Kilogram

The kilogram is the base unit of mass in the International System of Units. Until 2019 it was defined by a single physical platinum-iridium cylinder kept in France, the last SI base unit still tied to a manufactured object; it is now defined by fixing the value of the Planck constant, connecting mass to precise measurements of electrical power through a device called a Kibble balance, so the definition no longer depends on any one artifact that could be damaged, contaminated, or lost. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/