Phases of the Moon

Purpose: To demonstrate that the Moon reflects light from the Sun and the phases are determined by the amount of the Moon reflecting sunlight

Key Concepts:
The Moon reflects light from the Sun
The amount of sunlight that the moon reflects changes as the Moon revolves around Earth

Vocabulary:
Crescent - the phase of the moon that is less than half but more than new
Full Moon - the phase of the moon when the visible side of the moon is completely illuminated
Gibbous - the phase of the moon that is more than half but less than full
Moon - a natural satellite revolving around a planet
New Moon - the phase of the moon that is not visible from Earth
Orbit - the path of an object as it revolves around a celestial body
Phase - one apparent form from a sequence of forms
Satellite - a small body orbiting a celestial body
Waning - to decrease gradually in size
Waxing - to increase gradually in size

Material:
4-inch Styrofoam ball, 1 per student
Pencils
Light source
Pictures of moon phases

Set-up:
Place a light source in the center of an open, darken space to represent the Sun. Have students insert a pencil (to hold the ball at a distance) into their Styrofoam ball to represent the Moon. The students are observers on Earth.

Procedure:
1. Have students encircle the light source and hold their moon at arms length slightly above their head.
2. Have students look at their moons and determine how much of the moon is lit by the Sun. (None, the observer from Earth can see that the backside of the moon from Earth NEW MOON)
3. Instruct the students to continue looking at their moon and make a quarter turn to the left. (The right side of the ball is slightly illuminated forming a CRESCENT).
4. Instruct students to continue looking at their moons and make another quarter turn. Half of the ball is illuminated.
5. Have students to continue making quarter turns until all the phases are completed (Gibbous, half, crescent the new again)
6. Define for students that when the moon is growing phase is called waxing and a shrinking phase is called waning (for crescent or gibbous)
7. Discuss with students that the crescent is observed before and after a new moon and gibbous moons occur before and after a full moon.

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