Some people think that space is expanding as well. These people think that intra-galactic distances are relatively consistent, but inter-galactic distances are increasing in an accelerating fashion.
"Additionally, the expansion rate of the universe has been measured to be accelerating due to the repulsive force of dark energy which appears in the theoretical models as a cosmological constant. This acceleration of the universe, or "cosmic jerk", has only recently become measurable, and billions of years ago, the universe's expansion rate was actually decelerating due to the gravitational attraction of the matter content of the universe. According to the simplest extrapolation of the currently-favored cosmological model (known as "ΛCDM"), however, the dark energy acceleration will dominate on into the future."