Michelson-Gale-Pearson Experiment

The Michelson–Gale–Pearson experiment is a large-scale version of the Michelson-Morley Experiment and the Sagnac-Interferometer which attempted to measure the Sagnac Effect due to the rotation of the earth. It has been claimed that the results of this experiment is evidence for the earth's rotation.

From a work titled The Sagnac and Michelson-Gale-Pearson Experiments (Archive) by Dr. Paulo N. Correa we read on p.5:

  “ The outcome of the MGP experiment was ambiguous, though maybe no more ambiguous than the small persistent positive shift observed in MM experiments. Composed of 269 separate tests with readings that varied from -0.04 to +0.55 of a fringe, and a mean at +0.26 fringes, the MGP experiment could be interpreted to yield a positive result of ≈ 0.3 km/s - therefore near the speed of the earth's rotation, but the result was of borderline significance. It could be said that the experiment was inconclusive because it adduced neither proof that there was a shift in the phase of the light beams, nor that there wasn't one. ”

Essentially the tests saw wild results. There was almost no change to light's velocity in one test, yet a lot of change in another test. It is perplexing that the rotation of the earth would start and stop when tested at different times. Only through the statistics was it claimed that the experiment saw the rotation of the earth. As stated, the inconsistent results were ambiguous in nature and could offer no evidence of the shift in the phase of the light beams.

Other Resources

How to Lie with Statistics by Darrell Huff (Psychology Today Article)