The Concept of Weight as Reflecting the Epistemological Changes in Physics

Abstract The goal of this study was to elicit and juxtapose the account of the concept of weight in history vis a vis physics education. The results reveal the problem of consistency in the currently employed teaching materials. The weight concept is very old and remains ubiquitous in science. Its history reflects the maturation of scientific methodology. The latter implied three periods of its development: old, classical, and modern. The “old” weight designated heaviness, or gravity, of bodies and the quantity of matter, both measured through weighing by balance. The “old” weight served as the basis for trade and technology. “Old” weight split in the scientific revolution of the seventeenth century into mass and gravitational force that explained the weight of massive objects—weight was identified with gravitational force. The third period followed the scientific revolution of the twentieth century. Classical Mechanics adopted the equivalence principle and included the accelerated observers. This implied redefinition of weight by the operational definition as the result of weighing. Thus, weight was distinguished from the gravitational force. All three periods reflect the change of physics methodology. In education, physics textbooks are currently divided between the contradictory accounts of the second and third periods of weight history. The weight concept is often confused by students who show numerous related misconceptions. Facing this complexity, we argue for using weight teaching as a tool for promoting the modern perspective of knowledge construction in physics, its epistemology, that is, revealing the nature of science, the need for a reliable operational definition alongside a theoretical one, to the students. The teaching in accordance with the discipline-culture paradigm emphasizes the discursive nature of science, reveals the conceptual dialogue, and suggests its presentation in science/physics classes.