The Cosmic Black-Body Radiation and the Existence of Singularities in Our Universe

A recent theorem on the occurrence of space-time singularities is discussed. It is shown that observa- tions of 30 K black-body background radiation indicate that the Universe contains a singularity if the general theory of relativity holds, if the energy-momentum tensor obeys a reasonable inequality, and if causality is not violated. The possible nature of the singularity is discussed