Imagine a container filled with molecules connect by a fragile barrier from a container containing only a vacuum. Suddenly, the barrier is removed (or shattered). You might think that, sooner or later, all of the molecules will return to the original side.

Some people who MISUNDERSTAND Thermodynamics think that the Second Law is purely macroscopic and does not apply to the atomic domain. They are WRONG. Second Law applies on all scales: from black holes down to atomic nuclei. One reason that they believe wrongly this is that they think that, given enough time, sooner or later Second Law will be beaten by random events. The problem with this is that FOREVER IS NOT LONG ENOUGH. Even in a simple problem such as the three dimensional random walk, the vast majority of paths have NO RETURN TO ORIGIN. (see Probability by William Feller, first edition, Random Walks) The idea that, if you wait long enough, everything, no matter how improbable will occur is FALLACIOUS. Most things, like a reversal of entropy, will NEVER HAPPEN, no matter how long you wait. The problem is that the points on a possible random walk path are COUNTABLE, while the number of possible paths is UNCOUNTABLE. As the time of the problem goes to infinity, the probability of a repetition of a previous state goes to ZERO.