Which SI base unit was redefined in 2019 by fixing the numerical value of the Planck constant?
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Kilogram
The kilogram was the last SI unit defined by a physical artifact (the International Prototype of the Kilogram). It is now defined using the Kibble balance and the Planck constant, making the unit stable over time.
Also asked as:
- Which SI unit's definition was changed in 2019 to be based on the Planck constant rather than a physical object?