Precision work: Defect-free coatings for silicon spheres

The prototype kilogram – to which all scales are calibrated to – is losing weight. International efforts are striving to redefine the base unit for measuring mass and, in future, redefine the kilogram on natural constants. For this purpose, the Avogadro experiment determines the number of atoms in almost perfect silicon spheres. Researchers have recently succeeded in homogeneously coating the spherical surfaces – the measurement uncertainty can be limited to a range below 10 mi