  Observable consequences of the hypothesis that the observed universe is a
numerical simulation performed on a cubic space-time lattice or grid are
explored. The simulation scenario is first motivated by extrapolating current
trends in computational resource requirements for lattice QCD into the future.
Using the historical development of lattice gauge theory technology as a guide,
we assume that our universe is an early numerical simulation with unimproved
Wilson fermion discretization and investigate potentially-observable
consequences. Among the observables that are considered are the muon g-2 and
the current differences between determinations of alpha, but the most stringent
bound on the inverse lattice spacing of the universe, b^(-1) >~ 10^(11) GeV, is
derived from the high-energy cut off of the cosmic ray spectrum. The numerical
simulation scenario could reveal itself in the distributions of the highest
energy cosmic rays exhibiting a degree of rotational symmetry breaking that
reflects the structure of the underlying lattice.
