WHAT IS ACCRETION AND WHY AM I RUNNING?

Shawn Bean, BHP Teacher
Illinois, USA

Without hesitation, I’d say that one of the most effective Big History activities is Active Accretion (from Lesson 4.0). Students get a chance to go outside (so, choose the day wisely) and run in circles to demonstrate the process of planet formation; they start as a spread-out group of individual dust particles and eventually form a planet.

The day before we’re going to cover the activity, I warn students that they should wear comfortable shoes the next day, as they will be expected to run. It’s funny that many of my students who refuse to run in gym have no problem running in my class; I haven’t had a single student refuse to run (barring those with medical excuses). If a student has a medical excuse, I have them help me out in managing and directing the activity—deciding when the runners should stop, for example.

The goal for the activity is simple: model the process of planet formation through active accretion. The modeling process is also simple: Students (“dust particles”) all run in the same direction around me (the “Sun”), until they form one giant group (or, “planet”). As they run past their peers (and especially larger group of peers), students must link arms with those in that group. The linking of arms demonstrates the gravity that forces the particles together. While they run, students hold signs that designate the size of their group. Everyone starts off as a dust particle, and the groups slowly gain in size until they are chondrules, then meteoroids…all the way up to one, giant planet.

This activity is a great way to get the kids moving, and the lessons learned seem to stick better when they are actively learning. How’s that for active accretion? (Ha ha.)

About the author: This year is Shawn’s third teaching Big History as a year-long freshman world history class. He teaches in the diverse suburbs of south Chicago and has five Big History classes this year. 

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