তাপীয় সাম্যাবস্থা: সংশোধিত সংস্করণের মধ্যে পার্থক্য

One may imagine an isolated system, initially not in its own state of internal thermal equilibrium. It could be subjected to a fictive thermodynamic operation of partition into two subsystems separated by nothing, no wall. One could then consider the possibility of transfers of energy as heat between the two subsystems. A long time after the fictive partition operation, the two subsystems will reach a practically stationary state, and so be in the relation of thermal equilibrium with each other. Such an adventure could be conducted in indefinitely many ways, with different fictive partitions. All of them will result in subsystems that could be shown to be in thermal equilibrium with each other, testing subsystems from different partitions. For this reason, an isolated system, initially not its own state of internal thermal equilibrium, but left for a long time, practically always will reach a final state which may be regarded as one of internal thermal equilibrium. Such a final state is one of spatial uniformity or homogeneity of temperature.<ref>[[Max Planck|Planck, M.]], (1897/1903), p. 3.</ref> The existence of such states is a basic postulate of classical thermodynamics.<ref>[[László Tisza|Tisza, L.]] (1966), p. 108.</ref><ref>Bailyn, M. (1994), p. 20.</ref> This postulate is sometimes, but not often, called the minus first law of thermodynamics.<ref>{{Cite journal |doi = 10.1119/1.4914528|bibcode = 2015AmJPh..83..628M|title = Time and irreversibility in axiomatic thermodynamics|year = 2015|last1 = Marsland|first1 = Robert|last2 = Brown|first2 = Harvey R.|last3 = Valente|first3 = Giovanni|journal = American Journal of Physics|volume = 83|issue = 7|pages = 628–634}}</ref> A notable exception exists for isolated quantum systems which are [[Many body localization|many-body localized]] and which ''never'' reach internal thermal equilibrium.