Hello. Suppose there are two objects that are travelling at the speed of light, and that the observer is in an inertial frame of reference. These two objects are say, a light-second apart, and are approaching each other. From the frame of the observer, each object covers half a light-second before meeting each other. However, problems arise if a transformation is used. Since any inertial reference frame is as good as any other, it should be possible to transform the measurements from the observer's frame to that of one of the light speed frames. But then, the v^2/c^2 term in the transformation becomes one, and gamma becomes indeterminate. Because of that it becomes unclear what would happen in the c-frame. This problem arises any time you have an object travelling at light speed approaching you, even if you are not travelling at light speed yourself. For instance, if there was a train approaching a beam of light, because you don't have to deal with gamma in the train's frame, you could calculate when you would meet the light beam, but from the light beam's point of view you can't. Could this arise from the nature of travelling at c? The transformations then do not apply because from such an object's point of view, the spacetime distance is always zero. Thank you for the answers.