Hertz Makes Electromagnetic Waves Measurable

In the autumn of 1886 at the Technische Hochschule in Karlsruhe, Heinrich Hertz noticed that discharging a Leyden jar through a Riess spiral produced an unexpected spark across a second, disconnected spiral. The unintended spark provided Hertz with an experimental path toward testing the theoretical framework developed by Scottish physicist James Clerk Maxwell two decades earlier. Maxwell had calculated that coupled electric and magnetic fields propagated through space as transverse waves traveling at the speed of light, yet his equations lacked empirical verification beyond visible radiation.

Hertz had considered testing Maxwell’s theory years earlier in Berlin under Hermann von Helmholtz. In 1879, Helmholtz had established a Prussian Academy of Sciences prize for empirical verification of electromagnetic action across polarizable insulators. Hertz had initially deemed an experimental apparatus unfeasible, turning instead to electromagnetic induction for his doctoral thesis. After securing his professorship in Karlsruhe, the observation involving the coupled spirals led him to build a practical transmitter and receiver.