Worlds in Comparison

The Astronomical Society of the Pacific has a wonderful program called Family Astro that has various activities you can do with groups (such as families) that are fun and impart some astronomical insight. One of them is called Worlds in Comparison and involves making a set of models of the planets to the correct relative scale out of a lump of about 3 pounds of play-dough. Pluto (if you are inclined to include it despite its recent demotion) ends up being smaller than some of the random crumbs left on the table from the early divide and merge operations. You can figure out the proportions yourself using the data from the website www.nineplanets.org.

However, the point of this commentary is to say, never, never, never attempt to do this with first graders. I did this with my own two boys, ages 6 and 8 in first and third grade and it worked well. I did with a couple of families whose children are middle- and high-school aged. Then I did with a complete classroom of first graders. Of course, the teacher was there and the two of us did most all of the exercise jumping from table to table to help them. First graders simply don’t have the fine motor skills necessary during the later stages of the exercise.

The process starts with dividing the lump of dough into 10 parts; 6 go to Jupiter, 3 to Saturn, and the remainder goes to the next round. Again, divide into 10 parts; 5 go to Saturn, 2 to Uranus, 2 to Neptune with 1 for the next round. And it goes on. Very quickly the children simply can’t do it. Of course, many of the children simply don’t know how to go about dividing the dough into 10 equal parts in the first place.

I would not label the exercise a failure, not exactly. The children were quite impressed with how small Earth was compared to Jupiter and were astounded at how miniscule Pluto turns out to be. So they did come away with a good visceral feel for the relative sizes (I think they did). But the exercise itself it simply too difficult for this age group.

FWIW, I also did it with a fourth grade group a couple of weeks later and discovered they also have some trouble with an efficient strategy for dividing a lump of dough into 10 equal pieces. Many of them started forming small balls immediately before they had divided up the dough and then spent a lot of time trying to correct the sizes. Hindsight being 20-20, I think this is why it is called Family Astro.