Steady State Theory and Pulsating Theory
: steady state theory dust cloud theory pulsating theory
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). In steady state views, new matter is continuously created as the universe expands, so that the perfect cosmological principle is adhered to.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.
The theory requires that new matter must be continuously created (mostly as hydrogen) to keep the average density of matter equal over time. The amount required is low and not directly detectable: roughly one solar mass of baryons per cubic megaparsec per year or roughly one hydrogen atom per cubic meter per billion years, with roughly five times as much dark matter. Such a creation rate, however, would cause observable effects on cosmological scales.
Dust-Cloud Theory. Between 1940 and 1955 the German astronomer Carl f. von Weizsaccker, the Dutch-American astronomer Gerald P. Kuiper and the U. S. chemist Harold C. Urey worked out a theory that attempted to account for all the characteristics of the solar system that need to be explained. According to their dust-cloud theory, the solar system was formed from a slowly rotating cloud of dust and gas that contracted and started to rotate faster in its outer parts, where eddies formed. These eddies were small near the center of the cloud and larger at greater distances from the center. The distances corresponded more or less to the Titius-Bode relation.
As
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). In steady state views, new matter is continuously created as the universe expands, so that the perfect cosmological principle is adhered to.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.
The theory requires that new matter must be continuously created (mostly as hydrogen) to keep the average density of matter equal over time. The amount required is low and not directly detectable: roughly one solar mass of baryons per cubic megaparsec per year or roughly one hydrogen atom per cubic meter per billion years, with roughly five times as much dark matter. Such a creation rate, however, would cause observable effects on cosmological scales.
Dust-Cloud Theory. Between 1940 and 1955 the German astronomer Carl f. von Weizsaccker, the Dutch-American astronomer Gerald P. Kuiper and the U. S. chemist Harold C. Urey worked out a theory that attempted to account for all the characteristics of the solar system that need to be explained. According to their dust-cloud theory, the solar system was formed from a slowly rotating cloud of dust and gas that contracted and started to rotate faster in its outer parts, where eddies formed. These eddies were small near the center of the cloud and larger at greater distances from the center. The distances corresponded more or less to the Titius-Bode relation.
As