The Nature of Physical Theory: A Study in Theory of Knowledge

By Victor F. Lenzen | Go to book overview

CHAPTER IX
THE ELECTRODYNAMIC CONCEPTION OF NATURE
A. MICROSCOPIC ELECTRODYNAMICS

1. INTRODUCTION

IN the mechanical conception of nature the fundamental physical phenomenon is that of a material body in motion. The fundamental concepts are of space, time, mass and mechanical force. Mechanical force has been conceived of as an action at a distance between bodies, or as an action by contact of material bodies. The mechanical theory was the canonical system of the nineteenth century; contemporary physics, however, is largely guided by an electrodynamic conception of nature.

Electrodynamics is the study of electric charges and of the electromagnetic field which is excited by the charges. Like mechanical phenomena, electrodynamic processes occur in space and time. An electrically charged body has position in space and is surrounded by an electric field. Electric charges in motion constitute an electric current which excites a magnetic field. An electromagnetic field is a physical condition which is propagated throughout space with a finite velocity in accordance with laws expressed by Maxwell's equations. Thus the fundamental concepts of electrodynamics are of space, time, electric charge, electric field, etc. In place of mechanical force we have the concept of a force which arises from the action of the electromagnetic field upon the electric charges of bodies. The program of an electrodynamic conception of nature is the interpretation of all physical properties and phenomena in terms of the concepts of electrodynamics.

A first step in the development of a unitary electromagnetic theory of physics was the recognition of the fundamental reality of the electromagnetic field. We have seen that an

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