Другое : Steady state theory
Steady state theory
Steady state theory
In cosmology, the steady state
theory is a model developed in 1949 by Fred Hoyle, Thomas Gold and others as an
alternative to the Big Bang theory. 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 and today it is considered a non-standard cosmology.
It is also the basis for another theory known as the quasi-steady state theory
which postulates a lot of little big bangs occurring over time. 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. Despite violating conservation of mass, the steady state
theory had a number of attractive features. Most notably, the theory removes
the need for the universe to have a beginning.
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.
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.
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.
As of 2005, the big bang theory is
the one that the majority of astronomers consider the best approximation to
describing 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 there is not a single big bang but rather multiple big bangs
over time which create matter.
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