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Thursday, March 27, 2014

Mermin resolves metaphysical issues in Nature

I posted before on Mermin taking Bohr seriously, SciAm pushes Quantum Bayesianism, and Counterfactuals: Time on the metaphysics of time. Now Cornell Physicist N. David Mermin has an essay in the current Nature journal:
Schrödinger wrote in a little-known 1931 letter2 to German physicist Arnold Sommerfeld that quantum mechanics “deals only with the object–subject relation”. Another founder of quantum mechanics, Danish physicist Niels Bohr, insisted in a 1929 essay3 that the purpose of science was not to reveal “the real essence of the phenomena” but only to find “relations between the manifold aspects of our experience”. ...

People who believe wavefunctions to be as real as stones have invested much effort in searching for objective physical mechanisms responsible for such changes in the wavefunction: ...

Another celebrated part of the muddle produced by the exclusion of the perceiving subject is 'quantum non-locality', the belief of some quantum physicists and many mystics, parapsychologists and journalists that an action in one region of space can instantly alter the real state of affairs in a faraway region. Thousands of papers have been written about this mysterious action at a distance over the past 50 years. A clue that the only change is in the expectations of the perceiving subject7 is that to learn anything about such alterations one must consult somebody in the region where the action took place. ...

The issue for Einstein was not the famous revelation of relativity that whether or not two events in two different places happen at the same time can depend on your frame of reference. It was simply that physics seems to offer no way to identify the Now even at a single event in a single place, although a local present moment — Now — is evident to each and every one of us as undeniably real. How can there be no place in physics for something as obvious as that? ...

When I recently mentioned to an eminent theoretical physicist that I was writing an essay explaining how the QBist view of science solves the strictly classical problem of the Now, he said: “Ah, you're going to explain why we all have that illusion.” And a distinguished philosopher of science recently derided the attitude that there ought to be a Now on my world-line as “chauvinism of the present moment”9.
My only quarrel with Mermin is that he acts as if he is saying something new. He is just reciting the view of Bohr and everyone else not infected with Einstein's disease.

There are physicists and philosophers today who (1) believe wavefunctions to be as real as stones; (2) assert quantum non-locality; and (3) deny Now as just chauvinism of the present moment. They have bizarre and foolish philosophies that lead to unresolvable paradoxes. Mermin's common sense explanations from a century ago are perfectly adequate.

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