IEEE Circuits and Systems Magazine - Q1 2023 - 79

Pioneers in CAS
Heinrich Hertz
H
einrich Rudolf Hertz discovered in 1887 the electromagnetic
waves experimentally. Independent
of Oliver Heaviside and Josiah Willard Gibbs,
he formulated Maxwell's equations in the form known
today. Therefore, Hertz became one of the founders of
wireless communications although he never was interested
in engineering aspects of his discovery. He was an
eminent scientist who worked in many physical areas.
Especially, he opened the door to the research of atomistic
models of matter and the special relativity theory.
Hertz was born at Hamburg, Germany, in February 22,
1857. He received his abitur at Gelehrtenschule des Johanneums
and in 1874 he began to study civil engineering
at the Dresden University of Technology but he concentrated
himself to mathematics and exact natural sciences.
After his military service, Hertz concluded his studies in
1877 at Technical University of Munich. One year later
he changed to the Friedrich-Wilhelms-University (since
1945 Humboldt-University) of Berlin and studied with
Hermann von Helmholtz and Gustav Kirchhoff and tried
to solve a problem that was given by Helmholtz, who formulated
an award task for the Prussian Academy of Sciences.
At this time Hertz was not successful and in 1880
he obtained his doctor's degree with the thesis " About
the induction in rotating balls " (Über die Induktion in
rotierenden Kugeln). In 1881, his research moved to the
area of elastic and plastic deformations of bodies and
published his first paper.
After Hertz had moved to University of Kiel in 1883, he
extended his results of his 1881 paper and he received
his habilitation (academic teaching license) with a thesis
" About the contact of solid elastic bodies " (Über den
die fester elastischer Körper). In 1886, Hertz became the
successor of Karl Ferdinand Braun at Karlsruhe Institute
of Technology where he began with his experimental
research of electromagnetic waves. The stimulus to this
work was again Helmholtz's award task of the Prussian
Academy of Science. At first Hertz studied induction phenomena
in isolators and the propagation speed electromagnetic
effects along a wire where he found standing
waves. He published his results in the Annalen der Physik
in 1887 and 1888, respectively. Eventually, he discovered
electromagnetic wave in the free space and its reflections,
Digital Object Identifier 10.1109/MCAS.2023.3234728
Date of current version: 12 April 2023
FIRST QUARTER 2023
and finally Hertz studied these waves with dipoles and parabolic
mirrors and published his results in 1888. By means
of his studies Hertz showed that light waves and electromagnetic
waves are consubstantial and therefore he confirmed
Maxwell's theory of electromagnetics. He finished
this period of working with his 1889 paper " The forces of
electric oscillations, treated according to Maxwell's theory "
(Die Kräfte elektrischer Schwingungen, behandelt
nach der Maxwell'schen Theorie). Subsequently, Hertz
became one of the Maxwellians (George F. FitzGerald,
Oliver Heaviside, and Oliver Joseph Lodge). Additionally,
Hertz studied other areas of physics; e.g., in 1887 he discovered
the external photoelectric effect. Hertz was not
interested in the applications of his discovery of electromagnetic
waves in wireless communications. The civil
engineer Huber asked Hertz in a letter in 1889, whether
electromagnetic waves can be used for wireless telegraphy;
Hertz gave him a negative answer. In 1889, Hertz followed
Rudolf Clausius as a professor at the University of
Bonn, Bonn, Germany, and published the last two papers
" About the basic equations of electrodynamics of resting
bodies " (Über die Grundgleichungen der Elektrodynamik
ruhender Körper) and " About the basic equations of electrodynamics
for moving bodies " (Über die Grundgleichungen
der Elektrodynamik für bewegte Körper). With his
second paper, the problem was not solved by Hertz, but it
opened the door to theory of relativity of Albert Einstein.
Furthermore, he discovered in 1892 the passage of cathode
radiation through thin metal layers. This research
area was proceeded by Philipp Lenard who received the
Nobel prize for his discoveries in 1905. In 1894, Hertz's
fundamental monograph about the new foundations of the
principles of mechanics was published.
Heinrich Hertz died in Bonn in January 1894 at the
age of almost 37 years of sepsis.
The hertz (symbol: Hz) is the derived unit of frequency
in the International System of Units (SI) and is
defined as one cycle per second. It is named after Heinrich
Rudolf Hertz, the first person to provide conclusive
proof of the existence of electromagnetic waves.
Prepared by Professor Wolfgang Mathis, Professor
Emeritus, Leibniz Universität Hannover, Hannover, Germany
(Email: mathis@tet.uni-hannover.de).
(continued on page 78)
IEEE CIRCUITS AND SYSTEMS MAGAZINE
79
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