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At this stage of the development of atomic theory, Wolfgang Pauli made a decisive contribution through his discovery in 1925 of a new law of Nature, the exclusion principle or Pauli principle. The 1945 Nobel Prize in Physics has been awarded to Pauli for this discovery.
- Overview
- Education and training
- The birth of quantum mechanics
- Swiss years
- Exile and return
Wolfgang Pauli (born April 25, 1900, Vienna, Austria—died Dec. 15, 1958, Zürich, Switz.) Austrian-born physicist and recipient of the 1945 Nobel Prize for Physics for his discovery in 1925 of the Pauli exclusion principle, which states that in an atom no two electrons can occupy the same quantum state simultaneously. Pauli made major contributions to quantum mechanics, quantum field theory, and solid-state physics, and he successfully hypothesized the existence of the neutrino.
In addition to his original work, he wrote masterful syntheses of several areas of physical theory that are considered classics of scientific literature. An even deeper influence was left by his personal interactions with other scientists, as recorded by numerous testimonies and a vast but never dull extant correspondence.
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Pauli was raised among the intellectual elite of Vienna, a highly cosmopolitan city that was one of the most important centres of scientific advancement at the turn of the 20th century. Pauli’s godfather and mentor was the physicist-philosopher Ernst Mach, for whom he was given one of his middle names. Pauli later wrote that Mach’s influence in his upbringing was an “anti-metaphysical baptism.”
Having demonstrated outstanding mathematical abilities—Pauli taught himself the then new theory of relativity in his gymnasium years and published his first paper on the subject when he was 18—he enrolled in physics at the University of Munich, where he studied the most advanced physics of the day: the Bohr-Sommerfeld quantum theory of the atom, under Arnold Sommerfeld. Pauli distinguished himself not only for his brilliance but also for his exacting rigour and impertinent witticisms. A review of the theory of relativity that he wrote for Encyklopädie der mathematischen Wissenschaften (“Encyclopedia of Mathematical Sciences”) in 1921 gained him early fame and high praise from Albert Einstein.
With Pauli’s return to Hamburg in 1924 as a lecturer, he participated in the creation of quantum mechanics. He first solved (1924–25) certain vexing difficulties in the theory of atomic spectra by the introduction of a new quantum number—a quantity that was later called spin but that Pauli, in accordance with his philosophical rejection of visualizable models, called “a two-valuedness not describable classically.” He concluded that if a quantum state so defined was occupied by one electron, it was excluded for other electrons. This rule was eventually incorporated in the quantum mechanics of multiparticle systems and elevated to a principle, the exclusion principle. It thus became the foundation of the Fermi-Dirac statistics, the branch of quantum statistics developed by Italian physicist Enrico Fermi and English physicist P.A.M. Dirac, of quantum chemistry, and of the quantum theory of solids. In addition to this and other results in quantum mechanics, quantum field theory, and the theory of magnetism, Pauli assisted the work of others with his critical input. (He later came to be called the “conscience of physics” for his critical insights.) His analysis of the philosophical foundations and methodology of physics played a central role in the so-called Copenhagen interpretation of quantum mechanics, based on the renunciation of causality and on the affirmation of the positivist notion that physical concepts must be limited by the possibilities of observation.
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In 1928 Pauli obtained a professorship at the Swiss Federal Institute of Technology (Eidgenössische Technische Hochschule, or ETH) in Zürich, a position that he kept for the rest of his life and from which, together with German physicist Gregor Wentzel of the University of Zürich, he created a successful “school” of theoretical physics. The suicide of Pauli’s mother in 1927 and the end of his marriage with the Berlin dancer Käthe Deppner in 1930 led him to psychoanalysis, first as a therapy (an analyst was recommended to him by the Swiss psychologist Carl Gustav Jung) and then as a philosophical interest. He studied Jung’s ideas and their import on the scientific understanding of the physical world, which led him to distance himself from positivism. Although Pauli ended two years of personal therapy with Jung in 1934, when Pauli married Franciska (Franca) Bertram, the two men developed an extensive correspondence through the following years concerning physics and psychology.
In 1930 Pauli conjectured the existence of neutral particles (later called neutrinos) to preserve the conservation of energy in nuclear beta decay. (Experimental detection of the neutrino did not come until 1956.) His analysis of symmetries in quantum field theory resulted in the formulation in 1940 of the spin-statistics theorem, which established a necessary connection between the spin of a particle and its statistical properties.
The outbreak of World War II and the possible threat of Nazi persecution (Pauli’s paternal grandparents were Jews) led him to accept a visiting professorship in 1940 at the Institute for Advanced Study in Princeton, N.J., U.S., where he worked mainly on meson theory. Although he became an American citizen in 1946, he went back to Europe that year, first to finally accept his 1945 Nobel Prize and then to return to his former position at ETH in Zürich. Back at ETH he worked on renormalization in quantum electrodynamics, in collaboration with his students, and on the CPT (charge, parity, time) symmetry in quantum field theory. He finally became a Swiss citizen in 1949.
In his later years Pauli’s involvement with philosophy intensified, while travels and epistolary exchanges kept alive his dialogue with Einstein, Bohr, and others. A rich correspondence with Jung, as well as several publications, testify to Pauli’s ongoing quest to understand “physis and psyche as complementary aspects of the same reality.”
- The Editors of Encyclopaedia Britannica
In 1925, Wolfgang Pauli introduced two new numbers and formulated the Pauli principle, which proposed that no two electrons in an atom could have identical sets of quantum numbers. It was later discovered that protons and neutrons in nuclei could also be assigned quantum numbers and that Pauli’s principle applied here too.
In 1945, after having been nominated by Albert Einstein, Pauli received the Nobel Prize in Physics for his "decisive contribution through his discovery of a new law of Nature, the exclusion principle or Pauli principle".
Feb 13, 2024 · Wolfgang Pauli left an indelible mark in the world of physics with discoveries that shaped how we understand the fundamental aspects of the universe. His work waved a beacon for future scientific explorations, influencing fields ranging from quantum physics to solid-state physics.
Dive into the remarkable journey of Wolfgang Pauli, the visionary physicist who reshaped our understanding of the quantum world. From the groundbreaking Excl...
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Wolfgang Pauli - Nobel Lecture. W O L F G A N G P A U L I. Exclusion principle and quantum mechanics. Nobel Lecture, December 13, 1946. The history of the discovery of the « exclusion principle », for which I have received the honor of the Nobel Prize award in the year 1945, goes back to my students days in Munich.
