Cresent Moon as seen from Earth
In the following display note that the Moon, in the inner loop, dosen't change. For this to occur an observer most be looking at the moon from above the north pole. The outer loop shows an obsever looking at the moon from a location on earth.
Moon Phases as seen from two observation points
The Moon's Surface
- When the Moon is between the Earth and the Sun in a nearly streight line the dark surface cannot be seen which is called the New Moon.
- As the Moon moves in a counter clockwise direction away from the New Moon it moves into the crescent stage thus showing a growing illunimation of the Moon surface as seen from the Earth. It is called the Waxing(growing) Crescent Moon.
- First Quarter is when the Moon is at right angle to the line joining the Sun and Earth, thus completing 1/4 of its orbit. The growing illunimated surface continues into the Waxing Gibbous phase and into the Full Moon when the Moon has completed half of its orbit.
- After the Full Moon the illunimated surface gradually dwindling thru the Waning Gibbous phase into the Third Quarter and onto the Waning Crescent. Finally we see the darkness of the New Moon completing one full orbit of the Earth. Note in making one orbit, from New Moon to New Moon, takes 29 1/2 Apparent Solar days or Mean Solar days. One Sidereal Lunar Month is 27 1/3 solar days.
In the image above it shows the Sun in the center and the Earth in two different positions labled E1 and E2. When the Earth is at E1 and the Moon is at M1 , the New Moon, and 27 1/3 days later the Moon completes one orbit moveing it to the second position M1', but meantime the Earth has moved to the position E2 and the Moon must now moved to position M2 to be properly lined up with the Sun and Earth again. The time for the Moon to travel from the M1' position to M2 takes a little more then two solar days to make up the differents of 27 1/3 and 29 1/2.
