Young's Experiment and Gravity
There are two empirical errors that have crippled Western technology. While I do count the Michelson Morley fiasco as an empirical error of the first order, the theories that it produced, relativity and quantum mechanics have merely served to perpetuate the basic two.
Nor do I count Newton's theory of gravitation because the theory, unoriginal in every aspect, merely popularized one of the basic errors and I don't count Newton's theory of colors simply because it isn't a theory. The notion that white light is made up of all colored light and that colored light is lined up the way it comes out of the spectrum is merely monkey see, monkey say science, a fact recognized by Newton's nemesis, Robert Hooke, and apparently recognized as valid by Newton, who waited out Hooke's death before pursuing vigorously his by then thirty year old notions.