Cosmology is the study of the whole universe—how it evolved, what its constituents are, and how it will look and behave in the future. To do this, we must understand gravity and the physics of particles, heat, and work. When we combine our best understanding of these, we get the Standard Big Bang Model (SBBM). This gives us a picture of the history of the universe, which is depicted to the left. This picture of the universe makes several predictions about the current universe, which have been validated by observation; these include

• the relative abundances of the light elements [1]. The BBM predicts, for example, how much helium should exist in comparison to how much hydrogen;

• the expansion of the universe. The SBBM predicts that, in a universe with matter and radiation, the universe will expand [6];

• the Cosmic Microwave Background [2]. The SBBM predicts that we should find a background radiation left over from about 380,000 years after the Big Bang. We observe this, no matter where we look in the universe.