Postprint version. Published in Studies In History and Philosophy of Science Part B: Studies In History and Philosophy of Modern Physics, Volume 29, Issue 2, June 1, 1998, pages 223-243.
NOTE: At the time of publication, the author Francisco Flores was not yet affiliated with Cal Poly.
The definitive version is available at https://doi.org/10.1016/S1355-2198(98)00007-0.
Einstein’s 1935 derivation of mass—energy equivalence is philosophically important because it contains both a criticism of purported demonstrations that proceed by analogy and strong motivations for the definitions of the ‘new’ dynamical quantities (viz relativistic momentum, relativistic kinetic energy and relativistic energy). In this paper, I argue that Einstein’s criticism and insights are still relevant today by showing how his derivation goes beyond Friedman’s demonstration of this result in his Foundations of Spacetime ¹heories. Along the way, I isolate three distinct physical claims associated with Einstein’s famous equation that are sometimes not clearly distinguished in philosophical discussions of spacetime theory.