Sean Carroll is a well-known and respected theoretical physicist, and I am in no way qualified to review his book. I did read it, however, and I did enjoy it, in a way. What I enjoyed mostly, I think, was the thought that some very clever people probably understand it. Sadly, I can’t say I’m one of them. There are three reasons for this: I don’t have a background in quantum mechanics, I’m not especially brilliant, and I don’t think my mind is flexible enough to wrap around most of the ideas presented. None of these are the fault of the book, hence my 4-star rating. The point Dr. Carroll is making, as best I can tell, is that reality, in all its apparent wild complexity and diversity is, in fact, simply the wave function of the universe evolving in accordance with Schrödinger’s equation.
Like, duh! Why didn’t I think of that?
Just kidding. I have only a vague idea what that even means. What Dr. Carrol thinks it means (or at least what I think he thinks it means) is that truly quantum phenomena cause the universal wave function to split or branch, which results in two equally real universes where before there was only one…not that anyone notices, or can notice, or even know which one they are in…. I can understand the idea of branching. Actually, it’s what the late, great Terry Pratchett used as a premise in his books Jingo and Night Watch. (Excellent stories with cops, robbers, revolution, and a special, magical kind of physics set in a wonderfully imaginative fantasy world. I highly recommend them. But, I digress. Back to the subject at hand…) The creation of multiple worlds every time an entangled particle is seen to spin one way when it could equally have been observed to spin another seems to be a rather inefficient way of constructing a universe, but I’m willing to go along with it if it’s all backed up with a sound theory and some supporting observations. After reading this book, I’m still not sure it is. Again, probably not the fault of the book, and it makes a great premise for a good story.