Holma Boat Club by the light of the moon

Moonlight consists of mostly sunlight (with little

earthlight ''Earthlight'' is a science fiction novel by British writer Arthur C. Clarke, published in 1955. It is an expansion to novel length of a novella of the same name that he had published four years earlier. Overview ''Earthlight'' is a scie ...

) reflected from the parts of the Moon's surface where the Sun's light strikes.

Illumination

The intensity of moonlight varies greatly depending on the lunar phase, but even the

full Moon The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (when the ecliptic longitudes of the Sun and Moon differ by 180°). This means ...

typically provides only about 0.05–0.1 lux illumination. When a full Moon around

perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ell ...

(a "

supermoon A supermoon is a full moon or a new moon that nearly coincides with perigee—the closest that the Moon comes to the Earth in its elliptic orbit—resulting in a slightly larger-than-usual Angular diameter, apparent size of the lunar disk as v ...

") is viewed around upper culmination from the

tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referr ...

, the

illuminance In photometry (optics), photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate w ...

can reach up to 0.32 lux. From Earth, the

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

of the full Moon is only about that of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. 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 Purkinje effect (; sometimes called the Purkinje shift, often incorrectly pronounced ) is the tendency for the peak luminance sensitivity of the eye to shift toward the blue end of the color spectrum at low illumination levels as part of da ...

. The blue or silver appearance of the light is an illusion. The Moon's

bond albedo The Bond albedo (or ''spheric albedo'' or ''planetary albedo'' or ''bolometric albedo''), named after the American astronomer George Phillips Bond (1825–1865), who originally proposed it, is the fraction of power in the total electromagnetic ra ...

is 0.12, meaning only 12% of incident sunlight is reflected from the lunar surface. Moonlight takes approximately 1.26 seconds to reach Earth's surface. Scattered in

Earth's atmosphere The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing fo ...

, moonlight generally increases the

brightness Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target. The perception is not linear to luminan ...

of the

night sky The night sky is the nighttime appearance of astronomical object, celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon. Natural light sources in a ...

, reducing contrast between dimmer stars and the background. For this reason, many

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...

s usually avoid

observing Observation is the active acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the perception and recording of data (information), data via the use of scienti ...

sessions around full moon.

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 The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m acro ...

. 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

has scattered and

refracted In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...

. File:Earthshine Moon.jpg,

Earthlight ''Earthlight'' is a science fiction novel by British writer Arthur C. Clarke, published in 1955. It is an expansion to novel length of a novella of the same name that he had published four years earlier. Overview ''Earthlight'' is a scie ...

(indirect sunlight reflected from Earth) illuminates the dim side of the Moon, while direct sunlight the bright side. File:High ISO with long exposure.jpg, With manual exposure settings, photographs taken in moonlight do not appear much different from those taken in daylight.

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 In folklore, a werewolf (), or occasionally lycanthrope (; ; uk, Вовкулака, Vovkulaka), is an individual that can shapeshift into a wolf (or, especially in modern film, a therianthropic hybrid wolf-like creature), either purposely ...

. The light of the Moon was thought to worsen the symptoms of

lunatics Lunatic is an antiquated term referring to a person who is seen as mentally ill, dangerous, foolish, or crazy—conditions once attributed to "lunacy". The word derives from ''lunaticus'' meaning "of the moon" or "moonstruck". History The te ...

, and to sleep in moonlight could make one blind, or mad.''A Dictionary of English Folklore'', Oxford University Press, 2000

Nyctalopia Nyctalopia (; ), also called night-blindness, is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases. Night blindness may exist from birth, or be caused by injury or malnutrition ( ...

(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 Moonmilk (sometimes called mondmilch, also known as montmilch or as cave milk) is a white, creamy substance found inside limestone, dolomite, and possibly other types of caves. It is a precipitate from limestone comprising aggregates of fine cry ...

, a soft white limestone precipitate found in caves, was thought to be caused by the rays of the Moon.

Moonlight in art

File:Joseph Vernet - Night - Seaport by Moonlight - WGA24731.jpg, ''Seaport by Moonlight'' (1771) by

Claude Joseph Vernet Claude-Joseph Vernet (14 August 17143 December 1789) was a French painter. His son, Antoine Charles Horace Vernet, was also a painter. Life and work Vernet was born in Avignon. When only fourteen years of age he aided his father, Antoine 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, ''A Philosopher in 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 Édouard Manet (, ; ; 23 January 1832 – 30 April 1883) was a French modernist painter. He was one of the first 19th-century artists to paint modern life, as well as a pivotal figure in the transition from Realism to Impressionism. Bo ...

File:Van Gogh - Starry Night - Google Art Project.jpg, ''

The Starry Night ''The Starry Night'' ( nl, De sterrennacht) is an oil-on-canvas painting by the Dutch Post-Impressionist painter Vincent van Gogh. Painted in June 1889, it depicts the view from the east-facing window of his asylum room at Saint-Rémy-de-Prove ...

'' (1889) by

Vincent van Gogh Vincent Willem van Gogh (; 30 March 185329 July 1890) was a Dutch Post-Impressionist painter who posthumously became one of the most famous and influential figures in Western art history. In a decade, he created about 2,100 artworks, inc ...

File:Stanisław_Witkiewicz_-_Wiatr_halny_1895.jpg, ''Halny'' (1895) by Stanisław Witkiewicz

Contemporary art

In 2008

Katie Paterson Katie Paterson (born 1981) is a Fife-based visual artist from Glasgow, Scotland, having previously lived and worked in Berlin whose artworks concern translation, distance, and scale. Paterson holds a BA from Edinburgh College of Art (2004) and a ...

produced an artwork titled ''Light bulb to Simulate Moonlight''. It consists of 289 lightbulbs coated to produce a similar spectrum to the light of the full Moon.

References

External links

Phases of the Moon
at

USNO United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the Depo ...

Strange Moonlight
a
Science@NASA

a

{{Parts of a day Lunar observation Light Light sources

Light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...