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 ...

Planck’s constant is equal to 6.626069934 x 10−34 kg∙m2/s, they said. And their uncertainty was just 13 parts per billion. That number may be barely intelligible to the casual observer. But to Pratt, ...

How much is a kilogram? 1,000 grams. 2.20462 pounds. Or 0.0685 slugs based on the old Imperial gravitational system. But where does this amount actually come from and how can everyone be sure they are ...

A kilo is a kilo is a kilo, right? Wrong. Monday marks World Metrology Day, and this year’s edition sees a big change in the way the kilogram unit is defined. In November last year, scientists and ...

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 ...

Scientists and policy makers from around 60 nations voted unanimously Friday to redefine the kilogram. The decision at the General Conference on Weights and Measures in Versailles, France was greeted ...

If you’ve weighed yourself recently, it may be some comfort to know that what you think you weigh is wrong. That’s because the International Bureau of Weights and Measures has voted to change the way ...

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 ...

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 ...