Bubble universes. Conceptual computer artwork of several 'bubble' universes that may have formed in the early universe. Two of these universes are joined by a wormhole. All the matter in the universe expanded from an infinitely compact state 13.7 billion years ago (an event called the Big Bang). Inflationary theory proposes that during 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. Since this expansion is faster than the speed of light, areas of inflation would form bubbles that would normally be completely isolated from each other. This artwork could also represent the creation of separate universes as fluctuations in a quantum foam.