After it’s all over, your lights will be just as bright, and your refrigerator just as cold. But very soon the ampere—the base unit in the International System of Units (SI) for electrical current—will take on an entirely new identity. In 2018, the SI base units are scheduled to be re-defined in terms of physical constants, with major changes in the kilogram, ampere, kelvin, and mole. NIST scientists are at work on an innovative, quantum-based measurement system that will be consistent with the impending change.

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