(Hamburg, February 22, 1857 - Bonn, 1 January 1894), the German physicist.
Thanks to an apparatus of his invention, the Hertz dipole, capable of emitting radio waves, he was able to prove the existence of electromagnetic waves;
That is why the international system of frequency is measured in hertz.


Family and studies


Hertz was born in Hamburg, in a family of Jewish roots: His father, Gustav Ferdinand Hertz, was a jew lawyer converted to Christianity, a senator and head of the administration of justice in 1887; his mother, Anna Elisabeth Pfefferkorn, was the daughter of a Doctor of Frankfurt. After attending a private technical school, Heinrich continued his studies privately. He graduated in 1875 at the Johanneum in only one year, and that’s how he was able to enter into university. He moved to Frankfurt to gain practical experience in engineering and, after completing his military service in Berlin in a railway regiment (1876-77), he attended one year at the University of Monaco. He chose a career in science, rather than engineering, but in fact, while attending university in Berlin in 1878,  he showed a certain aptitude for sciences and languages (he was also learning Arabic and Sanskrit). In Berlin he was a student of Hermann von Helmholtz and Kirschhoff and graduated in 1880 magna cum laude in 1880. The subject of his thesis was the electromagnetic induction in rotating spheres ..

After graduating he continued working with Helmholtz until 1883 when he obtained the position of reader in theoretical physics at the University of Kiel. In 1885 he received the professorship at the University of Karlsruhe, Hertz is at the same time the one who discovered the electromagnetic waves, and the one who clarified and expanded the electromagnetic theory of light formulated by Maxwell in 1884. Following a first experiment conducted by Michelson in 1881 (forerunner of the more famous Michelson-Morley experiment of 1887) that excluded the existence of the aether, he reformulated Maxwell's equations to take account of this new discovery.
Through an experiment he showed that electrical signals can be sent through the air, as already predicted by James Clerk Maxwell and Michael Faraday, and so laid the groundwork for the invention of radio.

A reserved man, unassuming and seemingly little ambition, Hertz thought that his discoveries were not of any practical use, although in reality they would lead to the development of wireless telegraphy, radio, television, radar and mobile phone. It is interesting to recall that in 1887 Hertz also accidentally discovered the photoelectric effect, while maintaining his research on electromagnetism. "There is no kind of use," Hertz responded to his students when asked about the usefulness of his discovery "it is just an experiment that demonstrates that Maxwell was right. We have these mysterious electromagnetic waves that we can not see with the naked eye, but they are there."

Also in 1887 accidentally discovered the photoelectric effect, while maintaining his research on electromagnetism (whose theoretical explanation was later elaborated by Albert Einstein), noting that electrically charged objects would lose their charge when exposed to ultraviolet light.
After several years of poor health, in the summer of 1892, Hertz was hit by a bone disease (granulomatosis Wegenere) and died of septicemia in Bonn on 1 January 1894, at the age of 36. He was buried in the Jewish cemetery of Ohlsdorf and after only 5 years, the city dedicated him a street in Hamburg. Under the Nazis, his bas-relief, one of the 56 prominent citizens of Hamburg that adorned the columns of the entrance of the Town Hall was secretly removed, together with those of the other "Jewish portraits". All these bas-reliefs were replaced in 1949.