  Causal Dynamical Triangulations in four dimensions provide a
background-independent definition of the sum over space-time geometries in
nonperturbative quantum gravity. We show that the macroscopic four-dimensional
world which emerges in the Euclidean sector of this theory is a bounce which
satisfies a semiclassical equation. After integrating out all degrees of
freedom except for a global scale factor, we obtain the ground state wave
function of the universe as a function of this scale factor.
