Klein's theorem and the proof of E_0 = mc~2

摘要

Despite repeated attempts, Einstein failed to give us a general and rigorous proof of his E_0=mc~2 relation. A completely general proof emerged in 1918 from a theorem on the four-vector character of energy-momentum of extended systems by the mathematician Felix Klein, but this proof is not well known, rarely seen in textbooks, and sometimes misunderstood. A simple version of this proof is presented here, with discussion of the crucial role of the energy-momentum tensor.