The 4 Percent Universe

by Richard Panek

  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.

  8. Hello, Lambda

  ON JANUARY 8, 1998, four astronomers sat at a table at the front of a conference room at the Washington Hilton to deliver the verdict of science. Ruth Daly was there with her radio-galaxy data, and Neta Bahcall was there with her galaxy-cluster data, and representatives from the two supernova teams were there—Peter Garnavich for the High-z collaboration, and Saul Perlmutter for the SCP. The press re-leases from the various institutions had done their job. A couple of dozen journalists filled the seats, including reporters from the New York Times and the Washington Post, and cameras on tripods lined the back of the room, their metal lamps throwing light and heat. The four astronomers represented four independent collaborations, but they spoke with one voice: The universe would expand forever.