It sounds like the book contains all sorts of things, including some of the material about string theory that Penrose has presented in public talks various places about “Fashion, Faith and Fantasy in Modern Physical Theories”. One version of these talks is available online from Princeton. By “Fashion” Penrose is referring to string theory, and he considers the question of why it is so fashionable. String theory has been heavily sold as “beautiful” and to some extent Penrose seems to go along with this, but his invoking of the term “fashion” indicates an awareness of how problematic notions of “beauty” can be. The latest fashionable clothes are heavily promoted for their beauty, although after a few years, when they become unfashionable, this beauty is no longer so obvious.”Beauty” is very often a social construct, with many people willing to agree that something is “beautiful” if everyone around them is saying so. Recall the story of the emperor and his fashionable outfit.
I’ve never understood these claims that string theory is “beautiful”, and was again struck by this when I got ahold of a copy of Barton Zwiebach’s new book on string theory aimed at undergraduates called A First Course in String Theory. Most of the first 270 pages of the book are devoted to working out in detail the quantization of the bosonic string in light-cone gauge, and I find it hard to believe that anyone finds this a beautiful subject. It is mathematically rather complicated and not that interesting, and has no real connection to any observable physics.
Later on in the book Zwiebach does devote a fair amount of space to trying to connect string theory to the standard model, mainly using the construction of intersecting D6 branes. At the end of this section, he acknowledges that this construction is truly hideous and looks all too much like a Ptolemaic use of epicycles on epicycles to explain planetary motion, saying “the models seem contrived, at least in the sense that they are engineered to give the physics that we observe, rather than obtained naturally as the simplest solutions of string theory”. He quotes Alfonso the Wise (1221-1284) as having said the following about Ptolemaic epicycles:
“Had I been present at the creation, I would have given some useful hints for the better ordering of the universe.”
He tries to end on a more optimistic note, hoping that some deeper meaning of string theory will emerge with more work, quoting Maimonides as follows:
“In the realm of Nature, there is nothing purposeless, trivial or unnecessary”
which begs the question of whether string theory is part of the “realm of Nature”.