The concept of distance between two "worlds" (nowadays you use the world "world" instead of "universe" because, as has been pointed out, there can only be one universe) is irrelevant. In most theories of the multiverse (I say most because there are multiple theories), the "space" inbetween the different worlds is more of a topological space, so there is no distance, just relationships. There are also "many worlds" (ie multiverse) theories in which every world exists at the instance of the collapse of the wave function of a particle, and the particle exists in all of the worlds, meaning it travels every possible path. I'm sure you've heard of this, because it is a popular subject in pop science books. Anyways, Feynmann used this idea to describe the wave function propagator, and, amazingly enough, it describes the way the universe works. So, even though you might not believe it, it has been shown by experiment to be a possible correct theory.