
2
First Law—The E = Mc
2
of
Thermodynamics
There is a tendency, particularly among physicists, to view the first law of thermody-
namics as merely a consequence of the energy conservation principle of mechanics.
That is to some extent a valid perspective today, when atomism has been firmly es-
tablished and when thermodynamics is seen as the effective description of a very
large number of these microscopic constituents in terms of a very few macroscopic
thermodynamic degrees of freedom. But such a perspective would hardly have been
justified at the times (middle of 19th century) when the first law was established.
At that time, atomism was only a conjecture, ...