Description
Fibre-optic gyroscopes (FOGs) provide a clear and accessible demonstration of relativistic physics suitable for the undergraduate laboratory. Although the rotational and propagation speeds involved are far below the speed of light, the operation of a fibre-optic gyroscope depends on the relativistic transformation of the speed of light in a moving medium. In this paper, we compare the predicted phase shift between counter-propagating beams under three models: Galilean relativity, a naïve form of special relativity, and Einstein’s theory of special relativity. We describe the construction of a low-cost fibre-optic gyroscope and present measurements of the interference power as a function of rotation rate. The data show clear disagreement with both the Galilean and naïve relativistic predictions, while exhibiting excellent quantitative agreement with the predictions of special relativity. After accounting for a small systematic correction in the fibre length, the model based on Einstein velocity addition reproduces the observed power–rotation relationship. The experiment offers a hands-on and pedagogically effective means of illustrating how even very small relativistic corrections become observable in practical interferometry.
| I am the presenting author | Yes |
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