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FEATURE

FROM THE FARTHEST REACHES OF THE COSMOS TO THE INNERMOST REACHES OF THE ATOM, PITT PHYSICISTS QUEST TO UNDERSTAND THE NATURE OF THE UNIVERSE

THE LONG AND THE SHORT OF IT
WRITTEN BY TOMMY EHRBAR
I THE BEGINNING, BACK BEFORE THE BIG bang even, all existence was melded to-

gether into a single superforce„a perfectly symmetrical crystal of mathematics. Pure order reigned. And then it shattered, again and again and again, giving rise to this messy world with all its randomness, and to certain creatures, destined to sift from the confusion the tiniest hints of order. These creatures are known as physicists, and their quest for order, ancient in origin, continues to this day.

Something quite astonishing has happened to physics in recent years as physicists move in two seemingly opposite directions: inward toward the smallest particles of the atom, and outward toward the farthest reaches of the universe. Let us follow their explorations and see where they most surprisingly lead. Let us pursue the riddle of nature„the long and the short of it.

Pitt professor Eugene Engels will be our interpreter of the worlds inside atoms„the short perspective. He is a particle physicist by profession, a jovial man by temperament, easily given to laughter.

Engels has reason to be in good spirits. He helped corner a most mercurial prey of contemporary physics: the so-called top quark. This spectacular feat took place last spring at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois. Engels had plenty of company. He and colleague Paul Shepard led a Pitt research contingent of seven. Altogether 440 scientists worldwide participated in the experimentation.

The top quark, Engels says, was the final missing elementary particle in what physicists call the Standard Model: the prevailing theory of particles and forces that explains what the universe is composed of.

Quarks, named by the physicist Murray Gell-Mann, are maddeningly elusive. They cannot, by definition, exist on their own, but only in combination with other quarks, forming protons, neutrons, mesons, and other particles. The rest of the quarks predicted by theorists were found years ago: the up quark, down quark, bottom quark, strange quark, and charm quark. Past sightings of top quarks all turned out to be illusions. But the scientists at Fermilab are now, just a tinctureshort of dead certainty, convinced that they have seen signs of the real thing.

Every field of science uses models to visualize and explain what can't be seen directly. Fossil biologists, for example, unearth a few bones and teeth preserved from some ancient animal no one has ever seen. From these fragments, following known rules of anatomy, they build a model of the animal as it might have looked. The more bones they find, the clearer the idea of how the pieces fit together, and the more confident they are that their model fits the real thing.

Particle physicists, as they build a model of matter and energy and how they fit together at the most basic subatomic level, are today like fossil biologists who have found nearly all the bones. Unearthing evidence of the top quark was a pivotal bone in this extraordinary body of work.

The hunt for the top quark, Engels says, began in zeal in 1977, after the bottom quark was detected. Experiments, indeed entire particle accelerators, have since come and gone.

During the past year and a half, Engels and scientists at Fermilab, home of a four-mile-long accelerator ring, sent beams of particles„billions of protons and anti-protons„crashing into each other. "We try, " he says, " to make nature do what we want it to do." The particles created under these conditions immediately decay into other particles, many lasting no more than billionths of a second. It is from these ricocheting patterns that the existence of things like top quarks must be inferred.

The Fermilab group detected a dozen patterns (or "events" ) that, viewed through theory, might represent the signature of a top quark. Engels notes that these results, "while not proving the existence of quarks, provide very strong evidence." He estimates the chance of error as one in 400. At the extremes of scientific inquiry, there is always the problem of separating order from randomness, weeding out false positives„the patterns that leap by chance from background noise.

This turns out to be a problem in both the physics of the very small, and in the physics of the very far away. Three years ago, astronomers detected pulses of distant radio waves indicating the presence of a pulsar: the spinning corpse of a burnt-out star. The pulses periodically sped up, then slowed down, and scientists inferred that the perturbations in these signals might be caused by planets orbiting the pulsars, giving them a gravitational tug. They announced the probable discovery of a planet, 10 times the size of Earth, orbiting a collapsed star. Further analysis, however, showed that what seemed to be fluctuations in the blinking of a pulsar were actually fluctuations in the orbit of the Earth. True, the astronomers had discovered a planet„the one on which they were standing. (In other instances, though, fluctuations detected by scientists have, in fact, signaled the remarkable phenomenon of planets orbiting pulsars.)

And so for good reason, the Fermilab scientists are cautious about deciphering infinitesimal coded messages from deep inside the atom. Yet, with more confidence than ever, they are now fitting together the bones that support their Standard Model.

BUT HOW IS ENGELS SO convinced that quarks are the fundamental stuff of matter? Isn't it possible that something smaller might be found, that something smaller might always be found? "I don't know," he admits. "Maybe someone will come along and explain the quark as two of

something else. But I do know that from these six quarks we have a model for understanding hundreds of other particles. That's quite an economy, quite a powerful tool."

The breakthrough at Fermilab last spring came at a pivotal time in the history of American particle physics. For many years, scientists in this field had staked their lot with the proposed $11 billion, 54-mile superconducting supercollider in Texas. The collider was roundly supported by Congress when it was proposed by the Reagan administration in 1986. But the House of Representatives voted in the summer of 1993 to cut off funding, and the Senate followed suit. Engels saw a dream die. "It's a national tragedy," he says. But his critique is leveled not so much at the loss of the collider, but at "the lack of any long-range national science policy."

Today there are four high-powered accelerators in America: at Stanford, Brookhaven, Cornell, and of course Fermilab, where Engels, as he has for the past several years, travels every two weeks, continuing his experiments, polishing the bones of his model.

He also travels back in time, in a way. According to the creation story that cosmology has provided, the top quark, bottom quark, strange quark, and charm quark„all but the up and down quarks„haven't existed in nature since just after the big bang. By creating these particles in super-hot conditions akin to those present in the very early universe, the Fermilab experimenters were able, in a sense, to peer back in time.

FOR EUGENE ENGELS, THE quest for order all began in the middle school years. "I was fascinated by how things work, everything from bicycles to sewing machines, taking them apart, putting them back together. Later, I was the type who hung around high school after hours„in the chem lab," he laughs. "I just loved compounds„seeing them change!" At Cal Tech, he took a stab at physics. "Immediately I found it both great fun and incredibly hard. I figured if I can do this I can do anything." He laughs again, "I guess I decided to take the path of most resistance." A pause. "Physics allows me to tackle the most fundamental questions. And to see such order and beauty. To behold a carbon atom, as it is excited, giving off light! But there is chaos, too. A simple process„smoke from a cigarette rising in a pattern„we don't understand it, we don't understand the turbulence. Often, late at night, I can't sleep trying to think through a problem. This work is still intensely hard, but I can't imagine anything else so much pure fun."

"Einstein," Engels continues, "is the first hero in my field." In the beginning of the twentieth century, the German-born Albert Einstein was working in a hot bed of inventiveness in a patent office in Bern, Switzerland. Madame Curie had recently discovered radium, and Einstein was pondering the nature of radioactivity. He was seeking a way to relate mass to energy. How could large amounts of energy be produced by the loss of a tiny amount of mass? Only, Einstein began to reason, by multiplying the mass by a very large figure indeed.

Einstein found the correct figure in the speed of light, and in 1905 published his famous equation: E=mc2, energy is equal to mass multiplied by the square of the speed of light. In this formula, he stated in general terms what experimental physicists were discovering in the lab: that we dwell in a dynamic world, where all mass is congealed

energy, all energy liberated matter.

Experimenters such as Ernest Rutherford and theorists such as Erwin Schroedinger and Niels Bohr developed increasingly sophisticated models of atomic structure, leading eventually to the theory of quantum mechanics. Essentially, this theory said that inside the atom, the rules of cause and effect were useless, that it was unknown where an electron would go when impacted, only where it would "probably" go. (To which Einstein responded, "I cannot believe God plays dice with the universe. ")

The next step was technological. The "Ur"-particle accelerator, known as a cyclotron, was developed by Ernest Lawrence at Berkeley in the 1930s leading many years later to the work of Eugene Engels, evidence of the top quark, and a new understanding of the beauty and order of nature in its smallest dimension.

PITT ASTROPHYSICIST David Turnshek is our interpreter of worlds countless light-years away„the long perspective. Turnshek is a hunter of immense star systems and quasars in the vast reaches of the cosmos. In recent work, he identified what appears to be the most distant "ordinary" galaxy known. As he continues to study the remote heavens, his goal is no less than to probe the origin, evolution, and ultimate fate of the universe. Like Eugene Engels„but from a vastly different starting point„he travels far back in time. In fact he describes himself as an archaeo-astronomer. The light he views today allows him to study gas clouds, stars, galaxies, and quasars as they existed billions of years ago.

As a result of the big bang, the universe is expanding. As galaxies move from us, the whole spectrum of emitted light shifts toward the red, or long wavelengths. By measuring the red shift, Turnshek can chart distances. In a general way, the velocity of expansion is proportional to the distance. If one galaxy is twice as far off as another, it is racing away at twice the speed.

Logging on to the Hubble Space Telescope these days, as well as the largest ground-based telescopes, Turnshek aims his vision well beyond the "halo" of our Milky Way galaxy, trying to discover where a new quasar or galaxy may pop up, hoping to solve some of the great riddles that have haunted human beings.

Back in his Allen Hall office he says, "There's something embarrassing about teaching astronomy. The question always comes up: 'What's the universe made out of?' And the answer is: 'We don't know."

Particle physicists such as Engels, he says, enjoy an advantage. "They can experiment, smash stuff together. We can't do this. However, our advantage is that we can use our telescopes to observe the entire electromagnetic spectrum and explore what is actually out there in the universe and how it evolved from the past to the present. We do know the bulk of the universe is made up of non- luminous matter. Ninetyfive percent of it is invisible, is dark to us. We know it's there because of the gravity it exerts, because of how objects move in its presence."

What is all this dark matter? "There are lots of possibilities, " says Turnshek. "Black holes. Unknown planets. Masses too small to be stars. Or, just possibly, exotic subatomic particles that scientists have observed streaking through the universe." Subatomic particles in outer space! The very stuff Eugene Engels is probing down here on earth. Where in the world could they have come from? Unraveling the answer to this question propels us back in time.

In the beginning, some 13 billion years ago, there existed a ball of radiant energy. Nothing else existed, not even space beyond. The ball of energy was both picture and frame, both text and margin. And then it exploded„the big bang„ with unimaginable force. Three minutes after the explosion, subatomic particles began to combine as nuclei of simple atoms, mainly hydrogen and helium, which formed an ionized gas.

The gas continued to expand. The universe was radiant with light. Darkness did not yet exist, nor night. At last, after 700,000 years, a critical point was reached. The density of gas (a state of matter) superseded the density of radiant energy; matter got the upper hand of light. Normal chemistry could now take place, electrons combining with nuclei to form the first stable atoms.

The gas continued to expand. It was opaque and not entirely uniform; some parts were heavier than others. And now, gravitation began its long career as the chief formative cosmic force. Under its pull, those patches denser than others attracted gas from less dense regions, becoming seeds of growing concentrations. And so, about a billion years after the big bang, there came into being the first galaxies.

Within each galaxy, again under the influence of gravitation, hydrogen and helium atoms combined to form stars, and light made a spectacular reentrance into the drama of the cosmos. Some of these stars would end several billion years later by exploding as supernovas, introducing a new kind of matter: heavy atoms, such as carbon, the basis of life here on earth.

The galaxies continued to expand.

And David Turnshek continues to track them.

To what end ? He responds: " I don't like complicated theories. I prefer to study problems that are largely unsolved, rather than work on details that need to be sorted out. If we accept Einstein's gravity theory, we see that the total mass of the universe„visible and dark matter„will determine its ultimate fate."

A key concept, here, is critical mass. For instance, for a rocket to break free of the earth, it needs to achieve a velocity that will overcome the tug of gravity caused by the earth's total mass. Whether a rocket fired at a specific velocity will escape any planet depends critically on the total mass of that planet.

Now consider the total mass of the universe and the fact that the universe is expanding at a known velocity. If total mass of the universe is less than the critical mass, the universe will expand forever. If total mass is greater than the critical mass, the universe will someday quit expanding, then collapse, and eventually the "big crunch" will occur.

As it turns out, Turnshek says, "we have discovered that the total mass of the universe is really close to the critical mass, but just a little bit less„indicating that the universe may expand forever. However, we're still finding more dark matter. So it may work out to be a perfect cosmic equation. Some scientists see this as too extraordinary a coincidence, but to me, assuming the mass of the universe equals the critical mass is a satisfying, simple, and very useful model."

FOR DAVID TURNSHEK, THE quest for order began back in the sixth grade, when a kid in his neighborhood named Ed Potosky (Arts and Sciences '74) "put together two pieces of glass that he had ground and polished into a tube and mounted it to a base. Ed Potosky, a kid just down the street, had built an actual telescope! I decided I had to build one, too.

"I kept building telescopes, five in all, each one bigger. It was only eventually that I began trying to understand what I saw through the telescope and that I began to learn the rich history of astronomy." Turnshek learned, among other things, how a Renaissance physicist once turned the world on its head.

In the early sixteenth century, Nicolaus Copernicus was an administrator of church property at a cathedral in Poland. That was his day job. But after work (and evening services) he returned to his tower home,ascended a platform atop the tower, and there with an astrolabe, a simple instrument Ptolemy had used 1,400 years before, he would take measurements of the stars and calculate planetary orbits.

As Copernicus gazed upon the often misty Baltic sky, he began to formulate a revolutionary theory. He speculated that heavenly bodies moved not around the earth's center, as had been believed for centuries, but around an imaginary point in space, traveling in a complicated series of circular movements, comparable to swinging cabins revolving on a constantly turning Ferris wheel. Altogether, there were 40 of these circular movements.

But Copernicus found his own cosmology "unreasonable," lacking the grace and simple economy of divine creation. Was there an alternative theory available? It so happened that there was.

Rediscovered Greek books stated that certain early astronomers, notably Aristarchus of Samos, had "placed the sun amid the fixed stars, and held that the Earth revolves around the sun." But Aristarchus' theory had never been more than a fringe movement in antiquity because it seemed to contradict everyday experience, and because, if the Earth did rotate on its axis at great speed, how was it that objects and people did not fly off into space?

Copernicus, believing he could answer these difficulties, provisionally adopted the theory and began to see whether it could accommodate known observations of the heavenly bodies.

Copernicus lived on the edge of Europe, far from the cosmopolitan academics in Renaissance Italy who would have laughed his theory to scorn. Alone in his tower, with no wife, no children, no close family, he had nothing to cherish but his extraordinary theory.

And cherish it Copernicus did, for more than 30 years, before he finally published his On the Revolutions o f the Heavenly Spheres in 1543. While his book was at the printer, Copernicus suffered a cerebral hemorrhage and was taken to bed. The first copy of his masterwork was placed in his hands on May 24th, and later that day he died. His revolution would change forever humanity's understanding of its place in the universe and would propel the earth into space.

But not immediately. Our story turns to Venice in the seventeenth century. The extraordinary life of Galileo Galilei offers some uncanny parallels with modern physicists. Galileo can also be seen as a father figure to physics of the very long and of the very short.

Galileo was professor of mathematics and military engineering at the University of Pisa. He was amazingly inventive. He built the first telescope in Italy and promptly sold it to the Doge of Venice for a thousand ducats and a life professorship.

"I have made a telescope," he wrote, "a thing for every maritime and terrestrial affair and an undertaking of inestimable worth. One is able to discover enemy sails and fleets at a greater distance than customary, so that we can discover him two hours or more before he discovers us, and by distinguishing the number and quality of his vessels judge whether to chase him, fight, or run away."

He also, at some point, turned the telescope toward the sky; and observed the moons of Jupiter. Being a practical man who needed money, he tried to sell his findings as a navigational aid. More significantly, his discovery gave tremendous popular support to the Copernican theory that planets did revolve around the sun, contradicing church teaching and getting him into considerable trouble during the Inquisition.

Still, Galileo's main concerns were with terrestrial motion. As a military engineer, he gave a lot of thought to cannon balls. The conventional wisdom in those days was that the maximum range of a cannon was achieved by pointing it at a 45-degree angle. To test the laws of projectiles, Galileo treated the horizontal and vertical mo tions separately. He discovered that a cannonball fired from a perfectly horizontal cannon and another falling vertically from the mouth of the cannon would hit the ground at the same time. This seemed contrary to common reason. But Galileo argued that vertical motion„or any other kind of motion„ could not be used to detect horizontal motion. A sailor cannot tell, by observing any shipboard effect, whether his craft is moving smoothly or standing still. "All steady motion is relative and cannot be detected without reference to an outside point, " pronounced Galileo. In the seventeenth century, he had elucidated the principle of relativity!

From Galileo, then, two lines of inquiry thread their way into our own century and are continuing here at the University of Pittsburgh.

Galileo's confirmation of the Copernican cosmology leads us to such scientists as David Turnshek, observing the heavens, testing theories, seeking to explain the universe as a whole.

Galileo's principle of relativity leads to Einstein, who took the concept into light-speed, and then to such scientists as Eugene Engels, seeking to explain the universe in its smallest dimension.

The long and the short of it.

Astrophysicists who dream of evermightier telescopes. Particle physicists who dream of ever-speedier accelerators. What they share is a compulsion„at nature's extremities„to observe, to decipher, to bring light to the dark matter of all existence in both inner and outer space.

These scientists peel back the confusion of our surroundings„at distances that make us dizzy, at sizes approaching nothingness.

Like Einstein, they hunt for unifying design. Like Copernicus, they climb, day after day, the tower of their imagination, questing for order, or at least considerably less messiness. That's the long and the short of what they do, the beginning and the end of it.


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