Why Do Eclipses Happen?

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Sometimes it is hard to imagine why eclipses happen. Try this experiment and see if it helps you to understand.

Materials Needed:

a grape to represent the Moon
an orange to represent the Earth
a toothpick
a piece of styrofoam (about 1/2 inch thick by and inch or two high and wide)
a desk lamp to represent the Sun
a ruler

1. Take the styrofoam and stick the toothpick securely into it. Stick the grape on top of the toothpick so it is about two inches high.

2. Place the orange about three inches behind the grape on a table.

3. Shine the desk lamp (Sun) directly at the Moon and Earth from about 1 foot away.

Cartoon of eclipse demonstration.

Look at the Earth. What do you see?

You should see a shadow that is darker in the middle and lighter on the outside. The darker part of the shadow represents the umbra, the shadow of the Moon in which total solar eclipses can be seen.The lighter part of the shadow represents the penumbra, from which only partial solar eclipses are seen.

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StarChild Authors: The StarChild Team
StarChild Graphics & Music: Acknowledgments
StarChild Project Leader: Dr. Laura A. Whitlock
Curator: J.D. Myers
Responsible NASA Official: Amber Straughn