Modern civilisation, it is said, would be impossible without measurement. And measurement would be pointless if we weren’t all using the same units. So, for nearly 150 years, the world’s metrologists have agreed on strict definitions for units of measurement through the International Bureau of Weights and Measures, known by its French acronym, BIPM, and based outside Paris.
Nowadays, the bureau regulates the seven base units that govern time, length, mass, electrical current, temperature, the intensity of light and the amount of a substance. Together, these units are the language of science, commerce and technology. Scientists are constantly refining these standards. In 2018, they approved new definitions for the kilogram (mass), ampere (current), kelvin (temperature) and mole (amount of substance). Now, with the exception of the mole, all of the…