LARGE-SCALE INHOMOGENEITY VERSUS SOURCE EVOLUTION - CAN WE DISTINGUISH THEM OBSERVATIONALLY

We reconsider the issue of proving large-scale spatial homogeneity of the Universe, given isotropic observations about us and the possibilit y of source evolution in both numbers and luminosities. Two theorems m ake precise the freedom available in constructing cosmological models that will fit the observations. They make it quite clear that homogene ity cannot be proven without either a fully determinate theory of sour ce evolution, or availability of distance measures that are independen t of source evolution. We contrast this goal with the standard approac h that assumes spatial homogeneity a priori, and determines source evo lution functions on the basis of this assumption.