[phkahler]

Thank you. That's the first thing anyone has said that disambiguation it for me. My first thought was "but what if mass is concerned and the positive and negative mass cancel out?" But I quickly remembered the photons have the mass-equivalent energy, so the mass doesn't cancel, it gets "converted".

Is there energy in an electric field? If so it must be signed or it wouldn't cancel out.

[LegionMammal978]

> Is there energy in an electric field? If so it must be signed or it wouldn't cancel out.

The energy contained in the electromagnetic field is nonnegative: as I understand it, within a given volume, it's simply the sum of the photon energy of all of the photons.

Meanwhile, electrons and positrons exist in their own particle field, and have both positive mass energy and nonnegative kinetic energy. When an electron and positron annihilate and produce photons, they convert their combined mass energy into kinetic energy in the photons. The only thing that gets "canceled out" is the positive and negative electric charge.