Can we determine what other worlds there are? Is the form of the Universal Wavefunction knowable?
To calculate the form of the universal wavefunction requires not only a knowledge of its dynamics (which we have a good approximation to, at the moment) but also of the boundary conditions. To actually calculate the form of the universal wavefunction, and hence make inferences about all the embedded worlds, we would need to know the boundary conditions as well. We are presently restricted to making inferences about those worlds with which have shared a common history up to some point, which have left traces (records, fossils, etc.) still discernible today. This restricts us to a subset of the extant worlds which have shared the same boundary conditions with us. The further we probe back in time the less we know of the boundary conditions and the less we can know of the universal wavefunction. This limits us to drawing conclusions about a restricted subset of the worlds – all the worlds which are consistent with our known history up to a some common moment, before we diverged. The flow
