The solar system is my favorite part of astronomy to teach. I enjoy getting past the big bang and stars portion of the unit, and discussing things closer to home.
Since I teach high school, students generally already know some basics: the order of the planets, which ones are made of gas, and where the asteroid belt is found. But one thing that is hard to grasp is the size of the solar system…. it is HUGE. (Yes, it’s very tiny in comparison to the universe, but when they learn it would take 12 years to reach Neptune in a rocket ship, they start to grasp how far apart the planets are).
When in doubt, build a model.
I’m big on using models whenever possible. I wanted my students to create a scaled model that showed not just planet size, but distance as well. A company called Mighty Wonderer reached out to me and offered me a solar system model to use with students and I was happy to check it out (you can find it on Amazon). I LOVE that it shows students the size differences between planets, and on each baggie there is a walk-off distance if you wanted to walk off a scaled model. I was hopeful to do this on the football field with students, but once I was looking at the bags I realized that we wouldn’t even get to Jupiter before running out of room- the solar system is just too big to model if you want it truly scaled with distance AND size.
Since I needed a more practical model, I decided to keep the relative size of the planets the same as the provided model, but measure the distance with adding machine tape (cash register tape, whatever you want to call it!) First, I gave each group a 4 meter strip of paper and they had to convert AU distances into centimeters. Then they measured and labeled their adding machine tape so they could see the distances between planets.
For the second part of the activity, students were given an assortment of objects and their task was to analyze a data table of planet sizes and match an object to the correct planet. I used:
- Mercury: Chia seed
- Venus: Popcorn kernel
- Earth: Popcorn kernel
- Mars: Small foam ball
- Jupiter: Ping pong ball
- Saturn: Bouncy ball
- Uranus: Marble
- Neptune: Marble
- Pluto: Poppyseed
Want to try it out? Here are some tips:
- Have the 4m paper pre-measured and cut. It will save class time.
- Don’t have adding machine tape? You could take this activity outside and have them use sidewalk chalk.
- Feel free to substitute out any materials that are roughly the same size. For example, you could use a grain of quinoa instead of a chia seed, or a golf ball instead of a ping pong ball.
- Bring in a basketball (or borrow one from the gym teacher) to show how large the Sun would be in comparison to the planets.
- For the smallest objects (like the poppyseed and chia seed), put it in a microcentrifuge tube so they don’t get lost. You could also use empty litmus paper vials.
You can download the worksheet I used for FREE! here on my website.