Experiments studying the fine-structure of hydrogen spectra played an important role in physics development in the 1920s-1930s. As core instruments, the evolution of high-resolution-power spectroscopes in use largely reflects how these experiments developed. Focusing on these experiments, we describe how spectroscopes evolved from old instruments—Lummer-Gehrcke plates and echelons—to new ones, the Fabry-Perot interferometers. In the 1920s, experimenters noticed that new instruments could simplify error handling and thus were introduced into these experiments, although their initial measurement accuracy was not as good as that of the old instruments. In the 1930s, a new method specifically designed for the new instruments significantly improved the measurement accuracy, winning the competition against the old ones. Meanwhile, some of the research concerns underlying such experiments changed. With these new concerns, the old instruments were replaced without further competition, even though the old ones were potentially as capable as the new ones in meeting these concerns. Previous narratives of this history have mainly focused on the controversies between the results or conclusions of concurrent experiments. As a complementary perspective, we take the evolution of the spectroscope as a clue to reveal the consistency and continuity of these experiments and analyze the driving factors behind the spectroscope's evolution by examining the accumulation of knowledge of experimental errors.
ZHANG et al. (2025) studied this question.