Skulls in the Stars: Lord Kelvin vs. the Aether! (1901)

[T]hese speculations resulted in a number of interesting results. For instance, we have noted previously that Earnshaw’s theorem (1839), an important result in electromagnetic theory, arose from an attempt to determine the forces that hold the aether together. In 1902, Lord Rayleigh attempted to detect the aether-induced “length contraction” by measuring the birefringence of moving objects, an ingenious attempt that gave a negative result.

In the broadest sense, a “good” theory is one which raises interesting questions that may inevitably be tested by experiment. Even if it proves to be fundamentally incorrect in the end, it has spurred numerous theoretical and experimental results.