Sagnac effect

physics

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Last updated

July 16, 2026

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The Sagnac effect, first demonstrated in 1913 by Georges Sagnac, is a phenomenon observed with light beams traveling in opposite directions around a rotating platform. When a beam of light is split and sent around a closed loop on a rotating surface, the beam traveling in the direction of rotation returns slightly after the beam traveling against the rotation. This difference in arrival times creates an interference pattern that depends on the platform's rotation rate.1

This effect is the basis for optical gyroscopes, which have virtually no moving parts. These gyroscopes are used in applications like commercial jetliners and satellites. Modern versions, such as ring laser gyroscopes and fiber-optic gyroscopes, utilize lasers and fiber optics to detect rotation with high precision.1

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gyroscope
Optical gyroscopes
…devices are based on the Sagnac effect, first demonstrated by French scientist Georges Sagnac in 1913. In Sagnac’s demonstration, a beam of light was split such that part traveled clockwise and part counterclockwise around a rotating platform. Although both beams traveled within a closed loop, the beam traveling in the…
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…devices are based on the Sagnac effect, first demonstrated by French scientist Georges Sagnac in 1913. In Sagnac’s demonstration, a beam of light was split such that part traveled clockwise and part counterclockwise around a rotating platform. Although both beams traveled within a closed loop, the beam traveling in the…
Read More