You are an observer fixed in absolute space watching clocks pass between two points, A and B, separated by 1km. The moving clocks are identical in every way, and have observers aboard. The Sagnac clock observer is traveling at a speed of 1km/s in a circular orbit (radius 1 billion light years), so its path between A and B appears as a straight line. And the Sagnac effect requires that the speed of light must be c+v and c-v respectively (if the Sagnac observer recorded the speed of light as c, then he would not be moving in a circle). According to Relativity the Inertial clock observer - who is traveling in a straight line at 1km/s - records the speed of light as being c. You are not told which clock will pass by, but when they pass you cannot distinguish the two apart. And both clocks follow the same straight line, as your measuring device cannot detect any error in their paths. The case against Relativity is this: It is an experimentally proven fact that the Sagnac observer measures the speed of light as c+v and c-v. Otherwise the Sagnac effect would not be observed. But according to Relativity, what appears to be an identically moving observer measures the speed of light a c. Since we cannot distinguish between the moving clock observers in this case, they must both measure the speed of light as being the same. And it is clear that Relativity is at fault and the one-way speed of light is not c, but either c+v or c-v.