Children of the Comet

by Donald Moffitt

  Chu glanced over to where Nina was chatting with Andrew and some of his friends. She was holding something with a cherry in it. Chu knew that Alten thought she was still too young to drink. But he also knew that Andrew had probably sneaked her something like a Manhattan, an old drink named after the twentieth-century project that had originally split the atom. She saw Chu and waved. He waved back and lifted his glass.

  Irina came over, trailed by her disciple Laurel. “What are you saying about Nina?”

  “That your daughter’s good at math,” Chu said.

  Irina laughed. “She had to be when she was growing up. To please Alten.”

  “Well, she picked up on something that was too simple for your genius husband to think about.”

  “That’s what Joorn said.” She shook her head. “Does it really mean what Nina says it does?”

  “Think about it. What’s the volume of a sphere with a diameter of ninety-three million miles?”

  “There aren’t enough places on my calculator.”

  “Exactly. Multiply pi by four. Then multiply that by the cube of the radius. Then divide that by the number of atoms in a cubic mile, say, of the outer layers of a helium star. Even a lowly starship skipper like Joorn or me can figure that one out.”

  “I can’t.”

  “Then you’ll just have to wait till we get there. If Nina’s right, we’ll show you.”

  CHAPTER 29

  6,000,000,003 A.D.

  A Walk in the Sun

  The landscape was bleak and suffused with a ruddy light. The sky was a bloody red wherever they looked. The three of them cast no shadows whatsoever. The terrain was shot through with dangerous cracks but was otherwise utterly flat, without even a small hill to cast a shadow of its own.

  “You shouldn’t have come, Father,” Alten said. “You’re too old to take the risk. You could have stayed aboard the ship and watched from there.”

  “I’ve traveled two and a half billion light-years to come home,” Joorn said. “I wasn’t about to settle for a view from your helmet cam. Or a probe. I had to set foot on Mother Earth myself.”

  They were wearing the antiquated Venus coolsuits that had been packed away in storage for six billion years. Suits like these had been worn by men on Venus when Time’s Beginning left Earth. They were bulky with insulation and equipped with Maxwell’s Demons, the compact refrigeration units that worked by using sound waves to bat slow molecules in one direction and fast molecules in the other. The exhaust tubes rose high above their heads like medieval pikes, swaying precariously, the heat from them making the air ripple.

  “Me too,” Martin said. “I mean really and truly setting foot on Mother Earth.”

  Alten snorted. “More like Grandmother Earth to you. You’re the youngest. You might have stayed behind and watched from the ship.”

  “Point of privilege,” Martin said.

  Joorn intervened good-naturedly. “The boy’s right. It doesn’t take a member of the Gant dynasty to run the ship. There’s a perfectly competent third officer taking charge.”

  “Thanks for that, Skipper,” Chu said. “Nice to know I’m not needed.” He looked up at the burning sky. The sun reached both horizons. Technically it was sunrise, noon, and sunset at the same time. “We better move on before the soles of our boots melt. We’ve been standing in one place too long.”

  Joorn looked back over his shoulder as if to reassure himself that the lander was still there. It towered some eighty feet above them, but it didn’t cast a shadow either. “Not too far,” he said. “We have to give ourselves time to get back when the monitors beep us that the heat is starting to get the best of the ship’s demon.”

  They shuffled forward about a hundred yards. It was easier than trying to push through the molasses that had been the atmosphere of Venus. Earth had no atmosphere to speak of anymore, and they really didn’t need the suits to be powered. On the other hand, the heat was worse.

  Joorn signaled for a stop. “Anybody see anything yet?” he said.

  “You’re kidding, right?” Chu said. “We could walk a thousand miles and the scenery wouldn’t change.”

  Joorn nodded. “It would be nice to have some place to go to after traveling all those light-years,” he said wistfully.

  “Not much of a homecoming, is it, Grandfather?” Martin asked. “I can almost see why Professor Karn was against coming back.”

  They stared in mutual commiseration at the horizon. It was the same barren surface crust as far as the eye could see, a featureless plain with no shadows, even in the gaping cracks.

  “We came a few million years too early, that’s all,” Alten said. “Nina’s prediction was right on target. The sun’s already begun to shrink. Earth will eventually emerge from the photosphere. The cooling process will speed up, and life will be possible again. And the white dwarf that the sun becomes will still shed enough heat to sustain some sort of life for another billion years.”

  Chu nodded. “And in its death throes the sun will continue to lose mass through flares and coronal mass ejections. So Earth’s orbital radius will keep growing and speed up the cooling process.”

  That stopped Alten for about a half second. Then he said, “I see you’ve been brushing up on your astrophysics, Chu.”

  “I’ve been talking to Nina,” Chu said dryly.

  Martin said, “I ran through her arithmetic myself, Dad. It’s counterintuitive, but it explains why we’re walking around inside the outer chromosphere. The temperature’s still horrendous—though it’s technically down to only about six thousand kelvins here.” He frowned with concentration. “But with a radius the size of Earth’s orbit, the volume of the sun is so tremendous that its matter is tenuous enough to dilute it, especially in the outer layers of the photosphere. Like, putting your hand on a hot stove isn’t the same as touching the point of a pin heated to the temperature of a hot stove.”

  Alten started to correct him but thought better of it. “Keep it up, son. We’ll make a starship pilot of you yet.”

  “Not as good as Chu. And he’ll need a good engineer.”

  Joorn said sharply, “We’ll need a good astrophysicist too. If we’re going to be zipping around the Sol-Centauri system, piloting the ship will be a full-time job.”

  Chu said, “That would be you, Skipper.”

  “I’m already about a hundred years past retirement age,” Joorn demurred. “Are we arguing about who gets to refuse the job?”

  Martin was getting restive. He kept glancing at the sky. “Where do we look next, Grandfather? Venus and Mercury are gone forever. Earth will be a hot potato for the next million years.”

  “We’ll take a closer look at Mars next,” Joorn said. “From the orbital observations, it looked like the surface baked to a hard finish but didn’t melt. There was even a hint of green, though that will have to be confirmed—some of the algae we planted there six billion years ago may have survived and evolved. It may be a fit environment for the human race.”

  “And if it isn’t,” Alten said, “there’s the four Galilean moons of Jupiter. When the sun boiled away Jupiter’s hydrogen—including the metallic form that liquefied when the atmospheric pressure was released—it ended the dynamo effect that was causing Jupiter’s killer radiation. It’s become a nice neighborhood, and now there are four rocky bodies large enough to have gravity similar to Mars.”

  “Five, if you count Jupiter itself,” Chu said. “It turned out to have a rocky core about the size of Earth. Even closer to the gravity we’re used to, and just right for terraforming.”

  “And closer to our new friends in the Oort cloud,” Martin added enthusiastically. “If Mother’s team is right, there’s a whole human civilization there—maybe a trillion people spread out all the way to Alpha Centauri. We can’t ignore them. We have a lot to offer each other, and commerce of a sort has already begun.”
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  “We’ll see,” Joorn said. “We’re getting ahead of ourselves. Right now we have to keep moving. My feet are feeling warm.”

  They moved on till they came to the edge of a crack. They stopped and peered down into a chasm that was several hundred feet deep. There was a glint of lava at the bottom.

  They were still staring downward when the dull red glow of the landscape all around them suddenly turned a blinding white. That was a lucky thing because their helmets’ filters kicked in a fraction of a second too late.

  Moments later, the lander’s AI announced, “Coronal mass ejection. Return to lander immediately.”

  Joorn cursed. “How long before the heavy stuff gets here?” he said.

  Alten was conferring with the AI. After a few more seconds, he raised his head and said, “If we can get off-planet in the next fifteen minutes, we should be able to keep ahead of it.”

  Martin started to run. Joorn stopped him with a sharp command. “Don’t hurry. If anybody stumbles or falls and damages his demon, he’ll be barbecue.”

  Even so, they made it back to the lander in record time. They skimped on recycling time in the airlock and let a lot of hot air into the cabin. Martin threw his helmet back but didn’t stop to unlatch the clamshell halves of his suit. He got busy doing an engine check while Chu seated himself and started the ignition process.

  “How’s the engine temperature?” Joorn said.

  “Fine,” Martin said. “The lander’s demon kept everything nice and cool.”

  The lander took off like a racehorse out of the gate. It had been calibrated for Earth gravity, but Earth had lost a tenth of its mass during its sojourn inside the sun. When its surface resolidified, it weighed about the same as Venus. Or the former Venus—the solar system’s second planet had turned into plasma.

  They were past the orbit of Mars and still accelerating when they looked back. A gob of glowing plasma, bigger than worlds, had enveloped Earth and was now chasing them.

  “Don’t worry, Martin,” Chu said. “The CME can’t catch us now. The plasma cloud’s only traveling at about five million miles an hour, and we’re outrunning the high-energy protons too.”

  “I’m not worried,” Martin said stiffly. “I can do the math too.”

  “By the time the CME reaches the orbit of Mars, it’ll have spread out to a width of about ten million miles anyway,” Alten said. “Too diluted to even give us a summer tan.”

  “I said I’m not worried, Father.”

  Time’s Beginning was waiting for them beyond the orbit of Neptune. From here, the sun was only a star, though as a red giant it was the brightest star in the sky. It still cast a measurable amount of heat though. At the limit of its expansion, it had melted the ice of Europa and stripped Jupiter of its hydrogen, after all. Neptune’s orbit had been deemed a safe enough distance for the ship to park, though in view of the importance of the decision, Joorn had deemed it necessary to put it to a general vote.

  Neptune was only four light-hours from Earth, but it took them some weeks to reach it because even at a one-G acceleration there wasn’t enough time to attain near-lightspeed. By the time they arrived, they were tired, unshaven, and badly in need of a proper shower.

  They paused at the airlock to drink in the magnificent sight of a full Neptune. It had managed to hold on to its hydrogen-helium atmosphere through the sun’s red-giant era, and from close orbit it filled the sky, a luminous blue sphere that bathed Time’s Beginning in its reflected light. The starship was parked in a co-orbit with Naiad, one of Neptune’s smaller moons, to anchor it more conveniently. It was an unequal partnership, but it saved a lot of finicky orbital maneuvering.

  Joorn led the way through the boat lock’s access corridor. “You two can go on ahead and get yourselves cleaned up,” he said. “I’m going to stop at the bridge and check in with Robertson. The time lag on the last transmission from him was over two hours.”

  Robertson, the third officer, had served as captain pro tem during their absence.

  “We’ll go with you, Skipper,” Chu said.

  Martin nodded. “I want to see what the ship’s instruments made of that coronal mass ejection.”

  They traversed the corridors to the bridge, passing pedestrians from time to time. People called out greetings, curiosity plain in their voices, but no one was ill-mannered enough to try to engage them in conversation.

  There were still guards at the entrance to the bridge, though it had been several years since the Karnites’ second attempt at mutiny. Ryan was still ship’s president, and he was taking no chances. Necessary or not, security guards at the bridge were an established custom now.

  “Glad to see you back, Captain,” said one of them, as he let the three in. “Some were saying they were afraid you wouldn’t make it.”

  Joorn laughed. “Sorry to disappoint them, Paxton. But they aren’t getting rid of me that easily.”

  Robertson had been alerted, and he rose to greet them. He nodded to Martin and Chu, and said, “How was it on Earth, Captain?”

  “Hot,” Joorn said. “How did things go aboard ship?”

  “Fine.” Robertson looked worried. “But …”

  Joorn became instantly attentive. “What is it, Robertson?”

  “It only happened a couple of hours ago. There didn’t seem to be any point in exchanging messages with you because of the time lag. You’d be back here by the time …”

  “What is it, man?” Joorn said impatiently.

  Robertson continued doggedly. “It … actually happened at least two years ago anyway, since it’s in the middle of the Oort cloud, and at that distance, the light from …”

  “What?”

  “It was the light from a Higgs drive. Hadronic photons and some of the characteristic decay products. And a little of the associated hard stuff—enough for us to detect but not enough to do any harm at this distance.”

  Joorn’s jaw dropped. “A Higgs drive!”

  Chu found his voice. “That means …”

  “Yes,” Joorn said.

  “The Higgs drive turned off after penetrating the Oort cloud,” Robertson went on, “and the source, whatever it was, continued decelerating using deuterium-helium-3 fusion or some other less lethal reaction like deuterium-deuterium.”

  “Like us,” Martin said.

  “They have some sort of ethics then,” Chu said.

  “That’s not all,” Robertson said. “We were able to continue to track them briefly. We lost them, but it looked like they were making a beeline to the part of the cloud where we left our beacons.”

  “Orbiting Torris’s comet,” Chu said.

  “I’m afraid so.”

  “It’ll take us at least two years to get back there,” Martin said. “In the meantime …”

  “In the meantime, anything could happen. Like the Higgs drive being turned back on.”

  At that point the door swung open and Nina burst in, brushing past the guards. She spared only a distracted glance for her father and Martin and flung herself sobbing into Joorn’s arms.

  “Grandfather, Grandfather, did Mr. Robertson tell you? Mother and I only found out about it a little while ago! What does it mean? What’s going to happen to Torris and Ning and all those people? We’ve got to get back there right away!”

  CHAPTER 30

  6,000,000,005 A.D.

  The Oort Cloud

  The captain’s name was Yung, and his ship was the Tien Shih—the “Celestial Arrow.” It had been launched some two hundred years after Time’s Beginning by the Chinese Commonwealth.

  Yung was a tall, dignified man who looked about seventy, though he must have been Joorn’s age. He was wearing a naval uniform that hadn’t changed much through the ages: a white high-necked tunic and plenty of gold braid. The captain’s saloon was elegantly furnished in a style that wouldn’t have been
out of place on a sailing ship from the days of the China Trade, with uncomfortable high-backed armchairs of carved ebony, a straight-backed velvet couch, Chinese screens, and lots of wicker. There was even a gilt cage with a live thrush in it.

  He poured tea from an antique teapot, serving Irina and Nina first and then the men. There was a painted tray with elaborate little pastries that no one had touched.

  “We planted our colonies in MR 2251-178,” he was saying, “a quasar as seen from Earth at the time. Like your 3C-273, it had settled down into a proper galaxy by the time we got there. If there ever had been First Ones, as in our own Milky Way, they’d been gone for a good three and a half billion years. We seeded five of the galaxy’s stars with our colonists, providing the nuclei for a galaxy-wide Commonwealth, thus discharging our obligations to our ancestors, extinct these six billion years.”

  He paused to sip his tea. He might have been laboring under strong emotion, but his voice remained under firm control as he continued.

  “The remaining colonists—five thousand of them—voted to remain aboard Celestial Arrow and return to the Milky Way, just as your own Homegoing faction did. Though I must say, without the necessity of a mutiny like Professor Karn’s. Everything was done lawfully. They were under no illusions about what we’d find here, but there was every confidence that we might, in some way, resurrect the Middle Kingdom in the galaxy where it was born. I’m sure that you and your people can understand that kind of ancestral yearning, Captain.”

  “Indeed we can,” Joorn said. There was a murmur of agreement from the rest of his party.

  “But we can discuss all that later,” Captain Yung said. He broke into a smile. “It’s an honor to meet you, Captain Gant. Your name is in all the history books, and you are a hero to all those who believed in man’s destiny. Of course no one had the slightest inkling of what happened to your ship after it passed out of the Local Group, but you are an inspiration to boys like me. I became a spaceman because of you.”

  Joorn ignored the transparent attempt at flattery. “You said ‘the first expedition,’” he prompted.