Quantum theory and the electromagnetic world-view

Isis, 2011

Even though Arnold Sommerfeld and his school are commonly regarded as major contributors to the formation of quantum theory, little has been written on the origins, development and impact of Sommerfeld's brand of theory-making. Suman Seth's Crafting the Quantum aims at filling this gap with much attention to the cultural conditions and the diversity of practices in the then-emerging theoretical physics. Seth defines Sommerfeld's approach as a 'physics of problems' in which well-defined rules and sound mathematics are applied to a great variety of specific problems, with much attention to phenomenological and computational details. Seth nuances this picture by bringing in Sommerfeld's early attachment to the electromagnetic world view, his ideal of a complete unified theory of microphysical phenomena, and the aesthetic dimension of his quantum numerology. Seth regards Sommerfeld's mature style as the resultant of his threefold background in mathematics, technical mechanics and physics. Sommerfeld originally saw himself as a mathematician bringing his skills to the service of applied mechanics and physics, in the spirit of his mentor Felix Klein's cross-disciplinary projects. After a few years of teaching technical mechanics at the Technische Hochschule in Aachen, he obtained the chair of theoretical physics in Munich, from which he trained a large number of theoretical physicists of the following generations. Seth explains this enormous success by diverse characteristics of Sommerfeld's teaching: his lively mode of exposition, his frequent appeal to figures and mechanisms, the place he gave to elementary considerations, his dwelling on unsolved problems, sessions of supervised problem solving in parallel with the course, and a personal acquaintanceship with the students. Sommerfeld also benefitted from the contemporary surge of theoretical physics owing to the financial difficulties of experimental physics in the impoverished Weimar Republic. As proofs of this evolution, Seth cites Lenard's and Stark's famous attacks, and what he wittily dubs the 'discovery of the Pauli effect', namely the multiplication of stories of the perturbation of experiments by the mere proximity of the proudly pure theorist Wolfgang Pauli. Seth judiciously contrasts Sommerfeld's physics of problems with the 'physics of principles' of two contemporary theorists, Max Planck and Niels Bohr. By physics of principles, Seth sometimes means any theoretical physics that has the philosophical ambition of providing firm and general foundations. He occasionally means something more similar to Poincaré's physique des principes: a theory defined by means of general principles of empirical origin, and not by the constructive combination of hypothetical elements. The latter definition applies to Max Planck, who sought a via media between Mach's positivism and the rising theoretical microphysics of Ludwig Boltzmann, Hendrik Lorentz and others. As Seth explains, Planck applied the principles of thermodynamics to ideal processes performed on coarsely defined systems. He did not require the experimental realizability of these processes or the experimental accessibility of the finer details of the systems. Seth finds this view embodied in Planck's early works on the thermodynamics of solutions and continued in his later works. In early quantum theory, Planck sought to determine the quantum structure of phase space through thermostatistical considerations that blurred the kinematics of individual atoms and molecules. In contrast, Sommerfeld quantized the motion of individual electrons and intertwined his analysis with aspects of the rising experimental microphysics.

The British Journal for the History of Science, 2011

The Foundations of Quantum Mechanics - Historical Analysis and Open Questions - Cesena 2004, 2006

The rise of quantum physics is analyzed by outlining the historical context in which different conceptions of Nature (mechanistic, thermodynamic and electromagnetic ones) were in competition to give a foundation to physics. In particular, electromagnetic conception roots of quantum physics are showed: since Larmor's first trials till to Poincaré's quantum electromagnetic mechanics and to Heisenberg's new mechanics.

Science, 1951

Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics, 2009

The paper detailed what we now know as his ''exclusion principle.'' This essay situates the work leading up to Pauli's principle within the traditions of the ''Sommerfeld School,'' led by Munich University's renowned theorist and teacher, Arnold Sommerfeld (1868-1951). Offering a substantial corrective to previous accounts of the birth of quantum mechanics, which have tended to sideline Sommerfeld's work, it is suggested here that both the method and the content of Pauli's paper drew substantially on the work of the Sommerfeld School in the early 1920s. Part One describes Sommerfeld's turn away from a faith in the power of model-based (modellmässig) methods in his early career towards the use of a more phenomenological emphasis on empirical regularities (Gesetzmässigkeiten) during precisely the period that both Pauli and Werner Heisenberg (1901-1976), among others, were his students. Part two delineates the importance of Sommerfeld's phenomenology to Pauli's methods in the exclusion principle paper, a paper that also eschewed modellmässig approaches in favour of a stress on Gesetzmässigkeiten. In terms of content, a focus on Sommerfeld's work reveals the roots of Pauli's understanding of the fundamental Zweideutigkeit (ambiguity) involving the quantum number of electrons within the atom. The conclusion points to the significance of these results to an improved historical understanding of the origin of aspects of Heisenberg's 1925 paper on the ''Quantum-theoretical Reformulation (Umdeutung) of Kinematical and Mechanical Relations.''

discrete, indivisible packets or "quanta" of energy. Prior to 1900 physicists pictured the atom as a nucleus that looked something like a plum to which were attached tiny protruding springs. (This was the atomic model hypothesised by J J Thomson and named the plum pudding model ). At the end of each spring was an electron. Giving the atom a jolt, by heating it, for instance, caused its electrons to jiggle (oscillate) on the ends of their springs.

2005

What were the real nature and role of the annus mirabilis, 1905, in Physics? In this paper we discuss in a historical perspective Planck’s and Einstein’s contributions as the fundamental steps in the scientific transformations (the latter with a sharper sense of methodological awareness) that led from the mechanistic and reductionist approach of 19 th century physics to the fulfillment of the formal revolution of quantum mechanics. This process underwent with further scientific breaks, in the context of the social and economic situation and the corresponding role of science.The mechanistic approach adopted in physics at the end of the 19 th century not only produced difficulties and contradictions, but resulted in the limitation of further scientific development. Chemists were the first, at that time, to perceive such limits, and introduce a thermodynamic approach, whose role in the revolution in physics must be underlined. Planck was the first physicist to introduce a procedure tha...

The philosopher-Physicists centers on the origins of modern mathematical physics developed primarily by Maxwell and Helmholtz. In alternate chapters, the contributions of the principals are placed in the context of the prevailing discourses and controversies in physics and philosophy. Cultural contexts, such as art (e.g. the pre-Raphaelites), literature (e.g. romanticism) and historical events (e.g. the revolutions of 1848 and the Franco-Prussian war) are presented. Contemporaries, such as Boltzmann, Gibbs, Oersted, and Riemann in mathematical physics, and Fichte, Schelling, Hegel, and Frege in philosophy are considered. The last chapters deal with the influence of the work of Maxwell and Helmholtz on the developments in 20 th century mathematical physics, focusing on the origins of quantum mechanics. The theme of the arguments is in the influence of Kantian epistemology and metaphysics on the authors. The epilogue examines the work of Arthur Compton as founded on Maxwell's electrodynamics and field theory and Helmholtz' concept of energy (all modified by Einstein), and Boltzmann's Statistical Mechanics. It highlights the difficulties of modern wave-particle dualism inherent on their dependence on the mathematical formalism and on innovations of the principals. The arguments are paraphrased with a minimum of both scientific and philosophical technical terminology, and there is no mathematical notation. This is to make the work accessible to non-specialists, typically at the undergraduate level.