## “The Quantum Universe” and “How to teach quantum physics to your dog”

I’ve written previously about how it can be difficult to move from the basics of a subject to the more complex aspects. Quantum mechanics is a good case in point. There are many many books that introduce the subject to a non-expert user, and just as many undergraduate and graduate textbooks that try and turn those inspired by the popular science into experts. It’s a big jump between the two. Brian Cox and Jeff Forshaw’s book, “The Quantum Universe, Everything that can Happen Does Happen” is possible an attempt to try and bridge the gap between the two. It covers many of the familiar aspects of the popular science book, but tries and to discuss this in terms of Feynman path integrals (without too much of the calculation) and attempts to give, in my view at least, a slightly different spin on the ‘weirdness’ of quantum mechanics.

The main thrust of the book has been caught up in a little bit of internet controversy (here and here, for example), in which Cox described the change in energy of an electron in a lump of diamond to be inextricably linked to the energy of every other in the Universe, and that due to the Pauli Exclusion Principle, in which no two fermions can exist in the same quantum state, if the energy of one changes, then the energy of every other electron changes in response. Everything is connected to everything else.

This goes to show you have to be very careful about how you present complex science in public, and the more famous you get the more careful you have to be. Cox seems to have oversimplified in the TV lecture, and even if correct it does seem a bit of a sales gimmick in this case, as any changes are simply t0o small to be measured. In addition there does seem to be a little bit of confusion with this idea when discussing degeneracy pressure in neutron stars in the final, fairly technical chapter.

While the book is interesting I did find it rather hard work due to the use of a ‘clocks’ analogy that is used to describe quantum interference effects, and which is used throughout the book. I didn’t find it a very intuitive analogy, and coupled with the somewhat wordy explanations, and lack of diagrams (and diagrams on pages away from the explanations dealing with them) I’m not sure I’d recommend the book to anyone other than with a desperate need to keep up to date with Brain Cox’s popular science output. The book should be applauded for the introduction of topics such as semiconductors and attempt to do a real world calculation at the end, although I’m not really sure who this is intended for.

I amy be wrong, but I don’t think Brian Cox does much in the way of undergraduate teaching. Someone who does is Chad Orzel, from Union College, who has written a much clearer explanation of quantum physics with his “How to teach quantum physics to your dog“. In this book much of the same material is covered in a much clearer and more concise fashion. It doesn’t have as much technical info as “The Quantum Universe”, but covers the material well, from the basic ideas of quantum uncertainty all the way to quantum teleportation. The hook here is that the discussion is framed as a sort of Socratic dialogue between Orzel and his Dog Emmy. Initially I thought this would just annoy me, but I got used to it quickly and it really helps the explanations to have an interjector asking sensible questions about the validity of what has just been said (always good when dealing with quantum physics!). In many ways this looks like a smart undergraduate asking the questions (although with less squirrels) and I suspect that this clarity of thought has come from extensive interactions with inquiring young minds. I really enjoyed the book, and the only weak explanation, where the technicalities prove a bit too much for many questions, was on the teleportation chapter.

There are lots and lots of books on quantum theory in the popular market place, but if I were looking to invest in one of the newer ones, then I’d plump with Orzel’s book and Emmy’s bunnies. It’s a nice refresher with good explanations, and is well suited for senior school pupils. Cox and Forshaw’s book is, I feel, trying to being a Feynman’s QED for a modern age, but comes up short with more muddled explanations. It is to be commended for trying to take on some very challenging ideas though.