Hertz’s methodology and its influence on Einstein

Hertz died at the early age of 37; nevertheless, in this short lifetime he became a leading classical physicist and an outstanding philosopher. In 1884 Hertz published a detailed and critical analysis of Maxwell’s set of equations. This major undertaking, “Über die Beziehungen zwischen den Maxwell’schen elektrodynamischen Grundgleichungen und den Grundgleichungen der gegnerischen Elektrodynamik”, preceded his famous tour de
force: proving experimentally that electric waves exist. Hertz attempted in this paper to show the validity of Maxwell’s set of equations even if one starts with the premises of opposing theories. He did not introduce the ether in his derivation of the equations, despite his belief in the reality of this hypothetical entity. He distinguished between the electric and the magnetic force, claiming, however, that each force is unified in the sense that different sources yield the same kind of force.
Hertz’s influential papers, which Einstein reported reading, are based on the idea
of interchangeability of electric and magnetic elements. Hertz explicitly characterized Maxwell’s theory as asymmetrical, a feature with which he was not satisfied. He therefore proceeded to eliminate the asymmetry between the forces. Hertz manipulated the equations for the forces of electricity and magnetism mathematically, recasting them symmetrically, thus making the two descriptions of the forces interchangeable. However, in the wake of his experimental work on electric waves, Hertz no longer accepted the
validity of his derivation of the equations; instead, he opted for the axiomatic approach, turning the equations into postulates.
Einstein’s decision to postulate the two principles of his theory of relativity of 1905 (thus giving it an axiomatic basis) is reminiscent of Hertz’s decision to postulate the equations. But this line of influence did not affect Einstein’s view of asymmetry, for it has to be removed by physical arguments, not by mathematical manipulations as Hertz had done. For Einstein indistinguishability was the key concept, not interchangeability.
Nevertheless, Hertz’s pioneering attempt to grapple with the asymmetrical nature of Maxwell’s theory formed the background against which Einstein clarified his thoroughly physical approach to the problem. Hertz was a most effective interlocutor for Einstein: in Hertz’s work Einstein found the quintessence of 19th-century physics and it served as
his point of departure for inaugurating the physics of a new era.