It’s mass for the masses. A tabletop device makes the new definition of the kilogram more accessible. Previously, the kilogram had been equal to the mass of a special metal cylinder kept in a vault ...

The watt balance—also known as the Kibble balance—is a precision electromechanical instrument that has revolutionised the realisation of the kilogram by linking it directly to the Planck constant.

THERE’S a new way to weigh. For over a century, the kilogram was defined by a metal cylinder in a French vault. Now, this key unit of mass is defined using the Planck constant, a fundamental figure in ...