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Three steps to the Hubble constant [21]. A decade before Hubble made his observations, a number of physicists and mathematicians had established a consistent theory of an expanding universe by using Einstein field equations of general relativity.
The earliest and most direct observational evidence of the validity of the theory are the expansion of the universe according to Hubble's law (as indicated by the redshifts of galaxies), discovery and measurement of the cosmic microwave background and the relative abundances of light elements produced by Big Bang nucleosynthesis (BBN).
Hubble's results for Andromeda were not formally published in a peer-reviewed scientific journal until 1929. [29] Hubble's classification scheme. Hubble's findings fundamentally changed the scientific view of the universe. Supporters state that Hubble's discovery of nebulae outside of our galaxy helped pave the way for future astronomers. [30]
The model assumes that general relativity is the correct theory of gravity on cosmological scales. It emerged in the late 1990s as a concordance cosmology, after a period of time when disparate observed properties of the universe appeared mutually inconsistent, and there was no consensus on the makeup of the energy density of the universe.
Hubble's idea allowed for two opposing hypotheses to be suggested. One was Lemaître's Big Bang, advocated and developed by George Gamow. The other model was Fred Hoyle's steady-state model, in which new matter would be created as the galaxies moved away from each other. In this model, the universe is roughly the same at any point in time.
An important parameter in fate of the universe theory is the density parameter, omega (), defined as the average matter density of the universe divided by a critical value of that density. This selects one of three possible geometries depending on whether Ω {\displaystyle \Omega } is equal to, less than, or greater than 1 {\displaystyle 1} .
Experimental observations confirm expansion of universe according to Hubble's law. Since the universe is expanding, the equation for that expansion can be "run backwards" to its starting point. The Lambda-CDM concordance model describes the expansion of the universe from a very uniform, hot, dense primordial state to its present state over a ...
In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the very early universe.Following the inflationary period, the universe continued to expand, but at a slower rate.