2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/12021Cosmologies that match in a volume averaged sense need not generally have the same light propagation behaviors. In particular a universe with inhomogeneity may not demonstrate the Friedmann-Robertson-Walker distance-redshift relation even after volume averaging to FRW spacetime. Even the Dyer-Roeder prescription for incorporating inhomogeneity within a universe equivalent to FRW in an angle averaged sense does not guarantee FRW behavior in general. To legitimately use the FRW distance-redshift relation to interpret observations, the physical conditions must match in a line of sight sense (defined herein: most observations do), since light probes the mass distribution or geometry on all length scales.9 pages, 0 figures, corrected referencesAstrophysicstext