<human>:  I have a question about a branch of mathematics called Ergodic theory. How many ergodic sets are there?
<bot>: There are infinitely many ergodic sets. Ergodic theory is a branch of mathematics that studies the behavior of dynamical systems. A dynamical system is a system that evolves over time. An ergodic system is a system that has a unique invariant measure. An ergodic set is a set that is invariant under the system.