▪ Abstract The Universe is in transition. At early times, galactic evolution was dominated by
hierarchical clustering and merging, processes that are violent and rapid. In the far future,
evolution will mostly be secular—the slow rearrangement of energy and mass that results
from interactions involving collective phenomena such as bars, oval disks, spiral structure,
and triaxial dark halos. Both processes are important now. This review discusses internal
secular evolution, concentrating on one important consequence, the buildup of dense�…