For the present I will limit myself to quoting the following result: if we imagine the same quantity, which in the case of a single body I have called its entropy, formed in a consistent manner for the whole universe (taking into account all the conditions), and if at the same time we use the other notion, energy, with its simpler meaning, we can formulate the fundamental laws of the universe corresponding to the laws of the mechanical theory of heat in the following simple form:
1. The energy of the universe is constant.
2. The entropy of the universe tends to a maximum.
Rudolph Clausius in Annalen der Physik, 125 (1865)
In this chapter we tum our attention to the entropy ...