Science Blog ZINC PROJECTS
Redefining kilogram
Date: 27-Feb-08
Author: Sandia National Laboratories
The kilogram is losing weight and many international scientists agree that it's time to redefine it.
Scientists are hoping to redefine the kilogram by basing it on standards of universal constants rather than on an artifact standard.
The International Prototype Kilogram (IPK) or "Le Grand K," made in the 1880s, is a bar of platinum-iridium alloy kept in a vault near Paris.
International Prototype Kilogram (IPK) or "Le Grand K". Courtesy: Bureau International des Poids et Mesures
Of the seven units of measurement in the International System, or SI, the kilogram is the only base still defined by a physical object. In addition, copies of the kilogram have changed over time by either gaining or losing weight as compared to the standard kilogram.
The purpose of redefining the kilogram is based on risk reduction ... By replacing the master kilogram -- Le Grand K -- with a unit based on physical constants, researchers at multiple laboratories and at national measurement institutes could establish traceability.
The earliest the kilogram would be redefined is 2011.
Full story: Sandia weighs in on new definition for kilogram
Related links:
• International Prototype Kilogram
• FAQs about the kilogram
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