Although Einstein apparently knew about the Michelson-Morley experiment, it's unclear how much his development of relativity depended on it. He seems to have mo

Although Einstein apparently knew about the Michelson-Morley experiment, it's unclear how much his development of relativity depended on it. He seems to have moved on to being motivated mainly by rationalist abstraction and the use of gedanken experiments, rather than actual experiments. The predictions of relativity were then confirmed by later observations and experiments. "On the role of the Michelson-Morley experiment: Einstein in Chicago" http://philsci-archive.pitt.edu/4778/1/Einstein_Chicago_Web2.pdf http://philsci-archive.pitt.edu/4778/1/Einstein_Chicago_Web2... It seems that the development of quantum mechanics has been much more driven by experimental results, although there are exceptions, such as Dirac's prediction of the positron.