ALCA Members PLC Domains Data Standards Map Plan Curriculum Assessment Strategies

Earth and Moon: What a Pair! Copy

Students may know that the moon is one-fourth the diameter of the earth. However, the moon is MUCH LESS than one-fourth the volume of the earth. This lesson demonstrates this concept. Also included in the lesson's enrichment activity is information on applying the concept to the earth-sun relationship.

Teacher Goals

  • Radius, Volume Relationship - This activity will demonstrate some simple geometric relationships involving spheres.
  • Moon, Earth Size Relationship - This activity will help the student to relate comparative sizes of the earth and moon.
  • Concept Enrichment - This activity will allow the instructor to add other examples of sphere/size relationships to ensure student understanding.

Required Resources

  • Large sphere (ping-pong ball, tennis ball, etc) This sphere will have a hole cut into it during the activity.
  • Clay or play dough
  • Knife or scissors
  • Reference books
  • Earth and Moon Performance Assessment Checklist

Optional Resources

  • Eric W. Weisstein's World of Astronomy
    Eric W. Weisstein and Wolfram Research, Inc. offers this website of interesting astonomical information.
  • Website for Measuring the Moon's Diameter
    This site is hosted by York University.
  • Space and Science Website
    The Minnesota Space Frontier Society hosts Jeff Root's website, which provides some incredible information about space.
  • Space Website
    Windows to the Universe, the University Corporation for Atmospheric Research (UCAR), and the Regents of the University of Michigan offer this site for educational purposes.

Steps

  1. Calculating Volumes

    pi (r cubed). Now look up the radius of the moon. Calculate the volume of the moon using the same formula.

    Divide the volume of the earth by the volume of the moon.This will tell you how many moons it would take to fill up the earth.

  2. Measuring

    After your instructor gives you a sphere of some type, carefully measure the diameter of the sphere. Next calculate the radius of the sphere. Then calculate one-fourth the radius of the sphere.

  3. Opening the earth

    Carefully cut a hole in one side of the sphere. Cut 4 pieces of clay and form small clay spheres that measure one-fourth the radius of the large sphere.

  4. Filling the Earth

    Carefully put the four small spheres into the large sphere. Do they fit easily? Estimate how many clay spheres it would take to fill the large sphere.

  5. ENRICHMENT

    Expand on this experiment by looking up the diameter of ther sun or some other planets in our solar system. How many earths would it take to fill the sun, or Jupiter?

  6. Comparison

    Your answer to number 5 would also apply to the clay sphere experiment you performed because you kept the ratio 1 (moon) to 4 (earth). How close was the estimate you made in Procedure 4? Where could some experimental errors be?

Teacher Notes

  • This activity is very simple, clean, and easy to expand. Care MUST BE TAKEN when cutting the hole in the large sphere! Some possible spheres to use include ping-pong balls, old tennis balls, old playground balls, etc. Only a small amount of clay is needed (depending on the size of the large sphere). Most students will probably have a calculator that has a pi key on it. If not, 3.1416 will suffice. This would be a good time to introduce what pi is. The students will probably estimate very low on the number of "moons" that will fit into their "earth." Upon doing their reference research and calculations, they should come up with an answer fairly close to 64.
  • Students will read that the moon is one-fourth the diameter of the earth. However, the moon is MUCH LESS than one-fourth the volume of the earth. This concept is demonstrated in this lesson. Also included in the enrichment activity is information on applying the concept to the earth-sun relationship.

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