Static Universe

A static universe, also referred to as a "stationary" or "Einstein" universe, is a model in which space is neither expanding nor contracting. Albert Einstein proposed such a model as his preferred cosmology in 1917. He added a positive cosmological constant to his equations of general relativity to counteract the attractive effects of gravity on ordinary matter, which would otherwise cause the universe to either collapse or expand forever. This motivation evaporated after proposals first by the astrophysicist and Roman Catholic priest, Georges Lemaître, and then by astronomer Edwin Hubble, that the universe appears to be not static, but expanding; in particular, Hubble researched data from the observations made by astronomer Vesto Slipher to confirm a relationship between redshift and distance, which forms the basis for the modern expansion paradigm. According to George Gamow this led Einstein to declare this cosmological model, and especially the introduction of the cosmological constant, his "biggest blunder".

Even after Hubble's, Slipher's and Lemaître's observations, Fritz Zwicky proposed that a static universe could still be viable if there was an alternative explanation of redshift due to a mechanism that would cause light to lose energy as it traveled through space, a concept that would come to be known as "tired light". However, subsequent cosmological observations have shown that this model is not a viable alternative either, leading nearly all astrophysicists to conclude that the static universe is not the correct model of our universe.