After a vote (and a century of research), the standard measure for mass is redefined, and the long reign of Le Grand K is ended. A one-kilogram sphere of single-crystal silicon, one of the roundest ...

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In a subterranean vault in a suburb of Paris lies a small, rarely seen metal cylinder known as Le Grand K. For 130 years, this golf-ball-sized hunk of 90% platinum and 10% iridium has served as the ...

The NIST-4 Kibble balance, an electromagnetic weighing machine that is used to measure Planck's constant, and in turn, redefine the kilogram. Jennifer Lauren Lee / NIST Locked in a vault that requires ...

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The official US kilogram — the physical prototype against which all weights in the United States are calibrated — cannot be touched by human hands except in rare circumstances. Sealed beneath a bell ...

Physics is a funny thing. Despite dictating the behaviors and states of everything from atoms to stars, our interpretation of its effects are rooted in very human constructs. Meters, amperes and ...

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Update, May 20th, 2019, 10AM ET: This article was originally published in November 2018. As of May 20th, 2019, World Metrology Day, the new definition of the kilogram based on Planck’s constant has ...