“Nowhere is this feature made more evident than in the famous double-slit experiment. This experiment wasn’t actually performed until the 1970s, long after it was proposed. It wasn’t one of those surprising experimental results that theorists had to invent a new way of thinking in order to understand, but rather a thought experiment (suggested in its original form by Einstein during his debates with Bohr, and later popularized by Richard Feynman in his lectures to Caltech undergraduates) meant to show the dramatic implications of quantum theory.”