{{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 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 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> (joules 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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