The universe is accelerating. A mysterious energy is pushing apart space itself, like a crazed toddler blowing up the cosmic balloon. Unless "the" universe is actually only one of many universes. Cosmologists are seriously entertaining that possibility. In the big bang that started our universe, little bits of space might have pinched off, said physicist Steven Weinberg of the University of Texas. Each pocket universe could have different features. In one-ours-the improbable cancellation of most of the cosmological constant would have occurred, leaving just enough to explain the dark energy. As for why we happen to be living in that improbable universe, that's easy: only this feature allows galaxies to form and life to emerge.
In 'Dark Energy,' Cosmic Humility