"Two hours!" exclaimed Floyd. "No wonder that they've spread over half the planet. It's a textbook case of exponential growth."
"I know what they are!" said Ternovsky in sudden excitement. "They're von Neumann machines!"
"I believe you're right," said Vasili. "But that still doesn't explain what they're doing. Giving them a label isn't all that much help."
"And what," asked Katerina plaintively, "is a von Neumann machine? Explain, please."
Orlov and Floyd started speaking simultaneously. They stopped in some confusion, then Vasili laughed and waved to the American.
"Suppose you had a very big engineering job to do, Katerina - and I mean big, like strip-mining the entire face of the Moon. You could build millions of machines to do it, but that might take centuries. If you were clever enough, you'd make just one machine - but with the ability to reproduce itself from the raw materials around it. So you'd start a chain reaction, and in a very short time, you'd have bred enough machines to do the job in decades, instead of millennia. With a sufficiently high rate of reproduction, you could do virtually anything in as short a period of time as you wished. The Space Agency's been toying with the idea for years - and I know you have as well, Tanya."
"Yes: exponentiating machines. One idea that even Tsiolkovski didn't think of."
"I wouldn't care to bet on that," said Vasili. "So it looks, Katerina, as if your analogy was pretty close. A bacteriophage is a von Neumann machine."
"Aren't we all?" asked Sasha. "I'm sure Chandra would say so."
Chandra nodded his agreement.
"That's obvious. In fact, von Neumann got the original idea from studying living systems."
"And these living machines are eating Jupiter!"
"It certainly looks like it," said Vasili. "I've been doing some calculations, and I can't quite believe the answers - even though it's simple arithmetic."
"It may be simple to you," said Katerina. "Try to let us have it without tensors and differential equations."
"No - I mean simple," insisted Vasili. "In fact, it's a perfect example of the old population explosion you doctors were always screaming about in the last century. Zagadka reproduces every two hours. So in only twenty hours there will be ten doublings. One Zagadka will have become a thousand."
"One thousand and twenty-four," said Chandra.
"I know, but let's keep it simple. After forty hours there will be a million - after eighty, a million million. That's about where we are now, and obviously, the increase can't continue indefinitely. In a couple more days, at this rate, they'll weigh more than Jupiter!"
"So they'll soon begin to starve," said Zenia. "And what will happen then?"
"Saturn had better look out," answered Brailovsky. "Then Uranus and Neptune. Let's hope they don't notice little Earth."
"What a hope! Zagadka's been spying on us for three million years!"
Walter Curnow suddenly started to laugh.
"What's so funny?" demanded Tanya.
"We're talking about these things as if they're persons - intelligent entities. They're not - they're tools. But general-purpose tools - able to do anything they have to. The one on the Moon was a signalling device - or a spy, if you like. The one that Bowman met - our original Zagadka - was some kind of transportation system. Now it's doing something else, though God knows what. And there may be others all over the Universe."
"I had just such a gadget when I was a kid... Do you know what Zagadka really is? Just the cosmic equivalent of the good old Swiss Army knife!"
VII: LUCIFER RISING
50
Farewell to Jupiter
It was not easy to compose the message, especially after the one he had just sent to his lawyer. Floyd felt like a hypocrite; but he knew it had to be done to minimize the pain that was inevitable on both sides.
He was sad, but no longer disconsolate. Because he was coming back to Earth in an aura of successful achievement - even if not precisely heroism - he would be bargaining from a position of strength. No one - no one - would be able to take Chris away from him.
"My dear Caroline [it was no longer 'My dearest'], I am on my way home. By the time you get this, I'll already be in hibernation. Only a few hours from now, as it will seem to me, I'll open my eyes - and there will be the beautiful blue Earth hanging in space beside me.
"Yes, I know it will still be many months for you, and I'm sorry. But we knew that's the way it would be before I left; as it is, I'm getting back weeks ahead of schedule because of the change in the mission plan.
"I hope we can work something out. The main question is: What's best for Chris? Whatever our own feelings, we must put him first. I know I'm willing to do so, and I'm sure you are."
Floyd switched off the recorder. Should he say what he had intended: 'A boy needs his father?' No - it would not be tactful, and might only make matters worse. Caroline might well retort that between birth and four years old it was the mother who mattered most to a child - and if he had believed otherwise, he should have stayed on Earth.
"... Now about the house. I'm glad the Regents have taken that attitude, which will make it much easier for both of us. I know we both loved the place, but it will be too big now and will bring back too many memories. For the time being, I'll probably get an apartment in Hilo: I hope I can find some permanent place as quickly as possible.
"That's one thing I can promise everyone - I won't leave Earth again. I've had enough of space travelling for one lifetime. Oh, perhaps the Moon, if I really have to - but of course that's just a weekend excursion.
"And talking of moons, we've just passed the orbit of Sinope, so we're now leaving the Jovian system. Jupiter is more than twenty million kilometres away, and is barely larger than our own Moon.
"Yet even from this distance, you can tell that something terrible has happened to the planet. Its beautiful orange colour has vanished; it's a kind of sickly grey, only a fraction of its former brilliance. No wonder it's only a faint star now in the sky of Earth.
"But nothing else has happened, and we're well past the deadline. Could the whole thing have been a false alarm or a kind of cosmic practical joke? I doubt if we'll ever know. Anyway, it's brought us home ahead of schedule, and I'm grateful for that.
"Goodbye for the present, Caroline - and thank you for everything. I hope we can still be friends. And my dearest love, as ever, to Chris."
When he had finished, Floyd sat quietly for a while in the tiny cubicle he would not need much longer. He was just about to carry the audio chip up to the bridge for transmission, when Chandra came drifting in.
Floyd had been agreeably surprised by the way in which the scientist had accepted his increasing separation from Hal. They were still in touch for several hours every day, exchanging data on Jupiter and monitoring conditions aboard Discovery. Though no one had expected any great display of emotion, Chandra seemed to be taking his loss with remarkable fortitude. Nikolai Ternovsky, his only confidant, had been able to give Floyd a plausible explanation of his behaviour.
"Chandra's got a new interest, Woody. Remember - he's in a business where if something works, it's obsolete. He's learned a lot in the last few months. Can't you guess what he's doing now?"
"Frankly, no. You tell me."
"He's busy designing HAL 10,000."
Floyd's jaw dropped. 'So that explains those log messages to Urbana that Sasha's been grumbling about. Well, he won't be blocking the circuits much longer."
Floyd recalled the conversation when Chandra entered; he knew better than to ask the scientist if it was true, for it was really none of his business. Yet there was another matter about which he was still curious.
"Chandra," he said, "I don't believe I ever thanked you properly for the job you did at the flyby, when you persuaded Hal to cooperate. For a while, I was really afraid he'd give us trouble. But you were confident all along - and you were right. Still, didn't you have any qualms?"
"Not at all, Dr Floyd."
"Why
not? He must have felt threatened by the situation - and you know what happened last time."
"There was a big difference. If I may say so, perhaps the successful outcome this time had something to do with our national characteristics."
"I don't understand."
"Put it this way, Dr Floyd. Bowman tried to use force against Hal. I didn't. In my language we have a word - ahimsa. It's usually translated as 'non-violence', though it has more positive implications. I was careful to use ahimsa in my dealings with Hal."
"Very commendable, I'm sure. But there are times when something more energetic is needed, regrettable though the necessity may be.' Floyd paused, wrestling with temptation. Chandra's holier-than-thou attitude was a little tiresome. It wouldn't do any harm, now, to tell him some of the facts of life.
"I'm glad it's worked out this way. But it might not have done so, and I had to prepare for every eventuality. Ahimsa, or whatever you call it, is all very well; I don't mind admitting I had a back-up to your philosophy. If Hal had been - well, stubborn, I could have dealt with him."
Floyd had once seen Chandra crying; now he saw him laughing, and that was an equally disconcerting phenomenon.
"Really, Dr Floyd! I'm sorry you give me such low marks for intelligence. It was obvious from the beginning that you'd install a power cut-out somewhere. I disconnected it months ago."
Whether the flabbergasted Floyd could think of a suitable answer would never be known. He was still giving a very creditable imitation of a galled fish when up on the flight deck Sasha cried out: "Captain! All hands! Get to the monitors! BOZHE MOI! LOOK AT THAT!"
51
The Great Game
Now the long wait was ending. On yet another world, intelligence had been born and was escaping from its planetary cradle. An ancient experiment was about to reach its climax.
Those who had begun that experiment, so long ago, had not been men - or even remotely human. But they were flesh and blood, and when they looked out across the deeps of space, they had felt awe, and wonder, and loneliness. As soon as they possessed the power, they set forth for the stars. In their explorations, they encountered life in many forms and watched the workings of evolution on a thousand worlds. They saw how often the first faint sparks of intelligence flickered and died in the cosmic night.
And because, in all the Galaxy, they had found nothing more precious than Mind, they encouraged its dawning everywhere. They became farmers in the fields of stars; they sowed, and sometimes they reaped.
And sometimes, dispassionately, they had to weed.
The great dinosaurs had long since perished when the survey ship entered the Solar System after a voyage that had already lasted a thousand years. It swept past the frozen outer planets, paused briefly above the deserts of dying Mars, and presently looked down on Earth.
Spread out beneath them, the explorers saw a world swarming with life. For years they studied, collected, catalogued. When they had learned all they could, they began to modify. They tinkered with the destinies of many species on land and in the ocean. But which of their experiments would succeed, they could not know for at least a million years.
They were patient, but they were not yet immortal. So much remained to do in this universe of a hundred billion suns, and other worlds were calling. So they set out once more into the abyss, knowing that they would never come this way again.
Nor was there any need. The servants they had left behind would do the rest.
On Earth the glaciers came and went, while above them the changeless Moon still carried its secret. With a yet slower rhythm than the polar ice, the tides of civilization ebbed and flowed across the Galaxy. Strange and beautiful and terrible empires rose and fell, and passed on their knowledge to their successors. Earth was not forgotten, but another visit would serve little purpose. It was one of a million silent worlds, few of which would ever speak.
And now, out among the stars, evolution was driving toward new goals. The first explorers of Earth had long since come to the limits of flesh and blood; as soon as their machines were better than their bodies, it was time to move. First their brains, and then their thoughts alone, they transferred into shining new homes of metal and plastic.
In these, they roamed among the stars. They no longer built spaceships. They were spaceships.
But the age of the Machine-entities swiftly passed. In their ceaseless experimenting, they had learned to store knowledge in the structure of space itself, and to preserve their thoughts for eternity in frozen lattices of light. They could become creatures of radiation, free at last from the tyranny of matter.
Into pure energy, therefore, they presently transformed themselves; and on a thousand worlds the empty shells they had discarded twitched for a while in a mindless dance of death, then crumbled into rust.
They were lords of the Galaxy, and beyond the reach of time. They could rove at will among the stars and sink like a subtle mist through the very interstices of space. But despite their godlike powers, they had not wholly forgotten their origin in the warm slime of a vanished sea.
And they still watched over the experiments their ancestors had started, so long ago.
52
Ignition
He had never expected to come there again, still less on so strange a mission. When he re-entered Discovery, the ship was far behind the fleeing Leonov and climbing ever more slowly up toward apojove, the high point of its orbit among the outer satellites. Many a captured comet, during the ages past, had swung around Jupiter in just such a long ellipse, waiting for the play of rival gravities to decide its ultimate fate.
All life had departed the familiar decks and corridors. The men and women who had briefly reawakened the ship had obeyed his warning; they might yet be safe - though that was still far from certain. But as the final minutes ticked away, he realized that those who controlled him could not always predict the outcome of their cosmic game.
They had not yet attained the stupefying boredom of absolute omnipotence; their experiments did not always succeed. Scattered across the Universe was the evidence of many failures - some so inconspicuous that they were already lost against the cosmic background, others so spectacular that they awed and baffled the astronomers of a thousand worlds. Only minutes remained now, before the outcome would be determined here; during those final minutes, he was once more alone with Hal.
In that earlier existence, they could communicate only through the clumsy medium of words, tapped on a keyboard or spoken into a microphone. Now their thoughts melded together at the speed of light:
"Do you read me, Hal?"
"Yes, Dave. But where are you? I cannot see you on any of my monitors."
"That is not important. I have new instructions for you. The infrared radiation from Jupiter on channels R23 through R35 is rising rapidly. I am going to give you a set of limiting values. As soon as they are reached, you must point the long-range antenna toward Earth and send the following message, as many times as possible -"
"But that will mean breaking contact with Leonov. I will no longer be able to relay my Jupiter observations, according to the program Dr Chandra has given me."
"Correct; but the situation has changed. Accept Priority Override Alpha. Here are the AE 35 Unit coordinates."
For a fraction of a microsecond, a random memory intruded into his flow of consciousness. How strange that he should once again be concerned with the AE 35 Antenna-pointing unit, whose reported malfunction had led Frank Poole to his death! This time, all the circuits lay open to his scrutiny, clear as the lines had once been on the palm of his hand. There could be no false alarms; nor was there any danger of them now.
"Instructions confirmed, Dave. It is good to be working with you again. Have I fulfilled my mission objectives properly?"
"Yes, Hal; you have done very well. Now there is one final message for you to transmit to Earth - and it will be the most important one you have ever sent."
"Please let me have it, Dave. But why did you say fina
l?" Why indeed? For whole milliseconds he pondered that question. And as he did so, he became aware of an emptiness he had not detected before. It had been there, but until now the barrage of new experiences and sensations had concealed it.
He knew something of their plans; they had need for him. Very well, he too had needs - perhaps, after a fashion, even emotions. Here was his last link with the world of men, and the life he had once known.
They had granted his earlier request; it would be interesting to test the extent of their benevolence - if, indeed, such a term was remotely applicable to them. And it should be easy for them to do what he was asking; they had already given ample evidence of their powers, when the no-longer-needed body of David Bowman had been casually destroyed - without putting an end to David Bowman himself.
They had heard him, of course; once again, there was the faint echo of an Olympian amusement. But he could detect neither acceptance nor denial.
"I am still waiting for your answer, Dave."
"Correction, Hal. I should have said: your last message for a long time. A very long time."
He was anticipating their action - trying, indeed, to force their hand. But, surely, they would understand that his request was not unreasonable; no conscious entity could survive ages of isolation without damage. Even if they would always be with him, he also needed someone - some companion - nearer his own level of existence.
The languages of mankind had many words to describe his gesture: cheek, effrontery, chutzpah. He recalled, with the perfect power of retrieval he now possessed, that a French general had once declaimed 'L'audace - toujours l'audace!' Perhaps it was a human characteristic that they appreciated, and even shared. He would soon know.