Understanding the Phases of the Moon
Grade: K-6
Object: to understand why the moon goes from new to full phases
Method: Place two balls and a flashlight on a table. The balls stand for the
earth-moon system, while the flashlight represents the sun. Shine the light on
the 'moon' ball as it is slowly rolled around the 'earth' ball. When the moon
ball is between the sun and the earth, the light will only shine on the 'unseeable'
side of the moon. This is the 'new moon' phase. When the moon is at right angles
to the sun-earth axis, a first quarter moon exists (while it is called 'first
quarter', the moon actually appears half lit). When the moon is behind the
earth, a full moon can be seen. Note that with this model you can also
demonstrate eclipses.
School Instruction: Once the students understand the earth-moon system , and how
it is lit by the sun, have them demonstrate an eclipse. For a solar eclipse, the
moon must be between the sun and the earth. For a lunar eclipse, the earth must
be between the sun and the moon. Ask why eclipses don't occur every day (they
actually do in space, but are not always exactly aligned to occur on earth!).