The new kilogram has finally arrived.
Updates to scientists’ system of measurement went into force May 20, redefining the kilogram and several other units in the metric system. The revamp does away with some outdated standards — most notably, a metal cylinder kept in a vault near Paris that has defined the kilogram for 130 years (SN: 12/8/18, p. 7).
Tinkering with units allows scientists to more precisely measure weights, temperatures, electric currents and other quantities laid out in the International System of Units used around the globe. The kilogram, the basic unit of mass, is now defined by a quantum quantity known as the Planck constant. That value, an immutable constant of nature, is the same everywhere in space and time. That’s an improvement over the Parisian artifact, which could have changed slightly if gunk or scratches marred its surface.