Heinrich Rudolf Hertz | Biography

Heinrich Hertz, best known for his work with electromagnetism and electromagnetic radiation, was born in Hamburg, Germany, on February 22, 1857. He initially studied engineering, but abandoned that subject to take up physics at the University of Berlin. At Berlin he studied under physicists Gustav Kirchhoff and Hermann Helmholtz. After Hertz received a Ph.D. in 1880, he became Helmholtz's assistant and began what became a lifelong friendship.

In 1883, while working at the University of Kiel, Hertz became especially interested in the electromagnetic equations that had been established by James Clerk Maxwell. The Berlin Academy of Science had established a prize for work on a specific problem, and Helmholtz encouraged Hertz to submit an entry. Hertz was interested, but lacked the facilities to carry out the experiments. Fortunately, he was offered a professorship in physics at Karlsruhe in 1885, a post that included a very well-equipped laboratory. Hertz began his work and ultimately took the prize, but what he discovered in the process went well beyond his expectations.

To solve the Berlin Academy problem, Hertz had to delve into the matter of oscillating electric currents. He bent a copper wire into a loop and left a small gap between the two ends. He connected this to a circuit, discharged an induction coil into it and was rewarded with a spark jumping the gap. Attaching spheres to the ends of the gap, he passed an electric current backward and forward, causing each sphere alternately to become charged. When the charge reached a specific level, the spark jumped.

Realizing that Maxwell had predicted electromagnetic radiation with an extremely long wavelength should be emitted by such an oscillating charge, Hertz wondered if these invisible waves were being generated by his spark. To see if this was so, he devised a simple test. He reasoned that in the same way an oscillation current in his loop created radiation, the radiation produced might set up an oscillating current in another loop. He bent a wire into another loop to serve as a " detector"--and he was able not only to detect the radiation, but to determine the shape and intensity of the invisible waves by moving the receiving loop around the room. He found the wavelength of the " Hertzian waves" was 2.2 feet (66 cm) which was a million times greater than the wavelength of visible light. Hertz had detected a new type of radiation--the radio wave--and shown that it behaved in accordance with Maxwell's theory. In England, physicist Sir Oliver Lodge (1851-1940) confirmed Hertz's conclusions.

Hertz was also the first to notice that under certain conditions, electrical flow could be affected by light. He had observed that shining an ultraviolet light on the negatively charged side of the gap in his loop made it easier for a spark to jump the gap, but there was no body of theory Hertz could call upon to make sense of this. It was not until the age of quantum physics that Albert Einstein explained this phenomenon, called the photoelectric effect.

Hertz's discovery paved the way for the age of radio, television, and satellite communication. Within forty years scientists such as Alexsandr Popov (1859-1906), Lodge, Guglielmo Marconi (1874-1937), and Vladimir Zworykin (1889-1982)had learned how to carry Morse code, sound and even moving pictures on radio waves.

Unfortunately Hertz did not live to see even radio become a major factor in communication. Plagued with ill-health for most of his life, he died of a chronic blood disease on New Year's Day, 1894, at the age of thirty-six. The term "hertz," designating one single vibration or cycle per second, is named in his honor.