Apparatus used by Heinrich Hertz, c 1887.
© Science Museum / Science & Society Picture Library
Model (scale 1:4). In 1888, the German physicist Heinrich Hertz (1857-1894) confirmed experimentally James Clerk-Maxwell's (1831-1879) theory of the existence of electromagnetic waves. He found that electromagnetic radiation behaved (with the exception of wavelength) like light waves. Hertz discovered that electromagnetic waves generated by an electric spark could be detected by a tuned electric circuit situated up to 20 metres away from their source. Hertz' discoveries enabled Guglielmo Marconi (1874-1937) to devise a way of using radio waves as a means of comunication in 1894. The unit of frequency of radio waves is today named after Hertz.