Big Bang inflation. Conceptual artwork of several areas of inflation (domes) in the early universe. The term Big Bang describes the expansion of all the matter in the universe from an infinitely compact, high-temperature state 13.7 billion years ago. The inflationary theory proposes that during the extreme conditions in the Big Bang, conditions known as a false vacuum created a repulsive force that caused an incredibly rapid expansion, much faster than the ordinary expansion observed today. This accounts for the uniformity of the background radiation that is a remnant of the Big Bang. Rapid inflation could form separate 'bubble' universes.