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Static universe
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The idea of a static universe or "Einstein's universe" is one which demands that space is not expanding nor contracting but rather is dynamically stable. Albert Einstein once proposed such a model as his preferred cosmology by adding a cosmological constant to his equations of general relativity to counteract the dynamical effects of gravity which in a universe of matter would cause the universe to collapse. This motivation evaporated after the discovery by Edwin Hubble that the universe is not static, but expanding; in particular, Hubble discovered a relationship between redshift and distance, which forms the basis for the modern expansion paradigm.
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The idea of a static universe or "Einstein's universe" is one which demands that space is not expanding nor contracting but rather is dynamically stable. Albert Einstein once proposed such a model as his preferred cosmology by adding a cosmological constant to his equations of general relativity to counteract the dynamical effects of gravity which in a universe of matter would cause the universe to collapse. This motivation evaporated after the discovery by Edwin Hubble that the universe is not static, but expanding; in particular, Hubble discovered a relationship between redshift and distance, which forms the basis for the modern expansion paradigm. This led Einstein to declare this cosmological model, and especially the introduction of the cosmological constant, his "biggest blunder".
Even after Hubble'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 most astrophysicists to conclude that the static universe is not the correct model of our universe.
Einstein's universe
Einstein's proposal was a universe characterized by the dust solution of Einstein's field equation for a value of the cosmological constant equal to , where is Newtonian gravitational constant, is the energy density of the matter in the universe and is the speed of light. Value is called Einstein's cosmological constant or, alternatively, the cosmological constant of Einstein's universe.
The radius of curvature of space of Einstein's universe, called "Einstein's radius", is equal to
"Einstein's universe" is one of Friedmann's solutions of Einstein's field equation, for the value of cosmological constant . This is the only stationary solution of all Friedmann's solutions, and because it is stationary, it is thought to be non physical by majority of astronomers. Those astronomers think that the universe is expanding because there is observed a phenomenon of Hubble redshift and it is interpreted by those astronomers as a Doppler shift caused by galaxies moving away from our own Galaxy. Therefore, it is thought that the real solution of Einstein's field equation cannot be stationary.
Einstein came to consider this modification of his theory as his "biggest blunder." Most physicists of the twentieth century assumed it to have the value zero; this assumption predicts a decelerating expansion of the universe. However, with the discovery of the accelerating universe, the cosmological constant has been revived as a possible explanation for dark energy..
Other problems with the model
Besides from Hubble's law, the cosmic microwave background radiation is used as empirical evidence of the Big Bang model. A static universe model has to explain this radiation in some other way. Also there has to be some process of "recreation of Hydrogen" since if the universe was not created some finite time ago, as in the Big Bang model, the stars would otherwise all have run out of fuel (Hydrogen) by now.
Nonstandard cosmologies
A very small number of proponents of the static universe continue to promote nonstandard cosmologies in defiance of scientific consensus, though the term "static universe" has fallen somewhat out of favor since it is argued by advocates of these theories that the universe is "dynamically evolving".
See also
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