This revolution has been a long time in the making. Behind it are metrologists working in their scientific laboratories, and scientific managers in their decision-making committees. Now the moment is approaching when many of the old quantities (specifically, the definitions behind them) will have to step down to make way for their successors, who are waiting in the wings. The quantities concerned are the kilogram, the mole, the ampere and the kelvin. The foremost expert committee in the world of metrology, the International Committee for Weights and Measures (Comité international des poids et mesures, CIPM), issued its unequivocal recommendation for this development at its recently concluded annual assembly. It is hoped that, at their general conference next year, the international community of signatories to the Metre Convention will heed the experts’ advice and provide the physical units with an especially firm foundation – one that...
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