Since 1889, Le Grand K, a sleek cylinder of platinum-iridium metal, has ruled from its underground vault in Paris. An absolute monarch, it was the very definition of 1 kilogram of mass. Scientists ...

Since 1889, human civilization has depended upon a magic rock. Known as Le Grand K, it sits under protective glass in St. Cloud, France. Humanity's magic rock is actually a chunk of metallic alloy ...

Is a meter a meter and a second a second? Yes, but they will be defined differently from May 20th on. This marks the beginning of a new era for science. New rules have been in force since May 20th: ...

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 ...

is a senior reporter who has covered AI, robotics, and more for eight years at The Verge. Update, May 20th, 2019, 10AM ET: This article was originally published in November 2018. As of May 20th, 2019, ...