The aim of this work is to use the concept of quasi history to analyze the form of didactical presentation of the physics contents. We intend to stress the changes made to the knowledge, since the first records by the way it appears in textbooks. The content to work is the experiment of Stern-Gerlach, usually associated with the discovery of the electron spin, and which played an important role in the development of quantum theory in the twentieth century. Analyzing the original work and using some facts of history of science, we will discuss the modifications made by this content to the form in which it is presented in textbooks used in graduate courses in physics and engineering.
Stern-Gerlach experiment; electron spin; quasi-history
