Phases of the Moon
From AstronomyOutreach network
The Moon is Earth's constant companion and only natural satellite. One of the largest and most dense moons in the solar system, it appears very bright in the sky and can be seen in broad daylight, although in reality the surface is quite dark.
The Moon orbits the Earth every twenty nine and a half days, and it is in synchronous orbit, so the same side of the Moon faces the earth at all times. However the lit part of the Moon as seen by the Earth changes as it makes its orbit, going from the New Moon phase (when the Moon appears dark) to the Full Moon phase (when the Moon appears fully illuminated) and back again, which is called a lunation. This is not caused by shadows being cast upon the Moon by the Earth (which would be a partial or full eclipse), rather the phases are cased by the Moon's revolutions about the Earth.
Here are the phases in order:
- New Moon
- Waxing Crescent
- First Quarter
- Waxing Gibbous
- Full Moon
- Waning Gibbous
- Last Quarter
- Waning Crescent
Lunar Calendar
Lunar calendars have been in use for at least 10,000 years with the oldest known lunar calendar being found in Scotland. It's a calendar based on cycles of the lunar phases. Because there are slightly more than twelve lunations (synodic months) in a solar year, the period of 12 lunar months (354.37 days) is sometimes referred to as a lunar year. The origin of the word "Month" is related to the word "Moon" and is rooted in Old English "mōnath", of Germanic origin; related to Dutch "maand" and German "monat".
The Hijri Qamari is the Islamic calendar which is the lunar calendar in use today. The Islamic calendar is always 12 months, so the months are not linked with the seasons and drift each solar year by 11 to 12 days. It comes back to the position it had in relation to the solar year approximately every 33 Islamic years. It is used mainly for religious purposes, but in Saudi Arabia it is the official calendar. Other lunar calendars often include extra months added occasionally to synchronize it with the solar calendar.