Evolution of Measurement System and SI Units in India

The paper presents a terse review on the evolution of measurement system and International System of Units (SI) in India, the methodology followed to realize the measurement units and the present state of the art in realizing of 7 base units. The measurement systems evolved, developed and used during several ancient historical periods, Indus valley to Vedic period to existing SI system of modern era, are discussed. The major activities carried out during ancient times were primarily based on the units of mass, length and time. The current system has been established and adopted to realize SI units through the fundamental constants, invariant of time and space, which has replaced the dependence on artifacts. The new era of SI system based on quantum metrology has established linkages of all the 7 base units to fundamental constants. The aim of the study is to present the major events, activities and developments carried out in India pertaining to the evolution of SI units. The SI system at the top of traceability chain and heart of metrology and measurement system, it is of utmost important to understand, how the SI system is evolved historically: It becomes further inevitable when India is aiming for AtmaNirbhar Bharat (Self-Reliant India) for augmenting the industrial growth of Indian economy, wherein strengthening the national quality infrastructure for enhancing trade and commerce shall be indispensable and unbroken chain of measurement traceability through new SI system would play a major role. The present review would provide a concise report on these developments, starting from Indus valley period to existing era.