Einstein developed his STR based on a hypothesis that was meant to replace the existing ether model. By introducing dogmatically the non-universal-time concept and some manipulative mathematics, he created transformation formulas that are indeed consistent, however only purely mathematically. They don’t have anything to do with reality.“The community of physics” seemingly also discovered that Einstein’s hypothesis did not replace the old ether model. In order to maintain his ”wonderful” transformation formulas, it introduced a completely different hypothesis, applied unrealistic physics and above all, just like Einstein, manipulative mathematics.This same community rejects the very simple, logical and realistic hypothesis, as formulated in this booklet, only by using the argumentation that countless experiments prove the correctness of the STR.Based on this simple hypothesis, and applying genuine mathematics, the conclusion is justified that the STR has to be rejected and thus that all measurements that are labelled as proving the correctness of the STR must have been carried out either correctly, but interpreted by wishful thinking, or carried out incorrectly.