A Moon phases model project helps you show why the Moon looks different during the month. The Moon does not make its own light, so the bright part we see is sunlight reflecting from its surface. By using a ball for the Moon, a globe for Earth, and a flashlight for the Sun, you can see how the same half of the Moon is always lit.
This project makes an invisible space pattern easy to see in the classroom.
Understanding Moon Phases Model Project
A strong 3D model needs one fixed light source. Place the flashlight on a desk and keep it still. Put the Earth model in the middle, then move the Moon ball around it in a wide circle.
Keep the ball at about the same height as the Earth model. Stand where the Earth would be and look toward the Moon at each stop. What changes is not the amount of the Moon that receives light.
What changes is the angle from which your eyes view the bright half. This is the key observation your project should make clear.
The phase names tell a useful story about what is growing or shrinking in the sky. Waxing means the visible bright area becomes larger night by night. Waning means it becomes smaller.
Crescent describes a thin curved shape. Gibbous describes a shape that is more than half bright but not completely bright. The word quarter can be confusing.
At first quarter or last quarter, people see half of the Moon's disk lit. The name refers to the Moon being about one quarter or three quarters of the way through its trip around Earth, not to the amount of the disk that looks bright.
Your model can explain why eclipses do not happen every month. The Moon's path around Earth is tilted a little compared with Earth's path around the Sun. Most of the time, the Moon passes slightly above or below the straight line needed for an eclipse.
An eclipse needs a very exact lineup. During a lunar eclipse, Earth blocks sunlight from reaching the Moon.
During a solar eclipse, the Moon blocks some sunlight from reaching part of Earth. This difference matters because ordinary phases come from viewing angle, while eclipses come from shadows.
An Oreo display is useful for showing the changing shapes, but it cannot show the true three dimensional positions by itself. Make each cookie label clear and arrange the cookies in order around an Earth drawing. Scrape the cream slowly so the white part has a smooth edge.
In a written explanation, state that the cream represents the part visible from Earth, not the part being lit in space. Pay attention to the order of the phases, the meaning of waxing and waning, and the direction your diagram uses.
Views from the Northern and Southern Hemispheres can look flipped. The cycle is close to four weeks but not exactly four equal weeks, which helps explain why phase dates shift on a calendar.
Key Facts
- The Moon reflects sunlight; it does not produce its own light.
- One half of the Moon is always lit by the Sun, except during eclipses.
- The 8 main Moon phases are new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter, and waning crescent.
- A full Moon happens when Earth is between the Sun and the Moon.
- A new Moon happens when the Moon is between Earth and the Sun.
- One Moon phase cycle takes about 29.5 days.
Vocabulary
- Moon phase
- A Moon phase is the shape of the sunlit part of the Moon that we can see from Earth.
- Waxing
- Waxing means the lit part of the Moon appears to grow larger each night.
- Waning
- Waning means the lit part of the Moon appears to shrink smaller each night.
- Orbit
- An orbit is the path one object follows as it moves around another object in space.
- Sunlight
- Sunlight is the light from the Sun that shines on Earth and the Moon.
Common Mistakes to Avoid
- Thinking Earth's shadow causes the monthly Moon phases. This is wrong because Moon phases are caused by the Moon's position around Earth and how much of its sunlit half we can see.
- Putting the flashlight in the center of the model. This is wrong because the Sun should be off to one side so all Moon positions are lit from the same direction.
- Labeling first quarter as a half Moon without explaining it. This is incomplete because first quarter means the Moon is one quarter of the way through its phase cycle, even though we see half of its lit disk.
- Mixing up waxing and waning. Waxing means the bright part is growing, while waning means the bright part is shrinking.
Practice Questions
- 1 A Moon phase cycle is about 29.5 days. About how many days pass between a new Moon and the next full Moon?
- 2 Your model has 8 Moon positions spaced equally around Earth. If one full cycle is 29.5 days, about how many days are between each labeled phase?
- 3 In a model, the flashlight is on the left side, Earth is in the center, and the Moon is on the side nearest the flashlight. Explain why an observer on Earth would see a new Moon.