Noninertial Proper Motions of the Minkowski Metric, the Sagnac Effect, and the Twin Paradox

The Sagnac effect and related twin paradox with a rotating disc are analyzed. It may seem that the special theory of relativity gives an easy exhaustive treatment here. However, such consideration is deceptive since principles originally established only for inertial frames reference, whereas experiment exist in noninertial one. We introduce additional group motions to rotation uniform angular speed show these transformations leave Minkowski metric invariant. Thus, we can give firm mathematical ground usual effect. should be noted presented result true case motions; general coordinate into accelerating reference do not preserve metric.