Coherence in the Physical World

Abstract

The term coherence is used in many connections. We often speak of coherent reasoning, coherent activities, coherent bodies, and coherent phenomena. In science this term is often used to indicate continuity of a structure in space and time. If many individuals can simultaneously observe similar sets of coherent phenomena, we infer with some justification, first, that the phenomena observed have some kind of correspondence with activities in an external world, that is, a world independent of the existence of the individual observers, and second, that the coherence itself is an attribute of the external world. In a recently published article, to which I shall make several references in this paper, I have called attention to the fact that the science of physics is based on the form and the changes in form of an immediately observed phenomenological world, called the physical world, which can be completely characterized as a structure in space and time. In his analysis of the foundations of the science of physics Eddington has clearly shown that theoretical physics deals exclusively with structures of the type described in the mathematical theory of groups, and that our knowledge of the physical world could have been reached by our sense of vision alone. Coherence in the physical world is that characteristic of the structure which describes the more or less permanent relationship between phenomena in different parts of space at approximately the same time, or a regular sequence in the changing phenomena at approximately the same region of space.