Michelson-Morley - Science proves itself wrong

I am revisiting (re-listening to) the first Great Course I heard: "Einstein's Relativity and the Quantum Revolution: Modern Physics for Non-Scientists, 2nd Edition" and I am learning even more the second time through it.  One of the recent points which impressed me again was the "Michelson-Morley Experiment."  You can follow one of the links to read about it, but here are the salient points:

In the latter part of the 19th century, scientists believed that light must be transmitted through a medium.  Since it had been shown that light (all electo-magnetism, really, but light in particular) moves as a wave, it was supposed that there must be some medium through which it traveled.  Think about the kinds of waves we usually encounter -- sound waves travel through the medium of air, ocean waves through the medium of water.  Without the medium, the wave does not exist.  Light was a wave, so it should have a medium. This medium was called "ether" (sometimes spelled "aether.")

For very good reasons which I won't get into, scientists were convinced that the Earth must be moving through the ether -- it was not at rest in the ether, as a ball floating on a still pond is at rest in the water, but more like a boat being pushed under power through water that has a current pushing against it somehow.  This meant that there must be a "wind" -- a movement of ether past the Earth that was analogous to wind.


So, convinced that the Earth was moving through the ether, Michelson and Morley designed a very clever experiment to prove this, and to attempt to measure the speed at which the Earth was moving in the ether.

Their experiment, pictured at the left, was ingenious, and became one of the most well-known experiments in history.

Because it failed.

The experiment clearly showed that the Earth was not moving, relative to the ether, and so science was faced with a (seeming) contradiction.  It was proven that the Earth was not at rest with respect to the ether, and it was also proven that the Earth was not in motion with respect to the ether.  How could this be?

Einstein would give the answer with his theory of special relativity in 1905, and one of the results would be the (now obvious) answer: there is no such thing as "ether" - no "medium" which transmits electro-magnetic waves such as light.

This is such a great example of how scientists work.  They build experiments which are influenced by their beliefs/knowledge.  After all, Michelson and Morley were convinced that they would find the ether wind.  They were "biased" in the sense that they expected something, so they built an experiment based on their beliefs. But scientists also publish their results, even when those results do not support the current the theories.  By doing so, they put the scientific world to work trying to reconcile the results with science's view of reality, and science moves forward.

No scientist ever gets "the final answer" because no theory has yet explained everything.  But throughout history, science has gotten closer and closer to being able to describe more and more of reality by constantly looking for contradictions, anomalies and points of divergence and trying to find theories which explain them all -- or at least more than the theories which are known at the time.

It's a darn good thing Michelson and Morley were willing to show that they were wrong.  Great scientists.