Australian scientists and optical engineers will be making a perfect sphere that may one day redefine the kilogram -- and they ... three years to produce the 20 cm long cylinder of silicon.

The perfect sphere that will be used to redefine the kilogram in terms of the Planck constant in 2018 has been shown to consist of the purest silicon ever made. The kilogram is the only unit still ...

each 93 millimetres in diameter and with a mass ofone kilogram (measured against the existing standard). The sphere's crystalline structure contains evenly spaced atoms, which allows researchers ...

A team of scientists based in Germany measured the constant by counting the atoms in a painstakingly crafted one-kilogram sphere of silicon ... Its mass is uncertain to 20 parts per billion.