no longer be able to make contact. Therefore, any observer in a de Sitter universe would have cosmological event horizons beyond which that observer can never see nor learn any information. If our universe is approaching a de Sitter universe then eventually we will not be able to observe any galaxies other than our own Milky Way (and any others in the gravitationally bound Local Group, assuming they were to somehow survive to that time without merging). Role in the Benchmark Model The Benchmark Model is a model consisting of a universe made of three components - radiation, ordinary matter, and dark energy - that fit current data about the history of the universe. These components make different contributions to the expansion of the universe as time elapses. Specifically, when the universe is radiation dominated, the expansion factor scales as , and when the universe is matter dominated . Since both of these grow slower than the exponential, in the future the scale factor will be dominated by the exponential factor representing the pure de Sitter universe. The point at which this starts to occur is known as the matter-lambda equivalence point and the modern-day universe is believed to be relatively close to this point. See also Cosmic inflation de Sitter space for more mathematical properties Deceleration parameter Causal patch References Physical cosmology Exact solutions in general relativity Inflation (cosmology) ru:Модель де Ситтера