That particle, the paladin of this tale, chances to be a proton. And as such, as luck would have it, it ranks among the heartier pieces of matter in the infant cosmos. Barely a trillion of its kind would it take, arrayed side by side, to span the dot over this "i"; a mere thousand times that number would suffice to tip the scales against a modest-sized virus.

So comparatively huge is our proton that it seems almost planetlike amid the early universe, a smooth, white, Venus-in-miniature careering through space, with other such particle worlds dimly visible in the distance. Of these some are protons, indistinguishable from our own; the rest, neutrons – similar in size, hued in battleship gray.

Still far off is the age when protons and neutrons will be able to forge a lasting alliance, to come together in tight, permanent clusters. Yet when that does happen these two particle types will emerge as crucial building blocks. They will emerge as building blocks for the nuclei of stable atoms, and so, as the substrata for more mature forms of matter, even for consciousness itself.

Nothing else seems to occupy the newborn universe. Nothing, that is, save for a dazzling, all-pervasive glow. And yet that glow conceals an inner quality. There is a fine texture to it, a shifting, sparkling texture. Indeed, far from being continuous and bland, this iridescent seas swarms with a myriad of lowlier particles, a billion of them for every proton and neutron.

Suddenly, without warning, one of these lesser specks of matter streaks directly across the path of our advancing proton, scarcely avoiding an impact. Like a coal-black meteor it seemed in comparison with the proton's bulk. But there could be no doubting its true identity. This was an electron, a member of the third species of particle that, together with protons and neutrons, are needed for the fabrication of atoms. Its negative electric charge exactly balances the positive charge of the proton. In mass, however, the electron is a dwarf, over 1,800 times lighter than either the proton or neutron. And in size – even a meteor is too lofty a description. For the extraordinary fact is, the electron seems to have no size at all, to be simply a dimensionless point.

In all directions the electrons abound, over 100 million of them to our single proton. And yet they are not the only species of swarming horde. There is also the positron. And here is a very strange thing. For the positron seems to be the complete antithesis of the electron, a sort of mirror image – white meteor to the electron's black.

Nor is the electron unique in having a counter-self. To every fundamental particle in nature there is a corresponding "antiparticle." An antiproton, an antineutron. And so on. Always, particles and their antiparticles are equal in mass. But other of their properties, such as electric charge, are reversed. So, for instance, the positron bears a charge that is as much positive as the electron's is negative.

Most surprising of all is what happens when particle and antiparticle meet. For then they completely annihilate one another, freeing the energy previously pent up inside them as a pair of entirely new particles – particles known as photons.

Everywhere now the crackling of electrons annihilating with positrons becomes apparent, like the noise of some overworked Geiger counter. And yet that mutual act of destruction also prompts a question. For why do so many electrons and positrons remain? It seems that, despite their efforts to extinguish one another, their numbers remain more or less the same.

Reenter those mysterious photons, products of the electron-positron clash. These make up a third superpopulous particle tribe, as numerous even as the electrons and positrons. But, at the same time, they are a very different breed. For photons, it turns out, rather unexpectedly, are particles of light.

Rainbows. A star in Orion. The Mona Lisa's smile. Light may be all of these – or at least the bearer of information about them. And yet – a stream of tiny particles? So, at the subatomic level, may it behave.

A light particle, a photon, is not a material thin. Its substance is not of matter but of pure energy. And the fact that it vaunts energy alone enables it to do what no material particle in nature can – to travel at the ultimate cosmic speed (186,282 miles per second in empty space), but it can travel neither slower nor faster than that. To impede a photon, to trap and examine it, is to destroy it and so free its energy for some new purpose.

Most unusual is what may happen when two photons collide. If, together, the photons have enough energy, they may give rise to a fresh pair of particles, one particle plus its antiparticle. What is more, the offspring of this "pair-creation" process may be particles with mass. Mass from energy. Strange. Strange, at least, it seems to dwellers of a macroscopic world. That matter and energy should be two sides of the same coin. That matter is mere patterned energy; energy, the formless clay out of which material things arise.

Now the reason the annihilating electrons and positrons remain so numerous becomes clear. Directly above our proton, two photons – glittering Fourth of July rockets – converge, collide. And abruptly vanish. In their stead materializes an electron-positron pair! And it is the same throughout the rest of this young cosmos. The rejuvenation of the warring electron and positron hosts is everywhere taking place. As fast as the antagonists are slaying one another, new recruits are being introduced to the fray through the efforts of the photons. Which is to say, the electrons and positrons and photons are in dynamic equilibrium so that the number of each, one second after genesis, is maintained approximately the same.

But what of the protons and neutrons? Why are they not being created, along with their antiparticles, from photon collision?

Like all newborns, the cosmos is small. Not nearly so small now, perhaps, as it was but a heartbeat ago. Yet very tiny still compared with what it will become.

Imagine all the substance of 100 billion galaxies drawn into a bubble of space only 200,000 miles across – less than the distance from the Earth to the Moon. Such is the condition of the one-second-old universe.

Take a bicycle pump. Pump it several times, and the air inside becomes warm. Compression causes heat.

Take the universe. Squeeze its entire contents into a ball 200,000 miles across. And the cosmic matter becomes hot. Searingly hot. One second after genesis the universe swelters at ten billion degrees centigrade. By comparison, ground zero of a nuclear blast would seem the very essence of tranquility.

Presently that close encounter with the electron-meteor, already described, takes place again, but now in reverse. The electron flashes by, this time in the wake of our retreating proton.

Another electron spears past, perilously near. Followed by another, and another. And then the inevitable: Squarely on, our proton is struck by one of these speeding mavericks. For an instant it seems as if the luckless electron may simply be engulfed, as a fist-sized meteor would be by the Earth, without effect. But then, rapidly, from where the smaller particle buried itself into the larger one's surface, a gray shadow begins to spread outward. Soon that grayness has enveloped the whole of our proton. And our proton is no more. It has been transformed – into a neutron! (In forward time, of course, this would be seen as a neutron decaying into a proton plus an electron.)

Here, then, is another kind of particle reaction common with the early universe. Already, photons in collision have been seen to give rise to electron-positron pairs; electrons and positrons in annihilation to yield photons. Now, it transpires, an electron may merge with a proton to spawn a neutron.

But not simply a neutron. When the electron struck, a second particle, a wraithlike thing, sprang from the midst of the reaction, only to hasten away at vast speed. It was a neutrino, one of nature's exiles, bizarre and aloof.

Billions of neutrinos from the depths of space have passed unmolested through the reader's brain in the time it has taken to assimilate this wild thought. Some came directly from the one-second-old universe itself. Most, by now, have also navigated clear through the body of the Earth as if it were a vacuous ball. Neutrinos move at, or very close to, the speed of light. They are either massless or the possessors of a mass so small that it has not hitherto been measured. And hardly ever do they court the attentions of ordinary matter. A light-year of lead would pose little threat of absorption to one.

But in the subsecond cosmos the state of matter is far from ordinary. The particle soup here is very, very thick indeed. So thick, in fact, that even a spectral neutrino may not move through it far without the risk of interaction.

Just as an electron and a proton may combine to produce a neutron and a neutrino, so, under the extreme conditions of the early universe, the reverse reaction can as easily take place. Within the first second of creation, neutrons and neutrinos find it a simple matter to unite and produce protons and electrons. In complementary style a neutron and a positron may collide to yield a proton and an antineutrino. And to complete the round: From colliding protons and antineutrinos may come neutrons and positrons.

All of which suggests, at first, unbridled confusion. In this primal subatomic riot, incited by ultrahigh densities and temperatures, the various particle species seem capable of interacting at will, randomly, in any fashion. Protons, neutrons, electrons, positrons, photons, neutrinos, and antineutrinos– the main particle types in the cosmos at this stage – all are implicated. And the result: apparent chaos, apparent anarchy.

And yet, in truth, there is an underlying order, well concealed perhaps, to what goes on here. The particles cannot combine ad libitum. Nor are the results of their collision altogether arbitrary.

The universe is like a game of chess. It has rules. And those rules govern the actions and behavior of everything there is, including subatomic particles, just as the rules of chess dictate how chessmen may move.

For example, there are conservation rules. Certain quantities, nature demands, must pass through a particle reaction unaltered. Among these – energy. The summed energy (including energy in the guise of mass) of the particles entering a reaction must exactly balance that of the particle products. Energy, overall, can neither be created, nor destroyed. Only can it be reforged, recast.

And, in like manner, nature insists always that electric charge be conserved. What charge goes in must also come out. As when our proton mutated into a neutron. Proton and electron (total charge: +1 + (-1) = 0) gave rise to neutron and neutrino (total charge: 0 + 0 = 0). Had our proton, on the other hand, met with a positron, it could not have produced, say, a neutron and an electron. For then, in flagrant violation of charge conservation, the total charge would have had to change from +2 to -1.

Thus nature sets strict limits on the possible variety of ways that basic particles can mix and match. And yet not only through the conservation of energy and charge does it do this. There are other quantities, too, that it decrees be left unaltered, quantities wholly unfamiliar at the macroscopic level, and so apparently arbitrary that they suggest a much deeper significance to nature's rules. They suggest that not only do these rules control how matter and energy behave but that they also determine exactly the basic forms that matter and energy can take.

Which returns us to our chess analogy. For is this really not also the case with chess? That the rules of the game govern not simply the movements of some preexisting chess pieces but that those rules, in some sense, actually create the pieces. Forget, for a moment, the superficial appearance of a bishop or a rook or a pawn. The way it is carved, whether of ivory or wood, even its physical presence on a physical board – these are not what fundamentally matter (chess, after all, can be played in the head). It is the definition of what a piece can do, how it may move, how it may interact with other pieces, that is its true and central essence. And that definition follows directly from the game's precepts.

So it is with the universe. The laws of nature lay down precisely, uniquely, the fundamental modes in which matter and energy occur. They define, in other words, the scope and properties of subatomic particles. Moreover, they bring into being the intangible essence, the potentiality, of those particles. And yet here is a critical point: Why those specifically?

Just as in chess there is a small repertoire of pieces – a rook, a queen, a knight, and so on – so in nature there is only a limited number of different particles. There is an electron, a proton, a neutrino. But, for example, there is no particle with ten times the mass of the electron and twice its charge. Nowhere does nature's design provide for such a creature, just as surely as chess makes no allowance for a piece that may leap over three others in a single move.

The cosmic rule book defines just certain types of particle. But not only that. It defines them in such a way that they seem to fall quite neatly into family groups. One such family, the baryons, or "heavyweight" particles, includes the proton, the neutron, and their antiparticles. A second clan, the leptons, or "lightweight" particles, includes the electrons, the neutrinos, and their antiparticles.

Now those additional conservation rules, alluded to earlier, make their appearance. For the universe, it turns out, is meticulous about keeping the separate populations of leptons and baryons at a constant level. Always, in any particle reaction, the total number of baryons less antibaryons and the total number of leptons less antileptons remains the same. And that is extraordinary, for these quantities – the so-called baryon number and lepton number – play absolutely no other part in the physics of the cosmos. Whereas charge and energy, for instance, as well as being conserved quantities, exert obvious dynamic effects, the baryon and lepton numbers seem merely to be a cosmic accounting device.

Why should the universe be this way, why so incredibly contrived? Why should it follow one particular set of rules – one seemingly so arbitrary rather than any other? Who or what made this special selection?

We are like the priests of that fictitious tribe, puzzling over the origin of their mountain stream. Yet we are also bolder than they. For now we are heading up the mountain, swimming back against time's current, moving ever closer (so we guess) to the ultimate source of the cosmic stream on the topmost peak.

Our proton has reached to within just one tenth of a second of Time Zero. And now space seems more confined, more congested than ever. The temperature has soared to a tropical 30 billion degrees; the density has risen to over 10 billion trillion trillion times that of lead.

And yet, spectacular though these changes may be, they are quantitative only. True, the particle soup has grown hotter, thicker, even than before. But in content or structure it has not much altered. And that is perhaps surprising, even disappointing. For now the time for such significant change appears fast to be running out. Only one tenth of a second remains before the supposed wellspring of creation itself comes into view. And what is that mere finger-snap of time compared with the billions of years available for cosmic evolution to come? Is genesis about to be exposed as a nonevent, as the greatest anticlimax of them all?

Not quite. Time, that master magician, is up to its tricks again. For now it would have us believe that it is a simple thing, a linear thing, always to be considered in equal intervals, each of the same importance (an illusion our clocks serve to strengthen). And yet, of course, that is nonsense. What matters, what is crucial, is not the size of a time interval but what happens within it. During the first one tenth of a second more took place, very much more, than in any similar-length period that followed. The universe underwent more transformation, experienced a greater richness of events, in that first split second that in all the billions of years of star-making and galaxy-building to come.

But how to grasp such a concept? How to become aware of the immense potential for change within even the most slender time slices close to genesis?

First, we must abandon the usual linear way of depicting time. In its place set up an exponential scale in which successive, equally-spaced divisions signify not some fixed increment of time but rather a tenfold leap in its value from the previous division. Bring in, too, a new style of notation. So that, for example, the time of one second after the start of the universe is shown as 10⁰ s, on the exponential scale. Immediately before this comes the division marked 10^-1 s, or one tenth of a second; immediately after, the division labeled 10¹ s, or ten seconds. So organized, the axis of time accords the same priority to the period between one tenth of a second and one second as it does to that between one second and ten seconds.

Continuing the exponential scale into the past, further milestones are placed at 10^-2 s (one hundredth of a second), 10^-3 s (one thousandth of a second), and 10^-4 (one ten-thousandth of a second). And now the wealth of opportunity for cosmic development within the first few moments of creation starts to become clear. For on this new scale the "gap" between one ten-thousandth of a second and one thousandth of a second is as broad as that, say, between 10³ (a thousand) seconds and 10⁴ (ten thousand) seconds. The possibility, at least, emerges that what previously may have been dismissed as trifling instants of time near to genesis could, in fact, rival in importance much longer intervals (as measured linearly) that occurred later on. Taken to an extreme, the potential for significant change within the universe may have been as great, for instance, between 10^-36 and 10^-35 of a second (a gap of only nine trillion trillion trillionths of a second) as it was between 10¹⁸ and 10¹⁹ seconds – a span of over three billion years!

Of course just placing the whole cosmic timescape within a fresh frame in no way alters time's basic nature. That is not the point of the new scale. The point is to highlight an aspect of time that already exists but is easy to overlook. Namely, that time can accommodate a vast number, an unlimited number, of events of critical significance even within its smallest recesses. That, in fact, the universe can evolve out of all recognition within one of time's most fleeting moments – especially when that moment happens to be among the very first.

Think of a human analogy. Think of someone who, as an adult, may take months or years to master an important new skill. Who would guess that within a similar time space, as a young child, that individual had discovered how to breathe, eat, accurately recognize faces and objects, crawl, walk, draw, even talk – skills of astonishing complexity and subtlety.

The universe, too, as a child, learned at a remarkable rate. It learned faster when young because, like a human child, it was much smaller, and all of its internal processes ran correspondingly swifter. The closer the time to the moment of its birth, the more frenetic was its activity and its rate of development. Brief though one tenth of a second may seem in later context, to the juvenescent cosmos it must have appeared as endless, as eventful, as any hot summer in childhood.

So now, imagine: Ahead, in the midst of the early subatomic melee, our particle. Below, extending in a thin luminous band across the base of our field of view, a scale like that of a clear tape measure. Time values, marked exponentially on the scale, drift slowly, steadily, past a fixed pointer that reveals the current time reading. Its value now: 10^-2 s AG, one hundredth of a second After Genesis.

And increasingly our particle hero seems to be suffering from an identity crisis. Under heavier and heavier bombardment by electrons, positrons, neutrinos, and antineutrinos, it flits ever more rapidly back and forth between neutron and proton states, from gray to white and back again. So much so that the generic label "nucleon," embracing both proton and neutron, from this point on will serve it more aptly.

All around, the dawn particle sea roisters. Amid seething waters of 100 billion degrees our nucleon now moves, buffeted and tossed by the currents of a fluid inconceivably more dense than any ocean on Earth.

Yet still the blend of particles is more or less the same as before. Liberal amounts of the finer ingredients, electrons, positrons, photons, neutrinos, and antineutrinos, remain delicately, but essentially, spiced with the much coarser nucleons.

Onward our particle flies. Beyond 10^-2 s AG, beyond 10^-3 s, ever on, in a madcap dash to keep its appointment with genesis.

Now the cosmic chronometer reads just 10^-4 s AG, one ten-thousandth of a second after the start of it all. And at last, it seems, the promise of change hangs heavy in the air. Out of a nearby collision of two photons, a proton-antiproton pair appears. A moment later, in the middle distance, a neutron and antineutron emerge in similar style. More and more the process is repeated, as the universe surges past the critical temperature, about ten trillion degrees, at which nucleons and antinucleons form.

But remember: Throughout all this the cosmic clock is running backward. So that, in fact, what is happening now is the final destruction of the antiprotons and antineutrons seen in time-reverse order.

Further our particle moves into the past. Further the universal temperature climbs, well beyond that of the nucleon threshold, so that greater and greater are the numbers of protons, neutrons, and their antiparticles being spawned in the space around.

By 10^-6 s AG the nucleon-antinucleon population has risen outrageously, 100 millionfold. Risen to be as high as that of the leptons and photons, for by this time all of these particles are being created and destroyed continuously, and with equal ease, during subatomic collisions.

Now that riddle of the antinucleons' disappearance, hinted at earlier, stands firmly astride our path, demanding our attention. For these are the stark simple facts:

At 10^-6 s AG the numbers of nucleons, antinucleons, and photons are, to all appearances, equal. Yet by 10^-4 s AG only one nucleon survives for every 100 million photons, and there are no antinucleons left at all. Since the sole way nucleons and antinucleons can be destroyed is by annihilating with each other on a one-to-one basis, we are left with a remarkable, almost unbelievable, conclusion. Namely, the original populations of nucleons and antinucleons were not exactly the same. There is an excess, in the one-microsecond-old universe, of roughly one nucleon for every 100 million nucleon-antinucleon pairs. And tiny though that excess may seem, it is both intriguing and momentous. Intriguing because it proves beyond all doubt that the rules of nature have a peculiar built-in bias for matter over antimatter. And momentous, as already suggested, because that relatively small band of nucleonic survivors will become the basis for all the important structures in the universe to come.

Why should the cosmos not be completely evenhanded in its treatment of matter and antimatter? The origin of asymmetry, any sort of asymmetry, seems as incredible as that of the universe itself. Who told nature it had to be lopsided?

But even as the question is asked, our attention is diverted. For now, just as the time gauge slips past 10^-6 s AG, another tremendous change takes place. Our particle world, our seemingly secure rock in this unsafe cosmos, abruptly breaks up! In a flash its large gray-white spheroid form is gone, shattered. But shattered not into various odd, sizable chunks, like a real planet that had disintegrated, but into three of the tiniest specks imaginable. No bigger than the pointilistic electrons are these. And their name – quarks.

Faster than we can follow, two of the quarks born of our nucleon's demise escape, losing themselves in the particle maze around. Only one remains on center stage to become our new hero, or rather our old hero in its new and lessened form.

And the other nucleons in space? They, too, it seems, are bursting spectacularly apart, showering space with their component quarks and antiquarks. Neutrons and protons were not, after all, truly fundamental particles. Each was a bound state of three much smaller flecks of matter, a bag of quark triplets.

But how did the quarks come to be in such bags? The answer to that has to do with the nature of quarks and, in particular, with the nature of the force that operates between them, which is very odd indeed. Quarks attract one another with a force that actually becomes stronger the farther the quarks are apart, as if each were joined to its neighbors by means of an unbreakable elastic thread. Closely packed, quarks behave as if they were free – almost as if they were content that others of their kind were nearby. Yet if any attempt is made to separate them, the quarks immediately counter this by pulling each other more and more powerfully together. So intense is their social urge that quarks simply cannot be made to exist in isolation.

Now, apparently, at about 10^-6 s AG, a watershed has been reached. No longer can the quarks remain as a single, closely knit, cosmos-wide community. The density of matter has already become too low for that. Driven by their irrepressible need to remain always very near to at least some of their kind, the quarks separate into groups of three. Always three – three quarks or three antiquarks – an arrangement that seems to satisfy well their communal desire. Now, after the first one millionth of a second or so, and for all the rest of time, the universe will be devoid of "naked" quarks. Try to pluck one of its nucleonic bag and the attempt will be foiled. For each quark is like the end of the elastic thread of force that joins it to its neighbor. Can one end of a thread be made to exist on its own? No: Because in the attempt to isolate one end, the original thread is snapped in two, each new piece with its own pair of ends!

But now already our own quark has moved deeper into the past, back to a time when many of its kind still roamed free. Ever smaller dwindles the number of nascent nucleons and antinucleons as their contents break free to join the primal ocean of quarks all around.

A mere 10^-8 s AG reads the time gauge. And now all protons and neutrons and their antiparticles are gone, leaving the universe replete with an inconceivably hot and dense consommé of leptons, photons, and quarks. Not one of these particles boasts any extension in space. Not one has the solidity or the apparent propensity for organization that matter in the future universe will have. And yet each of these spots of next-to-nothingness seems to "know" exactly what it is; even stranger, what its rules of engagement are with other particles. And that seems most peculiar. It seems to bring us close, in fact, to the very heart of what reality is. For now we are dealing not with stars, or rhinos, or political intrigue, or with any such higher level of complexity. One hundred millionth of a second after the universe began, we stand in the presence of near-ultimate simplicity.

Ironic that something so simple should prove so enigmatic, so hard to understand. We thought we knew matter, knew it intuitively at least. Just as we believed we had an innate feel for those other rudimentaries of nature, energy, space, and time.

Matter was? Tangibility, substance. It was the ground beneath your feet, this book in your hands. And yet all that is now seen to involve a much more abstruse concept. What we experience and label as "matter" in our macroscopic world is actually some vastly elaborate and entangled hierarchy, as far removed from the basic underlying essence of matter as a Wagnerian opera is from each of its component notes.

Matter – raw, unembellished matter, the protocosmos reveals – consists of quarks and leptons. And nothing more. All there ever will be in the universe must be fashioned from these insubstantial parts. (The photons, too, are still present in huge numbers but are constituents of energy.)

But a quark and a lepton have no size. And yet, somehow, they must contrive to make "objects" that we perceive to have physical extension. Objects like you and me, and galaxies.

And there is more to this mystery of matter. Because, of course, the quarks and leptons of the early universe are not individually aware of the task ahead of them – that they have to come together to make neutrons and protons, atoms and molecules, stars and galaxies, and, eventually, cosmologists. Yet at 10^-8 s AG they are also everything, materially, that there is. And from them, indeed, progressively more interesting creations will come.

Blind and primitive the dawn quarks and leptons may be. Yet they are destined for greater things. Though their febrile dance has the appearance of being chaotic, out of that chaos, we know, will emerge order. It is as if they carry within them a code, like a colossal genetic code, for building the universe to come.

But building presupposes the ability to join parts together. So that not only must there be fundamental particles, but there must also be fundamental forces by which to bind them.

Now our time indicator shows 10^-9 s AG. And the entire cosmos has shrunk so much that it would fit comfortably inside the globe of the future sun – a tiny womb wherein the most primitive forms of matter and energy incubate.

Deeper, ever deeper, our particle descends into the eye of the swirling vortex of counterclock time. To within one ten billionth of a second of creation it moves, while around it the temperature soars to ten thousand trillion degrees. And now another transition begins, more remarkable, more profound even than the freeing of the quarks from their nucleonic jails. Once again it is as if the universe had tripped some hidden mechanism, a mechanism seemingly precontrived and awaiting only the right time and conditions to set it off.

Four cosmic forces there had been: electromagnetism, gravity, the strong force, and the weak. Four basic ways in which the humblest particles in nature could interact. But now, at 10^-10 s AG, an extraordinary change is starting to take place. Electromagnetism and the weak force, previously so disparate in character, are fast growing more and more alike. As the temperature rises further and time edges back to just one trillionth of a second AG, so these two forces gradually meld and become one. The product of their improbable union: the electroweak force.

(Again, it must be remembered, this is in time-reverse order, from future to past. So that in truth the universe started out, prior to 10^-12 s AG, with three distinct forces. One of these, the electroweak, then began to fork. And thereafter its twin offshoots went their separate ways, never to reunite.)

Even so, the primal kinship of electromagnetism and the weak force would not be lost, just as in some future age man and the apes would diverge from common stock and yet still retain the evidence of their shared ancestry. That affinity, between life's evolution and the development of the early universe, runs deep. Both are marked unmistakably by the growth of complexity. Four forces from three. Compound particles from simple. Man and ape from a single, prehominoid ancestor. Revealed here is a common omnipresent urge of the cosmos to unfold, to progress, by its own efforts, toward some unseen final goal. This same urge it was that prompted both the splitting of the electroweak force and, billions of years later, the division of the line that led to man.

Yet how far back can this process of complication be traced? Are the three forces and the handful of elementary particle types in the universe at 10^-12 s AG themselves the products of an even earlier chain of evolution? Or do they represent nature's ultimate, irreducible state?

Onward our quark explorer presses in quest of Time Zero, its energy increasing without bound as it penetrates farther into the past. Beyond 10^-13, 10^-14, 10^-15 s AG, it goes, while around it the temperature and density of cosmic matter rise and rise to new inconceivable heights. Trillions of encounters it has, but always these involve the same triad of forces and the same basic set of rules.

Now, at 10^-20 s AG on the exponential time scale, our particle has crossed more orders of magnitude than those that separate humans from the one-second-old universe. Even so, its immense, regressive journey into Deep Time has barely begun.

Still, at 10^-25 s AG, there is no sign of any further qualitative change. The separation of electromagnetism from the weak force now lies at an awesomely remote point in the future. Was it, after all, the first crucial cosmic development, the first-ever step toward great complexity?

And now, farther back our hero flies, to 10^-35 s AG. Suddenly, with the universe ten trillion trillion trillionths of a second old, the question is answered. Just as before the electromagnetic and weak forces conjoined, so now, at this much earlier time, the strong force begins to merge with the electroweak. It is a stunning event – a triumphant triple alliance that brings to the universe, at last, an even simpler and more perfect order.

Now there are only two distinct ways in which any piece of cosmic matter may interact. There is gravity. And there is the grand unified force. Embraced by the latter are all of the attributes previously associated with the strong force and the weak and with electromagnetism. It is as if all the pieces on a chessboard – pawns, rooks, and bishops alike – were given the same freedom to move around and coact as a queen. How could any of the pieces then meaningfully be told apart? When the strong force united with the electroweak that same freedom was bestowed upon the quarks and leptons. Suddenly anything a quark could do a lepton could do equally well. A lepton could even turn into a quark, a quark into a lepton.

In this new democratic universe no longer is our hero particle distinguishable from any of the others with which it interacts. The differences between quarks and leptons, so conspicuous before, have vanished. They are revealed as having been mere facades, skin-deep variations, hiding a common core within.

Yet even as the universe assumes a form still simpler than before, the mystery of its origin and unfolding remain. At 10^-35 s AG all that there is from which to build all there will ever be is this pocket sea of primitive, like particles – the quark-leptons. But what drove these cloned specks of energy to evolve and combine, through many branching levels of complication, into atoms and galaxies and minds? Despite their overt simplicity, the grand-unified particles bear – even at this early stage – the inner potential for what is to follow. Truly they are the spores of the cosmos, the harbingers of complexity to come. But even spores must have an origin, as must the concealed genetic message they carry.

So, to the final stage of our assault on genesis. And now we must venture on alone, forsaking the company of the particle with which we have journeyed thus far. Already it is moving away from us, our last direct link with the cosmos we knew. For a while we watch it still, colliding, merging with its protagonists, then reasserting its individuality once more. And yet no longer can we really be sure whether this is "our" particle or some other that is identical to it in every sense.

So at last we turn away. And prepare our imagination – to accept a universe that has shriveled to the size of a pea. That has become so heated – to 100 trillion trillion degrees – that every particle within it has the energy of a charging bull. And that, like an equatorial dusk, is rapidly about to ...

Darken.

What a stunning, almost biblical, genesis it would have made – this, the brief, spectacular era of the creation of the particles. Here, at 10^-35 s AG, or a little before, most of the matter in the universe, sprang into being. Photons too – explaining, in time reverse, the sudden dimming. As part of the process by which the strong force uncoupled from the electroweak, by which the grand unification was broken, most of the material that the universe would ever contain showered into existence.