Nightfall

by Isaac Asimov

  “That’s how it begins. You get to like it little by little, you develop jolly associations between one particular place and drinking, then after a while you experiment with having a drink or two somewhere else, and then a drink or three—”

  “Theremon! You sound like an Apostle of Flame! They think drinking’s evil too, don’t they?”

  “They think everything’s evil. But drinking certainly is. That’s what’s so wonderful about it, eh, my friend?” Theremon laughed. “You were telling me about Athor.”

  “Yes. The really comical thing. Do you remember that wild notion you had that some unknown factor might be pushing Kalgash away from the orbit we’d expect it to have?”

  “The invisible giant, yes. The dragon huffing and puffing in the sky.”

  “Well, Athor took exactly the same position!”

  “He thinks there’s a dragon in the sky?”

  Beenay guffawed. “Don’t be silly. But some sort of unknown factor, yes. A dark sun, maybe, or some other world that’s located at a position that’s impossible for us to see, but which nevertheless is exerting gravitational force on Kalgash—”

  “Isn’t that all a little on the fantastic side?” Theremon asked.

  “Of course it is. But Athor reminded me of the old philosophical chestnut of Thargola’s Sword. Which we use—metaphorically, I mean—to smite the more complex premise when we’re trying to decide between two hypotheses. It’s simpler to go looking for a dark sun than it is to have to produce an entirely new Theory of Universal Gravitation. And therefore—”

  “A dark sun? But isn’t that a contradiction in terms? A sun is a source of light. If it’s dark, how can it be a sun?”

  “That’s just one of the possibilities Athor tossed at us. It isn’t necessarily one that he takes seriously. What we’ve been doing, these last few days, is throwing around all kinds of astronomical notions, hoping that one of them will make enough sense so that we can begin to put together an explanation for— Look, there’s Sheerin.” Beenay waved at the rotund psychologist, who had just entered the club. “Sheerin! Sheerin! Come out here and have a drink with us, will you?”

  Sheerin stepped carefully through the narrow doorway.

  “So you’ve taken up some new vices, have you, Beenay?”

  “Not very many. But Theremon’s exposed me to the Tano Special, and I’m afraid I’ve caught a taste for it. You know Theremon, don’t you? He writes the column in the Chronicle.”

  “I don’t think we’ve actually met,” Sheerin said. He offered his hand. “I’ve certainly heard a lot about you, though. I’m Raissta 717’s uncle.”

  “The psych professor,” Theremon said. “You’ve been at the Jonglor Exposition, right?”

  Sheerin looked startled. “You keep up with everything, don’t you?”

  “I try to.” The waiter was back. “What can we get you? Tano Special?”

  “Too strong for me,” Sheerin said. “And a little too sweet. —Do you have neltigir, by any chance?”

  “The Jonglorian brandy? I’m not sure. How do you want it, if I can find some?”

  “Straight,” said Sheerin. “Please.” To Theremon and Beenay he said, “I developed a liking for it while I was up north. The food’s awful in Jonglor, but at least they can distill a decent brandy.”

  “I hear they’ve had a lot of trouble at the Exposition,” Theremon said. “Some problem in their amusement park—a ride through Darkness that was driving people crazy, literally driving them out of their heads—”

  “The Tunnel of Mystery, yes. That was the reason I was there: as a consultant called in by the city and its lawyers for an opinion.”

  Theremon sat forward. “Is it true that people were dying of shock in that tunnel, and they kept it open anyway?”

  “Everyone’s been asking me that,” replied Sheerin. “There were a few deaths, yes. But they didn’t seem to harm the ride’s popularity. People insisted on taking the risk anyway. And a lot of them came out very badly deranged. I took a ride in the Tunnel of Mystery myself,” he said, shuddering. “Well, they’ve shut the thing down, now. I told them it was either that or fork over millions of credits in liability suits, that it was absurd to expect people to be able to tolerate Darkness at that level of intensity. They saw the logic of that.”

  “We do have some neltigir, sir,” the waiter broke in, putting a glass of somber brownish brandy on the table in front of Sheerin. “Just one bottle, so you’d better go easy.” The psychologist nodded and scooped up his drink, downing about half of it before the waiter had left the table.

  “Sir, I said—”

  Sheerin smiled at him. “I heard what you said. I’ll take it easier after this one.” He turned to Beenay. “I understand there was some excitement at the Observatory while I was up north. Liliath told me. But she wasn’t too clear on what was going on. Some new theory, I think she said—”

  Grinning, Beenay said, “Theremon and I were just talking about that. Not a new theory, no. A challenge to an established one. I was running some calculations on Kalgash’s orbit, and—”

  Sheerin listened to the story with increasing astonishment. “The Theory of Universal Gravitation’s invalid?” he cried when Beenay was halfway through. “Good lord, man! Does that mean that if I put my glass down, it’s likely to go floating up into the sky? I’d better finish off my neltigir first, then!” And he did.

  Beenay laughed. “The theory’s still on the books. What we’re trying to do—what Athor is trying to do; he’s been spearheading the work, and it’s amazing to watch him go at it—is to come up with a mathematical explanation for why our figures don’t come out the way we think they ought to.”

  “Massaging the data, I think it’s called,” Theremon added.

  “Sounds suspicious to me,” Sheerin said. “You don’t like the result, so you rearrange your findings, is that it, Beenay? Make everything fit, by hook or by crook?”

  “Well, not exactly—”

  “Admit it! Admit it!” Sheerin roared with laughter. “Waiter! Another neltigir! And one more Tano Special for my unethical young friend here! —Theremon, can I get you a drink too?”

  “Please.”

  Sheerin said in the same broad tone as before, “This is all very disillusioning, Beenay. I thought it was only us psychologists who made the data fit the theories and called the result ‘science.’ Seems more like something the Apostles of Flame might do!”

  “Sheerin! Cut it out!”

  “The Apostles claim to be scientists too,” Theremon put in. Beenay and Sheerin turned to look at him. “Last week just before the rain started I had an interview with one of their big people,” he went on. “I had hoped to see Mondior, but I got a certain Folimun 66 instead, their public-relations man, very slick, very bright, very personable. He spent half an hour explaining to me that the Apostles have reliable scientific proof that next year on the nineteenth of Theptar the suns are going to go out and we’ll all be plunged into Darkness and everyone will go insane.”

  “The whole world turned into one big Tunnel of Mystery, is that it?” Sheerin said jovially. “We won’t have enough mental hospitals to hold the entire population, you know. Or enough psychiatrists to treat them. Besides, the psychiatrists will be crazy too.”

  “Aren’t they already?” Beenay asked.

  “Good point,” said Sheerin.

  “The madness isn’t the worst of it,” Theremon said. “According to Folimun, the sky will be filled with something called Stars that will shoot fire down upon us and set everything ablaze. And there we’ll be, a world full of gibbering maniacs, wandering around in cities that are burning down around our ears. Thank heaven it’s nothing but Mondior’s bad dream.”

  “But what if it isn’t?” Sheerin said, suddenly sobering. His round face grew long and thoughtful. “What if there’s something to it?”

  “What an appalling notion,” Beenay said. “I think it calls for another drink.”

  “You haven’t fin
ished the one you’ve got,” Sheerin reminded the young astronomer.

  “Well, what of it? It still calls for another one afterward. Waiter! Waiter!”

  [14]

  Athor 77 felt fatigue sweeping through him in shimmering waves. The Observatory director had lost all track of time. Had he really been at his desk sixteen straight hours? And yesterday the same. And the day before—

  That was what Nyilda claimed, anyway. He had spoken to her just a little while before. His wife’s face on the screen had been tense, drawn, unmistakably worried.

  “Won’t you come home for a rest, Athor? You’ve been going at it practically around the clock.”

  “Have I?”

  “You aren’t a young man, you know.”

  “I’m not a senile one, either, Nyilda. And this is exhilarating work. After a decade of initialing budget reports and reading other people’s research papers I’m finally doing some real work again. I love it.”

  She looked even more troubled. “But you don’t need to be doing research at your age. Your reputation is secure, Athor!”

  “Ah, is it?”

  “Your name will be famous in the history of astronomy forever.”

  “Or infamous,” he said balefully.

  “Athor, I don’t understand what you—”

  “Let me be, Nyilda. I’m not going to keel over at my desk, believe me. I feel rejuvenated by what I’m doing here. And it’s work that only I can do. If that sounds pigheaded, so be it, but it’s absolutely essential that I—”

  She sighed. “Yes, of course. But don’t overdo it, Athor. That’s all I ask.”

  Was he overdoing it? he wondered now. Yes, yes, of course he was. There wasn’t any other way. You couldn’t dabble in these matters. You had to throw yourself wholeheartedly into them. When he was working out Universal Gravitation he had worked sixteen-, eighteen-, twenty-hour days for weeks on end, sleeping only when sleep became unavoidable, snatching brief naps and awakening ready and eager for work, with his mind still bubbling with the equations he had left unfinished a little while before.

  But he had been only thirty-five or so, then. He was nearly seventy now. There was no denying the inroads of age. His head ached, his throat was dry, there was a nasty pounding in his chest. Despite the warmth of his office his fingertips were chilly with weariness. His knees were throbbing. Every part of his body protested the strain he had been putting on it.

  Just a little while longer today, he promised himself, and then I’ll go home.

  Just a little while longer.

  Postulate Eight—

  “Sir?”

  “What is it?” he asked.

  But his voice must have turned the question into some sort of fierce snarl, for when he glanced around he saw young Yimot standing in the doorway doing a bizarre series of wild twitches and convulsions, as though he were dancing on hot embers. There was terror in the boy’s eyes. Of course Yimot always seemed intimidated by the Observatory director—everybody around here was, not just graduate students, and Athor was used to it. Athor was awesome and he knew it. But this went beyond the ordinary. Yimot was gazing at him in undisguised fear mingled with what seemed like astonishment.

  Yimot struggled visibly to find his voice and said huskily, “The calculations you wanted, sir—”

  “Oh. Yes. Yes. Here, give me.”

  Athor’s hand was trembling violently as he reached for the printouts Yimot had brought him. Both of them stared at it, aghast. The long bony fingers were pale as death and they were quivering with a vehemence that not even Yimot, famed for his remarkable nervous reactions, could have equaled. Athor willed his hand to be still, but it would not. He might just as well have been willing Onos to spin backward across the sky.

  With an effort he snatched the papers from Yimot and slapped them down on the desk.

  Yimot said, “If there’s anything I can get you, sir—”

  “Medication, you mean? How dare you suggest—”

  “I just meant something to eat, or maybe a cold drink,” Yimot said in a barely audible whisper. He backed slowly away as if expecting Athor to growl and leap for his throat.

  “Ah. Ah. I see. No, I’m fine, Yimot. Fine!”

  “Yes, sir.”

  The student went out. Athor closed his eyes a moment, took three or four deep breaths, struggled to calm himself. He was near the end of his task, of that he was sure. These figures that he had asked Yimot to work out for him were almost certainly the last confirmation he needed. But the question now was whether the work was going to finish him before he finished the work.

  He looked at Yimot’s numbers.

  Three screens sat before him on his desk. On the left-hand one was the orbit of Kalgash as calculated according to conventional reckoning under the Theory of Universal Gravitation, outlined in blazing red. On the right-hand screen, in fiery yellow, was the revised orbit that Beenay had produced, using the new university computer and the most recent observations of Kalgash’s actual position. The middle screen carried both orbits plotted one over the other. In the past five days Athor had produced seven different postulates to account for the deviation between the theoretical orbit and the observed one, and he could call up any of those seven postulates on the middle screen with a single key-stroke.

  The trouble was that all seven of them were nonsense, and he knew it. Each one had a fatal flaw at its heart—an assumption that was there not because the calculations justified it, but only because the situation called for some such sort of special assumption in order to make the numbers turn out the right way. Nothing was provable, nothing was confirmable. It was as though in each case he had simply decreed, at some point in the chain of logic, that a fairy godmother would step in and adjust the gravitational interactions to account for the deviation. In truth that was precisely what Athor knew he needed to find. But it had to be a real fairy godmother.

  Postulate Eight, now—

  He began keying in Yimot’s calculations. Several times his trembling fingers betrayed him and he made an error; but his mind was still sharp enough to tell him instantly that he had hit the wrong key, and he backed up and repaired the damage each time. Twice, as he worked, he nearly blacked out from the intensity of his effort. But he forced himself to go on.

  You are the only person in the world who can possibly do this, he told himself as he worked. And so you must.

  It sounded foolish to him, and madly egocentric, and perhaps a little insane. It probably wasn’t even true. But at this stage in his exhaustion he couldn’t allow himself to consider any other premise but that of his own indispensability. All the basic concepts of this project were held in his mind, and his mind alone. He had to push himself onward until he had closed the last link in the chain. Until—

  There.

  The last of Yimot’s numbers went into the computer.

  Athor hit the key that brought the two orbits up into view simultaneously on the middle screen, and hit the key that integrated the new number with the existing patterns.

  The brilliant red ellipse that was the original theoretical orbit wavered and shifted, and suddenly it was gone. So was the yellow one of the observed orbit. Now there was only a single line on the screen, a deep, intense orange, the two orbital simulations overlapping to the last decimal place.

  Athor gasped. For a long moment he studied the screen, and then he closed his eyes again and bowed his head against the edge of the desk. The orange ellipse blazed like a ring of flame against his closed eyelids.

  He felt a curious sense of exultation mixed with dismay.

  He had his answer, now; he had a hypothesis that he was certain would stand up to the closest scrutiny. The Theory of Universal Gravitation was valid after all: the epochal chain of reasoning on which his fame was based would not be overthrown.

  But at the same time he knew now that the model of the solar system with which he was so familiar was in fact erroneous. The unknown factor for which they had sought, the invisible giant,
the dragon in the sky, was real. Athor found that profoundly upsetting, even if it had rescued his famous theory. He had thought for years that he fully understood the rhythm of the heavens, and now it was clear to him that his knowledge had been incomplete, that a great strangeness existed in the midst of the known universe, that things were not as he had always believed them to be. It was hard, at his age, to swallow that.

  After a time Athor looked up. Nothing had changed on the screen. He punched in a few interrogative equations, and still nothing changed. He saw one orbit, not two.

  Very well, he told himself. So the universe is not quite as you thought it was. You’d better rearrange your beliefs, then. Because you certainly can’t rearrange the universe.

  “Yimot!” he called. “Faro! Beenay! All of you!”

  Roly-poly little Faro was the first through the door, with beanpole Yimot just behind him, and then the rest of the Astronomy Department, Beenay, Thilanda, Klet, Simbron, and some others. They clustered just inside the entrance to his office. Athor saw by the expression of shock on their faces that he must be a frightful sight indeed, no doubt wild and haggard, his white hair standing out in all directions, his face pale, his whole appearance that of an old man right on the edge of collapse.

  It was important to defuse their fears right away. This was no moment for melodrama.

  Quietly he said, “Yes, I’m very tired and I know it. And I probably look like some demon out of the nether realms. But I’ve got something here that looks like it works.”

  “The gravitational lens idea?” Beenay said.

  “The gravitational lens is a completely hopeless concept,” Athor said frostily. “The same with the burned-out sun, the fold in space, the zone of negative mass, and the other fantastical notions we’ve been playing with all week. They’re all very pretty ideas but they don’t stand up to hard scrutiny. There is one that does, though.”

  He watched their eyes widen.

  Turning to the screen, he began once again to set up the numbers of Postulate Eight. His weariness dropped away as he worked: he struck no wrong keys this time, he felt no aches and pains. He had moved into a realm beyond fatigue.