Another example is the Sagnac effect. Two signals were sent in opposite directions around a rotating platform. After their arrival a displacement of the interference fringes occurs. Sagnac himself believed that he had proved the existence of the aether. However, special relativity can easily explain this effect. When viewed from an inertial frame of reference, it is a simple consequence of the independence of the speed of light from the speed of the source, since the receiver runs away from one beam, while it approaches the other beam. When viewed from a rotating frame, the assessment of simultaneity changes during the rotation, and consequently the speed of light is not constant in accelerated frames.