Galileo : scienza e sapienza. (Editoriale)

We describe a didactical activity in which we measure the isochronism of the small oscillations of a pendulum by means of a water clock, built by the students, inspired by Ctesibio's clock (III century b. C.). The risks of a poorly designed didactic transposition are considered: first and foremost, that of fossilising scientific notions and losing the research work that sup- ports it. In particular, the relevance of movement and doing in learning the mathematical­scientific area is considered. [Publisher's text].