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13 August 2009

The definition of the standard metre (meter)

Remember the SI units we learn in physics lessons way back in our high school years?

The length that set the standards for the meter we use was actually a platinum bar now still kept in France.

But since October 20th 1960 (exactly 29 years before I was born) The length for the standard metre has been redefined in the 11th General Conference on Weights and Measures as:

"1,650,763.73 wavelengths in vacuum of the radiation (light) corresponding to the transition between the 2p10 and 5d5 quantum levels of the Krypton-86 atom."

Using the multiple distance of wavelengths of light to measure distance, now that's precision!

1 comment:

Anonymous said...

interesting blog.

btw, correct me if i'm wrong. 1 meter is no longer defined using Kr-86 but rather by speed of light? ie the distance travelled by light in vacuum during a time interval of (1/Cknot) of a second.