Sagnac effect

The Sagnac effect occurs when a rotating system, like a ring or a loop, causes light beams traveling in opposite directions to take different amounts of time to complete a circuit. Imagine a circular track where one runner starts running clockwise while another runs counterclockwise. The one going against the rotation of the track takes longer to complete the lap than the one going with it. This phenomenon is used in technologies like ring laser gyroscopes, which help with navigation in aircraft and spacecraft by providing precise rotational measurements based on the time difference of light paths.