Kilogram

The kilogram is the SI base unit of mass. Since 2019, its definition fixes the numerical value of the Planck constant.

Planck constant: A physical constant relating a quantum’s energy to its frequency. Its fixed numerical value anchors the kilogram’s present definition.
Grave (unit): A proposed French metric unit of mass, defined as the mass of one litre of water. Its water-based standard was an early predecessor in the kilogram’s development.
Mass: A physical quantity measuring inertia and, in gravitational theories, the source of gravitational effects. The kilogram is the SI unit used to quantify mass.
Bureau International des Poids et Mesures: The international organization that coordinates measurement standards and maintains key reference facilities. It coordinated the transition from the international prototype to the revised kilogram definition.
Kibble balance: An instrument that compares mechanical power with electrical power to measure mass. It realizes the kilogram by linking a test mass to electrical measurements.
Gram: A metric unit of mass equal to one-thousandth of a kilogram. The kilogram was established as one thousand grams in the metric system.
International System of Units: The globally used system of measurement built around seven base units and defined constants. The kilogram’s meaning and role are set within this system.
National metrology institute: A country’s designated organization for maintaining and disseminating measurement standards. Institutes now realize the kilogram using experiments grounded in fixed constants.
Josephson effect: The quantized voltage produced by a superconducting junction driven by microwave radiation. It supplies a precisely measurable voltage in Kibble balance experiments.
Kilogramme des Archives: A platinum standard kilogram made in 1799 and kept in the French national archives. It embodied an early material standard for the unit.

Linked from 29 pages