Science geeks everywhere are celebrating World Metrology Day today. Today has also been chosen by Bureau International des Poids et Mesures (International Bureau of Weights and Measures) to implement changes to the International System of Units or the SI. The changes are to the definitions of the kilogram, ampere, kelvin, and mole.
Of special interest to lighting designers, the Kelvin is now defined "by taking the fixed numerical value of the Boltzmann constant k to be 1.380 649 x 10–23 when expressed in the unit J K–1, which is equal to kg m2 s–2 K–1, where the kilogram, metre and second are defined in terms of h, c and Cs."
Yeah, I don't know what that means, either! Here's a link to the full definition and formula.