Refining Our Accounts of Entities We Can’t See

Theodore Arabatzis. Representing Electrons: A Biographical Approach to Theoretical Entities. Chicago: University of Chicago Press, 2006. xiv + 295 pp. Cloth, $70; paper, $28.

Reviewed by Janet D. Stemwedel

Those immersed in science sometimes forget the peculiar challenges presented
by entities like electrons that are undetectable to the unaided senses. How can we build accurate descriptions of these entities or even be sure they exist? Given that electrons are unobservable, what are the constraints on our notions of them?

In Representing Electrons, Theodore Arabatzis approaches these questions by examining how accounts of electrons developed between 1896 and 1925. He notes how difficult it is to identify a moment of discovery and instead tracks “a gradual process of accumulation of evidence to the effect that a novel subatomic entity, the electron, exists” (p. 66). Acceptance of this evidence was influenced by experimental developments and theoretical and philosophical commitments (e.g., desire to avoid alchemical implications: if electrons were material constituents of atoms, then the transmutation of matter might be possible), all of which are discussed in detail. In tracing the development of theoretical descriptions of the electron, Arabatzis reveals a striking interplay between scientists’ theories and the experimental results scientists took to reveal essential features of the entity (e.g., charge-to-mass ratio, lines in atomic spectra). Repeated attempts to model the behavior of electrons using classical assumptions were frustrated by mismatches with experimental results and internal inconsistencies. Scientists strove to account for new experimental features (e.g., the fine structure of the hydrogen spectrum) by making successive modifications to existing theoretical accounts.

Students of chemistry often forget that many of the pioneers of modern atomic theory (e.g., Ernest Rutherford, J.J. Thomson, and Niels Bohr) were physicists. Arabatzis provides an illuminating look at how physicists and chemists seeking to explain different phenomena produced differing (even contradictory) notions of electrons. For chemists an adequate explanation of the electron had to explain chemical combination; physicists wanted to know what role those same electrons played in cathode rays and atomic spectra. The concerns of both fields became constraints on the notion of the electron. Arabatzis pays particular attention to Irving Langmuir and G. N. Lewis’s efforts to reconcile these notions.

Representing Electrons’ careful multidisciplinary approach is a mixed blessing.While philosophers, historians, physicists, and chemists will all find issues of interest, they are likely to encounter significant stretches that speak to someone else’s concerns (e.g., the methodological preliminaries situating the book within ongoing historiographical and philosophical debates or the detailed formula derivations included in the discussions of successive modifications of accounts of the electron). Nevertheless, Arabatzis takes pains to connect the details to the central question—how we came to our understanding of electrons—and the details of that journey help convey the magnitude of the achievement.