WHAT IS AN ELEMENTARY PARTICLE?
INDIVIDUALAtomism in its latest form is called quantum mechanics.It has extended its range to comprise, besides ordinary matter, all kinds of radiation, including light-in brief, all forms of energy, ordinary matter being one of them.In the present form of the theoiy the "atoms" are electrons, jorotons, photons, mesons, etc.The generic name is elementary particle, or merely particle.The term "atom" has very wisely been retained for chemical atoms, though it has become a misnomer.This essay deals with the elementary particle, more particularly with a certain feature that this concept has acquired-or rather lost in quantum mechanics.I menn this : That the elementary particle is not an individual; it cannot be identified, it lacks "sameness."The fact is known to every physicist, but is rarely given any prominence in surveys readable by nonspccialists.In technical language it is covered by saying that the particles "obey" new-fangled statistics, either Einstein-Bose or Fermi-Dirac statistics.The implication, far from obvious, is that the unsuspected epithet "this" is not quite prop- erly applicable to, say, an electron, except with caution, in a restricted sense, and sometimes not at all.My objective here is to explain this point and to give it the thought it deserves.In order to create a foil for the discussion, let me summarize in sections 2-5 what we are usually told about particles and waves in the new physics.2. CURRENT VIEWS: THE AMALGAMATION OF PARTICLES AND WAVES Our image of the material world had been made up of two kinds of "fittings"-waves and particles.The former were instanced mainly, if not exclusively, by Maxwell's waves of electromagnetic energy, comprising such as are used in radio, light, X-rays, and gamma-rays.Material bodies were said to consist of particles.One
WORLD SCIENTIFIC eBooks•May 1, 1985•13 citations