Big Bang<br />From Wikipedia, the free encyclopedia<br />Jump to: navigation, search<br />For other uses, see Big Bang (disambiguation).<br /> <br />According to the Big Bang model, the universe developed from an extremely dense and hot state. Space itself has been expanding ever since, carrying galaxies (and all other matter) with it.The Big Bang is the cosmological model of the universe whose primary assertion is that the universe has expanded into its current state from a primordial condition of enormous density and temperature. The term is also used in a narrower sense to describe the fundamental "fireball" that erupted at or close to an initial timepoint in the history of our observed spacetime.[1]<br /><br />Theoretical support for the Big Bang comes from mathematical models, called Friedmann models. These models show that a Big Bang is consistent with general relativity and with the cosmological principle, which states that the properties of the universe should be independent of position or orientation.<br /><br />Observational evidence for the Big Bang includes the analysis of the spectrum of light from galaxies, which reveal a shift towards longer wavelengths proportional to each galaxy's distance in a relationship described by Hubble's law. Combined with the assumption that observers located anywhere in the universe would make similar observations (the Copernican principle), this suggests that space itself is expanding. The next most important observational evidence was the discovery of cosmic microwave background radiation in 1964. This had been predicted as a relic from when hot ionized plasma of the early universe first cooled sufficiently to form neutral hyrogen and allow space to become transparent to light, and its discovery led to general acceptance among physicists that the Big Bang is the best model for the origin and evolution of the universe. A third important line of evidence is the relative proportion of light elements in the universe, which is a close
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