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(Hamburg, 1857 - Bonn, 1894) German physicist who discovered the propagation of electromagnetic waves in space and studied the nature and properties of them, laying the groundwork that would lead to Marconi to an invention intended to revolutionize communications: radio. In 1887, in a famous experiment, Hertz was able to transmit electromagnetic waves between an oscillator (antenna) and a resonator (receiving antenna), experimentally confirming the theories of the English physicist James C. Maxwell on the identity of characteristics between light and electromagnetic waves.
Transmitter and receiver of Hertz (1887)
In his honor are called Hertzian waves or Hertzian electromagnetic waves produced by the oscillation of electricity in a conductor, used in radio; also derives from its name the Hertz, unit of frequency that equals one cycle per second, and that is represented by the abbreviation Hz (and its multiples: kilohertz, megahertz and gigahertz). Hertz followed after investigating other scientific topics, to develop principles of mechanics (which appeared after his death, in 1894) which developed all the mechanics from the principle of least action, ignoring the concept of force.
Son of a Senator, Heinrich Rudolf Hertz started the engineering studies, but then leaned by physics, he studied in Munich and Berlin. In the latter city he graduated in 1880 and was Assistant of Hermann von Helmholtz. In 1883 was Professor in Kiel, where he began to be interested in Maxwell's electromagnetic theory. In 1885 he moved to Karlsruhe as a Professor of Physics of the Polytechnic; It remained there until 1889, and during those four years conducted research that would use her celebrity.
Some time before, Helmholtz had called his attention to a prize offering since 1879, the Academy of Sciences of Berlin, who was an experimental confirmation of the relationship between the electromagnetic actions and the polarization of a dielectric; It was to prove the existence of the "electromagnetic waves", planned and almost lines since the year 1870 by James Maxwell, by means of mathematical calculation.
Heinrich Hertz showed no interest in a beginning toward that award, as was believed impossible any analogy between such actions show. However, times were already mature enough to allow that great men could give experimental validity to a theory that was to constitute one of the bases of the physical drive, and during those same years Hendrik Lorentz, in the Netherlands, was trying to formulate a theory applicable to such kind of phenomena.
Transmitter and receiver of Hertz (1887)
But in Karlsruhe, where he could count on the appropriate instruments, Heinrich Hertz managed to prove in 1887 the propagation of electromagnetic action in space. This was served only some metal wire bent shaped ring between whose extremes was a break of just a fraction of a millimeter. When one of these rings, properly oriented in space and used as a receiving station, was invaded by a wave of electromagnetic waves, the variations of the magnetic field associated with the passage of those waves generated in the small ring induced currents of high frequency, and between the ends of the same ring jumped small sparks; such sparks revealed the passage of electromagnetic waves.
Hertz reported the results in the article very fast electrical oscillations, in the Wiedemann's Annalen (1887). Continuing his experimental research in the two following years, Hertz got measure wavelength and the velocity of propagation of electromagnetic waves, and found to speed a very approximate to that provided by Maxwell value (i.e., the speed of light: 300,000 kilometers per second). It showed that these waves are "cross-cutting", as the light, and also discovered that electromagnetic waves were given the phenomena of reflection, refraction, and polarization also.
With all the electromagnetic theory of Maxwell, made sixteen years earlier, found an experimental confirmation, and it was possible to establish the electromagnetic nature of light. Hertz made public these research in a scientific report and a lecture given in 1889 to the German society for the progress of science and medicine, in Heidelberg. In Bonn, where he had been called that same year to succeed Rudolf Clausius in the Chair of physics at the University, Hertz went on their experiences, and dealt with electrical discharges in gases.
The writings of Heinrich Hertz Assembly met in Gesammelte Werke (1894-1895), which consists of three volumes: Schriften vermischten Inhalt, Untersuchung der elektrischen Kraft and Die Principien der Mechanik. The principles of mechanics, which tried to give a new shape to the fundamental laws of this science, were his last work, as Hertz, after a long and painful illness, died when he was only thirty-seven years.
To the radio
It should be noted that rudimentary instruments employed Hertz experiments are not at all comparable to the perfect stations radio stations or recipients of our days. But already in 1894, Hertz work caught the attention of Guglielmo Marconi, a young Italian physicist of twenty years it began to design and build, as in the experiments of Hertz, issuers of waves and devices to detect them.
Marconi patiently perfected their instruments, and the distance of your transmissions was increasing steadily: at first measured it in centimeters, meters and then later in kilometers, until in 1901 he sent a signal in Morse code from England to Newfoundland, landmark which marks the effective birth of wireless radiotelegraphy. The real expansion of the radio as a means of communication, however, would come at the hands of the chemical Reginald Fessenden, Assistant to Edison. Instead of Pulsations of Morse, Fessenden had the idea of sending a continuous signal, modulating it according to the sound waves, and making thus possible the transmission of voice and music. in December 1906 he issued his first radio program.