Mass is the amount of substance in an object. It is different from the weight of an object as weight is the force acting on the object due to the gravitational acceleration. Force is a derived unit; a product of mass and the acceleration experienced by the object.
Measurement of mass and force is critical in many industry sectors such as aerospace, construction, automobile, electronics, manufacturing, pharmaceutical and healthcare. The accurate measurement of mass and force has great impact on quality of products and services; performance and reliability of equipment; health and safety of the people.
From 20 May 2019, the SI unit of mass, kilogram (kg) has officially been re-defined! The kilogram is no longer defined by an artefact that is equal to the mass of the international prototype of the kilogram (an alloy of platinum and iridium) kept at the BIPM in France. Of all the seven SI units, the kilogram is the only unit that is still defined using an artefact standard. The artefact standard is susceptible to contamination, wear and tear, risk of damage by fire, water, mishandling… etc. The real change in the mass value of the international prototype of the kilogram is undetermined as there is no method precise enough to measure it.
With this new definition, it means that the unit of mass is now defined in terms of constants based on natural phenomenon. This decision provides the foundation for the future stability of the SI and it opens opportunity for the use of new technologies, e.g. quantum technologies, to implement these new definitions.
The International Prototype of the kilogram