But to bring us back down to Earth, think again about the experiment with two holes. In the experiment, each electron seems to “know” how many holes are open, and where it is going. Does entanglement—spooky action at a distance—come into the story here as well? If a pair of photons flying in opposite directions are, in effect, part of a single quantum system, might we regard the whole double-slit experiment and the electron—all of the electrons?—as part of a single quantum system? Maybe the electron knows which holes are open because the state of the holes is also part of the state of the
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