Over a century ago, a small metal cylinder was made in London and delivered to a green suburb of Paris. The cylinder was around the size of a salt shaker and manufactured from an alloy of platinum and iridium, an innovative material at the time.
In Paris, scientists finished and weighed it cautiously, until finally they decided that it turned out exactly one kilogram, about 2.2 pounds. Then, by international treaty, they announced it to be the international standard.
Since 1889, the year the Eiffel Tower opened, that cylinder has become the standard towards which any other kilogram on the planet has been judged. But that’s making problems. With respect to scientists, the cylinder’s mass seems to be to be changing.
The remedy is a new kilogram, the one that is based upon a constant number rather than a physical object. To have that number, researchers also have to develop a specific kind of scale, one which they can measures the kilogram devoid of balancing it against another mass. It has been a lengthy, slow process, but these days they are close to redefining the kilogram once and for all.
Please Don’t Sneeze On The Kilogram
As it stands, the whole world’s method of measurement relies on the cylinder. If it is dropped, scratched or otherwise defaced, it would cause a worldwide problem. “If somebody sneezed on that kilogram standard, all the weights in the world would be instantly wrong,” says Richard Steiner, a physicist at the National Institute of Standards and Technology (NIST) in Gaithersburg, Md. For that reason, the official kilogram is kept locked inside a secured vault at the International Bureau of Weights and Measures near Paris.
