The Solar System: Modeling the relative sizes of the planets

By Kate Fraser on Nov 25, 2014

with assistance from Stu Grove

Background Information

It is difficult to compare the sizes of the planets in our solar system directly since the solar system is so vast and the planets are so large.   In science making small models of very large items is a helpful hands-on way to compare sizes.  In this activity various household items and food samples are used to represent the planets and illustrate their relative sizes.  This activity is also a good way to review the names of the planets, the inner and outer planets’ locations, but not their relative distances from one another. 

This is sometimes known as the "Earth as a Peppercorn" Activity. The Earth is eight thousand miles wide! The peppercorn is eight hundredths of an inch wide. What about the Sun? It is eight hundred thousand miles wide. The ball representing it is eight inches wide. So, one inch in the model represents a hundred thousand miles in reality.

The original version called for nuts to be used to represent some of the planets. We modified this activity to be safe in a nut-free school!


setting up the solar systemIdentifying a location for the display the model planets is an important part of the preparation for this activity. Also measuring and finding objects to use a the planets can be challenging. We have suggested pin heads and small balls, but any roughly symmetrical object of the approximate diameter can be used.  We fastened the pins to pieces of paper to be displayed. 


  • Ball with a diameter of 8.00 inches (Sun)
  • Pinhead, diameter about 1/16 inch (Mercury)
  • A peppercorn or pin head about 1/8 inch in diameter (Venus)
  • A second peppercorn or pinhead approximately the same size (Earth)
  • A second pinhead red in color slightly larger than Mercury’s pin (Mars)
  • A small ball about 7/8 inch in diameter (Jupiter)  (We used a large glass marble)
  • A small ball about 11/16 inches in diameter. (Saturn) ( We used a round bell)
  • A small ball or coffee bean about 5/16 inches in diameter (Uranus) (For both Uranus and Neptune we used a bead)
  • Another small ball or coffee bean about the same size as the one for Uranus (Neptune) 
  • A pinhead, slightly smaller than the one used for Mercury (Pluto is the smallest planet)

Comparing the sizes of the planets


  1. Place all the objects on trays on a table.
  2. Review the number of the planets. We are including Pluto!
  3. Identify the names of each planet and the order of their locations in the Solar System. The mnemonic MVEMJSUNP is helpful in remembering the order.
  4. Identify which object represents the sun, using the materials list as a guide.
  5. Continue to identify each member of the solar system in order, placing the items about 10 inches apart, on a long table, on the floor or fastened to a wall. Since the relative distance among the planets is not being represented here, placing them close enough so that two or three parts of the model could be examined visually and tactually at the same time is helpful. 
  6. Visually and tactually examine the model.

labeled models of the planets


This activity can be combined with the relative distance activity:

NGSS Standards:

ESS1.B: Earth and the solar system: The solar system contains many varied objects held together by gravity. Solar system models explain and predict eclipses, lunar phases, and seasons.  (grades 6 -8)
collage of the relative size of the planets



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