View source for Moonlight

{{short description|Light that reaches Earth from the Moon}}
{{other uses|Moonlight (disambiguation)}}
[[File:Holma Boat Club by the light of the moon.jpg|thumb|250px|Moonlight illuminates a boat club in [[Holma, Lysekil Municipality|Holma]], Sweden.]]

'''Moonlight''' consists of mostly [[sunlight]] (with little [[earthlight (astronomy)|earthlight]]) reflected from the parts of the [[Moon|Moon's]] surface where the [[Sun|Sun's]] light strikes.<ref name=Toomer>{{Cite journal|first=G. J.|last=Toomer|author-link=G. J. Toomer|title=Review: ''Ibn al-Haythams Weg ur Physik'' by Matthias Schramm|journal=[[Isis (journal)|Isis]]|volume=55|issue=4|date=December 1964|pages=463–465 [463–4]|doi=10.1086/349914}}</ref>

==History==
The ancient Greek philosopher [[Anaxagoras]] was aware that "''the sun provides the moon with its brightness''".<ref>Fragment in Plutarch De facie in orbe lunae, 929b, as quoted in "The Riverside Dictionary of Biography" (2005), p. 23</ref>

[[Zhang Heng]]'s treatise "''The Spiritual Constitution of the Universe''" concludes that the light of the moon comes from the Sun. He writes that the Sun and Moon are "like fire and water" where the Sun "gives out light" and the Moon "reflects it".  <ref>Dinwiddie, R., Hughes, D. W., Jackson, T., Johnson, P., Mitton, J. (2017). The Astronomy Book. DK Big Ideas. p.23</ref>

==Illumination==
The intensity of moonlight varies greatly depending on the [[lunar phase]], but even the [[full moon]] typically provides only about 0.05–0.1&nbsp;[[lux]] illumination.<ref name=supermoon>{{cite journal |last1=Kyba |first1=Christopher C M |last2=Mohar |first2=Andrej |last3=Posch |first3=Thomas |title=How bright is moonlight? |journal=[[Astronomy & Geophysics]] |date=1 February 2017 |volume=58 |issue=1 |pages=1.31–32 |doi=10.1093/astrogeo/atx025 |url=https://academic.oup.com/astrogeo/article-abstract/58/1/1.31/2938119/How-bright-is-moonlight-Moonlight |access-date=14 February 2017}}</ref> When a full Moon around [[apsis|perigee]] (a "[[supermoon]]") is viewed around upper [[culmination]] from the [[tropics]], the [[illuminance]] can reach up to 0.32&nbsp;lux.<ref name=supermoon/> From Earth, the [[apparent magnitude]] of the full Moon is only about {{fract|1|380,000}} that of the [[Sun]].{{citation needed|date=December 2017}}

The color of moonlight, particularly around full moon, appears bluish to the [[human eye]] compared to other, brighter light sources due to the [[Purkinje effect]]. The blue or silver appearance of the light is an [[illusion]]. 

The Moon's [[Bond albedo]] averages 0.136,<ref name="Saari">{{cite journal |doi=10.1364/AO.47.004981 |title=Celestial body irradiance determination from an underfilled satellite radiometer: application to albedo and thermal emission measurements of the Moon using CERES |year=2008 |last1=Matthews |first1=Grant |journal=[[Applied Optics]] |volume=47 |pages=4981–93 |pmid=18806861 |issue=27 |bibcode=2008ApOpt..47.4981M |title-link=Clouds and the Earth's Radiant Energy System}}</ref> meaning only 13.6% of incident sunlight is reflected from the lunar surface. Moonlight takes approximately 1.26 seconds to reach Earth's surface. [[light scattering by particles|Scattered]] in [[atmosphere of Earth|Earth's atmosphere]], moonlight generally increases the [[sky brightness|brightness]] of the [[night sky]], reducing [[contrast (vision)|contrast]] between dimmer stars and the background. For this reason, many [[astronomer]]s usually avoid [[observational astronomy|observing]] sessions around a full moon.

==Gallery==
<gallery>
File:ISS-44 Moon - Goodnight Earth.jpg|Moonlight onto Earth's cloud cover from space
File:Sunrise over the VLT.jpg|Moonlight shines on the [[Very Large Telescope]].
File:Tonsvatnet, tåke og måne.JPG|Moonlight illuminates a lake and surroundings.
File:Giftedtypist - red moon (by).jpg|During a [[lunar eclipse]], the Moon is colored red by indirect [[sunlight]], which [[Earth's atmosphere]] has [[light scattering|scattered]] and [[atmospheric refraction|refracted]].
File:Earthshine Moon.jpg|[[earthlight (astronomy)|Earthlight]] (indirect sunlight reflected from Earth) illuminates the dim side of the Moon, while direct sunlight illuminates the bright side.
File:High ISO with long exposure.jpg|With manual [[exposure (photography)|exposure]] settings, photographs taken in moonlight do not appear much different from those taken in [[daylight]].
</gallery>

==Folklore==
In folklore, moonlight sometimes has a harmful influence. For example, sleeping in the light of a full Moon on certain nights was said to transform a person into a [[werewolf]]. The light of the Moon was thought to worsen the symptoms of [[lunatics]], and to sleep in moonlight could make one blind, or mad.<ref>''A Dictionary of English Folklore'', Oxford University Press, 2000</ref> [[Nyctalopia]] (night blindness caused by a lack of vitamin A) was thought to be caused by sleeping in moonlight in the tropics.

"[[Moon blindness]]" is a name for equine recurrent uveitis. Moonlight is no longer thought of as the cause.

In the 16th century, [[moonmilk]], a soft white limestone precipitate found in caves, was thought to be caused by the rays of the Moon.<ref name=Gessner>{{cite book |last=Gessner |first=Conrad |author-link=Conrad Gessner |title=Descriptio Montis Fracti sive Montis Pilati |trans-title=Description of Mount Fractus, or Mount Pilatus |date=1555 |language=la |page=54 |url=http://gallica.bnf.fr/ark:/12148/bpt6k93851n/f59 |access-date=March 12, 2016}}</ref>

[[Selenoplexia]] was a supposed medical condition caused by the rays of the moon.<ref name=Lippincott>''Lippincott's Medical dictionary'' (Lippincott, 1906), p. 920.</ref>

==Art==
<gallery mode="packed">
File:Joseph Vernet - Night - Seaport by Moonlight - WGA24731.jpg|''Seaport by Moonlight'' (1771) by [[Claude Joseph Vernet]]
Image:Joseph Wright of Derby - Dovedale by Moonlight - Google Art Project.jpg|''[[Dovedale by Moonlight]]'' (1784) by [[Joseph Wright of Derby]]
File:Philippe-Jacques de Loutherbourg - A Philosopher in a Moonlit Churchyard.jpg|''[[Visitor to a Moonlit Churchyard]]'' (1790) by [[Philip James de Loutherbourg]]
File:Ed. Manet. Clair de lune sur le port de Boulogne.jpg|''[[The Port of Boulogne by Moonlight]]'' (1869) by [[Édouard Manet]]
File:Van Gogh - Starry Night - Google Art Project.jpg|''[[The Starry Night]]'' (1889) by [[Vincent van Gogh]]
File:Stanisław_Witkiewicz_-_Wiatr_halny_1895.jpg|''Halny'' (1895) by [[Stanisław Witkiewicz]]
</gallery>

In 2008 [[Katie Paterson]] produced an artwork titled ''Light bulb to Simulate Moonlight''.<ref name=guggenheimPaterson /> It consists of 289 lightbulbs coated to produce a similar spectrum to the light of the full Moon.<ref name=guggenheimPaterson>{{cite web |url=https://www.guggenheim.org/artwork/28089 |title=Katie Paterson Light bulb to Simulate Moonlight |website=guggenheim.org |publisher=Solomon R. Guggenheim Foundation |access-date=29 January 2019}}</ref>

==See also==
{{Portal|Solar System}}
*[[Airglow]]
*[[Daylight]]
*[[Diffuse reflection]]
*[[Earthlight (astronomy)]]
*[[Lunar effect]]
*[[Scotobiology]]
*[[Starlight]]
*[[Night in paintings (Western art)]]
*[[Night in paintings (Eastern art)]]

==References==
{{reflist}}

==External links==
{{wiktionary|moonlight}}
{{commons category}}
* [http://aa.usno.navy.mil/data/docs/MoonPhase.html Phases of the Moon] {{Webarchive|url=https://web.archive.org/web/20110709100302/http://aa.usno.navy.mil/data/docs/MoonPhase.html |date=2011-07-09 }} at [[USNO]]
* [https://web.archive.org/web/20101004003005/http://science.nasa.gov/science-news/science-at-nasa/2006/28sep_strangemoonlight/ Strange Moonlight] at [https://science.nasa.gov/ Science@NASA]
* [https://web.archive.org/web/20130202083251/http://home.earthlink.net/~kitathome/LunarLight/moonlight_gallery/technique/moonbright.htm Moonlight Brightness] at [https://web.archive.org/web/20100311001241/http://home.earthlink.net/~kitathome/LunarLight/index.html LunarLight Photography]

{{The Moon|state=expanded}}
{{Parts of a day}}

[[Category:Lunar observation]]
[[Category:Light]]
[[Category:Light sources]]