TOE?
I probably should have just let sleeping dogs lie, but against my better judgement, I will jump into this one... :)
The one major disappointment, but not surprising, of The Elegant Universe (both the book and the TV documentary) is the omission of the significant point of view of the Anderson-Laughlin-Pines (ALP) "axis". It appears that, at least in the documentary, the only dessenting view was presented by Sheldon Glashow (which, BTW, was one of the rumored reasons why he left Harvard for BU - that he thought most theorists at Harvard in that field have abandoned phenomenology in favor of String, Superstring, etc...)
The ALP axis (as I would like to call it) contradicts the popular views among particle/high energy physicists, championed by Steven Weinberg, that the unification of all the 4 basic forces that includes the varification of quantum gravity, signifies a "Theory of Everything" (TOE). This point of view was alluded to several times in the documentary - that getting GR and QM to mearge would mean a TOE.
ALP - who are all condensed matter theorists and who are well-known in their own rights (Anderson and Laughlin are both Nobel Laureates) - argues that what Weinberg is arguing is not a TOE for physics/universe, but a TOE for REDUCTIONISM. A grand unified theory (GUT) would only be a complete explanation of the behavior of the universe at the elementary, single-particle scale, but not does not necessary mean that we have a complete description of all the phenomena in the universe. ALP points out that there are so-called EMERGENT phenomena that can't be explained simply by knowing all the elementary interactions and by simply adding more and more interaction - i.e. this isn't simply a matter of higher complexities. As Anderson likes to say "More Is Different!"
In his Nobel speech, Laughlin described an exercise he once did onto his poor, unsuspecting students taking a graduate class in QM.[1] He gave the students a take-home exam in which he asked the students to derive superfluidity from First Principles - meaning knowing the full set of microscopic equation of motion, derive the phenomena of superfludity. Of course, the students could not, and no one can! Superfluidity, superconductivity, fractional quantum hall effect, magnetism, phase transition, etc, etc., are all "emergent" phenomena that occur as a collective effect. These phenomena disappear, as Laughlin points out, when you take the system apart and analyze each individual component within the system. These are many-body effects that simply can't be "derived" with the individual properties as the starting point.
Condensed matter physicists have long known of this, and various principles that came out of condensed matter, such as the Higgs mechanism and the principle of broken gauge symmetry, have now been adopted in various other fields of physics, including particle/high energy. However, the fact that these emergent phenomena are different and not simply just added complexities, seem to not have been heard by many camps, especially among popular views. I think it is why those who are working in the field of quantum gravity, string, etc, still may have an impression that such unification signifies a TOE. ALP have clearly pointed out why such notion may be a fallacy.[2,3] A unified theory doesn't not imply a theory of everything.
Anyway, didn't mean to throw a wrench into the whole thing, but I feel that it should be pointed out that eminent and large number of physicists do not share the same philosophical view on GUT=TOE thingy.
Zz.
[1] R.B. Laughlin, Rev. Mod. Phys. v.71, p.863 (1999).
[2] R.B. Laughlin and D. Pines, PNAS v.97, p.28 (2000) or get it at http://www.pnas.org/cgi/reprint/97/1/28.pdf .
[3] R.B. Laughlin et al., PNAS v.97, p.32 (2000) or get it at http://www.pnas.org/cgi/reprint/97/1/32.pdf .