The Problem of Reflection in Eighteenth-Century Projectile Theories of Light

This paper explores the mechanical models elaborated by projectile theorists throughout the eighteenth century to explain the reflection of light. Influenced by Isaac Newton’s Opticks, these projectile theorists proposed that repulsion was the cause of reflection. My purpose is to show that their models were not unified and lacked a deeper understanding of the origin of repulsive powers. This analysis illustrates how a simple optical phenomenon was not easy for eighteenth-century theorists to explain, even when the projectile theory of light was prominent among natural philosophers.