This shows how the phases of the Moon arise. The diagram shows the orbit of the Moon around the Earth, looking down on the north pole of our planet. At point 1 on the diagram, only the unlit side is observed therefore, unless there is an eclipse the Moon will not be seen, i.e. New Moon. The Moon orbits the Earth and when it reaches point 3, half of the sunlit side will bee seen, so a half Moon will be observed (also called 1st Quarter because at that stage, a quarter of the surface of the moon will be visible). At point 5, all of the sunlit part is visible and we see a full Moon. In between these points, intermediate phases are seen (crescent - between 1 and 3; gibbous - between 3 and 5). The phases are reversed as the moon continues through points 6, 7, 8 and back to point 1. See also the terms waxing and waning in the main dictionary.
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