Think about radio, and what often ... Maxwell also boldly postulated that such waves travelled at the speed of light. In the late 1880s, German physicist Heinrich Hertz tested Maxwell's theory.

(Heinrich Herz, for whom the units hertz and megahertz are named, had discovered and first produced radio waves in 1888.) Marconi jumped right on the problem. He began experimenting at his family ...

In the 1880s Heinrich Hertz discovered that a spark jumping between two pieces of metal emits a flash of light—rapidly oscillating electromagnetic waves—which can be picked up by an antenna.