The Rationale for the Present Book Perhaps the most critical problem
facing present-day particle physicistsis to delineate the relationship
between classical and quantum systems. This relationship has many
facets. Particle-waveduality is one. The concept of the point particle
is another. And theconcept of particle mass is yet another. The
electron, as the lightest of the charged particles, represents a
fundamental "ground state", and many of the essential problems in the
murky area between the domainsofclassical and quantum physics can be
brought into focus by studyingjust this one particle. Thus the present
book is centered on questions that arise in connection with the
electron, and in particular with its mass, which has remained an
unsolved, and indeed almost unexplored, mystery. Each student ofphysics,
beginner and professional alike, has to fashion for himselfa way of
thinking about the electron. If, after reading this book, the reader
views this topic somewhat differently than before, the efforts of the
author will have been amply rewarded. When physicists were confronted
with the properties of the electron, they made a conceptualleap into the
unknown: they concluded that the electron does not obey classical laws
with respect to mechanics (as connected to the spin of the electron),
and also with respect to electrodynamics (as connected to the magnetic
moment of the electron).