Explaining the Lunar Phase Sequence in a Few Words
During the orbit of the Moon around the Earth, we see various degrees of its surface illuminated. The whole phase cycle lasts 29.53 days and it is called a lunar month. The image shows the eight phases of the moon during this month from two different perspectives, a distant observer's view and the Earth.
1. New Moon: Appears fully shadowed. During this phase, solar eclipses are likely to take place.
2. Waxing Crescent: Only a small edge of the Moon is illuminated (first sliver).
3. First Quarter: The Moon is half-illuminated, forming a 90-degree angle with the Sun.
4. Waxing Gibbous: Appears less than full but more than half lighted. The illuminated region is increasing day by day.
5. Full Moon: Appears fully illuminated. During this phase, lunar eclipses are likely to occur.
6. Waning Gibbous: Appears less than full but more than half lighted. The illuminated region is decreasing day by day.
7. Last Quarter: Appears half illuminated.
8. Waning Crescent: Only a small edge is illuminated (final sliver), before the Moon goes into darkness again.
Click here to see an animation of the lunar phase sequence, as seen from the Northern Hemisphere.