"Has there been other progress, though? If her original brain cannot be repaired-"

"We will come to the question of scientific progress in due course. For the moment, we judge it best for you to begin with something familiar. Your Servitor will show you around the solar system. Then it will be time for us to talk again."

"I don't want a stupid tour of the solar system. Last time, that made me feel worse. I'm interested in people, not planets.

I want to know what changes in the past fourteen million years might affect Ana's return."

Drake leaned forward, ready to argue. He was given no chance to do so. With one final wave of his hand, Ariel vanished; in the same moment, Drake was on board a ship.

Although Drake's frozen body remained in the cryowomb, the illusion that he had been reanimated was quite perfect.

He and Milton seemed to be traveling together in a real ship, its motion and progress constrained by the laws of dynamics and solar system geometry. He experienced real hunger and fatigue. After eighteen or twenty hours of subjective wakefulness, he would begin to yawn and feel the need for sleep.

It was the new solar system that seemed to lack reality.They had begun close to the Sun, where the familiar, steady beacon offered constancy and comfort. A few million years were nothing within the lifetime of a G-class star. It had looked down on Drake's birth, and it would probably look down unchanged on his final death, whenever that might be.

But unlike his birth, final death would not take place on Earth. Drake had stared from the ship's ports unmoved as they swept out past the hot cinder of Mercury and the garden world of Venus, with its blue-white atmosphere, placid seas, and sculpted continents. The transformation of the second planet might have been surprising and wonderful to those in Drake's own time, but it had been predicted since the era of Par Leon; the transformation had been well underway during his last resurrection.

His interest was focused on Earth long before they arrived there. The near-disastrous environmental runaway whose consequences he had seen on his last visit had lasted a few tens of thousands of years, but that was a mere blip on the long scroll of Earth's history. Ana had assured him that the correction was made. She had been sure that a similar mistake would never be allowed again.

So what would the home world have become, after so many millions of years of habitation and development?

As they drew closer, Drake looked and looked again. Something was wrong, but what was it?

The Earth-Moon doublet was growing in the ship's displays. The proportions were right, Earth's disk bulking more than ten times the area of its satellite; but the colors were peculiar. The smaller world was an angry red tinged with yellow smears. The larger one, instead of the familiar blue gray of Earth, gleamed a dull and mottled white that was naggingly suggestive and familiar.

He stared hard at that pale orb. The perspective shift took place within his mind.

"That big one's the Moon, the markings are changed but it has just the right color! But then where's Earth? Unless it was changed to look like the Moon, and the Moon. . . . Milton, I know this is a simulation. Does this represent reality, or are you playing tricks?"

The Servitor was at his side. It had spoken little since the journey began, but now the response was immediate. "It is not a simulation in the usual sense. It is a representation. By which I mean, although our whole journey is in derived reality, what you are seeing exactly matches the physical solar system, as it exists today."

"What happened to Earth?"

"It is easier to say why than what. As we told you, while you were in cryosleep another direction was three times taken by humanity. In two of those, technology was ignored. In the third, it took a leap that even now we do not understand.

The center of that new technology was Earth. One day, without warning, Earth collapsed to a fraction of its old size. Its surface closed. Its mass remained unchanged."

"It collapsed while it was still inhabited?"

"Correct."

Drake gazed in horror on the shrunken red- and yellow-smeared orb. "So everyone and everything on Earth was killed?"

"We think not. We believe that in some form everything on Earth has survived. Space within has been folded, and we believe that on the interior there was no collapse. We have no direct proof of this, since even after a million Earth years, no one has managed to penetrate the sphere that you see. It emits its own radiation, but it remains impermeable to everything from outside. Sometimes we see changes, occasionally there are what look like planet-wide lightning storms. Our best theory is that the sphere is constantly maintained by a single entity within it, a supermind combination of organic and inorganic intelligence.

"Of perhaps greater consequence to the rest of the solar system, at the time of Earth's collapse and closure the planet was the central repository of all solar system data banks. Their loss had a profound effect on human development-even on human sanity. Everyone was suddenly deprived of a vital group memory and a species cohesive force. The process of reconstruction was begun, from partial databases elsewhere, but it was slow, uncertain, and imperfect. After Earth's closure, every person in the Pluto cryowombs was revivified. Their memories assisted in the re-creation of the oldest historical records."

In Drake, that information produced a feeling of bitter irony. He had been wrong, totally and hopelessly wrong. He had argued, back in the quiet suburban house while the children were noisy upstairs and Tom Lambert sat pale-facedbefore him, that his own sacrifice was necessary. Without his help, Ana would never be resurrected. In fact, every long shot placed in Second Chance had paid off; even the "useless" ones, whom he had thought no one would bother to revive.

Instead of freezing himself he should have followed Tom Lambert's advice, and lived out his life. Better yet, instead of fleeing from Pluto he should have placed himself with Ana in the cryowombs there. They would have been resurrected together, to live the rest of their lives with each other.

Instead . . .

"I said, everyone was revivified," the Servitor continued. "That was of course not quite true. You alone, because I was armed with your specific instructions on your resurrection, were exempt."

"I am conscious now, even if I am not resurrected."

"True. We will come to that question in due course. But now, do you wish to go closer to Earth, for sentimental reasons?" The Servitor's wiry broom of sensors turned toward Drake. "Even were we not in derived reality, it would be quite safe to go to Earth. There has never been interference with an approaching ship, not even ones that have landed upon the impenetrable outer surface. They are simply ignored."

"That isn't Earth, no matter what you call it." Drake turned his back on the displays. "Take me away. There's nothing for me here."

Nothing for him, perhaps, anywhere in the solar system. That thought grew stronger as they flew outward from the Sun. It was not a problem of physical changes, which were substantial: Jupiter, glowing dully like a dying ember, flooding its satellites with abundant infrared radiation; the rings of Saturn, gone; Uranus like a miniature second sun illuminating the outer system; Neptune, vanished; Pluto basking in new heat to the point where nitrogen was a liquid on its surface and the cryowomb containing Drake and Ana-and only Drake and Ana-had been moved far out to a cooler location.

More important than all those were the changes that could not be seen. When Drake heard the words "fourteen million years" he had not at first thought through the implications. The news that everyone else in the cryowombs had been resurrected brought the understanding that he had become what he had once most feared: a living fossil, a creature from the remote past. Nothing he knew or was could interest anyone in this far future. Even the cryowombs themselves were an anachronism. Drake owed his own and Ana's continued existence in cryosleep only to Milton's literal, persistent, and conscientious mind.

And it was a mind. Drake could no longer think of the Servitor as a type of mechanical aide. Considered alone, Milton possessed mental powers that rivaled those of any human from Drake's time; considered as part of some still-undefined composite, the Servitor far surpassed human intelligence.

The ship flew on, beyond the solar system known to Drake. The Sun dwindled to a point. The constellations that filled the sky formed new and anonymous patterns. Fourteen million years was long enough for the slow movement of the "fixed" stars to have changed the face of the heavens.

"The Oort Cloud," Milton said, "was at your previous time of awakening undergoing its first exploration. It has changed a great deal. It is now a coalescence of a hundred million worldlets and interlocking intelligences. We do not propose to spend time there, since in your present form it is beyond your comprehension. Of greater interest to you is this."

The Servitor did not give any noticeable signal, but suddenly the ship vanished. Drake was hanging in open space before a lopsided and flattened disk, composed of thousands of bright sparks of light.

"We are looking at human star space," Milton went on. "This is the part of the galaxy that humanity and machines, in all their composite and complementary forms, have reached, developed, and colonized. Sol lies roughly at the center.

Although less than a millionth of our whole galaxy, human space includes eighty thousand suns. The perimeter grows continually, and asymmetrically, at a substantial fraction of light speed."

"Aliens?" The great disk seemed to be several hundred light-years across. Surely humans must have encountered fellow travelers through space and time. But the wire-broom head was shaking in dissent.

"Not yet. Life in abundance, yes. Even multicelled animal life, with nucleotide-base pair genetics and reproduction. But intelligence, no." Milton was calm and fatalistic. "The search continues. Someday the contact will surely take place."However, this is the end of our own brief outward journey. We must return now to the vicinity of your cryotank; there we face a more immediate problem."

Chapter 15.

Downloading.

Derived reality had at least one advantage over normal space and time: travel could be instantaneous. Milton might speak of "heading back" to the region of the cryotanks, but that was for Drake's convenience. There had been no physical travel. At one moment they were hovering far outside the solar system, contemplating the vast lopsided region of the spiral arm that was occupied by humans and their constructs; then they were again looking out over the Bay of Naples, where the dark clouds still hovered.

Ariel nodded to Drake, and began to speak.

"You have seen something of what humans and our inorganic companions can do and have done. Now it is time to talk of what we cannot do. Our limitations explain why we found it necessary to interact with you. The reason is simply stated: You cannot remain in the cryowomb for the indefinite future."

Drake had foreseen such a moment many millions of years ago, before he was ever frozen. Someday all his assets would become worthless. Who then would pay for the cost of continued cryotank operation?

He had hoped that the problem was solved when Par Leon informed him that activities involving the use of human time were the only ones with an implied cost. Now, apparently, the rules had changed again.

But he had learned not to accept negative answers. "Is there any way that I can be resurrected and earn credit? All that I know may be without value, but I would volunteer for any function that might allow Ana to remain in the cryowomb."

"You misunderstand. Maintenance of the cryowomb will shortly cease, but not because of any problems of maintenance. Each tank has its own long-lived power source, able to preserve a cryocorpse for an extremely long time without external support. Long enough, in fact, that we do not know its true lifetime, except that it would be measured in billions of years. The cryowomb with its cryotanks is already at the extreme edge of the Oort Cloud, and it is steadily drifting farther out to interstellar space. You and Ana have long been its only occupants. That, however, is not the reason why the cryowomb is increasingly irrelevant. The problem is far more basic. Look at this."

The window did not move, but the scene outside it changed. Drake found that he was staring through the glass at a naked body-his body, as it was stored in its cryotank.

"Again, we are in derived reality," Ariel said. "This time for a different reason. Watch closely."

Drake's cryocorpse did not move, but the flesh and bones gradually became translucent. Drake, staring uneasily at his own fading body, saw sparks of light appearing within it. They came randomly and infrequently, one every few seconds.

"One thing we cannot do," Ariel went on, "is control the probabilities that determine quantum processes. What you are seeing are changes to atoms or molecules within your own real body and brain, the result of quantum transitions.

To minimize such events, we long ago dropped the temperature in the cryotanks from the original liquid helium ambience, all the way to a fraction of a microkelvin. As a result, changes of atomic and molecular states became far less frequent. They did not, however, cease totally. Nor will they, no matter how close to absolute zero we take the temperature. Vacuum fluctuations guarantee it. There is no way to prevent or control such quantum effects."

Drake saw two more sparks of light, one in his cryocorpse's belly and one at the base of his brain. "You're telling me that I'm changing, even in the cryotank; and there's no way to stop it."

"You are changing-but very slowly. We are showing you quantum events at a greatly accelerated rate. Fifty years passed in real time, for each second shown on this display. However, your general conclusion is valid. There is no way to stop the changes. Left in a cryotank, at no matter how low a temperature, your body must inevitably be altered.

Quantum state transitions will eventually affect your memory and your mind."The scene outside the window flickered gray, then returned to show Naples and the clouded bay. Milton had been waiting silent at Ariel's side. Now the Servitor rolled closer to Drake. "You will appreciate my dilemma. On the one hand, your direct order was to leave you unchanged in the cryotank until such time as there was new learning that might affect our ability to reanimate Ana, as she was in your time. On the other hand, it proves impossible to leave you unchanged in the cryotank, since your very presence there inevitably produces change. Therefore I, whether I followed action or inaction, was unable to obey your command. We decided to interact with your cryocorpse, as we are doing now, to explore another option."

"You have one?"

"Of course: downloading. The conversion of the complete contents of your brain to electronic storage."

"You mean, become some sort of computer program? Forget it."

"Listen a little longer, before you reject. If you are downloaded, and at some future time you wish to function again in fleshly form, that can easily be done. It calls only for the storage, along with your brain's contents, of somatic information. Such information is contained in the nucleus of every cell of your body. From your genetic blueprint, your new body can be grown. You would then be uploaded to the new brain from electronic storage."

"That can really be done?"

"Can be, and has been, a billion times. It is the standard procedure for establishing research teams on the planets of other stars."

"But isn't electronic storage just as subject to change as storage in my frozen brain? It's not immune to quantum processes. You just said there's no way to prevent or control quantum effects."

"Quite true; there is, however, a way to compensate for them. It is done through simple redundancy and comparison.

After we perform an electronic download from a brain, we create three identical copies. Each of those copies, as you observed, is subject to statistical change because of quantum effects. Periodically, we therefore perform a complete bit-by-bit comparison of all three copies. Occasionally, one copy will show a difference from the other two. We attribute that change to a quantum fluctuation, and we correct the variant copy at that point to agree with the other two. It is, of course, mathematically possible for two quantum changes to take place in the stored brain map, on the same element of information and at the same time. That would produce three different versions, and there would be no way to decide which one was true to the original.

Fortunately, the probability of such an event is so small as to be of no concern."

"I assume you've done all this to somebody?"

"More than that." The Servitor lacked the means for a physical expression of embarrassment, but the voice slowed and changed. "For the past fourteen million years, I have been applying the technique to you. As soon as the technology permitted a complete download, I performed one of you. Since it was held in a totally dormant condition, and since you were still in the cryowomb, I felt that I had not violated your instructions."

"You mean I've been downloaded already, without ever being asked? You've got a nerve."

"What other option did I have? You ordered me to leave you unchanged in the cryotank, but leaving you there would itself change you. The only way to guarantee that you remained unaltered was to monitor changes in your frozen brain through triple redundancy checks on the downloaded versions, and then correct you appropriately in the cryotank. I can vouch for the effectiveness and reliability of the method, since it is close to the one that I employ on my own composite."

"How do you know that you don't change, Milton? You might be different than you were yesterday."

"And you may not be the Drake Merlin who went into cryosleep, or the same person who met with Trismon Sorel. No one can prove that they are what they were. I can say only this: uploading represents your only chance of remaining unchanged into the far future."

"What about my body?"

"Your original body?" Ariel answered the question. "It becomes of no interest. Its performance, without electronic update, must gradually degrade. We would propose to leave it in the cryowomb."

"My body is of no interest?""Certainly. You were disposing of your body, cell by cell, every hour and minute that you were alive. Ask yourself, where is the body that you wore when you were five years old? Where is the body in which you first met your beloved Anastasia? They are gone, stranded far back upon the banks and shoals of time. It is only your mind, the essential spirit of Drake Merlin, that floats free toward the uncharted ocean of the future."

"Ariel, I don't know you at all; but if you were back in my own time I'd be worried. I once had a teacher who told me, 'Watch out when the talk gets molto legato' -very smooth. Too smooth, and too flowery. What are you leaving out?"

"You had a suspicious-minded teacher, Drake Merlin. Very well. There are several other things that should be said.

The first concerns Ana. Her full genome is already in electronic storage, so future cloning would be trivial. But there is no 'complete Ana' available for electronic download. Her brain can yield no more than a random chaos of disconnected elements. Their transference would be pointless."

"If I move to electronic form, whatever remains of Ana must move with me."

"I suspected that would be your reply. But it is really quite illogical. If her personality could ever be restored, the existence of primitive brain residues will not be a factor."

"So you say-now. But I've heard too often that nothing can be done for Ana. Both of us get downloaded, or neither one."

"We hear you." Ariel nodded in resignation. "Milton?"

"It will be done."

The Servitor vanished. Ariel looked more pensive. "We have debated the wisdom of mentioning this next item," he said. "We do not wish to arouse in you hopeless and unrealizable expectations. In fact, had it not been necessary to contact you concerning your removal from the cryowomb, we would have remained silent.

But having gone so far, I will continue. Your goal, for fourteen million years, has been to restore Ana to the form that you knew-not merely her body, but her whole personality."

"And I've been told, over and over, that it's quite impossible. Are you telling me that it isn't?"

"It is impossible, today and for the known future. The question is, will it always be impossible? What I can tell you is this: whether Ana's restoration is feasible or infeasible, in principle, in the very long-term future, does not depend on your actions or on my actions. It depends on the overall nature of the universe itself. And it is because our perceptions of that future have been changing that I am willing to discuss it with you now."

"You've lost me. Totally."

"As I was afraid I might. It is not easy to explain in a way that you will understand, or to know where to start so as to maximize the probability of your comprehension. But let us begin with a question: Do you know the difference between an open universe and a closed universe?"

"I know what the terms used to mean, at the time that I was frozen."

"The notions have not changed, except possibly in minor details. The more distant galaxies recede from us, and more distant galaxies recede faster."

"Even in my time, most people knew that."

"Then the definitions with which you are familiar still apply. In an open universe, the galaxies go on receding from each other, forever. In a dosed universe, they one day reverse their motion and begin to approach each other. In a closed universe, the end point for that approach is a collapse to a point of infinite density, pressure, and temperature.

Is that clear?"

"Clear, and totally irrelevant. I'm interested in restoring Ana, not in discussing cosmology."