Simon told me this morning that he has found the answer to a question that bothered him so much lately -why photons (and gluons) violate E = mc². “It’s because photons are not real particles, they are virtual! That means that you cannot directly detect them. You need a photon to bounce off of an object to detect it. And gluons you cannot detect at all!”
Photons also don’t satisfy Eistein’s more complicated and less well-known equation about energy momentum relation: E² = (c²) + p²c², he added enthusiastically.