Misconceptions

There are some lovely articles in The Astronomy Education Review about common misconceptions about cosmology and gravity. Since understanding is related to the building up of a conceptual framework, the structure that is already there is crucially important. If there are deep-seated misconceptions that go unaddressed, many of our efforts to help students construct the correct mental model are doomed to failure.

Freefall is an awesome source of misconceptions...

Gravity is a nasty one. We experience the effects of gravity, so from early childhood we construct mental models for gravity. Kathryn Williamson and Shannon Willoughby from Montana State University (one of the very best centers for astronomy education research in the US) carefully constructed a set of illuminating questions probing the concepts in gravity that natural scientists valued the highest (including the universality of gravity; that gravity depends on mass and distance alone and not things like composition, magnetism, etc; gravity can't be blocked by intervening bodies; etc.). They then obtained open-ended written feedback about these probing questions from several hundred students, analyzing the results and conducting some follow-up interviews.


Some of the most prominent misconceptions that emerged were (quotations from the article):

• Boundaries, e.g., 'the surface of a planet, the edge of the atmosphere, or even an orbit ... may represent a casing that encloses a planet’s gravity, or a “check point” where gravity either disappears or diminishes. '
• 'An unexpected misconception is that the objects that orbit a planet can act as indicators of its surface gravity. ... the “orbiting indicators” concept is generally applied in two opposing ways: (a) A planet’s gravity must be stronger to reach out and hold objects that are far away, or (b) A planet’s gravity must be stronger to pull objects close to it. '
• 'Questionnaire results overwhelmingly support the well-documented ... misconception that gravity is confounded with magnetism, rotation, and atmospheric pressure.'

Other misconceptions include that only heavy objects can interact gravitationally or that denser objects have more gravity (at the same distance from the center).

This kind of study is an incredibly valuable tool (in principle) for designing activities to counter these misconceptions, and I look forward to including it in my teaching next semester.