In November 2018, the General Conference on Weights and Measures officially voted to redefine the kilogram, replacing the physical metal cylinder known as “Big K” with a new standard based on the Planck constant. This quantum-mechanical value, supported by organizations like NIST, serves as the foundation for the new measurement system. By fixing this number, the standard ensures that mass can be measured with high accuracy anywhere in the world, rather than relying on a single physical object stored in a vault.
The redefinition took effect in May 2019 after rigorous testing confirmed that independent experiments could reproduce the results within strict accuracy limits. It utilizes specialized devices to compare mechanical and electrical power, or counts atoms in a sphere of pure silicon to match the fixed quantum value. This change not only updated the kilogram but also redefined the kelvin, ampere, and mole, creating a unified system that connects measurements from the microscopic to the macroscopic.
This shift marks a significant milestone for science and industry, moving away from physical artifacts to definitions based on the fundamental laws of nature. Educational and industrial sectors will need to update their practices to align with these new constants, ensuring that future measurements are more stable and scalable. The implementation represents a permanent transition to a measurement framework rooted in quantum physics.
Keywords: Planck constant, Kibble balance, mass redefinition
