In his many uses of the pendulum as a model for other motions, Galileo also described several of the properties of pendular motion. All but a small number of his apparently observational reports ring true because of his use of such qualifiers as ‘almost’. His report of observations of two lead balls on equal long strings is shown by reconstruction to have been a real experiment. His report of similar observations with balls of cork and lead is shown to be (...) an imaginary experiment. His claim that the period of a pendulum is independent of amplitude is shown to be based more on mathematical deduction than on experimental observation. (shrink)

Physics textbooks often present items of disciplinary knowledge in a sequential order of topics of the theory under instruction. Such presentation is usually univocal, that is, isolated from alternative claims and contributions regarding the subject matter in the pertinent scientific discourse. We argue that comparing and contrasting the contributions of scientists addressing similar or the same subject could not only enrich the picture of scientific enterprise, but also possess a special appealing power promoting genuine understanding of the concept considered. This (...) approach draws on the historical tradition from Plutarch in distant past and Koyré in the recent history and philosophy of science. It gains a new support in the discipline–culture structuring of the physics curriculum, seeking cultural content knowledge of the subject matter. Here, we address two prominent individuals of Italian Renaissance, Leonardo and Galileo, in their dealing with issues relevant for introductory science courses. Although both figures addressed similar subjects of scientific content, their products were essentially different. Considering this difference is educationally valuable, illustrating the meaning of what students presently learn in the content knowledge of mechanics, optics and astronomy, as well as the nature of science and scientific knowledge. (shrink)