Abstract

For more than 150 years, starting with mechanical systems, the fact that certain quantities such as energy, momentum, etc. are constant in physical processes has led to an increasing number of conservation laws. With the advent of quantum physics, new conserved quantities, such as baryon and lepton numbers, have been found. In these new cases, the question of just what is being conserved arises. Moreover, it is clear that the same lack of understanding applies to the "classical" laws, since no one understands what "energy" or "momentum" really are, for example.

Recently, much emphasis has been placed on the related transformation symmetry properties, and the realization that gauge transformation symmetries are the source of certain quantum conservation laws. However, in spite of the insight this approach has provided, in no case has true understanding of "what it is" that is conserved been forthcoming. The following account suggests that, rather than the multiplicity of conservation laws now in use, a single conservation law produces all of the effects now ascribed to the many; and further, the nature of the one quantity that is being conserved is indicated.