"Since 1889, the year the Eiffel Tower opened, the cylinder against which every other kilogram on the planet has been judged rests inside three nested bell jars at the Bureau International des Poids et Mesures in Paris. But, according to scientists, the cylinder's mass appears to be changing.
The solution is a new kilogram, one that is based on a constant number instead of a physical object. To get that number, scientists have had to build a special kind of scale, one that measures the kilogram without balancing it against another mass. It has been a long, slow process, but today they are close to redefining the kilogram once and for all."
This fascinating story was on National Public Radio this morning. Audio for this story from Morning Edition will be available after 9 a.m.
source: National Public Radio Morning Edition
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