Heinrich Hertz experimentally demonstrates in 1887 at the Karlsruhe Polytechnic the existence of the electromagnetic waves theoretically predicted by Maxwell in 1865. Using spark oscillators, he detects reflection, refraction, and polarization of radio waves, confirming that light is a particular case of the electromagnetic spectrum. The unit of frequency, the hertz (Hz), bears his name. His experiments are the direct physical basis of all modern wireless telecommunications.