Entropy shown by dissipation. Entropy is a measure of the amount of order or disorder in a system, as well as how reversible a change is. This is illustrated here by a heap of objects (lower right) being scattered and spread outwards (upper left), a process that is difficult to reverse randomly through thermodynamic processes. The change is from order to disorder. However, the increase in entropy here is not as much as when a wellordered object is broken, as less ordering is needed to recreate the pile than (for example) a broken cup.