Ergodicity

Intuitive

A billiard ball in a rectangle with two circular ends: slight changes in initial conditions make such a big difference that eventually it could be anywhere. To be precise, we say its motion is "ergodic".

For the precise definition of "ergodic" read my diary:

(link: https://tinyurl.com/baez-bunimovich) tinyurl.com/baez-bunimovich

great example of the evolution of apparent randomness from a completely deterministic process

Yes, it sort of demystifies how that works.

https://mobile.twitter.com/johncarlosbaez/status/1023252524248137728

see also https://plus.google.com/+johncbaez999/posts/cWQ3RYLCAoi

Concrete

In this section things should be explained by analogy and with pictures and, if necessary, some formulas.

Abstract

The motto in this section is: the higher the level of abstraction, the better.

Why is it interesting?