India on Monday adopted a global resolution to redefine four of the seven base units -- kilogramme, kelvin, mole and ampere -- a move expected to have far-reaching effects, including changes in textbooks.

A resolution to redefine four of the seven base units was passed by representatives of 60 countries at the General Conference on Weights and Measures (CGPM) of the International Bureau of Weights and Measures (BIPM), Paris on November 16 last year.

However, it has been implemented across the world on May 20 -- World Metrology Day, Shekhar Mande, Director-General of the Council for Scientific and Industrial Research (CSIR), said.

Over 100 countries have adopted the metric system of measurements, also known as the International System of Units (SI), which has been in practice since 1889. The other base units are -- second, metre and candela.

“The fundamental constants are invariants of time and space and have successfully replaced the artefact-based units, and aptly opened up a new era for the quantum world by linking all seven base units to fundamental constants or quantum standards,” said K. Aswal, Director of the National Physical Laboratory (NPL), one of the oldest scientific institutes in the country that also takes care of setting metrology standards domestically.

The purpose of a system of units is to enable worldwide coherence of measurements. The International System of Units (SI) was formalised in 1960 and has been updated several times to account for development in measurement technology.

“Since the 1960s, we have had to rely ever more heavily on advanced science and engineering in our day-to-day lives, and also in manufacturing, healthcare and science. The proposed changes in the unit definition have been designed to have no immediate consequences,” he said.

“The unit redefinitions represent a profound change of perspective and they are expected to form the foundation of improved measurements for decades to come, as science and technology continues to develop in a way we cannot currently foresee,” Aswal said, however, this “may not change anything drastically”, but it will matter when it comes to measurements less than a kilogramme. For instance, measuring smaller diamonds.

The NPL has also sent recommendations on the proposed changes to be incorporated in the National Council of Educational Research and Training (NCERT), to implement them in contemporary education, he said.

Recommendations on the proposed changes have also been sent to the All India Council for Technical Education (AICTE), Indian Institutes of Technology (IITs), National Institutes of Technology (NITs), and other academic institutes to be incorporated in syllabi of metrology courses in graduate engineering and academic courses.