Editing Second law of thermodynamics (section)

=== Planck's statement ===
[[Max Planck]] stated the second law as follows.
:: Every process occurring in nature proceeds in the sense in which the sum of the entropies of all bodies taking part in the process is increased. In the limit, i.e. for reversible processes, the sum of the entropies remains unchanged.<ref name="Planck 100">[[Max Planck|Planck, M.]] (1897/1903), p. 100.</ref><ref name="Planck 463">[[Max Planck|Planck, M.]] (1926), p. 463, translation by Uffink, J. (2003), p. 131.</ref><ref name="Roberts & Miller 382">Roberts, J.K., Miller, A.R. (1928/1960), p. 382. This source is partly verbatim from Planck's statement, but does not cite Planck. This source calls the statement the principle of the increase of entropy.</ref>

Rather like Planck's statement is that of [[George Uhlenbeck]] and G. W. Ford for ''irreversible phenomena''.

:: ... in an irreversible or spontaneous change from one equilibrium state to another (as for example the equalization of temperature of two bodies A and B, when brought in contact) the entropy always increases.<ref>[[George Uhlenbeck|Uhlenbeck, G.E.]], Ford, G.W. (1963), p. 16.</ref>