Oskar Klein
Oskar Benjamin Klein (15 September 1894 – 5 February 1977) was a Swedish theoretical physicist known for ideas that helped shape quantum mechanics and theories of space.
He was born near Stockholm, the son of the chief rabbi of Stockholm. As a young student he studied with renowned scientists and briefly planned to go to France before World War I interrupted his plans. In 1917 he began working with Niels Bohr in Copenhagen, and he earned his doctoral degree at the University College of Stockholm in 1921.
Klein held several important academic posts. He became a professor at the University of Michigan in 1923, then returned to Europe in 1925, spending time in Copenhagen and Leiden before becoming a professor at Lund University in 1926 and later at Stockholm University College in 1930, a position he held for many years. He retired as professor emeritus in 1962 and received the Max Planck Medal in 1959 for his work.
Klein’s most famous contribution is the Klein-Gordon equation, introduced in 1926. This is the relativistic version of the equation that describes how quantum fields behave, especially for scalar particles like pions. Another major idea he championed is part of the Kaluza-Klein theory: the possibility that extra dimensions exist beyond the familiar three of space and one of time, but are curled up so small that we do not notice them—an idea that later became central to string theory.
In 1938 Klein proposed a boson-exchange model to explain weak nuclear interactions, a precursor to later theories such as Yang–Mills. His work helped lay foundations for quantum field theory and for thinking about hidden dimensions in the universe.
Oskar Klein passed away in Stockholm in 1977. His legacy continues in the annual Oskar Klein Memorial Lecture and in the Oskar Klein Centre for Cosmoparticle Physics, both established in his honor.
This page was last edited on 3 February 2026, at 08:33 (CET).