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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 notion of an expanding universe was first scientifically originated by physicist Alexander Friedmann in 1922 with the mathematical derivation of the Friedmann equations.
The theory he devised to explain what he found is called the Big Bang theory. [citation needed] In 1931, Lemaître proposed in his "hypothèse de l'atome primitif" (hypothesis of the primeval atom) that the universe began with the "explosion" of the "primeval atom" – what was later called the Big Bang.
The work, which would become the subject of Alpher's PhD dissertation, argued that the Big Bang would create hydrogen, helium and heavier elements in the correct proportions to explain their abundance in the early universe. While the original theory neglected a number of processes important to the formation of heavy elements, subsequent ...
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.
The timeline of the universe begins with the Big Bang, 13.799 ± 0.021 billion years ago, [1] and follows the formation and subsequent evolution of the Universe up to the present day. Each era or age of the universe begins with an "epoch," a time of significant change. Times on this list are relative to the moment of the Big Bang.
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 ...
The Big Bang theory, which explains the Evolution of the Universe from a hot and dense state, is widely accepted by physicists. In astronomy, cosmogony is the study of the origin of particular astrophysical objects or systems, and is most commonly used in reference to the origin of the universe, the Solar System, or the Earth–Moon system.
According to the Big Bang theory, the energy and matter initially present have become less dense as the universe expanded. After an initial accelerated expansion called the inflationary epoch at around 10 −32 seconds, and the separation of the four known fundamental forces , the universe gradually cooled and continued to expand, allowing the ...