Heinrich Hertz

Heinrich Rudolf Hertz was a German physicist who changed our understanding of the physical world.

Born on 22 February 1857 in Hamburg, he was the son of a lawyer and politician. Hertz showed a great talent for many subjects during his early schooling. He studied sciences and engineering in several German cities, including Dresden, Munich, and Berlin. By 1880, he earned his Ph.D. from the University of Berlin. He later served as a professor at the University of Karlsruhe and the University of Bonn.

His work provided the first physical proof for theories that had previously only existed as mathematical equations.

In 1864, the Scottish physicist James Clerk Maxwell proposed a theory of electromagnetism. Maxwell used equations to predict that electric and magnetic fields could travel through space. He called these traveling fields electromagnetic waves. Maxwell also suggested that light itself was a type of electromagnetic wave with a short wavelength. However, no one had been able to generate or detect these waves before. For many years, scientists could not prove if these waves actually existed in the air. Hertz took on the challenge of turning these mathematical ideas into observable reality.

In the autumn of 1886, Hertz discovered a way to build a testing apparatus. He noticed that discharging a Leyden jar into a Riess spiral produced a spark in another coil. This observation allowed him to build a transmitter and a receiver. His transmitter was a dipole antenna made of two one-meter wires. These wires had a spark gap between their inner ends and zinc spheres at the outer ends. He used a Ruhmkorff coil to apply high voltage pulses of about 30 kilovolts.

These pulses created standing waves of current that radiated electromagnetic waves into the space around them.

To catch these waves, Hertz used a resonant single-loop antenna. This receiver had a tiny micrometer spark gap between its ends. When the waves hit the loop, a spark would jump across the gap. Through these experiments, Hertz proved several key facts about these waves. He showed that they were transverse waves, meaning they move perpendicular to their direction of travel. He also measured their velocity and found it was equal to the velocity of light. By doing this, he proved that light and these new waves were both forms of electromagnetic radiation. These findings confirmed that Maxwell's equations were correct.

Beyond electromagnetic waves, Hertz made other significant scientific discoveries. He helped establish the photoelectric effect through his observations in 1887. He noticed that a charged object lost its charge more easily when hit by ultraviolet radiation. He saw that a glass panel would block this radiation and reduce the spark in his receiver. However, a quartz panel did not block the radiation, so the spark remained strong. This showed that light could influence the movement of electrons. He also studied cathode rays and demonstrated they could pass through thin metal foils like aluminum.

In the early 1880s, Hertz also contributed to the field of contact mechanics. This is the study of how solid objects behave when they touch and press against each other. He used observations of Newton's rings to understand how pressure is distributed. He looked at how a glass sphere exerts pressure when placed on a lens. His work provided a foundation for later theories regarding how materials react under a load. Even though his work on contact mechanics was separate from his work on electricity, it remains a vital part of physics.

It is remarkable that Hertz did not realize the massive impact of his work. He once stated that his discovery was of "no use whatsoever." He believed he had simply proven that Maxwell was right about the existence of waves. He did not foresee how these waves could be used for technology. However, his proof led to an explosion of new research. Before 1910, these were often called "Hertzian waves." Only six years after his experiments, Guglielmo Marconi began developing wireless telegraphy. This work eventually led to the modern radio communication systems we use today.