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Quantity Calculus, Fundamental Constants, and SI Units.

Barry N Taylor1

  • 1National Institute of Standards and Technology, Gaithersburg, MD 20899-8420, USA.

Journal of Research of the National Institute of Standards and Technology
|December 8, 2021
PubMed
Summary
This summary is machine-generated.

The International System of Units (SI) is undergoing revision, with a new system effective May 20, 2019. This paper updates previous work, highlighting the utility of quantity calculus for understanding SI unit revisions and defining constants.

Keywords:
International System of UnitsSISI defining constantsfundamental constantsquantity calculus

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Area of Science:

  • Metrology
  • Physics
  • Chemistry

Background:

  • The International System of Units (SI) is set for a significant revision.
  • The 26th General Conference on Weights and Measures is scheduled for November 2018.
  • The revised SI will be implemented on World Metrology Day, May 20, 2019.

Purpose of the Study:

  • To update a 2011 analysis of the SI in light of the impending revisions.
  • To demonstrate the continued relevance and utility of quantity calculus.
  • To provide expressions for SI base units and defining constants under both current and revised systems.

Main Methods:

  • Review of the quantity calculus.
  • Analysis of the seven defining constants in the current and revised SI.
  • Derivation of expressions for SI base units and relationships between unit magnitudes.

Main Results:

  • Expressions for the seven current and revised SI base units are provided.
  • Relationships between the magnitudes of revised and current SI units are established.
  • Numerical values of current SI defining constants in revised SI units are derived using quantity calculus.

Conclusions:

  • The quantity calculus is a valuable tool for navigating SI unit revisions.
  • The paper provides a comprehensive update on the SI, incorporating the latest changes.
  • Understanding the relationships between old and new SI units is crucial for scientific consistency.