Understanding the Revised SI: Background, Consequences, and Perspectives

Abstract

Abstract This article expounds the significance of the revision of the international system of units, the SI, approved by the General Conference on Weights and Measures (CGPM) in 2018. The revised SI implements a construct of a system of units based on fixing the numerical values of constants of nature, the “defining constants.” This fundamental development in the SI is not only elegant and infinitely sustainable, but moreover will drive future technological innovation. This article provides an historical overview and discusses the underlying principles and consequences of the revised SI: from the history of Planck's proposal for creating a system of units “valid for all times and civilizations,” to the scientific and technological motivations for the revision and the expected resulting innovations.