Origins I: From the arrow of time to the first quantum field

Abstract

This chapter traces the origins of quantum theory, which goes back to the classical physics of the final quarter-century of the 1800s. During this time, the three pillars of classical physics — Newtonian mechanics, electromagnetic theory, and thermodynamics — stood as precise descriptions of natural phenomena, each apparently unassailable in its natural domain of applicability. However, natural phenomena requiring the simultaneous application of more than one of these formal structures began to demand the attention of physicists. The history of thermal radiation is discussed, with particular attention to those aspects important for understanding the conceptual origins of quantum field theory. The story leads continuously from the early arguments surrounding the role of the Second Law of Thermodynamics (and the ‘arrow of time’ it implies) in blackbody radiation, to the appearance of the first truly quantum-field-theoretical analysis of electromagnetic radiation.