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The '''Second Law of Thermodynamics''' states that heat can never flow from a cold body to a warmer one. An equivalent definition is that the [[entropy]] of an isolated system cannot decrease.<ref> “Another way of stating the second [[law]] then is: ‘The universe hvgggsee is constantly getting more disorderly!’ Viewed that way, we can see the second law all about us. We have to [[work]] hard to straighten a room, but left to itself it becomes a mess again very quickly and very easily. Even if we never enter it, it becomes dusty and musty. How difficult to maintain houses, and machinery, and our bodies in perfect working order: how easy to let them deteriorate. In fact, all we have to do is nothing, and everything deteriorates, collapses, breaks down, wears out, all by itself -- and that is what the second law is all about.” Isaac Asimov, Smithsonian Institute Journal, June 1970, p. 6 </ref>