At 02:41 PM 6/29/2012, Scott Daniel - Turbovans wrote: >Where did they derive that dimension from ? As Mike said...but the actual definition from 1889 to 1960 was the distance between two scribed lines on a platinum-iridium bar kept at the International Bureau of Weights and Measures in France, measured at the melting point of ice. In 1960 it was redefined in terms of the wavelength of a particular emission line in the spectrum of krypton-86, and in 1983 redefined once again as the distance light travels in vacuum in a specific time (roughly one three hundred millionth of a second). Here's a photo of the working end of one of the original prototype metre bars, specifically the one that was the US National standard for the meter until 1960. http://museum.nist.gov/object.asp?ObjID=37 Yours, David |
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