Something Deeply Hidden: Quantum Worlds and the Emergence of Spacetime

I'm late to the party, I know; the book was published almost a year ago. But I swore I wouldn't buy another book on Quantum Theory. Every author claims they will explain it, but of course they can't. All I wanted to do was understand quantum mechanics before I died, but to use an oxymoron, Carroll made it blindingly clear that wasn't going to happen. Not the dying part, the understanding part.Don't misunderstand - this is a superb book. It's well written, insightful, and entertaining. It's on the other extreme of the spectrum of useful explanations from, say Roger Penrose. Penrose is reputed to be one of the smartest living scientists, but his writing is impenetrable and should not be marketed to the general public. Maybe 100 people in the world understand him. I suspect most physicists lie and never finish his books.I knew there was a problem with quantum theory when I tossed the problem of quantum entanglement to my 9 year old grandson and he couldn't solve it. He's a really smart kid. My experience has been the drunker I get the more sense theories seem to make. Problem is, I could never get drunk enough for quantum mechanics to make sense. When I read that if the wave function of the universe simply obeys the Schrodinger equation it will undergo decoherence and branching I think to myself tell me something I don't know. No I don't. I think is this going to be on the test? Is it too late to drop the course? What sustains me is the famous Feynman quote. Don't feel bad if you don't understand quantum physics. Nobody does.But exploring the many manifestations of quantum theory with witty conversations and amusing anecdotes is not enough. String theory, the many worlds, the numerous other quantum theories Carroll explains reminds me of what Hossenfelder said in her recent book Lost in Math. Theoretical physicists are collectively delusional, unable or unwilling to recognize their unscientific procedures. As Unger and Smolin said in The Singular Universe and the Reality of Time, if a theory makes no predictions and is unfalsifyable it's no longer science. The more time that passes after the establishment of the Standard Model in the 1960's and 70's with very little progress, the more philosophical and metaphysical science seems to have become.The thing I can't get past is nonlocality. Neither could Einstein. Having remote particles instantly affect each other when one of them changes is what Einstein called spooky action at a distance. No explanation I've seen is convincing.I think some of the critiques of Carroll's book are a tad harsh. I think the problem lies with quantum physics- trying to explain it is pretty heroic. Despite my criticism, if Sean Carroll writes another book I'll probably buy it.A parting note - I would have submitted this review earlier, but towards the end of the book I was seriously injured by a collapsing wave function.

The Many-Worlds idea has proven a source of inspiration to science fiction writers and has many of us thinking about what alternative versions of ourselves might be like. But it has been taken by the general public as a fringe idea – interesting but one on the borderline between science and fiction. This book puts Many-Worlds into the center of the debate about how to interpret the results of quantum physics. Carroll’s expertise in quantum fields has been firmly established over the years and his ability to explain ideas, as he did in his superb courses for The Teaching Company, makes this the best book available to explain what the Many-Worlds hypothesis is and what it means.After laying the background in the first third of the book, Carroll uses part two to spell out the strengths and weaknesses of Many-Worlds and why he holds to it. Carroll’s approach is “materialistic” but not in the old way of meaning that word. Materialism in the old sense of everything in reality being reduced to what we can check out by our five senses is absurd in the light of quantum theory. What Carroll means is that the Many-Worlds approach ignores things like consciousness or “mental” effects in the understanding of what is happening at the quantum level. Results like the “observer effect” and entanglement can be explained by a straightforward evidence-based hypothesis that takes the wave equation of Schrödinger and the experimental processes as the foundation of the theory. To agree with Carroll we have to accept the reality of “many worlds” and Carroll goes over the problems we have with that. But Many-Worlds is in an important way the simplest explanation (in the Occam’s Razor sense) of the strange results in quantum experiments.The third part of the book explores how the Many-Worlds hypothesis ties into explaining the origin of the universe and the origin of space and time. Carroll goes over three other possible theories and discusses Hawking’s cosmological ideas. As a non-physicist I found some parts of the third section more difficult but this does not detract from the overall clear and readable writing in the bulk of the book. This book and ones like it being produced today are starts toward convincing us that understanding the quantum level by the categories of our macroscopic reality needs to be replaced by understanding our macroscopic reality by the realities of the quantum level. The foundation of it all is there. As Carroll says, everything is quantum.