“We now know that the moon is demonstrably not there when nobody looks.”
– N. David Mermin

Last Wednesday, I was in a pub with some friends. That is to say, we are no longer colleagues, yet a good time was had by all (except for the one who got drenched in beer by the newbie waitress), so I’d say “friends” would be the appropriate classifier.

A laser pointer happened to be present, and we were playing with it, so of course the conversation turned to quantum mechanics and the Einstein-Podolsky-Rosen paradox. We remembered what the paradox was about and what it was supposed to prove, but we didn’t quite remember why it was a paradox; in other words, why the hidden variables hypothesis was not an acceptable alternative to nonlocality. So I looked it up afterwards.

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