To detect and characterize gravitational waves from neutron star binaries, LIGO needs good models of all possible signals. Numerical relativity can’t practically be used for every case, but it is needed to test and calibrate the simpler models that LIGO can use. Inspiral waveforms from binaries with neutron stars differ from binary black hole waveforms by the presence of tidal forces. In a recent paper, Tanja Hinderer and collaborators use SXS black hole-neutron star simulations to validate a new model of these tidal forces. They find that tidal effects can be stronger than previously expected when they come close to resonance with a neutron star’s preferred ways of ringing (its normal modes of oscillation).