Wolfgang Ernst Pauli (April 25, 1900 – December 15, 1958) was an Austrian-American physicist noted for his work on the theory of spin.
Pauli was born in Vienna to Wolfgang Joseph Pauli and Berta Camilla Schütz. His middle name was given in honor of his godfather, the physicist Ernst Mach.
Pauli attended the Döblinger Gymnasium in Vienna, graduating with distinction in 1918. Only two months after graduation, he had published his first paper, on Einstein's theory of general relativity. He attended the Ludwig-Maximilian University of Munich, working under Sommerfeld, where he received his doctorate in July 1921 for a thesis on the quantum theory of ionised molecular hydrogen.
Sommerfeld asked Pauli to review relativity for the Encyklopaedie der mathematischen Wissenschaften, a German encyclopedia. Two months after receiving his doctorate, Pauli completed the article, which came to 237 pages. It was praised by Einstein; published as a monograph, it remains a standard reference on the subject to this day.
He spent a year at the University of Göttingen as the assistant to Max Born, and the following year at what became the Niels Bohr Institute for Theoretical Physics in Copenhagen. He then spent 1923 to 1928 as a lecturer at the University of Hamburg. During this period, Pauli was instrumental in the development of the modern theory of quantum mechanics. In particular, he formulated the exclusion principle and the theory of nonrelativistic spin. (See below for a list of his scientific contributions.)
In May 1929, Pauli left the Roman Catholic Church; in December that year, he married Käthe Margarethe Deppner. The marriage was an unhappy one, ending in divorce in 1930 after less than a year.
In 1928, he was appointed Professor of Theoretical Physics at the Federal Institute of Technology in Zurich, Switzerland. He held visiting professorships at the University of Michigan in 1931, and the Institute for Advanced Study at Princeton in 1935.
In 1934, he married Franciska Bertram. This marriage would last for the rest of his life. They had no children.
The German annexation of Austria in 1938 made him a German citizen, which became a difficulty with the outbreak of the Second World War in 1939. Pauli moved to the United States in 1940, where he was Professor of Theoretical Physics at Princeton. After the end of the war in 1945, he returned to Zurich, where he mostly remained for the rest of his life.
Also in 1945, he received the Nobel Prize in Physics for his "decisive contribution through his discovery in 1925 of a new law of Nature, the exclusion principle or Pauli principle." He had been nominated for the prize by Einstein.
Pauli died in Zürich.
Pauli made many important contributions in his career as a physicist, primarily in the subject of quantum mechanics. He seldom published papers, preferring lengthy correspondences with colleagues (such as Bohr and Heisenberg, with whom he had close friendships.) Many of his ideas and results were never published and appeared only in his letters, which were often copied and circulated by their recipients. Pauli was apparently unconcerned that much of his work thus went uncredited. The following are the most important results for which he has been credited:
In 1924, Pauli proposed a new quantum degree of freedom to resolve inconsistencies between observed molecular spectra and the developing theory of quantum mechanics. He formulated the Pauli exclusion principle, perhaps his most important work, which stated that no two electrons could exist in the same quantum state. Uhlenbeck and Goudsmit later identified this degree of freedom as electron spin.
In 1926, shortly after Heisenberg published the matrix theory of modern quantum mechanics, Pauli used it to derive the observed spectrum of the hydrogen atom. This result was important in securing credibility for Heisenberg's theory.
In 1927, he introduced the Pauli matrices as a basis of spin operators, thus solving the nonrelativistic theory of spin. This work influenced Dirac in his discovery of the Dirac equation for the relativistic electron.
In 1931, he proposed the existence of a hitherto unobserved neutral and massless particle, in order to explain the continuous spectrum of beta decay. In 1934, Fermi incorporated the particle, which he called a neutrino, into his theory of radioactive decay. The neutrino was first observed experimentally in 1959.
In 1940, he proved the spin-statistics theorem, a critical result of quantum mechanics which states that particles with half-integer spin are fermions, while particles with integer spin are bosons.
Personality and Reputation
The Pauli Effect was named after his bizarre ability to break experimental equipment simply by being in the vicinity. Pauli himself was aware of his reputation, and delighted whenever the Pauli Effect manifested.
Regarding physics, Pauli was famously perfectionist. This extended not just to his own work, but also to the work of his colleagues. As a result, he became known within the physics community as the "conscience of physics", the critic to whom his colleagues were accountable. He could be scathing in his dismissal of any theory he found lacking, often labelling it ganz falsch, utterly false. Famously, he once said of one such paper: "This isn't right. It isn't even wrong."
According to a story well known in the physics community, after his death in 1958 Pauli was granted an audience with God. Pauli asked God why the fine structure constant has the value 1/(137.036...). God nodded, went to a blackboard, and began scribbling equations at a furious pace. Pauli watched Him with great satisfaction, but soon began shaking his head violently...