Bell’s brilliance and the hedonism of understanding

 

If you’re coming here from FARK.COM and wonder what this is all about, start reading two posts back “https://luysii.wordpress.com/2010/12/13/bells-inequality-entanglement-and-the-demise-of-local-reality-i/”.  You don’t have to know any physics or math to do so (but it helps, of course)

Bell did most of his work on quantum mechanics (QM) behind everyone’s back.  His day job was accelerator design and particle physics at the European center for such things (CERN).  He was no more satisfied with quantum mechanics than Einstein.  In the 60s the attitude toward the fundamentals behind QM was “Don’t Ask, Don’t Think”.  This persisted for decades and years later he made sure that anyone wanting to actually attempt an experiment testing his inequalities had a secure position before he’d encourage them.

In the 50’s David Bohm had developed a theory with hidden variables which explained the results of QM perfectly.  Unfortunately, it relied on something called a pilot wave (which you couldn’t measure).  Even worse the pilot wave was non-local affecting everything everywhere at once.  Worse than that, the great mathematician von Neumann had proved that a hidden variable was impossible (mathematically).  So Bell had the guts to decide that one of them had to be wrong, and read both papers (the very definition of Chutzpah).   For those organic chemists in your 30s, imagine that you decided that the Woodward Hoffmann rules were wrong.  Clearly, something you’d have to work on out of sight.

So Bell reads von Neumann’s proof and finds that it’s wrong.  He doesn’t like the nonlocality of Bohm’s theory either, so what to do. Follow the implications of a hidden variable theory of QM with locality.  This is how he came up with his inequalities.  To do so he had to know a good deal of QM and exactly what its predictions would be for various orientations of the polarizing beam splitters (PBSs) — see the previous two posts if you’re foggy about what PBSs do.  Not only that, but he had to conceive a type of experiment which no one at the time had any clue how to do.  A brilliant, brilliant man, and a great pleasure to finally understand what he did (thanks to Zeilinger).

You’ll have to make your own peace with the implications of entanglement, nonlocality, lack of hidden variables, etc. etc.  Bohr didn’t –” For those who are not shocked when they first come across quantum theory cannot possibly have understood it.”  Feynman didn’t — “I think I can safely say that nobody understands quantum mechanics.”.  There are a number of ways to make the world QM describes as weird as possible.  No hidden variables means that the moon isn’t there unless you look at it (measure it), or that a pretty girl isn’t pretty until you look at her. Then there is Schrodinger’s cat (see https://luysii.wordpress.com/2009/11/23/spin-hair-race-and-schrodingers-cat/).  Chemists have long known (and ignored) the fact that electrons in atoms can’t have anything like a classical trajectory.  Why?  How would any electron with a quantum number of 2 or more get past a node (where it is never found)?

After all these years, finally understanding the inequalities was really pleasant, so pleasant in fact that I began thinking about why this was. One reason of course was that I’d read a lot about it and never understood what was going on.  That’s simply getting to the top of an intellectual mountain.

More importantly, I think a lot of the pleasure comes from the completeness of the understanding.  You never understand music, literature or art anything like this.  Playing Mozart or Bach gives me great pleasure, but I’ve never felt  that I completely understood what is going on, even though there certainly is an esthetic kick to it.  I’m not sure anyone does, but if they did, would the pleasure of it be of the same kind?  The stuff that seems to most interest us, is stuff we don’t fully understand.  Interest isn’t the same as pleasure, but trying to figure music out is enjoyable. Leonard Bernstein said something to the effect that if you could capture Beethoven in words you wouldn’t need Beethoven.

Even though we understand a lot about organic chemistry, I don’t think we’re close to understanding it deeply in this sense.  Perhaps that’s why it is so fascinating.

Merry Christmas and Happy New Year to all ! ! !
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