In this activity, students collect data on the lunar phases using a simple Earth-sun-moon model consisting of a flashlight, a foam ball on a pencil, and a circle of paper divided into eighths. A student, holding the moon in constant position, rotates 45 degrees until returning to the starting position, resulting in a model of the moon’s phases. Photos or drawings document the moon phases, and then the cycle is used as a model to predict lunar phase dates for the next 3 lunar cycles.
MS-ESS1-1. Develop and use a model of the Earth-sun-moon system to describe the cyclic patterns of lunar phases, eclipses of the sun and moon, and seasons.
No PPE is required for the activity.
Copy or upload the student activity guide. Assign students to groups (3–4 per group). All materials may be reused.
Observations and Positions in Degrees
Use your data table to explain the pattern of light and dark produced by the Earth-sun-moon model.
See the NASA diagram below.
Explain the differences between the lunar phase pattern you observed and the one presented in the phenomenon.
Student answers will vary, but the most obvious difference is the length of the cycle. The student-generated cycle is 8 phases long and the cycle in the phenomenon is 29 phases long.
Using your lunar phase model, explain why lunar phases happen.
See the NASA diagram below. Pay particular attention to the position of the moon relative to the sun and Earth.
NASA/JPL-CalTech “This graphic shows the position of the Moon and the Sun during each of the Moon’s phases and the Moon as it appears from Earth during each phase.”
Use the lunar phase model charts to predict the date and phase of the next 3 lunar cycles.
Check student predictions after they happen through nightly observations, or use a lunar calendar to check prior to the date by selecting the month and year.
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