This sphere was produced as part of an international project known as the Avogadro project. The goal of the Avogadro Project is to measure the value of the Avogadro constant to extreme precision, thereby allowing the mass of the kilogram to be defined in terms of the Avogadro constant. This would do away with the current physical artefact (a cylinder made of an alloy of platinum and iridium) and allow the kilogram to be reproduced in any laboratory by following a prescribed procedure.
Since 1889 the kilogram has been defined as the mass of an object known as the International Kilogram Prototype (IKP), a cylinder of platinum-iridium alloy, stored in a vault in France. In recent years, the second and metre have both been redefined in terms of fundamental physical constants, and the kilogram now remains the only standard which is still defined by a physical artefact.
In the International System of Units (SI) three other base units and 17 derived units (including the Newton, Joule, mole and Ampere) are based on the definition of the kilogram, and its stability is therefore extremely important. Comparisons of the IKP to its copies show that the masses are slowly diverging from one another, meaning the IKP is either gaining of losing weight. In 2010, these mass variations prompted scientists to begin the process of redefining the kilogram in terms of fundamental constants.
One proposed method is the Avogadro project, which aims to use perfect silicon spheres to accurately determine the value of the Avogadro constant (a fundamental physical constant), and to redefine the kilogram in terms of the Avogadro constant. There are 7 laboratories around the world participating in the Avogadro project, including laboratories in the USA, UK, Europe, and Asia. Australia and the CSIRO have played an integral part in this, being currently the only laboratory producing the silicon spheres that are used in the project. This sphere is one of the prototypes made at CSIRO for the Avogadro project. It was made by Achim Leistner, an Australian scientist, who is the Master Optician for the Avogadro project.