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The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. [1] The concept of an expanding universe was scientifically originated by physicist Alexander Friedmann in 1922 with the mathematical derivation of the Friedmann equations.
The chronology of the universe describes the history and future of the universe according to Big Bang cosmology. Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, with an uncertainty of around 21 million years at the 68% confidence level.
In medieval philosophy, there was much debate over whether the universe had a finite or infinite past (see Temporal finitism).The philosophy of Aristotle held that the universe had an infinite past, which caused problems for past Jewish and Islamic philosophers who were unable to reconcile the Aristotelian conception of the eternal with the Abrahamic view of creation. [2]
The traditional model of the Big Bang. The use of only general relativity to predict what happened in the beginnings of the universe has been heavily criticized, as quantum mechanics becomes a significant factor in the high-energy environment of the earliest stage of the universe, and general relativity on its own fails to make accurate predictions.
The timeline of the Universe lists events from its creation to its ultimate final state. For a timeline of the universe from the present to its presumed conclusion, see: Timeline of the far future; Chronology of the universe; Timeline of the universe
Big Bang nucleosynthesis predicts a primordial abundance of about 25% helium-4 by mass, irrespective of the initial conditions of the universe. As long as the universe was hot enough for protons and neutrons to transform into each other easily, their ratio, determined solely by their relative masses, was about 1 neutron to 7 protons (allowing ...
The CMB is landmark evidence of the Big Bang theory for the origin of the universe. In the Big Bang cosmological models, during the earliest periods, the universe was filled with an opaque fog of dense, hot plasma of sub-atomic particles. As the universe expanded, this plasma cooled to the point where protons and electrons combined to form ...
Gamow's work led the development of the hot "big bang" theory of the expanding universe. He was the earliest to employ Alexander Friedmann's and Georges Lemaître's non-static solutions of Einstein's gravitational equations describing a universe of uniform matter density and constant spatial curvature. Gamow's crucial advance would provide a ...