than antiquarks, even if it started out with equal numbers of each. As we have seen, GUTs allow quarks to change into anti- electrons at high energy. They also allow the reverse processes, antiquarks turning into electrons, and electrons and anti- electrons turning into antiquarks and quarks. There was a time in the very early universe when it was so hot that the particle energies would have been high enough for these transformations to take place. But why should that lead to more quarks than antiquarks? The reason is that the laws of physics are not quite the same for particles and antiparticles.
Up to 1956 it was believed that the laws of physics obeyed each of three separate symmetries called C, P, and T. The
symmetry C means that the laws are the same for particles and antiparticles. The
