This review was originally posted at Goodreads and imported here later with next to no spell/grammar checking.
I wish my first introduction to Quantum Mechanics was with this book.
Most approaches focus on the utter weirdness, elevating our misled intuitions and ignorance to a mysticism. What is the nature of the observer? Why is everything a both a wave and a particle? How is the can both alive and dead at the same time? Why the divide between the quantum realm and our everyday reality? And where does human consciousness come into all this?
You hear people talk about QM with such an air of mystery, there’s no wonder charlatans like Deepak Chopra take hold in the confusion.
This book cuts right through the bullshit, focusing on what we know, why we know it, what we don’t know and what are we doing about it.
Things aren’t a particle and a wave at the same time. Everything’s waves. There’s nothing special about an observer and absolutely nothing special about consciousness (from the QM point of view). QM has almost certainly nothing to do with your thought processes (other than the driving all the underlying chemistry that is). The act of "observing" is simply an entanglement of (what we perceive as) a particle with the measuring equipment and its environment. What you decide for lunch has no fundamental effect on the shape of the universe.
It is a breath of fresh air to hear some definite answers in the field that’s commonly so muddled. And seeing how we got there. You don’t need to be versed in QM, physics or even maths to be able to follow it. It does call for an attentive reader, however. One who is willing to pause and think, maybe re-read a paragraph or two.
Moreover, Something Deeply Hidden tries to impart as much genuine understanding as is possible without dealing with complex numbers and matrix calculations. It goes right up to the maths wall, but it doesn’t cross it.
Popular explanations of scientific topics often resort to similes that seem to provide an understanding, but leave the audience confused on the underlying issues, building wrong intuitions instead of a coherent picture.
Not this book. If you get it, you’re genuinely close to really getting it and if you don’t get it, you at least know.
Quantum mechanics is a very young science, developed extremely quickly (most of the fundamentals having been laid down in the span of two decades) with twisted, colourful history full of fascinating characters. The book mostly ignores this.
As such, Adam Becker’s What Is Real? which came out earlier in the same year is a perfect companion to Sean Carroll’s Something Deeply Hidden. The former paints the historical context while the latter dives into the science.
The book begins with the outline for why we needed QM in the first place, followed by describing the wavefunction and its evolution governed by the Schrödinger equation and describing the various experiments and what they mean.
It highlights that the deepest underpinnings of the theory are not understood at all (hence the proliferation of "interpretations" of QM), outlines why that might be the case and then selects a particular approach through which to make sense of all the observations.
That explanation framework is the Hugh Everett’s or Many-Worlds theory. It highlights its stark simplicity: "The entire universe is a wave function evolving according to the Schrödinger equation. Period." It is a deterministic theory as well, nothing random or unpredictable about it.
It makes a good case that even if it doesn’t turn out to be the ultimate answer, it is the purest thing we’ve got and it serves as a very nice lens to look at the quantum behaviour through. All the other theories need to postulate more stuff: elements other than the wave function, deviations from the Schrödinger equation, etc.
It goes through ways which we might one day be able to experimentally determine one from the other (showing that these really aren’t interpretations as much as genuinely different theories with different predictions).
The common criticisms and misunderstandings are addressed in a really good chapter that’s basically a Socratic dialogue between a many-worlds sceptic and a scientist studying it.
It does highlight the other popular theories and tries to compare them with many-worlds, but it’s explicitly clear what the main focus is. That said, even if you find many worlds unpalatable, problematic or plain weird, the will leave you with a much better understanding of quantum physics.
The final section of the book focuses on the big unanswered question: what is the quantum theory of gravity? We’ve successfully quantised all the other fundamental forces. And we’ve got a really good picture of gravity in realms where it is fairly weak (i.e. the vast majority of the universe). But what’s really going on in strong gravitational fields (black holes, the big bang) is still a huge unknown.
The author goes over some interesting directions (some of which he was an active participant in) suggesting that since the traditional approach to quantising gravity has not worked out that well yet, maybe we should start looking at QM at its purest form and trying to derive spacetime and gravity that way. A bottom-up approach instead of the top-down one we’ve been doing so far.
I really liked how this seems to be the culmination of the author’s writing career to date. It tackles spacetime, geometry, entropy as well as morality in the face of our laws of physics — all topics he’d written excellent books about before.
There have been multiple cases where I was following the argument being laid out in front of me and a nagging question has arisen. Most books, these are left unanswered. Here? It was directly addressed a couple paragraphs later.
I’ve read it as an audiobook (always a risky endeavour in a scientific topic) and it was excellent. Narrated by the author himself (to whom I could listen to constantly) and really well put together. The printed book had diagrams and equations, but these were described so well that it took me a while to realise they must have been there.
Most similar audiobooks provide you with a PDF of all the pictures (if you’re lucky) and you’re supposed to have them handy while you listen. There was no need for any of that here. It stands perfectly on its own.
PS: Just like the What Is Real? it paints Albert Einstein as fiercely smart person who understand QM as well as anyone and who’s questions and criticisms cut right to the meat of the matter. He’s been instrumental in building the theory and indeed it is his work in QM (quantisation of light) that resulted in his Nobel price (not relativity as people think). Instead of losing touch (as is the popular depiction) what he lost instead was the PR battle with Niels Bohr.
I like this picture better than the popular one. Einstein was one sharp fucking cookie and this just makes so much more sense.