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.”

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.”