Hi folks: I have a question about effective field theories. The magnetic moment of the electron calculated in renormalized QED gets it right to 12 decimal places. That suggests that QED gets things right all the way down to the order of 10^-12eV - that is, all the way to the TeV scale. But surely QED must break down at around the 100GeV mark - the scale of electroweak unification. I'm therefore confused about how it can get the magnetic moment right to all 12 places given that the theory must change so profoundly at a lower energy. Can anyone tell me where I've gone wrong? Thanks!