On back-reaction in special relativity

Back-reaction of fields plays an important role in the generation of particle masses and the mass-energy equivalence of special relativity, but the most natural demonstrations using classical models result in apparent errors such as the notorious "4/3" problem. Here, we discuss the resolution of these discrepancies within the underlying atomic description of matter, with the aim of encouraging classroom discussion of back-reaction and its connection to relativistic effects. (C) 2013 American Association of Physics Teachers.