Teaching planetary retrograde motion using a local positioning system

Abstract

For millennia, humans have observed planetary retrograde motion and attempted to explain the phenomena. Our modern understanding of the motions of bodies within the Solar System is built up from a rich history of past models, each of which tried to explain astronomical observations while also being influenced by the contemporary belief system. One of the pivotal observations that assisted astronomers in the development of our current planetary model is planetary retrograde motion. Complexities in heliocentric and geocentric planetary models coupled with the change of reference frame required to visualize retrograde can be challenging for students. For this reason, we developed a kinaesthetic learning activity for introductory physics and astronomy courses that requires students to physically walk planetary orbits and allows them to see apparent motions across a virtual sky in real-time. In this paper, we present multiple activities using a local positioning system that are based on changing historical models for the retrograde phenomenon. We aim for these activities to culminate in students’ holistic understanding of how astronomically observed retrograde patterns were explained by models stemming from the existing scientific knowledge and beliefs available at the time.