the thermodynamics (and specifically the notion of &quot;heat&quot;) is just statistical&#x2F;aggregate description of the interaction between the forces which are subject to the same entropic description like the entropic gravity and obey the same 2nd law. It is not surprising once you see that &quot;minimal action principle&quot; is just the 2nd law (&quot;entropy evolves along the gradient&quot;) expressed using the language of Lagrangian in mechanics. Thus all the known forces are subject to it, ie. in addition to gravity electromagnetic forces is subject to the same, and the Schrodinger too. That allows to calculate and use entropy for the whole system along its whole evolution path.