Quantum cosmology

The traditional enterprise of cosmology has been to construct a model of the universe which agrees with the authors' observations on the largest scales and which, when evolved backwards according to the laws of fundamental physics, gives a consistent historical picture of how the universe came to be the way it is today. The authors' observations tell us that the universe consists of matter and radiation. The matter that we see in galaxies is distributed roughly homogeneously and isotropically on the largest scales. The cosmic background radiation, in which we see a picture of the universe at an early stage, is remarkably isotropic. As a first approximation, we are thus led naturally to the Friedman-Robertson-Walker cosmological models in which the symmetries of homogeneity and isotropy are enforced exactly. Evolved backward in time using Einstein's gravitational theory and the laws of microscopic physics these models provide a consistent history of the universe. Among other things, they describe the evolution of the background radiation, the origin of the primordial elements, the evolution of the fluctuations which became the galaxies, and perhaps the origin of the baryons. The initial condition implied by the extrapolation is an early state in which the matter is in thermal equilibrium with high temperature and density, distributed homogeneously and isotropically but containing the seeds of condensations later to become galaxies