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51-458: Many cultures have implicitly linked the 29.5-day lunar cycle to women's menstrual cycles , as evident in the shared linguistic roots of "menstruation" and "moon" words in multiple language families . This identification was not universal, as demonstrated by the fact that not all moon deities are female. Still, many well-known mythologies feature moon goddesses, including the Greek goddess Selene ,

102-578: A clock for addressing this as an international scientific project. In Pakistan , there is a "Central Ruet-e-Hilal Committee" whose head is Mufti Muneeb-ur-Rehman, assisted by 150 observatories of the Pakistan Meteorological Department , which announces the sighting of the new moon. An attempt to unify Muslims on a scientifically calculated worldwide calendar was adopted by both the Fiqh Council of North America and

153-554: A lunar calendar. Calendars such as the Runic calendar fixing the beginning of the year at the first full moon after winter solstice . The Moon features prominently in art and literature , often with a purported influence on human affairs. Lunar cycle A lunar phase or Moon phase is the apparent shape of the Moon 's directly sunlit portion as viewed from the Earth . Because

204-594: A number given to each lunation beginning from a specific one in history. Several conventions are in use. The most commonly used was the Brown Lunation Number (BLN), which defines "lunation 1" as beginning at the first new moon of 1923, the year when Ernest William Brown's lunar theory was introduced in the American Ephemeris and Nautical Almanac . Lunation 1 occurred at approximately 02:41 UTC , 17 January 1923. With later refinements,

255-488: A total of 30 phases (one per day). As seen from Earth, the Moon's eccentric orbit makes it both slightly change its apparent size, and to be seen from slightly different angles. The effect is subtle to the naked eye, from night to night, yet somewhat obvious in time-lapse photography. Lunar libration causes part of the back side of the Moon to be visible to a terrestrial observer some of the time. Because of this, around 59% of

306-796: A vegetarian diet on the new moon and full moon each month. The new moon is significant in the lunar Hindu calendar . The first day of the calendar starts the day after the dark moon phase ( Amavasya ). There are fifteen moon dates for each of the waxing and waning periods. These fifteen dates are divided evenly into five categories: Nanda, Bhadra', Jaya, Rikta, and Purna, which are cycled through in that order. Nanda dates are considered to be favorable for auspicious works; Bhadra dates for works related to community, social, family, and friends; and Jaya dates for dealing with conflict. Rikta dates are considered beneficial only for works related to cruelty. Purna dates are considered to be favorable for all work. The lunar Hijri calendar has exactly 12 lunar months in

357-487: A year of 354 or 355 days. It has retained an observational definition of the new moon, marking the new month when the first crescent moon is seen, and making it impossible to be certain in advance of when a specific month will begin (in particular, the exact date on which the month of Ramadan will begin is not known in advance). In Saudi Arabia , the new King Abdullah Centre for Crescent Observations and Astronomy in Mecca has

408-545: A year, but only passes between the Earth and Sun 12.4 times. It might be expected that once every month, when the Moon passes between Earth and the Sun during a new moon, its shadow would fall on Earth causing a solar eclipse , but this does not happen every month. Nor is it true that during every full moon, the Earth's shadow falls on the Moon, causing a lunar eclipse . Solar and lunar eclipses are not observed every month because

459-409: Is a small fraction of a month . It does not have any obvious effect on the appearance of the Moon. It does however affect accurate calculations of the times of lunar phases. It can be confusing that the Moon's orbital sidereal period is 27.3 days while the phases complete a cycle once every 29.5 days (synodic period). This is due to the Earth's orbit around the Sun. The Moon orbits the Earth 13.4 times

510-400: Is about 2 degrees different from the line of sight of an observer who sees the Moon on the western horizon . The Moon moves about 12 degrees around its orbit per day, so, if these observers were stationary, they would see the phases of the Moon at times that differ by about one-sixth of a day, or 4 hours. But in reality, the observers are on the surface of the rotating Earth, so someone who sees

561-600: Is dark, the Moon is becoming darker; if the right side is lit, the Moon is getting brighter.) In the Southern Hemisphere , the Moon is observed from a perspective inverted, or rotated 180°, to that of the Northern and to all of the images in this article, so that the opposite sides appear to wax or wane. Closer to the Equator , the lunar terminator will appear horizontal during the morning and evening. Since

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612-479: Is dark, then the bright part is thickening, and the Moon is described as waxing (shifting toward full moon). If the right side of the Moon is dark, then the bright part is thinning, and the Moon is described as waning (past full and shifting toward new moon). Assuming that the viewer is in the Northern Hemisphere, the right side of the Moon is the part that is always waxing. (That is, if the right side

663-429: Is the first recorded to have used the former method; Chinese calendar uses the latter, despite delaying its start until the second or even third new moon after the solstice. The Hindu calendar , also a lunisolar calendar, further divides the month into two fourteen day periods that mark the waxing moon and the waning moon. The ancient Roman calendar was broadly a lunisolar one; on the decree of Julius Caesar in

714-450: Is the period from one new moon to the next. At the J2000.0 epoch, the average length of a lunation is 29.53059 days (or 29 days, 12 hours, 44 minutes, and 3 seconds). However, the length of any one synodic month can vary from 29.26 to 29.80 days (12.96 hours) due to the perturbing effects of the Sun's gravity on the Moon's eccentric orbit . The Lunation Number or Lunation Cycle is

765-556: The Aztec religion . Many cultures are oriented chronologically by the Moon, as opposed to the Sun. The Hindu calendar maintains the integrity of the lunar month and the moon god Chandra has religious significance during many Hindu festivals (e.g. Karwa Chauth , Sankashti Chaturthi , and during eclipses). Ancient Germanic tribes and the peoples they were in contact with, such as the Baltic Finnic peoples , were also known to have

816-650: The Baháʼí Faith , effective from 2015 onwards, the " Twin Holy Birthdays ", refer to two successive holy days in the Baháʼí calendar (the birth of the Báb and the birth of Bahá'u'lláh ), will be observed on the first and the second day following the occurrence of the eighth new moon after Naw-Rúz (Baháʼí New Year), as determined in advance by astronomical tables using Tehran as the point of reference. This will result in

867-506: The European Council for Fatwa and Research in 2007. The new calculation requires that conjunction must occur before sunset in Mecca, Saudi Arabia, and that, on the same evening, the moonset must take place after sunset. These can be precisely calculated and therefore a unified calendar is possible should it become adopted worldwide. The Baháʼí calendar is a solar calendar with certain new moons observed as moveable feasts . In

918-678: The Germanic tribes , Tsukuyomi of the Japanese, Igaluk / Alignak of the Inuit , and the Hindu god Chandra . The original Proto-Indo-European lunar deity, *Meh₁not appears to have been male, with many possible derivatives including the Homeric figure of Menelaus . Cultures with male moon gods often feature sun goddesses . An exception is Hinduism , featuring both male and female aspects of

969-559: The Hebrew calendar . In the Chinese calendar , the beginning of the month is marked by the last visible crescent of a waning Moon. The astronomical new moon occurs by definition at the moment of conjunction in ecliptical longitude with the Sun when the Moon is invisible from the Earth. This moment is unique and does not depend on location, and in certain circumstances, it coincides with a solar eclipse . A lunation , or synodic month ,

1020-452: The Julian day number of one from that of the other, or there are simpler formulae giving (for instance) the number of days since 31 December 1899. However, this calculation assumes a perfectly circular orbit and makes no allowance for the time of day at which the new moon occurred and therefore may be incorrect by several hours. (It also becomes less accurate the larger the difference between

1071-399: The new moon is the first lunar phase , when the Moon and Sun have the same ecliptic longitude . At this phase, the lunar disk is not visible to the naked eye , except when it is silhouetted against the Sun during a solar eclipse . The original meaning of the term 'new moon', which is still sometimes used in calendrical , non-astronomical contexts, is the first visible crescent of

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1122-459: The new moon , first quarter, full moon , and last quarter (also known as third or final quarter), when the Moon's ecliptic longitude is at an angle to the Sun (as viewed from the center of the Earth) of 0°, 90°, 180°, and 270° respectively. Each of these phases appears at slightly different times at different locations on Earth, and tabulated times are therefore always geocentric (calculated for

1173-592: The BLN was used in almanacs until 1983. A more recent lunation number (called the Lunation Number) was introduced by Jean Meeus in 1998. defines lunation 0 as beginning on the first new moon of 2000 (this occurred at approximately 18:14 UTC , 6 January 2000). The formula relating Meeus's Lunation Number with the Brown Lunation Number is BLN = LN + 953. The Goldstine Lunation Number refers to

1224-406: The Earth's center). Between the principal phases are intermediate phases, during which the apparent shape of the illuminated Moon is either crescent or gibbous . On average, the intermediate phases last one-quarter of a synodic month , or 7.38 days. The term waxing is used for an intermediate phase when the Moon's apparent shape is thickening, from new to a full moon; and waning when

1275-497: The Islamic Hijri calendar ) rely completely on this metric. The fact, however, that a year of twelve lunar months is ten or eleven days shorter than the solar year means that a lunar calendar drifts out of step with the seasons. Lunisolar calendars resolve this issue with a year of thirteen lunar months every few years, or by restarting the count at the first new (or full) moon after the winter solstice . The Sumerian calendar

1326-488: The Moon after conjunction with the Sun. This thin waxing crescent is briefly and faintly visible as the Moon gets lower in the western sky after sunset . The precise time and even the date of the appearance of the new moon by this definition will be influenced by the geographical location of the observer. The first crescent marks the beginning of the month in the Islamic calendar and in some lunisolar calendars such as

1377-466: The Moon in the sky, the crescent opens downward; when the Moon is above the Sun, the crescent opens upward . The crescent Moon is most clearly and brightly visible when the Sun is below the horizon, which implies that the Moon must be above the Sun, and the crescent must open upward. This is therefore the orientation in which the crescent Moon is most often seen from the tropics. The waxing and waning crescents look very similar. The waxing crescent appears in

1428-413: The Moon is tidally locked with the Earth, the same hemisphere is always facing 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

1479-414: The Moon on the eastern horizon at one moment sees it on the western horizon about 12 hours later. This adds an oscillation to the apparent progression of the lunar phases. They appear to occur more slowly when the Moon is high in the sky than when it is below the horizon. The Moon appears to move jerkily, and the phases do the same. The amplitude of this oscillation is never more than about four hours, which

1530-518: The Moon's orbit, this duration is not perfectly constant but averages about 29.5 days. The appearance of the Moon (its phase) gradually changes over a lunar month as the relative orbital positions of the Moon around Earth, and Earth around the Sun, shift. The visible side of the Moon is sunlit to varying extents, depending on the position of the Moon in its orbit, with the sunlit portion varying from 0% (at new moon) to nearly 100% (at full moon). There are four principal (primary, or major) lunar phases:

1581-469: The Moon's surface has been imaged from the ground. When the Sun and Moon are aligned on the same side of the Earth (conjunct), the Moon is "new", and the side of the Moon facing Earth is not illuminated by the Sun. As the Moon waxes (the amount of illuminated surface as seen from Earth increases), the lunar phases progress through the new moon, crescent moon, first-quarter moon, gibbous moon, and full moon phases. The Moon then wanes as it passes through

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1632-660: The Roman goddess Luna , and the Chinese goddess Chang'e . Several goddesses including Artemis , Hecate , and Isis did not originally have lunar aspects, and only acquired them late in antiquity due to syncretism with the de facto Greco-Roman lunar deity Selene / Luna . Male lunar gods are also common, such as Sin of the Mesopotamians , Khonsu of the Egyptians (or the earlier Egyptian lunar deity Iah ), Mani of

1683-404: The above descriptions of the lunar phases only apply at middle or high latitudes , observers moving towards the tropics from northern or southern latitudes will see the Moon rotated anti-clockwise or clockwise with respect to the images in this article. The lunar crescent can open upward or downward, with the "horns" of the crescent pointing up or down, respectively. When the Sun appears above

1734-508: The annual seasons by setting the new moon of Aviv , the barley ripening , or spring , as the first moon and head of the year. Since the Babylonian captivity , this month is called Nisan , and it is calculated based on mathematical rules designed to ensure that festivals are observed in their traditional season. Passover always falls in the springtime. This fixed lunisolar calendar follows rules introduced by Hillel II and refined until

1785-571: The first century BCE, Rome changed to a solar calendar of twelve months, each of a fixed number of days except in a leap year . This, the Julian calendar (slightly revised in 1582 to correct the leap year rule), is the basis for the Gregorian calendar that is almost exclusively the civil calendar in use worldwide today. Each of the four intermediate phases lasts approximately seven days (7.38 days on average), but varies ±11.25% due to lunar apogee and perigee . The number of days counted from

1836-563: The first day of the month of Muharram , which occurred in 622  CE (15 July, Julian, in the proleptic reckoning). It can be calculated using ILN = LN + 17038. The Thai Lunation Number is called "มาสเกณฑ์" (Maasa-Kendha), defines lunation 0 as the beginning of Burmese era of the Buddhist calendar on Sunday, 22 March 638 CE. It can be calculated using TLN = LN + 16843. The new moon, in Hebrew Rosh Chodesh , signifies

1887-425: The gibbous moon, third-quarter moon, and crescent moon phases, before returning back to new moon. The terms old moon and new moon are not interchangeable. The "old moon" is a waning sliver (which eventually becomes undetectable to the naked eye) until the moment it aligns with the Sun and begins to wax, at which point it becomes new again. Half moon is often used to mean the first- and third-quarter moons, while

1938-474: The half-circle, then the shape will be gibbous (bulging outwards), whereas if the half-ellipse is concave with respect to the half-circle, then the shape will be a crescent . When a crescent moon occurs, the phenomenon of earthshine may be apparent, where the night side of the Moon dimly reflects indirect sunlight reflected from Earth. In the Northern Hemisphere , if the left side of the Moon

1989-460: The intersection of Earth's orbital plane about the Sun and the Moon's orbital plane about the Earth (that is, at one of its nodes ). This happens about twice per year, and so there are between four and seven eclipses in a calendar year. Most of these eclipses are partial; total eclipses of the Moon or Sun are less frequent. The phases are not caused by the Earth's shadow falling on the moon, as some people believe. New moon In astronomy ,

2040-502: The lunation numbering used by Herman Goldstine , with lunation 0 beginning on 11 January 1001 BCE, and can be calculated using GLN = LN + 37105. The Hebrew Lunation Number is the count of lunations in the Hebrew calendar with lunation 1 beginning on 6 October 3761 BCE. It can be calculated using HLN = LN + 71234. The Islamic Lunation Number is the count of lunations in the Islamic Calendar with lunation 1 as beginning on

2091-483: The new moon's arms" or "the new moon in the old moon's arms". Archaeologists have reconstructed methods of timekeeping that go back to prehistoric times, at least as old as the Neolithic . The natural units for timekeeping used by most historical societies are the day , the solar year and the lunation . The first crescent of the new moon provides a clear and regular marker in time and pure lunar calendars (such as

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2142-449: The ninth century. This calculation makes use of a mean lunation length used by Ptolemy and handed down from Babylonians , which is still very accurate: ca. 29.530594 days vs. a present value (see below ) of 29.530589 days. This difference of only 0.000005, or five millionths of a day, adds up to about only four hours since Babylonian times. The new moon is the beginning of the month in the Chinese calendar . Some Buddhist Chinese keep

2193-594: The observance of the Twin Birthdays moving, year to year, from mid-October to mid-November according to the Gregorian calendar. Easter , the most important feast in the Christian liturgical calendar , is a movable feast . The date of Easter is determined by reference to the ecclesiastical full moon , which, being historically difficult to determine with precision, is defined as being fourteen days after

2244-413: The plane of the Moon's orbit around the Earth is tilted by about 5° with respect to the plane of Earth's orbit around the Sun (the plane of the ecliptic ). Thus, when new and full moons occur, the Moon usually lies to the north or south of a direct line through the Earth and Sun. Although an eclipse can only occur when the Moon is either new (solar) or full (lunar), it must also be positioned very near

2295-426: The required date and the reference date.) It is accurate enough to use in a novelty clock application showing lunar phase, but specialist usage taking account of lunar apogee and perigee requires a more elaborate calculation. The Earth subtends an angle of about two degrees when seen from the Moon. This means that an observer on Earth who sees the Moon when it is close to the eastern horizon sees it from an angle that

2346-418: The shape is thinning. The duration from full moon to new moon (or new moon to full moon) varies from approximately 13 days 22 + 1 ⁄ 2 hours to about 15 days 14 + 1 ⁄ 2 hours . Due to lunar motion relative to the meridian and the ecliptic , in Earth's northern hemisphere : Non-Western cultures may use a different number of lunar phases; for example, traditional Hawaiian culture has

2397-403: The solar divine. The ancient Egyptians had several moon gods including Khonsu and Thoth , although Thoth is a considerably more complex deity. Set represented the moon in the ancient Egyptian calendar . In Bakongo religion , the earth and moon goddess Nzambici is the female counterpart of the sun god Nzambi Mpungu . Metztli , Coyolxauhqui and Tēcciztēcatl are all lunar deities in

2448-508: The start of every Hebrew month and is considered an important date and minor holiday in the Hebrew calendar . The modern form of the calendar practiced in Judaism is a rule-based lunisolar calendar , akin to the Chinese calendar , measuring months defined in lunar cycles as well as years measured in solar cycles, and distinct from the purely lunar Islamic calendar and the predominantly solar Gregorian calendar . The Jewish months are fixed to

2499-423: The term quarter refers to the extent of the Moon's cycle around the Earth, not its shape. When an illuminated hemisphere is viewed from a certain angle, the portion of the illuminated area that is visible will have a two-dimensional shape as defined by the intersection of an ellipse and circle (in which the ellipse's major axis coincides with the circle's diameter). If the half-ellipse is convex with respect to

2550-452: The time of the new moon is the Moon's "age". Each complete cycle of phases is called a " lunation ". The approximate age of the Moon, and hence the approximate phase, can be calculated for any date by calculating the number of days since a known new moon (such as 1 January 1900 or 11 August 1999) and reducing this modulo 29.53059 days (the mean length of a synodic month ). The difference between two dates can be calculated by subtracting

2601-506: The western sky in the evening, and the waning crescent in the eastern sky in the morning. When the Moon (seen from Earth) is a thin crescent , Earth (as viewed from the Moon) is almost fully lit by the Sun. Often, the dark side of the Moon is dimly illuminated by indirect sunlight reflected from Earth, but is bright enough to be easily visible from Earth. This phenomenon is called earthshine , sometimes picturesquely described as "the old moon in

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