Mass-energy equivalence
= Mass-energy equivalence
{title2=$E_0=mc^2$}
The rest energy of a body is $E_0=mc^2$. A body emitting energy $dE$ and no net momentum in its rest frame loses mass $dE/c^2$. For a radiating source of luminosity $L$, the corresponding radiative mass-loss rate is $L/c^2$.