(Thanks as always for the APOD ping). It's not so surprising when you consider the difference between the average distance between galaxies and the average distance between stars. The average distance between galaxies is only something like 10 times the size of the galaxies themselves. That's not very much. Our own galaxy is on a collision course with the Andromeda galaxy and the sun isn't likely to hit anything, but I think that's far enough in the future it will already have gone nova and turned into a white dwarf.