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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.
Originally posted by djohnsto77
Cool article, but I don't quite get why they need to create perfect spheres in order to count the atoms.
A spherical shape was chosen for the project because it has no edges that might be damaged, and the volume can be calculated by using its diameter.