Heinrich Rudolf Hertz

German physicist

• Born: February 22, 1857; Hamburg, Germany
• Died: January 1, 1894; Bonn, Germany

Heinrich Rudolf Hertz was a nineteenth-century German physicist. He is remembered for sending and receiving the first radio waves. Using the mathematical equations and the theoretical framework developed by Scottish physicist James Clerk Maxwell, Hertz proved that electromagnetic waves and radio waves behave in the same way as light waves.

Primary field: Physics

Specialty: Electromagnetism

Early Life

Heinrich Rudolf Hertz (HIN-rink REW-dahlf HURTZ) was born in Hamburg, Germany to Gustav F. Hertz and Anna Elisabeth Hertz, formerly Anna Elisabeth Pfefferkorn. His father was a successful lawyer and later became a senator, and his mother was the daughter of a doctor. He had four younger siblings. His father was Jewish, but converted to Lutheranism when he married his Lutheran wife. The Hertz children were raised Lutheran.

Hertz began private school at age six. He was a bright student, and his mother and his teachers pushed him hard in his studies. In addition to science, he was gifted at languages and studied Sanskrit and Arabic.

After he left private school at age seventeen, Hertz studied at home for two years with the help of tutors and his mother. After one year of schooling at the Hamburg Gymnasium, he accepted an apprenticeship at a municipal engineering office in Frankfurt, where he attended lectures at the Frankfurt Physics Club. After his mandatory year of military service, Hertz still could not decide between engineering and natural sciences.

In a letter to his father Gustav written in late 1877, Hertz describes how he ultimately decided to give up a more lucrative career in engineering in favor of the natural sciences. In the letter, he explains that studying science was the only part of his work he looked forward to, and that he had lost interest in things like building and surveying. In 1878, Hertz enrolled at the University of Munich and studied physics and mathematics with German physicist and mathematician Johann Philipp Gustav von Jolly.

Life’s Work

After beginning his studies in the natural sciences at the University of Berlin, Hertz fell under the guidance of German physicist Hermann von Helmholtz, who was researching electricity and electromagnetism at the time. Helmholtz convinced Hertz to begin working on the problem of the kinetic energy of electricity. His experiments and research were so detailed and impressive that Hertz was offered the job of assistant professor to Helmholtz, and in 1880, he began researching electromagnetism.

Eager to encourage his students to investigate one of the most important questions in physics of the day, Helmholtz challenged students at the Berlin Academy of Sciences to prove experimentally a theory posited in 1865 by Scottish physicist James Clerk Maxwell. Maxwell had demonstrated mathematically that electricity and magnetism travel at the speed of light. He believed that light itself was a form of electromagnetic wave but did not live to see his hypothesis proven experimentally. Helmholtz challenged Hertz to study the problem, but after considering the time and effort the research would require, Hertz declined. He did not think he was ready to tackle such an important problem, since it was likely to take at least three years of work.

After earning his doctorate in 1880, Hertz worked for Helmholz for three years at the Berlin Physical Institute. In that time, he published over a dozen papers on several subjects, though most of his work focused on electricity. Hertz’s career would likely have been very different if he had taken Helmholtz’s advice and spent three years working on one big problem instead of numerous smaller ones.

After three years as an assistant, Hertz decided to advance his career by moving to a smaller academic community where he might make faster progress as a professional scientist. He accepted a professorship at the University of Kiel, where he quickly became one of the university’s most popular lecturers. Because the university did not have an experimental physics laboratory, Hertz made do with a simple workshop at home. He wrote three important papers during his two years in Kiel, the last of which provided a solid foundation for his later work on electromagnetism. The paper offered a thorough analysis of Maxwell’s work; Hertz gained a deep understanding of Maxwell’s equations while researching the paper.

Eager to return to the laboratory, Hertz accepted a post at the Karlsruhe Physical Institute, which had extensive, state of the art facilities. Hertz’s stay at Karlsruhe from 1885 to 1889 was the most productive of his career, and the place where he finally returned to the challenge set by his old mentor Helmholtz. Through frequent correspondence with his former professor, Hertz began to experiment in earnest.

With the help of some of his students, Hertz constructed a simple dipole antenna capable of producing ultra-high frequency (UHF) waves, and a receiver. The Hertz antenna receiver is also called the half-wave antenna, since its length is exactly half of a wavelength. With these instruments, Hertz was able to measure the speed of radio waves. As Maxwell predicted, their speed was equal to the speed of light.

Hertz’s work was widely disseminated and embraced, but he did not live long enough to enjoy its rewards. He died of vasculitis, a blood vessel disorder, at the age of thirty-six, and was survived by his grieving mentor Helmholtz.

Impact

Hertz’s desire to prove experimentally the mathematical theories of Maxwell led him to build the first primitive radio. He made Maxwell’s elegant mathematical theories a laboratory reality, and his work shaped the direction of electromagnetism research. However, Hertz did not anticipate the commercial uses for his experiments.

Soon after the 1820 discovery of electromagnetism by Danish physicist Hans Christian Ørsted, European scientists began developing their own theories to account for the phenomena. Most of them were incorrect. In the earliest days of electromagnetic research, scientists had to start from scratch. They designed and built their own equipment and explained their theories based on their individual sets of scientific suppositions. After Hertz demonstrated the validity of Maxwell’s work, scientists could rely on his equations backed with solid experimental data to guide them in improving their understanding of the nature of electricity and light.

Although he did not live long enough to witness the full implications of his the work, Hertz’s discoveries accelerated scientific research and helped lead to the development of the telegraph and the radio.

Bibliography

Gupta, S. V. Units of Measurement: Past, Present, and Future. International System of Units. New York: Springer, 2009. Print. Reviews the history and development of scientific measurements. Includes a biography of Hertz and a discussion of his career accomplishments.

Huurdeman, Anton A. The Worldwide History of Telecommunications. New York: Wiley-IEEE, 2003. Print. Reviews two centuries of work by inventors, physicists, and engineers, as well as the development of the global telecommunications network. Includes a discussion of Hertz and his work.

Sanghera, Paul. Quantum Physics for Scientists and Technologists: Fundamental Principles and Applications for Biologists, Chemists, Computer Scientists, and Nanotechnologists. New York: Wiley Interscience, 2011. Print. Discusses the application of quantum physics to the fields of computer science, biology, chemistry, and nanotechnology. Includes a review of Hertz’s experimental work on the photoelectric effect.