Entropy always increases over time within a closed system, except in idealized interactions that leave entropy unchanged, which are not practically possible. From what we know, the only thing that might actually be a true closed system is the universe. If you&#x27;ve identified some system that has decreased in entropy, then you&#x27;ve failed to notice something outside of it that has increased in entropy by a greater amount.<p>Is it possible that our understanding of entropy is flawed? Yes. But unless you have some novel physics experiment or mathematical model to share with us, I&#x27;ll stick with the second law of thermodynamics.<p>&gt;<i>But this does not by itself imply entropy of the system increased. The reason is the system got to a non-equilibrium state which has no macroscopic thermodynamic description and no unique way to assign entropy and detect its changes.</i><p>Entropy <i>is</i> the tendency to equilibrium. Your earlier statement, that entropy is only a measure of systems that are in equilibrium, is false. If you were right, entropy would be a totally meaningless notion because there are no closed systems and true equilibrium (as opposed to the near-equilibriums that we work with in practical terms) can only exist in one.