Recently during the 2009 AAPT Summer Meeting in Ann Arbor, we had the chance to talk with CoolStuff Contributor Joe Spaccavento. As always, Joe had another great idea for us. This time on how to introduce the concept of scale and distance to students in a very memorable way. In his unassuming way, Joe shared a great idea he got direct from NASA, all the while pulling an un-inflated beach ball replicating the Earth from his jacket pocket. Between breaths trying to quickly inflate the Earth, Joe started with his questions…
Joe Spaccavento, Physics Teacher
North Arlington High School, New Jersey
With respect to this globe, how far is 200 miles? Well, look here (pointing to the globe) New York City to Boston is about 200 miles. With respect to this globe, that’s about this far. (Holding up his thumb and fore finger barely apart.) Then he asked, “How far out does the Space Shuttle orbit?” Answers are offered all around; 230 miles, 200 miles, 180 miles… Well, it’s about 200 miles. The holding up the Earth Ball, he points out that the shuttle would be in orbit around the Earth about here… (Again with his finger barely off the surface). Surprised faces all around.
Then he asked, “What about the orbit of a Geosynchronous Satellite?” Answer: about 22,000 miles above the surface of the Earth! Again using the Earth model he explains that the Earth’s diameter at the Equator is roughly 7,926 miles. Our model here is about 1 ft in diameter. So let’s say 1 ft. = 7,926 miles. That’s the “scale” we’ll use.With that we can say that the Satellite is about 2.8 ft away from the surface of this model. None of us had any idea as to the scale of these distances until this simple demonstration made it perfectly clear. And on it went. How far to the Moon? The Sun?Joe went on to explain that the demo works so well, that he has started using multiple inflatable earths, set in a line to make it fun for the students as they become involved. This demonstration engages students and creates a lasting impression that won’t be forgotten. Joe has provided his spreadsheet of distance data and scale conversions in a free download for your use.