Klein was born in
Danderyd outside
Stockholm, son of the chief rabbi of Stockholm, Gottlieb Klein from
Humenné in
Kingdom of Hungary, now
Slovakia and Antonie (Toni) Levy. He became a student of
Svante Arrhenius at the
Nobel Institute at a young age and was on the way to
Jean-Baptiste Perrin in France when
World War I broke out and he was drafted into the military. From 1917, he worked a few years with
Niels Bohr in the
University of Copenhagen and received his doctoral degree at the University College of Stockholm (now
Stockholm University) in 1921. In 1923, he received a professorship at
University of Michigan in
Ann Arbor and moved there with his recently wedded wife, Gerda Koch from
Denmark. Klein returned to Copenhagen in 1925, spent some time with
Paul Ehrenfest in
Leiden, then became
docent at
Lund University in 1926 and in 1930 accepted the offer of the professorial chair in physics at the Stockholm University College, which had previously been held by
Erik Ivar Fredholm until his death in 1927. Klein was awarded the
Max Planck Medal in 1959. He retired as professor emeritus in 1962. Klein discovered in 1926 the
Klein-Gordon equation, the simplest and prototypical example of
relativistic wave equation. It describes the behavior of scalar fields, such as e.g., those associated to the
pions.
Walter Gordon, independently discovered and published the equation a few months later, as well as
Vladimir Fock. The
Klein-Gordon equation is an example of
Stigler's law as it was first discovered by
Erwin Schrödinger in 1925 but not published until after Klein, Gordon and Fock's papers because Schrödinger was initially discouraged by the fact that it did not give the right
fine structure for the
hydrogen atom. Klein is also credited for inventing the idea, part of
Kaluza–Klein theory, that extra
dimensions may be physically real but
curled up and very small, an idea essential to
string theory. in
Copenhagen in 1963 In 1938, he proposed a
boson-exchange model for charge-charging
weak interactions (radioactive decay), a few years after a similar proposal by
Hideki Yukawa. His model was based on a local isotropic
gauge symmetry and anticipated the later successful theory of
Yang–Mills. Oskar Klein died on 5 February 1977 in Stockholm, Sweden. The
Oskar Klein Memorial Lecture, held annually at the University of Stockholm, has been named after him. The Oskar Klein Centre for Cosmoparticle Physics in Stockholm, Sweden is also in his honor. ==See also==