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 final?' 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.

'Hal! Look at the signal on infrared channels 30, 29, 28 – it will be very soon now – the peak is moving toward the short wave.'

'I am informing Dr Chandra that there will be a break in my data transmission. Activating AE 35 unit. Reorientating long-range antenna... lock confirmed on Beacon Terra One. Message commences: ALL THESE WORLDS...'

They had indeed left it to the last minute – or perhaps the calculations had, after all, been superbly accurate. There was time for barely a hundred repetitions of the eleven words when the hammer blow of pure heat smashed into the ship.

Held there by curiosity, and a growing fear of the long loneliness that lay before him, that which had once been David Bowman, Commander of United States Spacecraft Discovery, watched as the hull boiled stubbornly away. For a long time, the ship retained its approximate shape; then the bearings of the carousel seized up, releasing instantly the stored momentum of the huge, spinning flywheel. In a soundless detonation, the incandescent fragments went their myriad separate ways.