Dynamic Interpretation of the Second Law of Thermodynamics

March 29, 2015

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Kent W. Mayhew

   “In the late 1860’s, both Boltzmann and Clauisus attempted to derive the second law of thermodynamics from mechanics, an approach known as the dynamical interpretation of the second law.  In this approach, the dynamics of individual molecules were followed in hope that this would ultimately lead to an understanding of the origin of the second law.

     Maxwell refuted this approach as a matter of principle because of the simple but powerful argument that Newton’s laws of motion, and indeed Maxwell’s equations for electromagnetic field, are completely reversible. Consequentially the irreversibility implicit in the second law cannot be explained by dynamical theory. It became believed that the second law could only be understood as a statement based upon a statistical analysis of an immense number of molecules”: From book by Longair (1) 

   I find the above quite interesting. Certainly if those formulating the foundations of thermodynamics only realized that not only does mechanical work generally require an expanding system i.e. a higher pressure system that expands in order to do work. But that such an expansion also displaces our atmosphere i.e.  lost work by expanding systems, then all these complex arguments  could have been avoided. Which is to say that the second law as written in term of entropy i.e. or if you prefer an immense number of particles, is no longer required

Certainly lost work explains why so many useful expanding systems here on Earth are irreversible.

 please see my blog on the second law

1) M.S. Longair . “Theoretical Concepts in Physics: An alternative View of Theoretical Reasoning in Physics”   Cambridge University Press  2003