The energy of an electron at rest is mc^2. 1) Can an electron even be at rest? It seems that the answer is "no" by the uncertainty principle. Thus, it would seem that every electron has energy greater than mc^2. Is this a correct statement? 2) Is this a classical quantity? That is, if I were to determine the electric and magnetic fields of an electron quatum mechanically, and if I integrated the square of the electric field to determine the total energy stored in those fields, would I get E = mc^2 as an answer. Basically, I am wondering which (if any) of these statements is true. E = E_rest + E_fields E = E_rest = E_fields Can we say: An electron has no energy---rather, it's fields due. Anyway, this wasn't super organized, but I hope my question is clear. I am trying to resolve (if it needs to be) E = mc^2 with quantum mechanics and I don't understand how the energy of a particle relates to the field that it creates.