Tuesday, October 03, 2006

Cool books 2b

Apropos this earlier posting, I just had a good look at another new anti-string book, Peter Woit's Not Even Wrong. Woit shows how string theory isn't even a theory, just a series of conjectures about fundamental forces and matter that have never been assembled into a coherent dynamical system, not to speak of being mathematically solved and subject to decisive tests. Thus, it's "not even wrong," since we have no way of knowing.

Woit's book is a concise telling of how fundamental physics has gone astray in the last generation. He recounts the rise of string theory from a series of obscure conjectural arguments and ideas in the 1970s, how it captured theorists' imaginations in the 1980s, and its later, strange persistence in the face of the increasingly obvious reality that it's not science. Woit winds up with the recent desperate maneuvers by string practioners. String "theory" proposes to replace quantum fields (defined at single points of space and time) with quantum extended objects: in 1-D = strings, in more dimensions = "branes," short for membranes, the 2-D analogue of strings. Without a coherent dynamics, there's nothing to solve -- the so-called "solutions" have themselves never been other than conjectures. In particular, there's no sign of a unique vacuum, or ground state (the most stable state = state of lowest energy). Without that, there's no way to make contact with observation.

The most absurd attempts to cut the Gordian knot of a mind-bogglingly large number of degenerate vacua (ground states with the same energy) appeal to the anthropic principle. (See my earlier posting too.) In a short, devastating chapter, Woit makes mincemeat of the anthropic enterprise: untestable, unprovable, science fiction, really. Either truism or empty proposition, anthropic reasoning leads to multiverses dressed up with a lot of hugger-mugger about Darwinism -- all nonsense: there's no selectional principle and, without a theory to count the various universes and assign them probabilities (no "measure," as mathematicians say), no way to know if our universe is likely or not. The anthropic principle should be banished from physics, and physicists should get back to work on stuff you can observe, test, and measure.

Many theorists defend string theory by pointing to important contributions it has made to mathematical physics. But string theory has contributed essentially nothing new. Draw up an intellectual balance sheet. String theory takes a lot from previous ideas: the Standard Model, with its trio of strong, weak, and electromagnetic forces, backed by gauge and chiral symmetries and general covariance (general relativity) -- a great, largely unsung achievement -- and speculative ideas such as supersymmetry, symmetry breaking, higher dimesions, orbifolds, and non-trivial topologies. It might be said to have contributed something to our understanding of quantum gravity, but even that is questionable. The few specific, meaty results of string theory either rely on conformal, gauge, and supersymmetric quantum field theories or make use of semi-classical arguments that any quantum theory must satisfy to agree with general relativity in the classical limit.

String theory might be best defined as a parascientific cult centered on Princeton and the guru figure of Ed Witten. Woit's book has fine thumbnail sketches of main string theorists, including an extended discussion of Witten. These are all smart, nominally sane people. How did they get sucked into this, why have they persisted for so long, and why have so many students and researchers gotten sucked in as well?

The roots of this debacle lie in the special position of high-energy physics as a science after World War II -- it received a lot of government money and intellectual prestige, accompanied by two+ generations of genuine breakthroughs, leading to the grand synthesis of the Standard Model. Unfortunately, at the highest energies, accelerators have become very expensive and take decades to build. Theory now operates in a void of evidence. Some have jokingly or angrily compared it to post-modernism in the humanities or to "faith-based" approaches like Intelligent Design. But it's really not a joke: string "theory" is not a theory at all. The most frustrating aspect is the snowjob that the string establishment has done on everyone else.

The real progress in fundamental physics today is being made through astrophysics and cosmology. Here data is pouring in from new observational platforms. Theories are being tested and slaughtered by data, leaving only a few standing. That's how real science works. It's patently false to argue, as some have, that string theory marks the "end of science." Plenty of good science is being done as I write this. It's just the end of the line for a certain type of academic theoretical physics, at least as we've known it for a generation. It's not the end of science as such.

Related thoughts from Burt Richter, emeritus director of Stanford Linear Accelerator Center.

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1 Comments:

At 3:14 PM, Blogger island said...

Either truism or empty proposition, anthropic reasoning leads to multiverses dressed up with a lot of hugger-mugger about Darwinism.

That's crap.

The anthropic principle should be banished from physics

As soon as you can come up with a stability mechanism that doesn't point directly at us.

Until then, quit trying to destroy this science that you know extremely little about, along with your anti-string crusade.

 

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