Quantum leap Redefining SI

摘要

The arcane science of metrology is on the cusp of a quantum leap, a bold redefinition of four of the seven SI base units, in the aftermath of which we will find our lives radically unchanged. The Systeme international d'unites (SI) has its roots in imperial France. In the late 1700s, King Louis XVI ordered investigations into a new, standardised system of weights and measures to crack down on rampant fraud. Louis' expert committee proposed measures based on nature - such as the triple point of water for temperature, and a fixed volume of water for mass. Before the revolution, the 'grave' was proposed as the mass of litre of water, but in 1799 this was updated to the 'gramme' - the mass of 1 cm3 of water at 4°C.