There are no clues in the available scientific data about how these problems might be solved, and theorists have been obliged to speculate. But, in Farewell to Reality, I argue that in their ambition to develop a "theory of everything", some theorists have crossed a line. The resulting theories, such as superstring theory (or M-theory), are not grounded in empirical data and produce no real predictions, so they can't be tested. Albert Einstein once warned: "Time and again the passion for understanding has led to the illusion that man is able to comprehend the objective world rationally by pure thought without any empirical foundations – in short, by metaphysics." Now, metaphysics is not science. Yet a string of recent bestselling popular science books, supported by press articles, radio and television documentaries, have helped to create the impression that this is all accepted scientific fact. Physics has gone too far.Duff replies with phony history lessons:
Quantum theory, for example, was largely driven by empirical results, whereas Einstein's general theory of relativity was more a product of speculation and thought experiments (contrary to what your quote implies). Speculation, then, is a vital part of the scientific process. When Paul Dirac wrote down his equation describing how quantum particles behave he wasn't just explaining the electron, whose properties had been well established in experiments. His equation also predicted the hitherto undreamed-of positron, and hence the whole concept of antimatter.Quantum theory was driven by data, but so was relativity and Dirac's theory. Poincare first conceived relativistic gravity in order to understand the finite propagation of gravity and the precession of Mercury's orbit.
Duff also says:
It is a common fallacy that physics is only about what has already been confirmed in experiments. The Higgs boson had no foundation in empirical reality when it was predicted in 1964. ...The Higgs mechanism was proposed as a way of explaining the short-range nature of nuclear forces. Yes, the particle was only found 50 years later.
Theories rarely spring fully formed from the minds of their discoverers. Chapter 2 of your book reminds us that it took 30 years of quantum entanglement (Einstein's "spooky action at a distance", proposed in 1935) before John Bell made a falsifiable prediction and another 20 before Alain Aspect tested it experimentally. Was all the entanglement research done in the meantime, including Einstein's, unscientific metaphysics? I don't think so.
Einstein's quantum work was unscientific metaphysics. Einstein and Bell were trying to prove quantum mechanics wrong by showing some supposedly counter-intuitive aspects of it. If they had turned out to be right, and they had inspired someone to disprove quantum mechanics wrong, then I guess I would have had to admit that they were onto something. But it is clear now that they were barking up the wrong tree. It was also the opinion of the leading physicists at the time of Einstein and Bell that they were barking up the wrong tree.
Baggott is right that theoretical physics has become Fairy Tale Physics, as explained in this podcast or my book.