Kilogram will get new measure set by value of Planck constant from 2019
October 27th, 2017
The International Conference of heads of Metrology Institutes held in Sevres, France has decided that the measure of kilogram will no longer be pegged to cylinder. From 2019 onwards, it will be set by value of Planck constant in combination with definitions of meter and second. Till now, the kilogram is the only one among units of measures pegged to real object. It was pegged to a cylinder (shown in fig) made up of 90% platinum and 10% iridium (In India, salt-shaker-sized cylinder weighing exactly a kilogram in National Physical Laboratory was used as ideal measure of kilogram since 1957). It was serving as reference for variety of industries to keep their weights accurate. But this cylinder’s weight in kilogram is known to fluctuate due to surface contamination with time, making it tricky to define its exact mass.