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 ...

The kilogram is getting an update. No, your bathroom scales won’t suddenly become kinder and a kilo of fruit will still weigh a kilo. But the way scientists define the exact mass of a kilogram is ...

The international prototype was forged in the 1880s. Enlarge Image In a heavily-guarded, subterranean vault on the outskirts of Paris is a lump of metal about the size of a plum. To the eye it's an ...

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 ...

The other day, I did something I am dispatched to do every now and then: bought a kilo of basmati rice. It came nicely packaged in a sealed bag. It feels about what I think a kilogram should feel like ...

The kilogram is changing — but (unfortunately) it’s not going to affect how much you weigh. At a meeting of the General Conference on Weights and Measures in Versailles, France, countries (including ...

Assent murmurs its way through the crowd as Nobel laureate Bill Phillips continues. "The time has come to make this transition," he says. "It's a scandal we have this metal, sitting around changing ...