What came before the Big Bang?

Why does a big bang have to be a beginning? Paul Steinhardt and collaborators propose that there are bangs bangin’ all the time, as our universe rattles around in a fifth dimension (whoa) our puny minds cannot even perceive. All of space and time as we know it sits on a four-dimensional surface called a brane. Sometimes it collides with another universe’s brane, and the smash creates bursts of energy we know as the big bang—energy still detectable as cosmic background radiation. As the universes move farther and farther apart in the fifth dimension, our cosmos expands. The cycles of collision and separation go on forever in a psychedelic dance. Many cosmologists don’t think we’ll ever find proof of this fifth dimension, but the idea that the big bang isn’t the real beginning has no end in sight.