On the Electromagnetic Mass Dilemma

We show that a charged sphere moving at a constant velocity $v$ exhibits a mass due to electromagnetic radiation, expressed as $4/(3+(v/c)^2) (E/c^2)$, where $E$ is the electromagnetic energy and $c$ the speed of light in vacuum. Our finding reconciles the longstanding mismatch between the electromagnetic mass calculated from the classical electrodynamics' $4/3 (E/c^2)$ and the relativistic theory.