Hey, not strictly homework but this is probably the best place for it, I wonder if you guys can help me out with a past paper question I've been pondering: Two events occur at the same place in an inertial reference frame S, but are separated in time by 3 seconds. In a different inertial frame S' they are separated in time by 4 seconds. (a) What is the distance between the two events·as measured in S'?  (b) What is the speed of S relative to S'?  Now, I've tried rearranging the Lorentz transformations for the reference frame velocity in order to equate them, and sub in the numbers given above, but I still have trouble because the Lorentz factor (gamma) sticks around. It wouldn't be too hard to do the second part of the question first, and get the distance from that, but I'd like to know the "proper" method.