File:Platinum-Iridium meter bar.jpg

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International Prototype Metre standard bar made of platinum-iridium. This was the standard until 1960, when the new SI system used a krypton-spectrum measurement as the base. In 1983 the current metre was defined by a relationship to the speed of light in a vaccuum. (NIST)

http://www.mel.nist.gov/div821/webdocs-14/lsi_2.htm

Public domain This image is in the public domain because it contains materials that originally came from the National Institute of Standards and Technology.
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current15:18, 1 May 2005Thumbnail for version as of 15:18, 1 May 2005270×175 (21 KB)Svdmolen (Talk | contribs) (International Prototype Metre standard bar made of platinum-irridium. This was the standard until 1960, when the new SI system used a krypton-spectrum measurement as the base. In 1983 the current metre was defined by a relationship to the speed of light i)

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