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Eclipse Model

This is a true scale eclipse model, with both sizes of Earth and Moon as well as distance between them to scale.
[This activity is adapted from the NASA Night Sky Network Shadows and Silhouettes astronomy outreach kit, developed by Astronomical Society of the Pacific]

Materials & Preparation:
  • 1 ball - 1" diameter (Earth)
  • 1 ball - 1/4" diameter (Moon)
  • 1 meter stick or yardstick
  • 2 sticks (popsicle sticks, chopsticks, etc) - attach Moon ball to one stick and Moon ball to the other stick.
  • 2 paper clamps - use these to attach the Earth and Moon ball/sticks to the meter stick.
  • Light (Sun or bright light bulb as model Sun)

What To Do:

Before attaching the Earth and Moon ball/sticks to the meter stick, it's interesting to
  1.  Show only the Earth ball on it's stick and ask "If the Earth were this size, how big would the Moon be? Is it half as big?  1/8 as big?  [Correct answer is that Moon is about one quarter the Earth in diameter.]
  2.  Show the Moon ball on it's stick and ask "at this scale how far apart should the Earth and Moon be? [correct answer is about 31" (79 cm) — the Moon is about 30 Earth diameters away from the Earth.]

Attach the Earth and Moon to the meter stick at the right distance.

Using sunlight or bright bulb, have people try to create a "true scale"
  • eclipse of the Sun where the shadow of the Moon falls on the Earth, and
  • eclipse of the Moon where the shadow of the Earth falls on the Moon.
Both are somewhat difficult.  Which is more difficult?