Carolyn (Schmidt) Balch
National Air and Space Museum
(Author's note: This article is slated to appear in the May/June issue of the Teacher's Laboratory newsletter, "Connect." It chronicles what I learned during a field-testing about how kids learn and what they think about fundamental concepts important to flight (gravity, air pressure, weightlessness, etc.). It's more broadly constructivist (on getting inside kids' heads) and less focused on inquiry per se.)
As a curriculum writer for the Smithsonian, I am currently working in middle schools trial-testing activities on flight for visitor handouts. Although I do most of the preparation, teaching, and assessment development for the students, I am still an outsider in their classroom. Although this is frustrating at times, this also allows a certain objectivity I never experienced as a full-time teacher.
My teaching style has evolved over time. I used to focus on how well I explained concepts---I now concentrate on how well students understand them. If I have learned anything in my career, it is that true understanding takes time. Students have to develop a rhythm of predicting, exploring, and reflecting on how new information affects their current understanding. A co-participant in this quest, I work with students to help them become aware of and be able to verbalize how they understand any given concept. Here are some thoughts along the way.
Air only has pressure when it's moving. Some students have a tough time understanding the concept of air pressure. They are confused by how something invisible can be constantly pressing on them. The most concrete thinkers reason that air only has pressure when they can feel it---during a breeze or by squeezing a container. A complete understanding of flight is difficult for these thinkers.
Air has no weight. While most middle-level learners realize that air is a substance, many do not think of it as having weight. Of those who say they know this, many "forget" to apply this concept during investigations. Understanding that air has weight is the key to understanding ambient air pressure.
An invisible covering holds Earth's air. When asked why Earth's air does not float into space, nearly all students said, "Gravity," which is true. But many of my students also thought there was an invisible covering surrounding Earth's air. Students referred to this as "The Atmosphere," "The Ozone," or "A Shield." This covering explains many things---why rockets are pointy, how radiation is kept out, and how air is kept in---each of which needs to be addressed. Addressing these "explanations" is complicated by the fact that they each contain truth and therefore cannot be dismissed out of hand. Even after students realized that gravity holds air down (resulting in weight and air pressure) some still needed "the covering" to hold in the air above them. They had no sense that air above was simply sitting on the air below it and that they were submerged at the bottom of this sea of air.
There is no gravity in space. This misunderstanding tends to be reinforced rather than challenged in students' everyday lives since it is widely held by the general public. Part of their confusion stems from their understanding that gravitational strength decreases with distance. This effect, while real, is not the reason for orbital weightlessness. (An orbiting space shuttle isn't far enough away to experience much difference in Earth's gravitational pull. In measurable terms, a 100 lb student standing on a 200-mile-high ladder---the height of a space shuttle orbit---would weigh about 91 lb.) Objects in space are weightless because of their motion, not their location. Thus orbiting astronauts are weightless because they are in free fall, not because they are in space.
Middle-learners aren't consistent in their ability to think abstractly Comments like, "Air doesn't weigh anything," and "Submerged objects weigh nothing," led us to wonder if these students were non-conservers (which we didn't expect at this age). During the project I became convinced that these comments were rooted in their ability (or lack thereof) to think abstractly. I'm now convinced that nearly all of the conceptual problems I observed can be traced to this one cause.
Conflicting beliefs don't seem to generate much cognitive dissonance. Offer high schoolers data that contradicts their beliefs and they'll feel compelled to investigate. By contrast, middle learners find this approach lackluster. Because they are driven by a quest to experience, they don't seem to be stimulated solely by intellectual curiosity. For this reason they may or may not discard an old understanding even when presented with a better one---it's not that they don't see the difference, it just not what they focus on. I admit I found this maddening, but also I found I had to deal with it. In some cases I had to be satisfied that the students were acquainting themselves with the phenomena and hope that understanding would come later.
Students not used to understanding science don't worry when it doesn't make sense. I am constantly asking students, "But does that make sense?" I have found that if new information doesn't make sense to students, they will soon discard it and retreat to their pre-existing framework. I think that one reason they don't question their thinking is that they often don't have to. If, when I am teaching, I eventually give them answers, then they know their real job is memorizing, not understanding. In this scenario the student can give the right answer, "Gravity," while still believing that an invisible covering surrounds Earth's air. As I've learned to guide rather than tell, I've also watched students become more interested in learning.
Students are upset by wrong predictions. Students often changed their predictions once they saw what really happened in an investigation. Since I wanted records, I began collecting the predictions mid-class. Later, I used them by asking students to analyze how their thinking had developed. I constantly assured them that "being wrong," as they put it, is a normal part of this process: true hypothesizing means entertaining all credible ideas until you can replace them with better ones.
Forty minute periods thwart investigation. I found period scheduling far more constraining than self-contained classrooms, though I spent comparable time in each. With periods we rarely seemed to have the time we needed to reflect and question. It's hard enough to be reflective in group settings; this type of schedule can make it more difficult. I also noted a tendency for students to wait things out if they didn't enjoy or understand an activity. They knew the period would finish whether or not they did.
Students are more intrigued by experiencing than by understanding. One strategy I tried was to have students predict outcomes and vote on these before experimenting. I asked kids whether they could (without moving) stand, squat, kneel, etc. on a bathroom scale so that it would show a reading other than their weight. They predicted and voted before investigating with relish and I thought, "What a great strategy." When teaching another concept, I repeated the strategy by asking students to predict how water would drain from a bottle if we poked a line of holes down its side. Discussion and investigation resumed but without much productive inquiry. With a second class I changed the approach by focusing on how we could determine water pressure using tools and poking holes and they went at it with abandon. I now think it's the activity, not the strategy, that made the difference. I choose activities based on content but I only repeat those that also provide an engaging experience.
Just because I taught it doesn't mean they learned it. I interviewed students before and after each unit. Though the exercise was purely for my own interest, I did get parental permission to tape the sessions for later listening. Not all of the students I interviewed showed marked changes in their thinking. I'll admit to being surprised---I still labor under the delusion that all my students will learn what I teach them. But understanding the principles of flight takes time; kids may not get it overnight, or even in five whole weeks. Listening to students was a little humbling but I highly recommend it. It has changed the way I teach.
Conceptual understanding is not a linear process. Understanding how things fly involves understanding challenging concepts. Initially I was obsessed with trying to fit these concepts into a neat, linear progression. But as if I was undoing a web, the more straight thread I pulled, the less of the pattern I had. Now I work to help students build their own contextual web of understanding. I'm also learning to be patient when I see gaps in their comprehension, realizing that I'm still revisiting and refining my own understandings. And I am continually reminding myself that understanding is a journey not a destination.
National Air and Space Museum
Washington, DC 20560
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