History of Metre

	Revision 22 . . (edit) November 12, 2001 1:39 pm by MichaelTinkler
	Revision 21 . . (edit) November 1, 2001 2:38 pm by Bryan Derksen [inserted missing "should"]
	Revision 19 . . (edit) November 1, 2001 12:34 pm by Bryan Derksen

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Difference (from prior major revision) (minor diff, author diff)

Changed: 9c9

In 1960, as lasers had become available, the 11th [General Conference on Weights and Measures]? changed the definition of metre to be the length of 1,650,763.73 wavelengths in vacuum of the orange-red emission line in the spectrum? of krypton-86. In 1983 the General Conference on Weights and Measures defined the metre as the distance traveled by light in a vacuum in 1/299,792,458 of a second (that is, the speed of light in a vacuum was defined to be 299,792,458 metres per second). Since the speed of light is believed to be constant everywhere, a definition based on light is easier to maintain and more consistent than a measurement based on the circumference of the Earth or the length of a specific metal bar. Thus, should either object be destroyed or lost, the standard meter can still be easily recreated in any laboratory.

In 1960, as lasers had become available, the 11th [General Conference on Weights and Measures]? changed the definition of metre to be the length of 1,650,763.73 wavelengths in vacuum of the orange-red emission line in the spectrum? of krypton-86. In 1983 the General Conference on Weights and Measures defined the metre as the distance traveled by light in a vacuum in 1/299,792,458 of a second (that is, the speed of light in a vacuum was defined to be 299,792,458 metres per second). Since the speed of light is believed to be constant everywhere, a definition based on light is easier to maintain and more consistent than a measurement based on the circumference of the Earth or the length of a specific metal bar. Thus, should the bar be destroyed or lost, the standard meter can still be easily recreated in any laboratory.

Changed: 13c13

Metre is a term used in the scansion of poetry, usually indicated by the kind of feet and the number of them: for instance, "iambic pentameter", "dactylic tetrameter", etc.

Metre is a term used in the scansion of poetry, usually indicated by the kind of feet and the number of them: for instance, "iambic pentameter", "dactylic tetrameter", etc. See meter in poetry.