Heinrich Hertz proved radio waves exist and saw no use for them
Between 1886 and 1889 Heinrich Hertz generated and detected invisible electromagnetic waves, confirming a prediction by James Clerk Maxwell. He considered it purely a test of theory with no practical value. Within six years Guglielmo Marconi was building wireless telegraphs on the same waves, and the unit of frequency now bears Hertz's name.
Hertz was born in Hamburg in 1857, the son of a lawyer and politician, and as a schoolboy showed a gift for languages as well as science, even learning Arabic. He studied in Dresden, Munich and Berlin, where his teachers included Gustav Kirchhoff and Hermann von Helmholtz. After his 1880 doctorate he spent three years as Helmholtz's assistant, then lectured at Kiel before becoming a full professor at Karlsruhe in 1885.
Maxwell's equations of 1864 predicted that linked electric and magnetic fields could travel through space as waves, and that light was one such wave. Nobody had made or caught any. In 1879 Helmholtz set a Berlin prize for experimental evidence of a related effect and urged Hertz to try, but Hertz saw no way to build the apparatus. The prize expired unclaimed in 1882.
The opening came at Karlsruhe in 1886, while playing with a pair of flat wire spirals: emptying a charged Leyden jar through one of them caused a spark across the other. He built a transmitter from two one-metre wires with a spark gap between them and zinc balls on the ends, driven by pulses of around 30,000 volts, and a receiver that was a simple wire loop with a tiny gap. Bouncing waves off a zinc plate about 12 metres away created standing waves roughly 4 metres long. From them he showed the waves moved at the speed of light and could be reflected and polarised like light.
Asked what the discovery was good for, he said essentially nothing; it simply showed Maxwell had been right. His waves were known as Hertzian waves until around 1910, when the name radio waves took over. Not every experiment worked out: in 1883 he wrongly concluded cathode rays carry no charge, because his electrodes were screened, as J. J. Thomson later showed. Hertz became director of the physics institute at Bonn in 1889 and died on New Year's Day 1894, aged 36.
Source: Heinrich Hertz
