Superclusters and the large‐scale structure of the Universe

From the beginning of this century, study of the origin and evolution of the Universe has been informed by the Cosmological Principle: The Universe is homogeneous and isotropic. On the largest observable scale, that of the blackbody cosmic background radiation, this statement has been confirmed to a high degree of accuracy; spatial inhomogeneities in the temperature of the background radiation are less than 1 part in $104.$ On the human scale, the Principle is patently absurd. A question of considerable current interest is to ascertain on what scale the postulate breaks down. Observers have recently been working hard on mapping structure on scales of $106$ to $3×108$ light years, and theorists have been exploiting the increasingly important connections between particle physics and cosmology in an attempt to understand how these structures come to be.