Learning about Gravity II. Trajectories and Orbits: A Guide for Teachers and Curriculum Developers

This is the second and final part of a review of educational research on children’s ideas about gravity. The first part concerned students’ understanding of how and why things fall. This article picks up the trail of research studies that address students’ understanding of the more complex ideas of projectile motion and orbits and examines how the recommendations of national education standards fare in light of this body of research. The article begins with a brief historical sketch of how these ideas developed in human history and a summary of the relevant Benchmarks and Standards. The review then summarizes the results of studies of children’s and adults’ ideas about projectiles and orbits. When viewed together, these studies revealed a number of common misconceptions about gravity: that gravity needs air; that there is no gravity in space; that objects in orbit are weightless, so gravity does not affect them; that the force of gravity diminishes rapidly with increasing altitude; that force is needed to keep an object in orbit; that planets closer to the Sun or that spin faster have more gravity; and that gravitational forces between objects are not equal and opposite. These misconceptions are surprisingly widespread, even among university students and teachers. The second part of the review concerns teachers and teaching. Included are studies about teachers’ awareness of their students’ misconceptions, the effectiveness of typical physics instruction, teaching interventions with students, and professional development of teachers. These studies illustrate a number of effective methods for teaching students and teachers about projectiles and orbital motion. The article ends with conclusions drawn from the research and recommendations for curriculum development and teaching. So as to avoid redundancy, this article will assume that readers have read Part I of this review, which appears in the same issue of the Astronomy Education Review