Action-at-a-Distance

Abstract

Maxwell is best known for his work on the kinetic theory of gasses and his electromagnetic theory of light. Regarding the former topic, Maxwell argued that the macroscopic properties of a gas, like pressure and temperature, may be understood in terms of the velocity distribution of the particles comprising the gas. Regarding the latter topic, Maxwell drew together disparate lines of research—from electricity, magnetism and the wave theory of light—to argue that “light is an electromagnetic disturbance in the form of waves propagated through the electromagnetic field according to electromagnetic laws.” Maxwell’s electromagnetic theory of light, presented to the Royal Society in 1864 as “A Dynamical Theory of the Electromagnetic Field,” was inspired by Faraday’s conception of electric and magnetic forces as manifestations of strains arising within a subtle medium pervading space. Underlying Maxwell’s theory is the idea that electrically charged bodies do not act upon one another immediately, that is, without any intervening medium. Rather, forces between bodies are mediated by the luminferous æther. The conflict between natural philosophers who advocated “action-at-a-distance” and those who advocated “mediated action” is the topic of the reading selection included in the present chapter. It was first published in the Proceedings of the Royal Institution of Great Britain in 1873. Whose arguments do you find most convincing?

To a person ignorant of the properties of air, the transmission of force by means of that invisible medium would appear as unaccountable.

—James Clerk Maxwell