It's a radical book, an excellent book, a background which allows the reader a way into the literature, and a way to decide which things should be studied further by genuine physicists.
"As we will see, the term 'superstring theory' really refers not to a well-defined theory, but to unrealised hopes … As a result, this is a 'theory' that makes no predictions … this very lack of falsifiability is what has allowed the whole subject to flourish. … When is very speculative research part of science and when is it not?' – page 6
On pages 180-2, Peter Woit quotes various theoretical physics Nobel Laureates on superstrings:
Feynman: 'I don't like it that they're not calculating anything. I don't like [it] that they don't check their ideas. I don't like that for anything that disagrees with an experiment, they cook up an explanation – a fix up… so the fact that it might disagree with experiment is very tenuous, it doesn't produce anything…'
Glashow: 'But superstring physicists … cannot demonstrate that the standard theory is a logical outcome of string theory. They cannot even be sure that their formalism includes a description of such things as protons and electron. And they have not yet made even one teeny-tiny experimental prediction… Until string theory people can interpret perceived properties of the real world they simply are not doing physics. Should they be paid by universities and be permitted to pervert impressionable students?'
't Hooft: '… I would not even be prepared to call $tring theory a 'theory' rather a 'model' or not even that: just a hunch. After all, a theory should come together with instructions on how to deal with it to identify the things one wishes to describe … Imagine that I give you a chair, while explaining that the legs are still missing, and that the seat, back and armrest will perhaps be delivered soon; whatever I did give you, can I still call it a chair?'
Peter Woit also discusses alternatives:
'In loop quantum gravity, the basic idea is to use the standard methods of quantum theory, but to change the choice of fundamental variables that one is working with. It is well known among mathematicians that an alternative to thinking about geometry in terms of curvature fields at each point in a space is to instead think about the holonomy [whole rule] around loops in space. The idea is that in a curved space, for any path that starts out somewhere and comes back to the same point (a loop), one can imagine moving along the path while carrying a set of vectors, and always keeping the new vectors parallel to older ones as one moves along. When one gets back to where one started and compares the vectors one has been carrying with the ones at the starting point, they will in general be related by a rotational transformation. This rotational transformation is called the holonomy of the loop. It can be calculated for any loop, so the holonomy of a curved space is an assignment of rotations to all loops in the space.' – P. Woit, Not Even Wrong, Cape, London, 2006, p189.
I can see why most people currently see LQG as being even more abstract or obscure in physical detail than extra dimensional string theory.
However, the 'spin foam vacuum' description is in some ways more tangible, and corresponds with known effects. The loops have a physical correspondence to real effects going on in the vacuum, which produce features like the Casimir force. Speculation is preferred by stringers:
"How did particle physics get itself into its current state, in which some of its most prominent practitioners question whether their colleagues have given up on science? Have they? Why has there been so little progress in this subject for the last quarter-century, and where should one look for ways to change this situation? The following chapters will describe some of the history that has led particle physics to its current predicament." – page 13
[To be continued…]