Imperial Earth

A r t h u r C. C l a r k e

Imperial Earth

Contents

I Titan

01 A Shriek In The Night

02 Dynasty

03 Invitation To A Centennial

04 The Red Moon

05 The Politics of Time And Space

06 By The Bonny, Bonny Banks of Lock Hellbrew

07 A Cross of Titanite

08 Children of The Corridors

09 The Fatal Gift

10 World's End

II Transit

11 Sirius

12 Last Words

13 The Longest Voyage

14 Songs of Empire

15 At The Node

16 Port Van Allen

III Terra

17 Washington, D.C.

18 Embassy

19 Mount Vernon

20 The Taste of Honey

21 History Lesson

22 Budget

23 Daughters of The Revolution

24 Calindy

25 Mystery Tour

26 Primeval Forest

27 The Ghost From The Grand Banks

28 Akhenaton And Cleopatra

29 Party Games

30 The Rivals

31 The Island of Dr. Mohammed

32 Golden Reef

33 Sleuth

34 Star Day

35 A Message From Titan

36 The Eye of Allah

37 Meeting At Cyclops

38 The Listeners

39 Business And Desire

40 Argus Panoptes

41 Independence Day

42 The Mirror of The Sea

IV Titan

43 Homecoming

"Remember them as they were; and write them off."

—Ernest Hemingway

"For every man has business and desire."

— Hamlet, Act I, Scene 4

Part One

Titan

1

A Shriek In The Night

Duncan McKenzie was ten years old when he found the magic number. It was pure chance; he had intended to call Grandma Ellen, but he had been careless and his fingers must have touched the wrong keys. He knew at once that he had made a mistake, because Grandma's viddy had a two-second delay, even on Auto/Record. This circuit was live immediately.

Yet there was no ringing tone, and no picture. The screen was completely blank, with not even a speckling of interference. Duncan guessed that he had been switched into an audio-only channel, or had reached a station where the camera was disconnected. In any case, this certainly wasn't Grandma's number, and he reached out to break the circuit.

Then he noticed the sound. At first, he thought that someone was breathing quietly into the microphone at the far end, but he quickly realized his mistake. There was a random, inhuman quality about this gentle susurration; it lacked any regular rhythm, and there were long intervals of complete silence.

As he listened, Duncan felt a growing sense of awe. Here was something completely outside his normal, everyday experience, yet he recognized it almost at once. In his ten years of life, the impressions of many worlds had been imprinted on his mind, and no one who had heard this most evocative of sounds could ever forget it. He was listening to the voice of the wind, as it sighed and whispered across the lifeless landscape a hundred meters above his head.

Duncan forgot all about Grandma, and turned the volume up to its highest level. He lay back on the couch, closed his eyes, and tried to project himself into the unknown, hostile world from which he was protected by all the safety devices that three hundred years of space technology could contrive. Someday, when he had passed his survival tests, he would go up into that world and see with his own eyes the lakes and chasms and low-lying orange clouds, lit by the thin, cold rays of the distant sun. He had looked forward to that day with calm anticipation rather than excitement — the Makenzies were noted for their lack of excitement — but now he suddenly realized what he was missing. So might a child of Earth, on some dusty desert far from the ocean, have pressed a shell against his ear and listened with sick longing to the music of the unattainable sea.

There was no mystery about the sound, but how was it reaching him? It could be coming from any of the hundred million square kilometers lying above his head. Somewhere — perhaps in an abandoned construction project or experimental station — a live microphone had been left in circuit, exposed to the freezing, poisonous winds of the world above. It was not likely to remain undetected for long; sooner or later it would be discovered and disconnected. He had better capture this message from the outside while it was still there; even if he knew the number he had accidentally called, he doubted if he could ever establish the circuit again.

The amount of audio-visual material that Duncan had stored under MISC was remarkable, even for an inquisitive ten-year-old. It was not that he lacked organizing ability — that was the most celebrated of all the Makenzie talents — but he was interested in more things than he knew how to index. He had now begun to discover, the hard way, that information not properly classified can be irretrievably lost.

He thought intently for a minute, while the lonely wind sobbed and moaned and brought the chill of space into his warm little cubicle. Then he tapped out ALPHA INDEX* WIND SOUNDS* PERM STORE #.

From the moment he touched the # or EXECUTE key, he had begun to capture that voice from the world above. If all went well, he could call it forth again at any time by using the index heading WIND SOUNDS. Even if he had made a mistake, and the console's search program failed to locate the recording, it would be somewherein the machine's permanent, nonerasable memory. There was always the hope that he might one day find it again by chance, as was happening all the time with information he had filed under MISC.

He decided to let the recording run for another few minutes before completing the interrupted call to Grandma. As luck would have it, the wind must have slackened at about the time he keyed EXECUTE, because there was a long, frustrating silence. Then, out of that silence, came something new.

It was faint and distant, yet conveyed the impression of overwhelming power. First there was a thin scream that mounted second by second in intensity, but somehow never came any closer. The scream rose swiftly to a demonic shriek, with undertones of thunder — then dwindled away as quickly as it had appeared. From beginning to end it lasted less than half a minute. Then there was only the sighing of the wind, even lonelier than before.

For a long, delicious moment, Duncan savored the unique pleasure of fear without danger; then he reacted as he always did when he encountered something new or exciting. He tapped out Karl Helmer's number, and said: "Listen to this."

Three kilometers away, at the northern end of Oasis City, Karl waited until the thin scream died into silence. As always, his face gave no hint of his thoughts. Presently he said: "Let's hear it again."

Duncan repeated the playback, confident that the mystery would soon be solved. For Karl was fifteen, and therefore knew everything.

Those dazzling blue eyes, apparently so candid yet already so full of secrets, looked straight at Duncan. Karl's surprise and sincerity were totally convincing as he exclaimed: "You didn't recognize it?"

Duncan hesitated. He had thought of several obvious possibilities — but if he guessed wrongly, Karl would make fun of him. Better to be on the safe side...

"No," he answered. "Did you?"

"Of course," said Karl, in his most superior tone of voice. He paused for effect, then leaned toward the camera so that his face loomed enormous on the screen.

"It's a Hydrosauruson the rampage."

For a fraction of a second, Duncan took him seriously — which was exactly what Karl had intended. He quickly recovered, and laughed back at his friend.

"You're crazy. So you don't know what it is?"

For the methane-breathing monster Hydrosaurus rexwas their private joke — the product of youthful imaginations, inflamed by pictures of ancient Earth and the wonders it had brought forth near the dawn of creation. Duncan knew perfectly well that nothing lived now, or had ever lived, on the world that he called home; only Man had walked upon its frozen surface. Yet if Hydrosauruscould have existed, that awesome sound might indeed have been its battle cry, as it leaped upon the gentle Carbotherium, wallowing in some ammonia lake...

"Oh. Iknow what made that noise," said Karl smugly. "Didn't you guess? That was a ram-tanker making a scoop. If you call Traffic Control, they'll tell you where it was heading."

Karl had had his fun, and the explanation was undoubtedly correct. Duncan had already thought of it, yet he had hoped for something more romantic. Though it was perhaps too much to expect methane monsters, and everyday spaceship was a disappointing anticlimax. He felt a sense of letdown, and was sorry that he had given Karl another chance to deflate his dreams. Karl was rather good at that.

But like all healthy ten-year-olds, Duncan was resilient. The magic had not been destroyed. Though the first ship had lifted from Earth three centuries before he was born, the wonder of space had not yet been exhausted. There was romance enough in that shriek from the edge of the atmosphere, as the orbiting tanker collected hydrogen to power the commerce of the Solar System.

In a few hours, that precious cargo would be falling sunward, past Saturn's other moons, past giant Jupiter, to make its rendezvous with one of the fueling stations that circled the inner planets. It would take months — even years — to get there, but there was no hurry. As long as cheap hydrogen flowed through the invisible pipeline across the Solar System, the fusion rockets could fly from world to world, as once the ocean liners had plied the seas of Earth.

Duncan understood this better than most boys of his age; the hydrogen economy was also the story of his family, and would dominate his own future when he was old enough to play a part in the affairs of Titan. It was now almost a century since Grandfather Malcolm had realized that Titan was the key to all the planets, and had shrewdly used this knowledge for the benefit of mankind — and of himself.

So Duncan continued to listen to the recording after Karl had switched off. Over and over again he played back that triumphant cry of power, trying to detect the precise moment when it was finally swallowed up in the gulfs of space. For years it would haunt his dreams; he would wake in the night, convinced that he had heard it again through the rock that protected Oasis from the hostile wilderness above.

And when he at last fell back into sleep, he would always dream of Earth.

2

Dynasty

Malcolm Makenzie had been the right man, at the right time. Others before him had looked covetously at Titan, but he was the first to work out all the engineering details and to conceive the total system or orbiting scoops, compressors, and cheap, extendable tanks that could hold their liquid hydrogen with minimum loss as they dropped leisurely sunward.

Back in the 2180's, Malcolm had been a promising young aerospace designer at Port Lowell, trying to make aircraft that could carry useful payloads in the tenuous Martian atmosphere. In those days he had been Malcolm Mackenzie, for the computer mishap that had irrevocably changed the family name did not occur until he emigrated to Titan. After wasting five years in futile attempts at correction, Malcolm had finally co-operated with the inevitable. It was one of the few battles in which the Makenzies had ever admitted defeat, but now they were quite proud of their unique name.

When he had finished his calculations and stolen enough drafting-computer time to prepare a beautiful set of drawings, young Malcolm had approached the Planning Office of the Martian Department of Transportation. He did not anticipate serious criticism, because he knew that his facts and his logic were impeccable.

A large fusion-powered spaceliner could use ten thousand tons of hydrogen on a single flight, merely as inert working fluid. Ninety-nine percent of it took no part in the nuclear reaction, but was hurled from the jets unchanged, at scores of kilometers per second, imparting momentum to the ships it drove between the planets.

There was plenty of hydrogen on Earth, easily available in the oceans; but the cost of lifting megatons a year into space was horrendous. And the other inhabited worlds — Mars, Mercury, Ganymede, and the Moon — could not help. The had no surplus hydrogen at all.

Of course, Jupiter and the other Gas Giants possessed unlimited quantities of the vital element, but their gravitational fields guarded it more effectively than any unsleeping dragon, coiled round some mythical treasure of the Gods. In all the Solar System, Titan was the only place where Nature had contrived the paradox of low gravity and an atmosphere remarkably rich in hydrogen and its compounds.

Malcolm was right in guessing that no one would challenge his figures, or deny the feasibility of the scheme, but a kindhearted senior administrator took it upon himself to lecture young Makenzie on the political and economic facts of life. He learned, with remarkable speed, about growth curves and forward discounting and interplanetary debts and rates of depreciation and technological obsolescence, and understood for the first time why the solar was backed, not by gold, but by kilowatt-hours.

"It's an old problem," his mentor had explained patiently. "In fact, it goes back to the very beginnings of astronautics, in the twentieth century. We couldn't have commercial space flight until there were flourishing extraterrestrial colonies — and we couldn't have colonies until there was commercial space transportation. In this sort of bootstrap situation, you have a very slow growth rate until you reach the takeoff point. Then, quite suddenly, the curves start shooting upward, and you're in business.

"It could be the same with your Titan refueling scheme — but have you any idea of the initial investment required? Only the World Bank could possibly underwrite it..."

"What about the Bank of Selene? Isn't it supposed to be more adventurous?"

"Don't believe all you've read about the Gnomes of Aristarchus; they're as careful as anyone else. They haveto be. Bankers on Earth can still go on breathing if they make a bad investment..."

But it was the Bank of Selene, three years later, that put up the five megasols for the initial feasibility study Then Mercury became interested — and finally Mars. By this time, of course, Malcolm was no longer an aerospace engineer. He had become, not necessarily in this order, a financial expert, a public-relations adviser, a media manipulator, and a shrewd politician. In the incredibly short time of twenty years, the first hydrogen shipments were falling sunward from Titan.

Malcolm's achievement had been an extraordinary one, now well documented in dozens of scholarly studies, all respectful, though some of them far from flattering. What made it so remarkable — even unique — was the way in which he had converted his hard-won expertise from technology to administration. The process had been so imperceptible that no one realized what was happening. Malcolm was not the first engineer to became a head of state; but he was the first, his critics pointed out, to establish a dynasty. And he had done so against odds that would have daunted lesser men.

In 2195, at the age of forty-four, he had married Ellen Killner, recently emigrated from Earth. Their daughter, Anitra, was the first child to be born in the little frontier community of Oasis, then the only permanent base on Titan, and it was several years before the devoted parents realized the cruel jest that Nature had played upon them.

Even as a baby, Anitra was beautiful, and it was confidently predicted that when she grew up she would be completely spoiled. Needless to say, there were as yet no child psychologists on Titan; so no one noticed that the little girl was too docile, too well behaved — and too silent. Not until she was almost four years old did Malcolm and Ellen finally accept the fact that Anitra would never be able to speak, and that there was really no one at home in the lovely shell their bodies had fashioned.

The fault lay in Malcolm's genes, not Ellen's. Sometime during his shuttling back and forth between Earth and Mars, a stray photon that had been cruising through space since cosmic dawn had blasted his hopes for the future. The damage was irreparable, as Malcolm discovered when he consulted the best genetic surgeons of four worlds. It was a chilling thought that he had actually been lucky with Anitra; the results could have been far, far worse...

To the mingled sorrow and relief of an entire world, Anitra had died before she was six years old, and the Makenzie marriage died with her in a flurry of grief and recrimination. Ellen threw herself into her work, and Malcolm departed on what was to be his last visit to Earth. He was gone for almost two years, and in that time he achieved much.

He consolidated his political position and set the pattern of economic development on Titan for the next half-century. And he acquired the son he had now set his heart upon.

Human cloning — the creation of exact replicas of another individual from any cell in the body except the sex cells — had been achieved early in the twenty-first century. Even when the technology had been perfected, it had never become widespread , partly because there were few circumstances that could ever justify it.

Malcolm was not a rich man — there had been no large personal fortunes for a hundred years — but he was certainly not poor. He used a skillful combination of money, flattery, and more subtle pressures to attain his goal. When he returned to Titan, he brought with him the baby who was his identical twin — but a half a century younger.

When Colin grew up, there was no way in which he could be distinguished from his clone father at the same age. Physically, he was an exact duplicate in every respect. But Malcolm was no Narcissus, interested in creating a mere carbon copy of himself; he wanted a partner as well as a successor. So Colin's educational program concentrated on the weak points of Malcolm's. Though he had a good grounding in science, he specialized in history, law, and economics. Whereas Malcolm was an engineer-administrator, Colin was an administrator-engineer. While still in his twenties, he was acting as his father's deputy wherever it was legally admissible, and sometimes where it was not. Together, the two Makenzies formed an unbeatable combination, and trying to draw subtle distinctions between their psychologies was a favorite Titanian pastime.

Perhaps because he had never been compelled to fight for any great objective, and had had all his goals formulated before his birth, Colin was more gentle and easygoing than Malcolm — and therefore more popular. No one outside the Makenzie family ever called the older man by his first name; few called Colin anything else. He had no real enemies, and there was only one person on Titan who disliked him. At least, it was assumed that Malcolm's estranged wife, Ellen, did so, for she refused to acknowledge his existence.

Perhaps she regarded Colin as a usurper, an unacceptable substitute for the son who could never be born to her. If so, it was indeed strange that she was so fond of Duncan.

But Duncan had been cloned from Colin almost forty years later and by that time Ellen had passed through a second tragedy — one that had nothing to do with the Makenzies. To Duncan, she was always GrandmaEllen, but he was now old enough to realize in his heart she combined two generations, and filled a void that earlier ages would have found it impossible to imagine or believe.

If Grandma had any real genetic relationship with him, all trace of it had been lost centuries ago on another world. And yet, by some strange quirk of chance and personality, she had become for him the phantom mother who had never even existed.

3

Invitation To A Centennial

"And who the hell is George Washington?" asked Malcolm Makenzie.

"Middle-aged Virginia farmer, runs a place called Mount Vernon—"

"You're joking."

"I'm not. No relation, of course — old George was childless — but that's his real name, and he's perfectly genuine."

"I suppose you've checked with the embassy."

"Of course, and got a fifty-line print-out of his family tree. Most impressive — half the American aristocracy for the last hundred years. Lots of Cabots and Du Ponts and Kennedys and Kissingers. And before that, a couple of African kings."

"It may impress you, Colin," interjected Duncan, "but now that I've glanced at the program, it all seems a little childish. Grown men pretending to be historical figures. Are they reallygoing to throw tea into Boston Harbor?"

Before Colin could answer, Grandfather Makenzie stepped in. A discussion among the three Makenzies — which was something seldom overheard by outsiders — was more in the nature of a monologue than an argument. Because their three personas differed only through the accidents of background and education, genuine disagreements among them were virtually unknown. When difficult decisions had to be made, Duncan and Colin would take opposing viewpoints and debate them before Malcolm — who would listen without saying a word, though his eyebrows could be very eloquent. He seldom had to give a judgment, because the two advocates usually reached a synthesis without much difficulty; but when he did, that was the end of the matter. It was quite a good way to run a family — or a world.

"I don't know about the tea, which would certainly be a waste at fifty solars a kilo, but you're being too hard on Mr. Washington and his friends. When wehave five hundred years behind us, we'll be justified in a little pomp and ceremony. And never forget — the Declaration of Independence was one of the most important historical events of the last three thousand years. Wewouldn't be here without it. After all, the Treaty of Phobos opens with the words: When in the course of human events, it becomes necessary for one people..."

"Quite inappropriate in that context. On the whole, Earth was heartily glad to get rid of us."

"Perfectly true, but don't ever let the Terrans hear it."

"I'm still confused," said Duncan rather plaintively. "Just what does the good general want from us? How can we raw colonials contribute to the proceedings?"

"He's only a professor, not a general," replied Colin. "They're extinct, even on Earth. As I see it, a few nicely composed speeches, drawing whatever parallels you can find between our historical situations. A certain exotic charm — you know; a whiff of the frontier, where men still live dangerously. The usual barbarian virility, so irresistible to decadent Terrans of all sexes. And, not least, a low-keyed yet genuine gratitude for the unexpected gift of an open Earth-Titan return ticket with all expenses for a two-month stay. That solves several of our problems, and we should appreciate it."

"Very true," Duncan replied thoughtfully, "even though it wrecks our plans for the next five years."

"It doesn't wreck them," said Colin. "It advances them. Time gained is time created. And success in politics—"

"—depends upon the masterful administration of the unforeseen, as you are so fond of saying. Well, this invitation is certainly unforeseen, and I'll try to master it. Have we sent an official thank you?"

"Only a routine acknowledgment. I suggest that you follow it up, Duncan, with a personal note to President — er — Professor Washington."

"They're both right," said Malcolm, rereading the formal invitation. "It says here: ‘Chairman of the Quincentennial Celebration Committee, and President of the Historical Association of Virginia." So you can take your choice."

"We've got to be very careful about this, or someone will bring it up in the Assembly. Was the invitation official, or personal?"

"It's not government to government, I'm happy to say, since the Committee sponsored it. And the fax was addressed to the Honorable Malcolm Makenzie, notto the President." The Honorable Malcolm Makenzie, also President of Titan, was clearly pleased at this subtle distinction.

"Do I detect in this the fine hand of your good friend Ambassador Farrell?" asked Colin.

"I'm sure the idea never occurred to him."

"I thought as much. Well, even if we are on firm legal grounds, that won't stop the objections. There will be the usual cries of privilege, and we'll be accused once again of running Titan for our personal benefit."

"I'd like to know who started the word ‘fiefdom’ circulating. I had to look it up."

Colin ignored the older man's interruption. As Chief Administrator, he had to face the day-to-day problems of running the world, and could not afford the slight irresponsibility that Malcolm was beginning to show in his old age. It was not senility — Grandfather was still only a hundred and twenty-four — but rather, the carefree, Olympian attitude of one who had seen and experienced everything, and had achieved all his ambitions.

"There are two points in our favor," Colin continued. "No official funds are involved, so we can't be criticized for using government money. And let's have no false modesty — Earth will expecta Makenzie. It might even be regarded as an insult if one of us didn't go. And as Duncan is the only possibility, that settles the matter."

"You're perfectly correct, of course. But not everyone will see it that way. All the families will want to send their younger sons and daughters."

"There's nothing to stop them," Duncan interjected.

"How many could afford it? Wecouldn't."

"We could if we didn't have some expensive extras in mind. So can the Tanaka-Smiths, the Mohadeens, the Schwartzes, the Deweys..."

"But not, I believe, the Helmers."

Colin spoke lightly, but without humor, and there was a long silence while all three Makenzies shared a single thought. Then Malcolm said slowly: "Don't underrate Karl. We have only power and brains. But he has genius, and that's always unpredictable."

"But he's crazy," protested Duncan. "The last time we met, he tried to convince me that there's intelligent life on Saturn."

"Did he succeed?"

"Almost."

"If he's crazy — which I doubt, despite that famous breakdown — then he's even more dangerous. Especially to you, Duncan."

Duncan made no attempt to answer. His wiser and older twins understood his feelings, even if they could never fully share them.

"There is one other point," said Malcolm thoughtfully, "and it may be the most important of all. We may have only ten years in which to change the whole basis of our economy. If you can find an answer to this problem on your trip — even a hintof an answer! — you'll be a hero when you come home. No one will criticize any of your other activities, public or private."

"That's a tall order. I'm not a magician."

"Then perhaps you'd better start taking lessons. If the Asymptotic Drive isn't pure magic, I don't know what is."

"Just a minute!" said Colin. "Isn't the first A-Drive ship going to be here in just a few weeks?"

"The second. There was that freighter, Fomalhaut. I went aboard, but they wouldn't let me see anything. Siriusis the first passenger liner — she enters parking orbit — oh — in about thirty days."

"Could you be ready by then, Duncan?"

"I very much doubt it."

"Of course you can."

"I mean phy si ologically. Even on a crash program, it takes months to prepare for Earth gravity."

"Um.. But this is far too good an opportunity to miss — everything is falling into place beautifully. After all, you were born on Earth."

"So were you. And how long did youtake to get ready when you went back?"

Colin sighed.

"It seemed like ages, but by now they must have improved the techniques. Don't they have neuroprogramming while you sleep?"

"It's supposed to give you horrible dreams, and I'll need all the sleep I can get. Still, what's good for Titan..."

He had no need to complete the quotation, which had been coined by some unknown cynic half a century ago. In thirty years, Duncan had never really doubted this old clichй — once intended to wound, now virtually adopted as a family motto.

What was good for the Makenzies was indeed good for Titan.

4

The Red Moon

Of the eighty-five known natural satellites, only Ganymede, lord of the Jovian system, exceeds Titan in size — and that by a narrow margin. But in another respect Titan has no rivals; no other moon of anyplanet has more than a trace of atmosphere. Titan's is so dense that if it were made of oxygen, it would be easy for man to breathe.

When this fact was discovered, late in the twentieth century, it presented the astronomers with a first-class mystery. Why should a world not much larger than the Earth's totally airless Moon be able to hold onto anyatmosphere — particularly one rich in hydrogen, lightest of all gases? It should long ago have leaked away into space.

Nor was that the only enigma. Like the Moon, almost all other satellites are virtually colorless, covered with rock and dust shattered by ages of meteoric bombardment. But Titan is red— as red as Mars, whose baleful glare reminded men in ancient times of bloodshed and of war.

The first robot probes solved some of Titan's mysteries, but, as is always the case, raised a host of new problems. The red color came from a layer of low, thick clouds, made from much the same bewildering mixture of organic compounds as the Great Red Spot of Jupiter. Beneath those clouds was a world more than a hundred degrees hotter than it had any right to be; indeed, there were regions of Titan where a man needed little more than an oxygen mask and a simple thermofoil suit to move around in the open. To everyone's great surprise, Titan had turned out to be the most hospitable place in the Solar System, next to Earth itself.

Part of the unexpected warmth came from the greenhouse effect, as the hydrogenous atmosphere trapped the feeble rays of the distant sun. But a good deal more was due to internal sources; the equatorial region of Titan abounded in what, for want of a better phrase, might be called cold volcanoes. On rare occasions, indeed, some of them actually erupted liquid water.

This activity, triggered by radioactive heat generated deep in the core of Titan, spewed megatons of hydrogen compounds into the atmosphere, and so continually made up for the leakage into space. One day, of course, the buried reserves — like the lost oil fields of Earth — would all be gone, but the geologists had calculated that Titan could hold the vacuum of space at bay for at least two billion years. Man's most vigorous atmospheric mining activities would have only a negligible influence on this figure.

Like the Earth, Titan has distinct seasons — though it is difficult to apply the word “summer” where the temperature at high noon seldom climbs to fifty below. And as Saturn takes almost thirty years to circle the sun, each of the Titanian seasons is more than seven Terran years in length.

The tiny sun, taking eight days to cross the sky, is seldom visible through the cloud cover, and there is very little temperature difference between day and night — or, for that matter, between Poles and Equator. Titan thus lacks climate; but it can, on occasion, produce its own quite spectacular brand of weather.

The most impressive meteorological phenomenon is the so-called Methane Monsoon, which often — though not invariably — occurs with the onset of spring in the northern hemisphere. During the long winter, some of the methane in the atmosphere condenses in local cold spots and forms shallow lakes, up to a thousand kilometers square but seldom more than a few meters deep, and often covered with fantastically shaped bergs and floes of ammonia ice. However, it requires the exceedingly low temperature of minus a hundred and sixty to keep methane liquefied, and no part of Titan is ever that cold for very long.

A “warm” wind, or a break in the clouds — and the methane lakes will flash suddenly into vapor. It is as if, on Earth, one of the oceans were to evaporate, abruptly increasing its volume hundreds of times and so completely changing the state of the atmosphere. The result would be catastrophic, and on Titan it is sometimes scarcely less so. Wind speeds of up to five hundred kilometers an hour have been recorded — or to be accurate, estimated from their aftereffects. They last only for a few minutes; but that is quite long enough. Several of the early expeditions were annihilated by the monsoon, before it became possible to predict its onset.

Before the first landings on Titan, at the beginning of the twenty-first century, some optimistic exobiologists had hoped to find life around the relatively warm oases that were known to exist. This hope was slow to fade, and for a while it was revived by the discovery of the strange wax formations of the famous Crystal Caves. But by the end of the century, it was quite certain that no indigenous life forms had ever existed on Titan.

There had never been any expectation of finding life on the other moons, where conditions were far more hostile. Only Iapetus and Rhea, less than half the size of Titan, had even a trace of atmosphere. The remaining satellites were barren aggregates of rock, overgrown snowballs, or mixtures of both. By the mid-2200's, more than forty had been discovered, the majority of them less than a hundred kilometers in diameter. The outer ones — twenty million kilometers from Saturn — all moved in retrograde orbits and were clearly temporary visitors from the asteroid belt; there was much argument as to whether they should be counted as genuine satellites at all. Though some had been explored by geologists, many had never been examined, except by robot space probes, but there was no reason to suppose that they held any great surprises.

Perhaps one day, when Titan was prosperous and getting a little dull, future generations would take up the challenge of these tiny worlds. Some optimists had talked of turning the carbon-rich snowballs into orbital zoos, basking beneath the warmth of their own fusion suns and teeming with strange life forms. Others had dreamed of private pleasure domes and low-gravity resorts, and islands in space for experiments in super-technology life styles. But these were fantasies of a Utopian future; Titan needed all its energies now to solve its coming crisis, in this demimillennial year of 2276.

5

The Politics of Time And Space

When only two Makenzies were talking together, their conversation was even more terse and telegraphic than when all three were present. Intuition, parallel thought processes, and shared experience filled in gaps that would have made much of their discourse wholly unintelligible to outsiders.

"Handle?" asked Malcolm.

"We?!" retorted Colin.

"Thirty-one? Boy!"

Which might be translated into plain English as:

"Do you think he can handle the job?"

"Have you any doubts that wecould?"

"At thirty-one? I'm not so sure. He's only a boy."

"Anyway, we've no choice. This is a God-sent — or Washington-sent — opportunity that we can't afford to miss. He'll have to get a crash briefing on Terran affairs, learn all that's necessary about the United States..."

"That reminds me — what isthe United States these days? I've lost count."

"Now there are forty-five states — Texas, New Mexico, Alaska, and Hawaii have rejoined the Union, at least for the Centennial year."

"Just what does that mean, legally?"

"Not very much. They pretend to be autonomous, but pay their regional and global taxes like everyone else. It's a typical Terran compromise."

Malcolm, remembering his origins, sometimes found it necessary to defend his native world against such cynical remarks.

"I often wish we had a little more Terran compromise here. It would be nice to inject some in Cousin Armand."

Armand Helmer, Controller of Resources, was not in fact a cousin of Malcolm's, but a nephew of his ex-wife, Ellen. However, in the closed little world of Titan everyone except recent immigrants was related to everybody else, and the designations “uncle,” “aunt,” “nephew,” “cousin” were tossed around with cheerful inaccuracy.

"Cousin Armand," said Colin with some satisfaction, "is going to be very upset when he learns that Duncan is on his way to Earth."

"And what will he do about it?" Malcolm asked softly.

It was a good question, and for a moment both Makenzies brooded over the deepening rivalry between their family and the Helmers. In some ways, it was commonplace enough; both Armand and his son, Karl, were Terran-born, and had brought with them across a billion kilometers that maddening aura of superiority that was so often the hallmark of the mother world. Some immigrants eventually managed to eradicate it, thought the process was difficult. Malcolm Makenzie had succeeded only after three planets and a hundred years, but the Helmers had never even tried. And although Karl had been only five years old when he left Earth, he seemed to have spent the subsequent thirty trying to become more Terran than the Terrans. Nor could it have been a coincidence that all his wives had been from Earth.

Yet this had been a matter of amusement, rather than annoyance, until only a dozen years ago. As boys, Duncan and Karl had been inseparable, and there had been no cause for conflict between the families until Armand's swift rise through the technological hierarchy of Titan had brought him into a position of power. Now the Controller did not bother to conceal his belief that three generations of Makenzies were enough. Whether or not he had actually coined the “What's good for the Makenzies...” phrase, he certainly quoted it with relish.

To do Armand justice, his ambitions seemed more concentrated on his only son than on himself. That alone would have been sufficient to put some strains on the friendship between Karl and Duncan, but it would probably have survived paternal pressures from either direction. What had caused the final rift was still something of a mystery, and was associated with a psychological breakdown that Karl had experienced fifteen years ago.

He had emerged from it with all his abilities intact, but with a marked change of personality. After graduating with honors at the University of Titan, he had become involved in a whole range of research activities, from measurements of galactic radio waves to studies of the magnetic fields around Saturn. All this work had some practical relevance, and Karl had also played a valuable role in the establishment and maintenance of the communications network upon which Titanian life depended. It would be true to say, however, that his interests were theoretical rather than practical, and he sometimes tried to exploit this whenever the old "Two Cultures" debate raised its hoary head.

Despite a couple of centuries of invective from both sides, no one really believed that Scientists, with a capital S, were more cultured (whatever that meant) than Engineers. The purity of theoretical knowledge was a philosophical aberration which would have been laughed out of court by those Greek thinkers who had had it foisted on them more than a thousand years earlier. The fact that the greatest sculptor on Earth had begun his career as a bridge designer, and the best violinist on Mars was still doing original work in the theory of numbers, proved exactly nothing one way or the other. But the Helmers liked to argue that it was time for a change; the engineers had run Titan for long enough, and theyhad the perfect replacement, who would bring intellectual distinction to his world.

At thirty-six, Karl still possessed the charm that had captivated all his peers, but it seemed to many — and certainly to Duncan — that this was now underlined by something hard, calculating, and faintly repellent. He could still be loved, but he had lost the ability to love; and it was strange that none of his spectacular marriages had produced any offspring.

If Armand hoped to challenge the Makenzie regime, Karl's lack of an heir was not his only problem. Whatever the Seven Worlds might say about their independence, the center of power was still on Earth. As, two thousand years ago, men had once gone to Rome in search of justice, or prestige, or knowledge, so in this age the Imperial planet called to its scattered children. No man could be taken seriously in the arena of Solar politics unless he was personally acquainted with the key figures of Terran affairs, and had traced his way at least once through the labyrinth of the terrestrial bureaucracy.

And to do this, one hadto go to Earth; as in the days of the Caesars, there was no alternative. Those who believed otherwise — or pretended to — risked being tagged with the dreaded word “colonial.”

It might have been different if the velocity of light were infinite; but it was a mere billion kilometers an hour — and therefore, realtime conversation would be forever impossible between Earth and anyone beyond the orbit of the Moon. The global electronic village which had existed for centuries on the mother world could never be extended into space; the political and psychological effects of this were enormous, and still not fully understood.

For generations, earth-dwellers had been accustomed to being in each other's presence at the touch of a button. The communications satellites had made possible, and then inevitable, the creation of the World State in all but name. And despite many earlier fears, it was a state still controlled by men, not by machines.

There were perhaps a thousand key individuals, and ten thousand important ones — and they talked to each other incessantly from Pole to Pole. The decisions needed to run a world sometimes had to be made in minutes, and for this the instantaneous feedback of face-to-face conversation was essential. Across a fraction of a light-second, that was easy to arrange, and for three hundred years men had taken it for granted that distance could no longer bar them from each other.

But with the establishment of the first Mars Base, this intimacy had ended. Earth could talk to Mars — but its words would always take at least three minutes to get there, and the reply would take just as long. Conversation was thus impossible, and all business had to be done by Telex or its equivalent.

In theory, this should have been good enough, and usually it was. But there were disastrous exceptions — costly and sometimes fatal interplanetary misunderstandings resulting from the fact that the two men at the opposite ends of the circuit did not really know each other, or comprehend each other's ways of thought, because they had never been in personal contact.

And personal contact was essential at the highest levels of statesmanship and administration. Diplomats had known this for several thousand years, with their apparatus of missions and envoys and official visits. Only after that contact, with its inevitable character evaluation, had been made, and the subtle links of mutual understanding and common interest established, could one do business by long-distance communications with any degree of confidence.

Malcolm Makenzie could never have achieved his own rise on Titan without the friendships made when he had returned to Earth. Once he had thought it strange that a personal tragedy should have led him to power and responsibility beyond all the dreams of his youth; but unlike Ellen, he had buried his dead past and it had ceased to haunt him long ago.

When Colin had repeated the pattern, forty years later, and had returned to Titan with the infant Duncan, the position of the clan had been immensely strengthened. To most of the human race, Saturn's largest moon was now virtually identified with the Makenzies. No one could hope to challenge them if he could not match the network of personal contacts they had established not only on Earth, but everywhere else that mattered. It was through this network, rather than official channels, that the Makenzies, as even their opponents grudgingly admitted, Got Things Done.

And now a fourth generation was being prepared to consolidate the dynasty. Everyone knew that this would happen eventually, but no one expected it so soon.

Not even the Makenzies. And especially not the Helmers.

6

By The Bonny, Bonny Banks of Loch Hellbrew

In the past, Duncan had always cycled to Grandmother Ellen's home, or taken an electric cart whenever he had to deliver some household necessity. This time, however, he walked the two-kilometer tunnel from the city, carrying fifty kilos of carefully distributed mass — which, however, only gave him ten kilos of extra weight. Had he known that such characters had once existed, he might have felt a strong affinity with old-time smugglers, wearing a stylish waistcoat of gold bars.

Colin had presented him with the complex harness of webbing and pouches, with a heartfelt "Thank God I'll never have to use it again! I knew I had it around somewhere, but it took a couple of days to find. It's only too true that the Makenzies never throw anything away."

Duncan found that it needed both hands to lift the harness off the table; when he unzipped one of the many small pouches, he found that it contained a pencil-sized rod of dull metal, astonishingly massive.

"What is it?" he asked. "It feels heavier than gold."

"It is. Tungsten superalloy, if I remember. The total mass is seventy kilos, but don't start wearing it all at once. I began at forty, and added a couple of kilos a day. The important thing is to keep the distribution uniform, and to avoid chafing.

Duncan was doing some mental arithmetic, and finding the results very depressing. Earth gravity was fivetime Titan's — yet this diabolical device would merely double his local weight.

"It's impossible," he said gloomily. "I'll never be able to walk on Earth."

"Well, Idid — thought it wasn't easy at first. Do everything that the doctors tell you, even if it sounds silly. Spend all the time you can in baths, or lying down. Don't be ashamed to use wheelchairs or prosthetic devices, at least for the first couple of weeks. And never try to run."

"Run!"

"Sooner or later you'll forget you're on Earth, and then you'll break a leg. Like to bet on it?"

Betting was one of the useful Makenzie vices. The money stayed in the family, and the loser always learned some valuable lesson. Though Duncan found it impossible to imagine five gravities, it could not be denied that Colin had spent a year on Earth and had survived to tell the tale. So this was not a bet that promised favorable odds.

Now he was beginning to believe Colin's prediction, and he scarcely noticed the extra mass — at least when he was moving in a straight line. It was only when he tried to change direction that he felt himself in the grip of some irresistible force. Not counting visitors from Earth, he was probably now the strongest man on Titan. It was not that his body was developing new strength; rather, it was recovering latent powers which had been slumbering, waiting for the moment when they would be called forth. In a few more years, what he was now attempting would be too late.

The four-meter-wide tunnel had been lasered, years ago, through the rim of the small crater which surrounded Oasis. Originally, it had been a pipeline for the ammoniated petrochemicals of the aptly named Loch Hellbrew, one of the region's chief natural resources. Most of the lake had gone to feed the industries of Titan; later, the tapping of the moon's internal heat, as part of the local planetary engineering project, had caused the remainder to evaporate.

There had been a certain amount of quiet grumbling when Ellen Makenzie had made her intentions clear, but the Department of Resources had pumped the remaining hydrogen-methane fog out of the tunnel, and now it carried oxygen, to the annual annoyance of the auditors, on inventory as part of the city's air reserve. There were two manually operated bulkheads, as well as the city's own backup seals. Anyone went beyond the second bulkhead at his own risk, but that was negligible. The tunnel was through solid rock, and since the pressure inside was higher than ambient, there was no danger of Titanian poisons leaking inward.

Half a dozen side tunnels, all of them now blocked, led out of the main passageway. When he had first come here as a small boy, Duncan had filled those sealed-off shafts with wonder and magic. Now he knew that they merely led to long-abandoned surge chambers. Yet though all the mystery was gone, it still seemed to him that these corridors were haunted by two ghosts. One was a little girl who had been known and loved by only a handful of pioneers; the other was a giant who had been mourned by millions.

There had been endless jokes about Robert Kleinman's name, for he was almost two meters tall, and proportioned accordingly. And his talents had matched his physique; he had been a master pilot at the age of thirty, despite the difficulty of fitting him into standard space equipment. Duncan had never considered him particularly good-looking, but in this matter he was outvoted by a small army of women — including Ellen Makenzie.

Grandma had met Captain Kleinman only a year after the final parting with Malcolm; she may have been on an emotional rebound, but hecertainly was not. Yet thereafter the Captain had never looked at another woman, and it had become one of those love affairs famous on many worlds. It had lasted throughout the planning and preparations for the first expedition to Saturn and the fitting-out of the Challengerin orbit off Titan. And as far as Ellen Makenzie was concerned it had never died; it was frozen forever at the moment when the ship met its mysterious and still inexplicable doom, deep in the jet streams of the South Temperate Zone.

Moving rather more slowly than when he had started his walk, Duncan came to the final bulkhead. On Grandma's hundredth birthday, the younger members of the family had painted it in brilliant fluorescent colors, which had faded not at all in the last dozen years. Since Ellen had never referred to it, and never heard questions which she did not wish to answer, there was no way of discovering if she appreciated the gift.

"I'm here, Grandma," Duncan called into the antique intercom which had been presented to her by some anonymous admirer long ago. (It was still clearly marked "Made in Hong Kong," and had been dated circa1995. Shameful to relate, there had been one attempt to steal it, though since theft was virtually unknown on Titan, this was probably only a childish prank or an anti-Makenzie gesture.

There was, as usual, no reply, but the door unlatched at once and Duncan walked through into the tiny foyer. Grandma's electrocycle occupied the place from which it had not moved for years. Duncan checked the battery and kicked the tires, as he always did with great conscientiousness. No need for any pumping or charging this time; if the old lady suddenly felt the impulse to descend upon the city, there was nothing to prevent her.

The kitchen, which was a unit lifted intact from a small orbital passenger shuttle, was a little tidier than usual. Presumably one of the voluntary helpers had just made her weekly visit. Nevertheless, the usual sickly sour smell of slow culinary disintegration and inadequate recycling was heavy in the air, and Duncan held his breath as he hurried through into the living room. He never accepted more than a cup of coffee from Grandma, and feared accidental poisoning if he ever sampled the products of her robot reconstituter. But Ellen seemed to thrive on it; over the years she must have established some kind of symbiosis with her kitchen. It still lived up to the manufacturer's “fail-safe” guarantee, even though it did produce the most peculiar odors. Doubtless Grandma never noticed them. Duncan wondered what she would do when the final disaster occurred.

The main living room was as crowded as ever. Against one wall were the shelves of carefully labeled rocks — a complete mineralogy of Titan and the other examined moons of Saturn, as well as samples from each of the rings. As long as Duncan could remember, there had been just one section empty, as if, even now, Grandma was still waiting for Kleinman to return.

The opposite wall was more sparsely occupied with communications and information equipment, and racks of micromodules which if completely saturated, could have held more knowledge than all the libraries of Earth up to the twenty-first century. The rest of the room was a compact little workshop, most of the floor space being occupied by the machines that had fascinated Duncan throughout his childhood, and that he would associate with Grandma Ellen as long as he lived.

There were petrological microscopes, polishing and cutting tools, ultrasonic cleaners, laser knives, and all the shining paraphernalia of gemologist and jeweler. Duncan had learned to use most of them, over the years, though he had never acquired more than a fraction of his grandmother's skill and almost wholly lacked her artistic talents. What he did share, to a much greater extent, were her mathematical interests, exemplified by the small computer and associated holographic display.

The computer, like the kitchen, was long overdue of retirement. But it was completely autonomous, so Grandma did not have to rely in any way upon the immensely larger storage facilities in the city. Although her computer had a memory scarcely larger than that of a human brain, it was sufficient for her rather modest purposes. Her interest in minerals had led her, inevitably, to crystallography, then to group theory, and then to the harmless obsession that had dominated so much of her lonely existence. Twenty years ago, in this same room, she had infected Duncan with it. In his case, the disease was no longer virulent, having run its course in a few months; but he knew, with amused tolerance, that he would suffer occasional relapses throughout his life. How incredible that five perfectly identical squares could create a universe that neither man nor computer would ever be able to explore fully...

Nothing in the familiar room had changed since his last visit, three weeks ago. He could even imagine that Grandma had not moved; she was still sitting at her worktable, sorting rocks and crystals, while behind her the read-out screen intermittently flashed solutions of some problem the computer was analyzing. She was, as usual, wearing a long gown that made her look like a Roman matron, though Duncan was quite sure that no Roman matron's dress ever appeared quite so disheveled or, to be perfectly frank, so overdue for the laundry. While Duncan had known her, Ellen's care of her equipment had never extended to her personal appearance.

She did not rise, but tilted her head slightly so that he could deliver his usual affectionate kiss. As he did so, he noticed that the external world, at least, had been touched by change.

The view from Grandma's picture window was famous — but by reputation only, since few indeed had been privileged to see it with their own eyes. Her home was partly countersunk into a ledge overlooking the dried-up bed of Loch Hellbrew and the canyon that led into it, so it presented her with a 180-degree panorama of Titan's most picturesque landscape. Sometimes, when storms raged through the mountains, the view disappeared for hours behind clouds of ammonia crystals. But today the weather was clear and Duncan could see for at least twenty kilometers.

"What's happening over there?" he asked.

At first, he had thought it was one of the fire fountains that sometimes erupted in unstable areas; but in that case the city would have been in danger, and he would have heard of it long ago. Then he realized that the brilliant yet smoky column of light burning steadily on the hill crest three or four kilometers away could only be man-made.

"There's a fusor running over at Huygens. I don't know what they're doing, but that's the oxygen burn-off."

"Oh, one of Armand's projects. Doesn't it annoy you?"

"No — I think it's beautiful. Besides, we need the water. Look at those rain clouds... realrain. And I think there's something growing over there. I've noticed a change in color on the rocks since that flame started burning."

"That's quite possible — the bioengineering people will know all about it. One day you may have a forest to look at, instead of all this bare rock."

He was joking, of course, and she knew it. Except in very restricted areas, no vegetation could grow here in the open. But experiments like this were a beginning, and one day...

Over there in the mountain, a hydrogen fusion plant was at work, melting down the crust of Titan to release all the elements needed for the industries of the little world. And as half that crust consisted of oxygen, now needed only in very small quantities in the closed-cycle economies of the cities, it was simply allowed to burn off.

"Do you realize, Duncan," said Grandma suddenly, "how neatly that flame symbolizes the difference between Titan and Earth?"

"Well, they don’t have to melt rocks there to get everything they need."

"I was thinking of something much more fundamental. If a Terran wants a fire, he ignites a jet of hydrocarbons and lets it burn. We do exactly the opposite. We set fire to a jet of oxygen, and let it burn in our hydromethane atmosphere.

This was such an elementary fact of life — indeed an ecological platitude — that Duncan felt disappointed; he had hoped for some more startling revelation. His face must have reflected his thoughts, for Grandma gave him no chance to comment.

"What I'm trying to tell you," she said, "is that it may not be as easy for you to adjust to Earth as you imagine. You may know — or thinkyou know — what conditions are like there, but that knowledge isn't based on experience. When you need it in a hurry, it won't be there. Your Titan instincts may give the wrong answers. So act slowly, and always think twice before you move."

"I've no choice about acting slowly — my Titan muscles will see to that."

"How long will you be gone?"

"About a year. My official invitation is for two months, but now the trip's being paid for, I'll have funds for a much longer stay. And it seems a pity to waste the opportunity, since it's my only one."

He tried to keep his voice as cheerfully optimistic as he could, though he knew perfectly well the thoughts that must be passing through Grandma's mind. They were both aware that this might be their last meeting. One hundred fourteen was not an excessive age for a woman — but, truly, what did Grandma have to live for? The hope of seeing him again, when he returned from Earth? He liked to think so...

And there was another matter, never to be referred to, yet hovering in the background. Grandma knew perfectly well the main purpose of his visit to Earth, and the knowledge must, even after all these years, be like a dagger in her heart. She had never forgive Malcolm; she had never accepted Colin; would she continue to accept him when he returned with little Malcolm?

Now she was hunting around, with a clumsiness quite unlike her normal precise movements, in one of the cubbyholes of her work desk.

"Here's a souvenir to take with you."

"What — oh, it's beautiful!" He was not being excessively polite; sheer surprise had forced the reaction from him. The flat, crystal-lidded box he was now holding in his hands was, indeed, one of the most exquisite works of geometrical art he had ever seen. And Grandma could not have chosen any single object more evocative of his youth and of the world that, though he was now about to leave it, must always be his home.

As he stared at the mosaic of colored stones that exactly filled the little box, greeting each of the familiar shapes like an old friend, his eyes misted and the years seemed to roll away. Grandma had not changed; but he was only ten...

7

A Cross of Titanite

"You're old enough now, Duncan, to understand this game... though it's very much more than a game."

Whatever it is, thought Duncan, it doesn't look very exciting. What can you do with five identical squares of white plastic, a couple of centimeters on a side?"

"Now the first problem," continued Grandma, "is to see how many differentpatterns you can make, by putting all these squares together."

"While they lie flat on the table?"

"Yes, with the edges matching exactly — overlapping isn't allowed."

Duncan started to shuffle the squares.

"Well," he began, "I can put them all in a straight line like this... then I can switch the end one to make an L... and the one at the other end to make a U..."

He quickly produced half a dozen different assemblies of the five squares, then found that he was repeating himself.

"I think that's all — oh, stupid of me."

He had missed the most obvious figure of all — the cross, or X, formed by putting one square in the middle and the other four surrounding it.

"Most people," said Grandma, "find thatone first. I don’t know what this proves about your mental processes. Do you think you've found them all?"

Duncan continued to slide the squares around, and eventually discovered three more figures. Then he gave up.

"That's the lot," he announced confidently.

"The what about thisone? Said Grandma, moving the squares swiftly to make a figure that looked like a humpbacked F.

"Oh!"

"And this..."

Duncan began to feel very foolish, and was much relieved when Grandma continued: "You did fairly well — you only missed these two. Altogether, there are exactly twelveof these patterns — no more and no less. Here they are. You could hunt forever — you won't find another one."

She brushed aside the five little squares, and laid on the table a dozen brightly colored pieces of plastic. Each was different in shape, and together they formed the complete set of twelve figures that, Duncan was now quite prepared to admit, were all that could be made from five equal squares.

But surely there must be more to it than this. The game couldn't have finished already. No, Grandma still had something up her sleeve.

"Now listen carefully, Duncan. Each of these figures — they're called pentominoes, by the way — is obviously the same size, since they're all made from five identical squares. And there are twelve of them, so the total area is sixty squares. Right?"

"Um... yes."

"Now sixty is a nice round number, which you can split up in lots of ways. Let's start with ten multiplied by six, the easiest one. That's the area of this little box — ten units by six units. So the twelve pieces should fit exactly into it, like a simple jigsaw puzzle."

Duncan looked for traps — Grandma had a fondness for verbal and mathematical paradoxes, not all of them comprehensible to a ten-year-old victim — but he could find none. If the box was indeed the size Grandma said, then the twelve pieces should just fit into it. After all, both were sixty units in area.

Wait a minute... the area might be the same, but the shapecould be wrong. There might be no way of making the twelve pieces fit this rectangular box, even though it was the right size.

"I'll leave it to you," said Grandma, after he had shuffled pieces around for a few minutes. "But I promise you this — it canbe done."

Ten minutes later, Duncan was beginning to doubt it. It was easy enough to fit ten of the pieces into the frame — and once he had managed eleven. Unfortunately, the hole then left in the jigsaw was not the same shape as the piece that remained in his hand — even though, of course, it was of exactly the same area. The hole was an X, the piece was a Z...

Thirty minutes later, he was fairly bursting with frustration. Grandma had left him completely alone, while she conducted an earnest dialogue with her computer; but from time to time she gave him an amused glance, as if to say "See — it isn't as easy as you thought..."

Duncan was stubborn for his age. Most boys of ten would have given up long ago. (It never occurred to him, until years later, that Grandma was also doing a neat job of psychological testing.) He did not appeal for help for almost forty minutes...

Grandma's fingers flickered over the mosaic. The U and the X and L slid around inside their restraining frame — and suddenly the little box was exactly full. The twelve pieces had been perfectly fitted into the jigsaw.

"Well, you knew the answer!" said Duncan, rather lamely.

" Theanswer?" retorted Grandma. "Would you care to guess how many differentways these pieces can be fitted into their box?"

There was a catch here — Duncan was sure of it. He hadn't found a single solution in almost an hour of effort —and he must have tried at least a hundred arrangements. But it was possible that there might be — oh —a dozen different answers.

"I'd guess there might be twenty ways of putting those pieces into the box," he replied, determined to be on the safe side.

"Try again."

That was the danger signal. Obviously, there was much more to this business than met the eye, and it would be safer not to commit himself.

Duncan shook his head.

"I can't imagine."

"Sensible boy. Intuition is a dangerous guide — though sometimes it's the only one we have. Nobodycould ever guess the right answer. There are more than two thousanddistinct ways of putting these twelve pieces back into their box. To be precise, 2,339. What do you think of that?"

It was not likely that Grandma was lying to him, yet Duncan felt so humiliated by his total failure to find even one solution that he blurted out: "I don't believe it!"

Grandma seldom showed annoyance, though she could become cold and withdrawn when he had offended her. This time, however, she merely laughed and punched out some instructions to the computer.

"Look at that," she said.

A pattern of bright lines had appeared on the screen, showing the set of all twelve pentominoes fitted into the six-by-ten frame. It held for a few seconds, then was replaced by another obviously different, though Duncan could not possibly remember the arrangement briefly presented to him. Then came another... and another, until Grandma canceled the program.

"Even at this fast rate," she said, "it takes five hours to run through them all. And take my word for it — though no human being has ever checked each one, or ever could — they're all different."

For al long time, Duncan stared at the collection of twelve deceptively simple figures. As he slowly assimilated what Grandma had told him, he had the first genuine mathematical revelation of his life. What had at first seemed merely a childish game had opened endless vistas and horizons — though even the brightest of ten-year-olds could not begin to guess the full extent of the universe now opening up before him.

This moment of dawning wonder and awe was purely passive; a far more intense explosion of intellectual delight occurred when he found his first very own solution to the problem. For weeks he carried around with him the set of twelve pentominoes in their plastic box, playing with them at every odd moment. He got to know each of the dozen shapes as personal friends, calling them with a good deal of imaginative distortion: the odd group, F, I, L, P, N and the ultimate alphabetical sequence T, U, V, W, X, Y, Z.

And once in a sort of geometrical trance or ecstasy which he was never able to repeat, he discovered five solutions in less than an hour. Newton and Einstein and Chen-tsu could have felt no greater kinship with the gods of mathematics in their own moments of truth...

It did not take him long to realize, without any prompting from Grandma, that it might also be possible to arrange the pieces in other shapes besides the six-by-ten rectangle. In theory, at least, the twelve pentominoes could exactly cover rectangles with sides of five-by-twelve units, four-by-fifteen units, and even the narrow strip only three units wide and twenty long.

Without too much effort, he found several examples of the five-by-twelve and four-by-fifteen rectangles. Then he spent a frustrating week, trying to align the dozen pieces into a perfect three-by-twenty strip. Again and again he produced shorter rectangles, but always there were a few pieces left over, and at last he decided that this shape was impossible.

Defeated, he went back to Grandma — and received another surprise.

"I'm glad you made the effort," she said. "Generalizing — exploring every possibility — is what mathematics is all about. But you're wrong. It canbe done. There are just two solutions; and if you find one, you'll also have the other."

Encouraged, Duncan continued the hunt with renewed vigor. After another week, he began to realize the magnitude of the problem. The number of distinct ways in which a mere twelve objects could be laid out essentially in a straight line, when one also allowed for the fact that most of them could assume at least four different orientations, was staggering.

Once again, he appealed to Grandma, pointing out the unfairness of the odds. If there were only two solutions, how long would it take to find them?

"I'll tell you," she said. "If you were a brainless computer, and put down the pieces at the rate of one a second in every possible way, you could run through the whole set in" — she paused for effect — "rather more than six millionyears."

Earth years or Titan years? thought the appalled Duncan. Not that it really mattered...

"But you aren't a brainless computer," continued Grandma. "You can see at a glance whole categories that won't fit into the pattern, so you don't have to bother about them. Try again..."

Duncan obeyed, though without much enthusiasm or success. And then he had a brilliant idea.

Karl was interested, and accepted the challenge at once. He took the set of pentominoes, and that was the last Duncan heard of him for several hours.

The he called back, looking a little flustered.

"Are you sure it can be done?" he demanded.

"Absolutely. In fact, there are two solutions. Haven't you found even one? I thought you were good at mathematics."

"So I am. That'swhy I know how tough the job is. There are over a quadrillion possible arrangements to be checked."

"How do you work that out?" asked Duncan, delighted to discover something that had baffled his friend.

Karl looked at a piece of paper covered with sketches and numbers.

"Well, excluding forbidden positions, and allowing for symmetry and rotation, it comes to factorial twelve times two to the twenty-first — youwouldn't understand why! That's quite a number; here it is."

He held up a sheet on which he had written, in large figures, the imposing array of digits:

1 004 539 160 000 000

Duncan looked at the number with satisfaction; he did not doubt Karl's arithmetic.

"So you've given up."

" NO!I'm just telling you how hard it is." And Karl, looking grimly determined, switched off.

The next day, Duncan had one of the biggest surprises of his young life. A bleary-eyed Karl, who had obviously not slept since their last conversation, appeared on his screen.

"Here it is," he said, exhaustion and triumph competing in his voice.

Duncan could hardly believe his eyes; he had been convinced that the odds against success were impossibly great. But there was the narrow rectangular strip, only three squares wide and twenty long, formed from the complete set of twelve pieces...

With fingers that trembled slightly from fatigue, Karl took the two end sections and switched them around, leaving the center portion of the puzzle unchanged.

"And here's the second solution," he said. "Now I'm going to bed. Good night — or good morning, if that's what it is."

For a long time, a very chastened Duncan sat staring at the blank screen. He did not as yet understand what had happened. He only knew that Karl had won against all reasonable expectations.

It was not that Duncan really minded; he loved Karl too much to resent his little victory, and indeed was capable of rejoicing in his friend's triumphs even when they were at his own expense. But there was something strange here, something almost magical.

It was Duncan's first glimmer of the power of intuition, and the mind's mysterious ability to go beyond the available facts and to short-circuit the process of logic. In a few hours, Karl had completed a search that should have required trillions of operations, and would have tied up the fastest computer in existence for an appreciable number of seconds.

One day, Duncan would realize that all men had such powers, but might use them only once in a lifetime. In Karl, the gift was exceptionally well developed; form that moment onward, Duncan had learned to take seriously even his most outrageous speculations.

That was twenty years ago; whatever had happened to that little set of plastic figures? He could not remember when he had last seen it.

But here it was again, reincarnated in colored minerals — the peculiar rose-tinted granite from the Galileo Hills, the obsidian of the Huygens Plateau, the pseudomarble of the Herschel Escarpment. And there — it was unbelievable, but doubt was impossible in such a matter — was the rarest and most mysterious of all the gemstones found on this world. The X of the puzzle was made of Titanite itself; no one could ever mistake that blue-black sheen with its fugitive flecks of gold. It was the largest piece that Duncan had ever seen, and he could not even guess at its value.

"I don't know what to say," he stammered. "It's beautiful — I've never seen anything like it."

He put his arms around Grandma's thin shoulders — and found, to his distress, that they were quivering uncontrollably. He held her gently until the shaking stopped, knowing there were no words for such moments, and realizing as never before that he was the last love of her empty life, and he was leaving her to her memories.

8

Children of The Corridors

There was a sense of sadness and finality about almost everything that he did in these last days. Sometimes it puzzled Duncan; he should be excited, anticipating the great adventure that only a handful of men on his world could ever share. And though he had never before been out of touch with his friends and family for more than a few hours, he was certain that a year's absence would pass swiftly enough among the wonders and distractions of Earth.

So why this melancholy? If he was saying farewell to the things of his youth, it was only for a little while, and he would appreciate them all the more when he returned...

When he returned. That, of course, was the heart of the problem. In a real sense, the Duncan Makenzie who was now leaving Titan would never return; indeed, that was the purpose of the exercise. Like Colin thirty years ago, and Malcolm forty years before that, he was heading sunward in search of knowledge, of power, of maturity — and, above all, of the successor which his own world could never give him. for, of course, being Malcolm's duplicate, he too carried in his loins the fatal Makenzie gene.

Sooner than he had expected, he had to prepare his family for the new addition. After the usual number of experiments, he had settled down with Marissa four years ago, and he loved her children as much, he was certain, as if they had been his own flesh and blood. Clyde was now six years old, Carline three. They in their turn appeared to be as fond of Duncan as of their real fathers, who were now regarded as honorary members of Clan Makenzie. Much the same thing had happened in Colin's generation — he had acquired or adopted three families — and in Malcolm's. Grandfather had never gone to the trouble of marrying again after Ellen had left him, but he had never lacked company for long. Only a computer could keep track of the comings and goings on the periphery of the clam; it often seemed that most of Titan was related to it in some way or other. One of Duncan's major problems now was deciding who would be mortally offended if he failed to say good-bye.

Quite apart from the time factor, he had other reasons for making as few farewells as possible. Every one of his friends and relatives — as well as almost complete strangers — seemed to have some request for him, some mission they wanted him to carry out as soon as he reached Earth. Or, worse still, there was some essential item ("It won't be any trouble") they wanted him to bring back. Duncan calculated that he would have to charter a special freighter if he acquiesced to all these demands.

Every job now had to be divided into one of two categories. There were the things that mustbe done before he left Titan, and those that could be postponed until he was aboard ship. The latter included his studies of current terrestrial affairs, which kept slipping despite Colin's increasingly frantic attempts to update him.

Extricating himself from his official duties was also no easy task, and Duncan realized that in a few more years it would be well-nigh impossible. He was getting involved in too many things, though that was a matter of deliberate family policy. More than once he had complained that his title of Special Assistant to the Chief Administrator gave him responsibility without power. To this, Chief Administrator Colin had retorted: "Do you know what power means in our society? Giving orders to people who carry them out — only ifand when they feel like it."

This was, of course, a gross libel on the Titanian bureaucracy, which functioned surprisingly well and with a minimum of red tape. Because all the key individuals knew each other, an immense amount of business got done through direct personal contact. Everyone who had come to Titan had been carefully selected for intelligence and ability, and knew that survival depended upon co-operation. Those who felt like abandoning their social responsibilities first had to practice breathing methane at a hundred below.

One possible embarrassment he had at least been spared. He could hardly leave Titan without saying good-bye to his once closest friend — but, very fortunately, Karl was off-world. Several months ago he had left on one of the shuttles to join a Terran survey ship working its way through the outer moons. Ironically enough, Duncan had envied Karl his chance of seeing some unknown worlds; now it was Karl who would be envious when he heard that Duncan was on his way to Earth. The thought gave him more sadness than pleasure; the Makenzies, whatever their faults, were not vindictive. Yet Duncan could not help wondering how often Karl's reveries would now turn sunward, and to the moment long ago when their emotions had been irrevocably linked with the mother world.

Duncan was just sixteen, and Karl twenty-one, when the cruise liner Mentorhad made her first, and it was widely hoped only, rendezvous with Titan. She was a converted fusion-drive freighter — slow but economical, provided adequate supplies of hydrogen could be picked up at strategic points.

Mentorhad stopped at Titan for her final refueling, on the last leg of a grand tour that had taken her to Mars, Ganymede, Europa, Pallas, and Iapetus, and had included fly-bys of Mercury and Eros. As soon as she had loaded some fifteen thousand tons of hydrogen, her exhausted crew planned to head back to Earth on the fastest orbit they could compute, if possible after marooning all the passengers.

The cruise must have seemed a good idea when a consortium of Terran universities had planned it several years earlier. And so indeed it had turned out, in the long run, for Mentorgraduates had since proved their worth throughout the Solar System. But when the ship staggered into her parking orbit, under the command of a prematurely gray captain, the whole enterprise looked like a first-magnitude disaster.

The problems of keeping five hundred young adults entertained and out of mischief on a six-months' cruise aboard even the largest spaceliner had not been given sufficient thought; the law professor who had signed on as master-at-arms was later heard to complain bitterly about the complete absence from the ship's inventory of hypodermic guns and knockout gas. On the other hand, there had been no deaths or serious injuries, only one pregnancy, and everyone had learned a great deal, though not necessarily in the areas that the organizers had intended. The first few weeks, for example, were mostly occupied by experiments in zero-gravity sex, despite warnings that this was an expensive addiction for those compelled to spend most of their lives on planetary surfaces.

Other shipboard activities, it was widely believed, were not quite so harmless. There were reports of tobacco-smoking — not actually illegal, of course, but hardly sensible behavior when there were so many safe alternatives. Even more alarming were persistent rumors that someone had smuggled an Emotion Amplifier on board Mentor. The so-called joy machines were banned on all planets, except under strict medical control; but there would always be people to whom reality was not good enough, and who would want to try something better.

Notwithstanding the horror stories radioed ahead from other ports of call, Titan had looked forward to welcoming its young visitors. It was felt that they would add color to the social scene, and help establish some enjoyable contacts with Mother Earth. And anyway, it would be for only a week...

Luckily, no one dreamed that it would be for two months. This was not Mentor's fault; Titan had only itself to blame.

When Mentorfell into its parking orbit, Earth and Titan were involved in one of their periodical wrangles over the price of hydrogen, F.O.B. Zero Gravitational Potential (Solar Reference). The proposed 15 percent rise, screamed the Terrans, would cause the collapse of interplanetary commerce. Anything under 10 percent, swore the Titanians, would result in their instant bankruptcy and would make it impossible for them to import any of the expensive items Earth was always trying to sell. To any historian of economics, the whole debate was boringly familiar.

Unable to get a firm quotation, Mentorwas stranded in orbit with empty fuel tanks. At first, her captain was not too unhappy; he and the crew could do with the rest, now that the passengers had shuttled down to Titan and had fanned out all over the face of the hapless satellite. But one week stretched into two, then three, then a month. By that time, Titan was ready to settle on almost any terms; unfortunately, Mentorhad now missed her optimum trajectories, and it would be another four weeks before the next launch window opened. Meanwhile, the five hundred guests were enjoying themselves, usually much more than their hosts.

But to the younger Titanians, it was an exciting time which they would remember all their lives. On a small world where everyone knew everybody else, half a thousand fascinating strangers had arrived, full of tales, many of them quite true, about the wonders of Earth. Here were men and women, barely into their twenties, who had seen forests and prairies and oceans of liquid water, who had strolled unprotected under an open sky beneath a sun whose heat could actually be felt...

This very contrast in backgrounds, however, was a possible source of danger. The Terrans could not be allowed to go wandering around by themselves, even inside the habitats. They had to have escorts, preferable responsible people not too far from their own age group, to see that they did not inadvertently kill either themselves or their hosts.

Naturally, there were times when they resented this well-intentioned supervision, and even tried to escape from it. One group succeeded; it was very lucky, and suffered no more than a few searing whiffs of ammonia. Damage was so slight that the foolish adventurers required only routine lung transplants, but after this exploit there was no more serious trouble.

There were plenty of other problems. The sheer mechanics of absorbing five hundred visitors was a challenge to a society where living standards were still somewhat Spartan, and accommodation limited. At first, all the unexpected guests were housed in the complex of corridors left by an abandoned mining operation, hastily converted into dormitories. Then, as quickly as arrangements could be made, they were farmed out — like refugees from some bombed city in an ancient war — to any households that were able to cope with them. At this stage, there were still many willing volunteers, among them Colin and Sheela Makenzie.

The apartment was lonely, now that Duncan's pseudosibling Glynn had left home to work on the other side of Titan; Sheela's other child, Yuri, had been gone for a decade. Though Number 402, Second Level, Meridian Park was hardly spacious by Terran standards, Assistant Administrator Colin Makenzie, as he was then, had selected one of the homeless waifs for temporary adoption.

And so Calindy had come into Duncan's life — and into Karl's.

9

The Fatal Gift

Catherine Linden Ellerman had celebrated her twenty-first birthday just before Mentorreached Saturn. By all accounts, it had been a memorable party, giving the final silvery gloss to the captain's remaining hairs. Calindy would have sailed through untouched; next to her beauty, that was her most outstanding characteristic. In the midst of chaos — even chaos that she herself had generated — she was the calm center of the storm. With a self-possession far beyond her years, she seemed to young Duncan the very embodiment of Terran culture and sophistication. He could smile wryly, one and a half decades later, at his boyish naпvetй; but it was not wholly unfounded. By any standards, Calindy was a remarkable phenomenon.

Duncan knew, of course, that all Terrans were rich. (How could it be otherwise, when each was the heir to a hundred thousand generations?) But he was overawed by Calindy's display of jewels and silks, never realizing that she had a limited wardrobe which she varied with consummate skill. Most impressive of all was a stunningly beautiful coat of golden fur — the only one ever seen on Titan — made from the skins of an animal called a mink. That was typical of Calindy; no one else would have dreamed of taking a fur coat aboard a spaceship. And she had not done so — as malicious rumor pretended — because she had heard it was cold out around Saturn. She was much too intelligent for that kind of stupidity, and I knew exactly what she was doing; she had brought her mink simply because it was beautiful.

Perhaps because he could see her only through a mist of adoration, Duncan could never visualize her, in later years, as an actual person. When he thought of Calindy, and tried to conjure up her image, he did not see the real girl, but always his only replica of her, in one of the bubble stereos that had become so popular in the ‘50’s.

How many thousands of times he had taken that apparently solid, yet almost weightless sphere in his hands, shaken it gently, and thus activated the five-second loop! Through the subtle magic of organized gas molecules, each releasing its programmed quantum of light, Calindy's face would appear out of the swirling mists — tiny, yet perfect in form and color. At first she would be in profile; then she would turn and suddenly — Duncan could never be sure of the moment when it arrived — there would be the faint smile that only Leonardo could have captured in an earlier age. She did not seem to be smiling at him, but at someone over his shoulder. The impression was so strong that more than once Duncan had looked back, startled, to see who was standing behind him.

Then the image would fade, the bubble would become opaque, and he would have to wait five minutes before the system recharged itself. It did not matter; he had only to close his eyes and he could still see the perfect oval face, the delicate ivory skin, the lustrous black hair gathered up into a toque and held in place by a silver comb that had belonged to a Spanish princess, when Columbus was a child. Calindy liked playing roles, though she took none of them too seriously, and Carmen was one of her favorites.

When she entered the Makenzie household, however, she was the exiled aristocrat, graciously accepting the hospitality of kindly provincials, with what few family heirlooms she had been able to save from the Revolution. As this impressed no one except Duncan, she quickly became the studious anthropologist, taking notes for her thesis on the quaint habits of primitive societies. This role was at least partly genuine, for Calindy was really interested in differing life styles; and by some definitions, Titan could indeed by classed as primitive — or, at least, undeveloped.

Thus the supposedly unshockable Terrans were genuinely horrified at encountering families with three — and even four! — children on Titan. The twentieth century's millions of skeleton babies still haunted the conscience of the world, and such tragic but understandable excesses as the "Breeder Lynching" campaign, not to mention the burning of the Vatican, had left permanent scars on the human psyche. Duncan could still remember Calindy's expression when she encountered her first family of six: outrage contended with curiosity, until both were moderated by Terran good manners. He had patiently explained the facts of life to her, pointing out that there was nothing eternally sacred about the dogma of Zero Growth, and that Titan reallyneeded to double its population every fifty years. Eventually she appreciated this logically, but she had never been able to accept it emotionally. And it was emotion that provided the driving force of Calindy's life; her will and beauty and intelligence were merely its servants.

For a young Terran, she was not promiscuous. She once told Duncan — and he believed her — that she never had more than two lovers at a time. On Titan, to Duncan's considerable distress, she had only one.

Even if the Helmers and Makenzies had not been related through Grandma Ellen, it was inevitable that she would have met Karl, at one of the countless concerts and parties and dances arranged for Mentor'scastaways. So Duncan could not really blame himself for introducing them; it would have made not difference in the end. Yet even so, he would always wonder...

Karl was then almost twenty-two — a year older than Calindy, though far less experienced. He still possessed the slightly overmuscled build of the native-born Terran, but had adapted so well to the lower gravity that he moved more gracefully than most men who had spent their entire lives on Titan. He seemed to possess the secret of power without clumsiness.

And in a quite literal sense, he was the Golden Boy of his generation. Though he pretended to hate the phrase, Duncan knew that he was secretly proud of the title someone had given him in his teens: “The boy with hair like the sun.” The description could only have been coined by a visitor from Earth. No Titanian would have thought of it — but everyone agreed that it was completely appropriate. For Karl Helmer was one of those men upon whom, for their own amusement, the Gods had bestowed the fatal gift of beauty.

* * * * *

Only years later, and partly thanks to Colin, did Duncan begin to understand all the nuances of the affair. Soon after his twenty-third birthday, the Makenzies received the last Star Day card that Calindy ever sent them.

"I stilldon't know if I made a mistake," Colin said ruefully as he fingered the bright rectangle of paper that had carried its conventional greetings halfway across the Solar System. "But it seemed a good idea at the time."

"Well, I don't think it did any harm, in the long run."

Colin looked at him strangely.

"I wonder. Anyway, it certainly didn't turn out as I expected."

"And what didyou expect?"

It was sometimes a great advantage, and sometimes downright embarrassing, to have a father who was also your thirty-year-older identical twin. He knew all the mistakes you were going to make, because he had made them already. It was impossible to conceal any secrets from him, because his thought processes were virtually the same. In such a situation, the only policy that made any sense was complete honesty, as far as that could be achieved by human beings.

"I'm not quite sure. But the moment I saw Calindy, shining like a nova amid all that gloom and chaos down in the old mine workings, I wanted to learn more about her... wanted to make her part of my life. Youknow what I mean."

Duncan could only nod his head in silent agreement.

"Sheela didn't mind — after all, I'm not a baby-snatcher! And we both hoped that Calindy would give you someone to think about besides Karl."

"I was already getting over that, anyway. It was much too frustrating."

Colin chuckled, not unsympathetically.

"So I can imagine. Karl was spreading himself pretty thin. Half of Titan was in love with him in those days — still is, for that matter. Which is why we must keep him out of politics. Remind me to tell you about Alcibiades someday.

"Who?"

"Ancient Greek general — too clever and charming for his own good. Or for anyone else's."

"I appreciate your concern," said Duncan, with only a slight trace of sarcasm. "But that increased my problems a hundred percent. As she made quite clear, I was much too young for Calindy, and of course Karl was now interested only in her. And to make matters worse, they didn't even mind me sharing their bed — as long as I didn't get in the way. In fact—"

"Yes?"

Duncan's face darkened. How strange that he had never thought of this before, yet how obvious it was!"

"Didn't mind, hell! They enjoyedhaving me there, just to tease me! At least Karl did."

It should have been a shattering revelation, yet somehow it did not hurt as much as he would have expected. He must have realized for a long time, without admitting it to himself, that there was a very definite streak of cruelty in Karl. Certainly his lovemaking often lacked tenderness and consideration; there were even times when he had scared Duncan into something approaching impotence. And to do that to a virile sixteen-year-old was no mean feat.

"I'm glad you've realized that," said Colin somberly. "You had to find it out for yourself — you wouldn't have believed us. But whatever Karl did, he certainly paid for it. That breakdown was serious. And, frankly, I don't believe his recovery is as complete as the doctors claim."

This was also a new thought to Duncan, and he turned it over in his mind. Karl's breakdown was still a considerable mystery, which the Helmer family had never discussed with outsiders. The romantics had a simple explanation: he was heartbroken over the loss of Calindy. Duncan had always found this too hard to accept. Karl was too tough to pine away like some character in an old-time melodrama — especially when there were at least a thousand volunteers waiting to console him. Yet it was undeniable that the breakdown had occurred only a few weeks after Mentorhad, to everyone's relief, blasted Earthward.

After that, there had been a complete change in his personality; whenever Duncan met him in these last few years, he had seemed almost a stranger.

Physically, he was as beautiful as ever — perhaps even more so, thanks to his greater maturity. And he could still be friendly, though there were sudden silences when he seemed to retreat into himself for no apparent reason. But real communication was missing; maybe it had never been there...

No, that was unfair and untrue. They had known many shared moments before Calindy entered their lives. And one, though only one, after she had left.

That was still the deepest pain that Duncan had ever known. He had been inarticulate with grief when they had made their farewells in the shuttle terminus at Meridian, surrounded by scores of other parting guests. To its great surprise, Titan had suddenly discovered that it was going to miss its young visitors; nearly every one of them was surrounded by a tearful group of local residents.

Duncan's grief was also, to no small extent, complicated with jealousy. He never discovered how Karl — or Calindy — had managed it, but they flew up in the shuttle together, and made their final farewells on the ship. So when Duncan glimpsed Calindy for the last time, when she waved back at him from the quarantine barrier, Karl was still with her. In that desolating moment, he did not suppose that he would ever see her again.

When Karl returned on the last shuttle flight, five hours later, he was drawn and pale, and had lost all his usual vivacity. Without a word, he had handed Duncan a small package, wrapped in brightly colored paper, and bearing the inscription of LOVE FROM CALINDY.

Duncan had opened it with trembling fingers; a bubble stereo was inside. It was a long time before he was able to see, through the mist of tears, the image it contained.

Much later that same day, as they clung together in mutual misery, an obvious question had suddenly occurred to Duncan.

"What did she give you, Karl?" he had asked.

There was a sudden pause in the other's breathing, and he felt Karl's body tense slightly and draw away from him. It was an almost imperceptible gesture; probably Karl was not even aware of it.

When he answered, his voice was strained and curiously defensive.

"It's — it's a secret. Nothing important; perhaps one day I'll tell you."

Even then, Duncan knew that he never would; and somehow he already realized that this was the last night they would ever spend together.

10

World's End

Ground Effect Vehicles were very attractive in a low-gravity, dense-atmosphere environment, but they did tend to rearrange the landscape, especially when it consisted of fluffy snow. That was only a problem, however, to anyone following in the rear. When it reached its normal cruising speed of two hundred kilometers an hour, the hoversled left its private blizzard behind it, and the view ahead was excellent.

But it was not cruising at two hundred klicks; it was flat out at three, and Duncan was beginning to wish he had stayed home. It would be very stupid if he broke his neck, on a mission where his presence was quite unnecessary, only two days before he was due to leave for Earth.

Yet there was not real danger. They were moving over smooth, flat ammonia snow, on a terrain known to be free from crevasses. Top speed was safe, and it was fully justified. This was too good an opportunity to miss, and he had waited for it for years. No one had ever observed a waxworm in the active phase, and this one was only eighty kilometers from Oasis. The seismographs had spotted its characteristic signature, and the environment computer had given the alert. The hoversled had been through the airlock within ten minutes.

Now it was approaching the lower slopes of Mount Shackelton, the well-behaved little volcano which, after much careful thought, the original settlers had decided to accept as a neighbor. Waxworms were almost always associated with volcanoes, and some were festooned with them — "like an explosion in a spaghetti factory," as one early explorer had put it. No wonder that their discovery had caused much excitement; from the air they looked very much like the protective tunnels build by termites and other social insects on Earth.

To the bitter disappointment of the exobiologists, they had turned out to be a purely natural phenomenon — the equivalent, at a much lower temperature, of terrestrial lava tubes. The head of a waxworm moved, judging from the seismic records, at up to fifty kilometers an hour, preferring slopes of not more than ten degrees. They had even been known to go uphillfor short distances, when the driving pressure was sufficiently high. Once the core of hot petrochemicals had passed along, what remained was a hollow tube as much as five meters in diameter. Waxworms were among Titan's more benign manifestations; not only were they a valuable source of raw materials, but they could be readily adapted for storage space and even temporary surface housing — if one could get used to the rich orchestration of aliphatic smells.

The hoversled had another reason for speed; it was the season of eclipses. Twice ever Saturnian year, around the equinoxes, the sun would vanish behind the invisible bulk of the planet for up to six hours at a time. There would be no slow waning of light, as on Earth; with shocking abruptness, the monstrous shadow of Saturn would sweep across Titan, bringing sudden and unexpected night to any traveler who had been foolish enough not to check his calendar.

Today's eclipse was due in just over an hour, which, unless they ran into obstacles, would give ample time to reach the waxworm. The sled was now driving down a narrow valley flanked by beautiful ammonia cliffs, tinted every possible shade of blue from the palest sapphire to deep indigo. Titan had been called the most colorful world in the Solar System — not excluding Earth; if the sunlight had been more powerful, it would have been positively garish. Although reds and oranges predominated, every part of the spectrum was available somewhere, though seldom for long in the same place. The methane storms and ammonia rains were continually sculpting the landscape.

"Hello, Sled Three," said Oasis Control suddenly. "You'll be out in the open again in five kilometers — less than two minutes at your present speed. Then there's a ten-kilometer slope up to the Amundsen Glacier. From there, you should be able to see the worm. But I think you're too late — it's almost reached World's End."

"Damn," said the geologist who had been handling the sled with such effortless skill. "I was afraid of that. Something tells me I'm nevergoing to catch a worm on the run."

He cut the speed abruptly as a flurry of snow reduced visibility almost to zero, and for a few minutes they were navigating on radar alone through a shining white mist. A film of sticky hydrocarbon slush started to build up on the forward windows, and would soon have covered them completely if the driver had not taken remedial action. A high-pitched whine filled the cabin as the sheets of tough plastic started to oscillate at near ultrasonic frequencies, and a fascinating pattern of standing waves appeared before the obscuring layer was flicked away.

Then they were through the little storm, and the jet-black wall of the Amundsen Glacier was visible on the horizon. In a few centuries that creeping mountain would reach Oasis, and it would be necessary to do something about it. During the years of summer, the viscosity of the carbon-impregnated oils and waxes became low enough for the glacier to advance at the breath-taking speed of several centimeters an hour, but during the long winter it was as motionless as rock.

Ages ago, local heating had melted part of the glacier and formed Lake Tuonela, almost as Stygian black as its parent but decorated by great whorls and loops where lighter material had been caught in patterns of turbulence, now frozen for eternity. Everyone who saw the phenomenon from the air for the first time though he was being original when he exclaimed: "Why, it looks exactly like a cup of coffee, just after you've stirred in the cream!"

As the sled raced over the lake, the pattern flickered past in a few minutes, too close for its swirls to be properly observed. Then there was another long slope, dotted with large boulders which could be avoided only by the full thrust of the underjets. This cut speed to less than a hundred klicks, and the sled labored up toward the crest in zigs and zags, the driver cursing and looking every few seconds at his watch.

"There it is!" Duncan shouted.

Only a few kilometers away, coming out of the mist that always enveloped the flanks of Mount Shackelton, was a thin white line, like a piece of rope laid across the landscape. It stretched away downhill until it disappeared over the horizon, and the driver swung the sled around to follow its track. But Duncan already knew that they were too late to achieve their main objective; they were much too close to World's End. Minutes later, they were there, and the sled came to a stop at a respectful distance.

"That's as close as I'm getting," said the driver. "I wouldn't like a gust to catch us when we're skirting the edge. Who wants to go out? We still have thirty minutes of light."

"What's the temperature?" someone asked.

"Warm. Only fifty below. Single-layer suits will do."

It was the first time Duncan had been out in the open for months, but there were some skills that nobody who lived on Titan ever allowed himself to forget. He checked the reserve oxygen pressure, the reserve tank, the radio, the fit of the neck seal — all those little details upon which his hopes of a peaceful old age depended. The fact that he would be within a hundred meters of safety, and surrounded by other men who could come to his aid in a moment, did not affect his thoroughness in the least.

Realspacers sometimes underestimated Titan, with disastrous results. It seemed altogether too easy to move around on a world where a pressure suit was unnecessary and the whole body could be exposed to the surrounding atmosphere. Nor was there any need to worry about freezing, even in the Titanian night. As long as the thermosuit retained its integrity, the body's own hundred and fifty watts of heat could maintain a comfortable temperature indefinitely.

These facts could induce a sense of false security. A torn suit — which would be immediately noticed and repaired in a vacuum environment — might be ignored here as a minor discomfort until it was too late, and toes and fingers were quietly dropping off through frostbite. And although it seemed incredible that anyone could ignore an oxygen warning, or be careless enough to go beyond his point of no return, it hadhappened. Ammonia poisoning is not the nicest way to die.

Duncan did not let these facts oppress him, but they were always there at the back of his mind. As he walked toward the worm, his feet crunching through a thin crust like congealed candle grease, he kept automatically checking the positions of his nearest companions, in case they needed him — or he needed them.

The cylindrical wall of the worm now loomed above him, ghostly white, textured with little scales or platelets which were slowly peeling off and falling to the ground. Duncan removed a mitten and laid his bare hand on the tube. It was slightly warm and there was a gentle vibration; the core of hot liquid was still pulsing within, like blood through a giant artery. But the worm itself, controlled by the interacting forces of surface tension and gravity, had committed suicide.

While the others busied themselves with their measurements, photographs, and samples, Duncan walked to World's End. It was not his first visit to that famous and spectacular view, but the impact had not diminished.

Almost at his feet, the ground fell away vertically for more than a thousand meters. Down the face of the cliff, the decapitated worm was slowly dripping stalactites of wax. From time to time an oily globule would break off and fall slowly toward the cloud layer far below. Duncan knew that the ground itself was another kilometer beneath that, but the sea of clouds that stretched out to the horizon had never broken since man had first observed it.

Yet overhead, the weather was remarkably clear. Apart from a little ethylene cirrus, nothing obscured the sky, and the sun was as sharp and bright as Duncan had ever seen it. He could even make out, thirty kilometers to the north, the unmistakable cone of Mount Shackelton, with its perpetual streamer of smoke.

"Hurry up and take your pictures," said a voice in his radio. "You have less than five minutes."

A million kilometers away, the invisible bulk of Saturn was edging toward the brilliant star that flooded this strange landscape with a light ten thousand times brighter than Earth's full Moon. Duncan stepped back a few paces from the brink, but not so far that he could no longer watch the clouds below; he hoped he would be able to observe the shadow of the eclipse as it came racing toward him.

The light was going — going — gone. He never saw the onrushing shadow; it seemed that night fell instantly upon all the world.

He looked up toward the vanished sun, hoping to catch a glimpse of the fabled corona. But there was only a shrinking glow, revealing for a few seconds the curved edge of Saturn as the giant world swept inexorably across the sky. Beyond that was a faint and distant star, which in another moment would also be engulfed.

"Eclipse will last twelve minutes," said the hoversled driver. "If any of you want to stay outside, keep away from the edge. You can easily get disoriented in the darkness."

Duncan scarcely heard him. Something had caught at his throat, almost as if a whiff of the surrounding ammonia had invaded his suit.

He could not take his gaze off that faint little star, during the seconds before Saturn wiped it from the sky. He continued to stare long after it was gone, with all its promise of warmth and wonder, and the storied centuries of its civilization.

For the first time in his life, Duncan Makenzie had seen the planet Earth with his own unaided eyes.

Part Two

Transit

11

Sirius

After three hundred years of spaceships that were mostly fuel tanks, Siriuswas not quite believable. She seemed to have far too many windows, and there were entrance hatches in most improbable places, some of them still gaping open as cargo was loaded. At least she was taking on somehydrogen, thought Duncan sourly; it would be adding insult to economic injury if she made the round trip on a single fueling. She was capable of doing this, it was rumored, though at the cost of doubling her transit time.

It was also hard to believe that this stubby cylinder, with the smooth mirror-bright ring of the radiation baffle surrounding the drive unit like a huge sunshade, was one of the fastest objects ever built by man. Only the interstellar probes, now far out into the abyss of their centuries-long journeys, could exceed her theoretical maximum — almost one percent of the velocity of light. She would never achieve even half this speed, because she had to carry enough propellant to slow down and rendezvous with her destination. Nevertheless, she could make the voyage from Saturn to Earth in twenty days, despite a minor detour to avoid the hazards — largely psychological — of the asteroid belt.

The forty-minute flight from surface to parking orbit was not Duncan's first experience of space; he had made several brief trips to neighboring moons, aboard this same shuttle. The Titanian passenger fleet consisted of exactly five vessels, and as none possessed the expensive luxury of centrifugal gravity, all safety belts were secured throughout the voyage. Any passenger who wished to sample the joys and hazards of weightlessness would have just under two hours to experience it aboard Sirius, before the drive started to operate. Although Duncan had always felt completely at ease in free fall, he let the stewards float him, an inert and unresisting package, through the airlock and into the ship.

It had been rather too much to expect the Centennial Committee to provide a single cabin — there were only four on the ship — and Duncan knew that he would have to share a double. L.3 was a minute cell with two folding bunks, a couple of lockers, two seats — also folding — and a mirror-vision screen. There was no window looking out into space; this, the Welcome Aboard!brochure carefully explained, would create unacceptable structural hazards. Duncan did not believe this for a moment, and wondered if the designers feared an attempt by claustrophobic passengers to claw a way out.

And there were no toilet facilities — these were all in an adjacent cubicle, which serviced the four cabins around it. Well, it was only going to be for a few weeks...

Duncan's spirits rose somewhat after he had gained enough confidence to start exploring his little world. He quickly learned to visualize his location by following the advice printed on the shipboard maps; it was convenient to think of Siriusas a cylindrical tower with ten floors. The fifty cabins were divided between the sixth and seventh floors. Immediately below, on the fifth level, was the lounge, recreation and dining area.

The territory above these floors was forbidden to passengers. Going upward, the remaining levels were Life Support, Crew Quarters, and — forming a kind of penthouse with all-round visibility — the Bridge. In the other direction, the four levels were Galley, Hold, Fuel, and Propulsion. It was a logical arrangement, but it would take Duncan some time to discover that the Purser's Office was on the kitchen level, the surgery next to the freight compartment, the gym in Life Support, and the library tucked away in an emergency airlock overlapping levels Six and Seven...

During the circumnavigation of his new home, Duncan encountered a dozen other passengers on a similar voyage of exploration, and exchanged the guarded greetings appropriate among strangers who will soon get to know each other perhaps all too well. He had already been through the passenger list to see if there was anyone on board he knew and had found a few familiar Titanian names, but no close acquaintances. Sharing cabin L.3, he had discovered, was a Dr. Louise Chung; but the parting with Marissa still hurt too much for the ‘Louise’ to arouse more than the faintest flicker of interest.

In any event, as he found when he returned to L.3, Dr. Chung was a bright little old lady, undoubtedly on the far side of a hundred, who greeted him with an absent-minded courtesy which, even by the end of the voyage, never seemed to extend to a complete recognition of his existence. She was, he soon discovered, one of the Solar System's leading mathematical physicists, and theauthority on resonance phenomena among the satellites of the outer planets. For half a century she had been trying to explain why the gaps in Saturn's rings were not exactly where all the bet theories demanded.

The two hours ticked slowly away, finally seeming to move with a rush toward the expected announcement: "This is Captain Ivanov speaking at minus five minutes. All crew members should be on station or standby, all passengers should have safety straps secured. Initial acceleration will be one hundredth gravity — ten centimeters second squared. I repeat, one hundredth gravity. This will be maintained for ten minutes while the propulsion system undergoes routine checks."

And suppose it doesn't pass those checks? Duncan asked himself. Do even the mathematicians know what would happen if the Asymptotic Drive started to malfunction? This line of thought was not very profitable, and he hastily abandoned it.

"Minus four minutes. Stewards check all passengers secured."

Now thatinstruction could not possibly be obeyed. There were three hundred twenty-five passengers, half of them in their cabins and the other half in the two lounges, and there was no way in which the dozen harassed stewards could see that all their charges were behaving. They had made one round of the ship at minus thirty and ten minutes, and passengers who had cut loose since then had only themselves to blame. And anyone who could be hurt by a hundredth of a gee, thought Duncan, certainly deserved it. Impacts at that acceleration had about the punch of a large wet sponge.

"Minus three minutes. All systems normal. Passengers in Lounge B will see Saturn rising."

Duncan permitted himself a slight glow of self-satisfaction. This was precisely why, after checking with one of the stewards, he was now in Lounge B. As Titan always kept the same face turned toward its primary, the spectacle of the great globe climbing above the horizon was one that could never be seen from the surface, even if the almost perpetual overcast of hydrocarbon clouds had permitted.

That blanket of clouds now lay a thousand kilometers below, hiding the whole world that it protected for the chill of space. And then suddenly — unexpectedly, even though he had been waiting for it — Saturn was rising like a golden ghost.

In all the known universe, there was nothing to compare with the wonder he was seeing now. A hundred times the size of the puny Moon that floated in the skies of Earth, the flattened yellow globe looked like an object lesson in planetary meteorology. Its knotted bands of cloud could change their appearance almost every hour, while thousands of kilometers down in the hydrogen-methane atmosphere, eruptions whose cause was still unknown would lift bubbles larger than terrestrial continents up from the hidden core. They would expand and burst as they reached the limits of the atmosphere, and in minutes Saturn's furious ten-hour spin would have smeared them out into long colored ribbons, stretching halfway round the planet.

Somewhere down there in that inferno, Duncan reminded himself with awe, Captain Kleinman had died seventy years ago, and so had part of Grandma Ellen. In all that time, no one had attempted to return. Saturn still represented one of the largest pieces of unfinished business in the Solar System — next, perhaps, to the smoldering hell of Venus.

The rings themselves were still so inconspicuous that it was easy to overlook them. By a cosmic irony, all the inner satellites lay in almost the same plane as the delicate, wafer-thin structure that made Saturn unique. Edge on, as they were now, the rings were visible only as hairlines of light jutting out on either side of the planet, yet they threw a broad, dusky band of shadow along the equator.

In a few hours, as Siriusrose above the orbital plane of Titan, the rings would open up in their full glory. And that alone, thought Duncan, would be enough to justify this voyage.

"Minus one minute..."

He had never even heard the two-minute mark; the great world rising out of the horizon clouds must have held him hypnotized. In sixty seconds, the automatic sequencer in the heart of the drive unit would initiate its final mysteries. Forces which only a handful of living men could envisage, and none could truly understand, would awaken in their fury, tear Siriusfrom the grip of Saturn, and hurl her sunward toward the distant goal of Earth.

"... ten seconds... five seconds... ignition!"

How strange that a word that had been technologically obsolete for at least two hundred years should have survived in the jargon of astronautics! Duncan barely had time to formulate this thought when he felt the onset of thrust. From exactly zero his weight leaped up to less than a kilogram. It was barely enough to dent the cushion above which he had been floating, and was detectable chiefly by the slackening tension of his waist belt.

Other effects were scarcely more dramatic. There was a distinct change in the timbre of the indefinable noises which never cease on board a spacecraft while its mechanical hearts are operating; and it seemed to Duncan that, far away, he could hear a faint hissing. But he was not even sure of that.

And then, a thousand kilometers below, he saw the unmistakable evidence that Siriuswas indeed breaking away from her orbit. The ship had been driving into night on its final circuit of Titan, and the wan sunlight had been swiftly fading on the sea of clouds far below. But now a second dawn had come, in a wide swathe across the face of the world he was soon to leave. For a hundred kilometers behind the accelerating ship, a column of incandescent plasma was splashing untold quintillions of candlepower out into space and across the carmine cloudscape of Titan. Siriuswas falling sunward in greater glory than the sun itself.

"Ten minutes after ignition. All drive checks complete. We will now be increasing thrust to our cruise level of point two gravities — two hundred centimeters second squared."

And now, for the first time, Siriuswas showing what she could do. In a smooth surge of power, thrust and weight climbed twenty-fold and held steady. The light on the clouds below was now so strong that it hurt the eye. Duncan even glanced at the still-rising disc of Saturn to see if it too showed any sign of this fierce new sun. He could now hear, faint but unmistakable, the steady whistling roar that would be the background to all life aboard the ship until the voyage ended. It must, he thought, be pure coincidence that the awesome voice of the Asymptotic Drive sounded so much like that of the old chemical rockets that first gave men the freedom of space. The plasma hurtling away from the ship's reactor was moving a thousand times more swiftly than the exhaust gases of any rocket, even a nuclear one; and how it created that apparently familiar noise was a puzzle that would not be solved by any naпve mechanical intuition.

"We are now on cruise mode at one-fifth gee. Passengers may unstrap themselves and move about freely — but please use caution until you are completely adapted."

That won't take mevery long, thought Duncan s he unbuckled himself; the ship's acceleration gave him his normal, Titan weight. Any residents of the Moon would also feel completely at home here, while Martians and Terrans would have a delightful sense of buoyancy.

The lights in the lounge, which had been dimmed almost to extinction for better viewing of the spectacle outside, slowly brightened to normal. The few first-magnitude stars that had been visible disappeared at once, and the gibbous globe of Saturn became bleached and pale, losing all its colors. Duncan could restore the scene by drawing the black curtains around the observation alcove, but his eyes would take several minutes to readapt. He was wondering whether to made the effort when the decision was made for him.

There was a musical "Ding- dong-ding," and a new voice, which sounded as if it came from a social stratum several degrees above the Captain's, announced languidly: "This is the Chief Steward. Will passengers kindly note that First Seating for lunch is at twelve hundred. Please do notattempt to make any changes without consulting me: Thank you." A less peremptory "Dong- ding-doing" signaled end of message.

Looking at the marvels of the universe made you hungry, Duncan instantly discovered. It was already 1150, and he was glad that he was in the First Seating. He wondered how many starving passengers were now converging upon the Chief Steward, in search of an earlier time slot.

Enjoying the sensation of man-made weight which, barring accidents, would remain constant until the moment of mid-voyage, Duncan went to join the rapidly lengthening line at the cafeteria. Already, his first thirty years of life on Titan seemed to belong to another existence.

12

Last Words

For one moment more, the achingly familiar image remained frozen on the screen. Behind Marissa and the children, Duncan could see the two armchairs of the living room, the photograph of Grandfather (as usual, slightly askew), the cover of the food-distribution hatch, the door to the main bedroom, the bookcase with the few but priceless treasures that had survived two centuries of interplanetary wandering... This was his universe. It held everything he loved, and now he was leaving it. Already, it lay in his past.

It lay only three seconds away, yet that was enough. He had traveled a mere million kilometers in less than half a day; but the sense of separation was already almost complete. It was intolerable to wait six seconds for every reaction and every answer. By the time a reply came, he had forgotten the original question and had started to say something else. And so the attempted conversation had quickly degenerated into a series of stops and starts, while he and Marissa had stared at each other in dumb misery, each waiting for the other to speak... He was glad that the ordeal was over.

The experience brought home to him, as nothing else had yet done, the sheer immensity of space. The Solar System, he began to suspect, was not designed for the convenience of Man, and that presumptuous creature's attempts to use it for his own advantage would often be foiled by laws beyond his control. All his life, Duncan had assumed without question that he could speak to friends or family instantly, wherever he might be. Yet now — before he had even passed Saturn's outer moons! — that power had been taken from him. For the next twenty days, he would share a lonely, isolated bubble of humanity, able to interact with his fellow passengers, but cut off from all real contact with the rest of mankind.

His self-pity lasted only a few moments. There was also an exhilaration — even a freedom — in this sense of isolation, and in the knowledge that he was setting forth on one of the longest and swiftest voyages that any man could make. Travel to the outer planets was routine and uneventful — but it was also rare, and only a very small fraction of the human race would ever experience it. Duncan remembered a favorite Terran phrase of Malcolm's, usually employed in a different context, but sound advice for every occasion: "When it's inevitable, relax and enjoy it." He would do his best to enjoy this voyage.

Yet Duncan was exhausted when he finally climbed into his bunk at the end of his first day in space. The strain of innumerable farewells, not only to his family but to countless friends, had left him emotionally drained. On top of this, there were all the nagging worries of departure: What had he forgotten to do? What vital necessities had he failed to pack? Had all his baggage been safely loaded and stowed? What essential good-byes had he overlooked? It was useless worrying about these matters now that he was speeding away from home at a velocity increasing by twenty-five thousand kilometers an hour, everyhour, yet he could not help doing so. Tired though he was, his hyperactive brain would not let him sleep.

It takes a real genius to make a bed that can be uncomfortable at a fifth of a gravity, and luckily the designers of Siriushad not accepted this challenging assignment. After thirty minutes or so, Duncan began to relax and to get his racing thoughts in order. He prided himself on being able to sleep without artificial aids, and it looked as if he would be able to dispense with electronarcosis after all. That was, of course, supposed to be completely harmless, but he never felt properly awake the next day.

You're falling asleep, he told himself. You won't know anything more until it’s time for breakfast. All your dreams are going to be happy ones...

A sound like a small volcano clearing its throat undid the good work of the last ten minutes. He was instantly wide awake, wondering what disaster had befallen Sirius. Not until several anxious seconds had passed did he realize that some antisocial shipmate had found it necessary to visit the adjacent toilet.

Cursing, he tried to recapture the broken mood and to return to the threshold of sleep. But it was useless; the myriad voices of the ship had started to clamor for his attention. He seemed to have lost control of the analytical portion of his brain, and it was busy classifying all the noises from the surrounding universe.

It had been hours since he had really noticed the far-off, ghostly whistling of the drive. Every second Siriuswas ejecting a hundred grams of hydrogen at a third of the velocity of light — a trifling loss of mass, yet it represented meaningless millions of gigawatts. During the first few centuries of the Industrial Revolution, all the factories of Earth could not have matched the power that was now driving him sunward.

That incongruously faint and feeble scream was not really disturbing, but it was overlaid with all sorts of other peculiar sounds. What could possibly cause the "Buzz... click, click... buzz," the soft "thump... thump... thump," the "gurgle, hisssss," and the intermittent "whee-wheee-whee" which was the most maddening of all?

Duncan rolled over and tried to bury his head in the pillows. It made no difference, except that the higher-pitched sounds got filtered out and the lower frequencies were enhanced. He also became more aware of the steady pulsation of the bed itself, at just about the ten cycles per second nicely calculated to produce epileptic fits.

Hello, thatwas something new. It was a kind of dispirited "ker- plunk, her- plunk, ker- plunk" that might have been produced by an ancient internal combustion engine in the last stages of decrepitude. Somehow, Duncan seriously doubted that i.c. engines, old or new, were to be found aboard Sirius.

He rolled over on the other side — and then became conscious of the slightly cold airstream from the ventilator hitting him on his left cheek. Perhaps if he ignored it, the sensation would sink below the threshold of consciousness. However, the very effort of pretending it wasn't there focused attention upon the annoyance.

On the other side of the thin partition, the ship's plumbing once again advertised its presence with a series of soft thumps. There was an air bubble somewhere in the system, and Duncan knew, with a deadly certainty, that all the engineering skills aboard the Siriuswould be unable to exorcise it before the end of the voyage.

And what was that?It was a rasping, whistling sound, so irregular that no well-adjusted mechanism could possibly have produced it. As Duncan lay in the darkness, racking his brains to think of an explanation, his annoyance slowly grew to alarm. Should he call the steward and report something had gone wrong?

He was still trying to make up his mind when a sudden explosive change in pitch and intensity left him in no doubt as to the sound's origin. Groaning and cursing his luck, Duncan resigned himself to a sleepless night.

Dr. Chung snored...

* * * * *

Some was gently shaking him. He mumbled "Go away," then swam groggily upward from the depths of slumber.

"If you don't hurry," said Dr. Chung, "you're going to miss breakfast."

13

The Longest Voyage

"This is the Captain speaking. We will be performing a final out-of-ecliptic velocity trim during the next fifteen minutes. This will be your last opportunity for a good view of Saturn, and we are orienting the ship so that it will be visible through the B Lounge windows. Thank you."

Thank you, thought Duncan, though he was a little less grateful when he reached B Lounge. This time too many other passengers had been tipped off by the stewards. Nevertheless, he managed to obtain a good vantage point, even though he had to stand.

Though the journey had scarcely begun, Saturn already seemed far away. The planet had dwindled to a quarter of its accustomed size; it was now only twice as large as the Moon would appear from Earth.

Yet though it had shrunk in size, it had gained in impressiveness. Siriushad risen several degrees out of the planet's equatorial plane, and now at last he could see the rings in all their glory. Thin, concentric silver haloes, they looked so artificial that it was almost impossible to believe that they were not the work of some cosmic craftsman whose raw materials were worlds. Although at first sight they appeared to be solid, when he looked more carefully Duncan could see the planet glimmering through them, its yellow light contrasting strangely with their immaculate, snowy whiteness. A hundred thousand kilometers below, the shadow of the rings lay in a dusky band along the equator; it could easily have been taken for an unusually dark cloud belt, rather than something whose cause lay far out in space.

The two main divisions of the rings were apparent at the most casual glance, but a more careful inspection revealed at least a dozen fainter boundaries where there were abrupt changes in brightness between adjacent sections. Ever since the rings had been discovered, back in the seventeenth century, mathematicians like Dr. Chung had been trying to account for their structure. It had long been known that the attractions of Saturn's many moons segregated the billions of orbiting particles into separate bands, but the details of the process were still unclear.

There was also a certain amount of variation within the individual bands themselves. The outermost ring, for example, showed a distinct mottling or beadiness, and a tiny clot of light was clearly visible near its eastern extremity. Was this, Duncan wondered, a moon about to be born — or the last remnants of one that had been destroyed?

Rather diffidently, he put the question to Dr. Chung.

"Both possibilities have been considered," she said. "My studies indicate the former. That condensation may, with luck, become another satellite in a few thousand years."

"I can't agree, Doctor," interjected another passenger. "It's merely a statistical fluctuation in the particle density. They're quite common, and seldom last more than a few years."

"The smallerones — yes. But this is too intense, and too near the edge of the B-ring."

"But Vanderplas' analysis of the Janus problem..."

At that moment, it became rather like the shoot-out in an old-time Western movie. The two scientists reached simultaneously for their hip computers and then retreated, muttering equations, to the back of the lounge. Thereafter, they completely ignored the realSaturn they had come so far to study — and which, in all probability, they would never see again.

"Captain speaking. We have concluded our velocity trim and are reorienting the ship into the plane of the ecliptic. I hope you had a good view — Saturn will be a long way off next time you see it."

There was no perceptible sense of motion, but the great ringed globe began to creep slowly down the observation window. The passengers in front craned forward to follow it, and there was a chorus of disappointed "Ohs" as it finally sank from view below the wide skirting that surrounded the lower part of the ship. That band of metal had one purpose only — to block any radiation from the jet that might stray forward. Even a momentary glimpse of that intolerable glare, bright as a supernova at the moment of detonation, could cause total blindness; a few seconds’ exposure would be lethal.

Siriuswas now aimed almost directly at the sun, as she accelerated toward the inner planets. While the drive was on, there could be no rear-viewing. Duncan knew that when he next saw Saturn with his unaided eyes, it would be merely a not-very-distinguished star.

A day later, moving at three hundred kilometers a second, the ship passed another milestone. She had, of course, escaped from the planet's gravitational field hours earlier; neither Saturn — nor, for that matter, the Sun — could ever recapture her. The frontier that Siriuswas crossing now was a purely arbitrary one: the orbit of the outermost moon.

Mnemosyne, only fifteen kilometers in diameter, could claim two modest records. It had the longest period of any satellite, taking no fewer than 1,139 days to orbit Saturn, at an average distance of twenty-one million kilometers. And it also had the longest day of anybody in the Solar System, its period of rotation being an amazing 1,143 days. Although it seemed obvious that these two facts must be connected, no one had been able to arrive at any plausible explanation of Mnemosyne's sluggish behavior.

Purely by chance, Siriuspassed within fewer than a million kilometers of the tiny world. At first, even under the highest power of the ship's telescope, Mnemosyne was only a minute crescent showing no visible features at all, but as it swiftly grew to a half-moon, patches of light and shade emerged which eventually resolved themselves into craters. It was typical of all the denser, Mercury-type satellites — as opposed to the inner snow-balls like Mimas, Enceladus, and Tethys — but to Duncan it now held a special interest. It was more to him than the last landmark on the road to Earth.

Karl was there, and had been for many weeks, with the joint Titan-Terran Outer Satellite Survey. Indeed, that survey had been in progress as long as Duncan could remember — the surface area of all the moons added up to a surprising number of million square kilometers — and the TTOSS team was doing a thorough job. There had been complaints about the cost, and the critics had subsided only when promised that the survey would be so thorough that it would never be necessary to go back to the outer moons again. Somehow, Duncan doubted that the promise would be kept.

He watched the pale crescent of Mnemosyne wax to full, simultaneously dwindling astern as the ship dropped sunward, and wondered fleetingly if he should send Karl a farewell greeting. But if he did, it would only be interpreted as a taunt.

* * * * *

It took Duncan several days to adjust to the complicated schedule of shipboard life — a schedule dominated by the fact that the dining room (as the lounge adjacent to the cafeteria was grandly called) could seat only one third of the passengers at a time. There were consequently three sittings for each of the three main meals — so for nine hours of every day, at least a hundred people were eating, while two hundred were either thinking about the next meal or grumbling about the last. This made it very difficult for the Purser, who doubled as Entertainment Officer, to organize any shipboard activities. The fact that most of the passengers had no wish to be organized did not help him.

Nevertheless, the day was loosely structured by a series of events, at which a good attendance was guaranteed by sheer boredom. There would be a thirty-minute newscast from Earth at 0800, with a repeat at 1000, and updates in the evening at 1900 and 2100. At the beginning of the voyage, the Earth news would be at least an hour and a half late, but it would become more and more timely as Siriusapproached her destination. When she reached her final parking orbit, a thousand kilometers above the Equator, the delay would be effectively zero, and watches could at last be set by the radio time signals. Those passengers who did not realize this were liable to get into a hopeless state of confusion and, even worse, to miss meal sittings.

All types of visual display, including the contents of several million volumes of fiction and nonfiction, as well as most of the musical treasures of mankind, were available in the tiny library; at a squeeze, it could hold ten people. However, there were two movie screenings every evening in the main lounge, selection being made — if the Purser could be believed — in the approved Democratic manner by public ballot. Almost all the great film classics were available, right back to the beginning of the twentieth century. For the first time in his life, Duncan saw Charlie Chaplin's Modern Times, much of the Disney canon, Olivier's Hamlet, Ray's Pather Panchali, Kubrick's Napoleon Bonaparte, Zymanowski's Moby Dick, and many other old masterpieces that had not even been names to him. But by far the greatest popular success was If This Is Tuesday, This Must Be Mars— a selection from the countless space-travel movies made in the days before space flight was actually achieved. This invariably reduced the audience to helpless hysterics, and it was hard to believe that it had once been banned for in-flight screening because some unimaginative bureaucrat feared that its disasters — such as accidentally arriving at the wrong planet — might alarm nervous passengers. In fact, it had just the opposite effect; they laughed too much to worry.

The big event of the day, however, was the lottery on the ship's run, simple but ingenious device for redistributing the wealth among the passengers. All that one had to do was to guess how far Siriushad traveled along her heliocentric trajectory during the previous twenty-four hours; any number of guests was permitted, at the cost of one solar each.

At noon, the Captain announced the correct result. The suspense was terrific, as he read out the figures very slowly: "Today's run has been two — two — seven — five — nine — zero — six — four — point — three kilometers." (Cheers and moans.) Since everyone knew the ship's position and acceleration, it required very little mathematics to calculate the first four or five figures, but beyond that the digits were completely arbitrary, so winning was a matter of luck. Although it was rumored that navigating officers had been bribed to trim the last few decimal places by minute adjustments to the thrust, no one had ever been able to prove it.

Another wealth-distributor was a noisy entertainment called "Bingo," apparently the main surviving relic of a once-flourishing religious order. Duncan attended one session, then decided that there were better ways of wasting time. Yet a surprising percentage of his very talented and intellectually superior companions seemed to enjoy this rather mindless ritual, jumping up and down and shrieking like small children when their numbers were called...

They could not be criticized for this; they needed some such relaxation. For they were the loneliest people in the Solar System; hundreds of millions of kilometers separated them from the rest of mankind. Everybody knew this, but no one ever mentioned it. Yet it would not have taken an astute psychologist to detect countless slightly unusual reactions — even minor symptoms of stress — in the behavior of Siriu s's passengers and crew.

There was, for example, a tendency to laugh at the feeblest of jokes, and to go into positive convulsions over catch phrases such as "This is the Captain speaking" or "Dining room closes in fifteen minutes." Most popular of all — at least among the men — was "Any more for Cabin 44." Why the two middle-aged and rather quiet lady geologists who occupied this cabin had acquired a reputation for ravening insatiability was a mystery that Duncan never solved.

Nor was he particularly interested; his heart still ached for Marissa and he would not seek any other consolation until he reached Earth. Moreover, with the somewhat excessive conscientiousness that was typical of the Makenzies, he was already hard at work by the second day of the voyage.

He had three major projects — one physical and two intellectual. The first, carried out under the hard, cold eye of the ship's doctor, was to get himself fit for life at one gravity. The second was to learn all that he could about his new home, so that he would not appear too much of a country cousin when he arrived. And the third was to prepare his speech of thanks, or at least to write a fairly detailed outline, which could be revised as necessary during the course of his stay.

The toughening-up process involved a fifteen-minute session, twice a day, in the ship's centrifuge or on the ‘race track.’ Nobody enjoyed the centrifuge; not even the best background music could alleviate the boredom of being whirled around in a tiny cabin until legs and arms appeared to be made of lead. But the race track was so much fun that it operated right around the clock, and some enthusiasts even tried to get extra time on it.

Part of its appeal was undoubtedly due to sheer novelty; who would have expected to find bicyclesin space? The track was a narrow tunnel, with steeply banked floor, completely encircling the ship, and rather like an old-time particle accelerator — except that in this case the particles themselves provided the acceleration.

Every evening, just before going to bed, Duncan would enter the tunnel, climb onto one of the bicycles, and start pedaling slowly around the sixty meters of track. His first revolution would take a leisurely half minute; then he would gradually work up to full speed. As he did so, he would rise higher and higher up the banked wall, until at maximum speed he was almost at right angles to the floor. At the same time, he would feel his weight steadily increase; the bicycle's speedometer had been calibrated to read in fractions of a gee, so he could tell exactly how well he was doing. Forty kilometers and hour — ten times around Siriusevery minute — was the equivalent of one Earth gravity. After several days of practice Duncan was able to maintain this for ten minutes without too much effort. By the end of the voyage, he could tolerate it indefinitely — as he would have to, when he reached Earth.

The race track was at its most exciting when it contained two or more riders — especially when they were moving at different speeds. Though overtaking was strictly forbidden, it was an irresistible challenge, and on this voyage there were no serious casualties. One of Duncan's most vivid and incongruous memories of Siriuswould be the tinkle of bicycle bells, echoing round and round in a brightly lit circular tunnel whose blurred walls flashed by only a few centimeters away... And the race track also provided him with a more material souvenir, a pseudomedieval scroll which announced to all who were interested that I, DUNCAN MAKENZIE, OF OASIS CITY, TITAN, AM HEREBY CERTIFIED TO HAVE BICYCLED FROM SATURN TO EARTH, AT AN AVERAGE VELOCITY OF 2,176,420 KILOMETERS AN HOUR.

Duncan's mental preparation for life on Earth occupied considerably more time, but was not quite so exhausting. He already had a good knowledge of Terran history, geography, and current affairs, but until now it had been mostly theoretical, because it had little direct application to him. Both astronomically and psychologically, Earth had been a long way off. Now it was coming closer by millions of kilometers a day.

Even more to the point, he was now surrounded by Terrans; there were only seven passengers from Titan aboard Sirius, so they were outnumbered fifty to one. Whether he liked it or not, Duncan was being rapidly brainwashed and molded by another culture. He found himself using Terran figures of speech, adopting the slightly sing-song intonation now universal on Earth, and employing more and more words of Chinese origin. All this was to be expected; what he found disturbing was the fact that his own swiftly receding world was becoming steadily more unreal. Before the voyage was finished, he suspected that he would have become half-Terran.

He spent much of his time viewing Earth scenes, listening to famous political debates, and trying to understand what was happening in culture and the arts, so that he would not appear to be a complete barbarian from the outer darkness. When he was not sitting at the viddy, he was likely to be flicking through the pages of a small, dense booklet optimistically entitled Earth in Ten Days. He was fond of trying out bits of new-found information on his fellow passengers, to study their reactions and to check on his own understanding. Sometimes the response was a blank stare, sometimes a slightly condescending smile. But everyone was very polite to him; after a while, Duncan realized that there was some truth in the old clichй that Terrans were never unintentionallyrude.

Of course, it was absurd to apply a single label to half a billion people — or even to the three hundred and fifty on the ship. Yet Duncan was surprised to find how often his preconceived ideas — even his prejudices — were perfectly accurate. Most Terrans didhave a quite unconscious air of superiority. At first, Duncan found it annoying; then he realized that several thousand years of history and culture justified a certain pride.

It was still too early for him to answer the question, so long debated on all the other worlds: "Is Earth becoming decadent?" The individuals he had met aboard Siriusshowed no trace of that effete oversensibility with which Terrans were frequently charged — but, of course, they were not a fair sample. Anyone who had occasion to visit the outer reaches of the Solar System must possess exceptional ability or resources.

He would have to wait until he reached Earth before he could measure its decadence more precisely. The project might be an interesting one — if his budget and his timetable could stand the strain.

14

Songs of Empire

In a hundred years, thought Duncan, he could never have managed to arrange this deliberately. Masterful administration of the unforeseen, indeed! Colin would be proud of him...

It had all begun quite accidentally. When he discovered that the Chief Engineer bore the scarcely uncommon name of Mackenzie, it had been natural enough to introduce himself and to compare family trees. A glance was sufficient to show that any relationship was remote: Warren Mackenzie, Doctor of Astrotechnology (Propulsion) was a freckled redhead.

It made no difference, for he was pleased to meet Duncan and happy to chat with him. A genuine friendship had developed, long before Duncan decided to take advantage of it.

"I sometimes feel," Warren lamented, not very seriously, "that I'm a living clichй. Did you know that there was a time when all ship's engineers were Scots and call Mac-something-or-other?"

"I didn't know it. Why not Germans or Russians? They started the whole thing."

"You're on the wrong wavelength. I'm talking about ships that float on water. The first powered ones were driven by steam — piston engines, working paddle wheels — around the beginning of the nineteenth century. Now, the Industrial Revolution started in Britain, and the first practical steam engine was made by a Scot. So when steamships began to operate all over the world, the Macs went with them. No one else could understand such complicated pieces of machinery."

" Steamengines? Complicated?You must be joking."

"Have you ever looked at one? More to it than you might think, though it doesn't take long to figure it out... Anyway, while the steamships lasted — that was only about a hundred years — the Scots ran them. I've made a hobby of the period; it has some surprising parallels with our time."

"Go on — surprise me."

"Well, those old ships were incredibly slow, averaging only about ten klicks, at least for freighters. So really long journeys, even on Earth, could take weeks. Just like space travel."

"I see. In those days, the countries on Earth were almost as far apart as the planets."

"Well, some of them. The most perfect analogy is the old British Commonwealth, the first and last world empire. For almost a hundred years, countries like Canada, India, and Australia relied entirely on steamships to link them to Britain; the one-way journey could easily take a month or more, and was often a once-in-a-lifetime affair. Only the wealthy, or people on official business, could afford it. And — just like today — people in the colonies couldn't even speak to the mother country. The psychological isolation was almost complete."

"They had telephones, didn't they?"

"Only for local use, and only a few even then. I'm talking about the beginning of the twentieth century, remember. Universal global communication didn't arrive until the end of it."

"I feel that the analogy is a little forced," protested Duncan. He was intrigued but unconvinced, and quite willing to listen to Mackenzie's arguments — as yet, with no ulterior motive.

"I can give you some more evidence that makes a better case. Have you heard of Rudyard Kipling?"

"Yes, though I've never read anything of his. He was a writer, wasn't he? Anglo-American — sometime between Melville and Hemingway. English Lit's almost unknown territory to me. Life's too short."

"True, alas. But I haveread Kipling. He was the first poet of the machine age, and some people think he was also the finest short-story writer of his century. I couldn't judge that, of course, but he exactly described the period I'm talking about. ‘McAndrew's Hymn,’ for example — an old engineer musing about the pistons and boilers and crankshafts that drive his ship round the world. Its technology — not to mention its theology! — has been extinct for three hundred years; but the spirit behind it is still as valid as ever."

"And he wrote poems and stories about the far places of the empire which make them seem quite as remote as the planets are today — and sometimes even more exotic! There's a favorite of mine called ‘The Song of The Cities.’ I don't understand half the allusions, but he tributes to Bombay, Singapore, Rangoon, Sydney, Aukland... make me think of Luna, Mercury, Mars, Titan..."

Mackenzie paused and looked just a little embarrassed.

"I've tried to do something of the same kind myself — but don’t worry, I won't inflict my verses on you."

Duncan made the encouraging noises he knew were expected. He was quite sure that before the end of the voyage he would be asked for his criticism — translation, praise — of Mackenzie's literary efforts.

It was a timely reminder of his own responsibilities. While the voyage was still beginning, he had better start work.

* * * * *

Exactly ten minutes, George Washington had directed — not a second more. Even the President will be allowed only fifteen, and all the planets must have equal time. The whole affair is scheduled to last two and a half hours, from the moment we enter the Capitol until we leave for the reception at the White House...

It still seemed faintly absurd to travel three billion kilometers to make a ten-minute speech, even for an occasion as unique as a five hundredth anniversary. Duncan was not going to waste more than the bare minimum of it on polite formalities; anyway, as Malcolm had pointed out, the sincerity of the speech of thanks is often inversely proportional to its length.

For his amusement — and, more important, because it would help to fix the other participants in his mind — Duncan had tried to compose a formal opening, based on the list of guests that Professor Washington had provided. It started off: "Madame President, Mr. Vice President, Honorable Chief Justice, Honorable Leader of the Senate, Honorable Leader of the House, Your Excellencies the Ambassadors for Luna, Mars, Mercury, Ganymede, and Titan" — at this point he would incline his head slightly toward Ambassador Farrell, if he could see him in the crowded gallery — "distinguished representatives from Albania, Austrand, Cyprus, Bohemia, France, Khmer, Palestine, Kalinga, Zimbabwe, Eire..." He calculated that if he acknowledged all fifty or sixty regions that still existed on some form of individual recognition, a quarter of his time would be expended before he had even begun. This, obviously, was absurd, and he hoped that all the other speakers would agree. Regardless of that protocol, Duncan had decided to opt for dignified brevity.

"People of Earth" would cover a lot of ground — to be precise, five times the area of Titan, an impressive statistic which Duncan knew by heart. But that would leave out the visitors; what about "Friends from other worlds"? No, that was too pretentious, since most of them would be complete strangers. Perhaps: "Madame President, distinguished guests, known and unknown friends from many worlds..." That was better, yet somehow it still didn't seem right.

There was more to this business, Duncan realized, than met the eye, or the ear. Plenty of people would be willing to give him advice, but he was determined, in the good old Makenzie tradition, to see what he could do himself before calling for help. He had read somewhere that the best way to learn to swim is by being thrown into deep water. Duncan could not swim — that skill being singularly useless on Titan — but he could appreciate the analogy. His career in Solar politics would start with a spectacular splash, and before the eyes of millions.

It was not that he was nervous; after all, he had addressed his whole world as an expert witness during technical debates in the Assembly. He had acquitted himself well when he weighed the complex arguments for and against mining the ammonia glaciers of Mount Nansen. Even Armand Helmer had congratulated him, despite the fact that they had reached opposing conclusions. In those debates, affecting the future of Titan, he had had real responsibility, and his career might have come to an abrupt end if he had made a fool of himself.

His Terran audience might be a thousand times larger, but it would be very much less critical. Indeed, his listeners would be friendly unless he committed the unpardonable sin of boring them.

This, however, he could not yet guarantee, for he still had no idea how he was going to use the most important ten minutes of his life.

15

At The Node

On the seas of Earth, they had called it "Crossing the Line." Whenever a ship had passed from one hemisphere to another, there had been light-hearted ceremonies and rituals, during which those who had never traversed the Equator before were subjected to ingenious indignities by Father Neptune and his Court.

During the first centuries of space flight, the equivalent transition involved no physical changes; only the navigational computer knew when a ship had ceased to fall toward one planet and was beginning to fall toward another. But now, with the advent of constant-acceleration drives, which could maintain thrust for the entire duration of a voyage, Midpoint, or "Turnaround," had logical impact. After living and moving for days in an apparent gravitational field, Sirius 'passengers would lose all weight for several hours, and could at least feel that they were reallyin space.

They could watch the slow rotation of the stars as the ship was swung through one hundred eighty degrees, and the drive was aimed precisely against its previous line of thrust, to slowly whittle away the enormous velocity built up over the preceding ten days. They could savor the thought that they were now moving faster than any human beings in history — and could also contemplate the exciting prospect that if the drive failed to restart, Siriuswould ultimately reach the nearest stars, in not much more than a thousand years...

All these things they could do; however, human nature having certain invariants, a majority of Sirius 'passengers had other possibilities in mind.

It was the only chance most of them would ever have of experiencing weightlessness long enough to enjoy it. What a crime to waste the opportunity! No wonder that the most popular item in the ship's library these last few days had been the Nasa Sutra, an old book and an old joke, explained so often that it was no longer funny.

Captain Ivanov denied, with a reasonably convincing show of indignation, that the ship's schedule had been designed to pander to the passengers' lower instincts. When the subject had been raised at the Captain's table, the day before Turnaround, he had put up quite a plausible defense.

"It's the only logical time to shut down the Drive," he had explained. "Between zero zero and zero four, all the passengers will be in their cabins, er, sleeping. So there will be a minimum of disturbance. We couldn'tclose down during the day — remember, the kitchens and the toilets will be out of action while we're weightless. Don't forget that! We'll remind everyone in the late evening, but some idiot always gets overconfident, or drinks too much, and doesn't have enough sense to read the instructions on those little plastic bags you'll find in your cabins — no thanks, Steward, I don’t feel like soup."

Duncan had been tempted; Marissa was beginning to fade, and there was no lack of opportunity. He had received unmistakable signals from several directions, and for groups with all values of nfrom one to five. It would not have been easy to make a choice, but Fate had saved him the trouble.

It was a full week, and Turnaround was only three days ahead, before he had felt confident enough of his increasing intimacy with Chief Engineer Mackenzie to drop some gentle hints. They had not been rejected out of hand, but Warren obviously wanted time to weigh the possibilities. He gave Duncan his decision only twelve hours in advance.

"I won't pretend this might cost me my job," he said, "but it could be embarrassing, to say the least, if it got around. But you area Makenzie, and a Special Assistant to the Administrator, and all that. If the worst comes to the worst, which I hope it won't, we can say your request's official."

"Of course. I understand completely, and I really appreciate what you're doing. I won't let you down."

"Now there's the question of timing. If everything checks out smoothly — and I've no reason to expect otherwise — I'll be through in two hours and can dismiss my assistants. They'll leave like meteors — they'll all have something lined up, you can be sure of that— so we'll have the place to ourselves. I'll give you a call at zero two, or as soon after as possible."

"I hope I'm not interrupting any — ah — personal plans you've made."

"As it happens, no. The novelty's worn off. What are you smiling at?"

"It's just occurred to me," Duncan answered, "that if anyone does meet the pair of us at two o'clock on the morning of Turnaround, we'll have a perfect alibi..."

Nevertheless, he felt a mild sense of guilt as he drifted along the corridors behind Warren Mackenzie. The weightless — but far from sleeping — ship might have been deserted, for there was no occasion now for anyone to descend below the freight deck on Level Three. It was not even necessary to pretend that they were heading for an innocent assignation.

Yet the guilt was there, and he knew why. He was taking advantage of a friendship for secret purposes of his own, by suggesting that his interest in the Asymptotic Drive was no more than would be expected from anyone with a scientific or engineering background. But perhaps Warren was not as naпve as he seemed; he could hardly be unaware that the Drive posed a threat to the entire economy of Duncan's society. He might even be trying to help, in a tactful way.

"You may be disappointed," said Warren as they passed through the bulkhead floor separating Levels Three and Two. "There's not much to see. But what there is is enough to give some people nightmares — which is why we discourage visitors."

Not the most important reason, thought Duncan. The Drive was not exactly a secret; there was an immense literature on the subject, from the most esoteric mathematical papers down to popularizations so elementary that they amounted to little more than: "You pull on your bootstraps, and away you go." But it would be fair to say that Earth's Space Transportation Authority was curiously evasive when it came down to the practical details, and only its own personnel were allowed on the minor planet where the Drive was assembled. The few photos of Asteroid 4587 were blurred telescopic shots showing two cylindrical structures, more than a thousand kilometers long, stretching out into space on either side of the tiny world, which was an almost invisible speck between them. It was known that these were the accelerators that smashed matter together at such velocities that it fused to form the node or singularity at the heart of the Drive; and this was all that anyone didknow, outside the STA.

Duncan was now floating, a few meters behind his guide, along a corridor lined with pipes and cable ducts — all the anonymous plumbing of any vehicle of sea, air, or space for the last three hundred years. Only the remarkable number of handholds, and the profusion of thick padding, revealed that this was the interior of a ship designed to be independent of gravity.

"D'you see that pipe?" said the engineer. "The little red one?"

"Yes — what about it?"

Duncan would certainly never have given it a second glance; it was only about as thick as a lead pencil.

" That'sthe main hydrogen feed, believe it or not. All of a hundred grams a second. Say eight tons a day, under full thrust."

Duncan wondered what the old-time rocket engineers would have thought of this tiny fuel line. He tried to visualize the monstrous pipes and pumps of the Saturns that had first taken men to the Moon; what was their rate of fuel consumption? He was certain that they burned more in every second than Siriusconsumed in a day. That was a good measure of how far technology had progressed, in three centuries. And in another three...?

"Mind your head — those are the deflection coils. We don't trust room-temperature superconductors. These are still good old cryogenics."

"Deflection coils? What for?"

"Ever stopped to think what would happen if that jet accidentally touched part of the ship? These coils keep it centered, and also give it all the vector control we need."

They were now hovering beside a massive — yet still surprisingly small — cylinder that might have been the barrel of a twentieth-century naval gun. So this was the reaction chamber of the Drive.

It was hard not to feel a sense of almost superstitious awe at the knowledge of what lay within a few centimeters of him. Duncan could easily have encircled the metal tube with his arms; how strange to think of putting your arms around a singularity, and thus, if some of the theories were correct, embracing an entire universe...

Near the middle of the five-meter-long tube a small section of the casing had been removed, like the door of some miniature bank vault, and replaced by a crystal window. Through this obviously temporary opening a microscope, mounted on a swinging arm so that it could be moved away after use, was aimed into the interior of the drive unit.

The engineer clipped himself into position by the buckles conveniently fixed to the casing, stared through the eyepiece, and made some delicate micrometer adjustments.

"Take a look," he said, when he was finally satisfied.

Duncan floated to the eyepiece and fastened himself rather clumsily in place. He did not know what he had expected to see, and he remembered that the eye had to be educated before it could pass intelligible impressions to the brain. Anything utterly unfamiliar could be, quite literally, invisible, so he was not too disappointed at his first view.

What he saw was, indeed, perfectly ordinary — merely a grid of fine hairlines, crossing at right angles to from a reticule of the kind commonly used for optical measurements. Though he searched the brightly lit field of view, he could find nothing else; he might have been exploring a piece of blank graph paper.

"Look at the crossover at the exact center," said his guide, "and turn the knob to the left — veryslowly. Half a rev will do — either direction."

Duncan obeyed, yet for a few seconds he could still see nothing. Then he realized that a tiny bulge was creeping along the hairline as he tracked the microscope. It was as if he was looking at the reticule through a sheet of glass with one minute bubble or imperfection in it.

"Do you see it?"

"Yes — just. Like a pinhead-sized lens. Without the grid, you'd never notice it."

"Pinhead-sized! That'san exaggeration, if I ever heard one. The node's smaller than an atomic nucleus. You're not actually seeing it, of course — only the distortion it produces."

"And yet there are thousands of tons of matter in there."

"Well, one or two thousand," answered the engineer, rather evasively. "It's made a dozen trips and is getting near saturation, so we'll soon have to install a new one. Of course it would go on absorbing hydrogen as long as we fed it, but we can't drag too much unnecessary mass around, or we'll pay for it in performance. Like the old seagoing ships — they used to get covered with barnacles, and slowed down if they weren't scraped clean every so often."

"What do they do with old nodes when they're too massive to use? Is it true that they're dropped into the sun?"

"What good would that do? A node would sail right through the sun and out the other side. Frankly, I don't know what they do with the old ones. Perhaps they lump them all together into a big granddaddy node, smaller than a neutron but weighing a few million tons."

There were a dozen other questions that Duncan was longing to ask. How were these tiny yet immensely massive objects handled? Now that Siriuswas in free fall, the node would remain floating where it was — but what kept it from shooting out of the drive tube as soon as acceleration started? He assumed that some combination of powerful electric and magnetic fields held it in place, and transmitted its thrust to the ship.

"What would happen," Duncan asked, "If I tried to touch it?"

"You know, absolutely everyoneasks that question."

"I'm not surprised. What's the answer?"

"Well, you'd have to open the vacuum seal, and then all hell would break loose as the air rushed in."

"Then I don't do it that way. I wear a spacesuit, and I crawl up the drive tunnel and reach out a finger..."

"How clever of you to hit exactly the right spot! But if you did, when your finger got within — oh —something like a millimeter, I'd guess — the gravitational tidal forces would start to tear away at it. As soon as the first few atoms fell into the field, they'd give up all their mass-energy — and you'd think that a small hydrogen bomb had gone off in your face. The explosion would probably blow you out of the tube at a fair fraction of the speed of light."

Duncan gave an uncomfortable little laugh.

"It would certainly take a clever man to steal one of your babies. Doesn't it ever give you nightmares?"

"No. It's the tool I'm trained to use, and I understand its little ways. Ican't imagine handling power lasers — they scare the hell out of me. You know, old Kipling had it all summed up, as usual. You remember me talking about him?"

"Yes."

"He wrote a poem called ‘The Secret of the Machines,’ and it has some lines I often say to myself when I'm down here:

"But remember, please, the Law by which we live,

We are not built to comprehend a lie,

We can neither love nor pity nor forgive.

If you make a slip in handling us you die!

"And that's true of all machines — all the natural forces we've ever learned to handle. There's no real difference between the first caveman's fire and the node in the heart of the Asymptotic Drive."

An hour later, Duncan lay sleepless in his bunk, waiting for the Drive to go on and for Siriusto begin the ten days of deceleration that would lead to her rendezvous with Earth. He could still see that tiny flaw in the structure of space, hanging there in the field of the microscope, and knew that its image would haunt him for the rest of his life. And he realized now that Warren Mackenzie had betrayed nothing of his trust; all that he had learned had been published a thousand times. But no words or photos could ever convey the emotional impact he had experienced.

Tiny fingers began to tug at him; weight was returning to Sirius. From an infinite distance came the thin wail of the Drive; Duncan told himself that he was listening to the death cry of matter as it left the known universe, bequeathing to the ship all the energy of its mass in the final moment of dissolution. Every minute, several kilograms of hydrogen were falling into that tiny but insatiable vortex — the hole that could never be filled.

Duncan slept poorly for the rest of the night. He had dreams that he too was falling, falling into a spinning whirlpool, indefinitely deep. As he fell, he was being crushed to molecular, to atomic, and finally to subnuclear dimensions. In a moment, it would all be over, and he would disappear in a single flash of radiation...

But that moment never came, because as Space contracted, Time stretched endlessly, the passing seconds becoming longer... and longer — until he was trapped forever in a changeless Eternity.

16

Port Van Allen

When Duncan had gone to bed for the last time aboard Sirius, Earth was still five million kilometers away. Now it seemed to fill the sky — and it was exactly like the photographs. He had laughed when more seasoned travelers told him he would be surprised at this; now he was ruefully surprised at his surprise.

Because the ship had cut right across the Earth's orbit, they were approaching from sunward, and the hemisphere below was almost fully illuminated. White continents of cloud covered most of the day side, and there were only rare glimpses of land, impossible to identify without a map. The dazzling glare of the Antarctic icecap was the most prominent surface feature; it looked very cold down there, yet Duncan reminded himself that it was tropical in comparison with much of his world.

Earth was a beautiful planet; that was beyond dispute. But it was also alien, and its cool whites and blues did nothing to warm his heart. It was indeed a paradox that Titan, with its cheerful orange clouds, looked so much more hospitable from space.

Duncan stayed in Lounge B, watching the approaching Earth and making his farewells to many temporary friends, until Port Van Allen was a dazzling star against the blackness of space, then a glittering ring, then a huge, slowly turning wheel. Weight gradually ebbed away as the drive that had taken them halfway across the Solar System decreased its thrust to zero; then there were only occasional nudges as low-powered thrustors trimmed the attitude of the ship.

The space station continued to expand. Its size was incredible, even when one realized that it had been steadily growing for almost three centuries. Now it completely eclipsed the planet whose commerce it directed and controlled; a moment later a barely perceptible vibration, instantly damped out, informed everybody that the ship had docked. A few seconds later, the Captain confirmed it.

"Welcome to Port Van Allen — Gateway to Earth. It's been nice having you with us, and I hope you enjoy your stay. Please follow the stewards, and check that you've left nothing in your cabins. And I'm sorry to mention this, but three passengers stillhaven't settled their accounts. The Purser will be waiting for them at the exit..."

A few derisive groans and cheers greeted this announcement, but were quickly lost in the noisy bustle of disembarkation. Although everything was supposed to have been carefully planned, chaos was rampant. The wrong passengers went to the wrong checkpoints, while the public-address system called plaintively for individuals with improbable names. It took Duncan more than an hour to get into the spaceport, and he did not see all of his baggage again until his second day on Earth.

But at last the confusion abated as people squeezed through the bottleneck of the docking hub and sorted themselves out in the appropriate levels of the station. Duncan followed instructions conscientiously, and eventually found himself, with the rest of his alphabetical group, lined up outside the Quarantine Office. All other formalities had been completed hours ago, by radio circuit; but this was something that could not be done by electronics. Occasionally, travelers had been turned back at this point, on the very doorstep of Earth, and it was not without qualms that Duncan confronted this last hurdle.

"We don't get many visitors from Titan," said the medical officer who checked his record. "You come in the Lunar classification — less than a quarter gee. It may be tough down there for the first week, but you're young enough to adapt. It helps if both your parents were born..."

The doctor's voice trailed off into silence; he had come to the entry marked MOTHER. Duncan was used to the reaction, and it had long ago ceased to bother him. Indeed, he derived a certain amusement from the surprise that discovery of his status usually produced. At least the M.O. would not ask the silly question that laymen so often asked, and to which he had long ago formulated an automatic reply: "Of course I've got a navel — the best that money can buy." The other common myth — that male close must be abnormally virile "because they had one father twice" — he had wisely left unchallenged. It had been useful to him on several occasions.

Perhaps because there were six other people waiting in line, the doctor suppressed any scientific curiosity he may have felt, and sent Duncan "upstairs" to the Earth-gravity section of the spaceport. It seemed a long time before the elevator, moving out along one of the spokes of the slowly spinning wheel, finally reached the rim; and all the while, Duncan felt his weight increasing remorselessly.

When the doors opened at last, he walked stiff-legged out of the cage. Though he was still a thousand kilometers above the Earth, and his new-found weight was entirely artificial, he felt that he was already in the cruel grip of the planet below. If he could not pass the test, he would be shipped back to Titan in disgrace.

It was true that those who justfailed to make the grade could take a high-speed toughening-up course, primarily intended for returning Lunar residents. This, however, was safe only for those who had spent most of their infancy on Earth, and Duncan could not possibly qualify.

He forgot all these fears when he entered the lounge and saw the crescent Earth, filling half the sky and slowly sliding along the huge observation windows — themselves a famous tour de forceof space engineering. Duncan had no intention of calculating how many tons of air pressure they were resisting; as he walked up to the nearest, it was easy to imagine that there was nothing protecting him from the vacuum of space. The sensation was both exhilarating and disturbing.

He had intended to go through the check list that the doctor had given him, but that awesome view made it impossible. He stood rooted to the spot, only shifting his unaccustomed weight from one foot to the other as hitherto unknown muscles registered their complaints.

Port Van Allen circled the globe every two hours, and also rotated on its own axis three times a minute. After a while, Duncan found that he could ignore the station's own spin; his mind was able to cancel it out, like an irrelevant background noise or a persistent but neutral odor. Once he had achieved this mental attitude, he could imagine that the was alone in space, a human satellite racing along the Equator from night into day. For the Earth was waxing visibly even as he watched, the curved line of dawn moving steadily away from him as he hurtled into the east.

As usual, there was little land visible, and what could be seen through or between the clouds seemed to have no relationship to any maps. And from this altitude there was not the slightest sign of life — still less of intelligence. It was very hard to believe that most of human history had take place beneath that blanket of brilliant white, and that, until a mere three hundred years ago, no man had ever risen above it.

He was still searching for signs of life when the disc started to contract to a crescent once more, and the public-address system called on all passengers for Earth to report to the shuttle embarkation area, Elevators Two and Three.

He just had time to stop of the "Last Chance" toilet — almost as famous as the lounge windows — and then he was down by elevator again, back into the weightless world of the station's hub, where the Earth-to-orbit shuttle was being readied for its return journey.

There were no windows here, but each passenger had his own vision screen, on the back of the seat in front of him, and could switch to forward, rear, or downward as preferred. The choice was not completely free, though this fact was not widely advertised. Images that were likely to be too disturbing — like the final moments of docking or touchdown — were thoughtfully censored by the ship's computer.

It was pleasant to be weightless again — if only during the fifty minutes needed for the fall down to the edge of the atmosphere — and to watch the Earth slowly changing from a planet to a world. The curve of the horizon became flatter and flatter; there were fleeting glimpses of island and the spiral nebula of a great storm, raging in silence far below. Then at last a feature that Duncan could recognize — the characteristic narrow isthmus of the California coastline, as the shuttle dropped out of the Pacific skies for its final landfall, still the width of a continent away.

He felt himself sinking deeper and deeper into the superbly padded seat, which spread the load so evenly over his body that there was the minimum of discomfort. But it was hard to breathe, until he remembered the "Advice to Passengers" he had finally managed to read. Don't try to inhale deeply, it had said; take short, sharp pants, to reduce the strain on the chest muscles. He tried it, and it worked.

Now there was a gently buffeting and a distant roar, and the vision screen flared into momentary flame, then switched automatically from the fires of reentry to the view astern. The canyons and deserts dwindled behind, to be replace by a group of lakes — obviously artificial, with the tiny white flecks of sailboats clearly visible. He caught a glimpse of the huge V-shaped wake, kilometers long, of some vessel going at great speed over the water, although from this altitude it seemed completely motionless.

Then the scene changed with an abruptness that took him by surprise. He might have been flying over the ocean once more, so uniform was the view below. Still so high that he could not see the individual trees, he was passing over the endless forests of the American Midwest.

Here indeed was proof of Life, on a scale such as he had never imagined. On all of Titan, there were fewer than a hundred trees, cherished and protected with loving care. Spread out beneath him now were incomputable millions.

Somewhere, Duncan had encountered the phrase "primeval forest," and now it flashed again into his mind. So must the Earth have looked in the ancient days, before Man had set to work upon it with fire and axe. Now, with the ending of the brief Agricultural Age, much of the planet was reverting to something like its original state.

Though the fact was very hard to believe, Duncan knew perfectly well that the "primeval forest" lying endlessly beneath him was not much older than Grandfather. Only two centuries ago, this had all been farmland, divided into enormous checkerboards and covered in the autumn with golden grain. "That concept of seasons was another local reality he found extremely difficult to grasp...) There were still plenty of farms in the world, run by eccentric hobbyists or biological research organizations, but the disasters of the twentieth century had taught men never again to rely on a technology that, at its very best, had an efficiency of barely one percent.

The sun was sinking, driven down into the west with unnatural speed by the shuttle's velocity. It clung to the horizon for a few seconds, then winked out. For perhaps a minute longer the forest was still visible; then it faded into obscurity.

But not into darkness. As if by magic, faint lines of light had appeared on the land below — spiders' webs of luminosity, stretching as far as the eye could see. Sometimes three or four lines would meet at a single glowing knot. There were also isolated islands of phosphorescence, apparently unconnected with the main network. Here was further proof of Man's existence; that great forest was a much busier place than it appeared to be by daylight. Yet Duncan could to help comparing this modest display with pictures he had seen from the early Atomic Age, when millions of square kilometers blazed at night with such brilliance that men could no longer see the stars.

He suddenly became aware of a compact constellation of flashing lights, moving independently of the glimmering landscape far below. For a moment, he was baffled; then he realized that he was watching some great airship, cruising not much faster than a cloud with its cargo of freight or passengers. This was one experience Titan could not provide. He determined to enjoy it as soon as the opportunity arose.

And there was a city — quite a big one, at least a hundred thousand people. The shuttle was now so low that he could make out blocks of buildings, roads, parks, and a stadium blazing with light, presumably the scene of some sporting event. The city fell astern, and a few minutes later everything was lost in a gray mist, lit by occasional flashes of lightning, not very impressive by the standards of Titan. Inside the cabin, Duncan could hear nothing of the storm through which they were now flying, but the vibration of the engines had taken on a new note and he could sense that the ship was dropping rapidly. Nevertheless, he was taken completely by surprise when there was a sudden surge of weight, the slightest of jolts — and there on the screen was a sea of wet concrete, a confusion of lights, and half a dozen buses and service vehicles scurrying around in the driving rain.

After thirty years, Duncan Makenzie had returned to the world where he was born, but which he had never seen...

Part Three

Terra

17

Washington, D.C.

"Sorry about the weather," said George Washington. "We used to have local climate control, but gave it up after an Independence Day parade was blocked by snow."

Duncan laughed dutifully, though he was not quite sure if he was supposed to believe this.

"I don't mind," he said. "It's all new to me. I've never seen rain before."

That was not the literal truth, but it was near enough. He had often driven through ammonia gales and could still remember the poisonous cascades streaming down the windows only a few centimeters before his eyes. But this was harmless — no, beneficent— water, the source of life both on Earth and on Titan. If he opened the door now he would merely get wet; he would not die horribly. But the instincts of a lifetime were hard to overcome, and he knew that it would require a real effort of will to leave the protection of the limousine.

And it was a genuine limousine — another first for Duncan. Never before had he traveled in such sybaritic comfort, with a communications console on one side and a well-stocked bar on the other. Washington saw his admiring gaze and commented: "Impressive, isn't it? They don't make them any more. This was President Bernstein's favorite car."

Duncan was not too good on American presidents — after all, there had been by now ninety-five of them — but he had an approximate idea of Bernstein's date. He performed a quick calculation, didn't believe the result, and repeated it.

"That means — it's more than a hundred and fifty years old!"

" Andit's probably good for another hundred and fifty. Of course, the upholstery — real leather, notice — is replaced every twenty years or so. If these seats could talk, they could tell some secrets. As a matter of fact, they often did — by you have my personal assurance that it's now been thoroughly debugged."

"Debugged? Oh, I know what you mean. Anyway, I don’t have any secrets."

"Then we'll soon provide you with some; that's our chief local industry."

As the beautiful old car cruised in almost perfect silence under the guidance of its automatic controls, Duncan tried to see something of the terrain through which he was passing. The spaceport was fifty kilometers from the city — no one had yet invented a noiseless rocket — and the four-lane highway bore a surprising amount of traffic. Duncan could count at least twenty vehicles of various types, and even though they were all moving in the same direction, the spectacle was somewhat alarming.