popular quantum gravity book.
She doesn't reach the heart of the problem -- that quantum gravity
is not really a scientific subject and there is no science to explain.
Lisa Randall has a surprisingly harsh review of Carlo Rovelli's popular quantum gravity book. There are comments by Woit and Motl.
The science as presented isn’t always correct, and interpretations are misleadingly presented as facts. Explaining quantum mechanics, Rovelli says: “Electrons don’t always exist. They exist when they interact. They materialize in a place when they collide with something else. The ‘quantum leaps’ from one orbit to another constitute their way of being real: An electron is a combination of leaps from one interaction to another.”Rovelli is correct that in some interpretations, electrons only exist as particles, and exhibit particle properties, when an interaction is observed. Otherwise they are some sort of wave-like field-like non-classical entities.
The real problem here is that quantum gravity is not a scientific subject, and there is no way to give a scientific explanation of it.
The core justification for the pursuit of quantum gravity is the claim that there is some incompatibility between quantum mechanics and general relativity. But the problem only exists at the center of black holes and during the first nanosecond of the big bang, and both of these are unobservable in principle. So there is no empirical data upon which to base a theory, and there is no way the theory could ever be tested.
Randall is right that Rovelli oversells his silly quantum gravity ideas, but so does everyone else who writes on the subject. Most of the ppl in the field are string theorists, and they oversell even more.
She is also right that he gets the most important number in the book wrong, even if the reader will not care. It is funny that all the theory can do is count orders of magnitude, and it has trouble even doing that correctly.
Randall herself wrote a popular book on how dark matter killed the dinosaurs, a theory that will never be proved. I guess she thinks that she did a better job of explaining the speculative nature of the hypothesis, and how empirical data might make the idea more or less plausible.