Why there can be no relativity of simultaneity at the physical level: The Appendices include a circular letter to specialists in the field, as well an open letter to Lee Smolin, in which I express the hope that these ideas may open the way to developing a new conception of spacetime. The book also includes several spacetime diagrams, along with my explanations and comments. I have attempted to answer the main criticisms liable to be put forward against my objection about the spaceship and the missile. In this book, I have presented the reasons why the speed of light cannot be invariant in all possible cases in the framework of absolute simultaneity. These issues are of great importance because they are liable to result in a major change of approach to spacetime in the field of Physics. (I have previously presented the following ideas, but I have discussed them in much greater detail in my latest book, " Paradox of the invariance of the speed of light. The error of interpretation of Einstein (explanation in a few words) Relativity the special and general theory, TRANSLATED BY ROBERT W. Every reference-body (co-ordinate system) has its own particular time unless we are told the reference-body to which the statement of time refers, there is no meaning in a statement of the time of an event.> We thus arrive at the important result:Įvents which are simultaneous with reference to the embankment are not simultaneous with respect to the train, and vice versa (relativity of simultaneity). Observers who take the railway train as their reference-body must therefore come to the conclusion that the lightning flash B took place earlier than the lightning flash A. Hence the observer will see the beam of light emitted from B earlier than he will see that emitted from A. Now in reality (considered with reference to the railway embankment) he is hastening towards the beam of light coming from B, whilst he is riding on ahead of the beam of light coming from A. they would meet just where he is situated. If an observer sitting in the position M’ in the train did not possess this velocity, then he would remain permanently at M, and the light rays emitted by the flashes of lightning A and B would reach him simultaneously, i.e. Just when the flashes 1 of lightning occur, this point M' naturally coincides with the point M, but it moves towards the right in the diagram with the velocity v of the train. Let M' be the mid-point of the distance A -> B on the travelling train. But the events A and B also correspond to positions A and B on the train. The thought experiment of Einstein's train