ABSTRACT
This chapter takes up some unfinished business. The modern era in cosmology can be divided into two parts. First, the isotropic Universe, in which the discovery of the high degree of isotropy confirmed the applicability of the expanding big-bang models. Second, the present anisotropic era, in which it is precisely the departures from isotropy that are the relics from which we hope to reconstruct the details of our past. The Universe is approximately homogeneous and isotropic, but not exactly so. In homogeneous anisotropic models at any point the Universe is expanding at different rates in different directions. The most direct way of determining the degree of anisotropy in the Universe is through the cosmic background radiation. The rotation of the Universe is of historical interest because it provided Einstein with what he called Mach's principle which was a seminal influence in the development of relativistic cosmology.
