At <http://www.metrication.us> the assertion is made that
The International Prototype of the kilogram "... is set to be replaced by a
perfect silicon crystal sphere developed by scientists at Australia's CSIRO."
Although the article on the sphere of silicon 28 is impressive, the assertion,
on adoption of the sphere as the redefinition of the kilogram, is premature.
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Gene,
The redefinition of the kilogram will be considered at the next meeting of the
CGPM in 2011. It is my understanding that the Avogadro Experiment has not been
chosen above the Watt Balance Experiment (or visa versa) to redefine the
kilogram. I understand that a redefinition will not move forward until a
project achieves uncertainties similar to the current realization method.
Agreement among the multiple Watt Balance experiment uncertainties must also
occur.
The BIPM website gives a nice synopsis on the topic
(http://www.bipm.org/en/scientific/elec/watt_balance/). The BIPM website
states:
"Taking into account the required uncertainty mentioned above and the levels of
performance reached up to now by the different techniques we believe that the
watt balance is a very promising candidate for a future redefinition of the
kilogram."
Best regards,
Elizabeth
Elizabeth J. Gentry
National Institute of Standards and Technology
Weights and Measures Division
Laws and Metric Group
100 Bureau Drive Stop 2600
Gaithersburg, Maryland 20899-2600
301-975-3690 Fax: 301-975-8091
http://www.nist.gov/metric
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Tuesday, April 29, 2008 2:41 PM
To: Elizabeth Gentry
Subject: kilogram of Silicon 28
Elizabeth,
At HYPERLINK "http://www.metrication.us/"www.metrication.us , I found the
statement: "120 year old cylinder that defines the world standard for one
kilogram to be replaced by sphere of silicon 28"
Browsing NIST Web pages reveals no indication of the 2008 status of the Silicon
28 sphere proposed by Australia's Centre for Precision Optics as the new SI
standard of mass.
What is the prospect of adoption by the CIPM and the CGPM?
Gene Mechtly.
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