The idea of parallel universes is not a simple metaphor: it is one of the many consequences that follow from cosmological observations. Space seems to have an infinite size. In such a case, everything that is possible will find some place where it becomes real, improbable though it may be. This is due to fairly consolidated physical ideas. If we consider less firm theories, we conclude that other universes may have different laws of physics. The presence of such universes would explain various aspects of our own and could resolve fundamental questions about the nature of time and the intelligibility of the physical world. Is there a copy of you...