Pieter Zeeman (1865–1943) was a Dutch physicist whose discovery that a magnetic field splits the spectral lines of light — a phenomenon now known as the Zeeman effect — earned him the 1902 Nobel Prize in Physics, shared with his mentor Hendrik Lorentz.[1]
Early life and education
Pieter Zeeman was born on 25 May 1865 in Zonnemaire, a village in the Dutch province of Zeeland, the son of a Lutheran minister. He studied physics at Leiden University under Heike Kamerlingh Onnes and Hendrik Lorentz, two of the leading physicists of the era, and completed his doctorate in 1893. He remained at Leiden for several years as a lecturer before moving to Amsterdam.[2]
The Zeeman effect
In 1896 Zeeman investigated whether a strong magnetic field could influence the light emitted by a glowing substance. Placing a sodium flame between the poles of a powerful electromagnet, he observed that its characteristic spectral lines broadened and, under higher resolution, split into distinct components. Lorentz supplied a theoretical explanation based on his electron theory, and the effect confirmed that charged particles were responsible for the emission of light within atoms. The magnitude of the splitting allowed an estimate of the charge-to-mass ratio of these particles, in agreement with the electron identified soon afterward.[1]
Nobel Prize and later career
For this work Zeeman and Lorentz jointly received the 1902 Nobel Prize in Physics.
In 1900 Zeeman was appointed professor at the University of Amsterdam, where he continued research into magneto-optics, the propagation of light in moving media, and precise measurements bearing on the theory of relativity. A dedicated laboratory, later named the Zeeman Laboratory, was built for his experiments.[2]
Legacy
The Zeeman effect became an essential tool across physics and astronomy, used to measure magnetic fields in the Sun and other stars and providing early evidence for the internal structure of the atom, later fully accounted for by quantum mechanics and electron spin. Zeeman received numerous honours, including the Rumford Medal, the Henry Draper Medal, the Matteucci Medal and the Franklin Medal, and he was elected a Foreign Member of the Royal Society. He died in Amsterdam on 9 October 1943.[1]
