Dynamical systems allow to modelize various phenomena or processes by only describing their local behaviour. The study of dynamical systems aims at knowing more on the global behaviour. Checking the reachability of a point is a fundamental problem. In this document, using results from the algebraic numbers theory such as Gelfond-Schneider's theorem, we will show that this problem that is undecidable in the general case is in fact decidable for a natural class of continuous-time dynamical systems: linear systems.