Over the centuries a ‘kilogram’ has been defined and redefined. But the standard since 1889 is known as ‘Le Grand K’, a cylinder of platinum-iridium. It is kept inside a jar at the International Bureau of Weights and Measures (BIPM) in Sèvres, France. For close to 130 years now, this cylinder’s mass is considered as an international standard for the kilogram.
However, all that could change now. A number of representatives will vote on Friday in Versailles to redefine the International System of Units or SI. As per reports, the new definition will be voted in at the meeting. The kilogram is among four fundamental units that are being reconsidered.
Apart from the kilogram, the others are the ampere (current), the Kelvin (temperature) and the mole (amount of substance). The definition of the kilogram will be based on a concept of physics known as the Planck constant.
The step has become a necessity since scientists want to come out with a measurement system which is based on unchanging fundamental properties of nature. Le Grand K, the “international prototype kilogram”, is the last object which was used to define an SI unit.
As a physical object, it is hard to change in weight. But it can get dusty or can be affected by the atmosphere. Cleaning it may change its weight, however minutely.
Source: financialexpress.com
