Students turn TTU campus into a scale model of the solar system

Posted by Lori Shull - Wednesday, December 14 2011


If the solar system was the size of the Tennessee Tech University campus, the sun would be slightly larger than a grapefruit in Bruner Hall and Pluto would be a grain of salt in the nursing building.

For a few days at the end of every fall semester, TTU physics professor Steve Robinson and his Intro to Astronomy course create a miniature solar system on campus. Most people don’t notice it; many of the planets and other celestial objects amount to little more than a bead taped to a piece of paper in a hallway.

“People really don’t have a good feeling for the relative size and distance between objects in our solar system,” Robinson said. “In a typical classroom, it’s impossible to make an accurate model of the solar system with the relative sizes and on the same scale.”

Students are assigned various objects in our solar system, including planets, moons and asteroid belts. Then they have to use proportional math and scaling to figure out how big their object would be and how far it would be from the grapefruit-sized sun.

“I’ve been doing this for several years and it still amazes me how different the real scale of the solar system is to the one in our minds,” Robinson said. “This is a ‘Gee Whiz’ thing. You thought you knew what the solar system is like but really you don’t.”

As part of the class, students initially create their own model of the solar system, based solely on their intuitions of how big things are and how widely spaced. Every year, they select objects too large to represent the planets and place them too closely together, Robinson said.

During the last week of classes, Robinson goes on a scavenger hunt down the halls of the campus’ academic buildings to find the items, and short papers, that his students have placed.

His walk to Mercury, Venus and Earth is short; all three are down the hall from his office in Bruner Hall with the sun. The bead representing Mercury looks like little more than a large air bubble under a piece of tape. Neptune is easier to see; it is about a quarter of an inch in diameter. But the walk to South Hall, where it is placed, is longer.

“They’re amazed at how their intuition is different from reality,” Robinson said. “That’s the importance of the project for me; how the concept of the solar system you’ve grown up with is so different from the true scale.”

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