For centuries, humanity believed the universe was a single, self-contained stage. One set of physical laws. One beginning. One reality unfolding in a predictable cosmic order. Every major scientific revolution—from Newton to Einstein to quantum mechanics—expanded our understanding of how the universe works, but not how many universes there might be. Now, quietly and without dramatic headlines or cinematic explosions, a series of quantum simulations has reopened one of the most unsettling questi...