Affirmation of the Open Source Definition | Open Source Initiative
▻https://opensource.org/node/966

PALO ALTO, Calif. - Feb. 5, 2019 — In 1799 the kilogram was defined as the mass of a litre of water. In 1889, metal cylinders of the precise identical mass were created as reference objects.

In the hundreds of years since, the physical nature of the metal caused those cylinders no longer to reflect the identical mass as defined. In order to ensure the integrity of a vital unit of measurement, the kilogram was redefined as the same mass but simply expressed in terms of fundamental and invariable physical constants.