Heinrich Hertz

By Julien Moreau

Heinrich Hertz proved Maxwell right — generated invisible waves in a laboratory, measured them, and died at thirty-six never knowing he had invented the wireless age.

Born in 1857 in Hamburg, Hertz was the brightest young physicist of Helmholtz's Berlin school, a prodigy in both theory and experiment who seemed destined to lead German physics for decades. In 1886, as professor at Karlsruhe, he set out to test Maxwell's prediction that oscillating electric charges radiate waves. His apparatus was disarmingly simple: a spark gap transmitter — two brass knobs across which sparks jumped — and a loop of wire with a tiny gap as receiver. When the transmitter sparked, sparks appeared in the receiver across the room, with no connection between them. He had generated and detected electromagnetic waves.

Then he did what only a great physicist would: he measured them. He showed the waves reflect, refract, polarize, and interfere exactly like light — proving they were the same phenomenon at a different frequency — and measured their velocity as the speed of light, closing the loop Maxwell had opened on paper. Maxwell's theory was confirmed in full; the electromagnetic spectrum was opened at the long-wavelength end. Hertz also discovered the photoelectric effect while studying the sparks — ultraviolet light knocking electrons from metal, the phenomenon Einstein would later explain with Planck's quanta, closing another loop he never saw.

Asked about the practical use of his waves, Hertz answered famously: none — "it's of no use whatsoever." He moved to Bonn, fell ill with a painful bone condition, endured operations, and died in 1894 at thirty-six. Within a decade Marconi was sending his waves across the Atlantic. Hertz's name marks the unit of frequency: every radio station, every Wi-Fi signal, every heartbeat of the wireless world is counted in hertz — the waves he found useless.

Impact on civilization

Hertz proved electromagnetic waves exist and behave like light — the experimental confirmation of Maxwell's theory and the birth of radio science. His spark-gap experiments opened the electromagnetic spectrum beyond visible light and made wireless communication conceivable; Marconi, radio, radar, television, satellite links, and Wi-Fi all descend from his Karlsruhe laboratory. The hertz — the unit of frequency — counts every oscillation of the modern wireless world in his name, from power grids to gamma rays — the whole spectrum, counted in Hertz.