Big Bang theory

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A scientific theory describing the origin of all space, time, matter, and energy approximately 13.7 billion years ago from the violent expansion of a singular point of extremely high density and temperature.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Astronomy, Cosmology) The theory that the known universe originated in an explosive event (the big bang) in which all of the matter and energy of the universe was contained in a single point and began to rapidly expand and evolve, starting as high-energy particles and radiation, and, as it cooled over time, evolving into ordinary subatomic particles, atoms, and then stars and galaxies. According to this theory, the four-dimensional space-time continuum which we perceive as our universe continues to expand to the present time, but it is unknown whether the expansion will continue indefinitely or eventually stop or even reverse, possibly leading to a contraction to a single point sometimes referred to as the “big crunch”. The competing “Steady-state Theory” gradually lost favor in the 1980's and 1990's. See also big bang.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (cosmology) the theory that the universe originated sometime between 10 billion and 20 billion years ago from the cataclysmic explosion of a small volume of matter at extremely high density and temperature
• noun (cosmology) the theory that the universe originated sometime between 10 billion and 20 billion years ago from the cataclysmic explosion of a small volume of matter at extremely high density and temperature