Clausius, one of the main founders of the modern thermodynamics, is the originator of the term “entropy,” but before this coinage he used an expression “equivalence value of transformations” instead. The term “entropy,” which is now used as a physical term, was originally economically conceived as equivalent value of exchange. Thermodynamics itself was a field of physics that was economically motivated to improve the thermal efficiency of heat engines. So, it was half physics and half economics. Apart from Clausius’s interest, the term has now become an important keyword for solving the environment and resource problems.
Oil and coal, which have brought about modern industry, are limited resources and destined to be exhausted someday. Moreover, combustion of oil or coal causes various kind of pollution. That's why the advanced nations are groping for the clean alternative energy sources since the oil crisis. There are many candidates for it, such as nuclear power, photovoltaic power, wind power, waterpower generation, but it is my considered opinion that methane is the best alternative energy sources. I'll tell you the reason for it.