Pieter Zeeman

Dutch physicist

• Born: May 25, 1865; Zonnemarie, Netherlands
• Died: October 9, 1943; Amsterdam, Netherlands

Pieter Zeeman shared the Nobel Prize in Physics in 1902 with Hendrik A. Lorentz. Zeeman is remembered for discovering that spectral lines could be split when placed in a magnetic field. This “Zeeman effect” aided in the discovery of the electron and helped lead to the development of magnetic resonance imaging, among many other advances.

Primary Field: Physics

Specialty: Optics

Early Life

Pieter Zeeman was born May 25, 1865, in the small town of Zonnemarie in the Netherlands. Zonnemarie is in the Zeeland province on the island of Schouwen, in the southeastern part of the country. Zeeman’s parents, Catharinus Farandinus Zeeman and Wilhelmina Worst, had six children: four sons and two daughters. Catharinus was a Lutheran minister. Wilhelmina home-schooled Zeeman and his siblings through elementary school. Zeeman then attended secondary school in Zierikzee, the island’s major city. Zeeman was still in high school on November 17, 1882, when a massive geomagnetic storm disrupted telegraphs and created auroras worldwide. He observed and sketched the aurora as a pale green arch that formed in the eastern sky. Zeeman sent letters with his description and drawings to the journal Nature, and they were published in 1883. After graduating, he attended school in Delft for two years, studying classical languages and reading papers by leading scientists. While there, Zeeman met physicist H. Kamerlingh Onnes, who was a pioneer in refrigeration technology and later discovered superconductivity.

Life’s Work

After passing his qualifying exams, Zeeman enrolled at the University of Leiden in 1885. Zeeman began studying physics under Onnes and theoretical physicist Hendrik A. Lorentz. Under Lorentz, Zeeman studied electromagnetism, mechanics, thermodynamics, and light. In 1890, Zeeman began working as an assistant to Lorentz in Leiden’s physics department. He was responsible for setting up the demonstrations and experiments that Lorentz used in his introductory physics courses. He also helped Lorentz with his research on the Kerr effect. The Kerr effect, discovered by Scottish physicist John Kerr, describes changes in the index of refraction of a material within an electric field. Zeeman’s paper “Mesures relatives du phénomène de Kerr” (Relative measurements of the Kerr effect) was published in 1892, and was awarded a gold medal from the Dutch Society of Sciences. Zeeman later wrote his doctoral thesis on the Kerr effect in 1893. He spent the next term at F. Kohlrausch’s institute in Strasbourg (then part of the German Empire, today in France), studying the propagation and absorption of electrical waves in fluids. Zeeman then returned to Leiden, where he became a lecturer of mathematics and physics. On March 25, 1895, he married Johanna Elisabeth Lebret in Dordrecht.

Zeeman continued to study optics, and began investigating the effect of magnetism on visible light. In 1896, he discovered that the spectral line of burning salt (sodium) divided when the flame was placed within the magnetic field created by a powerful electromagnet. The emitted radiation lines were split into lines with different wavelengths, frequencies, and polarizations. Zeeman observed and photographed the phenomenon using a concave grating with a ten-foot radius. Zeeman unveiled the results of his work on October 31, 1896, at a meeting of the Academy of Science in Amsterdam. Lorentz had predicted what happened during the experiment: that the lines would have circular polarization at the ends. Zeeman found that by reversing the magnet’s polarity, he could view both edges of the line and that they were in fact “circularly polarized” in opposite directions. Zeeman always referred to his discovery as “the magnetic splitting of the spectral lines,” though it became known as the Zeeman effect. He later published his notes in Researches in Magneto-Optics in 1913. In 1902, Zeeman and Lorentz received the Nobel Prize in Physics for their work in optics.

In 1897, Zeeman became a lecturer of physics at the University of Amsterdam. He was promoted to full professor in 1908 when he also became the director of the Physics Institute. In 1923, a new laboratory was built for Zeeman to continue his research into the magnetic splitting of spectral lines. The building was designed with temperature control and a dark room with a zig-zag entrance, which aided in improving the quality of photographic results. The lab was also designed with higher-quality grating spectrographs. The laboratory was later named for Zeeman in 1940.

Zeeman also studied the optical Doppler effect. The Doppler effect causes the wavelength of light to be shifted. For example, in astronomy, light waves from a distant galaxy moving toward the Earth will be shortened, or shifted toward the blue part of the spectrum. The light from galaxies moving away will have increased wavelengths and appear redshifted. Zeeman also investigated the propagation of light through moving media, like water, glass, and quartz. Along with one of his students, he also discovered a number of new isotopes, including argon-38 and nickel-64. Zeeman retired when he turned seventy in 1935. He and his wife had three daughters: Wilhelmina, Elisabeth, and Johanna, and one son, Jan. He died October 9, 1943, in Amsterdam.

Impact

The Zeeman effect has had a wide-ranging impact on physics and medical technology. It helped scientists better understand the mechanics of light radiation, the structure of the atom, and the behavior of the electron. Zeeman’s discovery lead to J. J. Thomson’s experiment that proved the existence of the electron. The Zeeman effect has also played an important role in various fields of spectroscopy, including electron spin resonance, atomic absorption, Mössbauer spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. Magnetic resonance imaging (MRI), the most common tool used by radiologists and doctors, would not be possible without the Zeeman effect. Other biological and medical applications include determining the presence of various chemicals like zinc, lead, cadmium, copper, and iron in blood, plasma, and urine. In addition to the Nobel Prize, Zeeman received various other awards throughout his career, including the Henry Draper Medal (from the National Academy of Sciences, 1921) and the Franklin Medal (from the Franklin Institute, 1925). He was a member of the Royal Netherlands Academy of Arts and Sciences, and held the position of secretary for eight years. He also was a member of many foreign science academies and received a number of honorary degrees.

Bibliography

Hunt, Bruce. Pursuing Power and Light: Technology and Physics from James Watt to Albert Einstein. Baltimore: Johns Hopkins UP, 2010. Print. Investigates the connection between nineteenth-century technology and advancements in modern physics. Discusses Zeeman, his discovery, and its impact.

Tipler, Paul A., and Ralph Llewellyn. Modern Physics. 6th ed. New York: Freeman, 2012. Print. Modern physics textbook designed for undergraduates. Covers the Zeeman effect in detail in mathematical and theoretical terms.

Velthuys-Bechthold, P. J. M. Inventory of the Papers of Pieter Zeeman (1865–1943), Physicist and Nobel Prize Winner: C. 1877–1946. Haarlem: Rijksarchief in Noord-Holland, 1993. Print. Inventory of the Zeeman’s papers. Includes a review of documents donated to the North Holland Archives in Haarlem.

Zeeman, Pieter. Researches in Magneto-Optics: With Special Reference to the Magnetic Resolution of Spectrum Lines. London: Macmillan, 1913. Print. Zeeman’s collection of works in magneto-optics, first published in 1913, written as a narrative. Includes chapters on spectroscope technology at the time, the effect bearing his name, issues with resolutions, circular polarization, Hale’s sunspot discovery, and Thomson’s discovery of the electron. .