Since the 19th century, scientists have based their definition of the fundamental unit of mass on a physical object — a shining platinum iridium cylinder stored in a locked vault in the bowels of the ...

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 ...

Humanity is on the verge of a weighty achievement. On Friday, representatives of more than 60 nations will convene in Versailles, France, to approve a new definition for the kilogram. Since the 19th ...

*Refers to the latest 2 years of stltoday.com stories. Cancel anytime. The U.S. national kilogram, made in 1879 and kept at NIST. Washington Post photo by Salwan Georges Humanity is on the verge of a ...