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Heinrich Hertz
1857–1894 · Physicist
A German physicist who experimentally demonstrated the electromagnetic waves predicted by James Clerk Maxwell, laying essential groundwork for later radio technology.
Why is this scientist famous?
Experimentally demonstrated electromagnetic waves in the late 1880s, confirming key predictions of James Clerk Maxwell's electromagnetic theory. The unit hertz (Hz) is named after him.
Heinrich's story
Early Life
Heinrich Rudolf Hertz was born in Hamburg, Germany, into a prosperous Jewish family that had converted to Christianity. His father was a lawyer and later a senator in the city government. From an early age Heinrich showed extraordinary ability in mathematics and science, but he was also remarkably practical — he enjoyed building things with his hands and took up carpentry and metalwork as hobbies. He studied at universities in Munich and Berlin under some of the greatest physicists of the age, including Hermann von Helmholtz and Gustav Kirchhoff, who quickly recognised his exceptional talent.
The Electromagnetic Challenge
By the 1880s, James Clerk Maxwell's theory of electromagnetism was the most tantalising unsolved problem in physics. Maxwell had predicted that oscillating electric charges should produce waves that travel through space at the speed of light, and that light itself was just such a wave. But no one had ever detected these waves. Proving Maxwell right would require generating electromagnetic waves deliberately and detecting them — a feat that seemed beyond the capabilities of any laboratory. Hertz, now a professor at the Karlsruhe Institute of Technology, decided to try.
The Spark That Changed Everything
In 1887 Hertz built a simple but brilliant apparatus: a spark-gap transmitter that produced high-frequency electrical oscillations, and a wire loop with a small gap that acted as a receiver. When he triggered a spark at the transmitter, he observed a tiny spark jumping across the receiver's gap — even though the two devices were not connected by any wire. He had generated and detected electromagnetic waves travelling through free space. Over the following months he meticulously measured their properties: they could be reflected, refracted, polarised, and they travelled at the speed of light, exactly as Maxwell had predicted. Hertz's experiments provided powerful experimental confirmation of Maxwell's prediction that electromagnetic waves exist and share important properties with light.
A Scientist's Philosophy
Hertz was a perfectionist who valued elegance and clarity above all. When asked about the practical applications of his discovery, he reportedly said he did not think the waves would have any practical use — he had been testing a theory, not inventing a technology. This was not naivety but a reflection of his view that fundamental science was worth pursuing for its own sake. His work was driven by curiosity about the laws of nature, not by any desire to build devices. Within a decade of his death, experimenters including Guglielmo Marconi were developing practical wireless-telegraphy systems using electromagnetic waves, showing how fundamental research can lead to unforeseen technologies.
Tragic Early Death
Hertz's career was cut tragically short. In 1892 he began suffering from severe headaches and was diagnosed with an incurable illness. He continued writing despite his illness. His collected electromagnetic investigations appeared in German in 1892, followed by the authorised English translation Electric Waves in 1893. He died in Bonn on 1 January 1894, at the age of just 36. After his death, collections of his scientific papers were published under the editorship of the physicist Philipp Lenard. Though his active research career lasted barely ten years, his impact on physics was enormous.
Legacy
In 1930 the International Electrotechnical Commission named the unit of frequency — the hertz, representing one cycle per second — in his honour. Every radio station, every Wi-Fi router, every mobile phone, every microwave operates on frequencies measured in hertz. Hertz proved that invisible waves could travel through the air, and in doing so he opened the door to the entire age of wireless communication. He never imagined the world his discovery would create, but he built its foundation with his spark-gap apparatus in a Karlsruhe laboratory.
What did they discover?
Proof of Electromagnetic Waves
In experiments carried out in 1887–1888, Hertz generated and detected electromagnetic waves and showed that they could be reflected, refracted and polarised, providing experimental confirmation of key predictions of Maxwell's theory.
The Photoelectric Effect
During his electrical experiments, Hertz observed that ultraviolet light made electrical sparks easier to produce. Later researchers developed this observation into the study of the photoelectric effect, which Einstein explained using light quanta in 1905.
Measurement of Wave Properties
Hertz showed that electromagnetic waves could be reflected, refracted and polarised and measured their propagation, demonstrating their close relationship to light.
'Electric Waves' (Book)
His 1893 book 'Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity Through Space' collected his experimental results and became a foundational text for the new field of wireless physics.
Amazing facts
Hertz died at just 36 years old from a degenerative illness, never living to see his discovery lead to radio, television, and every wireless technology that followed.
He reportedly said, 'I do not think that the wireless waves I have discovered will have any practical application.'
While studying electrical sparks, Hertz observed that ultraviolet light affected electrical discharge, an early observation connected with the photoelectric effect.
The unit of frequency — the hertz (Hz), one cycle per second — was named in his honour in 1930.
Hertz was an accomplished craftsman who built all his own experimental apparatus by hand, including the spark-gap transmitter and receiver that detected electromagnetic waves.
His wife Elisabeth never remarried and spent years after his death editing and publishing his unfinished papers to preserve his scientific legacy.
Timeline
Born in Hamburg, Germany
Completed his doctorate under Hermann von Helmholtz at the University of Berlin
Appointed professor of physics at the Karlsruhe Institute of Technology
Carried out experiments generating and detecting electromagnetic waves
Published experiments demonstrating key properties of electromagnetic waves and confirming Maxwell's predictions
Began suffering from the illness that would prove fatal; continued working from his sickbed
The authorised English translation Electric Waves was published; the original German collection had appeared in 1892
Died in Bonn, aged 36
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Albert Einstein
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Guglielmo Marconi
1874–1937 · Electrical Engineer and Inventor
Developed practical wireless telegraphy systems, demonstrated long-distance radio communication and shared the 1909 Nobel Prize in Physics for contributions to wireless telegraphy.
