One of the greatest successes of the Standard Cosmological Model consists in the excellent agreement between the theoretical prediction for the cosmic microwave background radiation anisotropics and the most recent experimental data. However, this theoretical prediction provided by the model is not a proper temperature distribution, but it is a set of statistical variables related to this distribution. One can extract from the temperature distribution a two-point correlation function, which is expanded in Legendre polynomials. The coefficients from the expansion are then compared with the theoretical prediction for the same quantity. In this paper we show in detail how these variables are built, with simple examples from simplified temperature maps, in order to highlight the main physical features that can be read from this procedure.
astronomy; cosmology; cosmic microwave background
