Phases of the Moon
From AstronomyOutreach network
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*[https://nightsky.jpl.nasa.gov/docs/MoonPhases1.pdf Tutorial: Moon Phases by the Night Sky Network] | *[https://nightsky.jpl.nasa.gov/docs/MoonPhases1.pdf Tutorial: Moon Phases by the Night Sky Network] | ||
*[http://en.wikipedia.org/wiki/Lunar_phase Lunar Phases on Wikipedia] | *[http://en.wikipedia.org/wiki/Lunar_phase Lunar Phases on Wikipedia] | ||
| + | *[http://www.learner.org/vod/vod_window.html?pid=9 A Private Universe Full Movie] | ||
Latest revision as of 23:21, 6 October 2014
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. Due to the varying effects of the Sun's gravity on the Moon's eccentric orbital path, the length of any one lunation (synodic month) can range from 29.26 to 29.80 days .
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Phases of a Lunation
- New Moon 0% Illuminated
- Waxing Crescent 1% to 49% Illuminated (Increasing)
- First Quarter 50% Illuminated
- Waxing Gibbous 51% to 99% Illuminated (Increasing)
- Full Moon 100% Illuminated
- Waning Gibbous 99% to 51% Illuminated (Decreasing)
- Last Quarter 50% Illuminated
- Waning Crescent 49% to 1% Illuminated
Lunar Calendar
Lunar calendars have been in use for at least 10,000 years with the oldest known lunar calendar being found in Scotland. The lunar calendar is 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 a lunar calendar commonly in use today, but is not to be confused with a lunar calendar that is based on astronomical calculations.
A lunisolar calendar is a calendar used in traditional Bengali, Buddhist, Burmese, Chinese, Hebrew, Hindu, Japanese, Korean, Mongolian, Tibetan, and Vietnamese calendars, whose date indicates both the moon phase and the time of the solar year.
Misconceptions of Phases of the Moon
Lunar phases are not caused by shadows being cast upon the Moon by the Earth (which would be a partial or full eclipse), rather the phases are caused by the Moon's revolutions about the Earth, and our perspective of seeing direct sunlight reflect off the Moon from the different positions of the Moon in its orbit.
Misconceptions about how the phases of the Moon are created are pervasive. In the film documentary, A Private Universe several students, ranging from Ivy League graduates to high school students give their ideas of how the lunar phases are created from their incorrect understanding of some of the most basic scientific concepts of astronomy.