The definition of the kilogram is still a chunk of metal. Machined from a chunk of a virtually indestructible platinum-iridium alloy, the international prototype kilogram (IPK) was built to last ...

Out of this meeting, the kilogram—or at least the idea of a standard unit of mass—was born For more than a century, the kilogram has been defined by the weight of a cylinder of platinum-iridium at the ...

Graphene could one day be involved in a new definition of the kilogram. To the left of gold in the periodic table are two elements — platinum and iridium — that are just as interesting in many ...

For the units of length and weight that are widely used in daily life, the standards in Japan were the "prototype meter" and the "prototype kilogram" made of alloy (platinum 90%, iridium 10%) ...