  General relativity may be an effective theory with higher curvature
correction terms in the action. Inclusion of these terms leads to exciting new
possibilities, e.g., gravitational and electromagnetic perturbations following
different geodesics; leading to a time delay. Such a time delay was observed
between the gravitational wave event GW170817 and its electromagnetic
counterpart GRB 170817A. We describe how this effect can be used to constrain
the coupling of the higher curvature term. Our method is sufficiently general
and applicable to any higher curvature theory.
