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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.
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 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 "Big Bang" scenario, with cosmic inflation and standard particle physics, is the only cosmological model consistent with the observed continuing expansion of space, the observed distribution of lighter elements in the universe (hydrogen, helium, and lithium), and the spatial texture of minute irregularities (anisotropies) in the CMB radiation.
A simple machine is a mechanical device that changes the direction or magnitude of a force. [1] In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. [2] Usually the term refers to the six classical simple machines that were defined by Renaissance scientists: [3] [4 ...
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.
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Cosmic time, or cosmological time, is the time coordinate used in the Big Bang models of physical cosmology. [ 1 ] : 315 This concept of time avoids some issues related to relativity by being defined within a solution to the equations of general relativity widely used in cosmology.