Section 12.1 Introduction
Cosmology is the study of the origins of the cosmos, that is, the history of the universe. The present standard model of cosmology is the subject of this chapter.
At the end of Chapter 11, we claimed that the temperature and available energy in the early universe were sufficient to achieve universal symmetry. In this chapter we present a simple relation that shows how energy and temperature decrease with time. We then look in detail at each of the major events that served to mark transitions from one phase of the universe to another. We'll learn why these events occurred when they did, and what ramifications these events had for the interactions that followed. And finally we'll see what observational evidence exists that could test the microscopic theories of particle physics.