Measurements

Standardisation of measurement units

Measurements most commonly use the International System of Units (SI) as a comparison framework. The system defines seven fundamental units: kilogram, metre, candela, second, ampere, kelvin, and mole. All of these units are defined without reference to a particular physical object which would serve as a standard. Artefact-free definitions fix measurements at an exact value related to a physical constant or other invariable natural phenomenon, in contrast to reliance on standard artefacts which are subject to deterioration or destruction. Instead, the measurement unit can only ever change through increased accuracy in determining the value of the constant it is tied to.