New definition of kilogram on the cards

New research results by scientists can lead to a redefinition of the measurement of a kilogram.

Washington, Nov 2 : New research results by scientists can lead to a redefinition of the measurement of a kilogram.

The kilogram is the last International system of units (SI) unit based on a manufactured object and is the foundation for all the measurements.

SI units are defined by the General Conference on Weights and Measures, whose next meeting this month will consider a range of issues related to the maintenance of the SI. This will include an initial proposal to prepare for the redefinition of several of the base units.

This meeting could also include redefining mass relying on a physical constant - a physical quantity that is universal in nature and constant in time.

For 30 years, scientists across the world have been looking to measure the value of a physical constant as accurately as possible using the existing man-made unit for a kilogram. Once they have achieved this, the fixed value of one of these constants can be incorporated it into a new definition of the kilogram.

The research has been going on with a method known as Planck's constant, which uses an indirect comparison of mechanical and electrical power to measure the kilogram using length, time and quantum mechanical effects.

For the proper redefinition of the kilogram, it is necessary that no differences crop up in the results of the research. But, research from the UK's National Physical Laboratory (NPL) measuring Planck's constant using its Mark 2 watt balance show a significant discrepancy in the results.

According to Seton Bennett, Deputy Director at the National Physical Laboratory, "Given the inconsistency in these results, further results are required before the CGPM ( Conférence Générale des Poids et Mesures) could consider adopting a new definition for the kilogram. A decision to replace the International Prototype with a definition based on Planck's constant requires substantially more research by laboratories across the world, building on the strong foundations already laid by the National Physical Laboratory and its international partners."

ANI