A Time Odyssey Omnibus

by Arthur C Clarke - Stephen Baxter

  Cassie complied, but she kept her eyes fixed on Bella. “Space-based weapons systems,” she said. “That’s what my husband was working on, wasn’t it?”

  And she spoke of hints from the sky, traces, fragmentary clues that had been assembled by conspiracy theorists and sky-watchers of varying degrees of sanity and paranoia. They had seen the straight-line exhaust trail of a ship sliding across the sky at impossible speeds. The Liberator, of course. And they had seen another vessel, slow, ponderous, massive, moving in the asteroid belt, leaving behind the same kind of trail. That was clearly the tractor, preparing for the Big Whack. These ships had all been shrouded, but mankind’s invisibility shields were not yet perfect.

  Bella asked, “So what do you think all this means?”

  “That something is coming,” Cassie said. “Another sunstorm, perhaps. And the governments are preparing to flee with their families, in a new generation of superfast ships. That’s not a consensus view, but a common suspicion, I’d say.”

  Bella was shocked. “Do people really think so little of their governments that they imagine we’re capable of that?”

  “They don’t know. That’s the trouble, Bella. We live in the aftermath of the sunstorm. Maybe it’s rational to be paranoid.” Cassie folded away her softscreen. “Bella, I have followed this path not for my husband’s sake, or my own, but for my children. I think you are hiding something—something monstrous, that might affect their future. And they have a right to know what that is. You have no right to keep it from them.”

  Time for Bella to make her judgment about what to do about this woman. Well, Cassie was not a criminal. She was in fact the sort of person Bella had been appointed to protect.

  “Look, Cassie,” Bella said. “You’ve picked up some of the pieces of the jigsaw. But you’re assembling them into the wrong picture. I don’t want any harm to come to you, but on the other hand, I don’t want you to do any harm either. And by spreading this sort of theory around, harm is what you may inflict. So I’m going to take you into my confidence—the confidence of the Council. And when you know what I know, you can use your own judgment on how best to use the information. Is that a deal?”

  Cassie thought it over. “Yes, Bella, that’s fair.” And she looked at Bella, apprehensive, excited. Scared.

  Bella glanced at the clock on the wall. Thirty minutes before she would receive news of what had become of the Big Whack experiment. That desperate drama must be playing itself at this very moment, out among the asteroids, twenty-eight light-minutes away.

  She put that aside. “Let’s start with the Liberator,” she said. “Your husband’s legacy. Graphics, please, Thales.”

  They spoke of the Liberator. And of the Q-bomb it had been shadowing for months.

  And then Bella showed Cassie Bob Paxton’s last option.

  “It’s just another asteroid, drifting through the belt,” Bella said. “It has a number in our catalogs, and whoever landed that mining survey probe on it”—it was a metallic spark on the asteroid’s coal-dust surface—“probably gave it a name. We just call it the cannonball. And here is the ship whose exhaust your conspiracy-theorists saw.”

  “I wish you wouldn’t call them that,” Cassie murmured. She leaned forward to see. “It looks like another asteroid,” she said. “A rock with a silver net around it.”

  That was pretty much what the tractor was: a minor asteroid, much smaller than the flying-mountain cannonball. The rock had had a net of tough nanotube rope cast around it, and an antimatter-drive engine was fixed to its surface. “We used one of the early prototype engines from the Trojan shipyards. Not human-rated but it’s pretty reliable.”

  Cassie began to see it. “You’re using this to steer the bigger asteroid, the cannonball.”

  “Yes—with gravity. It turns out to be surprisingly hard to deflect an asteroid…”

  Turning aside the path of an asteroid had been studied for a century or more, since it had become understood that some asteroids crossed the path of the Earth, and, at statistically predictable intervals, collided with the planet.

  A dangerous rock was generally too big to destroy. An obvious idea was to knock it aside, perhaps with nuclear weapons. Or you could attach a drive to it and just push it. Or you could attach a solar sail to it, or even paint it silver or wrap it in foil, so the pressure of sunlight pushed it aside. Such methods would deliver only a small acceleration, but if you could catch the rock early enough you might do just enough to keep the rock from hitting its undesired target.

  As the asteroid belt was gradually colonized, all these methods had been tried; all failed, to varying degrees. The trouble was that many larger asteroids weren’t solid bodies at all, but swarms of smaller rocks, only loosely bound by gravity—and they were generally rotating too. Try to push them, or blow them up, and they would just fragment into a cloud of smaller impactors that would be almost as lethal and all but impossible to deal with.

  So the idea of the gravitational tractor was developed. Position another rock near your big problem asteroid. Push the second rock aside, gently. And its gravity field would tug at its larger sibling.

  “You see the idea,” Bella said. “You have to keep pushing your rock just too feebly to be able to escape the asteroid’s gravity field, so your tractor remains bound to the target. And the target will be drawn away no matter how broken-up it is. The only tricky part is orienting your tractor’s exhaust plume so it doesn’t impact the target’s surface.”

  Cassie nodded, a little impatiently. “I get the idea. You’re deflecting the orbit of this rock, this cannonball—”

  “So that it hits the Q-bomb. The bomb and the cannonball are on radically different trajectories; the impact will be fast—high-energy.”

  “When will this happen?”

  “In fact,” Thales said gently, “it did happen, nearly half an hour ago. Two minutes until the report comes in, Bella.”

  The graphics of tractor and cannonball vanished, to be replaced by a steady image of the Q-bomb, that eerie sphere visible only by reflected starlight, floating in a cloud of velvet above Bella’s desk. And beside it was a matchstick spacecraft.

  Cassie understood. It took her a few seconds to compose herself. Then, wide-eyed, she said, “It’s happening now. This impact. And your daughter is out there, in her shrouded battleship, observing. You brought me in at a time like this?”

  Bella found her voice was tight. “Well, I need to keep busy. And besides—I think I needed to see your reaction.”

  “Thirty seconds, Bella.”

  “Thank you, Thales. You see, Cassie—”

  “No. Don’t say any more.” Impulsively Cassie leaned across the table and grabbed Bella’s hand. Bella hung onto it hard.

  In the graphic, bomb and escort hung silently in space, like ornaments.

  Something came flying into the desktop image from the left-hand side. Just a blur, a gray-white streak, too fast to make out any details. The impact brought a flash that filled the virtual tank with light.

  Then the projection fritzed and disappeared.

  Bella’s desk delivered scrolling status reports and talking heads, all reporting aspects of the impact. And there were calls from across Earth and the Spacer colonies, demanding to know what was going on in the belt; the explosion had been bright enough to be seen with the naked eye in the night skies of Earth, as well as across much of the rest of the system.

  By pointing, Bella picked out two heads: Edna, and then Bob Paxton.

  “…Just to repeat, Mum, I’m fine, the ship’s fine, we stood off sufficiently to evade the debris field. Quite a sight, all that white-hot rock flying off on dead straight lines! We got good data. It looks as if Lyla’s projections on the likely loss of mass-energy by the Q-bomb have been borne out. But—”

  Bella flicked to Bob Paxton; his face ballooned before her, ruddy, angry. “Madam Chair, we haven’t touched the damn thing. Oh, we bled off a bit of mass-energy, even the Q couldn’t eat a fucking ast
eroid without burping, but not enough to make a bit of difference when that thing gets to Earth. And get here it will. It’s not been deflected at all, not a hairsbreadth. It defies everything we know about inertia and momentum.

  “And—okay, here it comes. We got the numbers now to do some extrapolating about what happens to the Earth if the Q-bomb hits, on the basis of how the rocks we have been throwing seemed to have drained the bomb. Umm. The bomb is not infinite. But it’s big. The bomb is big enough to destroy Mars, say. It won’t shatter Earth. But it will deliver about as large an impact as the planet could sustain without breaking up. It will leave us with a crater the size of Earth’s own radius.” He read, “‘This will be the most devastating event since the mantle-stripping impact that led to the formation of the Moon…’” He ran down, and just stared at the numbers off camera. “I guess that’s that, Madam Chair. We did our best.”

  Bella had Thales hush his voice. “Well, there you are, Cassie. Now you know everything. You’ve seen everything.”

  Cassie thought it over. “I’m glad your daughter is okay.”

  “Thank you. But the strike failed.” She spread her hands. “So what do you think I should do now?”

  Cassie considered. “Everybody saw that collision, on Earth and beyond it. They know something just happened. The question is, what do you tell them?”

  “The truth? That the world is going to end by Christmas Day?” She laughed, and wasn’t sure why. “Bob Paxton would say, what about panic?”

  “People have faced tough times before,” Cassie said. “Generally they come through.”

  “Mass hysteria is a recognized phenomenon, Cassie. Documented since the Middle Ages, when you have severe social trauma, and a breakdown of trust in governments. It’s a significant part of my job to ensure that doesn’t happen. And you’ve already told me the governments I work for aren’t trusted.”

  “Okay. You know your job. But people will have preparations to make. Family. If they know.”

  Of course that was true. Looking at Cassie’s set, determined face, the face of a woman with children of her own under threat, Bella thought she could use this woman at her side in the days and weeks to come. A voice of sanity, amid the ranting and the angry.

  And somebody was ranting at her right now. She glanced down to see the choleric face of Bob Paxton, yelling to get her attention. Reluctantly she turned up the volume.

  “We got one option left, Chair. Maybe we ought to exhaust that, before we start handing out the suicide pills.”

  “Bisesa Dutt.”

  “We’ve been pussyfooting around with these fuckers on Mars. Now we got to go get that woman out of there and into a secure unit. Earth’s future clearly depends on it. Because believe me, Chair Fingal, we ain’t got nothing else.” He paused, panting hard.

  Cassie murmured, “I’m not sure what he’s talking about. But if there is another option—” She took a breath. “I can’t believe I’m saying this. I guess this isn’t like the sunstorm, when we all had to know what was coming to build the shield. This time there’s nothing we can do. You can spare people the disruption of knowing as long as this final option is still available. And then, when there really is no hope—”

  “So we lie to the human race.”

  “Say it was a weapons test gone wrong. Why, that’s almost true.”

  Bella pointed to Edna’s image. “Thales, I want to send a message to Liberator. Your highest level of security.”

  “Yes, Bella.”

  “Look, Cassie, are you free for the next few hours? I think I’d like to talk a little more.”

  Cassie was surprised. But she said, “Of course.”

  “Channel opened. Go ahead, Bella.”

  “Edna, it’s me. Listen, dear, I have a new mission for you. I need you to go to Mars…”

  As she spoke, she glanced at her calendar. Only months were left. From now on, she sensed, whatever happened, the tension would rise, and the pace of events accelerate inexorably. She only hoped she would be able to exercise sound judgment, even now.

  PART 4

  DECISIONS

  47: OPTIONS

  July 2070

  Yuri came running in. He spread his softscreen out on the crew table. “At last I got the stuff downloaded from Mir…”

  The screen began to fill up with images of worlds, blurry photographs, and blue-green pencil sketches.

  Wells Station’s Can Two, the “house,” had one big inflatable table, used for crew meals, conferences, as a work surface. The table was modular; it could be split up into two or three. It was another bit of confinement psychology, Myra understood. The crew didn’t even have to eat together, if they chose not.

  Right now all the bits of the big table were pushed together. For days it had been used as the focus of a kind of unending conference. Yuri was trying to make sense of the alternate-Mars images Bisesa’s phone had slowly, painfully returned through the low-bandwidth Eye link. Ellie was slaving over her analysis of the Eye’s gravitational cage. Only Hanse Critchfield wasn’t working on some aspect of the Q-bomb threat, insisting he was more use with his beloved machines.

  And Myra, Alexei, and Grendel Speth, with comparatively little to contribute, sat glumly at the scuffed table, cups of cool low-pressure coffee before them.

  There was a sense of shabbiness in this roundhouse on Mars, Myra thought, compared to the expensive, expansive, light-filled environs of Cyclops. Yet, as Athena kept assuring them, they were at the focus of a response to a danger of cosmic proportions. The detonation in the asteroid belt had been visible on all the human worlds. Much of Earth had shut down, a civilization still traumatized by the sunstorm huddled in bunkerlike homes, waiting.

  But time was running out. And on Mars there was a sense of rising panic. The Earth warship Liberator was now only days away, and they all knew why it was coming.

  “All right,” Yuri said. “Here’s what we’ve got. As I understand it, the consensus among us is that the Mir universe contains a set of time-sliced samples. A showcase of solar life at its optimum on each world.”

  “All Sol’s children at their prettiest,” Grendel said. “But it can’t last. I mean, both Venus and Mars must have reached their peak of biodiversity in the early days of the solar system, when the sun was much cooler. As best anybody can tell, the Mir sun is a copy from the thirteenth century. That sun is too hot for these worlds. They can’t last long.”

  “But,” Yuri growled, “the point is, here are the worlds of the solar system as they were in the deep past. The question is how they got from past to present, what happened that made them as they are today. Now, look at Venus. We think we understand this case,” he said. “Right? A runaway greenhouse, the oceans evaporating, the water broken up by the sunlight and lost altogether…”

  Once Venus had been moist, blue and serene. Too close to the sun, it overheated, and its oceans evaporated. With the water lost to space Venus had developed a new thick atmosphere, a blanket of carbon dioxide baked out of the seabed rock, and the greenhouse effect intensified until the ground started to glow, red-hot.

  “A horror show, but we understand it. For Venus, our models fit,” said Yuri. “Yes? But now we turn to Mars. Mars was once Earthlike; but, too small, too far from the sun, it dried and cooled. We understand that much. But look at this.”

  He displayed contrasting profiles, of the ancient Mars on which they stood, and the young Mars of the Mir universe. The northern hemisphere of ancient Mars was visibly depressed beneath the neat circular arc of its younger self.

  “Something happened here,” Yuri said, his anger burning. “Something hugely violent.”

  Myra saw it. It must have been like a hammer to the crown of the skull, a tremendous blow centered here, at the north pole. It had been powerful enough to create the Vastitas Borealis, like a crater that spanned the whole of the northern hemisphere.

  They all saw the implication, immediately.

  “A Q-bomb,” Alexei said. “Scaled t
o Mars’s mass. And directed here, at the north pole. This would be the result. By Sol’s tears. But why? Why hit Mars, and not Venus?”

  “Because Venus was harmless,” Yuri snapped. “Venus was a water-world. If intelligence rose there at all it would have been confined to some seabed culture, using metals from geothermal vents or some such. They just didn’t put out the kind of signals you could see from afar. Roads, cities.”

  “But the Martians did,” Myra said.

  And their reward had been a mighty, sterilizing impact.

  Grendel was growing excited. “I think we’re seeing elements of a strategy here. The Firstborn’s goal seems to be to suppress advanced technological civilizations. But they act with—economy. If a star system is giving them cause for concern, they first hit it with a sunstorm. Crude, a blanket blowtorching, but a cheap way of sterilizing an entire system. I bet if we dig deep enough we’ll find a relic of at least one more sunstorm in the deep past. But if the sunstorms don’t work, if worlds continue to be troublesome, they strike more surgically. Just as they targeted Mars. Just as they’ve now targeted Earth.”

  “You’ve got to admit they’re thorough,” Yuri said.

  Alexei said, “And we know from Athena and her Witness that we aren’t the only ones. The Firstborn’s operations are extensive in space and in time. ‘A fire devoureth before them; and behind them a flame burneth: the land is as the Garden of Eden before them, and behind them a desolate wilderness; yea, and nothing shall escape them.’ The Book of Joel.”

  Myra raised her eyebrows. “Let’s not be hypocrites. Maybe the megafauna of Australia and America felt much the same way about us.”

  “They’re like gods,” Alexei said, still in apocalyptic mood. “Maybe we should worship them.”

  “Let’s not,” Yuri said dryly. “The Martians didn’t.”

  “That’s right,” Ellie said now. She came bustling into the room with a softscreen. “The Martians struck a blow. And maybe we can too.” In the midst of their huddled, fearful gloom, Ellie was grinning.