chapotraphouse

Entropy "reverses" itself literally all the time in micro scales. All entropy means is that the likely states of a system are more likely to occur (when I phrase it that way it sounds redundant to the point of absurdity, but that actually is what it means). If you look at the interface between two identical metal lattices that can exchange electrons, the most likely state is the one where the number of electrons remains the same at both sides of the interface. But at any given time, it's possible for an imbalance to come about and for there to be a few more electrons in one side of the interface. Larger imbalances are less likely, of course, but it would even be possible for all the electrons to move to one side; there's no physical law that says that the system has to keep evolving to become more and more disordered, it's just the most likely thing to occur. For all practical considerations in timespans measured in googol years or less, it's not worth considering this for macro scale systems. But if you want to entertain the notion that time goes on infinitely, googol is a laughably small number.

If you like acollieastro's stuff I think Alpha Phoenix explains the quirks of entropy in a similar way here that you might find to be a better explanation than my comment.