Facility for Rare Isotope Beams

“The metric system, now officially known as the International System of Units (SI), was born with the French revolution. It has recently undergone its most revolutionary reform since that birth. Famously, the kilogram is no longer defined as the mass of an artifact, the International Prototype Kilogram, but rather is now a quantum concept, defined by fixing the value of Planck’s constant. In fact, all of the base units of the SI are defined by fixing the values of natural constants, and the SI now has a distinctly quantum flavor. The quantization of charge allows us to fix the charge of the electron, defining the ampere as a certain number of electrons per second. The unit of temperature, the kelvin, is no longer based on the triple point of water, but on the thermal energy of the atomic/molecular components of matter, by fixing the value of Boltzmann’s constant. The unit of time has long been quantum, but its impending re-definition will make it even more so.”