The Birth of Gauge Theory

Although future historians of Physics will remember the first part of the twentieth century for the emergence of Special Relativity and Quantum Mechanics they may well judge that the most fundamental physical discoveries of the century were Einsteins theory of gravitation and the gauge-theory of the fundamental forces. These discoveries completely changed our conception of dynamics whereas Quantum Mechanics and Special Relativity changed only our ideas about kinematics. Furthermore, they showed that Geometry was not only the stage on which physics took place, but was part of the physical drama. The first appreciation of intimate relationship between geometry and physical force came, of course, with the theory of gravitation. In that case the geometry was strictly metrical. The appreciation of the intimate relationship between geometry and the other fundamental forces emerged much more slowly, partly because in those cases the geometry was non-metrical, and non-metrical geometry was itself an innovation. The process took about fifty years altogether, thirty to discover the basic structure of the fundamental forces (a structure which we now know as non-abelian or Yang-Mills gauge theory) and twenty to discover how such a theory should be applied. It is about the first thirty years of this evolution that I wish to speak here.