World gets new definition for units of kilogram, Kelvin, mole and ampere

The new SI is being implemented worldwide from May 20. This decision will enable scientists and researchers to base the SI units entirely on fundamental properties of nature

New Delhi: After decades of ground-breaking laboratory works, the world's scientific and technical community, in a landmark and historic decision taken in the recent open session of the General Conference on Weights and Measures (CGPM) at BIPM on November 16 2018, has unanimously adopted the resolution to redefine four of the seven base units, the kilogram (SI unit of weight), Kelvin (SI unit of temperature), mole (SI unit of amount of substance), and ampere (SI unit of current).

This decision has now enabled scientists and researchers to base the SI units entirely on fundamental properties of nature, which will ensure their ongoing refinement and improvement for years to come. The fundamental constants are invariants of time and space and successfully replaced the artefact based units, and aptly opened up the new era for the quantum world by linking all seven base units to fundamental constants/quantum standards.

New SI to take effect from today

The new SI is being implemented worldwide from May 20, i.e. the World Metrology Day. The World Metrology Day (WMD) is celebrated annually on this very day as the Metre Convention was signed by representatives of 17 nations on May 20, 1875. The Convention set the framework for global collaboration in the science of measurement and in its industrial, commercial and societal applications.

On this historic day, CSIR-NPL introduced redefined SI Units to nation in terms of constant of nature through a series of events, delivering lectures, releasing theme (The International System of Units – Fundamentally Better) based poster of BIPM; release of NPL's designed posters introducing redefined SI to nation highlighting fundamental constant of nature and impact of metrology on all walks of human life.