Truly, no one knows what lies beyond the edge of the universe. Many theorists say that beyond the edge, nothing lies. In fact, it is not possible for us to cross the edge of the universe by any means. If we consider the big band model, then the edge of the universe is the point where everything begins and it has constantly been expanding. Beyond this point, nothing exists which suggests that space and time itself do not exist.
Since we are bound by the dimensions that we live in, there is no way we could walk out of these. This does not, however, imply that there is a different dimension beyond the edge. It’s just nothing at all.