Prof. Doug Jones
This month we are going to take a look at the man whose name is associated with frequency, Heinrich Hertz. To put his life into perspective compared to the others we have met, here is a timeline. The timeline shows that Hertz came a bit later than the others, born in 1857, and had a rather short life of only 37 years.
Heinrich Hertz was born into a rather well-to-do family in what is now Hamburg, Germany. His paternal grandfather was a wealthy Jewish businessman who married into a Lutheran family and then converted. His father was a lawyer who became a politician and his mother was the daughter of a physician. Young Heinrich was raised in the Lutheran church, but it seems as though his parents emphasized his education more than his religious development. He started school at age 6 in a private and rather progressive school for its time. The Dr. Wichard Lange School was an all-boys school that emphasized child-centered teaching methods, and while it took into account individual differences, it also promoted fierce competition amongst the students. Heinrich actually flourished in this environment and soon rose to the top of his class. However, the Lange school did not teach Latin and Greek, which were required for admission into university, but focused on math and science. At age 15, Heinrich realized that if he wanted to go to university, the program at Lange was a hindrance rather than a benefit. He left Lange, was homeschooled and received tutoring in Latin, Greek and Arabic. As it turned out, young Hertz was a brilliant student with an extraordinary talent for language. At 17 he passed his entrance exams for University. As is the case with many adolescents, his talent was tempered by his restlessness and for the next few years he tried a number of vocations rather than attending University. At the age of 20, he performed his 1 yr. compulsive military duty. When he completed his military service, Hertz decided to become an engineer and enrolled in an engineering program. A month later he decided that engineering was not for him and decided that he wanted to become a physicist. He enrolled in the University of Berlin and began working in the laboratory of the eminent scientist Hermann von Helmholtz. Helmholtz, recognizing that young Hertz was not your average student, gave him a problem he himself had struggled with. In fact, there was a rather heated debate between Helmholtz and another eminent physicist, Wilhelm Weber.
The question was “does electricity move with inertia?” Or put another way “does electric current have mass?” The debate became so heated that the University of Berlin offered a prize to anyone who could answer the question definitively. Hertz quickly became intrigued by this question, which he re-stated as “does electric current have kinetic energy?” Over the next year, Hertz established a routine of attending lectures in the morning and carrying out experiments and doing his calculations well into the evening. A year later, at age 22, Hertz won the gold medal prize. He showed through a series of incredibly sensitive experiments that if electric current has mass at all it must be extremely minute. Remember that 1879, the year in which Hertz did his research, was 18 years before
the discovery of the electron! In the next year, 1880, Hertz carried out a series of experiments on electromagnetic induction, which he submitted as his thesis for a Doctor of Physics degree, which he was awarded that year at age 23. He stayed in Helmholtz’s lab until 1883 and in those 3 years published 15 papers in various academic journals.
Hertz then accepted a position at the University of Kiel as a lecturer in mathematical physics. This was a much more theoretical rather than experimental kind of position, and that was exactly what Hertz needed! It was during his time at Kiel that he began to grapple with one of the day's most vexing problems in physics: to experimentally verify Maxwell’s theory of electromagnetism. However, the University of Kiel did not have a good enough lab to conduct the sort of experiments that Hertz wanted to try. In 1885, Hertz accepted a professorship at the University of Karlsruhe, which had one of the best labs anywhere. Now he could focus on the task of proving Maxwell’s equations experimentally. A year later, in 1886, Hertz was discussing electric sparks with his students and demonstrating different ways to create them. In the process, he noticed something very interesting. When the sparks jumped across a gap, they seemed to set up an electrical vibration in the wires leading to the gap. He realized that these vibrations were the result of rapidly changing electrical charges. If Maxwell’s theory was correct, these charges should create electromagnetic waves that could pass through air just as light does. In the fall of ’86, Hertz constructed an apparatus with a spark gap and what amounted to a resonator where the charges would bounce back and forth at about 100 million times a second. He predicted that this device would produce waves that could be detectable at a distance. Hertz then set up a loop of wire about 8 feet away, which also had a spark gap. Just as Maxwell had predicted, the electromagnetic waves traveled the 8 feet and created a spark in the loop. He had proven Maxwell to be correct! He had produced and detected what we now call radio waves. Over the next three years Hertz, went on to fully prove that these waves and light waves were all part of the same family, which we now call electromagnetic radiation.
Surprisingly, Hertz, pure theoretical scientist that he was, did not appreciate what he had discovered. He was quoted as saying “ I do not think that the wireless waves I have discovered will have any practical application.”
Of course he was very wrong, because just 10 years later Marconi applied for a patent for wireless communications and 5 years after that, in 1901, Marconi transmitted a wireless signal across the Atlantic!
Hertz married in 1886 and had two daughters; one became a very influential biologist. A few years later, Hertz became ill and died at the age of 36. In 1930, the unit of frequency was named hertz
in his honor and fully adopted by the General Conference on Weights and Measures in 1960. So, the next time you use anything wireless…. remember Heinrich Hertz. He is the one who made it possible.
Next time we will meet Faraday.