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Summary: A scenario about conceptual change, where a bright student, Heather, is asked to describe the mechanisms that affect the change of the seasons.
Heather, a very bright ninth grader, is asked to explain the mechanisms causing the seasons and the phases of the moon. She has received no formal instruction on these topics in her ninth grade earth science class although these topics were covered in science lessons from earlier grades. In her explanations, Heather demonstrated some misconceptions. For example, she believed that the earth orbits the sun in a bizarre curlicue pattern and that the seasons are caused by the proximity of the earth to the sun at different points along the orbit.
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She explains that when the earth is closest to the sun at point X, it is winter in the northern hemisphere because the light rays from the sun hitting the earth are "indirect". Heather says that when the earth is at point Y, it is summer because the light rays hitting the northern hemisphere are "direct". She goes on to explain that direct rays are those that originate from the sun and travel in a straight line to the earth, and that indirect rays are rays that "bounce off" somewhere in space before reaching earth. To explain the phases of the moon, Heather explains that the shadow of the earth on the moon is the cause (Mestre, 1994).
The preceding scenario summarizes events documented in the educational video A Private Universe (Pyramid Film & Video, 1988). Heather's explanation of the seasons includes a mixture of correct and incorrect ideas. Her notion of direct and indirect light does explain, in part, why there are seasons, but her belief that the earth travels in a curlicue orbit is incorrect. Like Heather, all students enter classrooms with a wealth of knowledge about their physical, biological, and social worlds. They construct their own ideas about how the world works and explain scientific phenomena in terms of these ideas. These kinds of notions are referred to as naive beliefs, misconceptions, alternative conceptions; such preconceptions seldom match the scientific explanations that are taught in science courses.
To continue with Heather's story...
In her earth science class, Heather receives formal instruction explaining the causes of both the seasons and the phases of the moon. Two weeks after instruction begins, Heather is asked the same questions in another interview.
Instruction has helped Heather overcome several of her misconceptions. For example, Heather has revised her theory about the curlicue path of the earth around the sun. She now explains that the earth follows a nearly circular path around the sun. Furthermore, instruction has also changed Heather's belief that the seasons are caused by the proximity of the earth to the sun; she now knows that the earth is approximately the same distance from the sun throughout the year. She illustrates by drawing a diagram that the seasons are caused by the tilt in the earth's axis, which causes direct and indirect light to fall on the northern and southern hemispheres of the earth.
However, when asked to explain what she means by "direct" and "indirect" light, Heather resorts to her previous beliefs. She says that indirect light is light that bounces off points in space–similar to light reflecting off a mirror–before hitting the earth. Even a strong hint from the interviewer and a display of diagrams illustrating the differences between direct and indirect sunlight does not change Heather's mind; she incorporates the hints into her erroneous conception by saying that the indirect light from the sun, which also causes winter in the northern hemisphere, is light that bounces off some other point on the earth before reaching the northern hemisphere (Mestre, 1994).
After formal instruction, Heather has overcome some of her misconceptions. She no longer believes that the earth travels in a curlicue path around the sun. However, even with direct instruction, Heather still holds onto some of her misconceptions. She still believes that light bounces off points somewhere in space before hitting the earth. Heather seems to be relying on her earth-based observation of light bouncing off a mirror to explain the astronomically-based phenomenon of seasons. In the past, Heather's prior knowledge of the reflection of light may have facilitated learning certain concepts in physical science. In this case, however, the same prior knowledge interferes with learning.
Misconceptions are not prevalent only among school-age children. Even after several years of science instruction, adults maintain incorrect ideas about scientific phenomena. In A Private Universe, recent Harvard graduates (including some physics majors) and their professors were also asked to explain the seasons and the phases of the moon. Surprisingly, most displayed the same naive theories as Heather.
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This work is licensed by Michael Orey under a Creative Commons Attribution License (CC-BY 3.0), and is an Open Educational Resource.
Last edited by Jared Adler on Oct 12, 2011 11:37 am -0500.
