Is there only one universe in existence, or are there multiple universes? If, at the moment of creation or sometime after, the universe split apart, then the totality of existence would consist of numerous small universes, and the one we inhabit would be just one of many, rather than the entire cosmos. In this scenario, what lies beyond our universe would be other universes. However, what evidence supports the idea that the universe has undergone such a split? And if it has, what is the relationship between these separate universes?