The First Principle

The first principle of thermodynamics is considered to be one of the greatest achievements of scientific thought when heat, or the internal energy of a thermodynamic system, was recognized as a kind of mechanical energy. In this chapter, we will try to understand the main reasons that led to this outstanding discovery. We start with the main seventeenth and eighteenth century findings, from the Mariotte discovery of atmospheric pressure to James Watt steam engines. While the seventeenth century was the century of the discovery of vacuum by Pascal, the thermoscope of Galileu, the gas thermometer of the Grand Duke of Tuscany, Ferdinand II, and the discovery of the properties of elastic gases by Robert Boyle, the eighteenth century saw the born of the steam engines and the industrial revolution they produced, atmospheric gases were isolated and the Stahl phlogiston theory was overthrown by Lavoisier’s mass conservation principle. At the end of the eighteenth century, Lavoisier, controversially, also proposed the conservation of caloric principle, in the reverse sense with the principle of energy conservation sustained by important philosophers and further postulated by Helmholtz, based on the pioneer experimental works of Benjamin Thompson, Joule, and Mayer.