A little problem with special relativity. The equation for general relativity E^2= M^2c^4 + P^2c^2 is usually reduced in special relativity using the argument: If the mass is at rest, momentum is zero, therefore E^2 = 0 + M^2c^4 Therefore E = Mc2. Similarly if M is zero, E^2 = p^2c^2 + 0 And therefore E = pc The problem with this is that pc is only = to mc^2 if m is at rest. If M is in motion there is an additional kinetic energy component E= 1/2mv^2, therefore the total energy is more than pc. As a consequence I think that the intrinsic momentum, as represented by the massless photon, has to be considered separately from inertial momentum of a particle. Comments please.