Use a light bulb, turned on with its lampshade removed, to represent the sun. Have students stand in a semicircle holding a styrofoam ball at arm’s length, using a pencil that they stick into the ball, and then make the room as dark as possible. Explain to the students that the light bulb represents the sun, their Styrofoam ball the moon, and their heads the Earth. When you get the children to position their balls so that they are opposite the light bulb and their heads throw a shadow on the balls, they understand how lunar eclipses occur when the moon gets into the Earth’s shadow.
Considering that the moon’s plane is tilted, we don’t have lunar eclipses every month. Demonstrate this by holding two hula hoops, not in the same plane, over your head. One hoop represents the sun’s yearly orbit and the other the moon’s monthly orbit, with your head filling in for the Earth. Make it clear though, that the sun does not orbit the Earth. This model helps demonstrate that orbits of the sun and the moon are lined up twice a year in such a way as to make lunar eclipses possible.
A model that uses a scale based on the distance between the Earth and the moon, and the Earth and the sun, can help demonstrate the moon phases. Hammer down two nails, each about 3 to 4 centimeters (cm) long, into a wooden strip that is 125 cm long. The distance between the two nails should be 120 cm. Place a styrofoam ball of 4 cm diameter on one nail, representing the Earth, and another of 1 cm diameter, for the moon, on the other nail. In a place where the moon can be seen, and it is also sunny, point the moon sphere towards the real moon, with the Earth sphere right in front of your face. By altering the orientation of your model moon, you can demonstrate how the moon goes through different phases as the light it gets from the sun varies. Also explain how lunar eclipses are only possible during the full moon phase.
It is also possible to simulate a lunar eclipse using the scale model and an overhead projector that represents the sun. By pointing the Earth towards the projector, you can demonstrate how the Earth’s shadow can obscure the moon, creating a lunar eclipse.