Heinrich Rudolf Hertz (February 22, 1857 – January 1, 1894) was a German physicist who clarified and expanded the electromagnetic theory of light that had been put forth by Maxwell. He was the first to conclusively prove[1] the existence of electromagnetic waves by engineering instruments to transmit and receive radio pulses using experimental procedures that ruled out all other known wireless phenomena. Early years Hertz was born in Hamburg, then a sovereign state of the German Confederation, into a prosperous and cultured Hanseatic family. His father, Gustav Ferdinand Hertz, was a writer and later a senator. His mother was the former Anna Elisabeth Pfefferkorn. His paternal grandfather David Wolff Hertz (1757–1822), fourth son of Benjamin Wolff Hertz, moved to Hamburg in 1793 where he made his living as a jeweller. He and his wife Schöne Hertz (1760–1834) were buried in the former Jewish cemetery in Ottensen. Their first son Wolff Hertz (1790–1859), was chairman of the Jewish community. His brother Hertz Hertz (1797–1862) was a respected businessman. He was married to Betty Oppenheim, the daughter of the banker Salomon Oppenheim, from Cologne. Hertz converted from Judaism to Christianity and took the name Heinrich David Hertz.[2] While studying at the Gelehrtenschule des Johanneums in Hamburg, he showed an aptitude for sciences as well as languages, learning Arabic and Sanskrit. He studied sciences and engineering in the German cities of Dresden, Munich and Berlin, where he studied under Gustav R. Kirchhoff and Hermann von Helmholtz. In 1880, Hertz obtained his PhD from the University of Berlin; and remained for post-doctoral study under Hermann von Helmholtz. In 1883, Hertz took a post as a lecturer in theoretical physics at the University of Kiel. In 1885, Hertz became a full professor at the University of Karlsruhe where he discovered electromagnetic waves. The most dramatic prediction of Maxwell's theory of electromagnetism, published in 1865, was the existence of electromagnetic waves moving at the speed of light, and the conclusion that light itself was just such a wave. This challenged experimentalists to generate and detect electromagnetic radiation using some form of electrical apparatus. The first clearly successful attempt was made by Heinrich Hertz in 1886. For his radio wave transmitter he used a high voltage induction coil, a condenser (capacitor, Leyden jar) and a spark gap — whose poles on either side are formed by spheres of 2 cm radius — to cause a spark discharge between the spark gap’s poles oscillating at a frequency determined by the values of the capacitor and the induction coil. To prove there really was radiation emitted, it had to be detected. Hertz used a piece of copper wire, 1 mm thick, bent into a circle of a diameter of 7.5 cm, with a small brass sphere on one end, and the other end of the wire was pointed, with the point near the sphere. He bought a screw mechanism so that the point could be moved very close to the sphere in a controlled fashion. This "receiver" was designed so that current oscillating back and forth in the wire would have a natural period close to that of the "transmitter" described above. The presence of oscillating charge in the receiver would be signaled by sparks across the (tiny) gap between the point and the sphere (typically, this gap was hundredths of a millimeter). In more advanced experiments, Hertz measured the velocity of electromagnetic radiation and found it to be the same as the light’s velocity. He also showed that the nature of radio waves’ reflection and refraction was the same as those of light, and established beyond any doubt that light is a form of electromagnetic radiation obeying the Maxwell equations. Hertz's experiments would soon trigger the invention of the wireless telegraph, radio, and later television. In recognition of his work, the unit of frequency — one cycle per second — is named the "hertz". Meteorology He always had a deep interest in meteorology probably derived from his contacts with Wilhelm von Bezold (who was Hertz's professor in a laboratory course at the Munich Polytechnic in the summer of 1878). Hertz, however, did not contribute much to the field himself except some early articles as an assistant to Helmholtz in Berlin, including research on the evaporation of liquids, a new kind of hygrometer, and a graphical means of determining the properties of moist air when subjected to adiabatic changes.[3]
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