Kilogram standard slowly losing mass: ; Scientists trying to devise new way to calculate measurement

To fix the kilogram, one group of physicists is trying to define mass based on voltage, resistance and other electromagnetic measurements. A second group wants to make a perfect sphere of silicon; by counting the number of atoms in it more accurately than ever, the scientists hope to arrive at a new...

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Bibliographic Details
Published inSunday gazette-mail
Main Author Witze, Alexandra
Format Newspaper Article
LanguageEnglish
Published Charleston, W.V Charleston Newspapers 24.11.2002
Subjects
Davis, Richard
De Bievre, Paul
Kibble, Bryan
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Summary:To fix the kilogram, one group of physicists is trying to define mass based on voltage, resistance and other electromagnetic measurements. A second group wants to make a perfect sphere of silicon; by counting the number of atoms in it more accurately than ever, the scientists hope to arrive at a new mass standard. Scientists at the Institute for Crystal Growth in Berlin will soon make test crystals of silicon-28 to see how the material behaves. The project could have its kilogram replacement as soon as six years from now, said [Paul De Bievre]. The apparatus works by balancing the force of gravity pulling down on a 1-kilogram mass against an upward-pulling magnetic force. The device can indirectly define the kilogram because all the other units measured - such as time, length, voltage and resistance - are already precisely defined.