ABSTRACT
The last chapter studied a universe consisting of matter and radiation, with matter dominating the universe (but radiation outnumbering matter particles) at the present time, and for almost the entire history of the universe, except for the first few dozen millennia when radiation ruled the universe. What about the earlier times? Did photons outnumber the nucleons by the same factor of 1.6 billion? Did the short era of radiation dominance start with the big bang, or was there a period in the early universe when matter’s importance equated or surpassed radiation? These are important questions, because as we have seen, the content of the universe determines its fate. The following example sets the stage for the story of our very young universe.
