ESHS/HSS Annual Meeting

Practices in Parallel: Experiments in Early 20th Century Physics Laboratories

• In Event: Shifting Perspectives: Hands on Instruments Approaches (with Gloves) to Writing a History of Scientific Practices I

English Abstract

The experiments with the oil-drop apparatus are celebrated for their precise determination of the elementary charge and famously associated with the 1923 Nobel Prize in Physics awarded to Robert A. Millikan. Yet, the historical record reveals a much more complex picture. The same apparatus was simultaneously used by Millikan’s doctoral student Harvey Fletcher to investigate another physical phenomenon, Brownian motion, and to determine a different constant, Avogadro’s number. Brownian motion, the thermal and jittery movement of small particles, was treated as a disturbance in one line of inquiry and became the very object of measurement in another.
This complex experimental practice remains largely invisible in the written sources. The experiments were carried out concurrently yet relied on different measurement strategies: tracking moving drops for the determination of the elementary charge versus observing balanced drops for studies of Brownian motion. They required drops of different sizes, produced different types of data, and depended on divergent control and stabilization processes.
As analyzing historical instruments does not automatically lead to an understanding of historical practice, these differences call for even deeper engagement with the material conditions of the experiments. Applying replication methods, i.e. rebuilding the oil-drop apparatus and reenacting both experimental programs, makes these layers of practical differentiation visible. This hands-on engagement generates new questions about the concrete execution of the experiments and reveals challenges that previously went unnoticed. In this way, instruments become material realizations of historically situated experimental practice, whose reconstruction provides deeper insight into 20th century laboratory work.

Author

• Julia Bloemer, Europa-Universität Flensburg