That increase in photometric precision was crucial. At the time, it was perhaps the only justification for using HST on a supernova search. As everyone in astronomy knew, the purpose of HST was to perform science you could do only from space. The two distant supernova teams had proven that you could do their science from the ground—not as well as you could do it with HST, but you could do it nonetheless. What Perlmutter would need from Williams, then, was a slice of Director's Discretionary Time, a perk that routinely comes with the title of observatory director.
Williams said the idea sounded promising. He suggested that Perlmutter submit a proposal. A month later, Perlmutter did.
Williams, however, was no expert on the subject of distant supernova searches. Few people were, and with the exception of some Danes, nearly all of them were on one of the two competing teams. Three months later, at the annual May symposium at the institute, the SCP proposal came up during an open discussion. Bob Kirshner was in the audience. He had served on an HST Time Allocation Committee that had considered a similar proposal from SCP, and he had advised against it if only because the mission of HST was to do astronomy you could do only in space. He began to object, but Williams said they would continue the discussion in private. At the next break, Williams ushered Kirshner as well as Mark Phillips and Nick Suntzeff into his office.
"Is this a good idea?" he asked.
Kirshner immediately spoke up.
"No," he snapped. "It's the wrong idea." The point of a space telescope, he reminded Williams, was to do observations that you couldn't do from the ground. That was what the Observing Proposal paperwork said. That was what the previous STScI director had always insisted.
Williams listened. Then he said, "Yes, but I'm the director, and I can do what I want. This is really good science, and I think the Space Telescope ought to do anything that's really good."
Kirshner disagreed, and he and Williams went back and forth like this for a while. Occasionally Phillips and Suntzeff spoke up, echoing Kirshner's arguments. Still, the three High-z members knew what was at stake: If Saul got HST time, that could well be the game. And clearly Williams wanted to give HST time to Saul. He didn't want to hear the argument that nobody should be using HST to do follow-up photometry on distant supernovae. He wanted the best science to come out of HST. He wanted the best science to come out of his telescope.
Maybe they all realized it at once. Maybe they realized it one at a time. But at some point each of the three High-z members at the meeting understood what Williams was really saying. If they asked for HST time, right then and there, they'd get it too.
They asked.
"My God, what an idiot!" Suntzeff thought as he left Williams's office. "Instead of pushing for the science that I want, I'm trying to argue, for moral reasons, about why we shouldn't be getting the data that we want! How stupid can you get?"
From the West Coast, the SCP watched agog. The dots weren't difficult to connect. Bob Williams had been director of Cerro Tololo from the mid-1980s to 1993. Mark Phillips and Nick Suntzeff had worked at Cerro Tololo under Williams. Bob Kirshner had served as an advisor to Cerro Tololo during this period. If you wanted to see evidence of an old boys' network, you didn't have to look very hard.
Bob Cahn, the director of the Physics Division at LBL, got on the phone with Kirshner and yelled for a while. He got on the phone with Williams and yelled for a while.
Williams responded calmly, trying to explain his reasoning. HST was an important resource, and the search for high-redshift supernovae was a new field, and HST would surely get better results if both groups used it for their nearly identical experiments.
Cahn replied that he was familiar with important resources. He explained that high-energy physics, too, uses an important resource. He reminded Williams that this important resource was one that LBL had helped invent: the gigantic particle accelerator. But when a group applied for time on a gigantic particle accelerator, the proposal was confidential. Wasn't that how astronomy worked?
Williams conceded that that was indeed how astronomy worked, usually. He suggested a compromise. Both teams would receive Director's Discretionary Time, and the SCP would get to go first.
Cahn and Perlmutter had no choice but to accept. Afterward, though, whenever SCP team members talked among themselves about their rivals, they did so with a new appreciation of just how formidable they were. In the culture of high-energy physics, scientists have to work in large collaborations, and those collaborations have to endure for a long time. You can't afford to alienate your competitors, if only because they'll soon be your collaborators. Astronomers, however, still roamed some Wild West of the mind, where resources were scarce, competition was fierce, and survival depended on small alliances of convenience, often enduring just long enough to publish a paper. Astronomers could afford to play for keeps.
Not that high-energy particle physicists weren't competitive. But in the end they had to get along if they wanted to get work done. They could be tough. But next to astronomers, they were, said one SCP partisan, "pussycats."
By the autumn of 1997, the two teams had enough data to try to find at least a preliminary answer to how much the rate of expansion of the universe was slowing down, and therefore whether the universe was heading toward a Big Crunch or a Big Chill.
As part of the High-z team's fast-and-fair philosophy, Schmidt had divvied up the responsibilities not only institution by institution but junior astronomer by junior astronomer. In this game of tag, the Australian National University Mount Stromlo and Siding Spring Observatories' Schmidt was "it" first. He would write up the paper broadly introducing the collaboration's methods and goals. Then the team tagged Harvard and Peter Garnavich; he would take the three Type Ia supernovae that the team had measured photometrically with HST in the spring of 1997, add 1995K, and try to figure out a value for the Hubble constant. Just as important, the paper would help justify requests for more HST time.
On the SCP side, no one person was working exclusively on the problem. In keeping with the particle physics culture, the team was moving forward collectively. In fact, they'd already moved forward; a year earlier they announced the results from the first seven Type Ia, which suggested that the universe was flat—neither expanding forever nor eventually contracting. But the margins of error and the size of the sample were such that the result was preliminary at best.
Or wrong, as the team was beginning to suspect, on the basis of the one supernova on which they had managed to conduct reliable HST photometry. That one "guy," as astronomers like to call a piece of evidence, was indicating a possible shift in another direction, toward an open universe.
One approach astronomers could use in trying to make this determination was a histogram. On the morning of September 24, Gerson Goldhaber sat at his desk at LBL to prepare for the weekly team meeting. Unlike a graph, which plots each individual point of data, a histogram gathers several pieces of data at a time and "bins" them in categories. That morning, Goldhaber took each of the thirty-eight SCP supernovae so far and, based on its brightness and redshift, put it in a column corresponding to the amount of matter that this one supernova suggested the universe needed in order to slow the expansion to a halt: 0 to 20 percent of the necessary mass density, 20 to 40 percent, and so on, up to 100 percent. When he was done, the two tallest columns by far, one of them bulging with ten supernovae and the other with nine—half the total sample—told him that not only did the universe not have enough matter to slow the expansion to a halt, it had 0 to negative 40 percent.
"Lo and behold," he said to himself.
For the High-z team, Adam Riess was working on a statistical approach to the problem. His task was to take all the supernova data collected so far—all the pixels of spectroscopy and photometry, all the galaxy subtractions, all the light curves, all the margins of error—and develop software that would compare it with millions of different models of the universe. Some of those models would be absurd: relationships between magnitudes
and redshifts that, on a sheet of graph paper, would fall far from the straight, 45-degree line, off in remote corners where the punch holes were. Other models, however, would match slight deviations from that seemingly straight line. Within this subset, some models would match even slighter deviations, even subtler departures from the "norm." One of those universes would match his data.
And one did. It was a universe that not only didn't have enough matter to slow the expansion but had a mass density of negative 36 percent. It was a universe without matter. It was a universe that didn't exist.
"Lo and behold," Riess told himself.
Both teams had been operating under the assumption that the universe was full of matter and only matter. They knew some of it was dark, of course, but what was missing was still fundamentally matter. They had therefore assumed that only matter would be influencing the expansion of the universe.
Abandon those assumptions, however, and these seemingly nonsensical results might make sense after all. If the two teams considered a universe in which something else was affecting the expansion—a universe that consisted of something other than matter—then the universe would have matter in it again. They looked at the error bars and figured that the matter, dark or otherwise, was maybe 20 or 30 or 40 percent. Which left 60 or 70 or 80 percent ... something else.
As for the fate of the universe: They had their answer. Maybe even the answer—one they could quantify: It would expand forever.
What they didn't have—between the dark matter they couldn't see and this new force they couldn't imagine—was any idea what the universe was.
PART III
The Face of the Deep
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 woul
d 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?"
The 4-Percent Universe Page 14