Pieter Zeeman


Pieter Zeeman (Zonnemaire, May 25, 1865 – Amsterdam, October 9, 1943) was a Dutch physicist and Nobel laureate.

Zeeman was born in the Zeeland town of Zonnemaire, the son of the Reformed minister Catharinus Forandinus Zeeman (1828-1906) and Wilhelmina Worst. After the village school, consisting of one classroom, he was taught a basic knowledge of the French language by his father and was able to attend the hogereburgerschool (HBS) in Zierikzee (now part of the Pontes schools group). During his time at the HBS, he observed particularly bright northern lights, which could be seen in northern Europe in November 1882. Zeeman shared his observation with the Groningen physics teacher H.J.H. Groeneman, who published an article with a drawing about it in the magazine Nature.

Since the HBS did not offer direct access to the university, and Zeeman wanted to study mathematics and physics, he first had to take a year of supplementary education at the gymnasium in Delft. He was placed in the home of the vice principal J.W. Lely (Cornelis Lely”s brother) and received Latin and Greek as preparation for the university entrance examination.

During his stay in Delft, Zeeman came into contact with Heike Kamerlingh Onnes, from whom he would later receive instruction in mechanics. In 1885 he passed his entrance exam and was admitted to the State University in Leiden, as a student of Kamerlingh Onnes and Hendrik Lorentz. Kamerlingh Onnes was particularly impressed by Zeeman”s understanding of Maxwell”s famous book Theory of Heat. Even before his PhD, Zeeman was appointed assistant to Professor Lorentz in 1890. In 1893 he received his doctorate under Kamerlingh Onnes with a dissertation on magneto-optics: Measurements on Kerr”s phenomenon in polar reflections on iron, cobalt and nickel.

After receiving his doctorate, Zeeman worked for six months in Strasbourg with Emil Cohn at the Kohlrausch Institute where he conducted research on the propagation of electrical vibrations in liquids. He then served as a private lecturer in mathematics and physics at Leiden University before being appointed lecturer in physics at the University of Amsterdam in 1896.

In 1896, as a follow-up to his doctoral research on the nuclear effect, he initiated a study of the effect of magnetic fields on light and discovered what is now known as the sea effect, which he published in Nature and other important journals in 1897. This effect involves the phenomenon that spectral lines of an atom emitting light from an excited state split in the presence of a strong magnetic field. It is one of the proofs for the existence of quantization in the electron orbits around the atom and thus one of the indications of the correctness of quantum mechanics, which, by the way, would only be developed by Max Planck and others from 1900 onwards. A few years earlier, by the way, he managed to provide the answer to the competition on this nucleus effect organized by the Royal Dutch Society of Sciences and won the gold medal in 1892.

His discovery was an important proof of Lorentz”s theory of electromagnetic radiation. From Zeeman”s measurement results, Lorentz not only drew the conclusion that the particles responsible for light emission in atoms possessed a negative charge, but he could now also determine the ratio between the charge and the mass of the particles – quotient qm.

From that point on, Zeeman and Lorentz would jointly focus their research on the influence of magnetism on light rays. Zeeman himself investigated the splitting of spectral lines in many different substances, recording the results in a series of photographs. His work in this area was of great importance to all further research into the structure of atoms.

In 1900 Zeeman was appointed extraordinary professor of physics at the University of Amsterdam. On accepting this position, he delivered an inaugural address entitled: “Experimental investigations on parts smaller than atoms” in which the latest investigations on “important building blocks of our knowledge of nature” (the later discovered electrons) were explained. In 1908, as Van der Waals” successor, he was appointed full professor and director of the Physics Institute on Roeterseiland in the Plantage neighborhood.

Because this laboratory no longer met his requirements, he received a promise from the University of Amsterdam as early as 1914 that a new laboratory would be built for him. But because of the outbreak of World War I, Zeeman had to wait until 1923 before he could put the new laboratory “Physica” on Plantage Muidergracht into use. During the interim period Zeeman worked in the old laboratory on the optical doppler effect, an effect used in astronomy to learn more about the movement of stars. His attention was also focused on the propagation of light in moving solids.

In 1902 he shared with Hendrik Lorentz the Nobel Prize for his discovery of the sea effect. This was in response to experiments carried out by the American physicists Albert Michelson and Edward Morley. On the day of the presentation, December 10, 1902, Zeeman was ill. Therefore, Lorentz had to explain his former student”s research to the Swedish king and other invited guests. In 1912 Zeeman received the Matteucci Medal, as well as the Henry Draper Medal (1921), the Rumford Medal and the Benjamin Franklin Medal (1925). Until his death he remained active in the study of the propagation of light in media such as water, quartz and flint.

In 1932, in honor of the 350th anniversary of the Amsterdam University of Applied Sciences, and because the University of Göttingen wanted to thank the Netherlands for its great physical progress, Zeeman was made an honorary member of the University of Göttingen.

Zeeman has received many honorary doctorates from the universities of Oxford and Leuven, among others, and he has been appointed an (honorary) member of many scientific societies.

On his retirement at the age of 70, Zeeman was appointed Commandeur in de Orde van de Nederlandse Leeuw. In 1940, on the occasion of his 75th birthday, the Physica laboratory in Amsterdam, dating from 1923, was named after him. After his death on 9 October 1943, his body was laid to rest in a simple ceremony at the General Cemetery in Haarlem, not far from where Lorentz is buried.


  1. Pieter Zeeman
  2. Pieter Zeeman
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