William Thomson[aut]Thomson, William (1824-1907) (Lord Kelvin) (later Lord Kelvin) was one of the central figures in the history of heat. He established both the principle of absolute temperature and a numerical value in 1848. He proved theoretically that Joule’s principle of the conservation of energy was true, and that heat could not be conserved in a process that produces work. Thomson showed that it was important to consider the dynamics of heat flowHeat flow in the understanding of Thermodynamics. He stated his conclusions succinctly. These statements remain true today, but are rarely included in pedagogical treatments. Thomson was also a brilliant mathematician and fully analyzed both the experimental and theoretical importance of Carnot’s function.