A growing number of cosmologists agree with Greene that we are but one of many universes and at least one of these other worlds lies close to ours, maybe only a millimeter away. We can't see this world, because it exists in a type of space different from the four dimensions of our everyday reality.

    MIT's Max Tegmark believes this multiverse model of 'many universes' is grounded in modern physics and will eventually be testable, predictive and disprovable. "This is not sci-fi," he says, "its real science."

    As research at the CERN Large Hadron Colliderprogresses, scientists are talking increasingly of a "new physics" on the horizon, which promise to help researchers understand more of the unknowns about our universe. This new approach includes developing a better understanding of dark energy, a mystery force that some forward thinkers believe indicates that a 'sister' universe lurks in our neighborhood.