ABSTRACT
This chapter considers more modern approaches in which counts of galaxies, and of clusters of galaxies, are used to provide statistical information about their distributions on the sky and to catalogue prominent structures. To obtain the spatial correlation function ξ (r) directly requires three-dimensional positional information on the galaxy distribution. To study the uniformity of the galaxy distribution more carefully requires deeper surveys. One can look at the results of the major galaxy surveys in two ways: either as a way of delineating the large-scale structures or as data for a statistical analysis. The early redshift surveys showed linear structures which appear to line up on the galaxy. The chapter shows how observations of features in the temperature of the cosmic background radiation on various scales provide constraints on models of galaxy formation. It summarizes the formation of structure in a baryonic Universe. The effect of dark matter on structure formation depends upon its temperature at decoupling.
