The God Particle

by Leon Lederman

  3. It has problems. This issue has to do with the wave function (psi, or ψ and what it means. In spite of the great practical and intellectual success of quantum theory, we cannot be sure we know what the theory means. Our uneasiness may be intrinsic to the mind of man, or it may be that some genius will eventually come up with a conceptual scheme that makes everyone happy. If it makes you queasy, don't worry. You're in good company. Quantum theory has made many physicists unhappy, including Planck, Einstein, de Broglie, and Schrödinger.

  There is a rich literature on the objections to the probabilistic nature of quantum theory. Einstein led the battle, and in a long series of efforts (not easy to follow) to undermine the uncertainty relations, he was continually thwarted by Bohr, who had established what is now called the "Copenhagen interpretation" of the wave function. Bohr and Einstein really went at it. Einstein would invent a thought experiment that was an arrow to the heart of the new quantum theory, and Bohr; usually after a long weekend of hard work, would find the flaw in Einstein's logic. Einstein was the bad boy, the needier in these debates. Like a troublemaking kid in catechism class ("If God is all-powerful, can She build a rock so heavy that not even She can lift it?"), Einstein kept coming up with paradoxes in the quantum theory. Bohr was the priest who kept countering Einstein's objections.

  The story is told that many of their discussions took place during walks in the forest. I can see what happened when they encountered a huge bear. Bohr immediately drew a pair of $300 Reebok Pump running shoes out of his backpack and began lacing them up. "What are you doing, Niels? You know you can't outrun a bear," Einstein logically pointed out. "Ah, I don't have to outrun the bear, dear Albert," responded Bohr. "I only have to outrun you."

  By 1936 Einstein had reluctantly agreed that quantum theory correctly describes all possible experiments, at least those that can be imagined. He then switched gears and decided that quantum mechanics cannot be a complete description of the world, even though it does correctly give the probability for various measurement outcomes. Bohr's defense was that the incompleteness that worried Einstein was not a fault of the theory but a quality of the world in which we live. These two debated quantum mechanics into the grave, and I'm quite sure they are still at it unless the "Old One," as Einstein called God, out of misplaced concern settled the problem for them.

  Einstein and Bohr's debate requires books to tell, but I will try to illustrate the problem with one example. A reminder about Heisenberg's fundamental tenet: no attempt to make a simultaneous measurement of where a particle is and where it is going can ever be entirely successful. Design a measurement to locate the atom, and there it is, as precise as you like. Design a measurement to see how fast it is going—presto, we get its speed. But we can't have both. The reality that these measurements reveal depends on the strategy that the experimenter adopts. This subjectivity challenges our cherished beliefs in cause and effect. If an electron starts at point A and is seen to arrive at point B, it seems "natural" to assume it took a particular path from A to B. Quantum theory denies this, saying the path is unknowable. All paths are possible, and each has its probability.

  To expose the incompleteness of this ghostly-trajectory idea, Einstein proposed a crucial experiment. I cannot do justice to his concept, but I'll try to get across the basic idea. It's called the EPR thought experiment, for Einstein, Podolsky, and Rosen, the three inventors. They proposed a two-particle experiment, in which one particle's fate is tied to the other's. There are ways of creating a pair of particles flying apart from each other so that if one spins up the other must spin down, or if one spins right the other must go left. We send one particle speeding off to Bangkok, the other to Chicago. Einstein said, okay, let's accept the idea that we can't know anything about a particle until we measure it. So we measure particle A, in Chicago, and discover that it spins right. Ergo, we now know about particle B, in Bangkok, whose spin is about to be measured. Before the Chicago measurement, the probability of spin left versus spin right was 50 percent. Now, after Chicago, we know that particle B spins left. But how does particle B know the result of the Chicago experiment? Even if it carries a little radio, radio waves travel at the speed of light, and it would take some time for the message to arrive. What is this communicating mechanism, that doesn't even have the courtesy to travel at the velocity of light? Einstein called this "spooky action at a distance." The EPR conclusion is that the only way to understand the connection of A happenings (the decision to measure at A) with the outcome of B is to provide more details, which quantum theory cannot do. Aha! cried Albert, quantum mechanics isn't complete.

  When Einstein hit him with EPR, even traffic in Copenhagen stopped while Bohr pondered this problem. Einstein was trying to finesse the Heisenberg uncertainty relation by measuring an accomplice particle. Bohr's eventual rejoinder was that one cannot separate the A and B events, that the system must include A, B, and the observer who decides when to make the measurements. This holistic response was thought to have some ingredients of Eastern religious mysticism, and (too many) books have been written about these connections. The issue is whether the A particle and the A observer, or detector, have a real Einsteinian existence or are irrelevant intermediate ghosts before measurement. This particular issue was resolved by a theoretical breakthrough and (aha!) a brilliant experiment.

  Thanks to a theorem developed in 1964 by a particle theorist named John Bell, it became clear that a modified form of the EPR thought experiment could actually be done in the lab. Bell devised an experiment that would predict different amounts of long-distance correlation between A and B particles depending on whether Einstein's or Bohr's point of view was right. Bell's theorem has almost a cult following today, partly because it fits on a T-shirt. For example, there's at least one women's club, probably in Springfield, that meets every Thursday afternoon to discuss Bell's theorem. Much to Bell's chagrin, his theorem was heralded by some as "proof" of paranormal and psychic phenomena.

  Bell's idea resulted in a series of experiments, the most successful of which was carried out by Alan Aspect and colleagues in 1982 in Paris. The experiment in effect measured the number of times detector A results correlated with detector B results, that is, left spin and left spin or right spin and right spin. Bell's analysis enabled one to predict this correlation using the Bohr interpretation of a "complete-as-can-be" quantum theory as opposed to the Einstein notion that there must be hidden variables that determine the correlation. The experiment clearly showed that Bohr's analysis was correct and Einstein's wrong. Apparently these long-distance correlations between particles are the way nature works.

  Did this end the debate? No way. It rages today. One of the more intriguing places where quantum spookiness has arisen is in the very creation of the universe. In the earliest phase of creation, the universe was of subatomic dimensions, and quantum physics applied to the entire universe. I may be speaking for the masses of physicists in saying that I'll stick to my accelerator research, but I'm mighty glad someone is still worrying about the conceptual foundations of quantum theory.

  For the rest of us, we are heavily armed with Schrödinger, Dirac, and the newer quantum field theory equations. The road to the God Particle—or at least its beginning—is now very clear.

  Interlude B

  THE DANCING MOO-SHU MASTERS

  DURING THE ENDLESS PROCESS of raising, and reraising, enthusiasm for the construction of the SSC (the Superconducting Super Collider), I was visiting the Washington office of Senator Bennett Johnston, a Louisiana Democrat whose support was important to the fate of the Super Collider, which is expected to cost $8 billion. Johnston is a curious kind of guy for a U.S. senator. He likes to talk about black holes, time warps, and other phenomena. As I entered his office, he stood up behind his desk and shook a book in my face. "Lederman," he pleaded, "I have a lot of questions for you about this." The book was The Dancing Wu Li Masters by Gary Zukav. During our talk, he kept extending my "fifteen minutes" until we had spent an hour talkin
g physics. I kept looking for an opening, a pause or a phrase I could use as a segue into my pitch for the Super Collider. ("Speaking of protons, I have this machine...") But Johnston was relentless. He talked physics nonstop. When his appointments secretary had interrupted for the fourth time, he smiled and said, "Look, I know why you came. Had you given me your pitch I would have promised to 'do what I can.' But this was much more fun! And I'll do what I can." Actually, he did a great deal.

  To me it was a little disturbing that this U.S. senator, hungry for knowledge, had satisfied his curiosity with Zukav's book. There has been a spate of books over the past several years— The Tao of Physics is another example—that attempt to explain modern physics in terms of Eastern religion and mysticism. The authors are apt to conclude rapturously that we are all part of the cosmos and the cosmos is part of us. We are all one! (Though, inexplicably, American Express bills us separately.) My concern was that a senator might get some anxious ideas from such books just before an important vote for an $8 billion-plus machine to be run by physicists. Of course, Johnston is science-literate and knows a lot of scientists.

  The inspiration for such books is usually quantum theory and its inherent spookiness. One book, which shall go nameless, presents sober explanations of the Heisenberg uncertainty relations, the Einstein-Podolsky-Rosen thought experiment, and Bell's theorem, then launches into a rapturous discussion of LSD trips, poltergeists, and a long-dead entity named Seth who communicated his ideas by taking over the voice and writing hand of an Elmira, New York, housewife. Evidently one premise of this book, and of many like it, is that quantum theory is spooky, so why not accept other strange stuff as scientific fact also?

  Normally, one wouldn't care about such books if they were found in the religion, paranormal, or poltergeist sections of bookstores. Unfortunately, they are often placed in the science category, probably because words like "quantum" and "physics" are used in their titles. Too much of what the reading public knows about physics, it knows from reading these books. We'll pick on just two here, the most prominent of the lot: The Tao of Physics and The Dancing Wu Li Masters, both published in the 1970s. To be fair, Tao, by Fritjof Capra, who holds a Ph.D. from the University of Vienna, and Wu Li, by Gary Zukav, a writer, have introduced many people to physics, which is good. And there's certainly nothing wrong with finding parallels between the new quantum physics and Hinduism, Buddhism, Taoism, Zen, or Hunan cuisine, for that matter. Capra and Zukav have also gotten a lot of things right. There is some good physics writing in both of these books, which gives them a feeling of credibility. Unfortunately, the authors jump from solid, proven concepts in science to concepts that are outside of physics and to which the logical bridge is extremely shaky or nonexistent.

  In Wu Li, for example, Zukav does a nice job of explaining Thomas Young's famous double-slit experiment. But his analysis of the results is rather bizarre. As already discussed, because one gets different patterns of photons (or electrons) depending on whether one slit or two slits are open, an experimenter might ask herself, "How does the particle 'know' how many slits are open?" This, of course, is a whimsical phrasing of a question on mechanisms. The Heisenberg uncertainty principle, a concept which is the basis of quantum theory, says that one cannot determine which slit the particle slithers through without destroying the experiment. By the curious but effective rigor of quantum theory, such questions are not relevant.

  But Zukav gets a different message from the double-slit experiment: the particle does know whether one or two slits are open. Photons are smart! Wait, it gets better. "We have little choice but to acknowledge," Zukav writes, "that photons, which are energy, do appear to process information and to act accordingly, and that therefore, strange as it may sound, they seem to be organic." This is fun, perhaps even philosophical, but we have departed from science.

  Paradoxically, while Zukav is ready to ascribe consciousness to photons, he refuses to accept the existence of atoms. He writes, "Atoms were never 'real' things anyway. Atoms are hypothetical entities constructed to make experimental observations intelligible. No one, not one person, has ever seen an atom." There's our lady in the audience again, challenging us with the question "Have you ever seen an atom?" To give the lady credit, she was willing to listen to the answer. Zukav has already answered the question, in the negative. Even on a literal level, he is now way off the mark. Since his book was published, many people have seen atoms, thanks to the scanning tunneling microscope, which takes beautiful pictures of the little fellows.

  As for Capra, he's much cleverer, hedging his bets and his language, but essentially he's another nonbeliever. He insists that the "simple mechanistic picture of building blocks" should be abandoned. Starting with reasonable descriptions of quantum physics, he constructs elaborate extensions, totally bereft of the understanding of how carefully experiment and theory are woven together and how much blood, sweat, and tears go into each painful advance.

  If the casual disregard of such writers turns me off, the true charlatans positively disconnect me. In fact, Tao and Wu Li constitute a relatively respectable middle ground between good science books and a lunatic fringe of fakes, charlatans, and crazies. These folks guarantee eternal life if you restrict your diet to sumac roots. They give firsthand evidence of the visit of extraterrestrials. They expose the fallacy of relativity in favor of a Sumerian version of the Farmer's Almanac. They write for the "New York Inquirer" and contribute to the crackpot mail of all prominent scientists. Most of these people are harmless, like the seventy-year-old woman who reported to me, in eight closely spaced handwritten pages, her conversation with small green space visitors. Not all are harmless, however. A secretary of the Physical Review, a journal, was shot to death by a man whose incoherent article was refused publication.

  The important point, I believe, is this: all disciplines, all fields of endeavor, have an "establishment," be it the collection of aging physics professors in the prestige universities, the tycoons of the fast-food business, the senior officials of the American Bar Association, or the elder statesmen of the Fraternal Order of Postal Workers. In science the road to advancement is most rapid when giants are overturned. (I knew I'd get a good mixed metaphor out of this.) Thus, iconoclasts, rebels with (intellectual) bombs, are sought after zealously—even by the science establishment itself. Of course, no theorist enjoys having his theory trashed, and some may even react—momentarily and instinctively—like the political establishment in the face of a rebellion. But the tradition of overthrow is too strongly ingrained. The nurturing and rewarding of the young and creative is a sacred obligation of the science establishment. (The saddest report one can get about so-and-so is that it is not enough to be young.) This ethic—that we should remain open to the young, the unorthodox, and the rebellious—creates an opening for the charlatans and the misguided, who can prey upon scientifically illiterate and careless journalists, editors, and other gatekeepers of the media. Some fakes have had remarkable success, such as the Israeli magician Uri Geller or the writer Immanuel Velikovsky or even some Ph.D.'s in science (a Ph.D. is even less a guarantee of truth than a Nobel Prize) who push totally off-the-wall things like "seeing hands," "psychokinesis," "creation science," "polywater," "cold fusion," and so many other fraudulent ideas. Usually the claim is that the revealed truth is being suppressed by the ensconced establishment, intent on preserving the status quo with all the rights and privileges.

  Sure, that can happen. But in our discipline, even members of the establishment rail against the establishment. Our patron saint, Richard Feynman, in the essay "What Is Science?" admonished the student: "Learn from science that you must doubt the experts.... Science is the belief in the ignorance of experts." And later: "Each generation that discovers something from its experience must pass that on, but it must pass that on with a delicate balance of respect and disrespect, so that the race ... does not inflict its errors too rigidly on its youth, but it does pass on the accumulated wisdom plus the wisdom that it may not be
wisdom."

  This eloquent passage expresses the deep training in all of us who have labored in the vineyard of science. Of course, not all scientists can summon the critical juices, the mixture of passion and perception that Feynman could bring to an issue. That's what differentiates scientists, and it is also true that many great scientists take themselves too seriously. They are then handicapped in applying their critical powers to their own work or, worse still, to the work of the kids who are challenging them. No discipline is perfect. But what is rarely understood by the lay public is how ready, how eager, how desperately the collective science community in a given discipline welcomes the intellectual iconoclast—if he or she has the goods.

  The tragedy in all this is not the sloppy pseudoscience writers, not the Wichita insurance salesman who knows exactly where Einstein went wrong and publishes his own book on it, not the faker who will say anything to make a buck—not the Gellers or Velikovskys. It is the damage done to the gullible and science-illiterate general public, which can so easily be duped. This public will buy pyramids, pay a fortune for monkey gland injections, chew apricot pits, go anywhere and do anything to follow the huckster who, having progressed from the back of the wagon to the prime-time TV channel, sells ever more flagrant palliatives in the name of "science."

  Why are we, meaning we the public, so vulnerable? One possible answer is that the lay public is uncomfortable with science, unfamiliar with the way it evolves and progresses. The public sees science as some monolithic edifice of unbending rules and beliefs, and—thanks to the media's portrayal of scientists as uptight nerds in white coats—sees scientists as stodgy old artery-hardened defenders of the status quo. In truth, science is a much more flexible thing. Science is not about status quo. It's about revolution.