From ADRIAN BOWYER
‘The mystery is deep,’ says Jim Baggott of the Einstein-Podolsky-Rosen
paradox in quantum mechanics (Review, 11 September). Quantum entities made
in pairs each carry information about the other when they zip off in opposite
directions. Measure the state of one, and you know the state of the other
even if it is light-years away. ‘Spooky action at a distance,’ said Einstein
himself.
If I write a letter, xerox it, and post the two resulting pieces of
paper to two people hundreds of miles apart, then each of them will be reading
the same thing the next morning. Further, if they both know what I’ve done,
then each knows exactly what the other is reading. This is an entirely spook-free
process.
Do the Schrodinger’s-cat letters exist before the envelopes are opened?
An absorbing question, but not one that has anything to do with physics.
The question is one for epistemology – it’s about what we choose to mean
by the verb to exist when we apply it to information. Nobody thinks that
the question ‘Would mathematics exist if there were no minds to apprehend
it?’ is for physics to answer, interesting though it is.
People love mysteries; you only have to look at how they act when some
prankster tramples flat a bit of corn in a field to see that. But physics
has enough appeal on its own, without needing to manufacture mysteries by
importing meaning-games from epistemology. The EPR ‘paradox’ has a resolution
that is as quotidian as the writing of a letter.
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Adrian Bowyer University of Bath
