https://www.nytimes.com/2018/11/16/science/kilogram-physics-measurement.htmlFriday, in a small conference center located just steps from the Palace of Versailles, several dozen nations voted to overthrow Le Grand K (the physical specimen that had served as the official definition of the kilogram) and to redefine the kilogram and three other standard units of measure: the ampere, for electrical current; the kelvin, for temperature; and the mole, which describes the amount of a chemical substance. The vote fulfills an 18th-century dream. Henceforth, all seven units in the International System of Units, otherwise known as the S.I., will no longer be defined by material objects and instead will be defined only by abstract constants of nature.
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