I’m working under a bit of a “late night Ashes watcher” fog but here goes with my first post.
I’m reading a book at the moment called “The Golem: What you should know about Science” by Henry Collins and Trevor Pinch. They tell the story of the early days of relativity, which is somewhat different to the standard story.
According to most popular science books and even undergraduate textbooks, the pre-history of special relativity goes something like this:
If light travels through a medium (the ether) then it should appear to travel faster in certain directions. Picture throwing a pebble in a flowing river. Ripples travelling with the water downstream will move quickly while ripples trying to go upstream will slow down as they fight the current. In 1887, Albert Michelson and Arthur Morley used a clever technique (I won’t go into details) to measure our speed through the ether and found … drum roll … nothing. Which is weird because the Earth rotates around its axis and orbits around the sun so there should be something. An ether wind should be blowing past us, at least at some times of the year.
All were stumped and confused (except for a couple of ad hoc ideas) until Einstein unveiled his special relativity in 1905, which postulates that light always travels at the same speed. Another win for physics!
This is all very neat and tidy, but it isn’t the whole story. As Einstein’s theory gained popularity there was a push to repeat the Michelson-Morley experiment to greater accuracy. Morley teamed up with Dayton Miller in the early 1900’s, and again found no ether wind. In the 1920’s, with the encouragement of Einstein and Lorentz, Miller repeated the experiments at an elevation of 6000 feet, just in case the earth drags the ether along somehow. In September 1924, Miller announced that he had measured an ether wind that was “real and systematic, beyond any further question.” In 1933, Miller wrote an article that argued that the evidence for an ether wind was still strong.
Now, special relativity rests on a much broader experimental basis than just the 1887 experiments of Michelson and Morley. For an excellent article, go to this article on John Baez’s outstanding site. It deals with problems with the Miller experiments as well as a host of other tests. The point, however, is that the standard story that “Michelson-Morley proves relativity” is something of a myth. The problem is not that special relativity is wrong. The problem is that the myth gives the impression that science deals with beyond-a-doubt proof rather than a messy accumulation and interpretation of evidence.