Ask Ethan #29: The Most Famous Failed Science Experiment
So, then, the reasoning went, if light is a wave — albeit, as Maxwell demonstrated in the 1860s, an electromagnetic wave — it, too, must have a medium that it travels through. Although no one could measure this medium, it was given a name: the luminiferous aether.
Sounds like a silly idea now, doesn’t it? But it wasn’t a bad idea at all. In fact, it had all the hallmarks of a great scientific idea, because it not only built upon the science that had been established previously, but this idea made new predictions that were testable!
Ethan does a pretty thorough job of this, as usual, with the possible exception of not fully explaining that the observation of aberration was how scientists knew we couldn’t be at rest with respect to an aether — in their paper, Michelson and Morley specifically mention how their null result refutes Fresnel’s model of aberration (involving partial aether dragging and which was backed by an experiment carried out by Fizeau in 1851).
What I really object to here is the notion that this was somehow a failed experiment. The hypothesis failed, but it was not their hypothesis! While it’s quite likely that Michelson and Morley expected a result that was consistent with us moving through an aether, the more idealized view an experimentalist is supposed to take is to not expect a specific result at all, lest one become biased in gathering and interpreting data. That the experiment was clever and thorough enough to be able to refute an incorrect hypothesis means it was wildly successful, rather than a failure.