Revised the international system of units (SI)
On November 16, the General Conference on Weights and Measures adopted a resolution in which new definitions were approved for four of the base units of the SI: kilogram, ampere, kelvin and mol, which are redefined in terms of universal constants.
The new definitions are based on fixed numerical values of the Planck constant (h), the elementary charge (e), the Boltzmann constant (kB) and the Avogadro constant (NA), respectively. In addition, the definitions of the seven basic SI units are also expressed uniformly based on a constant.
The definition of the candle, whose pattern in Spain is made by the IO-CSIC, has been reformulated based on the luminous efficiency constant Kcd ,, a technical constant for photometry, and, therefore, it will continue to be linked to the watt. More details of this historic change can be found at
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