I cannot seem to figure out how to do this problem. The situation is, There are two events occuring a given time apart at the same location as seem by an observe in one frame (S). Another observer (S') sees these two events occuring at a differnent amount of time apart. I am trying to find the difference in posisitons of the two observers. I know that, x' = (x - ut) / sqrt(1 - u^2/c^2) = gamma*(x - ut) t' = (t - ux/c^2) / sqrt(1 - u^2/c^2) = gamma*(t - ux/c^2) But these two equations have too many unknowns for me. All I know are the two times for each observer and the fact that the events occur at the same spot. If I do not know the speed of the S' observer, how can I figure this out?