ABSTRACT

In 1900, Planck applied the concepts of statistical mechanics to the phenomenon of black body radiation to resolve the ultraviolet catastrophe, and thus opened the door to the development of quantum physics. The Feynman theory of quantum electrodynamics is a particle-based theory. The Feynman rules, the definitions and arrangements of vertices and propagators, can be derived from the Lagrangians of quantum field theory. The Feynman diagrams and associated rules are a short-hand version of quantum field theory. The focus has gone from electromagnetic fields of Faraday and Maxwell, to the particles of Planck and Einstein and then to quantum fields where particles are, in effect, localised amplitudes in their corresponding field. Although originally applied to electrons and photons, and then to the quantum fields of other fundamental particles, Feynman’s sum over histories is being used to model the evolution of the universe.