Open AccessNew SI and precision measurements: an interview with Tianchu Li
Author(s) -
Jin Wang
Publication year - 2020
Publication title -
national science review/national science review
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.433
H-Index - 54
eISSN - 2095-5138
pISSN - 2053-714X
DOI - 10.1093/nsr/nwz211
Subject(s) - avogadro constant , planck constant , kilogram , international system of units , ampere , boltzmann constant , metrology , constant (computer programming) , physics , engineering physics , analytical chemistry (journal) , thermodynamics , optics , quantum mechanics , chemistry , computer science , voltage , medicine , chromatography , body weight , quantum , programming language
On 13-16 November 2018, the 26th General Conference of Weights and Measures (CGPM) was held in Paris. The conference adopted Resolution A on 'Revision of the International System of Units (SI).' According to Resolution A: four of the SI basic units, namely kilograms, amps, kelvin and mole, are defined by the Planck constant h, the basic charge constant e, the Boltzmann constant k and the Avogadro constant N A , respectively. This establishes the basic quantities and units in SI on a series of constants. The new SI was officially launched on 20 May 2019. This is the most significant change and a milestone in the history of metrology since the Metre Convention was signed in 20 May 1875. Professor Tianchu Li, an academician of the Chinese Academy of Engineering, has been working on time and frequency standards for 37 years. In this interview, Prof. Li reviews the quantization and constant evolutions of the second and meter, and introduces the redefinitions of ampere, kelvin, kilogram and mole, and their significance for precision measurements.