The Moon reflects the light the Sun shines on it.
The apparent changes in its shape, from full to gibbous to half to crescent to new, does not mean the Moon is actually getting smaller or larger.
The Moon appears to wane (grow smaller) and wax (grow larger) because, as it rotates around Earth, we can only see those sections that receive sunlight.
Remember that we can only see one side of the Moon from Earth.
The far side of the Moon is always hidden from us. When the Moon’s orbit places it between Earth and the Sun, the Sun is shining only on the side we can’t see, so we experience a new moon.
Halfway through its orbit, the Moon is on the other side of Earth from the Sun, and we see a full moon.
In between the new and full moons, we see a waxing or new crescent, then a half moon called the first quarter (14 days after new and full moons), then a waxing or new gibbous until the full moon.
After a full moon, we see a waning or old crescent, half moon (also called last quarter) and an old or waxing gibbous leading to the full moon.
We see phases of the Moon because as the Moon orbits Earth, its shadow is thrown onto the surface of the planet.
The inner ring of moons shows what the Moon looks like from Earth.
If you’re still confused, here is a list of the 8 phases of the Moon.
- New moon
- Waxing crescent moon
- First quarter moon
- Waxing gibbous moon
- Full moon
- Waning gibbous moon
- Last quarter moon
- Waning crescent moon
- Dark moon