Science Talk on World Metrology Day

Whoever plans a revolution should be well prepared. And sometimes it is necessary to specify all the details down to the last decimal place. This is exactly what the scientists of measurement, the metrologists, did before they were able to give the International System of Units (Système international d'unités, SI for short) a completely new basis. Gone are the days when a metal cylinder, with all its shortcomings, told the world what a kilogramme should be. This ‘embodiment’ and other idealised rules have now been replaced by natural constants such as the speed of light, Planck's constant and Boltzmann's constant. These constants appear in the fundamental equations of physics and thus determine the ‘rules’ of nature. After metrological institutes around the world have measured the values of the most important natural constants as precisely as possible in extremely complex experiments, their values have now been established once and for all and now form the foundation of all measurement. And for the history books: this (peaceful) revolution took place on 20 May 2019. Its effects could last for all time.