Uncertainty by David Lindley

One of my colleagues raves about David Lindley’s Where Does the Weirdness Go? as a basic introduction to odd quantum effects, but somehow, I’ve never managed to get around to reading any of his books until now. I recently had a need to know a bit more about the historical development of quantum theory, though, and ran across Lindley’s Uncertainty: Einstein, Heisenberg, Bohr and the Struggle for the Soul of Science in the library, which promised to contain the information I was after, so I checked it out.

As you can guess from the title, the book deals with the early development of quantum mechanics, and is particularly concerned with the philosophical issues and personalities involved in Heisenberg’s Uncertainty Principle. The early chapters dip back into the very early history of quantum theory, but it mostly deals with the period from around 1915-1940, during which the study of atoms forced physicists to complete overturn classical intuition about how the world works.

Lindley does a very good job of presenting a non-technical history of the muddled period of the “old quantum theory,” between the development of the Bohr model of hydrogen and the development of recognizably modern quantum mechanics. This is a period that most modern physics books skip over lightly, mostly because it’s such an unholy mess– the idea of discrete quantum states was fairly well accepted, but had no obvious physical basis, and people were attempting to explain atomic structure with a dizzying variety of ad hoc rules and mostly arbitrary quantum numbers. The scientific history presented here gives some sense of the confusion, without actually being confusing, which is a significant accomplishment.

Where the book really shines, though, is in presenting the personalities of the people involved in the making of the theory. Lindley includes brief character sketches of all the important players, and enough anecdotes to give a good sense of what they were like. You get the maddeningly evasive and philosophical Bohr, the standoffish Heisenberg, the prickly Max Born. There are also nice portraits of Einstein as a cranky conservative, Schrödinger the utter cad (unsurprisingly, he got on well with Einstein), and the extremely sarcastic Pauli. Pretty much anyone who’s anyone in the history of quantum theory shows up, and they all get their due.

Of course, aas you can tell from the subtitle, the book also delves into the philosophical issues surrounding the rise of quantum theory. It’s a tad melodramatic to call this a “Struggle for the Soul of Science,” but it’s not a hgue stretch.

One of the things that Lindley does a nice job of conveying is just how radical Heisenberg’s approach to quantum theory was– he was pretty much ready to discard the entire picture of commonly understood physical reality, and deal solely in observables. He wasn’t concerned with the “real” structure of atoms, just what you could measure about them– in a sense, he was the earliest proponent of the “shut up and calculate” interpretation. This was tremendously disturbing in a philosophical sense, and probably played a role in the success of Schrödinger’s wave equation over Heisenberg’s matrix mechanics.

Interestingly, though, Lindley also makes clear that the battle over the philosophy and interpretation of quantum theory was not nearly as central as some treatments make it out to be. In his description, the epic debates between Einstein and Bohr at the Solvay conferences are a bit of a side show. Most of the younger physicists at the meetings more or less ignored them, in favor of detailed discussions of what could be accomplished with the new theory. This probably had something to do with the unholy mess that is the Copenhagen Interpretation becoming the accepted picture of things– Bohr cared deeply about this stuff, where many others did not, and thus he got to define the way people thought about interpreting the theory.

Inevitably, a book dealing with uncertainty will need to deal with popular conceptions of the Uncertainty Principle, and I particularly like what Lindley has to say here:

[E]ven in physics, the uncertainty principle is by no means of ever-present relevance. The whole point of Bohr’s program of complementarity was to help physicists handle the evident fact that the real world, the world of observations and phenomena in which we live seems to be pretty solid despite the fact that underneath it all lies the peculiar indeterminacy of quantum mechanics. If Heisenberg’s principle doesn’t enter all the often into the thinking of the average physicist, how can it be important for journalism, or critical theory, or the writing of television screenplays?

We already know that people act awkwardly in front of cameras, that they don’t tell their stories to a newspaper reporter the same way they would tell them to a friend. We know that an anthropologist dropping in on some remote village culture becomes the focus of attention and has trouble seeing people behave as they normally would. We know that a poem or a piece of music doesn’t mean the same thing to all readers and listeners.

The invocation of Heisenberg’s name doesn’t make these commonplace ideas any easier to understand, for the simple reason that they’re perfectly easy to understand in the first place. What fascinates, evidently, is the semblance of a connection, and underlying commonality, between scientific and other forms of knowledge. we return, in this roundabout way, to D. H. Lawrence’s jibe about relativity and quantum theory– that he liked them precisely because they apparently blunted the hard edge of scientific objectivity and truth. We don’t have to be as intellectually philistine as Lawrence to see the attraction here. Perhaps the scientific way of knowing, in the post-Heisenberg world, is not as forbidding as it once seemed.

I have a few minor quibbles about the presentation of the science– it leans a bit too heavily on the “observing a system changes the system” view of uncertainty, which isn’t quite right– but all in all, this is an excellent book. The science is clearly described and broadly accessible, and the personalities of the physicists involved come through with impressive clarity. It’s almost compulsively readable, too– I didn’t get around to picking it up until two days before it was due back at the library, but I had no trouble finishing it in time to return it. I’ll probably buy a copy the next time I hit Borders, because there are a few sections I’d like to refer back to, and that’s great praise for a popular physics book.