Gravitational-Wave Observations as a Tool for Testing Relativistic Gravity

Gravitational-wave observations can be powerful tools in the testing of relativistic theories of gravity. Future experiments should be designed to search for six different types of polarization, and for anomalies in the propagation speed of the waves: $|c_{\mathrm{grav}\mathrm{waves}}-c_{\mathrm{em}\mathrm{waves}}|\gtrsim {10}^{-7\mathrm{}}{c}_{\mathrm{em}\mathrm{waves}}$. This Letter outlines the nature and implications of such measurements.