1. The problem statement, all variables and given/known data Two identical particles are smashed together. They each have the same energy E. What is the energy measured for one of them by an observer in the rest system of the other? 2. Relevant equations E = γmc2 E = γ(E' + vp) 3. The attempt at a solution I've already found the speed of each particle, which is .99998C . Obviously I can't just double that since it would give me a non-real value for gamma. I know that the answer is 5 orders of magnitude greater than the energy for an individual particle.