ABSTRACT
The cosmological principle essentially states that the large-scale universe is homogeneous. If general relativity is correct, spacetime is puckered and warped in an incredibly complicated way, on all scales from atoms up to at least clusters of galaxies. In cosmology it is customary as a first approximation to regard this rich detail as 'fine structure', which may be ignored when studying processes involving the universe as a whole. Optical astronomers have searched for inhomogeneity in the distribution of galaxies, and their results indicate some superclustering on scales of 30–50 Mpc. Computer models of an evolving galaxy can give some idea of how the luminosity changes, and make possible a very rough correction to the measured magnitudes. The event horizon represents the greatest distance from which outside matter could eventually affect what will happen at any given locality.
