When two cars travelling at 15 m s-1 approach one another, one driver observes the approach of the other as being at 30 m s-1.When two particles in an accelerator travelling at 2 x 108 m s-1 approach one another, based on the physics you have studied so far, you could reasonably infer that the relative speed would be 4 x 108 m s-1. But this is impossible.Why? The speed of light places a speed limit on the universe: 3...