The Telescope in the Ice Read online

Just got back from Tibet, actually about 3 weeks ago and finally got brave enough to attack the many hundreds of messages. Sajama was quite successful as was Tibet with several cores to bedrock.… I am off to the South Pole soon to drill 2400 meter deep holes looking for neutrinos. This project is really interesting and at the cutting edge of high energy astrophysics so we get to make a lot of mistakes.…

  Peace;

  BK

  I asked him about the physics project. It was named AMANDA, he told me, the Antarctic Muon And Neutrino Detector Array. “The contrast of the two projects is pretty interesting in that with Lonnie we go in with light equipment and bring out heavy ice core. With AMANDA we have a huge drill (200,000 lb.) and the data doesn’t weigh anything.”

  He put me in touch with Francis Halzen and his colleague Bob Morse at the University of Wisconsin, the lead institution in the AMANDA collaboration. They were an affable and complementary pair: Francis the theorist and Bob the experimentalist. Bob was lead “man on the ground” in Antarctica and principal investigator, or PI, on the grant from the National Science Foundation that provided most of the funding for the project. Oddly, Francis, who had dreamed the whole thing up, was designated co-PI, meaning he didn’t hold the level of responsibility that Bob did—on paper at least. But it would quickly become apparent that there is almost always more to Francis than meets the eye. Regardless of the hierarchy, he was in fact intellectual leader and spiritus rector of the project, and his was the head on the chopping block if the project happened to fail.

  Be that as it may, both were relaxed, friendly, and quite open. They invited me to attend a collaboration meeting that would be held in conjunction with an open workshop at the University of California, Irvine, in the spring of 1998.

  The collaboration was relatively small at that point in time. Wisconsin, Cal Berkeley, and Irvine had been the founding institutions in 1990; a Swedish contingent from Stockholm and Uppsala Universities had joined in 1992; and a group from a small high-energy physics institute in the former East Germany had joined two years after that. They held private collaboration meetings about three times a year, combining them with workshops every once in a while.

  The purpose of this workshop was to gather together theorists with ideas about astrophysical sources of neutrinos, other neutrino astronomers, scientists and engineers with relevant technologies to bring to the table, experts in South Pole logistics, and representatives of the funding agencies to “initiate the conceptual design of IceCube—a kilometer-scale neutrino facility in Antarctica.” The idea was to “extend the AMANDA technique to kilometer-scale dimensions.” This, as it happened, was the first meeting ever held specifically about IceCube.

  The reason they needed to extend AMANDA was that the sensitivity and angular resolving power of a neutrino telescope is directly related to its size. Owing to the neutrino’s aloofness, it is necessary to monitor as large a volume of ice as possible, because the larger the volume the more likely it is that a neutrino will deign to interact inside it, die, and give birth to a visible child. Theory held that the minimum size needed for so-called discovery potential, the ability to observe the exotic cosmic accelerators that are expected to emit neutrinos, was about one cubic kilometer. AMANDA was the proof of concept for IceCube, the test as to whether it would be at all possible to see neutrinos in deep Antarctic ice. It was also the test bed for the technology that would be used in the larger instrument and the opportunity to explore the two-mile-thick East Antarctic Ice Sheet—no small task. There was dizzying technology involved, especially in Bruce Koci’s drill.

  At the same time, AMANDA was not exactly small. The collaboration had been working on it for about eight years. The array comprised a cylinder 120 meters in diameter, 500 meters high (a bit taller than the Eiffel Tower), and more than a mile deep, monitoring about six million tons of ice.

  * * *

  I soon discovered that not everyone in the AMANDA collaboration was as accommodating as Bob and Francis. The night before the spring meeting, its organizer, Steven Barwick, a professor at Irvine, held a party at his home to welcome us to town. As I thanked him on my way out, Steve informed me that a few members of the collaboration were uncomfortable with my attending the meeting and that I would not be allowed in. I was welcome to attend the open workshop, but I’d have to cool my heels for a few days until it started. I rationalized this disappointment with the thought that the most interesting conversations usually take place on the periphery of such gatherings anyway, especially after a couple of sips of alcohol.

  Indeed, after the party, in the bar of our hotel, I joined Francis Halzen for a nightcap. He was a compact, youthful-looking man, who came across, quite simply, as one of the happiest people I had ever met.

  Francis is not given to long pronouncements. He tends to speak in aphorisms, accompanied by a twinkle of the eye and the look of someone who’s about to let you in on a joke. One of his oldest colleagues and friends, Tom Gaisser from the University of Delaware, notes the “oracular, sibyl-like” quality of the comments Francis makes during group phone calls: they can be taken in several ways, and they usually break the logjam. He is also usually two or three steps ahead of most everyone else in the room. Francis has a deep voice, speaks English with a rich Flemish accent, and will often precede a point he is about to make by saying, “I don’t have to tell you this, because from what I just said it’s obvious,” when it isn’t obvious to me at all. I liked him right away.

  Many physicists seem to be perpetually high on mental activity, the bouncing around of neurons and the linking of synapses in the brain. This exhilarating and pleasurable sensation is the general buzz at these meetings, and Francis seems to thrive on it more than most. In those days, his science talk tended to be the high point of a collaboration meeting. It was generally about some physics insight he’d recently experienced, and as he spoke he was subject to surges of realization and excitement in which the ideas splashed across his mind so fast that his mouth couldn’t keep up. He’d sputter like a motor burning too much oxygen with its fuel, and his words would come out in bursts.

  As we sipped our drinks that evening, he came out with one of his standard, three-steps-ahead-of-the-game remarks. He assured me that even though AMANDA had not yet detected a single bona fide neutrino, the best part of the story was already over, and that had been the discovery that the instrument would actually work. This certainty had arisen in his mind, at least, two years earlier, when the collaboration had discovered that the deep ice under the pole is remarkably clear. To a theorist like himself, the rest was detail; at that point it was obvious the instrument would work. It had taken two years to bring the rest of the physics community along—not to mention certain recalcitrant members of the collaboration—but the workshop that would be held in a few days was a sign that the wider community, including the all-important funding agencies, was preparing to endorse the construction of IceCube.

  It was an historic moment, he told me. The dream of building a neutrino telescope had been around for forty years, since the late 1950s. There had been many attempts in the intervening decades, and two or three other feasibility studies still limped along, but this was the first to show enough promise to merit a move toward the real thing.

  Francis mentioned DUMAND once or twice, and I would hear this name many times in the course of the week. The Deep Underwater Muon And Neutrino Detector was the first pioneering—and by this time, unfortunately, notorious—attempt at realizing the dream. Its DNA is still found everywhere in neutrino astronomy. Several DUMAND veterans worked on AMANDA, and at least one still works on IceCube. This swashbuckling project, first funded in 1980, was supposed to have been located three miles deep on the floor of the Pacific Ocean, nineteen miles off the coast of the big island of Hawaii. It used water as the detection medium, rather than ice. After a long series of mishaps, DUMAND had been canceled just two years earlier, in 1996. There is a half-decent chance that it detected one up-going neutrino in the sixteen years of
its existence. The other competing efforts were also water-based.

  I was surprised to hear Francis say that it had proven easier to build one of these unlikely gadgets at the frigid South Pole than in the warmest tropical waters, for the simple reason that ice allows you to walk on your experiment. The central challenge for the water-based instruments was and remains ocean engineering. As one of the DUMAND pioneers wrote twelve years into the project, by which time they had still not placed even a preliminary design on the ocean floor, “Sailors have long known what we learned painfully, that the sea is an unforgiving medium.”

  By contrast, even though absurdly cold weather and six months of darkness prevented them from working more than four months a year at the pole, the AMANDA collaboration placed their first working detectors in the ice on their second try, two years into the project, and constructed their current working prototype within five years.

  As our conversation ended, Francis suggested characteristically that I ignore Steve Barwick’s advice and show up anyway the next morning. I did and Steve promptly kicked me out.

  I took advantage of my free time over the next few days to go running on Huntington Beach and catch up on my sleep. I hung out with the Amandroids, as they called themselves, during breaks and meals, and most profitably for after-dinner drinks. I spent as much time as I could with Bruce Koci, who didn’t look a whole lot different in squeaky-clean southern California than he had on the mountaintop in Bolivia. He showed up every morning in a pair of skin-tight blue jeans and beaten-up running shoes, wearing a bulky, un-tucked chamois shirt and carrying a venerable daypack that had seen many days at altitude. Never in the years that I knew Bruce did I see clear evidence that he had combed his hair.

  For environmental reasons, he insisted on walking back and forth to the conference venue from his hotel. It rained on one or two mornings, and on those days he protected his rumpled shirt with a formerly blue Gore-Tex jacket that had been bleached nearly white by months if not years of sun, wind, and rain. One morning, he was stopped by the campus police, who suspected he was a homeless person seeking shelter in a campus building.

  Bruce’s main reason for coming to these meetings was to keep himself current on the science in order to psyche himself up for the rigors of drilling. He was one of those rare engineers who realized that it didn’t matter if he built his machines up to spec if they couldn’t do what the scientists needed them to, especially since, much of the time, neither they nor he knew what the specs needed to be. He once referred to his relationship with Lonnie Thompson as “one of the longest-standing friendly relationships between science and engineering ever.”

  He represented one side of an interesting contrast that I noticed particularly at the workshop that followed the collaboration meeting. On one hand were the theorists, the inspiring John Bahcall among them, presenting heady ideas about the cosmic accelerators IceCube might eventually observe. While Bahcall’s feet seemed firmly on the ground, the other theorists had a febrile, untethered quality. The models they proposed seemed like examples of imagination gone wild, as if they were throwing darts at a wall, hoping that a decade or so later, when IceCube might finally produce results, one of those darts might nail an experimental finding. The lucky winner could then claim that she’d made an accurate prediction, ignoring the fact that she might have made several others that were disproven at the same time.

  On the other hand were the experimentalists, who had a gritty, persevering quality like Bruce. It took me some time to realize that the AMANDA collaborators had to have been exhausted just then, since their frantic, annual, four-month Antarctic field season had ended only about a month earlier. It had been a successful season, but there had been plenty of frustration and interpersonal strife mixed in. They were building the world’s largest particle physics detector, after all, dealing with the innumerable details involved in getting such an enormous and infernal gadget to work in one of the most inhospitable places on the planet. Unlike the theorists, they would not be bouncing to the next interesting problem in a week or two. IceCube had not even been designed yet. It wouldn’t be completed for another twelve years.

  * * *

  On the last morning of the collaboration meeting, as the day’s proceedings were to about begin, I joined the Amandroids for a self-serve breakfast of bagels, juice, and coffee in the hall outside the meeting rooms. Steve Barwick approached and said, “Mark, the collaboration has decided to give you a chance to make your case. We’d like you to give a presentation.”

  “When?” I asked.

  “Right now.”

  First, I apologized for not having a set of overhead transparencies (this was before the days of PowerPoint). That brought a laugh. Then I explained that I thought I understood their needs and concerns: I would not leak preliminary results or pass negative rumors, and I believed I had a vested interest in their success. A professor from Irvine took issue with that one, referring to the book Nobel Dreams (subtitle: Power, Deceit and the Ultimate Experiment), which paints an unflattering portrait of Nobel Laureate Carlo Rubbia, a friend, or at least a colleague, of many in the room. I explained that it would be a long time before anything would appear in print (little did I know…). They asked me to leave the room for a while and then invited me back and welcomed me into the collaboration.

  I’ve had open access ever since—for several years, in fact, I had total access: I even attended the closed meetings of the principal investigators. And at the end of 1999 I worked with Bruce Koci, drilling ice at the South Pole.

  * * *

  Those who were there generally agree that AMANDA was more fun than IceCube. It takes a looser mindset and a more risk-taking attitude to get a project off the ground than to engineer it to perfection (although that phase of the project was inspiring as well). The exploration is more wide-ranging. In some sense your job is to make mistakes. There was more derring-do on the ice during AMANDA—no one had heard of safety protocols or standard operating procedures—and Amundsen-Scott South Pole station, like so many other places, was more of a frontier outpost in those days. It is fair to say that AMANDA is the heart of this story. Francis Halzen says that AMANDA was “how neutrino astronomy was born.”

  It turned out that I had also met this close-knit tribe at a propitious time. For Francis wasn’t quite right when he told me the best part was already over. The next six months were probably the most exciting in the history of this project, even including IceCube’s groundbreaking discovery fifteen years later.

  Part I

  The Birth and Youth of the Neutrino

  1. This Crazy Child

  Physicists are more interesting than physics.

  —ROBERT MILLIKAN

  The particle now known as the neutrino first appeared in the mind of the Viennese physicist Wolfgang Pauli sometime near the end of 1930.

  This was about the midpoint of what was arguably the most exciting eight-year period in the history of science, as great thinkers such as Niels Bohr, Werner Heisenberg, Erwin Schrödinger, Max Born, Paul Dirac, Albert Einstein (protesting all the way), and Pauli himself addressed the bewildering puzzles of the atom and crafted the modern theory of quantum mechanics. In 1930, the quest was shifting from atomic structure to the next smallest length scale, the nucleus.

  Pauli was thirty years old. He had been born in 1900—the same year, coincidentally, in which Max Planck discovered a granularity in the energy carried by a certain type of radiation, his so-called quantum of action, and opened the Pandora’s Box of the atomic world (although Pauli, as we shall see, did not necessarily believe in coincidence).

  Recognized as a prodigy in math and physics as a child, Pauli made his first impression on the wider world just after graduating from high school, when he wrote three papers on Einstein’s mathematically sophisticated general theory of relativity, which the great man had completed only three years earlier. Pauli then went to the University of Munich to study under Arnold Sommerfeld, who was perhaps the leading authority on
the “old” Bohr-Sommerfeld quantum theory, which Bohr had introduced in 1913. Pauli earned his doctorate, summa cum laude, in the minimum time allowed, three years, with a thesis on molecular hydrogen that was probably the most ambitious application of the Bohr-Sommerfeld theory ever attempted—and somehow found time to publish a magisterial, 237-page treatise on relativity at about same time. The treatise evoked the following praise from Einstein himself:

  No one studying this mature, grandly conceived work would believe that the author is a man of twenty-one. One wonders what to admire most, the psychological understanding for the development of the ideas, the sureness of mathematical deduction, the profound physical insight, the capacity for lucid, systematic presentation, the knowledge of the literature, the complete treatment of the subject matter, or the sureness of critical appraisal.

  In 1924, the young man proposed what is now known as the Pauli exclusion principle, which explains how the electrons in an atom sort themselves into orbitals that line up with the rows in the periodic table of the elements. Among several of his contributions that might have been worthy of a Nobel, this was the one that won one, a couple of decades after the fact, in 1945. Pauli, who was Jewish by heritage, was in Princeton, New Jersey, at the time, having accepted an appointment at the Institute for Advanced Study in order to escape Nazi persecution. Einstein, who had nominated him for the prize, was in Princeton as well, since the institute had been founded, essentially, in order to give him a place to work outside Germany. Since Pauli didn’t hold a valid passport, he couldn’t travel to Stockholm for the award ceremony, so a splendid banquet was thrown for him in Princeton instead. Partway through, to everyone’s surprise, Einstein rose and proposed an impromptu toast designating Pauli as his intellectual and spiritual heir. “I will never forget the speech,” the younger man wrote in a letter to Max Born, ten years later. “It was like the abdication of a king, installing me as sort of ‘son of choice,’ as successor.”