universe. But more importantly, their center black holes will be larger and have much more gravitational pull. If enough of the galaxies in the universe merge, and the black holes at their centers merge, could enough gravity build to start a collapsing of the universe? Possibly so much gravitational pull that all mass, no matter how far away, will eventually be pulled back in, resulting in another big bang (or maybe some mass escapes and subsequent big bangs are smaller until there isn't enough mass left to create a big bang any longer). I think this possibility might be calculable if we can determine the mass of all matter in the universe. We might find that the universe is in a never-ending, continual expanding/contracting cosmic dance.
