Editing Exergy (section)

===A historical and cultural tangent===
In 1848, [[William Thomson, 1st Baron Kelvin]], asked (and immediately answered) the question

:Is there any principle on which an absolute thermometric scale can be founded? It appears to me that Carnot's theory of the motive power of heat enables us to give an affirmative answer.{{ref|kelvin1848}}

With the benefit of the hindsight contained in equation ({{EquationNote|5}}), we are able to understand the historical impact of Kelvin's idea on physics.  Kelvin suggested that the best temperature scale would describe a constant ability for a unit of temperature in the surroundings to alter the available work from Carnot's engine. From equation ({{EquationNote|3}}):

{{NumBlk|:|<math> \frac{\mathrm{d}B}{\mathrm{d}T_R}=-S </math>|{{EquationRef|5}}}}

[[Rudolf Clausius]] recognized the presence of a [[Proportionality (mathematics)|proportionality]] constant in Kelvin's analysis and gave it the name [[entropy]] in 1865 from the Greek for "transformation" because it quantifies the amount of energy lost during the conversion from heat to work. The available work from a Carnot engine is at its maximum when the surroundings are at a temperature of [[absolute zero]].

Physicists then, as now, often look at a property with the word "available" or "utilizable" in its name with a certain unease.  The idea of what is available raises the question of "available to what?" and raises a concern about whether such a property is [[Anthropocentrism|anthropocentric]]. Laws derived using such a property may not describe the universe but instead, describe what people wish to see.

The field of [[statistical mechanics]] (beginning with the work of [[Ludwig Boltzmann]] in developing the [[Boltzmann equation]]) relieved many physicists of this concern.  From this discipline, we now know that macroscopic properties may all be determined from properties on a microscopic scale where entropy is more "real" than temperature itself (''see [[Thermodynamic temperature]]''). Microscopic kinetic fluctuations among particles cause entropic loss, and this energy is unavailable for work because these fluctuations occur randomly in all directions.  The anthropocentric act is taken, in the eyes of some physicists and engineers today, when someone draws a hypothetical boundary, in fact, he says: "This is my system. What occurs beyond it is surroundings." In this context, exergy is sometimes described as an anthropocentric property, both by some who use it and by some who don't. However, exergy is based on the dis-equilibrium between a system and its environment, so its very real and necessary to define the system distinctly from its environment. It can be agreed that entropy is generally viewed as a more fundamental property of matter than exergy.