Doubt about relativity!! I am a noob! Forgive me if it sounds too stupid! Let me say, I am in CERN right now at the LHC. I fire a proton at 0.9c in one direction. While this happens, I also fire another proton at 0.5c in the opposite direction. Both the measurements were done considering the lab as a reference frame. The problem is, what's the speed(or velocity) of either proton relative to one another??