On the Sagnac Effect and the Consistency of Relativity Theory

Abstract

The Sagnac effect is an interferometric phenomenon produced by rotation. It has a rich history and presently has numerous technological applications. Despite some persistent claims to the contrary, we explain why the Sagnac effect does not prove relativity either incorrect or inconsistent. Analyzing such misunderstandings has didactic value because it allows us to review some subtle relativity concepts. It also reveals the importance of basing scientific reasoning on rigorous logical thinking to avoid confusion derived from prejudices based on our limited everyday human experience.