The International System of Units (SI) is undergoing significant changes to its definitions, with the 26th meeting of the Conférence Générale des Poids et Mesures (CGPM) adopting a new approach to articulating the definitions of the seven base units. This approach fixes the numerical values of seven “defining” constants, including fundamental constants of nature such as the Planck constant and the speed of light. These changes, effective from May 20th, 2019, mark a historic step forward in the realization of all units with an accuracy limited only by the quantum structure of nature and technical abilities, rather than by the definitions themselves. The changes were agreed by the CGPM in November 2018 and will have far-reaching impacts on science, technology, industry, and trade.
Source: https://www.nist.gov/pml/special-publication-330/sp-330-preface-9th-edition
Keywords: Fundamental constants of nature, Quantum phenomena, Atomic physics, Measurement technology, Metrology
