Designing Universes

by James Gleick
ORIGINS: The Lives and Worlds of Modern Cosmologists
by Alan Lightman and Roberta Brawer. Harvard University Press, $29.95.
YOU KNOW YOU left your glasses downstairs on the coffee table. The kitchen is just off the corridor to the right. There’s a grocery store around the corner and down the block. If you kept walking you would reach the river in about ten minutes. The city spills across it, gradually thinning to wooded suburbs. It sits in the foothills of a mountain chain of whose presence you are distantly aware, though the peaks can be seen only on the rarest of clear days. The mountains run down the spine of a continent between two great oceans, on that famously oblate spheroid called Earth. Nor does your sense of place end there. Far away, but not unimaginably so, is the sun, one of 100 billion stars of the Milky Way, itself one of billions of galaxies distributed through space. That space is not the flat, neutral stuff of your grandparents’ pre-Einsteinian intuition but an eerily plastic medium that somehow embodies both time and gravity. It also happens to be expanding at high speed, dragging its contents farther and farther apart, thanks to the explosive event that presumably set the whole universe going a mere 10 or 15 billion years ago: the big bang.
That’s already a lot to know about where we are, as this remarkable century nears its end. One human lifetime ago our intellectual horizon barely reached to the stars around ours. No one knew that beyond our galaxy lay wide gulfs filled with more galaxies. No one knew how the sun managed to shine or how old anything was. About the universe as a whole, no one knew much of anything. At the very least it seemed safe to assume that the universe was the same everywhere, that it always had been and always would be: world without end, amen. Infinite, static, Euclidean, ageless, and homogeneous—that was the universe as the century began. A comet was a big deal when there were no quasars, no cosmic strings, no singularities, no brown dwarfs or white dwarfs, no black holes or worm holes. Yet even with all these miraculous objects cluttering up the cosmos, somehow we find room for it in our mind’s eye. We manage to squeeze it in somewhere after continent, world, and solar system. Our universe must have seemed bigger somehow when it was . . . everything.
The people who have reduced the universe to such manageable proportions are a group known as cosmologists. They are scientists; they start out by playing with chemistry sets, go on to study astronomy or physics, spend years making images with telescopes (the romantic days of looking through telescopes being long past), put forward theories mainly in the language of equations, and debate the evidencepro and con in scientific journals. Yet cosmology stands out among the sciences as an enterprise that is not fully scientific after all but an amalgam composed also of philosophy, art, faith, and not a little hope. Black holes may be objects of pure physics, but those who ponder the first hot nanoseconds of the universe’s existence are pondering a place where science alone cannot go.
It’s hard for any seeker after knowledge to concentrate on the immediate aftermath of the big bang without letting the mind wander to the problem of what was happening, say, a minute earlier. Was a previous universe winding down? Was all creation merely, as the scientists so delicately put it, a fluctuation of the vacuum? Are there other universes having big bangs elsewhere, and if so, elsewhere in what? This way madness lies, or at least metaphysics. The big bang itself, despite the volumes of scientific analysis from which the concept sprang, seems to leave cosmologists begging the very biggest questions. Gerard de Vaucouleurs, a French cosmologist interviewed in Origins: The Lives and Worlds of Modern Cosmologists, tells the story of his audience with the pope after a 1979 cosmology conference in Rome: “He gave us a fine speech in Italian, about astronomy and space and about the big bang. He made it very clear that he was all for the big bang, because, essentially, ‘We told you so.'" What preceded the big bang? De Vaucouleurs says wryly,
I know what the answer of physicists is: “This is not a question you should ask because this is a mystery. There was no time and there was no space.” The theologians used to make it even simpler. “You should not ask those questions, brother, because otherwise the Inquisition will start being interested in you.”
ALAN LIGHTMAN, a physicist and the author of two elegant science-essay collections, and Roberta Brawer, a graduate student at the Massachusetts Institute of Technology, have assembled in Origins a sequence of twenty-seven interviews with the best of the cosmologists, leading members of an unusual fellowship —the people who have most effectively replaced theologians. The interviews build on a project at the Center for the History of Physics of the American Institute of Physics; the center has drawn oral history from many of the century’s leading scientists. It’s in the nature of the oral-history business that such interviews ramble and falter; while they are a rich resource for scientific historians, they don’t necessarily make for pleasant or even coherent reading. (Another limitation of the form is that oral historians invariably take a deferential approach to their subjects; pointed or argumentative questions are not part of the game.) On the whole, such interviews make better archives than books. Yet Lightman and Brawer have made something special out of the words of these twentyseven men and women. If you are willing to tag along for the odd turns into blind alleys and to back up again looking for the main path, a wonderful twopronged story starts to emerge. Half of it is the story of our horizons’ being pushed out to the very edges of the universe. Asking big questions and beginning to hear answers—“the grandness of the cosmological dream . . . that ephemeral realm,” as Allan Sandage, an American cosmologist, puts it. The other half is far more sober: the story of the scientific community, despite all the knowledge it has gained, caught at a moment when its theories are in a terrible, uncertain flux.
The cosmologists’ sense of the universe rests on a surprisingly small number of major astronomical observations, each in its own way a monument of modern science. One was Edwin Hubble’s discovery, in 1929, that other galaxies are streaming away from ours, and that the farther away they are, the faster they are moving—the discovery, in other words, that the entire universe is expanding. Another was the discovery, in 1965, of a sort of echo of the big bang, a faint, smooth, background radiation coming from every direction in the sky. A third was the discovery, made just in the past few years, that galaxies, far from being randomly scattered about, are organized in patterns that resemble bubbles, on the largest scale anyone can see, from one end of the visible universe to the other.
I say observations, but even these very concrete-seeming discoveries are not really seen. What an astronomer sees is groups of numbers representing various wavelengths of light arriving from various directions. Even the most innocent measurement of distance or velocity or age relies on a long chain of inferences: a combination of wavelengths suggests a chemical composition; a chemical composition suggests a galaxy’s age or type. Smart guesses can then be made about the luminosity of certain galaxies, and then about their distance from us. Cosmologists don’t actually know the distance of any faraway object to an accuracy better than a factor of two or so. Though theory rests on observations, cosmological observations always have some theory built into them in the first place.
Still, those are the verities: the cosmic expansion, the cosmic background radiation, the cosmic large-scale structure. Then come the paradoxes—the flies in the cosmic ointment.
Lightman frames the issues for the reader in a clear and thoughtful fiftypage introduction, and takes pains in the interviews to steer the cosmologists toward the places where modern theory flounders most helplessly in the face of observation. One is that the total mass of the universe seems astoundingly close to the precise amount needed to make the universe “flat,” its ultimate fate to be precisely balanced between eternal expansion and eventual collapse. Many (but not all) see that as a coincidence that badly needs explaining. Perversely, another difficulty is that most of that mass is invisible. The known stars and clouds of gas don’t account for it. Cosmologists have been forced into the position of postulating a universe mostly made up of some stuff that is not ordinary matter. What is it? Nobody knows.
There are other problems too. The huge patterns seen in the large-scale structure of galaxies defy easy explanation, as does the evident lack of any pattern at all in the cosmic background radiation. Cosmologists are scientists— the numbers are supposed to check out, the theories are supposed to match the observations, and lately, by and large, they don’t. While the cosmologists wait to see whether the Hubble Space Telescope will ever be able to provide enlightenment, they are reduced to giving odds and making bets on rival theories, as James Peebles, of Princeton, and Joseph Silk, of Berkeley, say in a new paper in Nature: “Many bottles of the finest champagnes and malt whiskies, and even more esoteric stakes, rest in abeyance while observers struggle to count rare photons from remote galaxies. . . .”
IT’S THE VERY messiness of life in the trenches of cosmology that makes Origins so useful. Forced to face the limits of science, many of Lightman’s interview subjects speak revealingly about the prejudices, the beliefs, and the aesthetic preferences that help shape their views of the universe. Jeremiah Ostriker, of Princeton, points out, for example, that astronomers have grown up learning that the history of their science is a continual subversion of the human-centered perspective: the sun does not revolve around the earth, the Milky Way does not revolve around the sun, the universe does not revolve around the Milky Way. Oddly, therefore, the bigbang theory leaves a subtly uncomfortable feeling, because it places humanity at a special point in time. “Anv scientist is brought up to think that anything unique about his place in space and time is probably an artifact of either his imagination or the measurements,” Ostriker savs.
We’re bred to have a bias against anything that shows things to be man-centered. In a big bang universe, we’re at a privileged point because we know we couldn’t have existed in the very distant past or the very distant future. And that seems strange.
No one can quite ignore the fact of our existence. One thing we know about the universe is that it has made possible the existence of creatures capable of asking questions about it. To some cosmologists, life seems infinitely precarious. An arbitrary change in some number here or there would mean that life could never have arisen, or so it seems. Some argue that the proton must be 1,836 times heavier than the electron, simply because otherwise there would be no chemistry, no life, and no cosmologists. Others frame the issue more profoundly, like Martin Rees, of Cambridge University, who sees complexity as the central issue. “We have—and our very existence requires—a universe that allows complexity and structure on many scales to evolve within it, starting off from simple beginnings,” he says. Regardless, once a cosmologist starts asking what sort of universe makes life possible, it’s a short step to thinking about multiple universes, ensembles of universes, mini-universes, parallel nonintersecting universes . . . and one understands why the pope might smile.
In the interests of understanding cosmologists as human beings. Lightman also tries to draw them out about their childhoods and scientific origins, and this comes out poorly, with its repetitious string of science-museum visits and other predictable experiences. Every scientist has told this kind of story too many times. Much more fertile is the philosophical question that Lightman asks near the end of every interview: What kind of universe would you design, if you could have any kind at all? Most of the cosmologists suddenly sparkle. Some like the universe as it is; others wish it could be different. Some passionately desire a steadystate universe, with no big bang, just the quaint infinitude in space and time that seemed to exist a century ago. Some wish they could eliminate disease and injustice. Some want a universe that allows time travel. Some believe that all possible universes already exist, somewhere and somehow.
My favorite answer came, almost inadvertently, from Maarten Schmidt, a Dutch cosmologist. “God! What a wild question,” he said first. “This is really the worst question I’ve ever heard . . . . It’s like asking me to take off my clothes and start walking around here.” And a minute later he added,
I find it extraordinary that it is possible with human means, with pieces of glass that are no larger than this room, to see things that are interestingly far out in the universe. Sometimes it strikes me that the universe is much smaller than . . . All right, here we go. I would have constructed a bigger universe. I think the universe is small.
It’s no wonder the cosmologists are willing to take on Lightman’s challenge. Designing universes is mostly what they’re doing anyway.