I'm reading Eisenstaedt, The curious history of relativity: how Einstein's theory of gravity was lost and found again. In ch. 1, Eisenstaedt says that in the early 18th century, James Bradley at Oxford tried to observe parallax, failed, but detected a much larger effect, aberration, which showed up as an annual variation. Eisenstaedt's discussion isn't very clear to me, but it sounds like Bradley's observations weren't compatible with Galilean relativity. This suggests that Michelson-Morley could have been anticipated by a century, if only Bradley's observation had been interpreted correctly. Is this right? Is there a natural interpretation of Bradley's observations in the ether theory? But the ether theory post-dated Bradley by 60 years, so I guess the only contender was Newton's emission theory? http://en.wikipedia.org/wiki/James_Bradley There are also some interesting remarks about Arago getting a negative result in attempts to detect a difference in refraction of starlight from the same star at morning and evening. According to Newton, such an effect should have existed.