A dark moon describes the Moon during the period it is invisible against the backdrop of the Sun in the sky. The duration of a dark moon varies between 1.5 and 3.5 days, depending on its ecliptic latitude.
In astronomical usage, the new moon occurs in the middle of this period, when the Moon and Sun 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". However, "new moon" originally referred to the crescent phase on the first night it is visible, one or two days after conjunction. Maritime records from the 19th century distinguish the dark moon (no moon) from the new moon.
Video Dark moon
Dark moon as the 30th division
The Oxford English Dictionary defines the new moon 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 is divided into 30 portions, as the ancient Greeks did in the time of Homer, the Babylonians did, and the Indians still do today (calling them tithi), the last phase is called the Dark Moon. In Greek, it was called the Old Moon and associated with Hecate. In India, it is called Amavasya and associated with Kali. Both of these goddesses have a dark connotation, hence the Dark Moon.
In Babylonian, Greek, and Indian culture, the Dark Moon occurs within the 12° of angular distance between the Moon and 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 lasts approximately 23 hours and 37 minutes before the time marked as New Moon on a lunar calendar.
Maps Dark moon
See also
- Amavasya
- Black moon
- Lunar phase
- Syzygy (astronomy)
External links
- http://astrology.about.com/od/foundations/p/DarkMoon.htm
References
Source of article : Wikipedia
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