 Using these notational conventions, the iconic equation \(E = mc^2\) is the equation for the total energy \(E\) of a body as a function of its relativitic mass. This equation is not really of interest to us in discussing mass-energy equivalence. Furthermore, physicists today have generally given up this notational convention and deprecate the notion of “relativistic mass,” which, as Griffiths quips, “has gone the way of the two dollar bill” (1999, p. 510 fn. 8). 