An alternate universe, also known as a parallel universe or multiverse, refers to a hypothetical reality that exists alongside our own. In these universes, the laws of physics, history, or even the fundamental nature of existence may differ from what we experience. This concept is often explored in science fiction, where characters might travel between these different realities. The idea of alternate universes is rooted in theories in physics, such as quantum mechanics and string theory. These theories suggest that multiple outcomes can occur simultaneously, leading to the possibility of countless variations of our universe. This intriguing notion raises questions about fate, choice, and the nature of reality itself.