The 4 Percent Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality - Richard Panek (2011)
Part III. The Face of the Deep
Chapter 7. The Flat Universe Society
ON MONDAY EVENINGS throughout the mid-1980s, the DuPage County Center for Scientific Culture held what would have been the only course in its catalogue, if it had had a catalogue. The classroom was the basement of a split-level suburban home. The student body was sparse: a handful of researchers, postdocs, and graduate students from the University of Chicago or the nearby Fermi National Accelerator Laboratory, as well as, often, a distinguished visitor. The students served as the instructors, too. Tuition was five bucks a week, which bought you pizza (or sometimes barbecued "backup" hamburgers, resurrected from the bowels of the freezer), beer, and a turn at the blackboard.
The topics varied from week to week, and from moment to moment. The first topic of the evening might be a recently published paper that had gotten it all wrong, whatever "it" was, or a wildly speculative hypothesis that someone wanted to test. From there the evening would follow its own path. The chalk would pass from hand to hand, feverishly, amid shouts of criticism or approval and screams of sudden insight or instant regret, and by the end of the class the participants were vowing to write a response eviscerating the recent paper that had gotten it all wrong, whatever "it" was, or a new paper championing an original theory that, whether one of the participants had arrived at the meeting espousing it or it had arisen over the course of the evening, had already gone through its own peer evisceration. (Eventually the center instituted a two- or three-day cooling-off period before participants could write up their papers.) But whatever path the evening had eventually followed, and however circuitously and riotously, the topic was always basically the same—what to do next with the Big Bang universe.
That universe was now nearly twenty years old. While observers were trying to measure the two numbers in cosmology—the universe's current rate of expansion, and how much the expansion was slowing down—theorists were trying to figure out how the expansion itself worked. Like Jim Peebles in his instant classic Physical Cosmology, they wanted to make explicit the connection between the physics of the early universe and the universe we see today.
That connection had been implicit from the start, in Lemaître's invocation of a primeval atom. And over the decades other theorists had tried to work out the calculations that would reveal how the universe had gotten from there to here—from hypotheses about a primeval fireball to observations of today's galaxies. The discovery of the cosmic microwave background, however, made a dialogue between particle physicists and astronomers necessary.
When the Princeton physicists had visited Holmdel in early 1965 to inquire about the detection of a 3 K signal, the Bell Labs astronomers explained what wavelength they had designed their antenna to detect, how they had taken into account the rattling of electrons—topics the Princeton physicists knew well. Their colleague Jim Peebles had already performed the calculation for the relic temperature of the primeval fireball, and Bob Dicke himself had invented some of the equipment in the Bell Labs experiment. Then the Bell Labs astronomers listened as the Princeton physicists talked about the Big Bang and the Steady State theories, how Dicke was hoping for evidence of an oscillating universe—topics the Bell Labs astronomers understood. Arno Penzias and Bob Wilson, like most astronomers, didn't take sides in the debate between the two theories, though Wilson had studied with Fred Hoyle and felt a slight allegiance to a Steady State universe. But that summit on Crawford Hill nonetheless marked the moment that particle physicists and astronomers began to talk to each other in earnest, with a sense that the conversation might actually lead somewhere: from here to there—from the current constitution of the universe to finer and finer fractions of a second in its history.
Hence the nickname for the nonexistent DuPage County Center for Scientific Culture: Primordial Pizza. The real institution was the NASA/Fermilab Astrophysics Center, five minutes away, and Edward "Rocky" Kolb and Michael Turner had been hired to run the Fermilab center in part because they were willing to entertain the unorthodox. Because Primordial Pizza met on Mondays, classes sometimes fell on national holidays. No matter. Invitations to lead a seminar went out to distinguished visitors, who had to wonder why they were being summoned to Fermilab on Memorial Day, and who, after leading a seminar in the scholarly and respectful confines of a Fermilab conference room or auditorium, soon found themselves sitting in the "less than elegant surroundings" of a bachelor pad while being bombarded with questions by students dozens of years their junior.
Kolb had a wife and three kids, so to Turner went the honor of playing host. In the tradition of memorable comedic pairings—Laurel and Hardy, Abbott and Costello, Cheech and Chong (Turner's reference of choice)—they complemented each other stylistically while possessing the same comic, and cosmic, sensibility. Kolb played strait-laced family guy, the tall lug with a push-broom mustache; Turner handled eye-rolling bomb thrower, long of hair and short of patience.
Kolb and Turner had both passed through Caltech—Turner as an undergraduate, Kolb as a postdoc. Even at informal meetings there, they found, you had to prepare meticulously, anticipating every possible objection. You were afraid to be wrong. Up the California coast, Luis Alvarez famously hosted Oreos-and-beer gatherings at "The Castle," his estate in the Berkeley hills. Each week a graduate student or postdoc had to present as-yet-unpublished news from the physics community. "I don't believe that," Alvarez would snap, moments into the talk, or "That doesn't make sense," or "The error bar doesn't look right." You had to explain and defend the research as if it were your own, even if you'd actually gotten it by phoning friends at Columbia or Harvard and begging them to throw you a scrap. And Stanford, where Turner had been a graduate student, "butchers its young." At those institutions, preparation was everything.
At the DuPage County Center for Scientific Culture, however, preparation was nothing. To prepare a presentation for Primordial Pizza was to violate its most solemn and sacred tenet: Don't be afraid to be wrong. And that directive went for graduate students and visiting Nobel laureates alike. The riff was more important than the result. You got up and improvised. You jammed. You played cosmology as if it were jazz.
Turner had inherited that sensibility, he had come to realize, from the bongo-beating quantum theorist Richard Feynman at Caltech—even though Feynman was, as Turner had also come to realize, "the worst advisor." Sometimes Feynman would advise graduate students to pursue subjects that, while of interest to him, would turn out to be beyond their understanding, and they wouldn't be able to complete their theses; sometimes he would advise doctoral candidates to pursue subjects that—while, again, of interest to him—would turn out to be so obscure that they wouldn't be able to find postdoctoral fellowships. It was Feynman who had advised Turner to pursue his graduate studies at Stanford. Not until Turner got to Palo Alto did he realize that Feynman had suggested Stanford because it was the home of a linear accelerator that was performing particle physics experiments that were of interest to Feynman. "Feynman," Turner thought, "is interested in what Feynman is interested in, period."
What was Turner interested in? He didn't know. He was rooming with some medical students, and he had to ask himself, What was solving equations next to saving lives? He soon dropped out of graduate school and became a car mechanic. Earned $500 per study in drug experiments (marijuana, Valium) at the local Veterans Administration hospital. Worked weekends cleaning up after the one thousand animals in Stanford's research labs. If nothing else, these experiences instilled in him a deeper appreciation for the life he'd left behind—the life of the mind. And so, in time, Turner audited—or, at least, sat in the back of and took notes on—a course on general relativity.
General relativity wasn't quite right for him either. But at least the course got him back into the classroom, and back into physics. After Turner finished his dissertation, in 1978, the University of Chicago astrophysicist David Schramm called him with a postdoc offer. A few years earlier Schramm had found inspiration in Physical Cosmology, and since then he had been trying to yoke together the two topics that, individually, hadn't quite captured Turner's attention: particle physics and cosmology. Now Schramm said to Turner, in the same offhand manner that Bob Dicke had used with Jim Peebles when he suggested that Jim figure out the temperature for the cosmic microwave background, "Why don't you think about it?"
Turner talked it over with his doctoral thesis advisor at Stanford, the physicist Robert Wagoner. "That early-universe cosmology stuff? Don't do that," Wagoner told him. Wagoner himself had participated in the Big Bang revolution. As a postdoc at Stanford in the two years immediately following the discovery of the cosmic microwave background, he had worked on the same kind of primordial particle physics that Schramm had adopted in the following decade. But he had a point. By the late 1970s, the Big Bang bandwagon had stalled. It lacked the one thing that could save it from swinging back to the voodoo side of the metaphysics-physics continuum, the one thing any theory needs to be scientific: a prediction to verify or falsify.
Whatever Feynman's liabilities as an advisor, he had taught Turner this lesson: Don't try to solve a problem until you think you have the answer. That approach was the opposite of how particle physics usually worked. In particle physics, the math came first. The math told you that a particle should exist, and that you could create that hypothetical particle from existing particles. Then you (and a thousand colleagues) commandeered an accelerator and smashed those existing particles together at velocities approaching the speed of light and waited for the hypothetical particle to pop into existence.
Nothing wrong with that approach. It worked.
But Feynman had taught Turner that sometimes you didn't need to do the math first. Instead, you needed to trust your intuition. To leap to a conclusion first. To imagine what the universe might be, and then go back and do the math until, with luck, it matched.
To imagine what your life might be, and then go back and do the work until, with luck, it matched.
"Don't do that early-universe stuff," said his thesis advisor at Stanford. "Come to Chicago and do great things!" boomed Schramm.
Schramm made you think you could do great things. He was, in a way, the embodiment of cosmology: big and bold and fearless. His colleagues called him Schrambo or Big Dave. At 6 feet 4 inches and 230 pounds, he had the build of a former wrestler (which he was) and the bearing of an amateur pilot (ditto): king and conqueror of all he surveyed. When he decided to pursue the physics of the early universe during a period when the Big Bang was unfashionable, he not only made no apologies but claimed the field as his own. Big Bang Aviation, he named the corporation that controlled his private plane, of which he was sole proprietor. big bang read the vanity plates on his red Porsche.
Turner might not have responded to cosmology or particle physics in isolation, but the combination proved irresistible—a balance of the loud, wildly speculative, and the quiet, "neat and simple." In particle astrophysics, Turner could reconcile the two dominant tendencies of his life. The bohemian who dropped out, the intellectual who crept back. The incautious and the careful.
So Michael Turner would go to Chicago. And he might even get to do great things—just as long as cosmology came up with a prediction.
In October 1981, Golden Tickets appeared in the mailboxes of cosmologists around the world, only the wonderland they would be entering at the appointed day and hour wasn't Willy Wonka's Chocolate Factory but Stephen Hawking's Nuffield workshop. The Nuffield Foundation, a charitable trust, had agreed to endow an annual workshop for three years. In the second year, Hawking and Gary W. Gibbons, also at Cambridge, decided to consolidate the remaining funds and go all out: an assault on the farthest frontier of cosmology, the "very early Universe," which the invitation defined as "< 1 sec."
Among the three dozen or so theorists who received the letter was Turner. He figured that Hawking and Gibbons had known to invite him because one of his colleagues at the University of Chicago was one of Hawking's frequent collaborators. Not that there were all that many theorists working this particular corner of the cosmological landscape. And of course a good workshop should have a fair number of young minds to ward against the calcification of old ideas and received wisdom. But Turner would have to earn his ticket, too. He would be one of a handful of attendees who would be not just giving a talk but writing a paper.
On his arrival at Cambridge on the first day of summer 1982, Turner presented the preliminary draft of his paper to Hawking. Hawking nodded his thanks, then motioned to an assistant, who presented Turner with Hawking's paper. A couple of other papers were circulating as well. The time had come to confront a question that had been haunting cosmology right from the day that Einstein extended general relativity to the universe: Why was the universe simple?
As the letter from Hawking and Gibbons had said, Big Bang cosmology "assumes certain initial conditions." Those assumptions, however, were notoriously ad hoc, from the Latin for for this. As in: For this purpose—the creation of a cosmological model from the general theory of relativity—Einstein assumed homogeneity, that the universe looked the same on the largest scale. For this purpose—the creation of a cosmological model that wasn't static—other theorists had added the assumption of isotropy, that the universe looked the same in every direction.
And the universe did seem to be homogeneous and isotropic. The discovery of the cosmic microwave background seventeen years earlier had satisfied most cosmologists that they now had the answer to the question of whether the universe was simple: Yes. On the largest scale it would look the same no matter where you were in it. And they had answered the question of how simple the universe was: Very. The cosmic microwave background was extremely smooth, just as theory had predicted.
But assuming that something is the way it is—even if those assumptions turn out to be correct, as the Big Bang theory's apparently were—is no substitute for understanding how it got that way. Why would a universe be, of all things a universe could be, simple—and not just simple, but so simple? On reflection, maybe the answer to the question of how simple the universe was shouldn't have been the satisfying "Very" but a suspect "Too."
Now, however, cosmology had a possible answer to the question of how the universe became so simple. Late in the evening of December 6, 1979, a no-longer-young academic with a boyish mop of hair, a boyish smile, and a grown-up worry about meeting the monthly rent sat down at the desk in his study, as he often did at that hour of the day. On this occasion, however, Alan Guth received a midnight visit from the Muse of Math. The next morning he bicycled to his office at the Stanford Linear Accelerator Center (in the process establishing a new personal best of nine minutes and thirty-two seconds) and immediately sat down with his notebook to summarize his long night's work.
"spectacular realization," he wrote near the top of a fresh page, and then he did something he'd never done before with a notebook entry. He drew two boxes around it.
By the time of the Nuffield workshop, two and a half years later, the story was already the stuff of scientific legend. Guth had experienced a genuine "Eureka!" moment. His was the kind of insight that causes colleagues to slap their foreheads and groan, "Of course!" The day after Guth gave his first seminar on his spectacular realization, in January 1980, he received calls from seven institutions either inviting him to give the same seminar or asking if he would consider a faculty position. By then Guth had given his idea the name that stuck: inflation, a pun that accommodated both the defining physical property of his discovery and the dominant economic worry of the era.*
According to his calculations, the universe had gone through a monumental expansion in its first moment of existence. At the age of a trillionth of a trillionth of a trillionth of one second—or 1/1,000, 000,000,000,000,000,000,000,000,000,000,000th of a second—the universe had expanded ten septillion-fold—or to 10,000,000, 000,000,000,000,000,000 times its previous size.
The suggestion followed an idea that another physicist, Edward P. Tryon, had put forward several years earlier, in a 1973 article in Nature. Like Gamow with "Rotating Universe?"—the Nature article that had partly inspired Vera Rubin's master's thesis—Tryon couched the counterintuitive in the form of a question: "Is the Universe a Quantum Fluctuation?" According to the laws of quantum mechanics, virtual particles can arise out of the emptiness of space—and actually do, as experiments since the middle of the century had shown again and again. Tryon wondered if the universe might be the result of one such quantum pop.
The argument became less sensational if you kept in mind that in quantum theory everything was a matter of probabilities. Therefore, anything was possible. Perhaps specific events were vanishingly unlikely—the creation of a universe from the nothingness of the vacuum, for instance. But they weren't impossible. And over the course of eternity, why shouldn't one or another of those vanishingly unlikely events come to pass? The universe, Tryon wrote, "is simply one of those things which happen from time to time." Or, as Guth liked to say, "the universe is the ultimate free lunch."
The problem with Tryon's idea was that it couldn't account for the size of our universe. Inflation, however, could. Guth realized that the infant universe could have gone through a process that physicists call a "phase transition" and everybody else calls "the thing that happens when water turns into ice or vice versa." When the temperature of water changes, the transformation doesn't happen all at once. It's not as if the word goes out and suddenly every molecule of H2O in the lake has melted into liquid or hardened into ice. Instead, the transformation happens piecemeal. Even within small sections of the pond the ice isn't freezing or melting uniformly. Cracks and fissures appear faintly, then harden, leaving a veined appearance. Guth found that if you apply that transformation mathematically to the conditions of the early universe, the phase transition would have produced a temporary vacuum. That vacuum, in turn, would have produced a negative pressure—a strong gravitational repulsion—that would have expanded space exponentially. The universe would have doubled in size, then doubled in size again, then doubled in size yet again. It would have done this at least a hundred times, and it would have done so over the course of 10−35 seconds (or 1/1035). After that, the vacuum would have decayed, the exponential expansion would have stopped, and the standard expansion of the universe—the one in the Big Bang theory that we can see for ourselves in the redshifting of the light from distant galaxies—would have begun.
At once Guth recalled a lecture by Bob Dicke that he had attended the previous year, one of a series that Dicke and Peebles had been delivering on a topic they called the "flatness problem." They would explain to their audiences that the fate of the universe depended on how much matter was in the universe: enough to reverse the expansion, not enough, or just right. The designation that scientists had given to the measure determining the fate of the universe was, aptly, the final letter in the Greek alphabet, omega. If the universe contained half the mass necessary to halt the expansion, then you would say omega equaled 0.5, or if it contained three-quarters of the necessary mass, you would say omega equaled 0.75. If the universe contained more than enough mass to halt the expansion, then omega equaled more than 1—1.5 times, maybe, or 2 times, or 100 times. And if the universe contained just the right amount—precisely the critical density to stop the universe from expanding but keep it from collapsing back on itself—then omega equaled 1.
Astronomers would even be able to measure omega, if they had a standard candle that they could trace far enough across the universe. But you might not need observations to know omega, Dicke argued. Theory alone might be enough.
According to Dicke, any significant deviation from 1 in the earliest universe would have led, effectively and almost immediately, to the end of the universe: either an exponential expansion toward infinity or a collapse. Calculating backward, the closer and closer you got to the Big Bang, the closer and closer omega must have been to 1. At three minutes after the Big Bang, omega would have been within a hundred-trillionth of 1. At one second after the Big Bang, omega would have been within a quadrillionth of 1—that is, between 0.999999999999999 and 1.000000000000001. The earlier in the universe you calculated, the more decimal places you added. At some point in the calculations you simply conceded: Omega as good as equaled 1.
And if omega equaled 1 then, it had to equal 1 now, because the value of omega depended on the measure of matter, and whatever matter the universe had then, it would have now and forever.
But for Big Bang theorists like Dicke and Peebles, a flat universe posed a problem similar to the one Newton and Einstein faced: Why would a universe that was full of matter not be collapsing through the effects of gravity? Newton had to invoke a universe of evenly spaced stars—plus God. Einstein had to invoke a universe of randomly spaced stars—plus lambda. Evidence for an expanding universe had allowed Einstein to abandon lambda and prompted future generations to try to figure out how to measure the rate at which the expansion was slowing. But now Dicke and Peebles were arguing that in a Big Bang universe, omega had to equal 1. The expansion had to slow to a virtual stop and stay there forever. All the matter in the universe had to reach a state of gravitational equilibrium—an eventuality with the same likelihood as a pencil standing on its point forever. Not impossible, according to the laws of classical physics, but not likely either.
But that December night in 1979, Guth realized that if inflation did occur and the entire universe was actually ten septillion times the volume of what we see, then what was flat wasn't the universe but only our part of it—the part we'd always assumed to be the universe in its entirety. Our part of the universe would appear flat to us, just as a football field appears flat even though the Earth is round. The universe as a whole could have any value of omega; the universe that we see, however, has a value close enough to 1 that, for all practical purposes, it may as well be 1.
So much for the flatness problem.
A few weeks after inventing inflation, Guth was listening to some colleagues at lunch and learned about another apparent contradiction in a homogeneous and isotropic universe, the "horizon problem." Look into the universe in one direction, then look into the universe in the opposite direction. This is essentially what antennas measuring the cosmic microwave background do. The light from one direction will just be reaching you, and the light from the other direction will just be reaching you, but the light from the first source will not yet have had time to reach the second source, and vice versa. Yet the cosmic microwave background reveals a similarity in temperature to within one part in 100,000. How did one part of the universe "know" the temperature of the other and match it if the two had never "communicated" with each other?
"Yeah," Guth thought, "inflation could solve that, too." If inflation did occur, then two distant parts of the universe would have been in contact with each other when the universe was less than 10 seconds old. Guth thought a little more. Then he told himself, "This really might be a good idea after all."
Guth's paper "The Inflationary Universe: A Possible Solution to the Horizon and Flatness Problems" appeared in early 1981. While the Nuffield workshop was officially called "The Very Early Universe," it quickly became a referendum on inflation. Seventeen of the thirty-six sessions addressed the topic directly, and many of the others mentioned it.
The question wasn't so much whether inflation made sense. Inflation explained two ad hoc assumptions—homogeneity and isotropy. It solved two problems—flatness and the horizon. It was too good not to be true—or at least that's how many of the theorists at Nuffield felt. The question instead was whether they could fix its flaws.
Guth's original idea was plagued by a problem that he himself hadn't identified. Once his version of inflation started, it couldn't stop. Other theorists—Andrei Linde, at the Lebedev Physical Institute in Moscow, and, independently, Paul Steinhardt and Andreas Albrecht, at the University of Pennsylvania—identified the problem and found the solution. They reconceived the inflationary period to be, as Guth came to think of it, less like the bubbling of boiling water than the congealing of a single Jell-O bubble. The problem with the one-bubble inflationary model, however, was that it still had to account for the visible universe—homogeneous and isotropic, but not toohomogeneous and isotropic, or else we wouldn't be here.
They were all borrowing from Hawking. In 1973 Hawking had redefined the study of the early universe with his work on black holes; he found that, owing to a combination of quantum and gravitational effects, they weren't one-way tickets to a singularity. At the edge of the event horizon—the black hole's ring of no return—quantum effects dictated that particles and antiparticles would be popping into existence, while gravitational effects dictated that one partner would disappear into the black hole but not the other. Rather than annihilating each other "immediately," one would slip over the edge, into the black hole, but the other would escape into space and the universe as we know it. Black holes, Hawking contended, aren't black after all. They leak radiation—Hawking radiation, as it came to be called.
In effect, Hawking had begun to bridge the two seemingly irreconcilable theories of the twentieth century, quantum mechanics and general relativity, a necessary step if science was ever going to describe the earliest, foamiest time after the singularity, or perhaps even the singularity itself. Two years later, Hawking and Gibbons extended the concept of quantum gravity to the universe as a whole and found that it would fill with thermal fluctuations. In early 1982, in the months leading up to Nuffield, Turner and Paul Steinhardt had begun working on the idea that those fluctuations could have been present during the inflationary period.
For Guth and Turner and some of the other attendees, Nuffield was the latest stop on what they'd come to regard as a "traveling circus" of cosmologists. In early 1982 they had attended conferences in London, the French Alps, and Switzerland. In April, Steinhardt and Hawking happened to be visiting the University of Chicago at the same time; head-scratching with Turner inevitably commenced. In May, Steinhardt visited Harvard; Guth biked over from MIT. In June, just two weeks before Nuffield, Hawking gave a lecture at Princeton; Steinhardt drove over from Philadelphia, then called Guth and Turner with the latest update on new inflation.
The conference at Nuffield was like that, only more condensed, more intense. Gibbons and Hawking had limited the schedule to two seminars most days, leaving the rest of the time for "informal discussion." And discuss they did. The participants talked during day trips to London. They talked over croquet and tea on the lawn at Hawking's house. They talked long into the night, knocking on one another's doors. And as they talked, the conception of inflation shifted, and shifted, and shifted again. For Turner, Nuffield was shaping up to be one of those rare cosmological events: "a workshop where work actually got done."
During his own talk, Turner tried to capture the breakneck exchange of ideas by adopting the tone of a TV newscaster and recapping the workshop so far in a series of "this-just-in" bulletins. He got laughs, but he also made a point: Even being able to analyze the problem was progress of a sort. Had they made new inflation work? No. But they had agreed on a way that they might make it work. Now they knew they had the right equations, even if they hadn't yet figured out how to solve them. They'd managed to wrest the universe back from being "too" simple—ad hoc simple—to being merely "very" simple. They'd even managed to convince themselves that cosmology came with a prediction: The universe was flat.
"Child's play," Turner thought. Now came the hard part—and the fun.
What was inflation—what was Nuffield—if not an exercise in a Feynman kind of faith? Cosmologists in the early 1980s had leaped to a conclusion, embracing inflajion simply because it explained and solved so much, and then they had gone back and labored to make the math work. And they'd succeeded. In the weeks following Nuffield, Turner and the other attendees reached a consensus on the equations for the new inflation, and cosmology suddenly had a new standard model: not just Big Bang, but Big Bang plus inflation.
Consensus, however, does not a science make. The work would continue—the tweaking and rethinking that Feynman's kind of faith eventually required. The whole field would be doing that tweaking and rethinking. The difference for Turner and Kolb was that they would be doing it Schramm-style—and with Schramm substance.
In the summer of 1981, during a hike in the Dolomites, Schramm and Leon Lederman, the director of Fermilab, discussed the idea of founding an institute devoted to the scientific intersection that Schramm had been championing for the previous decade: particle physics and cosmology. The idea was somewhat radical; as Turner said, "The two disciplines had little in common, other than indifference for one another." But NASA (perhaps as a consolation prize for awarding the Space Telescope Science Institute to Johns Hopkins rather than Fermilab) agreed to fund it, and Lederman and Schramm hired Turner and Kolb to run the NASA/Fermilab Astrophysics Center.
"The Big Bang," Schramm often said, quoting Yakov Zel'dovich, a Russian theorist, "is the poor man's particle accelerator." Accelerators on Earth could approach the energies of the earliest moments in the universe—the earlier the moment, the higher the energy—but they couldn't match the earliest, most energetic moments. Even if you wanted to reach a time and a level of energy that an accelerator could match, it wasn't the kind of instrument you could walk down the hall and borrow for the afternoon. What you could do instead was perform the calculations on how certain particles at certain temperatures would behave, and then see whether those calculations matched the observations of elements in the universe today.
The idea itself wasn't new. Gamow, Ralph Alpher, and Robert Herman had tried to perform those calculations in the late 1940s, working from the assumption of a Big Bang universe. Fred Hoyle had tried to perform those calculations too, working from the assumption of a Steady State universe. The Big Bangers' calculations could account for the approximately three-quarters hydrogen and one-quarter helium abundances in the universe but not the 1 percent heavier elements. The Steady Stater had the opposite problem—able to account for the creation of the heavier elements but not hydrogen and helium. The twin impasse did nothing for cosmology's reputation.
In 1957, however, the physicists Geoffrey and Margaret Burbidge, Willy Fowler, and Fred Hoyle collaborated on a 104-page tour de force in the journal Reviews of Modern Physics that did for the origin of elements what Darwin had done nearly a century earlier for the origin of species. B2FH, as scientists came to refer to the four collaborators, had worked for eighteen months in a windowless room in the Kellogg Radiation Laboratory at Caltech, scribbling on a blackboard, taking Baade and Zwicky's 1930s studies of the inner workings of supernovae to their logical conclusion, figuring out how nuclear reactions in successive generations of stars had ripped apart the basic building blocks of matter and put them back together in new and more complex combinations. Just as Darwin explained how single-cell creatures could evolve into species upon species, B2FH explained how single-proton atoms could eventually form the elements in the periodic table. As they phrased their conclusion, echoing Darwin's last line in On the Origin of Species, "The elements have evolved, and are evolving."
Gamow, Alpher, and Herman hadn't needed to account for the heavier elements after all. The hydrogen and helium they could account for were plenty, and then B2FH's supernovae would take over and produce the heavier elements. Following the discovery of the cosmic microwave background and the resurgence of interest in the Big Bang, physicists including Fowler, Hoyle, and Wagoner got to work on refining the calculations. The difference now for Schramm, and for the Fermilab Astrophysics Center he was deeding to Turner and Kolb, was that he wanted to get the physicists of the very small and the physicists of the very big talking to one another as if they belonged to one discipline—in fact, to create that discipline.
At once, Turner and Kolb started organizing "Inner Space/Outer Space," a conference that would advance the Schramm vision as well as the Schramm aesthetic. They adopted a logo that showed bubble-chamber tracks superimposed on a photograph of a galaxy, and they plastered it on souvenir T-shirts. They organized a jog around the accelerator track, the two hundred participants lumbering like bison. They showed off the buffalo that roamed on the Fermilab prairie. They hosted a "Buffalo Class* (*or equivalent protein material)" picnic, and advertised it with posters promising a talk by "J. Fonda* (*or equivalent protein material)." In the subsequent publication of the proceedings, they reproduced that poster and other whimsical drawings by Turner. And they included an afterword that doubled as a manifesto.
"Cosmology in the 20th century," they wrote, "has been hampered by a lack of confidence on the part of cosmologists, often leading to missed opportunities." Einstein lacked the courage of his equations: He missed predicting the expanding universe. A later generation lacked the courage of Gamow's equations: They missed discovering the cosmic microwave background. Their generation, Kolb and Turner vowed, wouldn't make that mistake. "Whatever future cosmologists write about cosmology in the 1980s, we can be certain it will not be that the cosmologists of this era were afraid to take even their wildest ideas seriously," they concluded. "We remain ever optimistic!"
The proselytizing continued (Turner even referred to NFAC as "the 'mother church'"). In 1989, Kolb and Turner published The Early Universe, a volume that they hoped would do for particle astrophysics and cosmology what Peebles's book had done for physics and cosmology, and then some. "Perhaps future cosmologists will laugh at our naïveté," they wrote in the "Finale" of the book. "But, if they do, we can hope they will admire our courage and boldness in attacking problems once thought to be beyond the reach of human comprehension. The extent to which we shall be rewarded for our courage and boldness remains to be seen. These authors," they concluded, "remain ever optimistic!" For the publication of the paperback edition they included a fresh preface: "Despite being four years older," they wrote, "we are no less optimistic; we are, in fact, even more optimistic!" And in recognition of their increasingly iconic presence in the community, they signed the preface "Rocky and Mike."
Fine: Be loud. Shout out your ideas. Crazy is okay, and the crazier the better. Snatch the chalk from your colleague. Standing to one side, leaning against a bar in a paneled basement, Schramm presumably appreciated the intellectual food fights on those Primordial Pizza nights.
But then: Be quiet. Cool off. Go back to your office in the morning and take out your notebook and refine the crazy idea until you've found the immovable math. And make sure that that math makes a prediction that someone can actually go out and verify. "Schramm's razor," his colleagues called this insistence on a verifiable prediction. And now cosmology had a prediction: The universe was flat.
So where was the evidence?
The "Inner Space" had changed over the years. In Schramm's original vision, inner space referred to particle physics, and he and his colleagues had succeeded in beating down the processes of element formation to what they called the "era of nucleosynthesis"—the period when the universe was between 1 second and 100 seconds old and the cosmic fog had cooled enough to allow the formation of elements. They knew what should have been happening in the previous fraction of a second, when protons and neutrons and electrons were ricocheting. But Hawking and Guth had changed the game; they came at the universe from the other end—not from the present backward but the beginning forward. They took into account not only particle physics but quantum physics. If inflation was right, then the quantum jiggling during the inflationary period—all 10 seconds of it—had frozen into the fissures in the cosmic pond, the veins in the ice, creating the structure around which matter (dark or not) had clustered, leading to the universe we see today.
But that "Outer Space" had been changing too. Long gone was the era of arguing over the Rubin-Ford effect—the data that Vera Rubin and W. Kent Ford had collected in the mid-1970s that seemed to show local galaxies not just receding in the expansion but moving en masse in a common direction. In 1976, the same year that Rubin and colleagues published the paper on the Rubin-Ford effect, a team led by Richard Muller and George Smoot at LBNL had taken a suggestion by Peebles in Physical Cosmology and, planting a Dicke radiometer aboard a U-2 plane, tried to measure the motion of our galaxy against the cosmic microwave background to determine whether the universe as a whole rotates. What they discovered instead was that our galaxy seemed to be racing through space at nearly 400 miles per second. Smoot made the announcement in April 1977 at an American Physical Society meeting during time that Peebles had yielded to him from his own talk. The phenomenon "is a real dilemma for theorists," Peebles said, and Smoot suspected that the two of them were the only physicists in the room who understood the implications: For the universe to contain such local volatility yet still appear homogeneous and isotropic on a large scale, that scale was going to have to be much larger than anyone had ever imagined.
That same year, Jim Peebles compiled a map of the millions of galaxies that the Lick Observatory had observed and found that not only did galaxies seem to be doing what galaxies interacting gravitationally with one another would be doing—clustering—but the clusters seemed to be doing what clusters interacting gravitationally with one another would be doing—superclustering. In 1981 Allan Sandage and Gustav Tammann announced that Gérard de Vaucouleurs (and, by extension, Rubin) had been correct: The Milky Way itself belonged to a local supercluster—indeed, the Local Supercluster, as de Vaucouleurs named it. That same year, a group including Robert Kirshner discovered evidence of the residue that clumping galaxies left behind: a "Great Void." The following year, another collaboration found that the Great Void wasn't so great; it was rather typical: "the superclustering phenomenon is widespread and accompanied by large holes in space that appear to be quite deficient of galaxies." A broader and deeper survey of galaxies by a Harvard Center for Astrophysics collaboration electrified astronomy by identifying a supercluster "Great Wall"—a filament of galaxies. But the Great Wall, too, in time came to seem typical, as redshift surveys continued to expand their reach. The pattern was consistent: The broader the slice of space, the longer the filaments; the longer the filaments, the greater the voids.
The scale itself of such structures presented a challenge for dark-matter theorists. Their simulations and calculations could show galaxies and clusters forming in the proper proportion in the distant past, but then the superclusters wouldn't have had time to develop later to the extent that observers were finding. Or their models could show superclusters having formed in the proper proportion in the recent past, but then the galaxies and clusters would have had to develop earlier to a greater extent than observers were finding. Still, for Turner and Kolb's purposes, at least the distribution of galaxies was, as one paper from this period reported, "frothy."
Did the galactic froth of Outer Space match the quantum jiggles of Inner Space? Since the discovery of the cosmic microwave background in 1965, the fate of the Big Bang theory had hung on the future detection of anomalies in the otherwise smooth bath of radiation—the inhomogeneities that had to be there in order for us to be here.
Was the universe flat? Since the invention of inflation in 1979, the fate of the quantum interpretation of those inhomogeneities had hung on the future detection of flatness.
In the early 1990s, Turner and Kolb and every other cosmologist who had been waiting for years got their answers to these two questions—sort of. The Cosmic Background Explorer (COBE) satellite, launched in 1989, had been designed to make those two measurements at an unprecedented level of sensitivity—a level so sensitive that many scientists (including Turner) doubted that the experiment could work.
In 1990, John Mather announced that COBE had measured the spectrum of the microwave background and found it consistent with Penzias and Wilson's detection more than two decades earlier, and refined the measurement of the temperature to 2.735 K (plus or minus 0.06 K). In 1992, Smoot* announced that COBE had detected the wrinkles in the radiation in a proportion to match the predictions of inflation. The universe was flat.
Or not. At Princeton, for instance, Ruth Daly was using radio galaxies—galaxies spitting out plumes of plasma to either side so that they look like barbells—as standard yardsticks. Like astronomers using supernovae as standard candles and hoping to see supernovae brighter (and therefore nearer) than they "should" be at cosmological distances, Daly and some other astronomers were hoping to see radio galaxies longer (and therefore also nearer) than they "should" be. Her preliminary observations corresponded to an omega of 0.1—one-tenth the density necessary to close the universe. Also at Princeton, Neta Bahcall was studying clusters of galaxies, hoping to extrapolate from their masses and distribution to "weigh" the universe. Her preliminary observations corresponded to an omega of 0.2—one-fifth the density necessary to close the universe. The universe according to Daly and Bahcall was open.
The universe was flat. The universe was open.
And that's where cosmology rested as the decade stretched on: a neither-nor state of suspension that would have to await further observations, a Pinteresque pause of cosmic proportions.
Late in 1997, this impasse assumed an importance beyond the professional for David Schramm when he received an invitation to participate in an event at the Smithsonian Institution's National Museum of Natural History. It would take place in April 1998, and it would feature a "Great Debate" between Schramm and Jim Peebles on whether the universe was flat. Such debates don't necessarily depend on the convictions of the participants; they're more rhetorical in nature. Still, Schramm's competitive side meant that he didn't want to simply score points. He wanted to be right. He wanted to know the value of omega.
He wanted to know what Saul Perlmutter knew.
For several years, Perlmutter's group had been promising a precise measurement of omega using Type Ia supernovae as standard candles. They had published several papers with hints of results, and now word was coming out of California that they were grabbing supernovae by the dozens, that they had gotten time on the Hubble Space Telescope, that they might be on the verge of delivering a verdict.
"What's Saul getting?" Schramm would say, winging past Turner's office. Then, a few days later: "What's Saul getting?"
Turner told him they might all find out soon enough, at the AAS meeting in January. Saul would be making a presentation. The other team would be making a presentation. All they could do now was go home for the holidays and wait.
Late in the evening of December 19, Michael Turner got a call. It was Judith, Schramm's wife. She was at their home in Aspen, waiting for her husband, who was supposed to be flying there in his Swearingen SW-3, but he was hours late, and now there was a report on the local news about a plane crash.
Turner said something reassuring, and he and Judy promised to stay in touch. Even after she called back later, Turner found it impossible to believe that David Schramm had not survived the plane crash, had not wrested his impressive frame from the wreckage, was not even now wandering a field in the snow and the cold and the dark.