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Chapter 1: The Socks

1978 & 1981

In 1978, when John Bell first met Reinhold Bertlmann, at the weekly tea party at the Organisation Européenne pour la Recherche Nucléaire, near Geneva, he could not know that the thin young Austrian, smiling at him through a short black beard, was wearing mismatched socks. And Bertlmann did not notice the characteristically logical extension of Bell’s vegetarianism—plastic shoes.

Deep under the ground beneath these two pairs of maverick feet, ever-increasing magnetic fields were accelerating protons (pieces of the tiny center of the atom) around and around a doughnut-shaped track a quarter of a kilometer in diameter. Studying these particles was part of the daily work of CERN, as the organization was called (a tangled history left the acronym no longer correlated with the name). In the early 1950s, at the age of twenty-five, Bell had acted as consultant to the team that designed this subterranean accelerator, christened in scientific pseudo-Greek “the Proton Synchrotron.” In 1960, the Irish physicist returned to Switzerland to live, with his Scottish wife, Mary, also a physicist and a designer of accelorators. CERN’s charmless, colorless campus of box-shaped buildings with protons flying through their foundations became Bell’s intellectual home for the rest of his life, in the green pastureland between Geneva and the mountains. At such a huge and impersonal place, Bell believed, newcomers should be welcomed. He had never seen Bertlmann before, and so he walked up to him and said, his brogue still clear despite almost two decades in Geneva: “I’m John Bell.”

This was a familiar name to Bertlmann—familiar, in fact, to almost anyone who studied the high-speed crashes and collisions taking place under Bell’s and Bertlmann’s feet (in other words, the disciplines known as particle physics and quantum field theory). Bell had spent the last quarter of a century conducting piercing investigations into these flying, decaying, and shattering particles. Like Sherlock Holmes, he focused on details others ignored and was wont to make startlingly clear and unexpected assessments. “He did not like to take commonly held views for granted but tended to ask, ‘How do you know?,’ ” said his professor, Sir Rudolf Peierls, a great physicist of the previous generation. “John always stood out through his ability to penetrate to the bottom of any argument,” an early co-?worker remembered, “and to find the flaws in it by very simple reasoning.” His papers—numbering over one hundred by 1978—were an inventory of such questions answered, and flaws or treasures discovered as a result.

Bertlmann already knew this, and that Bell was a theorist with an almost quaint sense of responsibility who shied away from grand speculations and rooted himself in what was directly related to experiments at CERN. Yet it was this same responsibility that would not let him ignore what he called a “rottenness” or a “dirtiness” in the foundations of quantum mechanics, the theory with which they all worked. Probing the weak points of these foundations—the places in the plumbing where the theory was, as he put it, “unprofessional”—occupied Bell’s free time. Had those in the lab known of this hobby, almost none of them would have approved. But on a sabbatical in California in 1964, six thousand miles from his responsibilities at CERN, Bell had made a fascinating discovery down there in the plumbing of the theory.

Revealed in that extraordinary paper of 1964, Bell’s theorem showed that the world of quantum mechanics—the base upon which the world we see is built—is composed of entities which are either, in the jargon of physics, not locally causal, not fully separable, or even not real unless observed.

If the entities of the quantum world are not locally causal, then an action like measuring a particle can have instantaneous “spooky” effects across the universe. As for separability: “Without such an assumption of the mutually independent existence (the ‘being-?thus’) of spatially distant things…,” Einstein insisted, “physical thought in the sense familiar to us would not be possible. Nor does one see how physical laws could be formulated and tested without such a clean separation.” The most extreme version of nonseparability is the idea that the quantum entities are not independently real: that atoms do not become solid until they are observed, like the proverbial tree that makes no sound when it falls unless a listener is around. Einstein found the implications ludicrous: “Do you really believe the moon is not there if nobody looks?”

Up to that point, the idea of science rested on separability, as Einstein had said. It could be summarized as humankind’s long intellectual journey away from magic (not locally causal) and from anthropocentricism (not independently real). Perversely, and to the consternation of Bell himself, his theorem brought physics to the point where it seemingly had to choose between these absurdities.

Whatever the ramifications, it would become obvious by the beginning of this century that Bell’s paper had caused a sea change in physics. But in 1978 the paper, published fourteen years before in an obscure journal, was still mostly unknown.

Bertlmann looked with interest at his new acquaintance, who was smiling affably with eyes almost shut behind big metal-rimmed glasses. Bell had red hair that came down over his ears—not flaming red, but what was known in his native country as “ginger”—and a short beard. His shirt was brighter than his hair, and he wore no tie.

In his painstaking Viennese-inflected English, Bertlmann introduced himself: “I’m Reinhold Bertlmann, a new fellow from Austria.”

Bell’s smile broadened. “Oh? And what are you working on?”

It turned out that they were both engaged with the same calculations dealing with quarks, the tiniest bits of matter. They found they had come up with the same results, Bell by one method on his desktop calculator, Bertlmann by the computer program he had written.

So began a happy and fruitful collaboration. And one day, Bell happened to notice Bertlmann’s socks.

❂

Three years later, in an austere room high up in one of the majestic stone buildings of the University of Vienna, Bertlmann was curled over the screen of one of the physics department’s computers, deep in the world of quarks, thinking not in words but in equations. His computer—at fifteen feet by six feet by six feet one of the department’s smaller ones—almost filled the room. Despite the early spring chill, the air-conditioning ran, fighting the heat produced by the sweatings and whirrings of the behemoth. Occasionally Bertlmann fed it a new punch card perforated with a line of code. He had been at his work for hours as the sunlight moved silently around the room.

He didn’t look up at the sound of someone’s practiced fingers poking the buttons that unlocked the door, nor when it swung open. Gerhard Ecker, from across the hall, was coming straight at him, a sheaf of papers in hand. He was the university’s man in charge of receiving preprints—papers that have yet to be published, which authors send to scientists whose work is related to their own.

Ecker was laughing. “Bertlmann!” he shouted, even though he was not four feet away.

Bertlmann looked up, bemused, as Ecker thrust a preprint into his hands: “You’re famous now!”

The title, as Bertlmann surveyed it, read:

Bertlmann’s Socks and the Nature of Reality
J. S. Bell
CERN, Geneve, Suisse

The article was slated for publication in a French physics periodical, Journal de Physique, later in 1981. Its title was almost as incomprehensible to Bertlmann as it would be for a casual reader.

“But what’s this about? What possibly—”

Ecker said, “Read it, read it.”

He read.

The philosopher in the street, who has not suffered a course in quantum mechanics, is quite unimpressed by Einstein-Podolsky-Rosen correlations. He can point to many examples of similar correlations in everyday life. The case of Bertlmann’s socks is often cited.

My socks? What is he talking about? And EPR correlations? It’s a big joke, John Bell is playing a big published joke on me.

“EPR”—short for the paper’s authors, Albert Einstein, Boris Podolsky, and Nathan Rosen—was, like Bell’s 1964 theorem, which it inspired thirty years later, something of an embarrassment for physics. To the question posed by their title, “Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?,” Einstein and his lesser-known cohorts answered no. They brought to the attention of physicists the existence of a mystery in the quantum theory. Two particles that had once interacted could, no matter how far apart, remain “entangled”—the word Schrödinger coined in that same year—1935—to describe this mystery. A rigorous application of the laws of quantum mechanics seemed to force the conclusion that measuring one particle affected the state of the second one: acting on it at a great distance by those “spooky” means. Einstein, Podolsky, and Rosen therefore felt that quantum mechanics would be superseded by some future theory that would make sense of the case of the correlated particles.

Physicists around the world had barely looked up from their calculations. Years went by, and it became more and more obvious that despite some odd details, ignored like the eccentricities of …