The pyramids' bases match within 0.05 percent thanks to a granite ruler
Around 2900 BC, Egypt carved a royal cubit from black granite: a pharaoh's forearm plus the width of his hand. Builders received copies. The result shows in the pyramids, whose base lengths differ by no more than 0.05 percent. It is the earliest known permanent measurement standard.
Metrology is the science of measurement. The International Bureau of Weights and Measures defines it as covering both experimental and theoretical work, at any level of uncertainty, in every field of science and technology. It rests on three overlapping activities: defining units that everyone accepts, realising those units in practice, and traceability, the chain linking an everyday measurement back to a reference standard. Its branches are scientific metrology, which establishes units; applied or industrial metrology, which puts measurement to work in manufacturing; and legal metrology, which regulates measuring instruments and methods.
Being able to measure is not enough; measurements must agree. Ancient China gave weights and measures a semi-religious role, mentioning the steelyard balance in the Book of Rites, and Greek and Roman architecture each had their own systems. After those empires fell, much of that standardisation was lost, and incompatible local systems made comparison difficult. England's Assize of Measures set length standards in 1196, and Magna Carta in 1215 included a clause on measuring wine and beer.
The modern discipline began with the French Revolution, when a political drive to harmonise units across France produced a length standard drawn from nature. The metre was defined in March 1791, and a decimal metric system followed in 1795. As other countries adopted it over the next 80 years, the Metre Convention set up the bureau, known by its French initials BIPM, to keep national standards aligned. Its remit later widened to electrical and light units and ionising radiation. In 1960 the 11th General Conference on Weights and Measures turned the metric system into the International System of Units.
Each country now maintains a national measurement system, a network of laboratories, calibration services and accreditation bodies. Its reach extends to energy, health, the environment, manufacturing and consumer trust, and fair trade depends on buyers and sellers agreeing on what a kilogram or a litre means.
Source: Metrology
