1. The Moon and its Phases

2. The Phases of the Moon
The Moon is unique in that it has phases, that is it is not always round. It “waxes” (gets larger) and “wanes” (gets smaller)
A “New” Moon is really no Moon at all,
a “Quarter” Moon is a half-circle lit,
A “Gibbous” Moon is more than quarter but not Full.

3. Thus the phases are:

4. The Phases are the result of the Moon’s orbiting Earth.
From Earth how much of the lit side of the Moon we can see depends on where the Moon is…
“New” Moon(no visible Moon) happens when the Moon is in front of the earth and we can only ‘see’ the dark side.
A Quarter Moon is when the Moon is alongside the Earth so that we see only half the lit side.
Full is when it is behind the Earth and the whole lit side can be seen. The rest are in between.

5. The Sun is Here
Notice that the Moon is in opposition during a full moon and thus can be seen at night
From Last to 1st quarter it is up during the day

6. A Month
A month is roughly the time it takes for the Moon to go through its phases
It takes about 29 ½ days
This does NOT match its period of revolution
days
because the motion of the Earth around the Sun changes the direction of the Sun.
(copy diagram)