A waning moon The term dark moon describes the last 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 a waning

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 ...

. The duration of a dark moon varies between 1.5 and 3.5 days, depending on its

ecliptic latitude In astronomy, the ecliptic coordinate system is a celestial coordinate system commonly used for representing the apparent positions, orbits, and pole orientations of Solar System objects. Because most planets (except Mercury) and many small So ...

. In current

astronomical 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 include ...

usage, the

new moon In astronomy, 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. ...

occurs in the middle of this dark period, when the Moon and

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

are in conjunction. This definition has entered popular usage, so that calendars will typically indicate the date of the "new moon" rather than the "dark moon".

Dark moon as the 30th division

The ''

Oxford English Dictionary The ''Oxford English Dictionary'' (''OED'') is the principal historical dictionary of the English language, published by Oxford University Press (OUP), a University of Oxford publishing house. The dictionary, which published its first editio ...

'' defines the

as "the first visible crescent of the Moon, after conjunction with the Sun". ''Dark moon'' is a term used for a waning crescent moon. When the

Moon's orbit The Moon orbits Earth in the prograde direction and completes one revolution relative to the Vernal Equinox and the fixed stars in about 27.3 days (a tropical month and sidereal month), and one revolution relative to the Sun in about 29.5 days ...

is divided into 30 segments, as the

ancient Greeks Ancient Greece () was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity (), that comprised a loose collection of culturally and linguistically re ...

did in the time of Homer, the

Babylonia Babylonia (; , ) was an Ancient history, ancient Akkadian language, Akkadian-speaking state and cultural area based in the city of Babylon in central-southern Mesopotamia (present-day Iraq and parts of Kuwait, Syria and Iran). It emerged as a ...

ns did, and the Indians still do today (calling them ''

tithi In Vedic timekeeping, a ''tithi'' is a "duration of two faces of moon that is observed from earth", known as ''milа̄lyа̄'' () in Nepal Bhasa, or the time it takes for the longitudinal angle between the Moon and the Sun to increase by 12 ...

''), the last phase is called the "dark moon". In Greek, it was called the "old moon" and associated with

Hecate Hecate ( ; ) is a goddess in ancient Greek religion and mythology, most often shown holding a pair of torches, a key, or snakes, or accompanied by dogs, and in later periods depicted as three-formed or triple-bodied. She is variously associat ...

. In India, it is called

Amavasya Amāvásyā () is the lunar phase of the new moon in Sanskrit. Indian calendars use 30 lunar phases, called tithi in India. The dark moon tithi is when the Moon is within 12 degrees of the angular distance between the Sun and Moon before conj ...

and associated with

Kali Kali (; , ), also called Kalika, is a major goddess in Hinduism, primarily associated with time, death and destruction. Kali is also connected with transcendental knowledge and is the first of the ten Mahavidyas, a group of goddesses who p ...

.Cole, Freedom. Amāvāsya and Pratipad. ''Jyotish Digest'', Vol XI, Issue II, April–Sep 2014 Both of these goddesses have a dark connotation, hence the term dark moon. In Babylonian, Greek, and Indian culture, the dark moon occurs within the 12° of

angular distance Angular distance or angular separation is the measure of the angle between the orientation (geometry), orientation of two straight lines, ray (geometry), rays, or vector (geometry), vectors in three-dimensional space, or the central angle subtende ...

between the Moon and the Sun before conjunction (a type of syzygy). The new moon occurs within the 12° after syzygy. This 12° arc is called ''uma'' by the Babylonians and ''tithi'' by the Indians. The Moon takes a mean duration of 23 hours and 37 minutes to cover this length, but this period can vary from 21 to 26 hours because of the Moon's orbital anomaly. This means that the "dark moon" actually lasts approximately 23 hours and 37 minutes and includes any time marked as "new moon" on a

lunar calendar A lunar calendar is a calendar based on the monthly cycles of the Moon's phases ( synodic months, lunations), in contrast to solar calendars, whose annual cycles are based on the solar year, and lunisolar calendars, whose lunar months are br ...

, and not 1.5 to 3.5 days as stated earlier.

References

{{DEFAULTSORT:Dark Moon category:new moon category:phases of the Moon

Dark moon as the 30th division

See also

References