Michelson-Gale-Pearson experiment
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The Michelson-Gale-Pearson experiment (1925) is a modified version of the Michelson-Morley experiment and the Sagnac-Interferometer which tests the theories of special relativity and luminiferous ether along the rotating frame of Earth.
The aim was to find out whether the rotation of the Earth has an effect on the propagation of light in the vicinity of the Earth. The Michelson-Gale experiment was a very large ring interferometer, (a perimeter of 1.9 kilometer), large enough to detect the angular velocity of the Earth. Like the original Michelson-Morley experiment, the Michelson-Gale-Pearson version compared the light from a single source (carbon arc) after travelling in two directions. The major change was to replace the two "arms" of the original MM version with two rectangles, one much larger than the other. Light was sent into the rectangles, reflecting off mirrors at the corners, and returned to the starting point. Light exiting the two rectangles was compared on a screen just as the light returning from the two arms would be in a standard MM experiment.
The outcome of the experiment was that the angular velocity of the Earth as measured by astronomy was confirmed to within measuring accuracy. The ring interferometer of the Michelson-Gale experiment was not calibrated by comparison with an outside reference (which was not possible, because the setup was fixed to the Earth). From its design it could be deduced where the central interference fringe ought to be if there would be zero shift. The measured shift was 230 parts in 1000, with an accuracy of 5 parts in 1000. The predicted shift was 237 parts in 1000. According to Michelson/Gale, the experiment is compatible with both the idea of a stationary ether and special relativity. However, while the idea of stationary ether (except Lorentz's ether) contradicts the Michelson-Morley experiment, special relativity explains both experiments.
[edit] Bibliography
- The Effect of the Earth's Rotation on the Velocity of Light, by A. A. Michelson and H. G. Gale, paper here
