“One Planet and Some Debris”

My replacement
My replacement “Sun” at not-quite 8-inches, is surrounded by the planets.

One of my favorite astronomy labs, making a scale model of our solar system, tends to be a real eye-opener for my students.  Maybe that’s why I like it so much; our preconceptions become obvious misconceptions and we are given a new model, a more accurate view of our home.

We began with a table of the sizes and distances of the Sun and planets.  Thanks to Kepler’s Third Law, radar and trigonometry, we have those statistics nailed down.  The students converted miles into inches, a scaled size and distance based on a Sun that is 8 inches in diameter. A neighborhood bowling alley gave me one old, beat-up bowling ball and I have used that flat, blue ball as the Sun for the past decade,

With Play-Doh, the students were amazed how small the model planets are compared to the bowling ball Sun.  They taped their Play-Doh planets to paper and we go outside to make the solar system.

We set the bowling ball at one end of HPU’s promenade.  We talk about rotation and plasma and coronal mass ejections, then take ten giant steps out to place Mercury.

Lucy checks out our solar system.
Lucy checks out our solar system.

On October 2, Dr. Sean Solomon, the Principal Investigator of the MESSENGER mission to Mercury, will be speaking at GTCC, sharing what they learned during the four year investigation of the smallest planet.

Then we stepped out to Venus, say a little about sulfuric acid rain and move to Earth, 1 Astronomical Unit (A.U.) from the Sun.

At Earth’s location we could look back at the bowling ball and see that its angular size is the same as the angular size of the Sun overhead.  This is confirmation that our model is scaled correctly.

We trekked out to Mars and talk about colonization, spread some sand to represent the asteroid belt, and take 95 more giant steps out to Jupiter. 5 A.U.s from the Sun.

“One planet and some debris” might be the way an alien visitor would describe our solar system.  Jupiter has its own collection of moons, and some are very interesting.  We talk about ice on Europa and volcanoes on Io.

Saturn would be another 5 A.U.s out, twice as far as Jupiter is from the Sun,  so we stop here at Jupiter, at the fountain end of the Promenade.  Uranus would be another 10 A.U. past Saturn, past the Greek Village on campus.  Neptune would be anther 10 A.U.   Neptune would be in downtown High Point.

Our next closest star, Proxima Centauri, would be about the size of a tennis ball in our model.  At this scale, how far away would that tennis ball have to be?

(Aside:  This semester while my Thursday morning Lab was out walking the solar system, someone picked up the bowling ball and carried it off. After 10 long years of service our model of the Sun has left us.  Good-night, Sun.)

Our bowling-ball Sun from a past semester. It looked so lonely, maybe someone has given it a good home.
Our bowling-ball Sun from a past semester. It looked so lonely, maybe someone has given it a good home.

“I am flabbergasted at how large our solar system is.” wrote one student.  Another student admitted that “It is mind blowing to see the visual representation of the distances from the Sun.  It is incredible.”

I love my job.


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