Review: The Quantum Universe

 The Quantum Universe is Brian Cox's introduction to quantum mechanics. Of all the books attempting to teach quantum mechanics that I've tried to read, this is the one that has the best pedagogy. Rather than follow the historical approach (introducing Heisenberg and Schrodinger's approaches first), Cox decides to use the Feynman approach right away. This allows for a geometric and diagrammatic approach to the subject that makes the initial approach relatively easy.

The approach rather than using equations with complex numbers and trigonometric functions like sine and cosine, takes advantage of the fact that you can represent complex numbers with a polar diagram. To make things easier for the layman, Cox describes these as "clocks", with magnitude represented by the size of the clock, and the hour hand (there are no minute hands in these clocks) representing the vector composed out of the real and imaginary parts. He then defines the rules for "adding" and "subtracting" clocks, and then defines how interference and cancellation of waves works. Out of all these mechanics he then gets to show how the famous double split experiment results are described correctly by this system.

From there, of course, the topic only gets harder. We extrapolate this system from photos to quarks, bosons, and Cox waves his hands and says these differ because the rules for the manipulation of clocks are different for each category. We get a walkthrough of how the standard model explains how an atom holds together, how the electrons in a hydrogen atom works, an explanation of the Pauli Exclusion Principle, and how the Higgs boson gives mass to the other particles.

Don't get me wrong. Quantum mechanics is hard. I found myself tired and falling asleep after spending an hour reading chapters of this book. I suspect the best way to approach this is to not try to read this book at bed time (though it did succeed in making me sleepy), but to do it during the day with pencil and paper handy and actually work through all the equations and diagrams he poses.

The book ends with deriving Subrahmanyan Chandrasekhar's result that a neutron star cannot be more than 1.4 times the size of the sun. This is a tour de force, involving everything you've learned so far. I will admit I couldn't follow all of it, but nevertheless I enjoyed the book.