The joint detection of gravitational waves and electromagnetic radiation from the binary neutron star merger GW170817 established that both signals propagate at essentially the same invariant speed, while revealing a small arrival-time delay of approximately 1.7 seconds between the gravitational-wave signal and the associated gamma-ray burst. Standard interpretations attribute this delay primarily to astrophysical emission mechanisms near the source.In this work, we demonstrate that the observed delay is also naturally consistent with the MyominAung Photon-Sea Theory (MATE), in which the vacuum is treated as a structured medium characterized by frequency-dependent interactions. Within this framework, both electromagnetic and gravitational disturbances propagate at the speed of light in the high-frequency limit, but may experience slightly different effective refractive responses to the photon-sea over cosmological distances.A simple numerical estimate shows that a minute difference in effective refractive index between electromagnetic radiation and gravitational perturbations yields a cumulative propagation delay consistent with the observed 1.7-second offset for a source distance of approximately 130 million light years. The implied refractive difference remains many orders of magnitude below current experimental bounds on deviations from luminal propagation.This interpretation does not contradict General Relativity or existing constraints on the speed of gravitational waves. Instead, it provides an alternative physical perspective in which a small portion of the observed delay may arise from medium-induced propagation effects, supplementing standard astrophysical emission explanations. The result supports the broader MATE program by illustrating how multi-messenger observations can be accommodated within a medium-based description of the vacuum.
Myomin Aung (Thu,) studied this question.