Cities in Flight

by James Blish

  And from this conclusion, though Amalfi’s own psyche had been fighting against its acceptance since the moment that he himself had realized it was so, there was really no escape. Conceptually, the universe had been a reasonably comfortable place to live in, in primitive atomic theory which offered the assurance that everything, earth, air, fire or water, steel and oranges, man or star, was ultimately composed of submicroscopic vortices called protons and electrons leavened a little with neutrons and neutrinos which had no charge, and bound together by a disorderly but homely family of mesons. The type case was the hydrogen atom, one proton sitting cosily on the hearth, contentedly positive in charge, while about it wove one electron, surrounded by its negative field like crackling cat’s fur. That was the simple case; but one was assured that even in the heaviest and most complicated atoms, even those man-made ones like plutonium, one need only add more and heavier logs to the fire, and more cats would come droning about it; it would be hard to tell one cat from another, but this is the customary penalty the owner of hundreds pays.

  The first omen that there was something wrong with this chromo of sub-microscopic and universal domesticity appeared, as all good omens should, in the skies. Back on Earth, nearly half a century before space flight, some astronomer whose name is quite lost had noticed that two or three of the millions of meteors that entered Earth’s atmosphere every day exploded at a height and with a violence which could not be accounted for by an eccentricity of orbit or velocity; and in one of those great flights of fancy which account in the long run for every new link in the great chain of understanding, he had a dream of something which he called “contra-terrene” matter—a matter made of fire with cat’s fur, which would be circled by cats in flames: matter in which the fundamental hydrogen atom would have a nucleus which would be an anti-proton, with the mass of a proton but carrying a negative charge, around which would orbit an anti-electron, with the negligible mass of an electron, but carrying a positive charge. A meteor of atoms constructed on this model, he reasoned, would explode with especial violence at the first contact with even the faintest traces of Earth’s normal-matter atmosphere; and such meteors would suggest that somewhere in the universe there were whole planets, whole suns, whole galaxies composed of such matter, whose barest touch would be more than death—would be ultimate and complete annihilation, each form of matter converting the other wholly into energy in a flaming and total embrace.

  Curiously, the contra-terrene meteors died out of the theory shortly thereafter, while the theory itself survived. The exploding meteors were found to be easier to explain in more conventional terms, but anti-matter survived, and by the middle of the Twentieth Century experimental physicists were even able to produce the stuff a few atoms at a time. Those topsy-turvy atoms proved to be nonviable beyond a few millionths of a micro-second, and it gradually became clear that even in this short lifetime the time in which they lived was running backwards. The particles of which they were made were born, in the great clumsy bevatrons of that age, some micro-seconds in the future, and their assembly into atoms of antimatter in the present time of the observers was in fact the moment of their death. Obviously anti-matter was not only theoretically possible, but could exist; but it could not exist in this universe in any assemblage so gross as a meteor; if there were worlds and galaxies made of anti-matter, they existed only in some unthinkable separate continuum where time and the entropy gradient ran backwards. Such a continuum would require at least four extra dimensions, at a minimum, in addition to the conventional four of experience.

  As the universe of normal matter expanded, unwound and ran down toward its inevitable heat-death, somewhere nearby and yet in a “somewhere” unimaginable by man, a duplicate universe as vast and complex was contracting, winding up, approaching the supernal concentration of mass and energy called the monobloc. As complete dispersion, darkness and silence was to be the fate of the universe in which the arrow of time pointed down the entropy gradient, so in the anti-matter universe the end was to be mass beyond mass, energy beyond energy, raw glare and fury to the ultimate power raging in a primeval “atom” no bigger across than the orbit of Saturn. And out of one universe might come the other; in the universe of normal matter the monobloc was the beginning, but in the universe of anti-matter it would be the end; in a universe of normal entropy, the monobloc is intolerable and must explode; in a universe of negative entropy, the heat-death is intolerable and must condense. In either case, the command is: Let there be light.

  What the visible, tangible universe had been like before the monobloc was, however, agreed to be forever unknowable. The classic statement had been refuted many centuries earlier by St. Augustine, who, when asked what God might have been doing before He created the universe, denied that He was constructing a hell for persons who asked such questions; thus “pre-Augustinean time” came to be something that a historian could know all about, but a physicist, by definition, nothing.

  Until now; for if the Hevians were right, they had lifted that curtain a little way and caught an instant’s glimpse of the unknowable.

  To have looked it full in the face could have been no more fatal.

  During the course of their exultant drive upon the Andromeda galaxy, the Hevians had discovered that one of their spindizzies— oddly, it was one of the machines which had been new-built for the project, not one of the old and somewhat abused drivers which had been dismounted from the Okie city—was beginning to run somewhat hot. This was a problem which was then brand new to them, and rather than take chances on the to them unknown effects which might be produced by such a machine were it to run really wild, they shut down their entire spindizzy network while repairs were made, leaving behind only a 0.02 per cent screen necessary to protect the planet’s atmosphere and heat budget.

  And it was then and there, in the utter silences of intergalactic space, that their instruments detected for the first time in human history the whispers of continuous creation: the tiny ping of new atoms of hydrogen being born, one by one, out of nothing at all.

  This would alone and in itself have been a sobering enough experience for any man of a thoughtful cast of mind, even one who lacked the Hevians’ history of preoccupation with religious questions; no one could view the birth of the raw material from which the whole known universe was built, out of what was demonstrably nothingness, without being shaken by the conviction that there must also be a Creator, and that He must be in the immediate vicinity of where His work was proceeding. Those tiny pings and pips in the Hevians’ instruments seemed at first to leave no room in the long arguments of cosmogony and cosmology for any cyclical theory of the universe, any continuous and eternal systole-diastole from mono-bloc to heat-death and back again, with a Creator required only at the remote inception of the rhythmic process, or not at all. Here was creation in process: the invisible Finger touched nothingness, and from nothing came something; the ultimate absurdity, which, because it was ultimate, could be nothing else but divine.

  Yet the Hevians were sophisticated enough to be suspicious. Historically, fundamental discoveries were dependably ambiguous; this discovery, which on the face of it seemed to provide a flat answer to 25,000 years of theological speculation, and in effect to bring God into inarguable being for the first time since He had been postulated by some Stone Age sun-worshipper or mushroom-eating mystic, could not be as simple as it seemed. It had been won too easily; too much else is implied by the continual creating existence of a present God to make it tenable that that existence should be provable by so simple and single a physical datum, arrived at by what could honestly only be described as ordinary accident.

  Gifford Bonner was later to remark that it had been fortunate beyond belief that it had been the Hevians, a people only recently winning back to some degree of scientific sophistication, but which had never lost its sense of the continuity and the overwhelming complexity of theology in a scientific age, who had first been allowed to hear these tiny birth-cries in the nursery
of time. The typical Earthman of the end of the Third Millennium, with his engineer’s bias, philosophically wedded in about equal measure to a sentimentally hard-headed “common sense” and a raw and naive mystique of Progress (it was at about this point in Bonner’s analysis that Amalfi had felt a slight impulse to squirm), might easily have taken the datum at face value and walked the plank on it directly into a morass of telepathy, the racial unconscious, personal reincarnation or any of a hundred other traps which await the scientifically oriented man who does not know that he too is as thorough-going a mystic as a fakir lying on a bed of nails.

  The Hevians were suspicious; they questioned the discovery first of all only on the subject of what it said it was saying. Theology could wait. If continuous creation was a fact, then primarily that ruled out that there should ever have been a monobloc in the history of the universe, or that there should ever be a heat-death; instead, it would always go along like this, world without end. Therefore, if the discovery was as fundamentally ambiguous as all such discoveries before had proven to be, it should in the same breath be implying exactly the opposite; ask it that question, and see what it says.

  This singularly tough-minded approach paid off at once, though the further implications which it offered for inspection proved in no way easier to digest than the first and contrary set had been. Taking a long chance with the still largely unfamiliar machines, and with the precarious life of their entire planet, the Hevians shut down their spindizzies entirely and listened more intently.

  In that utmost of dead silences, the upsetting whisper of continuous creation proved to have two voices. Each pinging birth-pang was not a single note, but a duo. As each atom of hydrogen leapt into being from nowhere into the universe of experience, a sinister twin, a hydrogen atom of anti-matter, came there in that instant to die, from … somewhere else.

  And there it was. Even what had seemed to be fundamental, ineluctable proof of one-way time and continuous creation could also be regarded as inarguable evidence for a cyclical cosmology. In a way, to the Hevians, it was satisfying; this was physics as they knew it to be, an idiot standing at a crossroads shouting “God went that-away!” and managing to point down all four roads at once. Nevertheless, it left them a legacy of dread. This single many-barbed burr of a datum, which could have been obtained under no other circumstances, was also sufficient in itself to endorse the existence of an entire second universe of anti-matter, congruent point for point with the universe of experience of normal matter, but opposite to it in sign. What appeared to have been the birth of a hydrogen atom of anti-matter, simultaneous with the birth of the normal hydrogen atom, was actually its death; there was now no doubt that time ran backwards in the anti-matter universe, and so did the entropy gradient, one being demonstrably a function of the other.

  The concept, of course, was old—so old, in fact, that Amalfi had difficulty in remembering just when in his lifetime it had become so familiar to him that he had forgotten about it entirely. Its revival here by the Hevians struck him at first as an exasperating anachronism, calculated only to get in the way of the real work of practical men. He was in particular rather scornful of the notion of a universe in which negative entropy could be an operating principle; under such circumstances, his rustily squeaking memory pointed out, cause and effect would not preserve even the rough statistical associations which they were allowed in the universe of experience; energy would accumulate, events would undo themselves, water would run uphill, old men would clump into existence out of the air and soil and unlearn their profitless ways back toward their mothers’ wombs.

  “Which is what they do in any event,” Gifford Bonner had said gently. “But actually, I doubt that it’s that paradoxical, Amalfi. Both of these universes can be regarded as unwinding, as running down, as losing energy with each transaction. The fact that from our point of view the anti-matter universe seems to be gaining energy is simply a bias built into the way we’re forced to look at things. Actually these two universes probably are simply unwinding in opposite directions, like two millstones. Though the two arrows of time seem to be pointing in opposite directions, they probably both point downhill, like fingerboards at the crest of a single road. If the dynamics of it bother you, bear in mind that both are four dimensional continua and from that point of view both are wholly static.”

  “Which brings us to the crucial question of contiguity,” Jake said cheerfully. “The point is, these two four-dimensional continua are intimately related, as the twin events the Hevians observed make very plain; which I suppose must mean that we must allow for a total of at least sixteen dimensions to contain the whole system. Which is no particular surprise in itself; you need at least that many to accommodate the atomic nucleus of average complexity comfortably. What is surprising is that the two continua are approaching each other; I agree with Miramon that the observations his people made can’t be interpreted any other way; up to now, the fact that gravitation in the two universes is also opposite in sign seems to have kept them apart, but that repulsion or pressure or whatever you want to call it is obviously growing steadily weaker. Somewhere in the future, the near future, it will decline to zero, there will be a Pythagorean point-for-point collision between the two universes as a whole—”

  “—and it’s hard to imagine how any physical framework, even one that allows sixteen dimensions of elbowroom, will be able to contain the energy that’s going to be released,” Dr. Schloss said. “The monobloc isn’t even in the running; if it ever existed, it was just a wet firecracker by comparison.”

  “Translation: blooey,” Carrel said.

  “It’s perfectly possible that a rational cosmology is going to have to accommodate all three events,” Gifford Bonner said. “I mean by that the monobloc, the heat death, and this thing—this event that seems to fall midway between the two. Curious; there are a number of myths, and ancient philosophical systems, that allow for such a break or discontinuity right in the middle of the span of existence; Giordano Bruno, Earth’s first relativist, called it the period of Inter-destruction, and a compatriot of his named Vico allowed for it in what was probably the first cyclical theory of ordinary human history; and in Scandanavian mythology it was called the Ginnangu-Gap. But I wonder, Dr. Schloss, if the destruction is going to be quite as total as you suggest. I am nobody’s physicist, I freely confess, but it seems to me that if these two universes are opposite in sign at every point, as everyone at this meeting has been implying, then the result cannot be only a general transformation of the matter on both sides into energy. There will be energy transformed into matter, too, on just as large a scale, after which the gravitational pressure should begin to build up again and the two universes, having in effect passed through each other and exchanged hats, will begin retreating from each other once more. Or have I missed something crucial?”

  “I’m not sure that the argument is as elegant as it appears on the surface,” Retma said. “That awaits Dr. Schloss’s mathematical analysis, of course; but in the meantime I cannot help but wonder why, for instance, if this simultaneous creation-interdestruction-destruction cycle is truly cyclical, it should have this ornamental waterspout of continuous creation attached to it? A machinery of creation which involves no less than three universal cataclysms in each cycle should not need to be powered by a sort of continuous drip; either the one is too grandiose, or the other is insufficient. Besides, continuous creation implies a steady state, which is irreconcilable.”

  “I don’t know about that,” Jake said. “It doesn’t sound like anything the Milne transformations couldn’t handle; it’s probably just a clock function.”

  “Defined, as I recall, as a mathematical expression about the size of a bottle of aspirin,” Carrel said ruefully.

  “Well, there’s one thing I’m perfectly certain of,” Amalfi growled, “and that is that it’s damned unlikely anybody is going to be around to care about the exact results of the collision after it happens. At least not at the rate this hassl
e is going. Is there actually anything useful that we can do, or would we be better off spending all this time playing poker?”

  “That,” Miramon said, “is exactly what we know least about. In fact it would appear that we know nothing about it whatsoever.”

  “Mr. Miramon—” Web Hazleton’s voice spoke from the shadows and stopped. Obviously he was waiting to be told that he was breaking his promise not to interrupt, but it was as plain to Amalfi as it was to the rest of the group that he was interrupting nothing now; his voice had broken only a dead and despairing silence.

  “Go ahead, Web,” Amalfi said.

  “Well, I was just thinking. Mr. Miramon came here looking for somebody to help him do something he doesn’t know how to do himself. Now he thinks we don’t know how to do it either. But what was it?”

  “He’s just said that he doesn’t know,” Amalfi said gently.

  “That isn’t what I mean,” Web said hesitantly. “What I mean is, what would he like to do, even if he doesn’t know how to do it? Even if it’s impossible?”

  Bonner’s voice chuckled softly in the still shipboard air. “That’s right,” he said, “the ends determine the means. A hen is only an egg’s device for producing another egg. Is that Hazleton’s grandson? Good for you, Web.”

  “There are a good many experiments that ought to be performed, if only we knew how to design them,” Miramon admitted thoughtfully. “First of all, we ought to have a better date for the catastrophe than we have now; ‘the near future’ is a huge block of time under these conditions, almost as shapeless a target as ‘sometime��; we would need it defined to the millisecond just to begin with. I applaud the young Earthman’s brilliant common sense, but I refuse to delude myself by asking for more than that; even that seems hopeless.”