In 2019, the kilogram will get more accurate. For 125 years, a salt-shaker-sized cylinder housed at the Bureau International des Poids et Mesures (BIPM), Paris and weighing exactly a kilogram served as the definition of the measure. India’s National Physical Laboratory too has a replica of this, since 1957, and it has served as the reference for a variety of industries to keep their weights accurate.
However an international conference of heads of metrology institutes decided, on October 19 in Sevres, France, that the kilogram will no longer be pegged to this cylinder made of 90% platinum and 10% iridium.
In the last 60 years, several standard units — the second, metre, ampere, Kelvin, mole, candela and, the kilogram — have all ceased to be defined by physical objects.
One metre, for instance, was a platinum-iridium bar of that measure. In 1960, the metre was defined as the distance travelled by light in vacuum in 1/299,792,458 seconds.