Definition of kilogram changed after nearly 130 years
Scientists on Friday unanimously voted to redefine kilogram, retiring the platinum alloy cylinder conceived in Paris in 1889. Redefined by the Planck constant, the new system determines the unit of mass through the electrical force needed to counteract the weight of a kilogram on a Kibble balance. The changes will come into effect from May 20, 2019, World Metrology Day.