Max Born thought that Pauli was, perhaps, an even greater scientist than Einstein. "But he was a completely different type of man," wrote Born, "who, in my eyes, did not attain Einstein's greatness."
The "king" was, of course, the 66-year-old Einstein. His realm was physics and Pauli was his appointed heir. The occasion was a banquet in Princeton honoring Pauli, who had been awarded the prize for his discovery of the exclusion principle. In 1969, eleven years after Pauli's death, Born commented, "Since the time when he was my assistant in Göttingen, I knew he was a genius, comparable only to Einstein himself. As a scientist he was, perhaps, even greater than Einstein. But he was a completely different type of man, who, in my eyes, did not attain Einstein's greatness." 2
Who was this prince of physics whose death in 1958 went unnoticed by The New York Times? Pauli was born on 25 April 1900 in Vienna. His father was a professor of colloid chemistry at the University of Vienna and Ernst Mach, the eminent physicist and radical empiricist philosopher, was his godfather.
The genie in the goblet
We introduce Pauli by letting him speak, describing his baptismal and scientific origins in a letter to his unlikely guru, the Swiss psychologist Carl Jung. Our English translation of a small excerpt can hardly convey the literary brilliance of this 31 March 1953 letter.
In typical Paulinean fashion
Mach's godson's first publication dealt with Hermann Weyl's gauge theory of gravity and electromagnetism. As Weyl remembered it: "He dealt with it in truly Paulinean fashion--namely, he dealt it a pernicious blow."4 At age 20, Pauli had finished his magisterial account of special and general relativity, an article 237 pages long in the Encyclopedia of the Mathematical Sciences, with 394 footnotes. It remains one of the best treatments ever of the relativity theories. In a rave review, Einstein wrote, "No one studying this mature, grandly conceived work would believe that the author is a man of twenty-one. One wonders what to admire most, the psychological understanding for the development of the ideas, the sureness of mathematical deduction, the profound physical insight, the capacity for lucid, systematic presentation, the knowledge of the literature, the complete treatment of the subject matter, or the sureness of critical appraisal." 5
After Pauli's review of relativity, his main interest shifted to the quantum puzzle, to which he and his fellow student Werner Heisenberg were introduced in Arnold Sommerfeld's seminar at Munich. Pauli soon introduced the atomic magneton and named it after Niels Bohr. He worked on the anomalous Zeeman effect and he discovered nuclear magnetism. In 1925, before the Heisenberg and Schrödinger formulations of the new quantum mechanics, Pauli posited his famous exclusion principle, which explained the structure of atoms in conformity with the periodic table. Within four years, he had become the world's foremost expert on the old Bohr-Sommerfeld quantum theory.
Pauli's approach to physics was described by Heisenberg in 1968:
The creation of quantum mechanics and quantum electrodynamics in the years between 1925 and 1933 was an epiphany unique in history. It is bracketed by two review articles by Pauli in the Handbuch der Physik, known to the cognoscenti as the Old and New Testament.7 The first is an encompassing account of what was known about the microworld before the new quantum mechanics. It is a clinical review of the bewildering experiments and the desperate attempts to make sense of them. Seven years later, in the second edition of the Handbuch, Pauli gives the definitive description of the new language that physicists now use to describe all of nature. Robert Oppenheimer called it "the only adult introduction to quantum mechanics."
Instances of inspiration in this historic epiphany have become folklore:
In his essay on paramagnetism, Pauli started the modern theory of solids. Max Jammer has called attention to a remarkable footnote in that paper.8 It contains the probability interpretation of wave mechanics in a clearer and more general formulation than Born's earlier suggestion. Quantum statistical mechanics and Fermi's golden rules appear in Pauli's contribution for the 1928 Festschrift honoring Sommerfeld. In papers with Heisenberg and Pascual Jordan, Pauli introduced relativistic quantum field theory. In 1930 he proposed the existence of the neutrino.
Much of Pauli's seminal work remains unpublished. For example, his proof of the equivalence of matrix and wave mechanics appears in a letter to Jordan, and he writes down the uncertainty relation for time and energy in a letter to Heisenberg. In November 1925, when Hendrik Kramers discovers, independently of Dirac, the magic quantization key that turns Poisson brackets into commutators, the last line of his seminal paper states that "Pauli has also already pointed to this interpretation of the commutation relations." 9
Staying out of the potato race
What clearly emerges from reading the letters and papers from the incubation period of quantum mechanics is that, among the score of people creating the new picture of physics, two protagonists stand out, combining awesome mathematical power with a global awareness of the experimental data. These two--Pauli and Heisenberg--were the phenomenologists par excellence in the labyrinth of spectroscopy. They felt themselves to be the real physicists, dismissing Jordan, Dirac, Born, Schrödinger, Louis de Broglie, and others as mere formalists. (See the article about Jordan and Pauli in Physics Today, October 1999, page 26*.) The main act in the drama of the new physics is not, as Michael Frayn imagines in his play Copenhagen,10 (see Physics Today, May 2000, page 51*) the discourse between Bohr and Heisenberg, but rather the Heisenberg-Pauli dialogue. Bohr, the revered father figure, no longer had the leading role he played before 1925.
We can imagine the magnitude of the loss when we read Pauli's 12-page letter of 19 October 1926, where he adumbrates the uncertainty relations by pointing out that "one can look at the world with the p-eye and one can look at it with the q-eye. But if one wants to open both eyes at the same time, one goes crazy."11 This letter is, strange to say, not mentioned by Heisenberg in his recollections about collaborating with Pauli.12 From reading Heisenberg's responses to the missing Pauli letters, one gets the impression that much of Heisenberg's work was inspired by Pauli's ideas and suggestions.
Much of Pauli's work in his later years was centered on quantum field theory. With Victor Weisskopf, he accomplished the quantization of spin-zero fields. (See the article by Weisskopf in Physics Today, December 1985, page 36). With Felix Villars, he achieved regularization of the theory. He proved two fundamental pillars of quantum field theory: the spin-statistics theorem and the TCP theorem. Pauli anticipated the Yang-Mills theory in letters to Abraham Pais, and he introduced the degeneracy of the vacuum ground state. Both of these ideas would later find their places in the standard model of particle physics.
Matter and mind
There was another, rather bizarre side to Pauli that is only now beginning to come into view with the publication of more than a thousand letters showing his attempts to explore the unconscious and find a common language for the description of mind and matter. Jung, in his 1935 essay "Dream Symbols of the Process of Individuation," wrote: "My material consists of more than 1000 dreams and visual impressions of a scientifically educated younger man. For the purpose of the present investigation I have studied the first 400 of these dreams."13 The anonymous dreamer, as we know now, was Wolfgang Pauli.
As Jung describes one of these dreams:
The search for symmetry and harmony in the laws of Nature was the central theme of Pauli's work in physics. His attempts to find the roots of Nature's order in the human mind led him to a study of Kepler. Pauli sought to investigate the human psyche as deeply as he explored the physical world. But he did not feel ready to publish his psychic investigations. Like Newton, he saw a great ocean of truth before him. To paraphrase the poet Rainer Maria Rilke,14 he succeeded in
1. Pauli to M. Born, 25 April 1955. Pauli's scientific correspondence is published in six volumes in K. v. Meyenn, ed. Wolfgang Pauli, Wissenschaftlicher Briefwechsel, Springer-Verlag, New York (1979-2000).
2. A. Einstein/H. & M. Born Briefwechsel 1916-1955, with commentary by M. Born, Nymphenburger Verlagshandlung, Munich (1969) p. 226.
3. Pauli to C. Jung, 31 March 1953, in Ref. 1.
4. H. Weyl, Science, 103, 216 (1946).
5. A. Einstein, Naturwissenschaften 10, 184 (1922).
6. W. Heisenberg, IAEA Bulletin special supplement (1968),
7. R. Kronig, V. Weisskopf, eds., Collected Scientific Papers by Wolfgang Pauli, vol. 1, Interscience, New York (1964), p. 269, translated by P. Achuthan, K. Venkatesan in General Principles of Quantum Mechanics, Springer-Verlag, Berlin (1980).
8. M. Jammer, Naturwissenschaftliche Rundschau 37, 1 (1984).
9. D. ter Haar, Master of Modern Physics, Princeton U. Press, Princeton, N.J. (1998), p. 150.
10. M. Frayn, Copenhagen, Methuen Drama, London (1998).
11. Pauli to W. Heisenberg, 19 October 1926, in Ref. 1.
12. M. Fierz, V. Weisskopf, eds., Theoretical Physics in the Twentieth Century, Interscience, New York (1960) p. 40.
13. C. Jung, Eranos Jahrbuch 1935, O. Fröbe-Kapteyn, ed., Rhein-Verlag, Zurich (1936), p. 119.
14. R. M. Rilke, Requiem für Wolf Graf v. Kalckreuth. The original German is: "Hart sich in die Worte zu verwandeln / wie sich der Steinmetz einer Kathedrale / verbissen umsetzt in des Steines Gleichmut."
15. K. v. Meyenn, K. Stolzenburg, R. Sexl, Niels Bohr, Vieweg, Braunschweig, Germany (1985), p. 308, Translated in G. Gamow, Thirty Years that Shook Physics, Doubleday, Garden City, N.Y. (1966), p. 165.
Karl von Meyenn is a historian of physics at the Max Planck-Werner Heisenberg Institute of Physics in Munich. He is the editor of the compendium (six volumes so far) of Pauli's scientific correspondence.1
Engelbert Schucking is a professor of physics at New York University.