New System of Measurement Units Proposed

The National Institute of Standards and Technology (NIST) is backing a worldwide effort to make major revisions to the International System of Units (SI), the modern metric system that is the basis of global measurement.

The most significant change in the proposed revisions to the SI would be the kilogram, the only one of the seven base units of the SI that is still defined in terms of a material “artifact”: A 130-year-old platinum-iridium cylinder at the International Bureau of Weights and Measures in France.

The goal to remove the last artifact is driven by the very small mass changes that it experiences over time. The proposed system defines a kilogram in terms of the Planck constant, used in quantum physics.

The new system would apply fixed values to constants which would then define all base units, i.e. the ampere could be defined in terms of the electric charge of a proton.

The International Committee for Weights and Measures will be submitting the resolution at the General Conference on Weights and Measures, an international body that has the authority to adopt the resolution. If the resolution passes, a new system of measurement could be in practice within the next ten years.