PARIS — A kilogram just isn't what it used to be. The 118-year-old cylinder that is the international prototype for the metric mass, kept tightly under lock and key outside Paris, is mysteriously ...

Project Avogadro seeks to change the definition of a kilogram from the weight of a hunk of metal that currently resides in France to a measurement based on fundamental constants (like every other unit ...

SINGAPORE — A kilogram is hard to fathom. It is a unit of mass, but humans can only sense force and not mass, hence the frequent confusion between mass and weight, which is a type of force, said Mr ...