OUR UNITS OF MEASUREMENT

Abstract

Prof. R.K. Pathria is an eminent theoretical physicist, known for his work on superfluidity in liquid helium and phase transitions. The book “Statistical Mechanics” authored by him still continues to be a popular title among undergraduates and is an international bestseller on this subject. Prof. Pathria is currently a professor emeritus at the university of Waterloo. In this article, Prof. R.K. Pathria provides a comprehensive history about the use of different units of measurement. Through this series of four articles, the author attempts to narrate the exciting and thrilling story of the adoption of different units of measurements, dominated by the flavour of an ever-increasing degree of scientific precision which forms the central theme of the series. Each article covers different units—length, time, weight, luminosity, electricity and magnetism. Part I and II cover the most basic measurements a student of physics has to deal with, which are the ones related to the three fundamental entities of Nature—space, time and matter. These measurements constitute the elementary processes of determining the length of a straight line joining two given points of space, the time interval elapsed between two given instants of time, and the mass of a given piece of matter. Part I focuses on length while part II focuses on time and mass. In part III, the author reviews the sequence of developments that finally led to the adoption of the fundamental units employed with respect to heat and light; thermometry and calorimetry are discussed in case of heat and for light the fundamental units employed in photometry. In the concluding article, part IV, the units of measurement employed in the domain of electricity and magnetism are discussed. The author limits the discussion to those aspects which he considers vital to have a holistic perspective.