2021, June 16, Sidewalk Solar System

June 16, 2021:  A summer project is to build a sidewalk solar system model. The scale uses the sun’s size as the size of a basketball.  Earth’s distance is 88 feet.

A solar system model with the sun the size of a basketball.
Photo Caption – A solar system model with the sun the size of a basketball.

by Jeffrey L. Hunt

Build a sidewalk solar system model. It’s a great summer project to show children the relative sizes and distances of the sun and planets.

The equipment needed is a tape measure (the longer, the better), sidewalk chalk for temporary markers or spray paint for a longer-term model.

With any model, making all the scales work is the challenge.  This is evident with the relative sizes and distances of the planets. Can we make the planets large enough, but keep their distance from the sun reasonable?  Well, not really.  A long neighborhood sidewalk is needed.

We start with the sun’s actual diameter, 840,000 miles.  Let’s reduce it to the diameter of a basketball, about 9.55 inches. At this scale the planets’ sizes are tiny, especially the inner planets until Jupiter is marked.  Then place the planets at their distances from the sun.

ObjectScale size (inches)Scale Distance (feet)
Mercury1/3234.3
Venus1/1063.4
Earth1/1088
Mars1/20133
Jupiter15/16457
Saturn13/16838
Uranus5/161690
Neptune5/162646

If you’re building a classic solar system, including Pluto, its distance from the sun in 2021 is 3018.4 feet from the sun.  The planet is small, only 1/200 inch, just a tiny dot.

Have fun with this model.

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Categories: Astronomy, Sky Watching

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