Of course, such an experiment has never been carried out for path-lengths of the order of a light-year, but the stated result is not seriously doubted (by conventional quantum physicists!). Experiments of this very type have actually been carried out with path-lengths of many metres or so, and the results are indeed in complete agreement with the quantum-mechanical predictions (cf. Wheeler 1983). What does this tell us about the reality of the photon’s state of existence between its first and last encounter with a half-reflecting mirror? It seems inescapable that the photon must, in some
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