According to quantum mechanics, it’s entirely possible that there are multiple copies of you reading multiple copies of this review. The many worlds approach to quantum mechanics says that the world decoheres into various branches. Branching reality is a difficult subject, but it is one that makes sense when interpreting exactly what quantum physics represent. Physicist, author, and podcaster, Sean Carroll attempts to explain these subtle and difficult philosophical questions in his latest book, Something Deeply Hidden, from Dutton. This is a book of big ideas explained to an audience of anyone. It doesn’t spoon feed the reader answers, but nor does it put concepts too far out of reach. For anyone interested in quantum mechanics, this is a must read.
TL;DR
From the Publisher
As you read these words, copies of you are being created.
Sean Carroll, theoretical physicist and one of this world’s most celebrated writers on science, rewrites the history of 20th century physics. Already hailed as a masterpiece, Something Deeply Hidden shows for the first time that facing up to the essential puzzle of quantum mechanics utterly transforms how we think about space and time. His reconciling of quantum mechanics with Einstein’s theory of relativity changes, well, everything.
Most physicists haven’t even recognized the uncomfortable truth: physics has been in crisis since 1927. Quantum mechanics has always had obvious gaps—which have come to be simply ignored. Science popularizers keep telling us how weird it is, how impossible it is to understand. Academics discourage students from working on the “dead end” of quantum foundations. Putting his professional reputation on the line with this audacious yet entirely reasonable book, Carroll says that the crisis can now come to an end. We just have to accept that there is more than one of us in the universe. There are many, many Sean Carrolls. Many of every one of us.
Copies of you are generated thousands of times per second. The Many Worlds Theory of quantum behavior says that every time there is a quantum event, a world splits off with everything in it the same, except in that other world the quantum event didn’t happen. Step-by-step in Carroll’s uniquely lucid way, he tackles the major objections to this otherworldly revelation until his case is inescapably established.
Rarely does a book so fully reorganize how we think about our place in the universe. We are on the threshold of a new understanding—of where we are in the cosmos, and what we are made of.
Review: Something Deeply Hidden
I’m a fan of Sean Carroll. I like his podcasts and his appearances on Joe Rogan’s podcast. He’s entertaining while still conveying complex knowledge. So, this review is biased from the start. I don’t understand quantum mechanics, and for most of my studies, I’ve been told I don’t need to understand it because the math works. It’s an odd way to approach physics. To quote Richard Feynman, “…I think I can safely say that nobody understands quantum mechanics.” Certain physicists like Sean Carroll have decided to change that. Something Deeply Hidden largely succeeds for our current best understanding. It doesn’t rely on the fact that the math works out; it attempts to explain reality, which was physics original purpose.
The book reads well; it’s not full of equations, though there are some. Dr. Carroll’s style of explanation is clear enough without equations. He’s funny and fills the book with good examples and easy to follow illustrations. Dr. Carroll lays down a foundation of quantum mechanics history before moving onto cutting edge physics and then to the weird stuff. Something Deeply Hidden is an intensely philosophical book that I’m still thinking about.
The book focuses on Schrödinger’s equation and the Everettian interpretation, which is also known as the many worlds interpretation. In short, Schrödinger’s equation describes the wave function of the universe, and there is no collapsing of the equation. Instead of superpositions collapsing into a measured reality, the measurement causes a branching of the universe. Let me repeat that a branching of the universe. One where outcome A happens and another where outcome B happens. And guess what, we branch when the universe does as well.
The Many Worlds Interpretation
Decoherence, branching, and superposition are difficult concepts to understand. Honestly, I’m not sure I grasp it fully. Dr. Carroll does a good job explaining it in a way that I could start to understand. (This is a book that I will have to reread.) The idea that the universe branches has long been a popular idea in science fiction (see the TV show Sliders). But it’s much more complex than simply a person’s decision causes the universe to split. In fact, Dr. Carroll deliberately debunks this idea. The universe branches, but an individual’s decision doesn’t cause the branching.
Dr. Carroll explains the many worlds interpretation in plain terms that at the same time make you scratch your head. In Chapter Seven, Dr. Carroll writes a short story that’s a dialogue between father and daughter physicists. In a way, it reminded me of What We Talk About When We Talk About Love by Raymond Carver. This chapter was unexpected yet effective in conveying difficult topics around probability. It was an odd chapter in a physics nonfiction book, but it helped convey the information. Something Deeply Hidden is well written.
Part Three
Multiple Me's
One consequence of branching is that when the universe decoheres and branches, so does the person. In other words, there are many copies of each of us on various branches out in the multiverse. Maybe. Dr. Carroll treats this as no big deal, and really after thinking about it for a while, it isn’t. Since we can’t interact with these other branches, contemplating the other me’s that exist is much the same as contemplating how many angels dance on the head of a pin. But I never did shake the weirdness of me branching with the universe.
This branching has direct consequences to conservation of energy and the concept of entropy. I’m not entirely convinced of the answer provided, but it’s an interesting answer. This is one of the rare moments in the book where I don’t think the answer conveys a physical meaning. Or, at the very least, one that I can understand. If the universe branches enough, does that mean it’s possible to lower the energy of the many worlds to almost zero? If so, what happens to all the me’s in those branches?
Competing Theories
Dr. Carroll states plainly that he subscribes to Hugh Everett III’s interpretation of quantum mechanics. But he does devote time to competing theories and gives them fair treatment. Then, he explains why he thinks the alternate interpretations are wrong but in respectful manner. Maybe I’ve been reading too much politics lately, but this was really refreshing. It’s important to see a thoughtful summary of and argument against a competing philosophy without a need to ‘win’ – whatever that means in physics circles.
This section also serves as a starter for investigating more about the interpretation of quantum mechanics. In this section, I learned the phrase quantum Bayesianism, which is just fun to say. Dr. Carroll’s description is quite interesting, and I might look into the topic in the future.
Conclusion
Sean Carroll’s Something Deeply Hidden broke my brain in the best way possible. This insightful, philosophical book explains difficult, complex concepts in understandable language. Based on the arguments, I’m now an Everettian convert. Somewhere out in the multiverse, there’s an Eric writing a better review of this book. In a different branch, there’s an Eric who didn’t get to read this book, and he’s all the poorer for it.
Something Deeply Hidden is available from Dutton Books on September 10, 2019