Using a chart depicting the moon's cycle around the earth, explain to students how the moon revolves around the earth as it circles the sun. This takes about 28 days or nearly one month. From earth we see four phases of the moon in its monthly orbit: new moon, which looks like no moon at all, the first quarter, where only half of the moon is visible, the full moon and the third quarter, which shows the other half of the moon. How we see the moon on any given night is based on how the moon, earth and sun are lined up in their cycles. Fourth grade students are learning the process of using a chart as they study the concepts presented.
Although the moon is often very bright it does not produce any of that light. The moon acts as a great big reflector, flashing the sun's light back to earth. Demonstrate this in a room with a single light bulb. Place a white ball on a stick and sit across from the lamp. Hold the ball slightly above your head between your face and the lamp. With your arm straight slowly spin around while looking at the ball. As you spin you will notice the ball reflecting light in a similar cycle to the moon's phases. The lamp played the role of the sun, your face played the role of the earth and the white ball played the role of the moon. A fourth grader will be able to clearly communicate what he's learned in this demonstration.
Using a chart of the moon's phases illustrate how the moon's shape identifies where it is within the cycle. Often in the night sky a sliver of moon can be seen, this is called a crescent. Other times the moon appears to be oval shaped, this is a gibbous moon. But how can this help explain where in the cycle the moon is. A waxing moon displays a little more of the moon each night as it moves from a new moon to full moon. After the full moon, the size appears to shrink within the sky each night, this is called waning. Give students the opportunity to reference the chart and identify a waxing or waning moon in both its crescent and gibbous phases.
Assign a parent-supervised, 29-day project charting the phases of the moon. Fourth grade students will plan out the project according to instructions given, demonstrating planning, observation and charting skills in addition to their understanding of the concepts presented. Have students create a 29-day calendar on a single sheet of paper. Observe the moon, record its shape by drawing your observations and labeling them each evening for 29 days.