ESHS/HSS Annual Meeting

Carrying the Second: Flying Clocks, Scientific Diplomacy, and the Redefinition of Time

• In Event: The Politics of Standardization

English Abstract

In the mid-twentieth century, the emergence of atomic time did not replace astronomical time overnight. It required empirical proof, inter-institutional trust, and a technological infrastructure capable of validating and comparing standards. In this context, “flying atomic clocks” — portable caesium clocks transported by aircraft — became the most reliable method for physically confronting local realizations of time.

Rather than functioning as mere courier devices, these itinerant clocks embodied the metrological and geopolitical negotiations underpinning the redefinition of the second in 1967. Hewlett-Packard engineers, national standards laboratories (notably NBS/NIST), and European astronomical observatories used flight campaigns to directly compare frequency standards, assess discrepancies, and calibrate institutional claims to authority. They tested not only precision, but also the legitimacy of actors competing to anchor the atomic second.

Grounded in archival material from the Neuchâtel Observatory, HP documentation, and correspondence between North American and European laboratories, this paper examines how flying clocks became leverage in the politics of standardization. They enabled industrial actors to demonstrate technological superiority, while simultaneously offering states a tool of scientific diplomacy: a neutral, measurable procedure to negotiate convergence without subordinating one national laboratory to another.

By following these mobile instruments, I argue that the adoption of the atomic second was less the triumph of a measurement concept than the outcome of a techno-industrial alignment. Flying clocks transformed atomic time from a laboratory ideal into a globally recognized regime, reshaping the hierarchy of metrological institutions and redefining the relationship between science, industry, and international authority.

Author

• Julien Gressot, Université de Neuchâtel