ABSTRACT
In addition to the usual problem of the formal operations needed to establish the table of possibilities that allows the discovery and verification of a law, the present research raises a question about the formal operational schema relative to proportionality. But we are dealing with a new type of proportionality. Whereas the proportions in the problems of the balance and of hauling a weight on an inclined plane derive from a model of physical equilibrium, the proportions we shall study in connection with the projection of shadows are of an essentially geometrical nature. They denote relationships between distances and diameters in a physical phenomenon that can be explained in terms of simple projective geometry.
