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How Accurate Is the Standard Second?

Published online by Cambridge University Press:  01 January 2022

Abstract

Contrary to the claim that measurement standards are absolutely accurate by definition, I argue that unit definitions do not completely fix the referents of unit terms. Instead, idealized models play a crucial semantic role in coordinating the theoretical definition of a unit with its multiple concrete realizations. The accuracy of realizations is evaluated by comparing them to each other in light of their respective models. The epistemic credentials of this method are examined and illustrated through an analysis of the contemporary standardization of time. I distinguish among five senses of “measurement accuracy” and clarify how idealizations enable the assessment of accuracy in each sense.

Type
Research Article
Copyright
Copyright © The Philosophy of Science Association

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Footnotes

I am indebted to Judah Levine, David Wineland, Till Rosenband, and their colleagues at the Time and Frequency Division at the U.S. National Institute of Standards and Technology (NIST) for valuable discussions. My visit to NIST in summer 2009 was made possible with kind help from Ian Hacking and Allan Franklin as well as a travel grant from the University of Toronto. I am also grateful to Margaret Morrison, Ian Hacking, Anjan Chakravartty, Marcel Boumans, Stephan Hartmann, Carlo Martini, Isaac Record, Paul Teller, Jonathan Weisberg, and several members of the audience at the Philosophy of Science Association meeting for helpful feedback on earlier versions of this article.

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