The Rotation and Distortion of the Universe

Abstract

The isotropy of the microwave background is used to place upper limits on the large-scale anisotropics of the Universe. This is done by considering the behaviour of the microwave background in all types of spatially homogeneous models that could reasonably represent our Universe. If the Universe is closed, we find that it is rotating at a rate of less than 3 × 10 ⁻¹¹ second of arc/century if the microwave background was last scattered at a redshift of about 7 and less than 2 × 10 ⁻¹⁴ second of arc/century if the last scattering was at a redshift of 1000. We also calculate how far back in time the Universe must have been nearly isotropic. In the case of one extreme hyperbolic model, it seems that it could have been highly anisotropic at a redshift greater than about 4. The significance of these results for galaxy formation is briefly discussed.