Steady
State theory
In cosmology, the Steady State theory is a now-obsolete
theory and model developed as an alternative to the Big Bang theory of
the universe's origin. In steady state views, new matter is continuously
created as the universe expands, thus adhering to perfect cosmological principle.While the steady state model enjoyed some popularity in the first half of the 20th Century, it is now rejected by the vast majority of professional cosmologists and other scientists, as the observational evidence points to a Big Bang-type cosmology and a finite age of the universe.
History
Sir James Jeans, in the 1920s, was the first to conjecture a
steady state cosmology based on a hypothesized continuous creation of matter in
the universe.The steady state theory of Bondi and Gold was inspired by the circular plot of the film Dead of Night, 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 not in closer galaxies.
Whereas the Big Bang theory predicted as much, the Steady State theory predicted that such objects would be found everywhere, 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 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 dL 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.
Since that time, the Big Bang theory has been considered 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.
Quasi-steady state
Quasi-steady state cosmology (QSS) was proposed in 1993 by Fred Hoyle, Geoffrey Burbidge,
and Jayant V. Narlikar as a new incarnation of the steady state
ideas meant to explain additional features unaccounted for in the initial
proposal. The theory suggests pockets of creation occurring over time within the universe, sometimes referred to as minibangs, mini-creation events, or little bangs.
After the observation of an accelerating universe, further modifications of the model were made.
Other proponents
Chaotic Inflation theory has many similarities with steady
state theory, however on a much larger scale than originally envisaged. It is
the C-field and the notion of quasi-steady state universe that has some
resemblance to chaotic inflation theory or eternal inflation,
which sometimes posits an infinite universe with neither beginning nor end, in
which inflation operates continuously, on a scale beyond the observable universe, to create the matter of the cosmos.
However, both steady state and quasi-steady state assert that the creation
events of the universe (new hydrogen atoms in the steady state case) can be
observed within the observable universe, whereas inflationary theories do not
posit inflation as an ongoing process within the observable universe.
Criticism
Astrophysicist and cosmologist Ned Wright has
pointed out flaws in the theory.These first comments were soon rebutted by the proponents.
Wright and other mainstream cosmologists reviewing QSS have pointed out new flaws and discrepancies with observations left unexplained by proponents.
