The mystery of dark energy suggests that there is new gravitational physics at low energies and on long length scales. On the other hand, low mass degrees of freedom in gravity are strictly limited by observations within the solar system. A compelling way to resolve this apparent contradiction is to add a galilean-invariant scalar field to gravity. Called galileons, these scalars have strong self interactions near overdensities, like the solar system, that suppress their effects on the motion of massive particles. These non-linearities are weak on cosmological scales, permitting new physics to operate. Extending galilean invariance to the coupling of galileons to stress-energy — as was first done in the case of massive gravity — can have a surprising phenomenological consequence: enhanced gravitational lensing. Weak lensing observations will be able to detect or constrain out this effect, which is not well described by existing “model independent” tests of GR.