Multiple Perspectives on the Stern-Gerlach Experiment

  • Tilman SauerEmail author
Part of the Boston Studies in the Philosophy and History of Science book series (BSPS, volume 319)


Different or conflicting accounts of the same episode in the history of science may arise from viewing that episode from different perspectives. The metaphor suggests that conflicting accounts can be seen as complementary, constructing a multi-dimensional understanding, if the different perspectives can be coordinated. As an example, I discuss different perspectives on the Stern-Gerlach experiment. In a static interpretation, the SGE has been viewed as an experiment that allows the determination of the magnetic moment of silver atoms. Based on the concept of magnetic momentum arising from orbital angular momentum, the original experiment was designed in 1922 as an experimentum crucis to decide between Bohr’s quantum theory and classical electromagnetic theory, and its outcome was interpreted as a confirmation of the Bohr-Sommerfeld quantum postulates. After the advent of quantum mechanics, the SGE was reinterpreted in terms of magnetic moment arising from the electron’s spin angular momentum. In a dynamical interpretation, physicists have asked for the physical mechanism responsible for the quantization of the angular momentum with respect to the direction of the magnetic field. Although different suggestions were explored, none was ever accepted as fully satisfactory. Today this difficulty is seen as a paradigmatic instance of the unsolved quantum measurement problem.


Angular Momentum Wave Packet Silver Atom Magnetic Field Vector Inhomogeneous Magnetic Field 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



My understanding of the SGE effect has profited a lot from discussions with Horst Schmidt-Böcking and Wolfgang Trageser. I also thank Tim Räz, Raphael Scholl, and Adrian Wüthrich for helpful criticism of an earlier version of this paper.


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© Springer International Publishing Switzerland 2016

Authors and Affiliations

  1. 1.Institute of MathematicsJohannes Gutenberg University MainzMainzGermany

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