The ekpyrotic model proposes that the universe has no beginning or end. Instead of a bang, what happened is thought of as a "Big Bounce", the moment at which the universe, which was slowly contracting to an incredibly, but not infinitely, small point, bounced to expansion. There is no beginning of time. Instead, our visible universe exists on one of two four-dimensional "branes" floating in a five-dimensional space.The ekpyrotic universe theory asserts that the cosmos exists as a product of an endless procession of creation, destruction and recreation. This model theorizes that the universe has been expanding and contracting repeatedly over time scales that make the 13.7 billion years that have passed since the Big Bang seem like a second.