  Traditional derivations of general relativity from the graviton degrees of
freedom assume space-time Lorentz covariance as an axiom. In this essay, we
survey recent evidence that general relativity is the unique
spatially-covariant effective field theory of the transverse, traceless
graviton degrees of freedom. The Lorentz covariance of general relativity,
having not been assumed in our analysis, is thus plausibly interpreted as an
accidental or emergent symmetry of the gravitational sector. From this point of
view, Lorentz covariance is a necessary feature of low-energy graviton
dynamics, not a property of space-time. This result has revolutionary
implications for fundamental physics.
