Light appears to travel at a constant velocity in a constant medium/matrix. According to Einstein, gravity is the opposing force of displaced space/time matrix by mass. The more mass, the more the gravitational displacement. Light is "bent" around massive objects. Shapiro? says there is a "time lag" of light passing around massive objects. Questions: Why did the propagation of light in a matrix theory die? Why can't the propagation matrix be the same gravitational matrix? Why can't the time lag be accounted for by the slowing of light in a denser matrix?