Albert Einstein delivering a lecture in 1934 at a meeting of the American Association for the Advancement of Science at the Carnegie Institute of Technology. (AP)
THE QUANTUM MOMENT
How Planck, Bohr, Einstein, and Heisenberg Taught Us to Love Uncertainty

By Robert P. Crease and Alfred Scharff Goldhaber

Norton. 332 pp. $29.95

THE ISLAND OF KNOWLEDGE
The Limits of Science and the Search for Meaning

By Marcelo Gleiser

Basic. 335 pp. $29.99

The human brain, that marvelous instrument we all carry around in our skulls, evolved for one purpose and one purpose only: to allow our ancestors to survive on the African savannah millions of years ago. Over the millennia, the brain got very good at its task, keeping our ancestors fed and out of the clutches of saber-toothed tigers and their ilk. Yet despite its humble origins, that same brain can understand general relativity, plot the course of distant galaxies and comprehend the working of our very cells. In fact, it is little short of miraculous that no matter where we go in the universe, no matter what new phenomena we investigate, our brain seems to be at home.

‘The Quantum Moment: How Planck, Bohr, Einstein, and Heisenberg Taught Us to Love Uncertainty’ by Robert P. Crease and Alfred Scharff Goldhaber (W. W. Norton)

With one exception.

Since the dawn of the 20th century, when scientists began exploring the inside of the atom, it has become increasingly clear that the brain is simply not designed to be comfortable with what goes on at that level. I don’t mean that we can’t calculate or control things inside the atom — cellphones, laptops and GPS systems are all fruits of our ability to deal with the subatomic realm. I mean that what goes on inside the atom isn’t like anything in our familiar world. While I can use the properties of electrons to produce these kinds of devices, I can’t draw you a picture of what an electron looks like. This is important, because we are primates whose main mode of interaction with the world is visual — we say “I see” when we mean “I understand.” There just seems to be something inherently unknowable about the basic structure of matter.

The science that developed to deal with the atom and its constituents is called quantum mechanics — “quantum” from the Latin for “heap” or “bundle,” “mechanics” for the science of motion, hence the science of motion of things that come in bundles. Quantum weirdness, I suppose, began in the 1920s when German physicist Werner Heisenberg enunciated his famous uncertainty principle. Quantum objects are different from familiar objects like billiard balls, for which we can specify a position and velocity at any point in time. In contrast, we cannot simultaneously know both the position and velocity of something like an electron. If we know exactly where that electron is, we can have no idea of how fast it’s moving and vice versa. It’s not so much that we don’t know these quantities for an electron, it’s that we can’t know them — they will remain forever what former defense secretary Donald Rumsfeld called “known unknowns.”

The uncertainty principle was followed quickly by Austrian physicist Erwin Schroedinger’s version of quantum mechanics, which implied that the only way to understand events in the quantum world was in terms of probabilities. (This, incidentally, was what caused Albert Einstein, one of the founders of quantum mechanics, to get off the quantum train.) In the ensuing years, weirdness piled on top of weirdness, and it became obvious that in probing the atom, we were entering a realm where there seemed to be real limits to what human beings could know. Two new books, “The Quantum Moment,” by Robert P. Crease and Alfred Scharff Goldhaber, and “The Island of Knowledge,” by Marcelo Gleiser, explore this and other limits to knowledge.

Each book begins with a lengthy introduction to the development of science, starting with the Greeks and running through to the quantum weirdness of modern times. “The Quantum Moment” is primarily concerned with how scientists and philosophers have dealt with the strangeness of the quantum world and how this strangeness has seeped into popular culture. The authors essentially divide modern history into two epochs. One of these they call the “Newtonian Moment,” referring to the period after the 17th century when the notion of an ordered, mechanical universe dominated our thoughts. It was a comforting vision and seemed to be profoundly in tune with our experience of nature. It was, alas, not to last, because we have now entered what the authors call the “Quantum Moment,” when we understand that the basic workings of nature at the subatomic level are not going to conform to the easily visualized constructs of the Newtonian world. After much discussion and exploration, the authors end by expressing the hope that we will someday get used to the new order of things.

In a nice touch, the book is interspersed with photographs and cartoons that illustrate how quantum ideas have entered popular culture. My favorite is a photograph of a pub called the Newton Arms, just down the road from where Isaac worked at Trinity College, Cambridge.

“The Island of Knowledge” approaches the problem of limitations to knowledge in a more general way. The title of the book refers to an interesting image. If we imagine an island of knowledge surrounded by a sea of ignorance, then every time we learn something new, two things happen: The island grows, and the boundary between knowledge and ignorance grows as well. The more we know, in other words, the more we are aware of what we don’t know.

Gleiser, a theoretical physicist, explores limits of knowledge beyond quantum mechanics — his discussions of cosmology and multiple universes are compelling. He spends a great deal of time on the issue I’m calling quantum weirdness. His basic point is that, although in principle everything is described by quantum mechanics — we are, after all, all made of atoms — the quantum effects are negligible for normal-size objects. Thus, there are two realms of knowledge, one Newtonian (for everyday life) the other quantum (for the subatomic world). Presumably there is a transition (though not necessarily a sharp one) between the two. Understanding this transition remains, at the moment, a research problem for the future.

Gleiser also gives a very nice description of a relatively new notion — quantum decoherence — that may explain how the transition between these two worlds works. The idea is that when a quantum object (such as an electron) encounters a macroscopic object (such as a detector), it bounces around like a pinball in a machine. Enough collisions, the argument goes, and the system loses its quantum properties and enters the Newtonian world.

Both books are well written and probe deep into one of the most difficult intellectual problems on the human agenda. I was particularly grateful that both avoided what Crease and Goldhaber, using a borrowed but evocative word, call “fruitloopery” — the unfortunate tendency to enlist the mysterious nature of quantum mechanics to try to explain New Age hypotheses such as extrasensory perception or reincarnation. You won’t find fruitloopery in these books, but if you are looking for a thorough and clear guide to the philosophical problems posed by the nature of the subatomic world, they are exactly what you need. In addition, both books eschew the use of equations, so readers without a scientific background can grapple directly with the strange quantum world to their hearts’ content.

James Trefil is the Clarence J. Robinson professor of physics at George Mason University and the author of “Science in World History.”

THE QUANTUM MOMENT

How Planck, Bohr, Einstein, and Heisenberg Taught Us to Love Uncertainty

By Robert P. Crease and Alfred Scharff Goldhaber

Norton. 332 pp. $29.95

THE ISLAND OF KNOWLEDGE

The Limits of Science and the Search for Meaning

By Marcelo Gleiser

Basic. 335 pp. $29.99