Cosmic birth rite

Various possibilities for testing different theories on the formation of ordinary matter are discussed. The proportions of other light elements, which were not burnt to helium-4 by the time cosmic fusion ceased, are focused to test the theory of big bang nucleosynthesis (BBN). The cosmic microwave background radiation (CMB) is a probe for the atomic age, when electrons and nuclei condensed into atoms. The spectrum of the microwaves at different positions in the sky measures the cosmic temperatures and this is a probe of densities of matter.