The standard model of particle physics describes the vast
majority of experiments and observations involving basic constituents of
matter. Any deviation from its predictions would be a sign of entirely
new, fundamental physics. A particularly important, long-standing
discrepancy concerns the magnetic moment of the muon. The current
measurement and theoretical calculations of this property have similar
precision, but disagree on the 3.5-4 sigma level. To transform this
disagreement into an actual discovery of new physics, an ongoing
experiment at Fermilab (USA), and one planned at J-PARC (Japan), are
aiming to reduce the measured uncertainty by a factor of four. On the
theory side, the largest part of the error comes from the hadronic vacuum
polarization contribution. Up until now, the most precise computations of
this contribution have been performed using inputs from electron-positron
annihilation experiments. Here we present a completely independent,
ab-initio computation of this term using lattice quantum field theory. We
reach a sub-percent precision similar to that of the phenomenological
approach for the first time. Surprisingly, our result leads to a standard
model prediction for the muon's magnetic moment that is in agreement with
its current experimental measurement. The upcoming Fermilab and J-PARC
experiments and our theoretical prediction are needed to either eliminate
the discrepancy or confirm it as an experimentally observable example of
physics beyond the standard model.