The Robertson-Walker metric gives mathematical expression to three widely-held assumptions about the nature of the observable universe. It is shown that the null-geodesic of this metric has little-known solutions for the speed and distance of a light-signal relative to its source. Some implications of these results are considered, the most interesting of these being that only in a universe whose 3-space is Euclidean (k = 0) will the behaviour of light on the cosmological scale be compatible with .our understanding of light behaviour on the local scale. It is shown in an Appendix that the derived implications of the metric are entirely consistent with Special Relativity, its underlying principles and its consequences.