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.
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.
| Object | Scale size (inches) | Scale Distance (feet) |
| Mercury | 1/32 | 34.3 |
| Venus | 1/10 | 63.4 |
| Earth | 1/10 | 88 |
| Mars | 1/20 | 133 |
| Jupiter | 15/16 | 457 |
| Saturn | 13/16 | 838 |
| Uranus | 5/16 | 1690 |
| Neptune | 5/16 | 2646 |
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
- Venus as an Evening Star
- Venus Evening Star (Summary)
- Mars during 2021 (Summary)
- Planets during June 2021
2021 – 2022, Venus – Mars Triple Conjunction
During 2021 into 2022, Venus passes Mars three times for a triple conjunction. The first occurs on July 12, 2021. The others occur during early 2022, followed by a close approach of the two planets.
2021, July 6: Venus – Saturn Opposition
July 6, 2021: This is the second bright planet – planet opposition this month. Venus and Saturn are in opposite directions from Earth. Venus sets about the time that Saturn rises. After this date, Venus and Saturn together are in the evening sky until early 2022.
2021, June 19: Evening Sky, Moon, Spica
June 19, 2021: The waxing moon appears with Spica in the southwestern sky during the early evening hours.
2021, June 26 – June 30: Bright Moon, Morning Planets
June 26 – June 30, 2021: The bright gibbous moon passes Jupiter and Saturn in the morning sky before sunrise. Observe that the moon is in a different spot each morning, farther east toward the impending sunrise.
2021, June 15: Moon, Sickle of Leo
June 15, 2021: The moon is with the Sickle of Leo this evening. Step outside about an hour after sunset to find the crescent moon that is about 30% illuminated over one-third of the way up in the west.
Categories: Astronomy, Sky Watching
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