It seems doubly odd that Lambda is roughly equal in density to the matter in the universe—within a factor of two, at least. Matter gets diluted as space expands, but each bit of new space contains more Lambda, which begets more Lambda, and so on. Early in the universe, the matter density would have been millions of times as great as Lambda. In the far future, the roles will reverse. Right now, for a very short period in the overall history of the universe, the two are roughly equal, so the cosmos is experiencing only a subtle acceleration. Schmidt finds the coincidence hard to swallow: “It's just bizarre to me that by chance we're living in a time when these things are roughly balanced. If we'd lived five billion years ago, we couldn't even measure Lambda, and five billion years in the future it would be screamingly obvious.” This is exactly the kind of fine-tuning inflation was supposed to get rid of.
Always eager to press on toward deeper cosmic understandings, theorists have cooked up a new kind of dark energy that has more appealing attributes than the vacuum fluctuations, called “quintessence.” The name refers back to the Greek theory of matter, in which the earth is composed of four basic elements but the heavens of an elevated, more perfect “fifth element.” The name deliberately evokes Aristotle's ether, describing that extra intangible that explains why the universe moves. In its modern incarnation, quintessence is something that is not matter but isn't exactly energy in the usual sense, either. Paul Steinhardt at the University of Pennsylvania, who collaborated with Guth in creating a workable theory of inflationary cosmology, is the leading champion of quintessence. Even he has a hard time explaining what it is in simple terms, however: “a slowly varying, spatially inhomogeneous component” or “a scalar field slowly evolving down its potential.” Again, the words are new, but the impulse is old. It is the endearingly optimistic sci/religious hope that one more mystical element will pull the whole cosmic explanation together.
A scalar field is one that has magnitude but, unlike an electric field, for instance, has no direction. The energy just sits there, piled up in space. It is somewhat analogous to the electric charge that builds up when you walk along a carpet on a dry winter day. Your body is full of energy, but you don't feel it. It just stays in place, at least until you disturb the system by doing something like touching a metal doorknob and get a nasty shock. According to the latest thinking in physics, space may be full of energy in the form of scalar fields, which regulate the rules governing subatomic particles and may even give those particles their masses. Indeed, the energy that presumably caused inflation in the early universe came from a scalar field.
The primary appeal of quintessence is that it does not have to stay at a fixed value, unlike vacuum energy. In some of Steinhardt's models, quintessence decreases in energy as the universe expands, tracking the thining out of the universe. It may not be a coincidence that the cosmic matter and energy densities are similar; they might be linked to one another physically. And Steinhardt does away with the mystery of how the vacuum energy almost, but not exactly, shrinks to zero. He simply argues that the energy really is zero because of some fundamental property that cancels out the effects of the quantum fields, as most physicists have long assumed, and proposes instead that quintessence drives the observed cosmic acceleration.
Even by today's cosmological standards, this is deep prayer in the Temple of Einstein: unknown effects controlling the vacuum energy, unknown fields creating quintessence, unknown effects linking quintessence to the matter density of the universe. Hardcore observers like Kirshner bristle when Steinhardt's name comes up. “Some of us would like some scintilla of evidence,” he crows.
Yet the two men share a similar core of epistemological faith—Steinhardt that he can deduce ultimate truth, Kirshner that he can hope to see it. Further studies of supernovas from the ground will not help much here. Cosmologists are pinning their hopes on two orbiting telescopes. NASA's Wilkinson Microwave Anisotropy Probe, launched in 2000, has already bolstered the evidence for dark energy and has pinned down the age of the universe: 13.7 billion years. The European Space Agency's Planck spacecraft will follow up in about four years. These satellites contain instruments to scrutinize the cosmic microwave background in excruciating detail. The resulting maps should be able to distinguish between quintessence and Einstein's Lambda and to throw out some of the inflationary cosmology models by revealing a great deal about the state of the universe very soon after the big bang. Meanwhile, the various supernova researchers are promoting SNAP—the Super-Nova/Acceleration Probe. This satellite will provide vastly improved measurements of Lambda and other astrophysical phenomena. The new data will roll back barriers and, no doubt, spawn even more ambitious and elusive theories.
For now, Perlmutter and Schmidt can say only what the universe appears to be doing, not why it is doing it. But taken at face value, the “what” alone is plenty strange. They have found a kind of cosmology that even the most far-out theorists had not seriously considered before. When Alexander Friedmann codified the first mathematical descriptions of a dynamic universe, he established the mathematical foundation for three basic descriptions of how it might evolve over time: the universe might collapse again someday, it might steadily expand forever, or it might teeter just on the edge between the two. Until 1998, those were the only scenarios that most cosmologists took seriously; in A Brief History of Time, updated in 1996, Hawking presents these essentially as the only possible choices. When Einstein invented the cosmological constant, however, he unwittingly established a fourth spiritual possibility. He had imagined that Lambda would exactly balance the force of gravity, keeping a finite universe motionless and intact. What Perlmutter and Schmidt see, instead, is the ultimate in unbalance—a runaway universe, in which galaxies race ever faster away from one another. The big bang gave sci/religion its own creation story. The discovery of Lambda offers a possible look at the end of days.
If cosmological acceleration continues unchecked, it holds out no hope of rejuvenation and new beginnings. Rather, it leads to an increasingly empty and isolated future, where stray clumps of matter are surrounded by furiously expanding space, racing away to nowhere. “It's going out in the bleakest fashion I can think of—it's eternity, but it's nothingness at the same time. If the universe had too much matter in it and recollapsed into a 'gnab gib' [backward big bang], that's at least exciting and has a finite end—it's like death. This other thing is just really grim,” Schmidt says. The accelerating universe could even create a spiritual crisis for Einstein's brand of sci/religion. He had originally posited a finite universe because it followed Mach's view that inertia is caused by the way an object interacts with the combined gravitational field of the rest of the universe. So what happens when the rest of the universe is no longer visible? “If you believe in Mach's principle, you can wonder if inertia will start not to make sense when the expansion takes over. It might take another Einsteinian revolution to answer that,” Perlmutter says.
From his viewpoint, Perlmutter isn't so worried about the prospect of a speeding-up cosmos. It allows an endless amount of time for things to happen, he notes. Perhaps we just need some time to adjust our philosophical attitudes to the latest scientific news. For old-time religions, however, he sees the accelerating universe deflating the stale argument that modern cosmology is just recapitulating the biblical story of creation: “The accelerating universe loses that sense that everybody likes to have that once you find out, science will turn out to be just the same as somebody's myth.” Riess captures the mix of wonder and accessibility that is the hallmark of sci/religion: “When I tell people about our different possible fates, it sounds philosophical—like talking about God. But this is something you can measure, like weather forecasting.”
9. SALVATION IN THE TEMPLE OF EINSTEIN
YOU WILL HARDLY find one among the profounder sort of scientific minds without a religious feeling of his own,“ Einstein wrote in 1934. ”This feeling is the guiding principle of his life and work. . . It is beyond question closely aki
n to that which has possessed the religious geniuses of all ages.“ A dozen years ago, I set out in search of that modern spiritualism at meetings of the American Astronomical Society. Every six months approximately 2,000 working astronomers—the country's largest gathering of cosmic explorers—take over a convoluted network of conference rooms and spend five days updating each other on the state of the universe. The look of these convocations, I soon discovered, is consistently and unnervingly businesslike: worn red carpeting, windowless rooms with yellowish overhead lighting, and participants scurrying around with plastic-encased nametags clipped to their jackets. More disappointing, the prevailing tone of the presentations is technical and detached. Many of the most renowned priests of sci/religion show up, but they offer little insight into the feeling that motivates their research. And I have never, ever heard them utter the word ”God.“
Alan Guth, whose elaboration of the big bang looms large over the Astronomical Society meetings, regards this reserved style as a sign of the times. “There's been a change in how physicists talk. Einstein felt free to talk about God; physicists today abhor the word,” he says. The shift is paradoxical: As the Temple of Einstein has grown steadily more powerful and compelling, its congregation has renounced much of the vibrant language it borrowed from old-time religion. Einstein's cosmic religion, his sense that the workings of the universe are harmonious and ultimately comprehensible to reason, is now buried within terms such as string theory or supersymmetry. Gamow's ylem has become quark-gluon plasma. Lemaitre's brightly evocative “fireworks of creation” has become the arcane “cosmic microwave background, left over from the time of recombination.” Even the big bang, whose name vaguely connotes the story of Genesis, is commonly deconstructed into more precise but puzzlingly abstract terms—a primordial quantum fluctuation, an inflationary episode, parity violation.
Obscurity of language is now practically a denning trait of modern cosmology, much as it is in particle physics, the branch of science operating at the other extreme end of the scale. Such obfuscation can make the gospel of sci/religion seem as remote as Christian heaven or Aristotelian ether. Small wonder, then, that much of the public has only a fuzzy understanding of the mystical program of sci/religion. A community of science reporters, myself included, makes a living decoding the esoteric utterances of leading cosmologists.
Prayer in the Temple of Einstein seems a daunting task, possible only after mastering a litany of unfamiliar terms and the enigmatic mother tongue of mathematics. Wander from room to room at the Astronomical Society meeting and you might never even know the faith is there. At a January 2002 session, a young astronomer named Brian Mason, of Caltech, presented the lead paper in one of the main cosmology sessions. His discussion about ways to measure the physical conditions in the early universe bore the title, “Measurements of the CMB Power Spectrum to L = 4000 with the CBI.” Compare that to the blunt directness of Einstein's “Cosmological Considerations on the General Theory of Relativity” or Gamow's 1950 lofty paper summarizing how elements formed during the big bang, “Half an Hour of Creation.” The language of science sounds as alien as church Latin or biblical Hebrew.
As the sermons of sci/religion have grown more oblique, its temples have similarly become more remote and less romantic. When I drove to the top of Mount Wilson, the site of cosmology's greatest early observational triumphs, I encountered a set of buildings that look decidedly past their prime. The visitor's center smells musty and needs a good dusting. Hubble's bentwood chair sits forlornly beneath the antique-looking Hooker telescope. It's not even his real chair, but a knockoff placed there in his memory. The cutting-edge observatories have retreated to higher locations, scraping the stratosphere on Mauna Kea in Hawaii, Cerro Paranal in northern Chile, and a handful of similarly inaccessible peaks where visits are expensive, time-consuming, and physically taxing. The Hubble Space telescope, probably the most famous sci/religious tool in the world, can be reached only by a $400 million trip on the space shuttle. Astronomers are no longer the solitary dreamers spending long, shivering nights peering through an eyepiece. Silicon light detectors and high-speed phone lines carry the images to computer labs that are halfway down the mountain or halfway across the world, where the real observing takes place. Ambitious projects such as Perlmutter's supernova search go further, relying on electronic processors to make the initial interpretation of whether there is anything interesting in each image, because the human eye could not possibly keep up with the flow of data.
These twin developments have created the gross misimpression that sci/religion is far removed from the lives and concerns of the lay public. Cosmologists do not ascend to flee the flaws of the world we inhabit, like saints striving to soar toward heaven. Rather, they ascend in order to bring the cosmic truth down to Earth and erase the boundaries between the universe up there and the world down here, boundaries that have existed only in our minds and in. our religious tales. And the unfamiliar vocabulary of sci/religion is not intended to create an insular, dogmatic faith, the way that the Bible or Koran and their elaborate body of interpretive literature define the practice of Christianity and Islam. Of course there is an element of clubbiness to the way cosmologists speak. They have their own shop talk, just as lawyers and auto mechanics do. But their jargon ultimately serves the same goal as their observatories, to unify us with our universe. The terminology of sci/religion provides a detailed way to describe wonders that are beyond normal human experience, both in space and in time. These words describe Einstein's divine vision of a coherent universe ruled by general relativity and other knowable physical laws.
While I toured Mount Wilson, I had to keep readjusting my opinion of what I was seeing, shedding the distorting attitudes of the ancient beliefs. For old-time religion, the decline of such a sacred site would be cause for mourning. For sci/religion, however, the decline of Mount Wilson is actually cause to rejoice. The Temple of Einstein has no holy ground; it operates on faith alone. Its sanctuaries or holy places of observation, like the theories they bolster or refute, are therefore in a continual state of flux. Old instruments are downgraded or discarded as new ones come along, taking the followers to a finer resolution, a better sensitivity, or a previously unexplored region of the spectrum. Mount Wilson grew quiet as larger telescopes utilizing superior technologies opened on darker, higher, more isolated peaks. But that is an old and ongoing story. The sites of all of the greatest sci/religious discoveries witness continuous change. Mauna Kea now has twelve working telescopes at its frigid summit. Five of these, including the magnificent Keck twins, began operation just within the past decade. Photon by photon, these observatories are continuing the job of the Hooker telescope, not to mention William Herschel's wooden-tubed reflector and Galileo's spyglass. They are bringing us closer to a transcendent connection with the cosmos.
Moreover, the temples of sci/religion can experience a renewal of purpose that has no analogy among the old-style faiths. The Hooker telescope is undergoing a modest rebirth with the addition of adaptive optics, a system of bendable mirrors and computer electronics that cancels out atmospheric blurring. And all across the top of the mountain, shiny new pipes link together the CHARA array—a network of modest, one-meter (three-foot) telescopes that combine their light to produce the resolving power of a single mirror as wide as the space between them. This technique, called “optical interferometry,” can produce images hundreds of times sharper than those from the Hubble Space Telescope. It only works on bright sources, so interferometry won't investigate Lambda or monitor the evolution of distant galaxies. But it can watch stars and planetary systems forming, Cepheid variable stars pulsating, perhaps even infernally hot gas taking a one-way trip into a black hole. Although such discoveries do not expand the boundaries of the universe, they do make more of its invisible wonders manifest.
At the American Astronomical Society, as well, there is more sci/religious zeal than the superficial sights and sounds indicate. Despite their reluctance to invoke over
tly theological language, in their actions the current priests of sci/religion remain firmly committed to the Temple of Einstein. “I don't think the basic attitudes have changed. Modern physicists, like Einstein, have their own intuitions about how the world works,” Guth says. Mason's paper at the society's recent meeting is a strong case in point. The “CBI” in his paper is the Cosmic Background Imager, an ingenious array of detectors designed to pick out features within the glow of microwaves left over from the big bang. Patterns embedded in the glow indicate how matter and energy were distributed when the universe was just 400,000 years old; that information, in turn, can reveal the constitution of the universe and distinguish between different models of early cosmic evolution. In other words, Mason is continuing to expand the kingdom of Einsteindom by pressing our physical understanding farther out into space, further back into time.
During an afternoon lull at the Astronomical Society meeting, Perlmutter laughed about how quickly his colleagues have absorbed the accelerating universe into their cosmological theories and transformed his once-shocking discovery into an element of the conventional wisdom. So he is pressing on ahead, gathering more data, planning additional observations, and delegating some of the computational problems in order that he might carve out some time to sleep and—if he is lucky—dig through some of his enormous backlog of e-mail. He's also working up support for building that orbiting observatory, the SuperNova/Acceleration Probe (or just SNAP), which would watch for exploding stars from space and drastically improve on the measurements possible from the ground. There's a lot of bureaucracy involved in obtaining the tens of millions of dollars needed for such a mission. “It's like re-view-of-the-month club right now,” he says. Still, he remains boyishly giddy about the need to understand the intangible. “We've got to know more about what this dark energy is—nothing is more fundamental than figuring out the energy that dominates the universe,” he says. He never mentions God, but his words thrum with the heart-pounding promise of Einstein's cosmic religion.
God In The Equation Page 25