Monday, June 21, 2010

No Final Theory

I read Marcelo Gleiser’s book, A Tear at the Edge of Creation. Gleiser is a physicist who has begun to wax reflective about the methods and limits of science. His main message is that the idea of a final theory is misguided and counterproductive (Gleiser blogs at the NPR 13.7 blog; he has a recent talk online here; hat tip goes to Peter Woit’s blog).  [UPDATE: 25 June 2010:  Prof. Gleiser responds to some criticisms here.]

Gleiser thinks the search for a final theory, or “theory of everything” (TOE), could be called “monotheistic science”. The idea of the TOE is that there must be a simple powerful theory underlying the complexity of the universe; such a theory would be marked by elegant symmetries and beautiful equations. This is a search for “oneness” which suggests a parallel with what religions have at their center.

Gleiser says: “It is now time to move on. It is now time to shake free of the old imperative for perfection and embrace the lessons of a new scientific worldview that explores the creative power of Nature’s imperfections and accepts that there are limits to knowledge. (p7)” He thinks that a focus on preserving earth and life, which is a product of this complexity, should be the goal.

After a bit of autobiography and some reflections about the persistence of religious belief, Gleiser attempts to trace the history of the idea behind the final theory. The idea of finding the perfect truth or “oneness” standing behind nature was part of Greek thought, and the Pythagoreans elevated mathematical beauty to religious heights.

A couple of brief chapters on Copernicus and especially Kepler are highlights of the book. Copernicus’ great achievement was still characterized by his desire to fit things into aesthetic harmony (i.e. perfect circles for orbits). Kepler had his vision of the five platonic solids nested in spheres guiding his solar system model. He, of course, made great strides despite this misguided fantasy. Of course the reader quickly sees the paradoxical aspect of this: thinkers throughout history have been inspired to make vlauable advances via this "misguided" pursuit of elegance and perfection which themselves remained out of reach. Can we and should we denigrate the inspirational source for so much progress even if it is true that our scientific approach to truth is necessarily asymptotic?

For himself, Gleiser says when he looked at Kepler’s model, he thought: “I knew my days as a Unifier were over. (p.37)”

Then he spends several chapters tracing the asymmetries in Nature which are actually responsible for the rich phenomena we observe. The asymmetry of time; the big bang’s blow to the idea of an eternally unchanging cosmos; asymmetry in EM given the absence of magnetic monopoles; the end of the clockwork universe given QM; matter/anti-matter asymmetry and CP violation.

Turning to recent TOE efforts, Gleiser is critical of any “… physical theories that cannot be tested…(they)should not be part of the scientific canon. (p.66)” In the absence of data, TOE’s are guided by things like mathematical beauty, which we know from experience will mislead. He is concerned when looking at superstring theory that “symmetry changed from useful tool to overarching dogma (p.60)”

He notes that the empirical complications of dark matter and dark energy went unanticipated by the unifiers: in his Perimeter talk he emphasizes that surprises will likely keep coming; despite this, superstring theorists continue to operate under the assumption that what we already know won’t be discomfited by new discoveries. The idea of supersymmetry which is postulated to enhance the unification of forces in the standard model is a “…clever invention of symmetry-hungry theorists. (p.138)”

Gleiser spends a fair amount of time on the standard model, the development of grand unified theories (GUT’s), and supersymmetry. While many expect the LHC to support supersymmetry, he thinks, based on the historical record, that higher energies are more likely to reveal unanticipated new phenomena.

Gleiser thinks unification is a holy grail, an unreachable dream. While each new theory increases our knowledge, we shouldn’t ever think we’ve discovered an eternal law. Regarding laws, he says: “There are natural laws, and they reflect patterns of organized behavior. But are these laws blueprints of physical reality? Or are they logical descriptions that we create to represent it? (p.150)”

Gleiser then spends a portion of the book on the question of life, with an emphasis on the chiral asymmetry of organic molecules needed for life. He sees this as a similar problem to the cosmic and subatomic asymmetries discussed earlier.

Taken altogether, the main theme of existence seems to Gleiser to be asymmetry. This leads to a worldview of the accidental or “absurd” universe, where there is no overriding purpose, and life is fragile and rare. This is opposed to the idea of a Grand Cosmic Plan, whether supernaturalist (religious) or naturalist (unifiers). (He does discuss the increasing use of multiverses in theories, but doesn’t see how these untestable regions really change the discussion.)

To conclude, he thinks “…it is precisely our insistence in search for “unique” and “final” explanations that is delaying our progress in our true search for meaning. (p.223)” We should, rather, find meaning in the fact that life is the result of a series of accidents, hence it is fragile and precious.

I liked this book and think its perspective is important. I thought it was somewhat repetitive, however, and the theme could have been equally well expressed in a somewhat briefer essay.

With regard to the conclusions, I would say that he is certainly right to emphasize the limits of our knowledge and the need for realism about what our theories can do. I happen to agree that we most probably will not achieve a physical TOE which consists of a short set of mathematically elegant expressions. It's interesting to note that some promising quantum gravity programs now take the form of simulating the large scale behavior of a certain kind of elementary element – implying that the pursuit of precision in our theories may now be superseded by insightful views about how laws of matter and space-time geometry arise as emergent regularities.

Still, I only agree partly with Gleiser’s philosophy: I think while we can accept that perfection will remain beyond our finite grasp, it is not inappropriate that we finite creatures can and should continue to be inspired by the idea that we part of an infinite and majestic whole.

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