In cosmology, the steady state theory (also known as the Infinite Universe Theory or continuous creation) is a model developed in 1948 by Fred Hoyle, Thomas Gold, Hermann Bondi and others as an alternative to the Big Bang theory (known, usually, as the standard cosmological model). Although the model had a large number of supporters among cosmologists in the 1950s and 1960s, the number of supporters decreased markedly in the late 1960s. It is also the basis for another theory known as the quasi-steady state theory which postulates big bang(s) occurring over time. The key importance of the theory is that it generated some of the most important research in astrophysics, much of which supports aspects of the Big Bang. Being a highly testable theory, in the best scientific tradition, it opened up many lines of questioning and new avenues of inquiry in cosmology.

Overview

The steady state theory was developed as a result of theoretical calculations that showed that a static universe was impossible under general relativity and observations by Edwin Hubble that the universe was expanding. The steady state theory asserts that although the universe is expanding, it nevertheless does not change its look over time. For this to work, new matter must be formed to keep the density equal over time.

Because only very little matter needs to be formed, roughly a few hundred atoms of hydrogen in the Milky Way Galaxy each year, it is not a problem of the theory that the forming of matter is not observed directly. The steady state theory had a number of attractive features. Most notably, the theory removes the need for the universe to have a beginning.

An aesthetically unattractive feature of the theory is that the postulated spontaneous new matter formation would presumably need to include the heavy isotope of hydrogen deuterium as well as the more common light hydrogen isotope, since no mechanism of nucleosynthesis in stars or by other processes accounts for the observed abundance of deuterium. the Big Bang model, all deuterium is made directly after the "bang," before the existence of the first stars.

Problems

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 (i.e., redshift, and thus, because of the finiteness of the speed of light, in the past) not in closer galaxies. Halton Arp, also since the 1960s, has been taking a different view of the data, claiming that evidence can also point to quasars existing as close as the local Virgo cluster, however, this theory is not accepted by mainstream scientists today.

For most cosmologists, the refutation of the steady-state theory came with the discovery of the cosmic background radiation in 1965, which was predicted by the big bang theory. Steven Hawking said that the fact that microwave radiation had been found, and that it was thought to be left over from the big bang, was "the final nail in the coffin of the steady-state theory." Within the steady state theory this background radiation is the result of light from ancient stars which has been scattered by galactic dust. However, this explanation has been unconvincing to most cosmologists as the cosmic microwave background is very smooth, making it difficult to explain how it arose from point sources, and the microwave background shows no evidence of features such as polarization which are 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 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.

As of 2006, the majority of astronomers consider the big bang theory to be the best description 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. At the same time, after the unexpected observation of an accelerating universe in the late-1990s, there were efforts to develop quasi-steady state theories, in which it is said that there is not a single big bang but rather multiple big bangs over time which create matter.

Books

• Fred Hoyle, Geoffrey Burbidge, and Jayant V. Narlikar, A Different Approach to Cosmology, Cambridge University Press, 2000, ISBN 0521662230.
• Simon Mitton, Conflict in the Cosmos: Fred Hoyle's Life in Science, Joseph Henry Press, 2005, ISBN 0309093139 or, Fred Hoyle: a life in science, Aurum Press, 2005, ISBN 1854109618
• Steven Weinberg, Gravitation and Cosmology (Wiley, New York, 1972), pp. 495–464.

References

• Quasi-steady state model - Narlikar, Vishwakarma, Burbidge

Physical cosmology | Obsolete scientific theories

Steady-State-Theorie | Teoría del Estado Estacionario | Création continue | Teorija stalnog stanja | Teoria dello stato stazionario | המצב היציב | Steady-statetheorie | 定常宇宙論 | Teoria stanu stacjonarnego (kosmologia) | Teoria do estado estacionário | Teorija mirujočega stanja