The Canon (45 page)

Even with antimatter effectively neutered, the universe would need close to another half a million years before it was fit to be seen. Until then, all was a fog. The universe was still so hot and dense that matter could exist only as a plasma, a sea of nuclear particles and footloose electrons that scattered the light every which way, as do the water molecules of a fog or cloud. "A plasma is very nontransparent to electromagnetic radiation," explained Alan Guth. "In our early universe, photons of light were constantly colliding with the free electrons and bouncing off in different directions, so the radiation didn't get anywhere in this period." And just as it is practically impossible to peer into the heart of a thick cloud, so astronomers suspect that the plasmic conditions of the early universe rule out any hope of detecting the electromagnetic signals of the Big Bang proper.

After 300,000 years, however, the fog began to lift. The universe had expanded to a diameter about
¹
/
_1,500
its current size, and it dropped to a temperature of a mere 3000 degrees, cool enough for electrons and protons to begin expressing their innate compatibility, their electromagnetic complementarity, and to form electrically neutral atoms—simple atoms like hydrogen and helium, but full-fledged, thoroughly modern atoms nonetheless. The opacity of plasma finally gave way to the transparency of a gas. At last the universe's radiant energy could begin traveling outward in a straight line, rather than being restirred back into the pitiless plasmic paste, and it has been flying freely ever since.

Adherents of the Big Bang model of the universe proposed in the 1940s that it should be possible to detect the boundary between the opaque early universe and the transparent universe that has reigned
ever since, just as we can look through a clear sky over to the edge of a giant cloud formation. This boundary is what they call the "surface of last scattering," or "the wall of light"—the last time in the history of the universe that matter managed to smear the astral radiance into a milky blur. The wall of light should be all around us, they said, because it is the relic glow of the whole universe as it was when it was much smaller, but that universe has since puffed out about us, as it has about all the other dots on the balloon, raisins in the cake, and the like. Or picture being aboard a raisin in the middle of a thick puff of smoke, which then expands outward from us like a spherical, shimmering smoke ring. Wider and wider it billows. Time passes, and now we're standing down here in the clear, contentedly fruit-bound, peering through a large volume of transparent space, looking outward for the halo of fuzz that once upon a time was all that was.

Yes, the fuzz has to be out there, Big Bang theorists suggested. It's part of the universe; where else could it go? They also calculated that the radiation billowing off this 3000-degree surface of last scattering would have started out as extremely high energy, which means of an extremely shortwave variety. In the intervening billions of years, however, the light, as it is wont to do with lengthy travels, would have redshifted down, down, down to long, cool wavelengths, in the long, ruddy end of the microwave portion of the electromagnetic spectrum—down to wavelengths you'd expect to be emitted by a radiant body not of 3,000 degrees, but of 3 degrees. In the mid-1960s, astronomers at Bell Labs in New Jersey detected the ambient blush, the remnants of the plasmic early universe, at the predicted 3-degree wavelength, an achievement for which they were awarded the Nobel Prize. The sense-a-round radiation is known formally as the cosmic microwave background, and you can detect it yourself, in the comfort of your home, especially if you don't have a decent cable connection: the snowy interference that appears on your untuned TV is partly the result of the cosmic microwave background, the cold crackling leftover light from the universe in circa 300,000
A.B.B.
It is the first fossil, the earliest snapshot, and, if not quite music to one's ears, the closest thing we have to the music of the spheres. Together, the cosmic background radiation and the redshifting of distant galaxies sing softly but surely of a very Big Bang, and of an expansion that began 14 billion years back and just keeps Beguining along.

The cosmic microwave background is ubiquitous, and impressively uniform. The night sky might look different when you're in the outback of Australia from the way it does when you're in Halifax, Nova Scotia, with a different arrangement of constellations, but the cosmic microwave signal you'd pick up in either location would be almost identical in strength and wavelength. That sameness attests to how much more uniform in temperature the universe was in its smaller and more compact past than it is in its current state of middle-aged spread and diffusion, and logically so: Think of how much easier it is to heat a small room evenly than a large, drafty Victorian house. The uniformity of the microwave signal also underscores the uniformity with which the universe has expanded since the Bang, or at least in the eons since the plasma age ended. The smoke ring has been pushed out the same amount in all directions, and so we perceive the same sort of cool, radiant signal from all directions.

It turns out, however, that microwave radiation is not completely homogeneous. Probing the celestial lightscape with sensitive instruments borne aloft by satellite and—how appropriate—balloon, astronomers have found minute fluctuations in the background microwave radiation, spots where the signal is comparatively stronger or its wavelength longer. To cosmologists, such flickerings in the wall of light indicate that the mass of the early universe—the stuff that was bouncing the universe's radiation into a plasmic haze—was not perfectly, smoothly distributed. From the moment that matter materialized, they said, it had a little clumpiness to it, the result of so-called quantum fluctuations arising from the natural jitteriness of subatomic particles. In other words, cosmologists argue, the basal canvas had no choice but to ripple; the laws of physics, the probabilistic nature of quantum mechanics, demanded it. And those tiny ripples that we see today as trifling trembles in an otherwise standardized background glow were likely the source of all cosmic diversity and opportunity. "Those ripples were responsible for the formation of galaxies, stars, of universal structure generally," said Guth. "Without them, the universe would have been a giant cloud of hydrogen gas, and a very dull place indeed."

Our universe was certainly no idle gasbag. From the start, it had a kind of cytoskeletal integrity to it, filaments of comparative density that only gained in strength and intensity as the universe grew. Over the next few hundred million years, the first stars and galaxies began to condense out of those pockets of comparative density in the expanding plume of atoms and energy. And though galaxies today are the only known homes for stars, the only place where stars are born and die, and you won't find any hermit stars wandering through the gravitationally barren wilderness of intergalactic space, that doesn't mean the galaxies got there first. After all, who better to know how to build a warm home, a thriving community, a stellar society, than the residents themselves?
Astronomers have much to learn about the evolution of cosmic structure, but they now suspect that stars may well have preceded galaxies as the earliest celestial bodies to form out of the spidery gaseous mass of the young universe. Not just any stars, though. Not stars like our sun, much as we love it and are lucky to have it exactly as it is. Rather, the first stars were likely to have been massive, thousands of times bigger than ours. Giant stars alone have the power of which Isaac Newton dreamed before a falling apple so rudely, apocryphally awoke him—the power of alchemy. Giant stars alone can start with the simplest, lightest atoms, like hydrogen and helium, and forge them into the whole periodic palette of the elements, into all the Rubenesque beauties with their thickset nuclei—nickel, copper, zinc and krypton, silver, platinum and gold, and tungsten and tantalum and, yes, mercury and lead. We humans are not unique in our greed for all that glitters. Once seeded with traces of heavy metals, the gift of those founding stellar magi, the wider gaseous terrain of the early universe began taking on shape, and, in very short order, the skies were ablaze with millions of stars living in distinct Milky Ways.

Which brings us to another of the great discoveries of modern astronomy: Joni Mitchell was right about us all being stardust. Our lives depend now on a single, living sun, but other suns before this one have died to give us life.

The observable universe may be more than a shapeless cloud of hydrogen gas, but nevertheless this least frilly of all elements is by far the most common. Nearly three-quarters of ordinary matter consists of hydrogen, the atom with one proton and one electron to claim. Helium, the second character on Mendeleev's table and possessor of two protons and two neutrons at its core, accounts for about 24 percent of known matter. All the hydrogen and much of the helium in existence today, along with a sprinkling of the universal stock of lithium, boron, and beryllium atoms, are the direct product of the Big Bang, generated when the universe was new. The next time a family member brings home one of those unsightly Mylar balloons that remains stubbornly, desultorily afloat for so long that you decide to shred it when the balloon's owner isn't looking, consider that at least a few of the helium atoms you are about to blithely disperse into the atmosphere may have been around in their current configuration for 13.7 billion years. Now hurry up and get rid of that thing before the kid comes back.

Ambitious though the Big Bang was, its inventive capacity was limited and short-lived. The laws of physics, which either preceded the Great Explosion or were born with it, dictate that the electromagnetic
force will keep the positively charged protons of discrete hydrogen nuclei as far as possible from one another, unless something pushes them so close together that the strong force can take over. As the mightiest known force in the universe, the strong force can strong-arm the innately xenophobic hydrogen nuclei until they agree to fuse into something new—into atoms of helium. Or it can fuse together helium and hydrogen atoms into an even bigger nuclear commonwealth, a state called "being lithium." Yet each ratcheting up in the size of the atomic polity requires that much more heat and density to manage, that much more ambient extremity to overcome electromagnetic repulsion and allow the strong force to work its diplomacy. The Big Bang got as far as impelling packets of five protons into meaningful proximity—into a scattering of boron atoms—before its mass had dispersed and its initial pressure-cooker conditions had dipped below those needed to drive fusion's fancies. In the wake of the natal stabs at nation-building, the bulk of the universe's atoms remained in the same parochial hydrogen format in which they'd begun.

Yet all atom-making was not through. There were those quantumborne quivers, those clumps in the cloud, and there was gravity, gracious, warm-hearted gravity, with its sensible shoes and its feet on the ground. Gravity is the weakest of nature's four forces, but it works well on large masses, and it has the added advantage of always attracting, never driving away. After a million or so years of breathless expansion driven by the Bang's phenomenal outward-bound pressure, gravity began to exert a moderating counterforce. The pace of wholesale, whole-scale growth slowed ever so slightly, allowing the denser pockets of matter in the universe a chance to dawdle, churn, swirl, and circumnavigate. And once a sufficiently dense exemplar of these hydrogen redoubts started twisting around on itself, gravity got a really firm grip, and pulled the gaseous pocket inward, into a ball. As it condensed, the gas grew hotter, its atoms more agitated. Soon it grew so hot that the electrons were again stripped away from their nuclear partners, returning the gas to the plasmic state of the small, early universe. In the center of the gaseous orb, where the heat and pressure were at maximum exhortation, not only were the electrons torn free from their protons, but the protons of the individual hydrogen atoms were squeezed closer and closer together, until finally their mutual electromagnetic repulsion could be overcome and the business of nuclear fusion could begin anew—on a bolder and more ambitious scale than anything seen in the Bang's early pangs.

As we all know from years of hearing the energy industry pine for the
power to tame it, nuclear fusion is a wondrous thing, a Rumpelstiltskin on stilts. Not only does it transform the light and the simple into the weighty and complex, but the very act of fusing atomic nuclei together releases a big jolt of electromagnetic radiation—of energy. We humans have succeeded in fusing together hydrogen atoms and unleashing a tremendous blast of energy in the process: that is the source of a hydrogen bomb's apocalyptic power. Far trickier is figuring out how to fuse atoms in a controlled, orderly, and, of course, cost-effective manner. It's a daunting task, but one that our sun and the billion trillion or so other stars in the universe accomplish every day. The source of a star's energy, its shine, its heat, its guiding wishworthy light, is thermonuclear fusion, the perpetual merging at the dense stellar core of large numbers of small atoms into a smaller number of larger atoms. The power of nuclear fusion is the defining hallmark of a star, and it takes a certain heft and density to pull it off. Jupiter is a very big ball of gas, but it's not quite big enough. The atoms at its core are not under sufficient pressure to change their elemental identity. Only at a mass about eighty times greater than Jupiter's will a ball of gas have the stoutness of heart to accomplish thermonuclear fusion, the squeezing together of reluctant singleton nuclei into the radiance of atomic matrimony.

The first stars to condense out of the primal nebula, though, were likely much bigger than eighty Jupiters, or even eight hundred suns, for as they began their collapse, the compaction through gravity of a thick slub of gas into a tidier and more coherent sphere, the increasingly dense object would attract ever more matter from its dusty surroundings and so grow huge rapidly by accretion. The early universe was a cramped, cluttered, dusty, gaseous place compared to today, and so a condensing ball had no choice but to pull in huge hanks of extra matter as it tightened in on itself—to augment its mass even as its volume diminished. That hugeness exacted a high personal cost: giant stars die young and violently. Yet if their lives were brief, their art would long survive them, and it is well worth a look at the docudrama of stellar genius.