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. I can’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 Sirius to 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 sub nuclear 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… and longer -until he was trapped forever in a changeless Eternity.

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 everyone 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 still haven’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 door step 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 now 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 clones must be abnormally virile “because the had one father twice”-he had wisely left unchY lenged. 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 just failed to make the grade could take a highspeed 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 cresent

Earth, filling half the sky and slowly sliding along the huge observation windows-themselves a famous tour de * force of 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.