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 ...

Deep underneath the Parisian suburb of Saint-Cloud, in a vault that can only be opened by three people wielding three different keys, there lies a hunk of metal that is so crucial to the world of ...

The supreme arbiter of mass for humankind is a polished cylinder of platinum alloy just smaller than a golf ball. It was cast in London in 1879, unveiled a decade later in a ceremony in France, and ...

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 ...

More than a century ago, a small metal cylinder was forged in London and sent to a leafy suburb of Paris. The cylinder was about the size of a salt shaker and made of an alloy of platinum and iridium, ...

When news breaks, you need to understand what actually matters — and what to do about it. At Vox, our mission to help you make sense of the world has never been more vital. But we can’t do it on our ...

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 ...

Stop the presses! Physicists at the National Institute of Standards and Technology have made a new measurement of Planck’s constant to a highly accurate degree. It’s the latest step toward improving ...

It has been used as a standard unit of weight measurement since the time of the French revolution, based on the precise mass of a lump of metal held in Paris. But the kilogram may be about to be given ...

Kevin Pimbblet receives funding from STFC and the Royal Astronomical Society. How much is a kilogram? 1,000 grams. 2.20462 pounds. Or 0.0685 slugs based on the old Imperial gravitational system. But ...