Nightfall

by Isaac Asimov

  No. No. No. No. Idiocy! Claptrap! Hysterical folly!

  There was more. “Again and again, when the Year of Godliness has ended, the gods have discovered that we’re still wicked and sinful, and so they have destroyed the world by sending down heavenly flames.… So say the Apostles, anyway.”

  No! No!

  “Beenay?” Siferra said. “Are you all right?”

  “Just thinking,” he told her. “By Darkness, it’s true! You’d give the Apostles complete confirmation!”

  “Not necessarily. It would still be possible for people who are capable of thinking clearly to reject Mondior’s ideas. The destruction of Thombo by fire—even the repeated destruction of Thombo at apparently regular intervals of approximately two thousand years—doesn’t in any way prove that the whole world was destroyed by fire. Or that some such great fire must inevitably come again. Why should the past necessarily be recapitulated in the future? But people who are capable of thinking clearly are in a minority, of course. The rest of them will be swayed by Mondior’s use of my findings and go into an immediate panic. You know, don’t you, that the Apostles claim the next great world-destroying fire is due to strike us next year?”

  “Yes,” Beenay said hoarsely. “Theremon tells me that they’ve pinpointed the exact day. It’s a two-thousand-and-forty-nine-year cycle, actually, and this is the two-thousand-and-forty-eighth year, and in something like eleven or twelve more months, if you believe Mondior, the sky will turn black and fire will descend on us. I think the nineteenth of Theptar is when it’s supposed to happen.”

  “Theremon? The newspaperman?”

  “Yes. He’s a friend of mine, actually. He’s interested in the whole Apostles thing and he’s been interviewing one of their high priests, or whatever. Theremon told me—”

  Siferra’s hand shot out and caught Beenay’s arm, her fingers digging in with astonishing force.

  “You’ve got to promise me you won’t say a word about any of this to him, Beenay!”

  “To Theremon? No, of course not! You haven’t published your findings yet. It wouldn’t be proper for me to say anything to anybody! —But of course he’s a very honorable man.”

  Her iron grip relaxed, but only a little.

  “Sometimes things get said between friends, off the record—but you know, Beenay, there’s no such thing as ‘off the record’ when you’re talking to someone like Theremon. If he sees a reason to use it, he’ll use it, no matter what he may have promised you. Or however ‘honorable’ you like to think he is.”

  “Well—perhaps—”

  “Trust me. And if Theremon were to find out what I’ve come up with here, you can bet your ears it’ll be all over the Chronicle half a day later. That would ruin me professionally, Beenay. It would be all I need, to become known as the scientist who provided the Apostles with proof of their absurd claims. The Apostles are totally repugnant to me, Beenay. I don’t want to offer them any sort of aid and comfort, and I certainly don’t want to seem to be publicly espousing their crackpot ideas.”

  “Don’t worry,” Beenay said. “I won’t breathe a word.”

  “You mustn’t. As I say, it would wreck me. I’ve come back to the university to have my research grant renewed. My Thombo findings are already stirring up controversy in the department, because they challenge the established view of Beklimot as the oldest urban center. But if Theremon somehow manages to wrap the Apostles of Flame around my neck on top of everything else—”

  But Beenay was barely listening. He was sympathetic to Siferra’s problem, and certainly he would do nothing to cause difficulties for her. Theremon would hear not one word about her research from him.

  His mind had moved on, though, to other things, vastly troublesome things. Phrases out of Theremon’s account of the teachings of the Apostles continued to churn in his memory.

  “—In something like fourteen months the suns will all disappear—”

  “—the Stars will shoot flame down out of a black sky—”

  “—the exact time of the catastrophe can be calculated scientifically—”

  “—a black sky—”

  “—the suns will all disappear—”

  “Darkness!” Beenay muttered harshly. “Can it be possible?” Siferra had gone on talking. At his outburst she halted in mid-sentence.

  “You aren’t paying attention to me, Beenay!”

  “I—what? Oh. Oh. Yes, of course I’m paying attention! You were saying that I mustn’t let Theremon know anything about this, because it would harm your reputation, and—and—listen, Siferra, do you think we could continue discussing this some other time? This evening, or tomorrow afternoon, or whenever? I’ve got to get over to the Observatory right away.”

  “Don’t let me detain you, then,” she said coldly.

  “No. I don’t mean it that way. What you’ve been telling me is of the most colossal interest to me—and importance, tremendous importance, more than I can even say at this point. But I’ve got to check something. Something with a direct bearing on everything we’ve been discussing.”

  She gave him a close look. “Your face is flushed. Your eyes are wild, Beenay. You seem so strange, all of a sudden. Your mind’s a million miles away. What’s going on?”

  “I’ll tell you later,” he said, halfway out the door. “Later! I promise you!”

  [16]

  At this hour the Observatory was practically deserted. No one was there but Faro and Thilanda. To Beenay’s relief, Athor 77 was nowhere to be seen. Good, Beenay thought. The old man was exhausted enough from the effort he had devoted to working out the Kalgash Two concept. He didn’t need more stress loaded upon him this evening.

  And it would be just fine, having only Faro and Thilanda here. Faro had exactly the kind of quick, untrammeled mind that Beenay needed right now. And Thilanda, who had spent so many years scanning the empty spaces of the heavens with her telescope and camera, might be able to fill in some of the conceptual material Beenay would require.

  Thilanda said at once, “I’ve been developing plates all day, Beenay. But it’s no go. I’d stake my life on it: there’s nothing up there in the sky except the six suns. You don’t think the great man’s finally gone around the bend, do you?”

  “I think his mind is as sharp as ever.”

  “But these photos—” Thilanda said. “I’ve been running a random scan of every quadrant of the universe for days now. The program’s all-inclusive. Snap, move down a couple of degrees, snap, move, snap. Methodically sweeping the entire sky. And look at what I’m getting, Beenay. A bunch of pictures of nothing at all!”

  “If the unknown satellite is invisible, Thilanda, then it can’t be seen. It’s as simple as that.”

  “Invisible to the naked eye, maybe. But the camera ought to be able to—”

  “Listen, never mind that now. I need some help from you two, purely theoretical stuff. Related to Athor’s new theory.”

  “But if the unknown satellite’s nothing but pie in the sky—” Thilanda protested.

  “Invisible pie might still be real pie,” Beenay snapped. “And we won’t like it when it comes hurtling out of nowhere and hits us in the face. Will you help me or won’t you?”

  “Well—”

  “Good. What I want you to do is prepare computer projections of the movements of all six suns covering a period of forty-two hundred years.”

  Thilanda gaped incredulously. “Four thousand two hundred, is that what you said, Beenay?”

  “I know that you don’t remotely have records of stellar movements over any such span. But I said computer projections, Thilanda. You’ve got at least a hundred years of reliable records, right?”

  “More than that.”

  “Even better. Set them up and project them backward and forward in time. Have the computer tell you what every daily combination of the six suns was for the last twenty-one centuries, and for the twenty-one centuries to come. If you can’t do it, I’m sure Faro will be glad to help you
write the program.”

  “I think I can manage it,” said Thilanda in a glacial tone. “And would you mind telling me what this is all about? Are we going into the almanac business now? Even the almanac is content to settle for just the next few years of solar data. So what are you up to?”

  “I’ll tell you later,” Beenay said. “That’s a promise.”

  He left her fuming at her desk and walked across the Observatory to Athor’s work area, where he took a seat in front of the three computer screens on which Athor had calculated the Kalgash Two theory. For a long moment Beenay stared thoughtfully at the center screen, showing the orbit of Kalgash as perturbed by the hypothetical Kalgash Two.

  Then he touched a key and the proposed orbital line of Kalgash Two became visible in bright green, a huge eccentric ellipse splayed out across Kalgash’s own more compact and nearly circular orbit. He studied it for a while; then he hit the keys that would bring the suns onto the screen, and peered broodingly at them for perhaps an hour, summoning them in all their varying configurations, now Onos in the sky with Tano and Sitha. Onos with Trey and Patru, Onos and Dovim with Trey and Patru, Dovim with Trey and Patru, Dovim with Tano and Sitha, Patru and Trey alone—

  The normal patterns, yes.

  But what about abnormal patterns?

  Tano and Sitha alone? No, it couldn’t happen. The relationship of that double-sun system’s position in the heavens to the location of the closer suns was such that Tano and Sitha could never appear in the sky in this hemisphere unless either Onos or Dovim, or both of them, were visible at the same time. Maybe it had been possible hundreds or thousands of years ago, he thought, though he doubted it. But certainly not now.

  Trey and Patru and Tano and Sitha?

  “Another no. The two sets of double suns were on opposite sides of Kalgash; whenever one pair was in the sky, the other one generally was hidden by the planet’s own bulk. Now and then the four of them did manage to get together in the sky, but Onos always was visible when such two-pair conjunctions occurred. Those were the famous five-sun days—which produced the equally distinctive Dovim-only days in the opposite hemisphere. They happened only every few years.”

  Trey without Patru? Tano without Sitha?

  Well, technically, yes. When one of the double-sun pairs was close to the horizon, one sun would be above the horizon and one of them below it for a brief period. But that wasn’t really a significant solar event, just a momentary aberration. The double suns were still together, but transiently separated by the line of the horizon.

  All six suns in the sky at once?

  Impossible!

  Worse than that—unthinkable!

  Yet he had just thought it. Beenay shivered at the idea. If all six of them were above the horizon simultaneously, then there would have to be a region in the other hemisphere where no sunlight whatever could be seen. Darkness! Darkness! But Darkness was unknown everywhere on Kalgash, except as an abstract concept. There could never have been a time when the six suns moved together and a major part of the world was plunged into utter lightlessness. Could there have been?

  Could there?

  Beenay pondered the chilling possibility. Once more he heard Theremon’s deep voice explaining the theories of the Apostles to him:

  “—the suns will all disappear—”

  “—the Stars will shoot flame down out of a black sky—”

  He shook his head. Everything he knew about the movements of the suns in the heavens rebelled against the idea of the six of them somehow bunching up on one side of Kalgash at the same time. It just couldn’t happen, short of a miracle. Beenay didn’t believe in miracles. The way the suns were arranged in the sky, there always had to be at least one or two of them shining over every part of Kalgash at any given moment.

  Forget the six-suns-here, Darkness-there hypothesis.

  What was left?

  Dovim alone, he thought. The little red sun all alone in the sky?

  Well, yes, it did happen, though not often. On those occasional five-sun days when Tano, Sitha, Trey, Patru, and Onos all were in conjunction in the same hemisphere: that left only Dovim for the other side of the world. Beenay wondered whether that might be the moment when the Darkness came.

  Could it be? Dovim by itself might cast so little light, just its cool and feeble reddish-purple gleam, that people might mistake it for Darkness.

  But that didn’t really make sense. Even little Dovim should be able to provide enough light to keep people from plunging into terror. Besides, Dovim-only days occurred somewhere in the world every few years. They were uncommon, but not all that extraordinary. Surely, if the effects of seeing nothing but a single small dim sun in the sky could cause vast psychological upheavals, then everybody would be worrying about the next Dovim-only event, which was due, as Beenay recalled, in just another year or so. And in fact nobody was thinking about it at all.

  But if Dovim alone were in the sky, and something happened, some special thing, some truly uncommon thing, to blot out what little light it provided—

  Thilanda appeared at his shoulder and said sourly, “All right, Beenay, I’ve got your solar projections all set up. Not just forty-two hundred years, either, but an infinite regression. Faro gave me a suggestion for the math and we’ve done the program so that it’ll run clear to the end of time if you want it to, or backward to the beginning of the universe.”

  “Fine. Pipe it over to the computer I’m using, will you? —And will you come here, Faro?”

  The pudgy little graduate student ambled over. His dark eyes were agleam with curiosity. Obviously he was bubbling with questions about what Beenay was doing; but he observed student-professor protocol and said nothing, merely waited to hear what Beenay would tell him.

  “What I’ve got here on my screen,” Beenay began, “is Athor’s suggested orbit for the hypothetical Kalgash Two. I’m going to assume that the orbit’s a correct one, since Athor has told us that it accurately accounts for all the perturbations in our own orbit, and I have faith that Athor knows what he’s doing. I also have here, or at any rate I will when Thilanda has finished the data transfer, the program that you and she have just worked out for solar movements over a long span of time. What I’m going to do now is to attempt to work out a correlation between the presence of just one sun in the sky and the close approach of Kalgash Two to this planet, so that—”

  “So that you can calculate the frequency of eclipses?” Faro blurted. “Is that it, sir?”

  The boy’s quickness was amusing and also a little disconcerting. “As a matter of fact, it is. You have eclipses on your mind too, do you?”

  “I was thinking about them when Athor told us all about Kalgash Two the first time. Simbron, you remember, mentioned that the strange satellite might hide the light of some of the suns for a little while, and you said that that would be called an eclipse, and then I started to work out some of the possibilities. But Athor cut me off before I could say anything, because he was tired and wanted to go home.”

  “And you haven’t said anything about it since?”

  “No one’s asked me,” Faro said.

  “Well, here’s your moment. I’m going to transfer everything that’s on my computer to yours, and you and I are going to sit down in this room separately and begin pushing the numbers around. What I’m searching for is a very special case in which Kalgash Two is at its closest point of approach to Kalgash and there’s only one sun in the sky.”

  Faro nodded. He headed for his computer at a speed faster than Beenay had ever seen him move before.

  Beenay didn’t expect to be the first to finish the computation. Faro was notoriously quick at such things. But the point was to have each of them work on the problem independently, to provide separate validation of the result. So when Faro made a snorting sound of triumph after a little while and jumped up to say something, Beenay irritably waved at him to be silent and went on working. It took him ten embarrassing eternal minutes more.

 
Then the numbers began coming up on his screen.

  If every assumption that he had fed into the computer was correct—Athor’s calculation of the unknown satellite’s probable mass and orbit, Thilanda’s calculation of the movements of the six suns in the heavens—then it wasn’t very likely that Darkness was going to come. The only possibility that would bring total Darkness was a Dovim-only day. But it didn’t look as if Kalgash Two stood much chance of eclipsing Dovim. Dovim-only days were such rarities that the likelihood of Dovim’s being alone in the sky at the time when Kalgash Two was anywhere near Kalgash in its long orbit was infinitesimal, Beenay knew.

  Or were they?

  No. Not infinitesimal.

  Not at all. He took a careful look at the figures on the screen. There seemed to be a slim possibility of a convergence. The calculation wasn’t complete, but things were heading in that direction as the computer worked over each Kalgash-Kalgash Two conjunction in the forty-two-hundred-year period of the inquiry. Every time Kalgash Two came round on its orbit, it reached Kalgash’s vicinity closer and closer to a Dovim-only day. The numbers continued to appear, as the computer processed all the astronomical possibilities. Beenay watched in mounting awe and disbelief.

  There it was, finally. All three bodies lined up in just the right way. Kalgash—Kalgash Two—Dovim!

  Yes! It was possible for Kalgash Two to cause a total eclipse of Dovim when Dovim was the only sun visible in the sky.

  But that configuration was an extreme rarity. Dovim had to be alone in its hemisphere and at maximum distance from Kalgash, while Kalgash Two had to be at its minimum distance. Kalgash Two’s apparent diameter would then be seven times that of Dovim. That was sufficient to hide Dovim’s light for well over half a day, so that no spot on the planet would escape the effects of Darkness. The computer showed that such a highly special circumstance was capable of occurring only once every—