steady state theory

 steady state theory






in the 1920s, was the first to conjecture a steady state cosmology based on a hypothesized continuous creation of matter in the universe.^[1][2] The idea was then revised in 1948 by Fred Hoyle, Thomas Gold, Hermann Bondi and others. The steady state theory of Bondi and Gold was inspired by the circular plot of the film Dead of Night,^[3] which they had watched together. Theoretical calculations showed that a static universe was impossible under general relativity, and observations by Edwin Hubble had shown that the universe was expanding. The steady state theory asserts that although the universe is expanding, it nevertheless does not change its appearance over time (the perfect cosmological principle); it has no beginning and no end.
Problems with the steady-state theory began to emerge in the late 1960s, when observations apparently supported the idea that the universe was in fact changing: quasars and radio galaxies were found only at large distances (therefore could have existed only in the distant past), not in closer galaxies. Whereas the Big Bang theory predicted as much, the Steady State theory predicted that such objects would be found throughout the universe, including close to our own galaxy.
For most cosmologists, the refutation of the steady-state theory came with the discovery of the cosmic microwave background radiation in 1965, which was predicted by the Big Bang theory. Stephen Hawking described this discovery as "the final nail in the coffin of the steady-state theory". The steady-state theory explained microwave background radiation as the result of light from ancient stars that has been scattered by galactic dust. However, the cosmic microwave background level is very even in all directions, making it difficult to explain how it could be generated by numerous point sources and the microwave background radiation shows no evidence of characteristics such as polarization that normally associated with scattering. Furthermore, its spectrum is so close to that of an ideal black body that it could hardly be formed by the superposition of contributions from a multitude of dust clumps at different temperatures as well as at different redshifts. Steven Weinberg wrote in 1972,

The steady state model does not appear to agree with the observed d_L versus z relation or with source counts ... In a sense, the disagreement is a credit to the model; alone among all cosmologies, the steady-state model makes such definite predictions that it can be disproved even with the limited observational evidence at our disposal. The steady-state model is so attractive that many of its adherents still retain hope that the evidence against it will disappear as observations improve. However, if the cosmic microwave background radiation ... is really black-body radiation, it will be difficult to doubt that the universe has evolved from a hotter, denser early stage.^[4]

Since this discovery, the Big Bang theory has been considered to provide the best explanation of the origin of the universe. In most astrophysical publications, the Big Bang is implicitly accepted and is used as the basis of more complete theories.