there was a time of loneliness, frustration and depression.
Hertz’s spirits were buoyed shortly
afterwards when he was introduced to
Elizabeth Doll—the daughter of a mathematics professor—whom he went on to
marry. The couple eventually had two
daughters together, Joanna and Mathilde.
What followed were Hertz’s most
fruitful years. He conducted his series of
experiments and their interpretation elucidating the nature of propagating electromagnetic waves. Between the years
1887 and 1888, Hertz made his seminal
finding that electromagnetic waves followed the law of geometrical optics. He
verified this experimentally and found
that such waves could be polarized and
that their refraction was in agreement
with results derived from Maxwell’s electromagnetic theory of 1864. This marked
the end of Weber’s theory of action at a
distance or the instantaneous propagation of force between charged bodies.
Antecedents to Hertz’s
electrical discoveries
As Süsskind pointed out, Hertz’s discoveries did not occur in a vacuum. Francis
FitzGerald (1857-1901) proposed, but
did not construct, a “magnetic oscillator”
that consisted of a loop of wire with a
With his doctorate in
hand, Hertz worked for
three years in Berlin as an
assistant to Helmholtz.
During this prolific
period, he published
13 scientific papers.
sinusoidal current from the discharge of a
condenser across a resistor. The oscillating
magnetic field in the wire loop was suggested as the source of radiation. Oliver
Joseph Lodge (1855-1936) conducted
experiments with waves that propagate
along a wire. William Mitchinson Hicks
(1850-1934), who worked at Cambridge
University’s Cavendish Laboratory (where
Maxwell was the director), experimented
with currents in two coils of wire that
had a magnetic needle placed between
them but not in the middle separation.
He observed an asymmetric effect on the
magnetic needle from the energized coils.
Besides these physicists, there were a
number of technically oriented investigators who came close to anticipating Hertz’s work but did not have the
[ Hertz’s spark apparatus ]
theoretical background to associate their
finding with Maxwell’s theory. In 1780,
the Italian anatomist Luigi Galvani
(1737-1798) made the prescient observation that the sparking from an electrostatic generator could cause movement
in a dead frog situated some distance
from the discharge.
Sixty-some years later, in 1843, Joseph
Henry (1797-1878) observed that a spark
discharge could magnetize needles several meters distant and proposed that the
electrical disturbance could propagate
great distances in space. In another interesting example, Thomas Alva Edison
(1847-1931), the great American inventor,
observed in 1875 that electrical sparks in
a magnetic vibrator used in electric bells
could induce sparks in a distant, overhead metal pipe that was not electrically
connected to the source of the sparks.
Edison incorrectly interpreted this observation as evidence of a new, nonelectrical phenomenon. He claimed that he
discovered a new force and named it the
“etheric force.”
Hertz’s electrical experiments
Hertz succeeded where others failed
because he had both the necessary
experimental skills to design, construct,
modify, and calibrate his instruments as
Courtesy of Deutsches Museum
June 2011 | 33
