We measure stuff all the time—how long, how heavy, how hot, and so on—because we need to for things such as trade, health and knowledge. But making sure our measurements compare apples with apples has ...

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 vote to redefine the kilogram was, as expected, unanimous, with representatives from more than 50 countries saying "yes" or "oui" at the historic meeting in Versailles, France. Bill Phillips, a ...

The National Institute of Advanced Industrial Science and Technology (AIST) showed Japan's meter and kilogram prototypes to the press on Monday, ahead of the 150th anniversary later this month of the ...