Friday, December 10, 2010

Truth Decay

The empirical character of a very successful theory  always grows stale, after a time.  We may then feel (as Poincaré did with respect to Newton’s theory) that the theory is nothing but a set of implicit definitions or conventions …
-- Karl Popper, “Truth, Rationality, and the Growth of Knowledge”, repr. in Conjectures and Refutations: the Growth of Scientific Knowledge (1962; page refs. to the Harper paperback reprint), p. 240

I’m currently reading The Shape of Inner Space, by Shing-Tung Yau -- the Yau of Calabi-Yau, which lies at the heart of string theory.    Unlike Smolin’s The Trouble with Physics, let alone Woit's Not Even Wrong, the author is not out to debunk the theory in any way, especially as he was one of its mathematical progenitors:  nor to puff it, like Brian Greene, since  unlike those contentious authors, Yau is not a physicist by trade, but a pure geometer.  But towards the end of the book, he is led to exclaim: 

Given that much of string theory now hinges on compactifications of Calabi-Yau manifolds, which have these moduli with their associated massless scalar fields  and particles that don’t appear to exist, is string theory itself doomed?

And he quotes physicist Burton Richter against those quasi-nihilistic latitudinarians who have (as a recourse of despair) embraced “the landscape” (short version:  Anything Goes):

To them the reductionist voyage that has taken physics so far has come to an end.  Since that is what they believe, I can’t understand why they don’t take up something else -- macramé, for example.

There have, throughout history, been repeated instances of premature prophecying of “the End of Physics”:  but  there   the idea was that we were close to having solved everything;  never, that physics might one day become permanently stuck.


It was with these passages ringing in my mind, that I picked up Jonah Lehrer’s essay in the current issue of The New Yorker:  “The Truth Wears Off”.   I won’t summarize it -- it is brilliantly written, go read it -- but merely comment that the widespread scientific predicament there depicted -- in physics and biology and psychology and beyond -- seems even worse that the slightly softened interpretation that the author tries to present as a possible explanation or compromise.   Neither “happenstance” nor unconscious bias  can explain the range of what is supposedly going on.  E.g. the researcher who repeatedly failed to replicate his own results, not for want of trying, should  if anyone  have been prey to such bias.

[Cultural comment, to be developed if anyone’s interested:  the scientific standing of Rhine’s experiments in ESP.
-- Indeed, this just in:  ]

As Pauli wrote to Kronig in 1925:
"At the moment, physics is again terribly confused.  In any case, it is difficult for me, and I wish I had been a movie comedian or something of the sort, and had never heard of physics."
Or cosmologist Edward Harrison in 1975, saying that endless expansion "would make the whole universe meaningless.  If that were true, I would quit, and spend my life raising roses." 
There is a thread, a thought, that links these observations;  but  once again -- Wovon man nicht sprechen kann, darüber muss man schweigen.


The Shape of Inner Space is something of an intellectual autobiography, in addition to an overview of Calabi-Yau.  And quite an engagingly modest one, as these things go.   By the end of it, you have a comfortable familiarity with the author, and are full of friendly feelings.

Immediately after finishing it, I happened to re-skim George Szpiro’s equally well-written volume, Poincaré’s Prize , and was startled to see that the sinister puppet-master depicted in the chapter “The Gang of Four, Plus Two”, is none other than Shing-Tung Yau.  When I originally read the book, the name meant nothing to me; but now… it was like rounding the corner, and encountering your own cousin brandishing a knife.

Now… in the grander scheme of things, so what;  we all have our faults.  But this account of academic rivalries  gibed with my surprise at searching Shape’s index for the name of Woit or Smolin, and not finding them.  Whatever their merits or demerits, these are popular recent book-length treatments of string-theory, and one might expect that Yau would reply to them, if only to rake them over the coals.  But only towards the end of his book  does he mention theirs, in briefest passing:  and then, without uttering their names (as one might be forced to allude to Mein Kampf, but draw the line at penning the name of its author).

Yau does, however, offer a kind of reply, as he demonstrates, pretty convincingly, that String Theory, the beneficiary of much math, has in turn created, and inspired, solid math in its own right, which will survive independently of whether the particular universe of our own sojourn  happens to embody the physics.   Indeed, the fact that Ed Witten received a Fields Medal, rather than a Nobel Prize for Physics, pretty much demonstrates that.

Pauli was not alone in his lament.   Schrödinger to Bohr, 1926:
If we are going to stick to this damn quantum-jumping, then I regret that I ever had anything to do with quantum theory.

And Einstein in 1924, re the idea of renouncing strict causality:
I would rather be a cobbler, or even an employee in a gambling house, than a physicist.

This is rather a rarified kind of job-dissatisfaction.  It is as though a carpenter, towards the end of a long and successful career, were to cry out, “Had I known that wood is mere cellulose, rather than a habitation for dryads,  I would have preferred to have been anything -- a plumber or a physicist -- rather than this!”

But the phenomenon does exist.  The author in which I found those two quotes -- J. C. Polkinghorne, The Quantum World (1984), p. 53 -- after a distinguished career as a particle physicist, resigned his chair, and became a vicar in a country parish in Kent.  It was from this Father-Brown-like living that he published his popular little volume with Princeton University Press.
Similar instances could be cited, notably Alexander Grothendieck.  (Motif: “Goodbye to All That.”)

[Update Feb 2014]  A statistical reason for “truth decay”, with examples:

Most scientists would look at a P value of 0.01 and “say that there was just a 1% chance” of the result being a false alarm. “But they would be wrong.”
Rather than being convenient shorthand for significance, the P value is a specific measure developed to test whether results touted as evidence for an effect are likely to be observed if the effect is not real. It says nothing about the likelihood of the effect in the first place.

1 comment:

  1. Here's the link to Lehrer.
    Looks like you need a sub to read the whole thing, though.