Poincaré recurrence theorem - Wikipedia
In mathematics and physics, the Poincaré recurrence theorem states that certain dynamical systems will, after a sufficiently long but finite time, return to a state arbitrarily close to (for continuous state systems), or exactly the same as (for discrete state systems), their initial state.
https://en.wikipedia.org/wiki/Poincar%C3%A9_recurrence_theorem
Alan Jo