Starquake

by Robert L. Forward

  Acknowledgments

  My thanks to my many friends who contributed ideas and helped me in several technical areas. In addition to those who helped in making the neutron star world of Dragon's Egg more believable, I want to thank Paul Blass, Rod Hyde, Keith Lofstrom, David Lynch, Lester del Rey, and Mark Zimmer-mann for additional help on this sequel.

  My special thanks to Eve for generating new names for the many generations of cheela that lived, fought, and died on the following pages and to Martha for putting up with a husband constantly off in a brown study

  Prelude

  Burrowing through the dark void between the Sun and its stellar neighbors, a tiny visitor came to the Solar System—a rapidly spinning, white-hot, ultra-dense neutron star. A super-strong magnetic field impaled the star from east to west. Reaching out from the rotating star, the two whirling arms of magnetic force whipped at the random atoms floating in space until they were moving at nearly the speed of light. The shocked atoms gave off a pulsating beam of powerful radio waves. Thus, even though the tiny neutron star was too small to be seen in the sky by the naked eye, it had been detected by radio telescopes on Earth long before it arrived at the Solar System.

  The neutron star was given the name "Dragon's Egg." When it was first detected, its position in the sky was at the end of the constellation Draco, as if the dragon had left an egg behind in its nest.

  The discovery of magnetic monopoles had revolutionized fusion-rocket technology, so it wasn't long before the first "interstellar" expedition reached the star, only some 2120 AU from Earth. Riding in the interstellar spacecraft St. George, the exploration crew approached the visitor carefully, for a neutron star can be dangerous if approached too closely without taking proper precautions.

  Although Dragon's Egg was only 20 kilometers in diameter, the surface gravity was 67 billion times Earth gravity, the 8200 K temperature was hotter than the Sun, and the trillion-gauss magnetic field threading through the star at the "East" and "West" magnetic "Poles" was so strong it could elongate a

  normally round atomic nucleus into a cigar shape. Since Dragon's Egg was spinning at slightly more than five revolutions per second, the rapidly moving magnetic fields emanating from the East and West Poles would cook any humans who approached the star too closely without protection.

  To counteract the gravity and the rotating magnetic fields, the scientists on St. George placed Dragon Slayer, their small science capsule, in a 406 kilometer synchronous orbit about the star, where the extreme gravity was canceled by the centrifugal force. Here also, Dragon Slayer would be moving along with the magnetic field and at 406 kilometers distance the magnetic field was no longer dangerous, just a nuisance.

  Although the orbital motion of Dragon Slayer canceled the gravity at the center of the spacecraft, the match was not perfect everywhere. The residual gravity tides of 200 gravities per meter were still dangerous, but the exploration scientists devised a solution for that problem. They looped a superconducting cable a million kilometers long around the neutron star. The cable was used to extract electrical energy from the star's rotating magnetic field. The electrical currents in the cable powered a robotic factory that produced magnetic monopoles. The monopoles were injected into eight of the many asteroids that had been collected by the neutron star during its journey through space. There were two large asteroids and six small ones.

  The monopoles from the factory condensed the asteroids until they were almost the density of the neutron star itself. Using the gravity interactions between the two larger asteroids, Otis and Oscar, the humans and their computers played a game of celestial billiards that placed the six smaller asteroids in a circular formation in synchronous orbit over the East Pole of the star. Then, using Otis as a gravitational elevator, Dragon Slayer and its crew was hauled down to join them.

  Once in orbit, the crew began to map Dragon's Egg. They expected to learn many interesting scientific facts about this dense visitor to their Solar System, but they also found something they had never expected.

  Life!

  Life on the surface of a neutron star!

  The alien creatures, the "cheela," were dense—as dense as the crust that covered the white-hot star. The tiny bodies of the cheela, a little larger than sesame seeds, weighed as much as

  a human, since they were made of degenerate nucleonic material. The life processes of the cheela used interactions between the nuclear particles in the bare nuclei that make up the cheela, while life on Earth uses electronic interactions between the electron clouds of the atoms that make up humans. Because nuclear reactions take place a million times faster than electronic reactions, the cheela thought, talked, lived, and died a million times faster than the humans in orbit above them.

  When Dragon Slayer first took up its position over the East Pole, the cheela were little more than savages and were awed by the laser mapping beams sent down from the middle of the strange star formation floating motionless in their sky. They raised a huge mound temple to worship the new Gods. The humans saw the temple and started sending simple picture messages, one pulse per second. Within less than a day the cheela had developed their technology to the point that they were able to send their first crude, handmade signals to the Gods above them, at 250,000 pulses per second. The humans, finally realizing the immense time difference, worked as rapidly as they could, but nearly a generation went by on the surface of the neutron star before the human laser pulses answered the crude flare signals sent by the cheela below. The human crew used the slower science instruments such as the laser radar mapper for human-to-cheela communication, while the computer dumped the contents of the ship's library directly from the Holographic Memory storage cubes through a high-speed laser communicator to the surface below.

  Chief Scientist Pierre Carnot Niven watched as Chief Engineer Amalita Shakhashiri Drake inserted the first of the 25 library HoloMem cubes, A to AME, into the communications console.

  "A complete education, from Astronomy to Zoology," Pierre mused. "Alphabetical order may not be the best way to teach someone, but in this case it's the fastest."

  For half a day the humans were the teachers for the cheela. In that 12 hours, 60 cheela generations passed. These were prosperous generations for the cheela, with the manna of knowledge pouring from the heavens keeping the previously warring clans on the star busy and at peace. After the first half day, the cheela had surpassed the human race in technological development and it was now time for the humans to become the students. Despite their tired bodies and their bewilderment

  over the rapidity of events in the past day, the humans continued to work diligently at their various science instruments and consoles, while one after another, the HoloMem crystals in their ship's library were rewritten with new knowledge from the cheela.

  Leaving

  06:00:00 GMT TUESDAY 21 JUNE 2050

  Beep! Beep! Beep!

  Pierre Niven opened his tired eyes and awkwardly turned off the alarm on his wrist chronometer. Six hours of sleep. He rubbed his hand over his bearded chin. The beard needed a trim and there were probably a few grey hairs peeking through the brown, but there was work to do. A quick bite in the galley, then he would relieve Amalita at the communications console. Both she and Seiko were long overdue for a sleep break. He heard muffled curses from the next sleep rack as Jean Kelly Thomas struggled to put her bed up.

  The long day started.

  06:05:06 GMT TUESDAY 21 JUNE 2050

  Multi-scientist Seiko Kauffmann Takahashi was on the Science Deck working with the star image telescope. The telescope looked at the neutron star with a one-meter diameter mirror in the top of the cylindrical tower of star-oriented instruments that stuck out of the "north pole" of Dragon Slayer's spherical body. The telescope brought a large, bright
image down through the hollow center of the tower and focused it on the frosted surface of the star image table in the middle of the top deck. Seiko looked down at the image while the computer looked up at the same image through the array of light detectors built under the surface of the table. When the crew first arrived a little over a day ago, the star image had only a few features in it. There had been the large volcano in the northern

  hemisphere, and the rough, mountainous regions at the East and West Poles where infalling meteoric material collected. Now, just a day later, the star was covered with a network of super-highways connecting great cities that grew in size even as Seiko watched. Noticing something happening in the outskirts of the capital city, Bright's Heaven, she efficiently took her compact body swiftly through a set of coordinated free-fall twists that put her on the other side of the table, then took a closer look.

  "Abdul," Seiko said. "I would like you to observe this. There is a strange phenomenon occurring at the old Holy Temple."

  "Just a sec while I reset the neutrino detector," electronic engineer Abdul Nkomi Farouk replied as he pushed himself over to hover above the star image table. Seiko reached up to the ceiling and made some adjustments to the telescope controls. The disk of light on the table expanded to show an elongated twelve-pointed star formation in the southern hemisphere of the neutron star.

  Still the largest structure on the star, the Holy Temple had been raised by the cheela nearly 24 hours ago as they emerged from barbarism. Led by the ancient prophet Pink-Eyes (one of the few cheela who could see the visible light from the human's laser mapping beam), the cheela had raised the great mound-temple to serve as a place for worship of their pantheon of gods: the God-Star Bright (our nearby Sun hovering over the South Pole axis of the neutron star), Bright's Messenger (the large asteroid, Otis, in its highly elliptical orbit), the six Eyes of Bright (the six small asteroids in a circle hovering over the East Pole), and the Inner Eye of Bright (the tiny human spacecraft at the center of the ring of asteroids).

  After the humans had established contact and convinced the cheela that they were not gods, the Holy Temple had been neglected and was slowly fading away into the landscape. The shape of the temple was that of a cheela at full alert, a long ellipsoidal body, with the long direction aligned along the local direction of the magnetic field, and twelve round eyes perched on short, exponentially tapered eye-stubs. After a hundred generations of neglect, the ancient ruins had degenerated to twelve blobs that used to be eyes and portions of wall mounds that had formed the rest of the body. Now, however, one of the eyes was once again dark and round, while its eye-stub was easily visible in the telescope image.

  Abdul thoughtfully twisted one black whisker tip with his fingers as he pondered the scene. "Looks like they're fixing up the Holy Temple. Are they reverting to human worship?"

  "Absolutely not." Seiko pronounced her verdict in the authoritative Teutonic tone she had learned from her father. "They are too intelligent for that. Since they now have space travel, they must have looked down and realized that the most visible structure on Egg looks rundown. Unless your neutrino and X-ray detectors have responded to a crustquake recently, it must be some sort of historical renovation project."

  "No big quakes lately," said Abdul. "So they must be doing this on purpose."

  "It's about time," Seiko humphed in disapproval. "That is the trouble with egg-layers, especially those that let the clan Old Ones raise the young. With no direct family ties through parents, they have no personal links to history."

  Seiko had had no sleep for the past 36 hours. She looked up to adjust the solar image telescope controls to expand the view. The sudden motion made her head swim. She hit the wrong switch, and the filter that blocked most of the light from the neutron star flicked open for an instant. Her eyes shut against the glare.

  "Seiko ... Seiko ..."

  Seiko opened her heavy eyelids to see Dr. Cesar Wong holding her by the shoulders and peering through the wisps of straight black hair that had fallen forward over her face. Floating next to him was Abdul.

  "I told her and I told her she shouldn't have skipped her last sleep break," Abdul said. "Maybe she'll listen to you and take one this time."

  "Seiko, my dear." Cesar's deep brown eyes showed concern. "You have driven yourself much too hard. Please take a rest."

  "Doctor Wong, I appreciate your concern. But I am not about to abandon my professional responsibility at this critical juncture."

  "Well—at least take a break and join with me in a cup of hot coffee in the galley." Dr. Wong took the petite scientist gently by the arm. She allowed herself to be steered down the passageway to the bottom deck. On the way through the middle deck, they passed Amalita and Pierre working the communications console that talked directly to the cheela through the laser communication link.

  Pierre was stretched out in free fall, his head and arms inside the communications console, while Amalita was talking to the cheela on the star. The speaker was not a computer-slowed image of a real cheela, but the real-time image of Sky-Teacher, a special purpose intelligent robot that the cheela had built for the job of communicating with the slow-thinking humans.

  Pierre was replacing the HoloMem crystal in the side of the communications console. He reached in and removed the small three-sided cover shaped like the corner of a box. The outside was jet black, but the inner surface was a corner reflector of brilliantly reflecting mirrors. He pushed a button and a clear crystal cube about five centimeters across popped out into the room, rotating slowly from the force of its ejection. Pierre left it in midair as he placed another cube into the memory cavity and replaced the mirrored cover. Then he floated over to catch the cube. The corners and edges of the HoloMem cube were jet black, but through the transparent faces could be seen flashes of rainbow light from the information fringes stored in the interior.

  06:13:54 GMT TUESDAY 21 JUNE 2050

  Leaving Amalita talking to Sky-Teacher, Pierre grasped the HoloMem cube at opposite corners and followed Doc and Seiko through the passageway in the floor to the lower deck and pulled himself over to the library console. He moved carefully, for between two fingers he was carrying all the wisdom that the cheela had accumulated during the past thirty minutes. He placed the crystal in its scanner cavity in the library console, fitted the brilliantly polished corner segment into place, and closed the lid.

  Sky-Teacher had said that this latest HoloMem crystal held a large section on the internal structure of neutron stars. Pierre had the computer jump rapidly through the millions of pages until he found a detailed cross section of the interior of Dragon's Egg. The diagram showed that the star had an outer surface that was a solid crust of nuclei: neutron-rich isotopes of iron, zinc, nickel, and other metallic nuclei in a crystalline lattice, through which flowed a liquid sea of electrons. Next came the mantle—two kilometers of neutrons and metallic nuclei in layers that became more neutron-rich and dense with depth.

  The inner three-fourths of the star was a liquid ball of superfluid neutrons and superfluid protons.

  Pierre scanned the next page, a photograph of a neutron star, but it wasn't Dragon's Egg. He could tell it was a real photograph, since he could see a portion of a cheela on a space flitter in the foreground. His eyes widened and he rapidly scanned page after page. There were many photographs, each followed by detailed diagrams of the internal structure of the various neutron stars. They ranged the gamut from very dense stars that were almost black holes to large, bloated neutron stars that had a tiny neutron core and a white-dwarf-star exterior. Some of the names were unfamiliar, but others, like the Vela pulsar and the Crab Nebula pulsar, were neutron stars known to the humans.

  "But the Crab Nebula neutron star is over 3000 light-years away!" Pierre exclaimed to himself. "They would have had to travel faster than the speed of light to have gone there to take those photographs in the past eight hours!"

  A quick search through the index found the answer.

  FASTER-THAN-LIG
HT PROPULSION—THE CRYPTO-

  KEY TO THIS SECTION IS ENGRAVED ON A PYRAMID

  ON THE THIRD MOON OF THE SECOND PLANET OF

  EPSILON ERIDANI.

  There followed a long section of encrypted gibberish.

  In near shock, Pierre set the library console for automatic transfer of the data to St. George and slowly floated over to the nearby lounge at the center bottom of Dragon Slayer. Everyone but Amalita was there. Doc was trying to talk Seiko out of taking some W.A.K.E. pills with her coffee, and Abdul was telling Jean Kelly Thomas about the recent restoration of the Holy Temple as she gulped down a quick breakfast after her shortened sleep period while trying to comb out the snarls in her short cap of red hair at the same time. While Jean and Pierre had been asleep, the cheela had advanced from their first orbital flights around their home world to intergalactic travel.

  Everyone was sitting on the soft, circular lounge seat, held there by the low outward-going residual gravity forces. Occasionally one of them would look out the viewport below his feet. Pierre jumped up to the top of the lounge and held onto the handle in the hatch door leading to one of the six high-gravity protection tanks built into the center of the ship. He too

  looked down and out the one-meter diameter window set in the "south pole" of the spherical spacecraft. The electronically controlled optical shutter had been set to blacken the port thirty times a second as each of the six glowing compensator masses passed in front of the port. The only light that entered the window came from a single intense spot that was Bright—the Sun, their home—2120 AU away.

  Pierre broke the silence. "It's nearly time for us to leave," he said.

  Jean looked up, her perky freckled nose wrinkled in puzzlement. "I thought the plan was for us to stay down here for at least another week."