Editing Langley (unit)

{{refimprove|date=August 2010}}
{{Infobox unit
| bgcolor      = 
| name         = langley
| image        = 
| caption      = 
| standard     = Non-SI metric unit
| quantity     = [[Heat flux]]
| symbol       = Ly
| namedafter   = [[Samuel Langley]]
| extralabel   = Derivation
| extradata    = 1 cal<sub>th</sub>/cm<sup>2</sup>
| units1       = SI units
| inunits1     = 41 840 J/m<sup>2</sup>
}}

The '''langley''' (Ly) is a unit of heat transmission, especially used to express the rate of [[solar radiation]] (or [[insolation]]) received by the earth. The unit was proposed by [[Franz Linke]] in 1942<ref>{{cite encyclopedia|last=Gyllenbok|first=Jan|author-link=Jan Gyllenbok|editor-last=|editor-first=|editor-link=|encyclopedia=Encyclopaedia of Historical Metrology, Weights, and Measures, Volume 1|title=langley|language=|edition=|year=2018|publisher=Birkhäuser|series=|location=|id=|isbn=9783319575988|oclc=|doi=|page=139|quote=}}</ref> and named after [[Samuel Langley]] (1834–1906) in 1947.

==Definition==
One langley is 
*1 [[Calorie|thermochemical calorie]] per [[square centimetre]],<ref name=nistguide>{{Cite web|authorlink=A. Thompson and B. N. Taylor|title=Appendix B9. Conversion Factors.|work=NIST Guide to the [[International System of Units|SI]]|publisher=The National Institute of Standards and Technology|date=2010-10-05|url=http://physics.nist.gov/Pubs/SP811/appenB9.html|accessdate=2013-04-14}}</ref>
*41 840 J/m<sup>2</sup> ([[joule]]s per [[square metre]])<ref>{{cite web|url=http://www.racerocks.com/racerock/abiotic/solar/solar.htm|title=Solar Energy at Race Rocks|access-date=2010-08-05|archive-url=https://web.archive.org/web/20131005002713/http://www.racerocks.com/racerock/abiotic/solar/solar.htm|archive-date=2013-10-05|url-status=dead}}</ref>

== See also ==
* [[Solar constant]]
* [[Radiant exposure]]

==References==
{{Reflist}}

[[Category:Units of measurement]]
[[Category:Non-SI metric units]]


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