Lunar and Planetary Institute






Moon Phases

Activity: Fruit for Phases


Explore!

This activity follows the demonstration in the lunar phases science story. Children explore the dynamics of lunar phases to develop an understanding of the relative positions of our Moon, Earth, and Sun that cause the phases of the Moon as viewed from Earth. The idea that the Moon does not produce its own light, but simply reflects the light of the Sun, is reinforced.

The Activity

Invite the children to revisit the science story accompanying “The Girl Who Married the Moon.” Share with the children that they will conduct the same experiment, but with a melon or grapefruit instead of an orange,so that the lunar phases will be easier to see.

  • What did the orange represent? (the Moon)
  • What happened to the orange in the story?

Choose a child to hold the fruit representing the Moon. The child's head will represent our Earth. Choose another child to stand with a large flashlight in the corner of the room (or use a lamp); the lamp will represent the Sun. Before turning on the “Sun,” ask the children to observe the fruit.

  • Does the fruit make its own light? (No)
  • Does our Moon make its own light? (No)

Turn the light on and direct it toward the fruit. Invite the children to observe the bright side of the fruit that is reflecting the light, just like our Moon does.

Ask the children why we do not always see a full Moon, illuminated by the Sun, from Earth.

  • When we look at the Moon, if it does not make its own light, why does it look so bright — where does the Moon get its light? (The Sun. In the same way that the Sun illuminates Earth, the Moon reflects the Sun's light, making it appear bright in our sky)

Have the child holding the fruit position it at arm's length, pointing at the light. Invite the other children to stand behind Earth.

  • What do they observe about the Moon? Is the part of the Moon they see from Earth illuminated? (No)
  • What part is illuminated? (The part facing the “Sun” that they cannot observe from “Earth”)
  • Based on this observation, does the Moon really have a “dark” side? (No)

Invite the children to move around the Moon to observe the side that is illuminated. Invite them to stand behind the Sun and discuss what they see.

  • Is the side of the Moon facing the Sun always illuminated? (Yes, just like the side of Earth facing the Sun always is illuminated)
  • What phase of the “Moon” are they observing from “Earth”? (The new Moon)

Ask the child holding the “Moon” to slowly turn 180 degrees, or a half-circle in the direction that our Moon orbits Earth, keeping the Moon at arm's length and slightly higher than his or her head. Invite the other children to share their ideas of the Moon's direction of revolution ( counterclockwise if viewed from above in the northern hemisphere; or to the left ).

  • As the Moon revolves and changes positions in relation to the Sun, what happens to the illumination of the Moon's surface as viewed from the Earth? (It increases until the side facing Earth is fully illuminated)

Make sure that all the children observe the change in illumination; they will have to move so they are observing the Moon from the same direction as the child holding the Moon.

  • What phase of the Moon are they observing when they have orbited half way around the Earth? (A full Moon)

Once the children are comfortable observing the changing illumination of the Moon, repeat the exercise so that each Moon phase is revealed. Start with the new Moon and have the child holding the fruit rotate in steps of 45 degrees, pausing at each of the eight phases to invite the children to make observations about the illumination and to identify the phase.

The children may wonder about Earth's rotation and the movement of the Moon. Remind them that Earth is spinning once on its axis each day, while our Moon is orbiting Earth approximately once each month. To illustrate this, pause the activity periodically and have another child hold the Moon wherever it is in its cycle. Have the child representing Earth spin slowly counterclockwise. Invite the other children to make observations about Earth's day and night cycle relative to the illumination of the Moon.

  • What does the child representing Earth observe?

Invite the children to continue their exploration, having them exchange roles. Ask them to recount the patterns of changing illumination they observe. Use randomly selected cards of the Moon's shape to challenge them to explain the positions of the Sun, Earth, and Moon during that stage of illumination.

Extensions

As an extension, share the Phases for Phrases song with the children and use the plates to identify and learn the names of the phases.


 

Last updated
January 9, 2007

 

Who?
Ages 8–14

How Long?
50 minutes

What's Needed?

This activity can be presented as a demonstration involving the children or it can be undertaken by small groups of children.

For each group:

• Cantaloupe or large grapefruit (a 6" Styrofoam ball can be substituted)
• Lamp or flashlight
• Eight index cards, each with an illustration of a different Moon phase

Connections to the National Science Standard(s)

Standard A (grades K–4): Model the phases of the Moon to understand lunar phases. Understand the pattern of movement of the Moon across the sky, as well as the observable cycle of changes in the Moon's shape within a month.

Standard A (grades 5–8): Model the phases of the Moon to understand lunar phases. Understand the scientific explanation of how objects in the solar system have regular and predictable motion that explains such phenomena as phases of the Moon and eclipses.