Aristotelian Physics, Impetus Theory, and the Mean Speed Theorem
Overview
Prior to the seventeenth century, many of the most fundamental problems of physics concerned difficulties associated with local motion—changes in place or position. Medieval attempts to explain how and why such changes took place were developed within an Aristotelian framework. These efforts progressively undermined and eventually led to the rejection of certain tenets of Aristotle's (384-322 B.C.) doctrine of motion. They also culminated in what many consider the single most important contribution of medieval scholars to physics—the mean speed theorem.
Background
Aristotle dichotomized the universe into a terrestrial or sublunar region, encompassing Earth and extending to the sphere of the Moon, and a celestial or supralunar region, extending from the sphere of the Moon to the fixed stars. All matter in the terrestrial region was thought to be composed of four elements—earth, water, air, and fire—while the celestial region was assumed to be filled with the fifth or divine element, ether. The ether was believed to be immune to all changes except local motion. Ordinary matter was subject not only to local motion but other types of change as well.
Aristotle distinguished between two types of local motion—natural and violent.
