The Cosmic Cookbook

Abstract

The asymmetry problem appeared to be solved. After matter and antimatter annihilated, only matter was left. The universe then consisted of electrons, neutrinos, photons, and a few protons and neutrons. But we know that it now contains many complex atoms—heavy elements. Where did they come from? How did they form? Gamow, as we saw earlier, was convinced that they came about as a result of collisions involving neutrons. He believed a step-by-step process occurred in the early stages of the big bang that produced all the atoms. But he was quickly stopped after helium-4 by a gap that was impossible to jump (and also at atomic mass 8).