Heinrich Rudolf Hertz (; 22 February 1857 – 1 January 1894) was a German physicist who first conclusively proved the existence of electromagnetic waves theorized by James Clerk Maxwell's electromagnetic theory of light. Hertz proved the theory by engineering instruments to transmit and receive radio pulses using experimental procedures that  ruled out all other known wireless phenomena. The unit of frequency – cycle per second – was named the "hertz" in his honor.