# Moonlight
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{{short description|Light that reaches Earth from the Moon}}
{{other uses|Moonlight (disambiguation)}}
thumb|Earthlight illuminates the dim side of the Moon, while direct sunlight illuminates the bright side.
'''Moonlight''' (or '''moonshine''') is light from the surface of the [Moon](/source/Moon), consisting mostly of reflected [sunlight](/source/sunlight), and some [earthlight](/source/earthlight).[{{Cite journal|first=G. J.|last=Toomer|author-link=G. J. Toomer|title=Review: ''Ibn al-Haythams Weg zur Physik'' by Matthias Schramm|journal=[Isis](/source/Isis_(journal))|volume=55|issue=4|date=December 1964|pages=463–465 [463–4]|doi=10.1086/349914}}]
==History==
The ancient Greek philosopher [Anaxagoras](/source/Anaxagoras) noted that "the sun provides the moon with its brightness".[Fragment in Plutarch De facie in orbe lunae, 929b, as quoted in ''The Riverside Dictionary of Biography'' (2005), p. 23] Ancient Chinese polymath [Zhang Heng](/source/Zhang_Heng) concluded that the light of the Moon comes from the Sun. He writes in his treatise, ''The Spiritual Constitution of the Universe'', that the Sun and Moon are "like fire and water", where the Sun "gives out light", and the Moon "reflects it".[Dinwiddie, R., Hughes, D. W., Jackson, T., Johnson, P., Mitton, J. (2017). The Astronomy Book. DK Big Ideas. p.23]
[Nyctalopia](/source/Nyctalopia) was called "moonblink" and thought to be caused by sleeping in moonlight in the tropics as late as the 19th century,[{{Cite book |last=Smyth |first=W. H. |url=https://www.gutenberg.org/ebooks/26000 |title=The Sailor's Word-Book |publisher=Blackie and Son |year=1867 |isbn=0851779727 |pages=483}}] but is actually caused by a deficiency in [Vitamin A](/source/Vitamin_A). Moonlight was historically thought to cause [equine recurrent uveitis](/source/equine_recurrent_uveitis), which was called "moon blindness".{{cn|date=July 2025}} [Moonmilk](/source/Moonmilk), a soft white limestone precipitate found in caves, was thought to be caused by the rays of the Moon.[{{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}}] [Selenoplexia](/source/Selenoplexia) was a supposed medical condition caused by the rays of the Moon.[''Lippincott's Medical dictionary'' (Lippincott, 1906), p. 920.]
==Illumination==
Moonlight illuminates a lake and surroundings.|thumb|left
The color of moonlight appears bluish or silvery to the [human eye](/source/human_eye) compared to other, brighter light sources, however this is an illusion, due to the [Purkinje effect](/source/Purkinje_effect): the spectrum has slightly more long-wavelength (red) light than daylight,[{{cite book| last = Barrow| first = John| author-link = John D. Barrow| title = The Artful Universe| url = https://archive.org/details/the-artful-universe-john-barrow/page/208/mode/1up| publisher = [Oxford University Press](/source/Oxford_University_Press)| edition = expanded| location = New York| date = 2005| pages = 208-209}}] but is almost the same as that of the sun.[{{cite book| last = Vavilov| first = S. I.| author-link = Sergey Vavilov| title = The Human Eye and Sun - Hot and Cold Light| url = https://archive.org/details/the-human-eye-and-sun-hot-and-cold-light-s-i-vavilov/page/102/mode/1up?q=%22spectrum+of+moonlight%22| publisher = [Pergamon Press](/source/Pergamon_Press)| edition = 1st| location = Oxford| date = 1965| page = 102}}] The intensity of moonlight varies greatly depending on the [lunar phase](/source/lunar_phase), with the [full moon](/source/full_moon) typically providing about 0.05–0.1 [lux](/source/lux) illumination.[{{cite journal |last1=Kyba |first1=Christopher C M |last2=Mohar |first2=Andrej |last3=Posch |first3=Thomas |title=How bright is moonlight? |journal=[Astronomy & Geophysics](/source/Astronomy_%26_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}}] When a full Moon at [perigee](/source/apsis) (a "[supermoon](/source/supermoon)") is viewed around upper [culmination](/source/culmination) from the [tropics](/source/tropics), the [illuminance](/source/illuminance) can reach up to 0.32 lux.[ From Earth, the [apparent magnitude](/source/apparent_magnitude) of the full Moon is only about {{fract|1|380,000}} that of the [Sun](/source/Sun), and the wavelength pattern is different.][{{cite journal |last1=Breitler |first1=J-C. |last2=Djerrab |first2=D. |last3=Leran |first3=S. |last4=Toniutti |first4=L. |last5=Guittin |first5=C. |last6=Severac |first6=D. |last7=Pratlong |first7=M. |last8=Dereeper |first8=A. |last9=Etienne |first9=H. |last10=Bertrand |first10=B. |title=Full moonlight-induced circadian clock entrainment in Coffea arabica |journal=[BMC Plant Biology](/source/BMC_Plant_Biology) |date=December 2020 |volume=20 |issue=1 |doi=10.1186/s12870-020-2238-4 |doi-access=free|url=https://pmc.ncbi.nlm.nih.gov/articles/PMC6961272/figure/Fig1/ |pmc=6961272 }}] The Moon's [Bond albedo](/source/Bond_albedo) averages 0.136,[{{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](/source/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}}] meaning only 13.6% of incident sunlight is reflected from the lunar surface. Moonlight takes approximately 1.26 seconds to reach Earth's surface. Moonlight is [scattered by particles](/source/light_scattering_by_particles) in the [atmosphere of Earth](/source/atmosphere_of_Earth), which increases the [brightness](/source/sky_brightness) of the [night sky](/source/night_sky), and decreases [contrast](/source/contrast_(vision)) between [dimmer stars and the background](/source/Limiting_magnitude). For this reason, many [astronomer](/source/astronomer)s usually avoid [observing](/source/observational_astronomy) the sky around a full moon.{{cn|date=July 2025}}
==Lunar eclipse==
[[File:Lunar eclipse 04-15-2014 by R Jay GaBany.jpg|thumb|Composite image of the [April 2014 total lunar eclipse](/source/April_2014_lunar_eclipse) from [Charleston, West Virginia](/source/Charleston%2C_West_Virginia), United States.]]
A [lunar eclipse](/source/lunar_eclipse) is an [astronomical event](/source/astronomical_event) that occurs when the [Moon](/source/Moon) moves into the [Earth's shadow](/source/Earth's_shadow), causing the moonlight to be darkened.[{{Cite web |url=http://earthsky.org/tonight/centurys-longest-lunar-eclipse-july-27 |title=Century's Longest Lunar Eclipse July 27 |last=McClure |first=Bruce |date=27 July 2018 |website=[EarthSky](/source/EarthSky) |access-date=1 August 2018}}] Such an alignment occurs during an [eclipse season](/source/eclipse_season), approximately every six months, during the [full moon](/source/full_moon) phase, when the Moon's orbital plane is closest to [the plane of the Earth's orbit](/source/Ecliptic).
When the Moon is totally eclipsed by the Earth (a "deep eclipse"),[{{cite web |author=Staff |title=PHYS 1350 Astronomy Exam 3 (TXST-Olson) |url=https://quizlet.com/341047631/phys-1350-astronomy-exam-3-txst-olson-flash-cards/ |date=2023 |work=[Quizlet](/source/Quizlet) |url-status=live |archiveurl=https://archive.today/20231109125204/https://quizlet.com/341047631/phys-1350-astronomy-exam-3-txst-olson-flash-cards/ |archivedate=9 November 2023 |accessdate=9 November 2023 }} "What is a deep eclipse? The smaller star is behind the bigger star"][{{cite news |author=Miller, A.M. |display-authors=et al.|title=ATel #16328 - ASASSN-23ht: A Deep Eclipse Event |url=https://www.astronomerstelegram.org/?read=16328 |date=7 November 2023 |work=[The Astronomer's Telegram](/source/The_Astronomer's_Telegram) |url-status=live |archiveurl=https://archive.today/20231109132351/https://www.astronomerstelegram.org/?read=16328 |archivedate=9 November 2023 |accessdate=9 November 2023 }}] it takes on a reddish color that is caused by the planet when it completely blocks direct [sunlight](/source/sunlight) from reaching the Moon's surface, as the only light that is [reflected](/source/diffuse_reflection) from the lunar surface is what has been [refracted](/source/atmospheric_refraction) by the [Earth's atmosphere](/source/Earth's_atmosphere). This light appears reddish due to the [Rayleigh scattering](/source/Rayleigh_scattering) of blue light, the same reason sunrises and sunsets are more orange than during the day.
{{clear}}
==Folklore==
Moonlight was sometimes thought to have a harmful influence in folklore. For example, sleeping in the light of a full moon was believed to transform a person into a [werewolf](/source/werewolf). The light of the Moon was thought to worsen the symptoms of [lunatics](/source/lunatics), and to sleep in moonlight could make one blind, or mad.[''A Dictionary of English Folklore'', Oxford University Press, 2000]
==Art==
{{further|Night in paintings (Western art)|Night in paintings (Eastern art)}}
[Katie Paterson](/source/Katie_Paterson) produced a display at [The Guggenheim](/source/The_Guggenheim) in 2008, entitled ''Light bulb to Simulate Moonlight'', which consisted of 289 lightbulbs coated to produce a similar spectrum to the light of the full Moon.[{{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}}]
File:Vernet, Claude Joseph - Seaport by Moonlight - 1771.JPG|''[Seaport by Moonlight](/source/Seaport_by_Moonlight)'' (1771) by [Claude Joseph Vernet](/source/Claude_Joseph_Vernet)
Image:Joseph Wright of Derby - Dovedale by Moonlight - Google Art Project.jpg|''[Dovedale by Moonlight](/source/Dovedale_by_Moonlight)'' (1784) by [Joseph Wright of Derby](/source/Joseph_Wright_of_Derby)
File:Philippe-Jacques de Loutherbourg - A Philosopher in a Moonlit Churchyard.jpg|''[Visitor to a Moonlit Churchyard](/source/Visitor_to_a_Moonlit_Churchyard)'' (1790) by [Philip James de Loutherbourg](/source/Philip_James_de_Loutherbourg)
File:Ed. Manet. Clair de lune sur le port de Boulogne.jpg|''[The Port of Boulogne by Moonlight](/source/The_Port_of_Boulogne_by_Moonlight)'' (1869) by [Édouard Manet](/source/%C3%89douard_Manet)
File:Stanisław_Witkiewicz_-_Wiatr_halny_1895.jpg|''Halny'' (1895) by [Stanisław Witkiewicz](/source/Stanis%C5%82aw_Witkiewicz)
==Gallery==
File:ISS-44 Moon - Goodnight Earth.jpg|Moonlight onto Earth's cloud cover from space
File:Earth From the Perspective of Artemis II.jpg|Moonlight illuminating the Earth in the ''[Hello, World](/source/Hello%2C_World_(photograph))'' photograph ([Artemis II](/source/Artemis_II), 2026)
File:Sunrise over the VLT.jpg|Moonlight shines on the [Very Large Telescope](/source/Very_Large_Telescope).
File:Holma Boat Club by the light of the moon.jpg|Moonlight illuminates a boat club in [Holma](/source/Holma%2C_Lysekil_Municipality), Sweden.
File:High ISO with long exposure.jpg|With manual [exposure](/source/exposure_(photography)) settings, photographs taken in moonlight do not appear much different from those taken in [daylight](/source/daylight).[
]
==See also==
{{Portal|Solar System}}
*[Airglow](/source/Airglow)
*[Daylight](/source/Daylight)
*[Diffuse reflection](/source/Diffuse_reflection)
*[Lunar effect](/source/Lunar_effect)
*[Scotobiology](/source/Scotobiology)
*[Starlight](/source/Starlight)
==References==
{{reflist|2}}
==External links==
{{Commons category|Moonlight}}
{{Wiktionary}}
*[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](/source/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:Light
Category:Light sources
Category:Lunar observation
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Adapted from the Wikipedia article [Moonlight](https://en.wikipedia.org/wiki/Moonlight) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Moonlight?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.