Quick question... does that equation refer to any type of matter, like a point particle? Or does it refer to atoms that have nuclei that are attached by the strong force? Lemme put it another way. Take a point particle, an electron... now if you found a way to convert that single electron into energy, would e=mc^2 calculate how much energy that would be? Or does e=mc^2 just refer to the energy inside an atomic nucleus aka the strong force?