A Question of Coherence [Historical]

Electromagnetic waves were first postulated by James Clerk Maxwell (1831-1879) in 1865. To demonstrate their existence 22 years later, Heinrich Hertz (1857-1894) had to design new instrumentation that he used to carry out an experiment than had never been performed before. To detect the waves produced by his oscillating electric circuit, he used a very crude receiver, subsequently known as the Hertz resonator. This was made of a simple wire shaped in a circle with a small gap between the two ends where a spark was caused by the waves (Hertz, 1887). It was a very weak effect that Hertz could hardly observe: a very tiny spark that required a dark room and even a magnifier. Hertz, focused on pure science, asserted, "I do not think that the wireless waves I have discovered will have any practical application" (O'Connor and Robertson, 2007).