COSMIC MICROWAVE BACKGROUND ANISOTROPY

The authors describe some of the current hypotheses concerning the origin of structure in the Universe, and the calculations which have been made to predict the amplitude of the microwave anisotropy. A different test of cosmological theories is provided by the dipole anisotropy of the microwave background, which arises from our motion relative to a uniformly expanding 'cosmic frame' defined by the mean state of motion of matter at great distances. The authors describe this anisotropy as extrinsic, and infer a solar motion which can be used to constrain both the large-scale density fluctuations in which we are embedded and independent determinations of our motion relative to distant galaxies.