According to a popular theory, most matter in the universe is orbiting black holes. Just look at galaxies, which contain almost everything and house supermassive black holes in their centers. A large part of black hole theory involves the cannibalization of stars or even entire galaxies as they fall into the hole’s event horizon.
In a finite universe, these black holes would eventually devour most of the matter, and we would be left with a dark universe. Every now and then there would be a flash of light, almost like lightning, whenever an object was pulled close enough to a black hole to emit energy, and then it would fall dark again.
Eventually, we’d be left with nothing but gravity wells in an abyss. More massive black holes would consume the less massive ones, becoming larger, even more massive black holes. But still, this wouldn’t be the final state of the universe.
Over time, black holes evaporate (lose their mass) because they emit what is called “Hawking radiation.” So after the last black hole dies, we’ll be left with an even distribution of subatomic Hawking radiation particles.