On the 20th of May, came into effect the revision of the International System of Units (SI), in order to adapt to the world measurements requirements.

Since May 20th, a kilo is not the same kilo we used to know anymore. Coinciding with the World Metrology Day, the revision of the International System of Units, (SI, abbreviated from the French Système International (d’unités)) came into effect. Since then, the kilogram, the ampere, the kelvin and the mol have been redefined in relation to its numerical values, fixed from physical fundamental constants and will inherit the associated uncertainties.

Image from the Spanish Metrological Centre

The SI is a consistent system of units that allows the quantification of any measurable magnitude of interest in a multitude of different fields, such as research, industry, business, society and countless others. It has been defined and formally stablished in 1960, and since then it has been revised partially in some occasions, to meet the needs of Science and Technology. This time, the revision has been deeper than the previous.

The result is a more consistent and fundamental definition of the whole SI, disregarding practical procedures based on material artefacts. It was the case, until now, for the kilo, susceptible of stability losses and strong limitations in the long-term. The SI now favours procedures that are more practical and, furthermore, reproducible in any time or place.

Image from Nature Magazine

The use of physical constants to define the international measurement units will allow the scientific community and the industry to obtain and spread its measurements with more exactitude, from the smallest to the biggest ones, fulfilling modern measurements requirements.

This update may encourage new technologies that were on hold.