The Telescope in the Ice

by Mark Bowen

  As the shock slowly “broke out” of the star, hitting progressively less dense layers of in-falling material and knocking them back out, more nuclei were ripped apart, generating more material for neutrino production, and the neutrinos that were trapped in the core were instantly released. This produced an ultraluminous neutrino burst lasting one or two hundredths of a second—the brightest phenomenon known to astrophysics.

  The theoretical models encounter a problem at this moment, because the release of the neutrinos should take enough energy out of the shock—wind from its sails, so to speak—to cause it to stall and the star to begin to collapse again. But the star does explode, obviously, and one idea is that a stream of neutrinos from the embryonic neutron star at the center of everything keeps the shock going. The ten-second duration of the flash seen by IMB, Kamiokande, and Baksan lends credibility to this notion.

  (You can thank neutrinos, incidentally, for the quality of your teeth. A recent study indicates that some of the antineutrinos given off by the core during these ten seconds undergo inverse beta decay with neon nuclei in that shell of the star and change them to fluorine, and that this seems to be the primary mechanism in the universe for making this element.)

  However the shock was kept alive, it continued to work its way out through the rest of the core and the progressive layers of the onion—which were oblivious to the goings on inside until the shock reached them—and gradually ejected everything but a core of pure neutrons, a neutron star, into the surrounding interstellar medium. Only when the shock reached the surface of the star did it release the light that was seen by eye and telescope 160,000 years later.

  As grand as the optical pyrotechnics may have seemed to the many astronomers watching them from the southern side of our planet, they were as nothing to the neutrino flash and the shock wave. The neutrino flash was about thirty thousand times as energetic as the optical display and two to three hundred times as energetic as the material explosion. Put another way, about 99.5 percent of the energy released in the gravitational collapse of the iron core escaped in the form of neutrinos, and more or less all of the remaining half a percent was carried away by flying material. Only a few thousandths of a percent was given off as light.

  The reason the first light from Supernova 1987a reached us after the neutrinos did was that it took time for the shock to work its way to the outer surface of the star. It traveled at only about a fiftieth the speed of light, while the neutrinos sailed out at close to the speed of light. And the fact that the delay was only a few hours added support to the identification of this supernova with a blue supergiant: it would take the better part of a day for a shock to escape from a red supergiant, because they’re that much larger. One of the great triumphs of Supernova 1987a was that the energy of the neutrino flash, as measured by Kamiokande and IMB, lined up almost perfectly with theoretical estimates for the gravitational energy that should be released in the collapse of an iron core weighing 1.4 solar masses.

  In 2002, Masatoshi Koshiba, the leader of the Kamiokande collaboration, shared half the Nobel Prize in Physics “for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos.” No one from IMB was cited, probably because the only real choice would have been Fred Reines, who had already won one Nobel and had died in 1998. Baksan was ignored altogether.

  Part III

  Touching the Mystery

  Neither the application of the discoveries of science nor even their achievement is to be compared with the struggle in winning them.

  —FREDERICK SODDY

  7. Solid-State DUMAND

  The idea was kind of a non-idea.

  —FRANCIS HALZEN

  Francis was born in the town of Tienen, in the Flemish region of Belgium, in March 1944. The story in his family is that he was almost born by the side of the road. His father had to drive his mother about seven miles to get to the hospital, and the Germans were bombing the road at the time. It was about a year before the end of World War II.

  Tienen was his father’s hometown. It had a population of about twenty thousand, relatively large by Belgian standards. Francis’s parents and older sister had lived there before the war, but had moved to his mother’s small village when the war began, because it was easier to get food in the countryside. His father owned a road and bridge building company that had been in the family for several generations. As such, according to Francis, his choice was to “work for the Germans and be killed later, or not work for the Germans and be killed immediately.” Louis Halzen hid in the Pyrenees in the south of France for most of the war, and figured out a way to return and live anonymously in his wife’s village for the last two years or so.

  Francis was too young to remember the war, and as a child he wasn’t particularly aware that he was growing up in its aftermath, although he does remember many stories of suffering, mostly for lack of food. Even for a few years after the war, the family ate chicken only once or twice a year. They moved back to Tienen when he was about four.

  He remembers his childhood as a placid one. He ranked at the top of his class all through his education in every subject except religion. (“I don’t know what went wrong there. It’s not like it’s a big deal. It was not intentional. I tried.”) But he claims that his excellence in school had no effect on him. “I never really realized it. Neither did my parents. In fact, I had to be pushed to go to university.” Looking back, he realizes it was probably a lack of confidence.

  He remembers the Belgian school system as being “absolutely superb, I have no other word for it.” He was good at science and math, and could speak Dutch, French, Greek, and Latin in addition to his native Flemish by the time he graduated from high school. He was also reasonably proficient in Elizabethan and Middle English from reading Shakespeare and Chaucer. He remembers being laughed at by British tourists when he tried to make small talk with them in these antiquated dialects during his family’s yearly vacations to the shore near Bruges.

  It was a classical education, not a practical one, and there were no elective courses—a good thing in his view. He believes his high school education was “pretty much the equivalent of what you would get at a very good liberal arts college” in the United States and that he could have gone straight into a Ph.D. program from there.

  No one in his family had ever gone to university. He was destined for his father’s construction business. Ironically, however, it was his father who encouraged him to go on in school. Louis had an active mind and a great interest in literature. When Francis remembers him, “it’s with a book.”

  Being a diffident young man, interested in just about everything, it was unclear what he should study, so his father had him speak to a counselor, who suggested pharmacy of all things. He was steered away from that by one of his high school math teachers, who stood him in front of a pharmacy one day, pointed through the window at a man inside mixing pills, and asked him if that was what he wanted to do for the rest of his life.

  Since Belgian education followed the French, Cartesian tradition, in which mathematics is the most revered of the disciplines, he made the non-choice and majored in math. He wasn’t really free to choose his university either. The Belgium university system was sliced into four more or less rigid segments, dictated by the country’s bedrock provincialism: the official state religion, Roman Catholic, versus secular, and Flemish versus Walloon- or French-speaking. Being Flemish and Catholic (though non-observing), he went to the Catholic University of Leuven, eighteen kilometers from Tienen, and commuted by train.

  He remembers the formal instruction at Leuven as being vastly inferior to his instruction in high school. For one thing, the school was weak in science. Had his family been more aware of the world of higher education, he probably would have chosen the University of Brussels, a non-sectarian school that was (and still is) much stronger in the sciences. In fact, Brussels now participates in IceCube. Oddly, the classes Francis found most stimulating at Leuven were the ones in religio
n that he was required to take once a year. Theology was an active field at the time owing to the debates engendered by Vatican II, and there were a few left-wing theologians on the faculty with remarkable intellects. “Even if I wasn’t very interested in what they were telling me, being exposed to people that are the top of their field is very important.”

  Francis believes that one always lives with the blind spots in one’s upbringing, but that one can erase them, at least partially, through education and the broadening of one’s worldview. He believes this is how he discovered his true calling professionally, over a period of about twenty-five years.

  He majored in math at first and slowly shifted to physics as he realized that that was what he “really wanted to do.” “You have to get rid of your upbringing slowly, right?… I think deep down I always wanted to be a physicist and an experimentalist; it just took me a long time to move from mathematics to real physics. [I] wandered for twenty years doing theoretical physics, and it’s clear from my period as a theoretical physicist that I’m a very poor mathematician.” He obtained intermediate degrees in both subjects and his final degree in physics alone.

  Most people would probably agree, almost half a century later, that Francis has had a stellar career in science and academia. But he is more proud of being the first member of his family to graduate from university and that in being so he might also have set an example. Almost every family member who has come after him has earned a Ph.D.

  He never figured he’d continue in physics. He was planning to teach high school for a year or two and then join the family business. His father figured the same: his son’s education had gone on long enough as far as he was concerned; it was time to start earning a living.

  Unbeknownst even to himself, however, Francis caught the research bug during his third year in university, the first in his entire education in which he was allowed to take an elective course, and the first in that formal milieu in which he ever spoke directly to a professor. The physics department required a thesis, and by pure luck he did his thesis work in the one corner of the department that had a sense of what true research actually was. Since it’s an international game, the professors he began to work with also had contact with the wider world.

  The luminary of Leuven’s physics department in those years was Georges Lemaître, who is now recognized as the father of both big bang theory and the theory of the expanding universe (the latter is often mistakenly attributed to Edwin Hubble). Lemaître was a Catholic priest and, for a time, head of the Pontifical Academy of Sciences. A superb mathematician, he had developed his two cosmological theories in 1925 as solutions to Einstein’s field equations for general relativity, which had appeared only nine years earlier. At first, even Einstein didn’t believe in the physical reality of Lemaître’s solutions, telling him famously, “Your calculations are correct, but your physics is abominable.” But Einstein and the rest of the scientific community came around when Hubble provided the first observational evidence to support Lemaître’s theories, about two years after he proposed them.

  Lemaître was an old man by the time Francis crossed paths with him; he died the year Francis graduated from university. And although Francis knew him by reputation, there is vivid evidence that he did not know him by sight: The great man could no longer walk, and he was driven to work in a limousine. Francis and another student sometimes had the job of meeting the limousine, transferring this old gentleman in his ecclesiastical robes to a chair, and carrying him up the steps to the institute where they worked. Francis only learned who he had been carrying twenty years later, from the other student, who had become a professor at Leuven.

  Lemaître was particularly devoted to numerical calculation and as a scientist of some renown, had access to the most powerful computers of his time. One of Francis’s early accomplishments was to use a machine that had been built under Lemaître’s direction to carry out the first computerized calculation of a Feynman diagram. (“It doesn’t matter what this means, but I’m very proud of this,” he says.) He undertook this project under the direction of Martinus “Tiny” Veltman, at the University of Utrecht, who would win the Nobel Prize in 1999 for a fundamental theoretical triumph that also required computers. So Francis found himself in the finest international company the moment his research career began.

  Luck has played an extraordinary role in his career—mostly for the good, it seems, but sometimes for the bad—and his undergraduate thesis is an example of both. One day his supervisor handed him a copy of the paper, fresh off the press, in which George Zweig of Caltech first proposed the existence of quarks. (It was Zweig who later offered him a position at Caltech.) It was an odd paper, because Zweig didn’t have the math to describe his new model; he employed strange geometric constructions to do the calculations. But Francis, with his rigorous training in mathematics, saw right away that they could be done with group theory and recast the model in elegant group theoretic terms. (“Imagine the luck involved!” he says.) It was a good piece of work, but the subject seemed so highly theoretical that he dropped it when he finished his thesis. Looking back, this was an obvious mistake, but how could he have known that quarks would become the greatest discovery of the next few decades in particle physics?

  * * *

  And so, having done estimable work even as an undergrad, Francis got a job as a high school teacher in a town near Tienen—but never took it up. His work had caught the eye of a Belgian theorist named Edward Verboven, who invited him to study with him at the University of Nijmegen in the Netherlands (to which Francis refers as “the land of great physicists north of the border”). Again it took a wise teacher to make him realize what he really wanted to do. This also happened to be a promotion, since graduate students were paid more than high school teachers. When the physics department at Leuven realized that Nijmegen was trying to steal him away, they offered him a position, so he followed the path of least resistance and stayed where he was—a theme in his career.

  Francis looks back on his doctoral thesis as a total waste of time. It had to do with S-matrix theory, an idea that was sexy at the time but has now disappeared “because,” he points out, “it had nothing to do with real world.” He calls it the string theory of the late sixties, since he suspects that string theorists “are going through a similar period now.” (This is one of his milder pronouncements about string theory. “It’s the ultimate form of bad physics to think that your imagination is more important than data and evidence,” he once told me. “It’s not just arrogance, it’s not just bad taste, it’s bad physics.”)

  He earned his doctorate over the course of only three years, defended his thesis a few days before Christmas 1968, and was married that same week. His wife, Nelly, was training to be a teacher at a school near Tienen where his sister taught, and she and Francis had met at a school dance. Most women of an intellectual bent studied to become teachers in Belgium, as it was rare for a Belgian woman to attend university back then.

  Francis has made surprisingly few career moves. They have all either been passive, as we have seen in his schooling, or completely spontaneous. And he has never applied for a job. The right offer has always appeared just in time to allow him to “transition from place to place following the science I wanted to do.”

  Even though he doesn’t think much of his Ph.D. thesis, it won him, as I have mentioned, a monetary prize from the Belgian government for being the best doctoral thesis submitted in the country that year. It must have been a hefty amount, since it allowed him not only to buy the “ugly hippie yellow/orange MGB” that fate would have him and Nelly drive to Méribel, France, it also allowed them to move to Geneva and support themselves while Francis volunteered in the theory group at CERN.

  It was a large theory group, a hundred or so, and it was an unsupportive, sink-or-swim environment. The group was led by a famously tough Belgian theorist named Léon Van Hove. One might guess that this would have given a fellow countryman a leg up, but this guess would be wrong. W
ithin a few weeks of Francis’s arrival, Van Hove strode into his office and said, “Halzen, the people we’ve had here from Belgium have been so bad over the last few years, you may be the last one.”

  “Well, at least you get me cheap,” Francis responded, pointing out that he wasn’t being paid.

  He had learned to work independently at Leuven, and he wasn’t intimidated by CERN’s milieu. He found some collaborators, began producing papers, and had a paying job by Christmas 1969. “So it was lucky that Van Hove had come into my office to insult Belgian theoreticians. Otherwise, I may not have had a salary for much longer.”

  Two years later, he had the chance encounter with Vernon Barger in Méribel that led to his spontaneous relocation to the American Midwest.

  This was a big jump, culturally. Madison was a sleepy country town compared to Geneva. Francis sums up the new state of affairs with his usual pithiness: you couldn’t get a decent cup of coffee in Madison, and he and Nelly used to drive all the way to Chicago to shop. (Francis is a dedicated gourmet. He tends to sample the best restaurants in the innumerable cities he visits in his travels, and his stories often revolve around memorable meals in the world’s most famous establishments.)

  But Nelly liked Madison immediately, thanks mostly to the educational opportunities. She began taking classes at the University of Wisconsin, earned a bachelor’s degree in the history of art, went on to a doctorate in French literature, and now teaches in the department of French and Italian.