Whether it is a bottle of soda, the tires of a car or the human body: Objects in everyday life can be described by only a few parameters, like temperature, pressure or volume. But how is this possible, if each of these systems are complex assemblies of atoms and molecules giving rise to a vast number of  coordinates, on the order of 10^23?

Ergodic theory is the mathematical attempt to provide an answer to this fundamental question. In this talk we will tackle the problem based on a prominent example - the Einstein model for a solid. It will be shown that this problem is reduced to studying rotations on a circle, for which we will prove a version of the ergodic theorem.