ABSTRACT
Special relativity theory is one of the great discoveries of the Physics during the first years of the twentieth century and originated a deep impact on the way that the physical phenomena must be described for objects moving with a speed comparable with the light velocity, as is the case of particles emitted in nuclear reactions. One of the great changes introduced by this theory was that time must be considered on equal footing with respect to the spatial coordinates and combined with them, to form a frame called space time where events occur differently for observers moving with a relative velocity having a magnitude comparable with light velocity. In particular, the results of measurements of the time interval between two events are not the same for these observers and, even more, the sequence as they occur can be different if they are not causally connected.
In this chapter, we analyze the repercussions that this theory has on the predictions about the duration of events and its corresponding sequence in space time according to different inertial observers. The existence of superluminal particles, such as tachyons, gives rise to paradoxes such as those discussed at the end of this chapter.
