Isaac’s Wheels – Reflections

Why is this science?


Roger Tobin, Professor of Physics, discusses Isaac’s thinking and the physics of rolling.

There are several features of this episode that make it science.

First, the children are trying to make sense of phenomena they’ve seen in the world. In this case, the phenomena are familiar (rolling, moving, and slowing down), but the children are studying them with a new level of attention, trying to pin down mechanisms with precision. Along the way, they form their own questions, and they assess and refine the quality of possible answers.

Second, they draw on and work to coordinate their understanding with their knowledge of other phenomena. Isaac’s idea of “keeping track” connects rolling with gear teeth meshing, to explain how a wheel can move without dragging. His classmates check his reasoning for consistency with their knowledge that something has to start the car moving and that it will slow down.

Finally, the students hold Isaac accountable to sensible, mechanistic reasoning: The floor can’t be what makes the car go forward; wheels getting “tired” can’t be what makes it slow down.

What contributed?

Studying the case, we see several things playing a role.

The teacher’s contributions
Sharon’s contributions were both administrative, to orchestrate turn-taking and attention, and substantive.

She calls on Isaac to explain his journal entry. She did not understand it at first, either from reading his notebook or from his initial explanation, but she knew he had spent time and effort working on it, and it seemed promising. Sharon’s choice to focus on Isaac’s idea reflects her sense of meaningful explanations in science, her general stance that it is important for children to express their thinking, and her particular goal of their doing science.

She also contributes as a model participant, posing her own questions (“what do you mean by keep track?” and “what pushes the wheel?”) as well as recognizing and supporting students’ questions (“I was wondering that too…” and “I had the exact same question!”).

Along the way, she guides the flow of conversation, coaching Isaac on making things clear (“I want you to tell me about that first before you talk about the bike”), making sure he hears and responds to classmates (“Will you listen to [Scarlett’s] question?”), and coaching the class on paying attention (“I’m really paying attention to every word he says…”).

The students’ expectations of sense-making
After several weeks of doing science in this way, the students have evidently formed a sense of what it entails. Where earlier the children (Isaac included) had made fantastical, implausible suggestions about the car’s motion, in this episode they raise ideas and concerns about mechanism and coherence. Isaac works to explain rolling; his classmates push him to make his assumptions explicit and to come up with a mechanism for why the car stops. In earlier classes, too, the children showed they expect to contribute ideas and questions, and that is evident here as well.

The students’ knowledge and abilities for sense-making
Finally, it matters to the conversation that the children have ideas! They come in with a great deal of “background knowledge” about motion from everyday experience. They know that pushes and ramps can make a toy car start moving, and that a flat, inert floor cannot; they know that tiredness is a temporary state mitigated by resting, something they experience but a wheel does not.

Their intuitive resources for conceptualizing motion include both the idea that motion needs a cause as well as (impressively!) the alternative idea that stopping needs a cause, such as dragging or scratching. Isaac knows about bicycles and gears, how gear teeth mesh together, and he seems to synthesize a more general notion of “keeping track,” a one-to-one correspondence between points on objects.

By the same token, the children have resources for reasoning by analogy, evident both in Isaac’s appeal to gears and in Scarlett’s and Jamir’s critique of the tacit analogy to people in the idea of wheels getting tired.