Wikipedia:Today's featured article/February 23, 2005

Diagram of the expansion of the Universe following the Big Bang

In physical cosmology, the Big Bang is the scientific theory that concerns the early development and shape of the universe. The central idea is that the theory of general relativity can be combined with the observations on the largest scales of galaxies receding from each other to extrapolate the conditions of the universe back or forward in time. A natural consequence of the Big Bang is that in the past the universe had a higher temperature and a higher density. The term "Big Bang" is used both in a narrow sense to refer to a point in time when the observed expansion of the universe (Hubble's law) began, and in a more general sense to refer to the prevailing cosmological paradigm explaining the origin and evolution of the universe. The term "Big Bang" was coined in 1949 by Fred Hoyle during a BBC radio program, The Nature of Things. Hoyle did not subscribe to the theory and intended to mock the concept. In current physical models, the universe 13.7 billion years ago would have had the form of a gravitational singularity, at which all time and distance measurements become meaningless and temperatures and pressures become infinite. (more...)

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