As it had already been shown [1], the continuation of reasoning applied by Hafele and Keating leads to the absurd conclusion that the Earth is not rotating around the Sun. Hafele and Keating derived a proper formula starting from false reasoning and this is the origin of the paradox. They tried to derive the formula from SRT, while the proper derivation can only be obtained from GRT [2]. There were also serious doubts concerning the experimental part of their work [4,5], but it does not matter now because today the GPS system confirms what H&K wanted to prove. Finally, H&K wanted to confirm SRT but their experiment confirmed, in fact, the GRT.
If we take a closer look at other experiments confirming SRT, we will come to the conclusion that all the experiments in fact confirm GRT similarly to the H&K experiment, because in order to compare times in two reference frames we have to disturb motion of one of the frames and this brings the problem to problems described by GRT. The pure inertial motion makes observation from two observed each other frames fully symmetrical, and we are not able to define in which of the frames the time flies slower. In this case we can draw the conclusion that the slowing of time in pure inertial motion can be only an observational effect. Only the change of speed of one of the participants transforms the observed time dilation into the real one. Therefore we can ask the questions ? are there any serious experimental evidences confirming SRT? And - if in order to register the shortening of time the change of speed is necessary ? can we assume, as it is done in SRT, that time slows down as a function of velocity.? Maybe the slowing of the time is rather a function of the change in velocity than the velocity itself?
