The Moon is a bright object we can often see in the night sky. It can look like a thin crescent, a half circle, or a big round full Moon. These shapes are called Moon phases, and they repeat in a pattern about once each month.
Learning the phases helps young students notice patterns in the sky and talk about what they observe.
The Moon does not really change its shape. We see different amounts of the Moon's sunlit side as it moves around Earth. When the sunlit side faces us fully, we see a Full Moon, and when it mostly faces away from us, the Moon is hard to see.
A simple Moon phase path shows the shapes in order: New Moon, Crescent Moon, Half Moon, Full Moon, Half Moon again, and Crescent Moon again.
Key Facts
- The Moon's shape in the sky is called its phase.
- The Moon phase cycle takes about 29.5 days.
- New Moon means the Moon is hard to see because the bright side faces mostly away from Earth.
- Full Moon means the Moon looks like a bright circle because the bright side faces Earth.
- Crescent Moon means only a small curved part of the Moon looks bright.
- Half Moon means about half of the Moon's face looks bright and half looks dark.
Vocabulary
- Moon phase
- A Moon phase is the shape the Moon appears to have when viewed from Earth.
- New Moon
- A New Moon is the phase when the Moon is very hard to see from Earth.
- Crescent Moon
- A Crescent Moon is a phase where the bright part looks like a thin curved banana.
- Half Moon
- A Half Moon is a phase where about one half of the Moon looks bright.
- Full Moon
- A Full Moon is a phase where the Moon looks like a big bright circle.
Common Mistakes to Avoid
- Thinking the Moon really changes shape is wrong because the Moon stays round, but we see different amounts of its bright side.
- Calling every bright Moon a Full Moon is wrong because a Full Moon looks like a complete circle, not just a partly bright Moon.
- Thinking the Moon makes its own light is wrong because the Moon shines by reflecting sunlight.
- Putting the phases in a random order is wrong because the Moon phases follow a repeating monthly pattern.
Practice Questions
- 1 The Moon phase cycle is about 30 days for a simple model. If a Full Moon happens on day 15, about what day would the next Full Moon happen?
- 2 A child sees a Crescent Moon on Monday and the class is using a 30 day Moon cycle. About how many days are in one full Moon phase cycle?
- 3 Look at these Moon shapes in order: New Moon, Crescent Moon, Half Moon, Full Moon. Explain why the Moon can look different even though it stays round.