to hold them down.” The students said they knew this because they had heard from the media that in space things are weightless. Indeed, they had seen pictures of astronauts just “floating” around. They had also been told that there is no air in space, and they put the two (no air and weightless) together. But they had no first-hand experiences to relate to what they knew from these external “authorities.”
If we really want to know what students are thinking, we need to ask them and then be quiet and listen respectfully to what they say. If we are genuinely interested and do not evaluate, we can learn from our students.
What good is having my students know the quantitative relation or equation for gravitational force if they lack a qualitative understanding of force and the concepts related to the nature of gravity and its effects? They should be able to separate the effects of gravity from the effects of the surrounding air. Later, they should be able to explain the phenomena of falling bodies, which requires that they separate the effects of gravity from those of air. While many physical science books focus on the constancy of gravitational acceleration, most students know that all things do not fall with the same acceleration. They know that a rock reaches the floor before a flat sheet of paper, for example. Not addressing the more common situation of objects falling differently denies the students’ common experiences and is part of the reason “school science” may not seem relevant to them. So, we need to separate the effects of air from those of gravity.
Learning is an active process. We need to acknowledge students’ attempts to make sense of their experiences and help them confront inconsistencies in their sense making.
Even more fundamental, I want my students to understand and be able to apply the concept of force as an interaction between objects in real-life situations. They should have first-hand experiences that will lead to the reasonable conclusion that force can be exerted by anything touching an object, and also that forces can exist as “actions at a distance” (i.e., without touching the object, forces might be exerted through the mechanisms of gravity, electrostatic force, and magnetic force).
I also want my students to understand the nature of scientific practice. They should be able to interpret or explain common phenomena and design simple experiments to test their ideas. In short, I want them to have the skills necessary to inquire about the world around them, to ask and answer their own questions, and to know what questions they need to ask themselves in the process of thinking about a problematic situation.