Einstein's E = mc^2 mistakes
  Although Einstein's name is closely linked with the celebrated relation E = mc2 between mass and energy, a critical examination of the more than half dozen "proofs" of this relation that Einstein produced over a span of forty years reveals that all these proofs suffer from mistakes. Einstein introduced unjustified assumptions, committed fatal errors in logic, or adopted low-speed, restrictive approximations. He never succeeded in producing a valid general proof applicable to a realistic system with arbitrarily large internal and external (that is, translational) speeds. The first such general proof was produced by Max Laue in 1911 (for "closed" systems with a time-independent energy-momentum tensor) and it was generalized by Felix Klein in 1918 (for arbitrary time-dependent "closed" systems). 
Hans C. Ohanian