(Ahh, spring, when a girl's fancy turns to spring training games, where she can gawk at things like green grass, blue skies, and people wearing short sleeves. Better to think of those kinds of things than other difficult things that cannot be solved, I suppose.)
Physics is the study of how things work. It’s a discipline of facts, causality, and ideas that can be tested. Yet one piece of physics that has become part of pop culture is, surely to many physicists’ eternal annoyance, Heisenberg’s Uncertainty Principle.
Heisenberg’s idea, as has undoubtedly been bludgeoned into you all, is that you can measure a particle’s position or its velocity, but not both; measuring velocity makes position uncertain, and measuring position makes velocity uncertain. Now we shrug at this notion as a given; however, as David Lindley relates in his book Uncertainty: Einstein, Heisenberg, Bohr and the Struggle for the Soul of Science, when the idea was first introduced, it seemed to be the destruction of science.
Classical physics was based on the idea that every action was the result of a previous action; all of nature was like a machine, with each part of the machine activated by another, and each piece’s workings and role in the machine understood. If everything in nature was not yet revealed to scientists, as long as they kept the faith in this interconnectivity, they could believe that someday they would know all.
In quantum mechanics, though, there was no getting around it—things happened without apparent cause or reason. There were spontaneous actions and classical physics loathed spontaneity. If everything couldn’t be measured and predicted in some way, then what was the use of science and all their beliefs?
These were the kinds of agonies suffered by older physicists, most notably Einstein. Heisenberg and others of his generation weren’t particularly interested in deep philosophical questions about the validity of classical physics and the striving towards one, universal truth; they were more concerned about working with what they could observe and how they could use that information. As Lindley writes about Heisenberg’s view of the new mechanics: “Forget about trying to account for the behavior of electrons directly; instead express what you would like to know in terms of what you can see.”
Most of Lindley’s book is about the battle between the old-fashioned determinists and their attempt to fight back against the new world of spontaneity and probability and the quantum mechanics group who accepted it and began their own work. But Lindley also asks why these shocking ideas came about when they did. He considers the frequently proposed concept that the willingness to accept uncertainty came from a generation of German scientists that had come to adulthood during the upheaval World War I and found themselves scraping by during the unsteady Weimar Republic. Was the new inexactness a result of the same chaotic postwar world that had created avant-garde movement in the arts and led to the collapse of so many prewar social mores and restrictions? Lindley dismisses this by pointing out that contributions to quantum mechanics came from physicists from many different countries, backgrounds, and political persuasions. He has a point, but, although I don’t want to overstate the influence, I don’t think it’s wrong to consider that the times might have had something to do with that generation’s openness to a world where effects might not have any causes. Think of how different generations’ ears become tuned to new kinds of music; what seems like noise to one group is the normal perfectly logical to the next.
Lindley also spends time investigating the acceptance of the Uncertainty Principle in pop culture. Watered down to the concept, “the observer changes the observed simply by through the act of observing,” Heisenberg’s ideas have been applied to literature, art, film, music, anthropology, and everyday interactions. The popular idea is that there is no universal truth, only an individual’s truth. Again, this doesn’t really capture Heisenberg’s principle, which really is better explained by saying that there is an array of answers to a question but it’s impossible to pin an exact cause to those effects (Heisenberg originally tried to describe his discovery as “inexactness” or “indeterminacy”); it doesn’t mean that there isn’t any answer or every answer, but that is what people like about it. Throughout history there have been periods of fear that science and rationality would destroy the humanity of the world. The Uncertainty Principle, though, is almost like an antidote for that possibility—science won’t take over the world because scientists have admitted that they don’t’ have all the answers and that there are some things that are impossible to know. They are as uncertain as everyone else.
Lindley unwinds the history of physics that led up to quantum mechanics, as well as the thorny, and ultimately futile, arguments against it as clearly as he can for an audience that may be composed of scientific idiots like me. He generally is very understandable, though I could have used diagrams or visual aids in some places (then again, when don’t I? Maps, diagrams, pictures, I’m all for it. I told you, I am a scientific idiot). The personalities of the different scientists involved come through well enough, though not as elegantly as they do in Gino Segre’s Faust in Copenhagen. The book is an enjoyable little read (only about 200 pages) and a good reminder of how easily the earthshaking ideas of one era can become the commonplace of the next.