On the outskirts of Paris, eight metres below ground in a climate-controlled vault, sits a 143-year-old platinum alloy cylinder. Standing just 39 mm tall, it has never been touched by human hands. Like a delicate Russian doll, the cylinder is caged inside three nested glass bells in a room that can be accessed only with three keys kept by three different people. Surrounding the mysterious object are “the witnesses”: six “identical” cylinders cast from the same platinum alloy.Never touched by human hands? Reprinting from 2011: = = = = = START REPRINT: Polistra is a fan of metrology, so when WUWT carried an article about a major standard of measure losing its standardness, her imagination was engaged.
In a vault beneath a 17th-century pavilion on the outskirts of Paris sits a platinum cylinder known as Le Grand K. Since 1889 it has been the international prototype for the kilogram, the standard against which all other kilos are measured. "It's a scandal that we've got this kilogram hanging around changing its mass and therefore changing the mass of everything else in the universe!" Bill Phillips, a Nobel Prize winning physicist, exclaimed at a scientific summit in London this week. No one knows for sure what went wrong with Le Grand K, but some theorize it lost weight from being cleaned.= = = = = END REPRINT.
The current icon shows Polistra using a Personal Equation Machine.