ABSTRACT
When Einstein applied the transformations of space and time coordinates that would preserve the laws of nature in relatively moving inertial frames (i.e. where the relative motion corresponds to constant speed in a straight line) to the laws that govern the motions of particles of matter, called ‘relativistic mechanics’, new predictions followed that were not implied by Galileo’s relativity. One of the most famous of these new predictions, that differed with the classical theory, was that when a body with mass M is at rest and not in any field of potential energy, it still has a residual energy-the ‘rest energy’, . The original derivation of this relation was quite straightforward, and it demonstrates the intimate relation between the particle aspect of matter and its continuous field aspect. The following is an outline of this derivation1.
