An introduction to the revised international system of units (SI)

In November 2018, the General Conference on Weights and Measures (CGPM) gave its unanimous approval to Resolution 1, a major revision of the SI to take effect on May 20, 2019 [1]. The intentions of the CGPM had already been set out in a resolution adopted in 2011. All of the work needed to meet the requirements of the 2011 resolution was monitored by the International Committee for Weights and Measures (CIPM), which drafted both resolutions. The CIPM relied heavily on its technical Consultative Committees, composed primarily of experts from National Metrology Institutes and international science bodies with a focus on metrology.