I finished it two days ago. It's taken me 67 days of inconstancy, unfaithfulness and procrastination. Strangely, in the last two of these days I read about 30% of the book. The free time afforded by holiday-time came in handy there.
Of course it's a kind of sequel. And it doesn't merely retell the first book, In Search of Schroedinger's Cat, in the light of another decade of discovery. Rather, it just recaps briefly in a prologue. After that there's a little history, followed by some "quantum conjuring" (more on that later). In the last two chapters Gribbin really comes into his own. He's obviously far more interested in the philosophy of quantum theory than in the mechanics. As such he seems more enthusiastic, and therefore more interesting, when describing the various interpretations of quantum theory, and pointing out the flaws in each. I was most involved and responsive for this last section. And finally, in the epilogue, he proposes an answer to the question he spent the entire book asking: what is reality?
Now to do this section by section.
The recap was useful, as it must have been a good four months since I finished Schroedinger's Cat. I'm not sure how useful it would be for someone who hadn't read the first book and was unfamiliar with the concepts. Gribbin probably explained it all in his usual clear, methodical way, but I honestly don't remember, and don't wish to re-read the first 30 pages.
I enjoyed the two history chapters. I always do enjoy scientific history. Gribbin began in 500 BC with light being something that originated in the human eye, and worked his way methodically forward to the 1950s and the birth of quantum electrodynamics (QED), which explains how electrons interact by exchanging photons. QED excited me almost as much as did the original revelations in Schroedinger's Cat about complementarity and the wave function and so forth. But by this time I'd already been reading for 24 days, and the hardest part was still ahead.
This was the "quantum conjuring" used to sell the book. Let me quote you the flyleaf.
Is it true that a particle of light can be in two places at the same time? Can a single atom go two ways at once? Can time stand still? These and other paradoxes point the way to the latest ideas about the nature of reality...These "applications" are in fact discussed only in Chapter 3, and are spectactularly boring by comparison with QED and the like. Worse, much of it went straight over my head. I emerged from this chapter with relief after another 25 days or so, with a vague idea that I was on the Starship Enterprise and all around people were communicating faster than c. In actual fact I was on a train and people were commuting slower than 30 km h-1, so I fumed about public transport instead, and forgot about the Aspect experiment.
The practical applications are equally astounding, as John Gribbin describes the serious possibility that quantum theory could eventually be used to develop a Star Trek style teleportation machine, and how it has already found applications in the development of uncrackable codes.
The next two chapters were the interesting philosophical ones. Halfway through Chapter 4 I stretched out on a couch and became dead to all stimuli except for my book. I just ate it up and couldn't believe the rate at which I was reading - an average of 43 pages a day where I'd previously been doing about 3. But still, all the way through the last two chapters and the epilogue I had a problem: I couldn't see the problem.
You see, Gribbin was trying to overthrow the standard, or "Copenhagen", interpretation of quantum theory. But I'd never seen quite what was wrong with it. True, it required an almost religious belief in some rather weird ideas, but so did the other interpretations that Gribbin put forward. True, the competing "many-worlds" interpretation made more logical sense, but it had its flaws just as Copenhagen had its useful points. Why not use them both together?
As it happened that was exactly what Gribbin ended up advocating just before revealing his preferred interpretation in the epilogue: "... we are free to choose the interpretation that most suits our needs in any particular situation." This idea pleases me. It's logical, encourages free thought and exploration, takes the best of every option and removes the need for any one "solution". This "bulk-buying approach" pleased me still more after I read the epilogue, for unfortunately, I don't like the "transactional" interpretation at all.
This is Gribbin's preferred interpretation and is meant to be the single ideal "solution". He claims that it "really does take away all the mystery from quantum mysteries" and I think he may even go so far as to suggest that it should take over as the standard interpretation. But it is no more than an interpretation, not the interpretation, and as Gribbin says, its predictions are identical to those of the other interpretations. What happens remains the same; it's how we look at why it happens that is altered, and that doesn't affect the behaviour of quantum entities by one iota.
Of course I can see how "advanced waves" (which travel backwards in time) can be used to explain non-locality (signals travelling faster than light). But that raises the problem of pre-determination. The waves are called "advanced" because they are detected before the event causing them actually happens, so from the moment an advanced wave or its effects are measured or observed in any way, that event has to happen. This completely destroys the concept of human free will. Gribbin attempts some half-baked excuse for this, but it doesn't stand up. Free will is related to our thoughts, which are merely electronic impulses in our brains, carried by electrons, which are quantum entities, so must take part in this advanced wave business.
The other thing I don't like about the transactional interpretation is the apparent requirement for these waves to be generated by events which wouldn't normally cause any kind of radiation. For example, the observation of a cat in a box. This is almost as absurd as the Copenhagen notion of "probability waves". I don't know whether I've fully understood this bit, but I can't see any other way for this interpretation to solve the puzzle of Schroedinger's Cat.
However, the transactional interpretation is a good way of looking at simple events, like the exchange of a photon between two electrons. It's a good way of remembering how things are supposed to happen. So I'll keep it in mind - alongside Copenhagen and "many-worlds", not above them.
It's been a great read. These two books have actually changed my life. There's a good chance that they've fundamentally altered my future (which I hope is not pre-determined). And the ride has been so much more fun for Gribbin's familiar style. How can you not enjoy being instructed by a man who brings you in by saying things like, "I trust you are not surprised to learn this; by now, you should have been astonished only if I told you that electrons did not behave in this way"?
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