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In
astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
, the new moon is the first
lunar phase A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth. Because the Moon is tidally locked with the Earth, the same hemisphere is always facing the Earth. In common usage, the four maj ...
, when the
Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the
naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...
, except when it is silhouetted against the Sun during a
solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season i ...
. The original meaning of the term 'new moon', which is still sometimes used in calendrical, non-astronomical contexts, is the first visible
crescent A crescent shape (, ) is a symbol or emblem used to represent the lunar phase (as it appears in the northern hemisphere) in the first quarter (the "sickle moon"), or by extension a symbol representing the Moon itself. In Hindu iconography, Hind ...
of 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 Sunset (or sundown) is the disappearance of the Sun at the end of the Sun path, below the horizon of the Earth (or any other astronomical object in the Solar System) due to its Earth's rotation, rotation. As viewed from everywhere on Earth, it ...
. 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 The Hijri calendar (), also known in English as the Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the Ramad ...
and in some lunisolar calendars such as the
Hebrew calendar The Hebrew calendar (), also called the Jewish calendar, is a lunisolar calendar used today for Jewish religious observance and as an official calendar of Israel. It determines the dates of Jewish holidays and other rituals, such as '' yahrze ...
. In the
Chinese calendar The traditional Chinese calendar, dating back to the Han dynasty, is a lunisolar calendar that blends solar, lunar, and other cycles for social and agricultural purposes. While modern China primarily uses the Gregorian calendar for officia ...
, 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 solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season i ...
. A lunation, or
synodic month In lunar calendars, a lunar month is the time between two successive Syzygy (astronomy), syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month. Variations In Shona people, S ...
, is the period from one new moon to the next. At the
J2000.0 In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to pe ...
epoch, the average length of a lunation is 29.53059
day A day is the time rotation period, period of a full Earth's rotation, rotation of the Earth with respect to the Sun. On average, this is 24 hours (86,400 seconds). As a day passes at a given location it experiences morning, afternoon, evening, ...
s (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 In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless quantity, dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circu ...
.


Lunation number

The ''Lunation Number'' or ''Lunation Cycle'' is 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, the BLN was used in almanacs until 1983. A more recent lunation number called the Lunation Number (LN) was introduced by Jean Meeus in 1998, and 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 to the Brown Lunation Number is BLN = LN + 953. The Goldstine Lunation Number (GLN) refers to 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 (HLN) is the count of lunations in the
Hebrew calendar The Hebrew calendar (), also called the Jewish calendar, is a lunisolar calendar used today for Jewish religious observance and as an official calendar of Israel. It determines the dates of Jewish holidays and other rituals, such as '' yahrze ...
with lunation 1 beginning on 6 October 3761 BCE. It can be calculated using HLN = LN + 71234. The Islamic Lunation Number (ILN) is the count of lunations in the
Islamic Calendar The Hijri calendar (), also known in English as the Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the Ramad ...
with lunation 1 as beginning on the first day of the month of
Muharram Al-Muharram () is the first month of the Islamic calendar. It is one of the four sacred months of the year when warfare is banned. It precedes the month of Safar. The tenth of Muharram is known as Ashura, an important day of commemoration in ...
, which occurred in 622  CE (15 July, Julian, in the proleptic reckoning). It can be calculated using ILN = LN + 17038. The Thai Lunation Number (TLN) 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.


Lunisolar calendars


Hebrew calendar

The new moon, in Hebrew Rosh Chodesh, signifies the start of every Hebrew month and is considered an important date and minor holiday in the
Hebrew calendar The Hebrew calendar (), also called the Jewish calendar, is a lunisolar calendar used today for Jewish religious observance and as an official calendar of Israel. It determines the dates of Jewish holidays and other rituals, such as '' yahrze ...
. The modern form of the calendar practiced in Judaism is a rule-based lunisolar calendar, akin to the
Chinese calendar The traditional Chinese calendar, dating back to the Han dynasty, is a lunisolar calendar that blends solar, lunar, and other cycles for social and agricultural purposes. While modern China primarily uses the Gregorian calendar for officia ...
, measuring months defined in lunar cycles as well as years measured in solar cycles, and distinct from the purely lunar
Islamic calendar The Hijri calendar (), also known in English as the Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the Ramad ...
and the predominantly solar
Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian cale ...
. The Jewish months are fixed to 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 The Babylonian captivity or Babylonian exile was the period in Jewish history during which a large number of Judeans from the ancient Kingdom of Judah were forcibly relocated to Babylonia by the Neo-Babylonian Empire. The deportations occurred ...
, this month is called
Nisan Nisan (or Nissan; from ) in the Babylonian and Hebrew calendars is the month of the barley ripening and first month of spring. The name of the month is an Akkadian language borrowing, although it ultimately originates in Sumerian ''nisag' ...
, 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 the ninth century. This calculation makes use of a mean lunation length used by
Ptolemy Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzant ...
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.


Chinese calendar

The new moon is the beginning of the month in the
Chinese calendar The traditional Chinese calendar, dating back to the Han dynasty, is a lunisolar calendar that blends solar, lunar, and other cycles for social and agricultural purposes. While modern China primarily uses the Gregorian calendar for officia ...
. Some Buddhist Chinese keep a vegetarian diet on the new moon and full moon each month.


Hindu calendar

The new moon is significant in the lunar
Hindu calendar The Hindu calendar, also called Panchangam, Panchanga (), is one of various lunisolar calendars that are traditionally used in the Indian subcontinent and Southeast Asia, with further regional variations for social and Hindu religious purposes ...
. 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.


Babylonian calendar The Babylonian calendar was a lunisolar calendar used in Mesopotamia from around the 2nd millennium BC until the Seleucid Era ( 294 BC), and it was specifically used in Babylon from the Old Babylonian Period ( 1780s BC) until the Seleucid Era. ...


Lunar calendars


Islamic calendar

The
lunar Hijri calendar The Hijri calendar (), also known in English as the Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the an ...
has exactly 12 lunar months in 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 Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in West Asia. Located in the centre of the Middle East, it covers the bulk of the Arabian Peninsula and has a land area of about , making it the List of Asian countries ...
, the new King Abdullah Centre for Crescent Observations and Astronomy in Mecca has a clock for addressing this as an international scientific project. In
Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...
, 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 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.


Solar calendars holding moveable feasts


Baháʼí calendar

The Baháʼí calendar is a solar calendar with certain new moons observed as moveable feasts. In the
Baháʼí Faith The Baháʼí Faith is a religion founded in the 19th century that teaches the Baháʼí Faith and the unity of religion, essential worth of all religions and Baháʼí Faith and the unity of humanity, the unity of all people. Established by ...
, 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 Tehran (; , ''Tehrân'') is the capital and largest city of Iran. It is the capital of Tehran province, and the administrative center for Tehran County and its Central District (Tehran County), Central District. With a population of around 9. ...
as the point of reference.Momen, Moojan (2014)
The Badí` (Baháʼí) Calendar: An Introduction
.
This will result in the observance of the Twin Birthdays moving, year to year, from mid-October to mid-November according to the Gregorian calendar.


Christian liturgical calendar

Easter Easter, also called Pascha ( Aramaic: פַּסְחָא , ''paskha''; Greek: πάσχα, ''páskha'') or Resurrection Sunday, is a Christian festival and cultural holiday commemorating the resurrection of Jesus from the dead, described in t ...
, the most important feast in the Christian
liturgical calendar The liturgical year, also called the church year, Christian year, ecclesiastical calendar, or kalendar, consists of the cycle of liturgical days and seasons that determines when feast days, including celebrations of saints, are to be obs ...
, 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 the (first crescent) new moon.


See also

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Notes


References


Works cited

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External links


Moon Watch site
() of the Nautical Almanac Office {{DEFAULTSORT:New Moon Phases of the Moon