Using Eclipse Glasses to Verify Scale of the Solar System Walk
Each semester my students and I make a scale model of the solar system. We begin with a bowling ball 8 inches in diameter to represent the Sun. Students then calculate the sizes of all the planets to scale and small groups make models from Play-Doh.
After we establish that our scale (1” : 100,000 miles) is for distance as well as size, we take our bowling ball and model planets outside to walk and make a scale model of the solar system. I set the bowling ball Sun down near one end of the campus and we walk to Mercury and Venus, stopping at each for me to say a few words about rotation and revolution, conditions on the surfaces and to give students a chance to ask questions.
This year, when we walked 25.3 yards from our bowling ball Sun to mark the position of the Earth in our model, we got out our eclipse glasses left over from the Great American Eclipse of August 21, 2017. I said a few words about how to safely observe the Sun; students put on the eclipse glasses and looked. After we searched for sunspots, I asked the students to note the apparent size of the Sun in our sky. Then we turned away from the Sun, took off the eclipse glasses, and looked back at our bowling ball Sun.
The first day we took Solar System walk with the eclipse glasses, a few students immediately remarked that the angular diameters of the Sun and our bowling ball appeared similar. One student proudly concluded aloud that our solar system model was, in fact, to scale.
For the rest of the group I reminded them that we were standing on the actual Earth looking at the Sun, and at the same time, we were standing at the location of model Earth looking at our bowling ball Sun. Since the actual Sun and the bowling ball both had similar angular diameters, this indicated that our bowling ball Sun was to scale and the distance from the bowling ball to our model Earth was also to scale.