The International System of Units (SI) is the global standard for measurement, maintained by the International Bureau of Weights and Measures (BIPM) and supported by organizations like the U.S. National Institute of Standards and Technology (NIST). The SI defines units such as the kilogram, ampere, kelvin, and mole, which are currently being redefined based on fundamental physical constants rather than physical artifacts. For example, the kilogram will no longer be based on a metal prototype but instead on the fixed value of the Planck constant. Similar changes are being made for the ampere, kelvin, and mole using the elementary charge, Boltzmann constant, and Avogadro constant, respectively.
These updates aim to improve the accuracy and consistency of measurements worldwide. The Consultative Committee for Units (CCU) has recommended these changes, and they are being implemented gradually. While the redefinitions were officially adopted in 2019, the full transition and widespread use of the new SI units are still ongoing. This shift to a “quantum-based” SI system ensures that measurements remain stable and universally accessible, supporting advancements in science and technology, including fields like quantum computing and precision engineering.
Source: https://www.nist.gov/programs-projects/international-system-units-si
Keywords: Planck constant, SI units, fundamental constants
