By the early part of the twentieth century atoms had become the frontier of physics; in the 1940s, nuclei became the focus of research. Progressively, more and more domains became subject to observation. With the development of instruments of ever-increasing power, we looked more and more closely at things smaller and smaller. The observations and measurements were followed inevitably by syntheses, compact summaries of our understanding. With each major advance, the field divided; some scientists followed the "reductionist" road toward the nuclear and subnuclear domain, while others followed the path to a greater understanding of atoms (atomic physics), molecules (molecular physics and chemistry), nuclear physics, and so on.
THE ENTRAPMENT OF LEON
I started out as a molecules kid. In high school and early college I loved chemistry, but I gradually shifted toward physics, which seemed cleaner—odorless, in fact. I was strongly influenced, too, by the kids in physics, who were funnier and played better basketball. The giant of our group was Isaac Halpern, now a professor of physics at the University of Washington. He claimed that the only reason he went to see his posted grades was to determine whether the A had a "flat top or a pointy top." Naturally, we all loved him. He could also broad-jump farther than any of us.
I became intrigued with the issues in physics because of their crisp logic and clear experimental consequences. In my senior year in college, my best friend from high school, Martin Klein, the now eminent Einstein scholar at Yale, harangued me on the splendors of physics during a long evening over many beers. That did it. I entered the U.S. Army with a B.S. in chemistry and a determination to be a physicist if I could only survive basic training and World War II.
I was born at last into the world of physics in 1948, when I began my Ph.D. research working with the world's most powerful particle accelerator of its time, the synchrocyclotron at Columbia University. Dwight Eisenhower president of Columbia, cut the ribbon dedicating the machine in June of 1950. Having helped Ike win the war, I was obviously much appreciated by the Columbia authorities, who paid me almost $4,000 for just one year of ninety-hour weeks. These were heady times. In the 1950s, the synchrocyclotron and other powerful new devices created the new discipline of particle physics.
To the outsider, perhaps the most salient characteristic of particle physics is the equipment, the instruments. I joined the quest just as particle accelerators were coming of age. They dominated physics for the next four decades, and still do. The first "atom smasher" was a few inches in diameter. Today the world's most powerful accelerator is housed at Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois. Fermilab's machine, called the Tevatron, is four miles around, and smashes protons and antiprotons together with unprecedented energies. By the year 2000 or so, the Tevatron's monopoly of the energy frontier will be broken. The Superconducting Super Collider (SSC), the mother of all accelerators, presently being built in Texas, will be fifty-four miles around.
Sometimes we ask ourselves: have we taken a wrong turn somewhere? Have we become obsessed with the equipment? Is particle physics some sort of arcane "cyber science," with huge groups of researchers and megalithic machines dealing with phenomena so abstract that even She is not sure what happens when particles collide at high energies? We can gain confidence and inspiration by viewing the process as following a chronological Road, one that could plausibly have started in the Greek colony of Miletus in 650 B.C. The Road's destination is a city where all is understood—where the sanitation workers and even the mayor know how the universe works. Many have followed The Road: Democritus, Archimedes, Copernicus, Kepler, Galileo, Newton, Faraday, all the way to Einstein, Fermi, and my contemporaries.
The Road narrows and broadens; it passes long stretches of nothing (like Route 80 through Nebraska) and curvy sections of intense activity. There are tempting side streets labeled "electrical engineering," "chemistry," "radio communications," or "condensed matter." Those who have taken the side streets have changed the way people live on this planet. But those who stay with The Road find that it is clearly marked all the way with the same sign: "How does the universe work?" It is on this Road that we find the accelerators of the 1990s.
I got on The Road at Broadway and 120th Street in New York City. In those days the scientific problems seemed very clear and very important. They had to do with the properties of what's called the strong nuclear force and some theoretically predicted particles called pi mesons, or pions. Columbia's accelerator was designed to produce lots of pions by bombarding innocent targets with protons. The instrumentation was rather simple at the time, simple enough for a graduate student to understand.
Columbia was a hotbed of physics in the 1950s. Charles Townes would soon discover the laser and win the Nobel Prize. James Rainwater would win the Prize for his nuclear model, and Willis Lamb for measuring the tiny shift in hydrogen's spectral lines. Nobel laureate Isadore Rabi, who inspired all of us, headed up a team that included Norman Ramsey and Polykarp Kusch, both to become Nobel winners in due course. T. D. Lee shared the Nobel for his theory of parity violation. The density of professors who had been anointed with Swedish holy water was both exhilarating and depressing. As young faculty, some of us wore lapel buttons that read "Not Yet."
For me the Big Bang of professional recognition took place in the period 1959–1962 when two of my Columbia colleagues and I carried out the first-ever measurement of high-energy neutrino collisions. Neutrinos are my favorite particles. A neutrino has almost no properties: no mass (or very little), no electric charge, and no radius—and, adding insult to injury, no strong force acts on it. The euphemism used to describe a neutrino is "elusive." It is barely a fact, and it can pass through millions of miles of solid lead with only a tiny chance of being involved in a measurable collision.
Our 1961 experiment provided the cornerstone for what came to be known in the 1970s as the "standard model" of particle physics. In 1988 the experiment was recognized by the Royal Swedish Academy of Science with the Nobel Prize. (Everybody asks, why did they wait twenty-seven years? I don't really know. I used to give my family the facetious excuse that the Academy was dragging its feet because they couldn't decide which of my great achievements to honor.) Winning the Prize was of course a great thrill. But that thrill does not really compare with the incredible excitement that gripped us at the moment when we realized our experiment was a success.
Physicists today feel the same emotions that scientists have felt for centuries. The life of a physicist is filled with anxiety, pain, hardship, tension, attacks of hopelessness, depression, and discouragement. But these are punctuated by flashes of exhilaration, laughter, joy, and exultation. These epiphanies come at unpredictable times. Often they are generated simply by the sudden understanding of something new and important, something beautiful, that someone else has revealed. However, if you are mortal, like most of the scientists I know, the far sweeter moments come when you yourself discover some new fact about the universe. It's astonishing how often this happens at 3 A.M., when you are alone in the lab and you have learned something profound, and you realize that not one of the other five billion people on earth knows what you now know. Or so you hope. You will, of course, hasten to tell them as soon as possible. This is known as "publishing."
This is a book about a string of infinitely sweet moments that scientists have had over the past 2,500 years. These sweet moments add up to our present knowledge about what the universe is and how it works. The pain and depression are part of the story, too. Often it is the obstinacy, the stubbornness, the pure orneriness of nature that gets in the way of the "Eureka" moment.
The scientist, however, cannot depend on Eureka moments to make his life fulfilling. There must be some joy in day-to-day activities. For me, this joy is in designing and building apparatus that will teach us about this extraordinarily abstract subject. When I was an impressionable graduate student at Columbia, I helped a world-famous professor visiting from Rome build a particle counter. I was the virgin in this an
d he a past master. Together we turned the brass tube on the lathe (it was after 5 P.M. and the machinists had all gone home). We soldered on the glass-tipped end caps and strung a gold wire through the short, insulated metal straw penetrating the glass. Then we soldered some more. We flushed the special gas through the counter for a few hours while hooking an oscilloscope to the wire, protected from a 1,000-volt power supply by a special capacitor. My professor friend—let's call him Gilberto, because that was his name—kept peering at the green trace of the oscilloscope while lecturing me in faultlessly broken English on the history and evolution of particle counters. Suddenly Gilberto went stark, raving wild. "Mamma mia! Regardo incredibilo! Primo secourso!" (Or something like that.) He shouted, pointed, lifted me up in the air—even though I was six inches taller and fifty pounds heavier than he—and danced me around the room.
"What happened?" I stammered.
"Mufiletto!" he replied. "Izza counting. Izza counting!"
He was probably putting some of this on for my benefit, but he was genuinely excited that we had, with our hands, eyes, and brains, fashioned a device that detected the passage of cosmic ray particles, registered them by small blips in the sweep of the oscilloscope. Although he must have seen this phenomenon thousands of times, he never got over the thrill. That one of these particles may just possibly have started its voyage to 120th Street and Broadway, tenth floor, light-years ago in a distant galaxy was only part of the excitement. Gilberto's seemingly never-ending enthusiasm was contagious.
THE LIBRARY OF MATTER
When explaining the physics of fundamental particles, I often borrow (and embellish on) a lovely metaphor from the Roman poet-philosopher Lucretius. Suppose we are given the task of discovering the most basic elements of a library. What would we do? First we might think of books in their various subject categories: history, science, biography. Or perhaps we would organize them by size: thick, thin, tall, short. After considering many such divisions we realize that books are complex objects that can be readily subdivided. So we look inside. Chapters, paragraphs, and sentences are quickly dismissed as inelegant and complex constituents. Words! Here we recall that on a table near the entrance there is a fat catalogue of all the words in the library—the dictionary. By following certain rules of behavior, which we call grammar; we can use the dictionary words to compose all the books in the library. The same words are used over and over again, fitted together in different ways.
But there are so many words. Further reflection would lead us to letters, since words are "cuttable." Now we have it! Twenty-six letters can make the tens of thousands of words, and they can in turn make the millions (billions?) of books. Now we must introduce an additional set of rules: spelling, to constrain the combinations of letters. Without the intercession of a very young critic we might publish our discovery prematurely. The young critic would say, smugly no doubt, "You don't need twenty-six letters, Grandpa. All you need is a zero and a one." Children today grow up playing with digital crib toys and are comfortable with computer algorithms that convert zeroes and ones to the letters of the alphabet. If you are too old for this, perhaps you are old enough to remember Morse code, composed of dots and dashes. In either case we now have the sequence: 0 or 1 (or dot and dash) with appropriate code to make the twenty-six letters; spelling to make all the words in the dictionary; grammar to compose the words into sentences, paragraphs, chapters, and, finally, books. And the books make the library.
Now, if it makes no sense to take apart the 0 or the 1, we have discovered the primordial, a-tomic components of the library. In the metaphor imperfect as it is, the universe is the library, the forces of nature are the grammar spelling, and algorithm, and the 0 and 1 are what we call quarks and leptons, our current candidates for Democritus's a-toms. All of these objects, of course, are invisible.
QUARKS AND THE POPE
The lady in the audience was stubborn. "Have you ever seen an atom?" she insisted. It is an understandable if irritating question to a scientist who has long lived with the objective reality of atoms. I can visualize their internal structure. I can call up mental pictures of cloudlike blurs of electron "presence" surrounding the tiny dot nucleus that draws the misty electron cloud toward it. This mental picture is never precisely the same for two different scientists because both are constructing these images from equations. Such written prescriptions are not user-friendly when it comes to humoring the scientist's human need for a visual image. Yet we can "see" atoms and protons and, yes, quarks.
My attempts to answer this thorny question always begin with trying to generalize the word "see." Do you "see" this page if you are wearing glasses? If you are looking at a microfilm version? If you are looking at a photocopy (thereby robbing me of my royalty)? If you are reading the text on a computer screen? Finally, in desperation, I ask, "Have you ever seen the pope?"
"Well, of course," is the usual response. "I saw him on television." Oh, really? What she saw was an electron beam striking phosphorus painted on the inside of a glass screen. My evidence for the atom, or the quark, is just as good.
What is that evidence? Tracks of particles in a bubble chamber. In the Fermilab accelerator, the "debris" from a collision between a proton and an antiproton is captured electronically by a three-story-tall, $60 million detector. Here the "evidence," the "seeing," is tens of thousands of sensors that develop an electrical impulse as a particle passes. All of these impulses are fed through hundreds of thousands of wires to electronic data processors. Ultimately a record is made on spools of magnetic tape, encoded by zeroes and ones. This tape records the hot collisions of proton against antiproton, which can generate as many as seventy particles that fly apart into the various sections of the detector.
Science, especially particle physics, gains confidence in its conclusions by duplication—that is, an experiment in California is confirmed by a different style of accelerator operating in Geneva. Also by building into each experiment checks and tests confirming that the apparatus is functioning as designed. It is a long and involved process, the result of decades of experiments.
Still, particle physics remains unfathomable to many people. That stubborn lady in the audience isn't the only one mystified by a bunch of scientists chasing after tiny invisible objects. So let's try another metaphor...
THE INVISIBLE SOCCER BALL
Imagine an intelligent race of beings from the planet Twilo. They look more or less like us, they talk like us, they do everything like humans —except for one thing. They have a fluke in their visual apparatus. They can't see objects with sharp juxtapositions of black and white. They can't see zebras, for example. Or shirts on NFL referees. Or soccer balls. This is not such a bizarre fluke, by the way. Earthlings are even stranger. We have two literal blind spots in the center of our field of vision. The reason we don't see these holes is because our brain extrapolates from the information in the rest of the field to guess what should be in these holes, then fills it in for us. Humans routinely drive 100 miles per hour on the autobahn, perform brain surgery, and juggle flaming torches, even though a portion of what they see is merely a good guess.
Let's say this contingent from the planet Twilo comes to earth on a goodwill mission. To give them a taste of our culture, we take them to see one of the most popular cultural events on the planet: a World Cup soccer match. We, of course, don't know that they can't see the black-and-white soccer ball. So they sit there watching the match with polite but confused looks on their faces. As far as the Twiloans are concerned, a bunch of short-pantsed people are running up and down the field kicking their legs pointlessly in the air, banging into each other, and falling down. At times an official blows a whistle, a player runs to the sideline, stands there, and extends both his arms over his head while the other players watch him. Once in a great while the goalie inexplicably falls to the ground, a great cheer goes up, and one point is awarded to the opposite team.
The Twiloans spend about fifteen minutes being totally mystified. Then, to pas
s the time, they attempt to understand the game. Some use classification techniques. They deduce, partially because of the clothing, that there are two teams in conflict with one another. They chart the movements of the various players, discovering that each player appears to remain more or less within a certain geographical territory on the field. They discover that different players display different physical motions. The Twiloans, as humans would do, clarify their search for meaning in World Cup soccer by giving names to the different positions played by each footballer. The positions are categorized, compared, and contrasted. The qualities and limitations of each position are listed on a giant chart. A major break comes when the Twiloans discover that symmetry is at work. For each position on Team A, there is a counterpart position on Team B.
With two minutes remaining in the game, the Twiloans have composed dozens of charts, hundreds of tables and formulas, and scores of complicated rules about soccer matches. And though the rules might all be, in a limited way, correct, none would really capture the essence of the game. Then one young pipsqueak of a Twiloan, silent until now, speaks his mind. "Let's postulate," he ventures nervously, "the existence of an invisible ball."
"Say what?" reply the elder Twiloans.
While his elders were monitoring what appeared to be the core of the game, the comings and goings of the various players and the demarcations of the field, the pipsqueak was keeping his eyes peeled for rare events. And he found one. Immediately before the referee announced a score, and a split second before the crowd cheered wildly, the young Twiloan noticed the momentary appearance of a bulge in the back of the goal net. Soccer is a low-scoring game, so there were few bulges to observe, and each was very short-lived. Even so, there were enough events for the pipsqueak to note that the shape of each bulge was hemispherical. Hence his wild conclusion that the game of soccer is dependent upon the existence of an invisible ball (invisible, at least, to the Twiloans).
The God Particle Page 2
