Planetary Motion From the Ground Up

Introductory physics is the most accessible science class taught in high school.  Sure, there are equations.  Sure, there is math.  But that’s not the point.  When it is done right, everything in a first year course can be experienced directly and easily observed.  Well, almost everything.  Planetary motion and Kepler’s Laws usually get stuck into the middle of the class as a vaguely historical and quickly brushed over link between circular motion and gravity.  This unit sets out to correct that by guiding students through the historical narrative of our understanding of the solar system through real and simulated astronomy.  The focus is on what students see and the interpretation of those observations through a historical lens.  Students will conduct their own observations and develop their own understanding through argumentation, making this unit an inquiry experience.

     This unit is designed for a high school physics course in place of the normal treatment of Kepler’s Laws and introduction to gravitation.  Students should be familiar with circular motion and forces before they begin.  As a mathematical requirement, they should have completed a course in geometry.  This topic list makes it a great fit for the AP Physics 1: Algebra Based course, because of its focus on observation, writing and argumentation.  Despite its original intent, it is accessible enough to be implemented in any high school physics or physical science course. 

     The topics addressed in this unit include, but are not limited to, Earth based astronomy, historical evaluations of competing solar systems, geometric argumentation, the development of Kepler’s Laws from observations and the development of Newton’s Law of Universal Gravitation from Kepler’s Laws.  Students will be required to make observations and turn their observations into arguments for or against competing worldviews.  They will supplement their observations with geometric arguments, the way that Galileo, Kepler and Newton did.  There is ample space for presentation, discussion and non-lab projects as well as free resources for simulations that allow students to make their own observations from both Earth-based and “bird’s eye” perspectives.