Units of Measure Redefined

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The fundamental units of measure in the International System (SI) will redefined from May 20, 2019, which is also the World Metrology Day.

The 26th meeting of the General Conference on Weights and Measures (CGPM) held in November 2018 at Versailles, France, was historic as the members voted for redefinition of 130 years old “Le grand K – the SI unit of kg” in terms of the fundamental Planck’s constant (h).

Representatives from 60 countries have also agreed for new definitions for Ampere, Kelvin and Mole. The Ampere will be defined by the elementary electrical charge (e); Kelvin by Boltzmann Constant (k); and Mole by Avogadro Constant (NA).

The change aims to tie these units of measure to fundamental constants of the natural world, which improves reliability and ease of comparison.

The CGPM is the highest international body of the world for accurate and precise measurements, and consists of 60 countries including India and 42 Associate Members. The International Bureau of Weights and Measures (BIPM), the main executive body of CGPM, has the responsibility of defining the International System of Units (SI). This revision of the SI is the culmination of many years of intensive scientific cooperation between the National Metrology Institutes and the BIPM. The dissemination of SI units for the welfare of society and industries in the country is the responsibility of Legal Metrology, Department of Consumer Affairs, Government of India.

The International prototype of kilogram (IPK) is kept at the BIPM, Paris, and serves as the international standard of kilogram. It is made of 90% platinum and 10% iridium and is a cylinder of 39 mm diameter and 39 mm height. Replicas of the IPK are made of the same material and are used at BIPM as reference or working standards and national prototype of kilogram (NPK), kept at different National Metrology Institutes (NMIs). The NPK-57, kept at the CSIR- National Physical Laboratory (NPL), Delhi, is sent periodically to BIPM for calibration. The precise and accurate measurements help the country in production of international quality products and help commerce through elimination of the technical barrier to trade.

However, the change will never impact the day-today-day work. For instance, there would be no change in baking ingredients on a kitchen scale, and on tons of goods shipped globally every day.

For astronomers calculating the movements of stars and galaxies or for pharmacologists trying to define doses of medications for a molecule, the new standard of measurement could change the way they work.

The metric system was intended to be rational, universal set of units “for all people, for all time”. The SI unit will finally be truly universal system, free of any human artefacts. (PIB)

Image source: https://www.bipm.org/en/bipm/mass/ipk/


Posted By : ScienceIndia Administrator
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