A demonstrator says: "Since 2019 the kilogram has been defined by fixing the value of…
PHYSICS · Subjective · Fermi University Physics · Scientific Practice & Experimental Methods · Quantities, units and the practice of measurement · Quantities, units and the practice of measurement
Measurement and Method, Ch What a measured value is: quantities, units and the SI
Problem
A demonstrator says: "Since 2019 the kilogram has been defined by fixing the value of the Planck constant h exactly, so every mass anyone measures, including the electron's, is now known with zero uncertainty." Is this correct? State which constants have been given exact values by the SI since 2019, and explain why the electron's mass is not one of them, quoting the relative uncertainty of its CODATA recommended value.