  We suggest that the cosmic microwave background (CMB) temperature correlation
function C(theta) as a function of angle provides a direct connection between
experimental data and the fundamental cosmological quantities. The evolution of
inhomogeneities in the prerecombination universe is studied using their Green's
functions in position space. We find that a primordial adiabatic point
perturbation propagates as a sharp-edged spherical acoustic wave. Density
singularities at its wavefronts create a feature in the CMB correlation
function distinguished by a dip at theta ~ 1.2 deg. Characteristics of the
feature are sensitive to the values of cosmological parameters, in particular
to the total and the baryon densities.
