Moonlight consists of mostly sunlight (with little earthlight) reflected from the parts of the Moon's surface where the Sun's light strikes. [1]
Moonlight consists of mostly sunlight (with little earthlight) reflected from the parts of the Moon's surface where the Sun's light strikes. [1]
The ancient Greek philosopher Anaxagoras was aware that "the sun provides the moon with its brightness". [2]
The intensity of moonlight varies greatly depending on the lunar phase, but even the full moon typically provides only about 0.05–0.1 lux illumination. [3] When a full Moon around perigee (a "supermoon") is viewed around upper culmination from the tropics, the illuminance can reach up to 0.32 lux. [3] From Earth, the apparent magnitude of the full Moon is only about 1⁄380,000 that of the Sun.[ citation needed ]
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, [4] meaning only 13.6% 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, moonlight generally increases the brightness of the night sky, reducing contrast between dimmer stars and the background. For this reason, many astronomers usually avoid observing sessions around a full moon.
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. [5] 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. [6]
Selenoplexia was a supposed medical condition caused by the rays of the moon. [7]
In 2008 Katie Paterson produced an artwork titled Light bulb to Simulate Moonlight. [8] It consists of 289 lightbulbs coated to produce a similar spectrum to the light of the full Moon. [8]
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. This means that the lunar hemisphere facing Earth—the near side—is completely sunlit and appears as an approximately circular disk. The full moon occurs roughly once a month.
Gegenschein or counterglow is a faintly bright spot in the night sky centered at the antisolar point. The backscatter of sunlight by interplanetary dust causes this optical phenomenon, being a zodiacal light and part of its zodiacal light band.
A lunar eclipse is an astronomical event that occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. Such an alignment occurs during an eclipse season, approximately every six months, during the full moon phase, when the Moon's orbital plane is closest to the plane of the Earth's orbit.
The Moon is Earth's only natural satellite. It orbits at an average distance of 384,400 km (238,900 mi), about 30 times the diameter of Earth. Tidal forces between Earth and the Moon have synchronized the Moon's orbital period with its rotation period at 29.5 Earth days, causing the same side of the Moon to always face Earth. The Moon's gravitational pull—and, to a lesser extent, the Sun's—are the main drivers of Earth's tides.
A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth. In common usage, the four major phases are the new moon, the first quarter, the full moon and the last quarter; the four minor phases are waxing crescent, waxing gibbous, waning gibbous, and waning crescent. A lunar month is the time between successive recurrences of the same phase: due to the eccentricity of the Moon's orbit, this duration is not perfectly constant but averages about 29.5 days.
A terminator or twilight zone is a moving line that divides the daylit side and the dark night side of a planetary body. The terminator is defined as the locus of points on a planet or moon where the line through the center of its parent star is tangent. An observer on the terminator of such an orbiting body with an atmosphere would experience twilight due to light scattering by particles in the gaseous layer.
Planetshine is the dim illumination, by sunlight reflected from a planet, of all or part of the otherwise dark side of any moon orbiting the body. Planetlight is the diffuse reflection of sunlight from a planet, whose albedo can be measured.
In astronomy, an extraterrestrial sky is a view of outer space from the surface of an astronomical body other than Earth.
In planetary geology, a ray system comprises radial streaks of fine ejecta thrown out during the formation of an impact crater, looking somewhat like many thin spokes coming from the hub of a wheel. The rays may extend for lengths up to several times the diameter of their originating crater, and are often accompanied by small secondary craters formed by larger chunks of ejecta. Ray systems have been identified on the Moon, Earth, Mercury, and some moons of the outer planets. Originally it was thought that they existed only on planets or moons lacking an atmosphere, but more recently they have been identified on Mars in infrared images taken from orbit by 2001 Mars Odyssey's thermal imager.
The night sky is the nighttime appearance of 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.
A nightlight is a small light fixture, usually electrical, placed for comfort or convenience in dark areas or areas that may become dark at certain times, such as at night or during an emergency. Small long-burning candles serving a similar function are referred to as "tealights".
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. It can be described as insufficient adaptation to darkness.
The lunar effect is a purported correlation between specific stages of the roughly 29.5-day lunar cycle and behavior and physiological changes in living beings on Earth, including humans. A considerable number of studies have examined the effect on humans. By the late 1980s, there were at least 40 published studies on the purported lunar-lunacy connection, and at least 20 published studies on the purported lunar-birthrate connection. Literature reviews and metanalyses have found no correlation between the lunar cycle and human biology or behavior. In cases such as the approximately monthly cycle of menstruation in humans, the coincidence in timing reflects no known lunar influence. The widespread and persistent beliefs about the influence of the Moon may depend on illusory correlation – the perception of an association that does not in fact exist.
Night photography is the capturing of images outdoors between dusk and dawn. Night photographers generally have a choice between using artificial lighting and using a long exposure, exposing the shot for seconds, minutes, or hours in order to capture enough light to record an image. With the progress of high-speed films, higher-sensitivity digital sensors, wide-aperture lenses, and the ever-greater power of urban lights, night photography is increasingly possible using available light.
The Moon is the largest natural satellite of and the closest major astronomical object to Earth. The Moon may be observed by using a variety of optical instruments, ranging from the naked eye to large telescopes. The Moon is the only celestial body upon which surface features can be discerned with the unaided eyes of most people.
In photography and cinematography, available light refers to any source of light that is not explicitly supplied by the photographer for the purpose of taking pictures. The term usually refers to light sources in the surrounding environment that are present naturally or artificial lighting that is already pre-existing. It generally excludes flashes, although arguably flash lighting provided by other photographers shooting simultaneously in the same space could be considered available light. Light sources that affect the scene and are included in the actual frame are called practical light sources, or simply practicals.
Earthlight is the diffuse reflection of sunlight reflected from Earth's surface and clouds. Earthshine, also known as the Moon's ashen glow, is the dim illumination of the otherwise unilluminated portion of the Moon by this indirect sunlight. Earthlight on the Moon during the waxing crescent is called "the old Moon in the new Moon's arms", while that during the waning crescent is called "the new Moon in the old Moon's arms".
Earth's shadow is the shadow that Earth itself casts through its atmosphere and into outer space, toward the antisolar point. During the twilight period, the shadow's visible fringe – sometimes called the dark segment or twilight wedge – appears as a dark and diffuse band just above the horizon, most distinct when the sky is clear.
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 orbit—resulting in a slightly larger-than-usual apparent size of the lunar disk as viewed from Earth. The technical name is a perigee syzygy or a fullMoon around perigee. Because the term supermoon is astrological in origin, it has no precise astronomical definition.
In lunar photography, the Looney 11 rule is a method of estimating correct exposures without a light meter. For daylight photography, there is a similar rule called the Sunny 16 rule. The basic rule is: "For astronomical photos of the Moon's surface, set aperture to f/11 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting]."
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| Surface and features | ||
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| Exploration | ||
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| Phases and names | ||
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