The Verge:
Nearly every measurement of weight you’ve ever made, from peeking at your bathroom scale to measuring out flour for a recipe, can be traced back to just a single object: a metal kilogram made of platinum and iridium that resides under lock and key in an underground vault in Paris. It’s called the International Prototype Kilogram, or IPK, and since its creation in 1889 it has been the standard by which the world’s weights are defined. But not for much longer.
But later this week, on Friday, November 16th, a coup is planned in this international ministry of weights. After having served for 129 years as the world’s standard, the International Prototype Kilogram (or Le Grand K, as it’s known locally) will be stood down. Grandees of the International Bureau of Weights and Measures, which regulates the metric system, will gather in Versailles and vote to replace this physical artifact with a definition of the kilogram based on a fundamental constant of nature.
I’ve been following this weirdly fascinating story for years. I loved the idea that an international measurement was represented in reality by one example of it deep in a lab vault in France. I’ll be a little sad when it gets replaced.
I suspect it will be a long time before K, its working standard copies, and the national prototype kilograms (Knn and Knnn series) retired. They will no longer be the definitional and primary reference standards but there will still be plenty of verification and cross-checking work to be done.
I love the switch to universal constants. But I also like that the article includes criticism of the new method for determining the standard as not quite meeting the “for all people, for all times” mission statement. Whether it’s the king’s foot or an enormously costly collection of equipment and staff, access is still limited to a relative few.
The new kilogram has minimal bezels, edge to edge weight, and the gram weight attaches to the top and weighs itself when not in use.