Chunk of metal known as ‘Grand K’ is now officially retired as the world’s only true kilogram
- About 50 nations vote to overhaul the international system of measurements
- New formula for the kilogram seen as more accurate when measuring very small or very large masses
In a historic vote, nations on Friday unanimously approved a groundbreaking overhaul to the international system of measurements that underpins global trade and other vital human endeavours, uniting together behind new scientific definitions for the kilogram and other units in a way that they have failed to do on so many other issues.
Scientists, for whom the update represents decades of work, clapped, cheered and even wept as the 50-plus nations gathered in Versailles, west of Paris, one by one said “yes” or “oui” to the change, hailed as a revolution for how humanity measures and quantifies its world.
The redefinition of the kilogram, the globally approved unit of mass, was the mostly hotly anticipated change. For more than a century, the kilogram has been defined as the mass of a cylinder of platinum-iridium alloy kept in a high-security vault in France. That artefact, nicknamed “Le Grand K”, has been the world’s sole true kilogram since 1889.
But now, with the vote, the kilogram and all of the other main measurement units will be defined using numerical values that fit handily onto a wallet card. Those numbers were read to the national delegates before they voted.
Scientists at the meeting were giddy with excitement: some even sported tattoos on their forearms that celebrated the science.
Nobel Prize winner William Phillips called the update “the greatest revolution in measurement since the French Revolution”, which ushered in the metric system of metres and kilograms.