The phases of the Moon are the different ways the Moon looks from Earth over about a month. As the Moon orbits around the Earth, the half of the Moon that faces the Sun will be lit up. The different shapes of the lit portion of the Moon that can be seen from Earth are known as phases of the Moon. Each phase repeats itself every 29.5 Earth days even though the moon takes 27.3 days to orbit the Earth. We have to account for the different angle of the Sun as the Earth-Moon orbits the Sun.
The same half of the Moon always faces the Earth, so the phases will always occur over the same half of the Moon’s surface, this occurs due to the phenomenon called tidal locking or gravitational locking where the time it takes for the Moon to rotate once is approximately the same as the time it takes for the Moon to orbit the Earth. Also notice the slow rocking and wobbling of the moon is due to the lunar libration. We can actually see 59% of the moon during the whole moon phase due to the lunar libration.
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