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Measuring the Changing Size of the Moon
Grade: K-6

Object: to show that the moon has a different visual diameter as it goes through its monthly cycle. This is because the moon does not have a circular orbit around the earth, but an elliptical one. It is closest to us during full moon phase, and furthest during the new moon phase.
Methods: have the student go out on various nights during the month. Have them hold a small ruler at arm's length (the distance between the eye and the ruler is the one thing that must be kept constant). Measure the diameter of the moon, and record these measurements on paper. They should increase from early phases up through the full moon.
School Instruction: have student's draw an earth/moon diagram, using an ellipse for the moon's orbit (you will probably need to demonstrate this at the blackboard). Show them how a moon closer to earth will appear larger, and one further away will appear smaller.