Andrew S. Tannenbaum
Watch out for the weight next time you step out to buy grocery because the kilogram just got a little lighter. "Le Grand K" - the cylinder of platinum & iridium is the only object known to scientists that has a mass of exactly 1 kg. It is the reference object from which the unit of mass is derived. All objects measured in kilograms - grocery to a warship are defined by Le Grand K's mass.
Several copies have been distributed across the world to act as arbiters of mass. They are measured against Le Grand K to ensure the integrity.
Losing some weight
But there is a fluctuation of mass between the sisters with either the Le Grand K losing some mass or others gaining some. However as they all are measured against each other, finding out the "one" is difficult.
Common man can however lay to rest his concerns as the fluctuations are about 50 parts in a billion. Although tiny, the difference is crucial to scientific community as these cylinders act as reference for kilogram.
New standards
As a outcome of the drift scientists are devising new ways of defining the kilogram. The basic idea is to measure kilogram in terms of constants of nature just the way a meter is defined as the distance traveled by light in vacuum in a precise fraction of a second. Another idea may be to redefine the kilogram on the basis of the mass of an atom.
What ever it may be one thing is sure - the small lump of metal in Paris is going to be used for some time to come.Image Credits: Wikipedia
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