We describe a recently introduced principle of relative locality which we propose governs a regime of quantum gravitational phenomena accessible to experimental investigation. This regime comprises phenomena in whichh and G N may be neglected, while their ratio, the Planck mass M p = h/G N , is important. We propose that M p governs the scale at which momentum space may have a curved geometry. We find that there are striking consequences for the concept of locality. The description of events in

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... spacetime now depends on the energy used to probe it. But there remains an invariant description of physics in phase space. There is furthermore a reasonable expectation that the geometry of momentum space can be measured experimentally using astrophysical observations.