Why is this science?
Students notice a fuzzy edge to the light spot coming from a tube, and they start to wonder about it. Is it just an artifact of the paper tube? Is it something more interesting? They decide that it needs to be explained.
In earlier conversations, they had discussed a model of light rays that could bounce, and they speculated that the fuzzy edge came from the rays that bounced off the sides of the tube. Some of those rays, they thought, should also go to the center of the light spot, and that led them to put tape in the middle of the beam to block the direct rays. It was a risky experiment, testing something they would not have predicted without the model. After the experiment confirmed their predictions, they collectively worked to refine the model and their terminology. Rather than just “agree to disagree” as competing ideas arise, they worked to sort them out. The students expected that they are building knowledge from their observations and models, rather than consuming canonical ideas.
What Contributed?
Students had competing ideas
Prior to the episode, there were competing ideas about whether light travels in straight lines or in a “wave.” The latter, students said, was “common knowledge,” and they understood it to mean an undulating trajectory. That idea was why Dee was skeptical of Amanda’s explanation for the fuzzy edge. Her skepticism compelled Amanda to explain her thinking more carefully and to seek out experimental verification.
During the episode, there was further disagreement over the precise meaning of “seconds”, which brought up questions that helped further refine their model: Does the ray become a second when it hits the mirror in the flashlight? Should one distinguish firsts, seconds, thirds, etc.? Does a light ray become a “second” only after hitting a surface?
At these moments, students’ desire to figure out which idea was correct drove their engagement.
Students expressed confusion about the phenomenon, terminology, and each other’s ideas
Prior to the start of this episode, Amber and Brooke both had periods where they thought the class’s model fell short, and they were genuinely confused by others’ claims. They mentioned this, and it was part of what spurred the class’s investigation of the fuzzy edge.
During the episode, Courtney was concerned by a lack of clarity around what their drawings should be showing. This started a conversation about why it’s even useful to label a ray a second, which helped to clarify the model.
In these moments, the students’ desire for better understanding helped drive them to think further and their classmates’ to explain more clearly.
One student took a leading role
At several points, it was Dee in particular who expressed uncertainty or identified and revoiced other students’ ideas:
- Yeah, why would they be right there on the edge, why wouldn’t, why wouldn’t the whole thing be fuzzy?
- Oh, I see. And there’s none of the straight ones on the outside.
- So are you sayin’? Or your question is ‘If it bounces on the mirror and then straight out is it a first or a second?’
- So I guess the real question is: when it hits the mirror is any of the light absorbed?… So does the mirror reflect all of it or does it absorb some light?
Other students responded to Dee, and in these moments she pushed their inquiry forward.
Access to simple everyday materials
The class used everyday materials — paper, flashlights and light bulbs, scissors and hole punches, aluminum foil, shoeboxes, etc — rather than expensive lab equipment. That helped the students feel comfortable to do things, such as to dismantle the flashlights, add tape, cut holes, etc. They didn’t need permission or specialized skills, so it was easy for them to design and conduct their own ideas for experiments.
Students presented diagrams of their ideas
A good amount of the discussion centered on the students’ diagrams, such as over precisely how to draw “seconds.” This helped them notice and work to resolve ambiguities and possible disagreements.
Help from the instructors
The instructors’ moves helped center the discussion on the students’ ideas.
- They worked to make sure that students recognized the reasonability of ideas, even ones the students decide are wrong.
- They modeled how to enter a conversation substantively (‘that makes sense to me because…’).
- They planned next moves based on students’ ideas.
- They pointed out the range of ways students were interpreting an idea and called for agreement.
- They supported students’ naming phenomena by adopting the student-generated term.