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.

Articles and Summaries

2021, May 13: The crescent moon is 3.2° to the upper left of Mercury.

2021, August 9: Evening Moon, Mars

August 9, 2021: After the New moon yesterday morning, the crescent moon appears in the evening sky during bright twilight near Mars.

2021, May 13: Brilliant Venus, Mercury, and the crescent moon in the evening sky.

2021, August 3: Four Evening Planets: Venus, Mars, Saturn, Jupiter

August 3, 2021:  Four planets appear in the evening sky.  Brilliant Evening Star Venus and dim Mars are in the west after sunset.  A little later during the evening, Saturn and Jupiter are easily visible in the southeast.

Saturn (NASA)

2021, August 2: Saturn at Opposition

August 2, 2021: Saturn is at opposition with the sun.  Earth is between the sun and the planet.

2020, July 17: The crescent moon appears near Venus before sunrise. The night portion of the moon is gently illuminated by earthshine.

2021: August 1 – 6: Morning Moon, Bright Stars

August 1 – 6, 2021:  The morning moon wanes toward its New moon phase in the eastern sky.  It passes the bright stars that are prominent in the evening sky during the winter season in the northern hemisphere.  The stars have been making their first appearances in the morning sky during summer.  At this hour, Procyon and bright Sirius are the last stellar duo to appear.

2021, July 8: The flowers celebrate summer.

2021, August 6: Summer’s Midpoint

August 6, 2021:  In the northern hemisphere, summer’s midpoint occurs today at 6:27 p.m. CDT.



Categories: Astronomy, Sky Watching

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