"But he is the type for an academic job. If we can arrange to have a large university offer him a chair in physics, I think he would take it gladly. There would be enough nonsensitive areas to keep him occupied; we would be able to keep him in close view; and it would be a natural development. The Russians might not start scratching their heads. What do you think?"

Brand nodded. "It's an idea. Even sounds good. I'll put it up to the chief."

They stepped into the elevator and Brand allowed himself to wonder about it all. What an ending to what had started with one letter of a name.

Marshall Sebatinsky could hardly talk. He said to his wife, "I swear I don't see how this happened. I wouldn't have thought they knew me from a meson detector. -Good Lord, Sophie, a.s.sociate Professor of Physics at Princeton. Think of it."

Sophie said, "Do you suppose it was your talk at the A.P.S. meetings?" "1 don't see how. It was a thoroughly uninspired paper once everyone in the division was done hacking at it." He snapped his fingers. "It must have been Princeton that was investigating me. That's it. You know all those forms I've been filling out in the last six months; those interviews they wouldn't explain. Honestly, 1 was beginning to think I was under suspicion as a subversive. -It was Princeton investigating me. They're thorough." "Maybe it was your name," said Sophie. "I mean the change." "Watch me now. My professional life will be my own finally. I'll make my mark. Once I have a chance to do my work without-" He stopped and turned to look at his wife. "My name! You mean the 5." "You didn't get the offer till after you changed your name, did you?" "Not till long after. No, that part's just coincidence. I've told you before Sophie, it was just a case of throwing out fifty dollars to please you. Lord, what a fool I've felt all these months insisting on that stupid 5."

Sophie was instantly on the defensive. "I didn't make you do it, Marshall. I suggested it but I didn't nag you about it. Don't say I did. Besides, it did turn out well. I'm sure it was the name that did this." Sebatinsky smiled indulgently. "Now that's superst.i.tion." "I don't care what you call it, but you're not changing your name back." "Well, no, I suppose not. I've had so much trouble getting them to spell my name with an S, that the thought of making everyone move back is more than I want to face. Maybe I ought to change my name to Jones, eh?" He laughed almost hysterically.

But Sophie didn't. "You leave it alone."

"Oh, all right, I'm just joking. -Tell you what. I'll step down to that old fellow's place one of these days and tell him everything worked out and slip him another tenner. Will that satisfy you?"

He was exuberant enough to do so the next week. He a.s.sumed no disguise this time. He wore his gla.s.ses and his ordinary suit and was minus a hat.

He was even humming as he approached the store front and stepped to one side to allow a weary, sour-faced woman to maneuver her twin baby carriage past.

He put his hand on the door handle and his thumb on the iron latch. The latch didn't give to his thumb's downward pressure. The door was locked.

The dusty, dim card with "Numerologist" on it was gone, now that he looked. Another sign, printed and beginning to yellow and curl with the sunlight, said "To let."

Sebatinslcy shrugged. That was that. He had tried to do the right thing.

Haround, happily divested of corporeal excrescence, capered happily and his energy vortices glowed a dim purple over cubic hypermiles. He said, "Have I won? Have I won?"

Mestack was withdrawn, his vortices almost a sphere of light in hyper-s.p.a.ce. "1 haven't calculated it yet."

"Well, go ahead. You won't change the results any by taking a long time. -Wowf, it's a relief to get back into clean energy. It took me a microcycle of time as a corporeal body; a nearly used-up one, too. But it was worth it to show you."

Mestack said, "All right, I admit you stopped a nuclear war on the planet."

"Is that or is that not a Cla.s.s A effect?"

"It is a Cla.s.s A effect. Of course it is."

"All right. Now check and see if I didn't get that Cla.s.s A effect with a Ckss F stimulus. I changed one letter of one name."

"What?"

"Oh, never mind. It's all there. I've worked it out for you."

Mestack said reluctantly, "I yield. A Cla.s.s F stimulus."

"Then I win. Admit it."

"Neither one of us will win when the Watchman gets a look at this."

Haround, who had been an elderly numerologist on Earth and was still somewhat unsettled with relief at no longer being one, said, "You weren't worried about that when you made the bet."

"I didn't think you'd be fool enough to go through with it."

"Heat-waste! Besides, why worry? The Watchman will never detect a Ckss F stimulus."

"Maybe not, but he'll detect a Cla.s.s A effect. Those corporeals will still be around after a dozen mkrocycles. The Watchman will notice that."

"The trouble with you, Mestack, is that you don't want to pay off. You're stalling."

"I'll pay. But just wait till the Watchman finds out we've been working on an una.s.signed problem and made an unallowed-for change. Of course, if we-" He paused.

Haround said, "All right, we'll change it back. He'll never know."

There was a crafty glow to Mestack's brightening energy pattern. "You'll need another Cla.s.s F stimulus if you expect him not to notice."

Haround hesitated. "I can do it."

"I doubt it."

"I could."

"Would you be willing to bet on that, too?" Jubilation was creeping into Mestack's radiations.

"Sure," said the goaded Haround. "I'll put those corporeals right back where they were and the Watchman will never know the difference."

Mestack followed through his advantage. "Suspend the first bet, then. Triple the stakes on the second."

The mounting eagerness of the gamble caught at Haround, too. "All right, I'm game. Triple the stakes."

"Done, then!"

"Done."

The Last Question

The last question was asked for the first time, half in jest, on May 21, 2061, at a time when humanity first stepped into the light. The question came about as a result of a five-dollar bet over highb.a.l.l.s, and it happened this way: Alexander Adell and Bertram Lupov were two of the faithful attendants of Multivac. As well as any human beings could, they knew what lay behind the cold, clicking, flashing face-miles and miles of face-of that giant computer. They had at least a vague notion of the general plan of relays and circuits that had long since grown past the point where any single human could possibly have a firm grasp of the whole.

Multivac was self-adjusting and self-correcting. It had to be, for nothing human could adjust and correct it quickly enough or even adequately enough. -So Adell and Lupov attended the monstrous giant only lightly and superficially, yet as well as any men could. They fed it data, adjusted questions to its needs and translated the answers that were issued. Certainly they, and all others like them, were fully ent.i.tled to share in the glory that was Multivac's.

For decades, Multivac had helped design the ships and plot the trajectories that enabled man to reach the Moon, Mars, and Venus, but past that, Earth's poor resources could not support the ships. Too much energy was needed for the long trips. Earth exploited its coal and uranium with increasing efficiency, but there was only so much of both.

But slowly Multivac learned enough to answer deeper questions more fundamentally, and on May 14, 2061, what had been theory, became fact.

Copyright 1956 by Columbia Publications, Inc.

The energy of the sun was stored, converted, and utilized directly on a planet-wide scale. All Earth turned off its burning coal, its fissioning uranium, and flipped the switch that connected all of it to a small station, one mile in diameter, circling the Earth at half the distance of the Moon. All Earth ran by invisible beams of sunpower.

Seven days had not sufficed to dim the glory of it and Adell and Lupov finally managed to escape from the public function, and to meet in quiet where no one would think of looking for them, in the deserted underground chambers, where portions of the mighty buried body of Multivac showed. Unattended, idling, sorting data with contented lazy clickings, Multivac, too, had earned its vacation and the boys appreciated that. They had no intention, originally, of disturbing it.

They had brought a bottle with them, and their only concern at the moment was to relax in the company of each other and the bottle.

"It's amazing when you think of it," said Adell. His broad face had lines of weariness in it, and he stirred his drink slowly with a gla.s.s rod, watching the cubes of ice slur clumsily about. "All the energy we can possibly ever use for free. Enough energy, if we wanted to draw on it, to melt all Earth into a big drop of impure liquid iron, and still never miss the energy so used. All the energy we could ever use, forever and forever and forever."

Lupov c.o.c.ked his head sidways. He had a trick of doing that when he wanted to be contrary, and he wanted to be contrary now, partly because he had had to carry the ice and gla.s.sware. "Not forever," he said.

"Oh, h.e.l.l, just about forever. Till the sun runs down, Bert."

"That's not forever."

"All right, then. Billions and billions of years. Twenty billion, maybe. Are you satisfied?"

Lupov put his fingers through his thinning hair as though to rea.s.sure himself that some was still left and sipped gently at his own drink. "Twenty billion years isn't forever."

"Well, it will last our time, won't it?"

"So would the coal and uranium."

"All right, but now we can hook up each individual s.p.a.ceship to the Solar Station, and it can go to Pluto and back a million times without ever worrying about fuel. You can't do that on coal and uranium. Ask Multivac, if you don't believe me."

"1 don't have to ask Multivac. 1 know that."

"Then stop running down what Multivac's done for us," said Adell, blazing up. "It did all right."

"Who says it didn't? What I say is that a sun won't last forever. That's all I'm saying. We're safe for twenty billion years, but then what?" Lupov pointed a slightly shaky finger at the other. "And don't say we'll switch to another sun."

There was silence for a while. Adell put his gla.s.s to his lips only occasionally, and Lupov's eyes slowly closed. They rested.

Then Lupov's eyes snapped open. "You're thinking we'll switch to another sun when ours is done, aren't you?"

"I'm not thinking."

"Sure you are. You're weak on logic, that's the trouble with you. You're like the guy in the story who was caught in a sudden shower and who ran to a grove of trees and got under one. He wasn't worried, you see, because he figured when one tree got wet through, he would just get under another one."

"I get it," said Adell. "Don't shout. When the sun is done, the other stars will be gone, too."

"Darn right they will," muttered Lupov. "It all had a beginning in the original cosmic explosion, whatever that was, and it'll all have an end when all the stars run down. Some run down faster than others. h.e.l.l, the giants won't last a hundred million years. The sun will last twenty billion years and maybe the dwarfs will last a hundred billion for all the good they are. But just give us a trillion years and everything will be dark. Entropy has to increase to maximum, that's all."

"I know all about entropy," said Adell, standing on his dignity.

"The h.e.l.l you do."

"I know as much as you do."

"Then you know everything's got to run down someday."

"AU right. Who says they won't?"

"You did, you poor sap. You said we had all the energy we needed, forever. You said 'forever.' "

It was Adell's turn to be contrary. "Maybe we can build things up again someday," he said.

"Never."

"Why not? Someday."

"Never."

"Ask Multivac."

"You ask Multivac. I dare you. Five dollars says it can't be done."

Adell was just drunk enough to try, just sober enough to be able to phrase the necessary symbols and operations into a question which, in words, might have corresponded to this: Will mankind one day without the net expenditure of energy be able to restore the sun to its full youthfulness even after it had died of old age?

Or maybe it could be put more simply like this: How can the net amount of entropy of the universe be ma.s.sively decreased?

Multivac fell dead and silent. The slow flashing of lights ceased, the distant sounds of clicking relays ended.

Then, just as the frightened technicians felt they could hold their breath no longer, there was a sudden springing to life of the teletype attached to that portion of Multivac. Five words were printed: insufficient data for MEANINGFUL ANSWER.

"No bet," whispered Lupov. They left hurriedly. By next morning, the two, plagued with throbbing head and cottony mouth, had forgotten the incident.

|errodd, Jerrodine, and Jerrodette I and II watched the starry picture in the visiplate change as the pa.s.sage through hypers.p.a.ce was completed in its non-time lapse. At once, the even powdering of stars gave way to the predominance of a single bright marble-disk, centered.

"That's X-23," said Jerrodd confidently. His thin hands clamped tightly behind his back and the knuckles whitened.

The little Jerrodettes, both girls, had experienced the hypers.p.a.ce pa.s.sage for the first time in their lives and were self-conscious over the momentary sensation of inside-outness. They buried their giggles and chased one another wildly about their mother, screaming, "We've reached X-23-we've reached X-23-we've-"

"Quiet, children," said Jerrodine sharply. "Are you sure, Jerrodd?"

"What is there to be but sure?" asked Jerrodd, glancing up at the bulge of featureless metal just under the ceiling. It ran the length of the room, disappearing through the wall at either end. It was as long as the ship.

Jerrodd scarcely knew a thing about the thick rod of metal except that it was called a Microvac, that one asked it questions if one wished; that if one did not it still had its task of guiding the ship to a preordered destination; of feeding on energies from the various Sub-galactic Power Stations; of computing the equations for the hyperspatial jumps.

Jerrodd and his family had only to wait and live in the comfortable residence quarters of the ship.

Someone had once told Jerrodd that the "ac" at the end of "Microvac" stood for "a.n.a.log computer" in ancient English, but he was on the edge of forgetting even that.

Jerrodine's eyes were moist as she watched the visiplate. "I can't help it. I feel funny about leaving Earth."

"Why, for Pete's sake?" demanded Jerrodd. "We had nothing there. We'll have everything on X-23. You won't be alone. You won't be a pioneer. There are over a million people on the planet already. Good Lord, our greatgrandchildren will be looking for new worlds because X-23 will be overcrowded." Then, after a reflective pause, "I tell you, it's a lucky thing the computers worked out interstellar travel the way the race is growing."

"I know, I know," said Jerrodine miserably.

Jerrodette I said promptly, "Our Microvac is the best Microvac in the world."