The Sagnac Effect

Farhad Hakimi

The story of an experiment that might have kept Einstein awake at night—but that paved the way for the dawn of optical gyroscopes and that could enable future gravitational-wave detectors.

A team led by the Technological University Munich recently used the Sagnac-effect-enabled ring-laser interferometer G at the Geodetic Observatory Wettzell to measure Earth’s rotation with unprecedented precision. [A. Eckert / TUM]

More than a century ago, George Sagnac —an ardent advocate of the concept of “absolute space”—challenged Einstein’s theory of special relativity, employing data from his meticulously crafted loop interferometer to scrutinize and question Einstein’s ideas. Einstein remained silent in response, and ironically, as subsequent events unfolded, Sagnac’s interferometer itself eventually proved a testament to the validity of Einstein’s theories.

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