Learning science with understanding
In the first lesson, I read the children’s storybook, Dreams, by Ezra Jack Keats. In the story, a young boy’s paper mouse floats away from his bedroom in the top story of an apartment building. As the mouse floats down towards the street, it makes a shadow. As the mouse floats further down the side of the building, the shadow gets bigger and bigger. As it reaches the ground, the mouse makes a huge shadow on the side of the building, and scares away a dog that has corned a friend’s cat. Unbeknownst to most of my students, the pictures in the story are exactly backwards, scientifically, and this offers wonderful possibilities for investigations with children.
As I read the story, I model classroom routines as I gather students into a group on the carpet, arrange seating, and demonstrate how to read the book while showing the pictures. Throughout the book, I ask questions like, “What do you think will happen next?” “What do you notice about the mouse’s shadow now?” “Have you ever seen your shadow get really big?” At the end of the story, I ask students to write about whether they think their own shadows could get really big, like the mouse’s shadow in the story, and draw a picture to help others understand what they’ve written. This is individual work, so that I can get information on each student’s thinking, before we discuss the story together.
As students write and draw, I walk around the room, reading over their shoulders, looking at pictures, asking questions to clarify what they’ve written, and encouraging them to clarify either their writing or drawing, so that others can be clear about what they mean.
In the second lesson, we come back together as a whole class and individual students present their writing, drawing, and thinking about the problem of making shadows bigger than the objects that make them. As each student comes up to the board to draw and explain, I try to make sure that women and minority students in the class are among the first to have a turn, so that we don’t fall into the “white guys know science and we should all listen to them first” stance that is so prevalent at every grade level. When students come up and take an authoritative stance, e.g., “I really already understand this, so I’m going to tell you all how it works,” I intervene with challenging questions, to keep the discussion open and remind all of us that these are ideas and theories, and we don’t have any evidence yet to support them. Once we have heard from every student who wants to present ideas, I check to see if there are other ideas that are different, that haven’t been presented yet. In this way, I model that we want to get all the ideas on the table, so that we all have a chance to consider them, compare them, and look for the similarities and differences among them. At this point, we usually have at least two or three different ideas about what’s going on with shadows ‘ size and models of light to explain those changes, so we talk about how we could test these ideas. This piece is critical, because students often have not had opportunities to design and test their own theories, in their earlier science classes, and may be uncertain about what constitutes a test. We ask each student or pair of students to bring back some representation of their work and findings, whether a tracing of the shadows as they got bigger, a graph of the distances they tried and the related shadow sizes, or a model of light that supports their findings.
Students work in pairs or small groups to set up tests of the different theories that we’ve articulated, most commonly a test between a “tunnel” model of light and an “ice cream cone” model. They have roles in the groups, such as the starter (who takes the first turn), the getter (who retrieves materials and takes them back again), the timer (who makes sure everyone gets an equal amount of time for their turns), and the recorder (who documents what the group is doing and finding). They design procedures for making sure they are measuring accurately, setting up the objects and lights so that they can get comparable data across several measurements, and accounting for variations in the kind of lights they are using. They solve problems such as why the shadow starts to get blurry around the edges, when they go beyond a particular distance between the object and the light. They may trace each shadow separately on paper, or trace all of the shadows’ changing sizes on the same paper. They make turn their measurements into a graph showing the relationship between the size of the shadow and the distances between the light and the object, or the object and the surface behind it. As they are working, I circulate to observe how they are working, pointing out when the young men are dominating the use of materials (a common problem in classrooms at all levels of science), and encouraging the women to take materials and try out their ideas, too. I also look for those students who think they “already know” this science, and ask questions to diagnose how much conceptual understanding they really have. Often, I find that their vocabulary may be impressive, but their understanding of the conceptual principles is shallow, and gently bring this to their attention, so that they can focus on learning, rather than lecturing others in the group.
After students have tested ideas and gathered evidence, they come back to the whole group to share their findings, new questions, and problems. They will usually have found similar results in their tests, i.e., that when the object moves closer to the light, the shadow gets bigger. However, not all of them will have invented a model of light to account for this, i.e., that the light is diverging in all directions from the source, so that an object at one distance blocks a different percentage of the light than the same object at a different distance from the source. So, I have to make sure that we move beyond the findings to how we interpret them and inform our original theories about light and its behavior. It is also important for me to ask about variations in the data the groups present, and ask for explanations that might account for differences. Students also will have found new intriguing questions and findings, e.g., why does the shadow get fuzzier as the object is closer to the light, or why isn’t our graph of shadow size vs. distance of the object a straight line? This provides us an opportunity to talk about how these lessons might lead to others, that would deepen our understanding of the nature and behavior of light. This lesson is an opportunity to help students make personal sense of their findings, look at the role that group discussion and thinking aloud play in their individual understanding, and consider the usefulness of various representations of the data that they have used.
These four lessons are clearly insufficient for helping my students to construct a robust, principled understanding of the physics of light and shadows. However, they provide a taste of authentic inquiry into a problem, especially for students who have never had an authentic inquiry experience in science, and an opportunity for me to model how a teacher might arrange for and scaffold learners’ progress in understanding central theories in science. They also provide important evidence for my most science-phobic students that they can learn science with understanding, and make personal sense of the natural world, with the help of colleagues.