ABSTRACT
This chapter analyses the rise of thermodynamics, the kinetic theory, its application to gases and statistical generalization by Boltzmann, and the developments leading up to Planck's radiation law. It considers how Einstein formulated then wielded what he termed "Boltzmann's principle" in demonstrating the quantum hypothesis was here to stay. The development of the concept of energy in the 1830s and 1840s and the new thermodynamics around 1850 set the stage for the kinetic theory of gases by the end of the 1850s. In defining the entropy of a thermodynamic state by the measure of its probability, Boltzmann extended the second law beyond the domain of pure thermodynamics into statistical mechanics. In 1895, Planck embarked on a highly ambitious program to tackle the riddle of blackbody radiation, the puzzle of why any object regardless of composition, maintained at constant temperature, emits the same exact spectrum of radiation.
