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GR, Effective at Cosmological Scales?Why should we trust general relativity as the correct description of gravity at cosmological length scales? Physicists have explored alternatives to GR inspired by observations, such as accelerating expansion. These observations suggest either introducing "dark energy" or modifying GR. Here I will argue that, treating GR as an "effective field theory," in conjunction with observations at short length scales, places surprisingly strong constraints on possible gravitational theories at cosmological scales. These argument establish that, given certain assumptions, GR is the unique theory of gravity at large length scales.
Department of Philosophy