-discuss the role of the Michelson-Morley experiments in making determinations about competing theories
From theories come predictions that can be tested. Experiments are performed to test predictions, and from the experimental results, judgements can be made regarding the theory's validity. The MM experiment was performed to test the prediction, based on the aether model, that an aether wind should exist.
MM's failed attempt at demonstrating any existence of the aether wind, casted doubt on the aether's existence but the aether concept was well entrenched. This led scientists to modify the model rather than abandon it.
-The aether drag was such a modification (as the earth moved, it dragged aether along with it, making earth’s velocity zero relative to aether) but it was later found to be incorrect. The rejection of subsequent modifications made it even harder to accept the aether theory.
-MM's experiment made way 20 years later for Einstein's theory of Special relativity in which he explained the importance of their null result and why the aether model was not needed. Although the theory of special relativity produced its own set of predictions, not all of which were testable at that time, as technology has improved, the predictions have been tested and found to be correct.
This led to two choices for scientists as follows. They could either:
1. Continue to follow theory for which no prediction proved true (aether)
2. Follow an alternative theory for which the prediction do prove true (relativity)
and hence the aether theory and any other associated theories were subsequently abolished.
Thus, MM's experiment played a highly significant role in making determinations about competing theories and changing scientific thinking.