The so called modern physics is at present included in the curricula of high school. Therefore, we often organize in-depth lessons on quantum mechanics and on the special theory of relativity (SR). In the following sections, we want to show a lesson given by the first author of this paper. He proposes to students a proportion to deduce relativistic time dilation and length contraction without knowing the Lorentz transformations.

The Italian government’s Ministry of Public Education, which defines the high school curricula, has introduced almost all the topics of modern physics for students in their last year of high school. The theory of relativity is, perhaps, the argument most developed. The students, doing a web search, read that the speed of light can take different values in General Relativity (GR). We have noticed that this concept creates a lot of confusion and also a misconception in young students. In this paper, we want to describe a lecture given in the classroom about this topic.

This paper has a didactic aim. The Einstein General Theory of Relativity is very difficult for undergraduates students and also for graduates who have not followed a course of study in gravitational physics. For example, the calculation of some of its known consequences, such as the gravitational time dilation, requires familiarity with space-time metrics. In this paper, starting with the analogy between the electromagnetic field and the inertial one, we want to analyze, through the Einstein Equivalence Principle (EEP), some simple effect in a fictious gravitational field by using the inertial potentials in analogy with the electromagnetic ones.