where 𝑚 μ is the rest mass of the muon [kg] and 𝑒 is the elementary charge [C]. A more precise value can be determined, however, via the perturbative expansion of the standard model. A theoretical value of 1.165 918 10(43) × 10 -3 (370,000 ppt relative uncertainty) results from the combined contributions of pure quantum electrodynamics, electroweak interactions, and hadronic interactions . In contrast, however, the latest experimental value of 1.165 920 59(22) × 10 -3 (190,000 ppt relative uncertainty) is in disagreement with theoretical calculations by as much as 5.2 sigma . This dramatic difference has spurred excitement for a "new physics."