Perfect Si sphere as new kilogram standard?

Australian scientists are developing a perfect Silicon sphere for consideration as the successor to the old kilogram standard.

The project requires the development of perfect silicon spheres, and optical engineers at CSIRO's Australian Centre for Precision Optics — considered world leaders in the craft — are doing their part.

Scientists will use the spheres to determine how many silicon atoms make up a kilogram, and this will be used as the new definition — bringing the kilogram into line with other base units such as the metre and the second, which are all defined by physical constants.

See The Age.