Reader's Department: THE ALTERNATE VIEW: OPUS 150: DARK FORCES IN THE UNIVERSE by John G. Cramer
This column is a milestone. In 1983, while I was on a one year sabbatical at the Hahn-Meitner Institute for Nuclear Physics in what was then West Berlin, I received a letter from Stan Schmidt informing me that Jerry Pournelle had decided that he no longer wished to be an Alternate View columnist for Analog and asking if I was interested in taking over as the AV columnist and “alternating” with G. Harry Stine.
This was a problem. At the time I had written about 80 papers for physics journals and a few science-fact pieces for Analog, but I was well aware that writing science fact for a popular audience is harder and more time-consuming than it looks, and the idea of having to produce a sensible column for every other issue of Analog on a regular basis was scary. I was not at all sure that I would have anything to write about when the deadlines came around. But I decided that the Analog soapbox was too tempting to pass up.
Fast forward to today. This is column number 150. Somehow, for over 25 years I have managed to meet each deadline with something (I hope) interesting to say about science in general and physics in particular. I think that popularizing science and making it accessible to interested readers is an important activity, and I hope you agree. With that said, let's consider the subject of this column: possible indications of a new “dark” force in the universe.
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It is now clear that our universe is a much stranger place than we had imagined only a decade ago. Its total mass-energy, according to our best cosmological models, divides up as 70% dark energy, 25% cold dark matter, 4% free hydrogen and helium, 0.5% stars (mostly hydrogen), 0.3% neutrinos, and only 0.03% atoms of elements heavier than helium, the stuff that we are mostly made of.
Dark energy, easily the most mysterious of these components, is an intrinsic energy of space spread uniformly through the universe and possessed by each otherwise completely empty volume of space. It creates a repulsive “pressure” that is accelerating the expansion of the universe. Dark matter, the next most mysterious, is some unknown form of mass that does not make or absorb light and interacts gravitationally with itself and with the normal mass of stars. Dark matter clusters around galaxies in a more-or-less spherical “halo,” accounts for most of the galactic mass, and causes stars in the outer reaches of a galaxy to orbit the galactic center much faster than they would in the absence of the dark matter halo.
But what is dark matter? It is definitely not ordinary matter (atoms, molecules, electrons) or any of the known fundamental particles including neutrinos. So what's left? Nothing ordinary, so we are pushed into speculating that dark matter is made of a previously unknown family of particles. Some theories that attempt to extrapolate beyond the standard model of particle physics predict new particles: e.g., supersymmetric particles, WIMPs, axions, etc. For the purposes of this column, we'll refer to them all as DMPs (i.e., dark matter particles).
How do you look for DMPs? There are basically two techniques: (1) We assume that a speeding DMP can collide with a normal nucleus, giving it enough recoil energy and momentum to trigger a sensitive detector, and (2) We assume that DMPs come in matter and antimatter flavors that can annihilate with each other and produce radiation detectible with sensitive instruments in space. Both types of DMP searches have been going on for some time, and are getting results that are both interesting and confusing.
Gran Sasso, located about 130 km from Rome, is the highest mountain in the Apennines of Central Italy. In 1995, twin highway tunnels connecting Rome to Teramo were cut through the mountain, and at the same time an underground particle physics laboratory was created there, consisting of three large underground low-background chambers shielded from cosmic rays by 1,400 meters of rock. In one of these chambers is the DAMA/LIBRA experiment, operating a cluster of sodium iodide detectors with a total mass of 250 kg (1/4 ton), designed to detect small signals arising from the collision of a DMP with a nucleus. When a nucleus recoils from a DMP hit, a small flash of light is made by the resulting ionization, and this light flash can be detected with photomultiplier tubes. The DAMA detectors can observe such signals over background with energies as small as two thousand electron volts or 2 keV (here keV means kilo electron volts, the quantity of energy needed to move one electron across a potential of 1,000 volts). DAMA has a lower threshold than that of most competing DMP searches. DAMA/LIBRA and its previous incarnation as DAMA/NaI have been operating in the very low-radiation Gran Sasso environment for a total of 11 years. During this long period of operation, some interesting and controversial data has been collected.
In its yearly orbit around the Sun, the Earth has a speed of about 30 km/s. Our sun orbits the galactic center with a speed of about 220 km/s. If our galaxy is embedded in a cloud of DMPs more or less at rest with respect to the galactic center, the Earth passes through the DMP stream with a varying speed. At some times during its orbit, the Earth's speed adds to the Sun's speed, and at other times it subtracts. Thus, the DMPs streaming through the DAMA/LIBRA detector are expected to hit the detectors with more energy in June than in December.
Therefore, one of the signals examined by the DAMA/LIBRA collaboration is any annual variation in the counting rates in the detector, and indeed they have found such a variation at about the 2% level in counts with energies between two and four thousand electron volts (2 to 4 keV). As expected, the signal reaches a maximum around June 2, just when the Earth and Sun speeds add. The variation has a period of exactly one year with a 0.2% uncertainty. They attribute their observations to the presence of DMPs in the galactic halo and ascribe a confidence level of 8.2 standard deviations to their result.
The problem is that other similar DMP detectors (Zeplin III, CDMS 2008) with a different detection medium and higher energy thresholds see no such effect. Also, the 2-4 keV signals seen by DAMA/LIBRA are lower in energy than is theoretically predicted for DMP-nucleus collisions. Therefore, the DAMA/LIBRA result has been the subject of debate and controversy at several recent international conferences.
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As mentioned above, the other way of searching for DMPs is to look for space radiation produced when somewhere a DMP and anti-DMP annihilate. One particle expected from such annihilations is the positron, the antimatter twin of the electron. The PAMELA detector, launched on a Russian satellite by the WIZARD collaboration, has recently reported an observation of the ratio of positrons to (electrons + positrons) in the energy range 1.5 to 90 GeV. (Here, 1 GeV is 109 eV; for reference, a proton has a mass-energy of 0.938 GeV.)
The theoretical expectation is that such energetic positrons should be produced mainly in gas collisions during the propagation of cosmic ray protons in the galactic medium, and this leads to a positron ratio that should fall steeply with energy. The actual data, however, shows a strong increase in the ratio with energy, starting at a value of about 0.05 at 10 GeV and rising to above 0.15 at 90 GeV. There are similar reports of a positron excess in the 600-800 GeV range from the balloon-borne ATIC cosmic ray detector, but these seem to be in conflict with recent GLAST/Fermi results. This excess of energetic positrons is not easily explained, and could be the result of DMP-anti-DMP annihilation.
The WMAP experiment, which has mapped the cosmic microwave background with great precision, has also reported a hard microwave “haze” coming from the center of our galaxy, not readily explained by known galactic emission mechanisms. This haze could be the synchrotron radiation from energetic electrons and positrons made in DMP-anti-DMP annihilation near the galactic center. Studies there with the EGRET gamma ray detector showed an excess of gamma rays at energies above those expected from pi0 meson decays. It is suggested that the observed gamma rays might arise from the inverse Compton scattering of energetic positrons and electrons colliding with starlight and cosmic background microwaves.
Thus, from several independent sources there is evidence of energetic electrons and positrons, possibly coming from DMP-anti-DMP annihilation. On the other hand, there is no corresponding evidence of any excess of strongly interacting particles like pions and antiprotons, which would be expected from conventional matter-antimatter annihilations. In particular, the PAMELA measurements place tight limits on the antiproton content of cosmic rays, and EGRET measurements place similar limits on gamma rays from pi0 meson decays. Neither provides any indication of strongly interacting annihilation products.
These results present a paradox. If DMP-anti-DMP annihilations are producing electrons and positrons with energies of 90 GeV or more, why are these decays not making any excess of antiprotons or pi0 mesons? This is in direct conflict with expectations based on the standard model, so the observations may point to new physics beyond the standard model.
One version of such new physics has recently been suggested by Arkani-Hamed, Finkbeiner, Slatyer, and Weiner (AFSW). They propose a new “dark” force that acts only between the dark-matter particles. In this AFSW model, when there is a DMP-anti-DMP annihilation between dark matter particles that wander into each other, the particle momentarily produced in annihilation is the carrier of the new dark-matter force. And it is assumed that the force-carrier particle has a mass of around 0.1 GeV, so that its low mass constrains its subsequent decay into electron-positron pairs and/or pairs of gamma rays.
Also, because of this new force, as the particles approach each other before annihilation, an attraction due to the force occurs that increases the probability that the annihilation will occur. This is called a Sommerfeld enhancement, and it can increase the chances of annihilation by several orders of magnitude. And the AFSW model predicts that DMPs should interact primarily with heavy nuclei, giving lower recoil energies, explaining why only detectors containing iodine (like DAMA) or lead nuclei show small but detectable recoil signals.
The AFSW theory can, at the expense of postulating a new and previously unknown force, explain all of the observations described above and make predictions that can be tested by new experiments and observations. In particular, the AFSW theory predicts that, as more data is collected, the positron enhancement observed by PAMELA should continue to increase up to the highest energies that the detector can resolve (~270 GeV). As the sources of positrons become better localized in position, the theory predicts that sources of the energetic positrons should be broadly distributed rather than localized at the galactic center (e.g., at the black hole there).
When the LHC begins operation in a few months (a year late because of a major cryogenics rupture) the AFSW theory predicts observation of a striking signature of highly energetic electrons and positrons among the produced particles in the proton-proton collisions. There are also predictions for new observations from the GLAST/FERMI and HESS detectors that have recently been launched.
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What are the science-fiction implications of all this? If the picture painted by the AFSW theory is correct, the matter content of the universe is mostly dark matter with its own particles, forces, and interactions. It clusters around galaxies in a somewhat different way than do the stars and planets of normal matter, and it may have complexities and structures that we have not imagined. Are there the equivalent of atoms and molecules made of dark matter that are invisible to us except through their gravitational interactions? There are almost no antiprotons in our galactic neighborhood, but apparently there is plenty of dark matter and antimatter. Can we find chunks of dark matter and dark antimatter and annihilate them for energy and propulsion?
So there may be another force in the universe, a fifth “dark” force that acts only between “dark” particles that ignore us as we ignore them, passing invisibly through our stars and planets as if they were not there.
The surface has just been scratched in this area. For science fiction this has the makings of new kinds of energy sources and propulsion, and perhaps even a new “dark’ territory to be explored by space travelers.
Copyright ? 2009 John G. Cramer
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AV Columns Online: Electronic reprints of over 145 “The Alternate View” columns by John G. Cramer, previously published in Analog, are available online at: www.npl.washington.edu/av.
The AFSW Theory:
N. Arkani-Hamed, D. P. Finkbeiner, T. R. Slatyer, and N. Weiner, “A Theory of Dark matter,” Physical Review D79, 015014 (2009), arXiv preprint 0810.0713v3 [hep-ph].
Short Story: THE UNIVERSE BENEATH OUR FEET by Carl Frederick
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Illustration by John Allemand
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How you see the world depends on how you look at it....
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he disturbance in the ice perturbed the funeral.
Despite the grinding sounds from the ice beneath, Jerik chirped his attention on Harshket, the High Priest of the People of the Rippling Wall. The priest, four feet planted firmly on the ice, raised his other two to heaven and commended the recently deceased Master of the Fourth School to the Great God, the god of water, the god of good.
A few feet in front of the priest, that Master of the Fourth School, his life-bubbles still pressing him to the ice, lay motionless. On a circle centered on the priest, six of the people, the Beaters to Heaven, stood at the six points of the compass. And behind them, outside another circle, waited the mass of the people—including Jerik. Though he listened to the priest's words (he could hardly do otherwise), he ping-chirped very little; he didn't really care to register the details of the priest's movements. And standing behind Jerik, his friend K'chir ping-chirped not at all. Jerik could hear the tapping as K'chir sequentially raised and lowered his feet in obvious boredom. The Master of the Fourth had been K'chir's master. Jerik knew the two didn't like each other and K'chir wasn't exactly crushed at the loss. Jerik sighed. He was still only in Third School. All he could do was hope.
At length, the priest lowered all six of his legs to the ice and addressed the inner circle. “Beaters,” he intoned, “do your sacred duty. Drive the god-given life-bubbles from the deceased. Beat him well and true, and enable him to rise swiftly to join the Great God of the Water. Let the deceased rise far from the evils of the world and from the evil presence of the God of the Ice."
"Finally!” whispered K'chir. “I thought Harshket would never stop babbling."
Those standing in the inner circle clattered somberly to the corpse. Each raised two forward legs above the body and, at a chirp from the priest, brought them down and began pummeling the ex-Master of the Fourth.
A trickle of bubbles dribbled from the master's mouth and collected in a clutch on the ice. Additional life-bubbles, tiny but numerous, shook free from the master's body and leg fur, carpeting the ice and softening the ping echoes.
Ping-chirping steadily now, Jerik observed the beating. He was surprised how few life-bubbles the master had possessed. But then again, the master was very old. And for the most part, vitality equated to how strong one's contact with the ice was—and that depended on one's supply of bubbles. A shift of the current brought Jerik the scent of the corpse—a terrible smell of death. Jerik blew out water in revulsion.
The priest gave a sharp chirp and the Beaters to Heaven moved back, causing the corpse, lighter without its bubbles, to twitch in the current. All was quiet, except for a susurrus of respectful chirping—and the constant grinding from the ice. Jerik could tell from his pings that many of the people resented the grinding and groaning from below. He knew though, that K'chir was far from annoyed; he was excited that there might actually be a release from the constant boredom.
Very slowly, the Master of the Fourth began to rise.
Ping-chirping in respect, Jerik observed the body rising faster, gently twisting and rolling in the current. Jerik breathed in relief as the death smell faded.
Jerik added to the wall of sound as the people, as a whole, ping-chirped the deceased, following the body to heaven with their chirps. As the body progressed steadily higher, the chirp echoes grew ever more faint, until they ceased altogether—until all that remained of the Master of the Fourth was a thin lake of air on the ice, the merged totality of the master's life-bubbles.
"Well, that's over,” K'chir whispered from behind.
"Not quite over,” said Jerik.
The circle of mourners converged on the lake of air. In order of their seniority, the High Priest Harshket going first, they wallowed in the air, trapping minuscule bubbles onto their leg fur. The lake shrank until, when K'chir's turn came, there was no air left at all.
Jerik chuckled. “It's too bad, K'chir,” he said. “It would have been really funny if you'd been able to absorb some of your master's essence—considering how much you hated him."
"I don't believe in that essence nonsense,” said K'chir, turning away from the one-time air-lake. He tapped a leg in disgust. “But the air was certainly full of the master's scent. I'll survive just fine without it.” He chirped a smile. “It's air. Life-giving air, certainly, but that's all."
"It's God's gift,” said Jerik.
"Come on!” said K'chir. “I don't believe in any such god."
Jerik winced. He didn't believe either, or at least didn't think he believed, but saying so aloud was not wise.
"Let's get out of here,” said K'chir. He and Jerik began to glide away, but the High Priest held up two legs.
"K'chir. Please wait until the others leave.” The priest spoke in a voice that was threatening despite the courtesy. “I want to talk to you."
K'chir stopped, but Jerik, as quietly and unobtrusively as he could, continued to glide away.
"And you,” said the priest. “Jerik, by your smell."
Jerik stopped abruptly. “Yes, sir?"
"Stay!"
"Yes, sir.” Jerik glided back to Harshket. He waited nervously with K'chir as the chirps from the people faded away. Then Harshket, without preamble, said, “K'chir. Do you know the Six-fold Way?"
"Of course, I do. Every First School student learns it on the first—"
"Recite it,” Harshket demanded.
"Why?"
"Recite it. Now!"
Jerik heard K'chir tap a leg in a quiet shrug.
"All right,” said K'chir in a voice at the border between polite and put upon. “The qualities of the People of the Rippled Wall are: Obedience.” He stamped his front left leg to the ice as custom required. “Loyalty.” He stamped his front right leg. “Honesty. Knowledge. Wisdom.” At the mention of each quality, he stamped another leg. “And Reverence,” he intoned, stamping his sixth foot.
"Do you think you exemplify these sacred qualities?” said Harshket.
K'chir stood silent.
"From your comments that I and no doubt many others of the people heard,” said Harshket, “I rather think you fail with regard to Reverence, the highest of the qualities."
"I'm not sure I am fully a believer,” said K'chir. Jerik noticed that his friend was being a lot more tentative than usual.
"Not sure?” Harshket raised his forward legs in the air and chirped, the rasping chirp of the elderly. “Can you not detect the sweet manna sent down from heaven by our kind and all-powerful god?"
"Maybe...” said K'chir in a cautious, even frightened voice. “Maybe the manna from heaven is just the dead—decomposed and sent back down to us."
"Nonsense!"
Jerik felt the turbulence of the current reflecting Harshket's anger—and then the turbulence subsided.
"Who, K'chir, do you think does the sending?” Harshket spoke in the voice of a philosophy master, which, of course, he was.
"The same one who sends down those,” said K'chir. He pinged a stream of sulfur-bubbles coming from on high. “And why would God send down foul-smelling, inedible life-bubbles that burn our bodies?"
"To test our faith, of course. You know that.” Harshket spoke as if he were addressing young children.
Jerik moved his mandible in a soft, unpingable show of amusement. Of course, to old Harshket, everyone was surely a child.
"You are in Fourth School—Collective philosophy,” said Harshket, wearily. “Collective! Do you think you're setting a good example for your young friend who is only, if I recall correctly, in Third School—Deductive philosophy?"
"I think, sir, I am setting a good example. At least I'm trying to."
"Then you fall short in the quality of Wisdom as well."
Jerik sensed his friend bristle.
"Yes, I accept the Six-fold way,” said K'chir. “But there are qualities it leaves out. What about Innovation? What about Adventurousness?” He chirped a sigh. “I'm so bored."
"Ah, so that's it.” Harshket chuckled and Jerik breathed easier. He'd been worried his friend had been pushing the priest too far.
"Adventurousness,” said Harshket, thoughtfully. “We have ice-gliding races, wrestling, debate rallies. Compete! That should address your boredom. Or perhaps you might study harder."
"I'm bored with all our rituals and traditions,” said K'chir. “I want to create, to innovate."
"Me too,” said Jerik, wanting to get into the game, now that High Priest Harshket seemed more disputative than angry.
"You are a mere juvenile, Jerik!” said Harshket, in a voice near anger. “And so young that your voice is almost as high pitched as your ping-chirp."
"Yes, sir.” Jerik thought deference the safest course at the moment.
Harshket chirped a sigh. “And as to you, K'chir. You must wait until the Sixth School—Transcendental philosophy. Your time will come."
"Maybe our culture has gotten too old.” K'chir lowered his head and soft-pinged the ice in an expression of sadness. “During our creative period, when we should be advancing the art, we're still learning what has gone before—studying philosophy, memorizing poetry.” He chirped frustration. “And even then, we study narrower and narrower specialties until we cannot any longer see the whole. True innovation is impossible."
"That is known,” said Harshket. “It is a sign that God's work for his people is almost done."
Jerik was afraid that would set his friend off, would make him say something he'd regret. But K'chir merely said, “I want more in life."
"More?” Now Harshket sounded angry. “Just what do you young people want?"
"For one thing,” said K'chir, “true knowledge."
"Meaning what?"
"Well...” said K'chir in a light tone. He'd apparently also detected the edge in Harshket's voice and knew it could mean danger. K'chir pinged the ice. “I'd sort of like to know what that grinding beneath the ice is."
Clearly, K'chir was trying to lighten the mood.
"Things have come up through the ice before.” Harshket's voice sounded troubled.
"They have?” said K'chir in a curious tone with no trace of challenge.
"You will learn about it in Fifth School next year."
"Please, sir,” said K'chir, “would you tell me about it now?"
Harshket made a throaty chirp toward the ice and said, “It happened many great-tides ago.” He spoke in a distant voice. “This thing came up through a fissure—a crack in the ice after a heaven-quake. And the thing came into the world upside-down. It had four feet rather than six. The feet pointed heavenward—a clear sign that it came from the God of Evil and Ice."
Harshket chirp-mapped the thing slowly and in exquisite detail. It took Jerik's breath away. The thing from the fissure had thin legs, rodlike with pads for feet. And it had a body with more rods sticking out nonsymmetrically from all sides. It seemed alive: a small shell-like object on its head swiveled back and forth, and it virtually reeked with frenzied electromagnetic waves. All this did Harshket transmit through a chirp-map, crisp and precise as if the priest had only encountered the object at last tide.
"And it rose toward heaven,” Harshket continued. “Rapidly. Aggressively. It could be nothing else but the Ice God's demon rising to challenge the Great God."
Jerik felt the shimmering currents of Harshket's shivering limbs.
"Ice God, Great God,” said K'chir in a voice of ridicule. “Well, I don't believe it."
"You are flirting with sacrilege, young man,” said Harshket. “You of course know that people have fallen into fissures and have been pulled down into the realm of the Ice God."
"Down into the ice. Yes."
"They never came back,” said Harshket with raised front legs. “Never!
K'chir chuckled and Jerik marveled at his friend's courage—or foolishness.
"So is that what the grinding sound is?” said K'chir. “The Ice God coming to visit?"
"In a manner of speaking, it is,” said Harshket. “It can only be the Antigod trying to break through because of the immorality and evil in the land."
"Well, I think,” said K'chir, swirling the water with a leg, “that there's another world beneath the ice."
"Ridiculous,” Harshket uttered a disdainful chirp. “You'll understand when you reach Sixth school."
"I'll never understand. I believe it is another world."
"If you are so contemptuous of philosophy, then tell me: How, other than going through a fissure, could the dead from this ... this other world reach heaven?"
"It could be,” said Jerik, attempting to gain points with both his friend and the priest, “that we're chosen by God to be the guardians of heaven."
K'chir as well as Harshket returned a dismissive chirp.
"Or," said K'chir, “maybe there is no heaven and no god."
Jerik suppressed a gasp.
"Sacrilege!” Harshket roiled the water and then paused until the currents grew calm. “I must deliberate on this,” he said in a voice of cold anger. “At first tide, come to me. I believe you must be corrected for your crimes against God. Both of you come."
Without another word, Harshket turned and scuttled away.
K'chir, with an audible scowl, glided away and Jerik glided after him.
"What will he do to us?” asked Jerik.
"He'll beat us, of course.” K'chir chirped toward the Rippled Wall and the two glided in that direction. “Me for sacrilege and you for hanging out with me.” After a few seconds, K'chir added, “He'll beat me more than you.” Jerik sensed the currents as K'chir shuddered. "Much more than you.” He sped up.
"Where are we going?” Jerik struggled to keep pace.
"I'm not going to stick around and let myself be beaten in front of all the people."
"You're not going to run away to another people,” Jerik called from behind, “are you? It won't really do any good. It'll be just the same.” Jerik shook in the turbulence of K'chir's wake.
"No,” said K'chir without slowing down. “I'm going to prove philosophy is garbage and Experimentation is truth."
"What are you talking about?"
"I will prove that this god stuff is nothing but myth,” said K'chir, breathlessly. “I am going to climb to the so-called heaven and look around."
"What!” Jerik grabbed his friend and the two spun around on the ice as if they were dancing. “You're joking."
"I'm serious."
Jerik dug the rough sides of his legs against the ice and their spinning slowed to a stop. He addressed his friend mandible to mandible. “They'll kill you for this."
"If God actually exists,” said K'chir in an annoyingly logical voice, “then when I go down to the ice again, yes, they might kill me. But then I'd just float back up to God. He'll punish me, perhaps. But he's supposed to be good and kind. So, I expect his punishment will probably not be too bad. And anyway, I really want to know if there actually is a god."
"Have you been sipping sulfur-bubbles?"
K'chir chirped a weak smile and went on. “But then if, as I believe, there is no god—well, Harshket can tell if people are lying. He'll know I'm telling the truth, so there'll be nothing he can beat me for.” K'chir clicked his mandibles, smugly.
"But climbing to heaven?” Jerik threw an exasperated ping upward. “That's impossible!"
"Why?” K'chir pinged in the approximate direction of the Rippling Wall, but they were too far away for an echo. “In bad times, the people had to climb ever higher for the edible growths on the rocks. That was long before you were born—before I was born either. That was before the people had learned to stabilize our population by rationing life-bubbles.” He started gliding again toward the wall. “So I'll go to a wall and climb higher—to heaven ... to see what's there."
"What's there?” Again Jerik strove to keep up. “It's friggin’ heaven! Are you so eager to die?"
K'chir sighed. “I'm bored to death already."
"Well ... well maybe the grinding in the ice will turn out to be something interesting. Maybe it's the thing Harshket saw."
"And maybe it isn't. I don't want to wait anymore. I'm climbing."
"I'm coming with you,” said Jerik, firmly.
"What?” K'chir braked to a stop. “No. Finish school. Maybe Sixth School will have answers—at least for you."
Jerik stiffened his legs, drawing himself to his full height. “I'm coming with you!"
"This is very, very dangerous,” said K'chir. “I'd rather you didn't do it."
"Don't make me say it again,” said Jerik.
After a few seconds of exploratory chirps, K'chir crossed his forward legs in acceptance. “Fine. Then come.” He started away but then turned. “And thanks. I appreciate your company."
K'chir leading, they headed toward the Rippling Wall, guided first by magnetic fields, then by chirp echoes, and finally by the smell of the stone.
With ping and claw, they explored the base of the wall, looking for a cleft, a place with good leg holds.
"How about this one?” said Jerik.
K'chir scuttled over. “It is good, very good."
Jerik began to climb.
"No, wait,” K'chir called. “Let's rub down our legs and bodies first. To strip the life-bubbles from our fur."
"Why?” Jerik wasn't crazy about the idea. Life-bubbles were precious.
"To make ourselves lighter,” said K'chir with a chuckle. “Not so light so we'd rise. We'd have to be dead for that.” K'chir began wiping away the bubbles. “But if we fall, we'll hopefully drift slowly down to the surface and not hurt ourselves on the ice."
"Hopefully!” Jerik also pressed down his fur, leaving a small lake of air on the ice. “But we'll roll around in the bubbles when we get back. Right?"
"Of course!” K'chir began climbing.
Jerik followed after. “I guess,” he said as he pinged the rock face, “if God didn't want us to climb to heaven, he wouldn't have provided footholds."
"Unless,” said K'chir, “he was testing our faith.” By voice alone, Jerik could tell K'chir's mandible was extended in amusement.
Using the cracks in the rock and the purchase afforded by the thick growths of edible molds clinging to the walls, K'chir and Jerik made quick progress. “At least we won't starve,” said Jerik. He grabbed a snack from the wall. “But, boy, heaven is high!"
"Don't call it heaven."
"What should I call it, then?” said Jerik, breathing heavily.
After a few more vertical feet, K'chir answered. “There doesn't seem to be another word. But when you say it, try to keep the reverence out of your voice."
"Yeah. Sure. Fine."
"Is it getting warmer?” K'chir asked. “Or is it just the exertion."
"I think it is getting warmer. Heaven is supposed to be warm.” Jerik moved a leg out into the current. “Yeah, it's warmer, but the current seems stronger too."
As they climbed, the growths grew sparser. “Well, there goes lunch,” said K'chir.
The wall became smoother. “I wonder if the molds made the footholds,” said K'chir. “Maybe the molds eat the rock."
"I'd really like some of those faith-testing cracks right now,” said Jerik, breathlessly, trying with all his strength to cling to the wall.
The climbing became very hard and slow, and the wall had begun to slant inward.
Jerik cried out.
"Don't ping down!” K'chir commanded.
But Jerik had so pinged and now felt a queasy vertigo. And then came a sharp current, a tide. One part of his mind knew it was the first tide, the one at whose occurrence Harshket had demanded their presence. Partially distracted as he was, Jerik released a leg and rubbed it thoughtfully across his torso. His body shifted, and with a shriek, he began to fall.
K'chir reached a leg down. “Grab hold!” he shouted.
Jerik pinged, then leapt for the proffered limb and grabbed it with his two forward legs.
K'chir grunted in exertion. Then Jerik felt himself falling again, while he still had hold of K'chir's leg.
"Hey!” K'chir exclaimed in a cheerful voice. “This is great! Wiping off our life-bubbles worked."
After a short, panicked pause, Jerik said, “Yeah, it did!” His dread had turned to elation as he felt himself not falling, but drifting softly down to the ice. Now, without fear, he ping-chirped down. “Uh-oh!"
"What's the matter?” said K'chir.
"On the ice,” said Jerik. “Three, maybe four sixes of people."
"And it is first tide, isn't it?” said K'chir, in obvious worry.
"I'm afraid so."
Jerik ping-chirped. “And there he is,” he said with an anxious sigh, “the High Priest himself."
"Then this is it,” said K'chir. He began ping-chirping an alert in all directions.
"What are you doing?"
K'chir paused his chirping to say, “Bringing out the people, at least the young people—I hope."
Jerik and K'chir floated down while drifting laterally in the current. Those below arrayed themselves in a circle and moved to keep the floaters directly above its center. The High Priest, Harshket, positioned himself at the center of the circle.
Jerik and K'chir hit the surface, bounced a few times, and then settled onto the ice. Jerik felt light, ungrounded, and insubstantial. He wished he'd had time to roll in his life-bubbles as was K'chir's plan.
The circle collapsed in on them.
As Jerik and K'chir found their footing, Harshket came up to them.
"Um...” said Jerik. “Well ... as you requested sir, we're here."
"You!” said Harshket, pointing at the Third Schooler. “You have been cast down from heaven."
"No, sir. We just fell off the wall,” said Jerik. He heard a soft moan from K'chir.
"Just as I suspected,” said Harshket. “You have attempted to violate the sanctity of God's domain."
Jerik hung his head. It was impossible to lie successfully to Harshket, or to any priest, trained as they were in the pursuit of truth. In the ensuing silence, Jerik heard the distant soft buzz of massive chirping; apparently K'chir had been successful in turning out the people.
"You must realize, Jerik,” said Harshket in a deceptively soft voice, “how serious an offence this is against God. You must be punished for your horrid deed."
Jerik didn't answer, but K'chir did. “If he offended God, then why not leave it to God to punish him?” Jerik knew K'chir was merely trying to help, but he wished his friend had kept his silence.
"As you were not the instigator, Jerik,” said Harshket, ignoring K'chir, “you will simply be beaten—and forgiven."
"Thank you, sir.” Jerik hated himself for giving the required response. He felt the ripple of current as the priest turned to K'chir.
"But for you, K'chir, there is no earthly redemption."
Jerik sensed his friend go as motionless as a rock. A few of the people chirp-mapped, but mostly the water was silent—save for the constant grinding from beneath the ice.
"For the crime of sacrilege,” Harshket intoned, “your life-bubbles will be beaten from your body and your body will rise to heaven. Far better that than cede your immortal soul to the Antigod."
"No!” came a voice from the people. It sounded like a student in the Fourth School.
"Life-bubbles are a gift from God!” Harshket raised his voice over the cries. “You are not worthy of them. But for your redemption, your precious life-bubbles will be your contribution to your people—allowing another of our people to be born. I and the people thank you for your sacrifice."
Angry shouts of “No” came from many youths in the crowd.
"This is an important lesson for the people,” Harshket shouted over the protests. “In fact—in fact so important that the punishment and sacrifice will be administered in the presence of the Antigod himself.” He paused as if for effect. “To show our contempt for him."
Like a tide, an expectant hush washed over the people, broken only by the sounds from under the ice.
"Where the hellish noise in the ice is the loudest,” shouted the priest, “there, we will go to confront the God of Evil.” He paused. “We are not afraid!” he intoned as a chant. He hesitated as if expecting the people to pick up the chant, but the people only ping-chirped. Then in a quiet voice Harshket said to those around him, “Attend that the malefactors do not flee."
Jerik felt himself grabbed by many limbs and propelled toward the grinding sounds. He could tell by the smells that his captors were old people. The trip to the center of the noise was a delay of his punishment, and Jerik was grateful for that. He wanted to say something comforting to K'chir but couldn't think of anything that wouldn't sound banal.
At a point where vibrations shook the ice and the din had grown to a muffled roar, Harshket called for a halt. “Here,” he shouted over the subsurface rumbling, “we will display our contempt for the God of Evil.” He turned to Jerik. “We'll start with you.” He chirped a superior smile. “Be thankful that in your case, it will just be a beating.” Clearing his voice with a grunt, he turned to K'chir. “And then we can attend to the more serious matter.” Again, he addressed the people as a whole. “Let this be a lesson to our young people."
Harshket gave the order and six of the people stretched Jerik out on the ice. The ice, quivering and groaning, seemed to be foretelling Jerik's fate, and he winced in anticipation. Suddenly, he had a renegade notion: he wasn't going to just lie there and take it. He'd taken enough. He'd fight, struggle, try to break free.
But just as he began kicking, he heard a great crash. Then a turbulence in the water pulsed across his body. His legs easily broke free, or maybe were released. He scrambled to his six feet, then ping-chirped—one voice in a sea of pings—and found that something had broken through the ice. Repeatedly then, he chirp-mapped, sacrificing spatial resolution for temporal, and detected an object rising from a tumble of ice fragments. The object appeared similar to the four-footed thing that Harshket had maintained was a demon from the Ice God. Jerik shivered. Could The High Priest have been right?
Jerik, chirp-mapping steadily, couldn't actually tell if the thing did indeed have four feet, for it had stopped midway in its emergence from the ice. But in any case, it was huge—far larger than the thing Harshket had observed. It was clearly a thing of design, of purpose. And it was awash in electromagnetic fields.
Jerik heard K'chir come to his side.
Suddenly the thing emitted a hissing sound, and then Jerik heard the sounds of falling bubbles and the smell of them reached his nose: life-bubbles, and they smelled pure and sweet. The hissing grew stronger and the trickle sounded now like gushing torrent. Jerik chirp-mapped faster and observed the bubbles cascading down from a crack in the object and forming an air lake around the object's base. He gasped as he understood the significance. Then he heard K'chir gasp as well.
"Observe!” K'chir shouted to the people. “If life-bubbles come only from the Great God, this device cannot be a thing of evil. It cannot be a surrogate of the Antigod."
Jerik heard chirps of agreement.
"What is its purpose, I wonder,” Jerik whispered.
"Maybe,” said K'chir, softly, “maybe someone from another world wants to say hello. And if it does, I certainly ... What's it doing now? It's opening up."
Jerik observed what seemed to be a thin slab of ice pivoting away. “There's some sort of a ... a cave in its side."
As Jerik chirp-mapped, a roughly spherical device of some sort emerged from within the cave. It floated upward for a time then stopped. High levels of electromagnetic radiation came from small areas of the thing.
"What's going on?” said Jerik.
"I think it may be ... observing us.” K'chir scuttled up to the bigger object. “Amazing!"
"Be careful,” Jerik said at a loud whisper. He chirp-mapped furiously and observed his friend wallowing in the lake of air, his leg and body fur absorbing the precious bubbles.
"This is wonderful!” K'chir called out.
Jerik detected that the people were in a frenzy of chirping, but no one said anything, not even Harshket. Jerik turned and pinged the people. They're probably too stunned.
Then he heard a collective gasp, staggered, of course, as each of the people observed at his own map speed. Jerik swiveled back toward the object and chirp-mapped. Then he too gasped. K'chir had leaped up from the lake and into the cave-like opening in the object.
Jerik sensed a sudden increase in the electromagnetic field around the object and he began chirp-mapping as fast as he could. He observed the slab pivoting very slowly back. “Get out, K'chir,” he shouted. “Fast! The cave is closing."
"No!” K'chir shouted back. “This thing comes from another world. And I want to experience that world.” He held up his two forward legs. “I will be back!"
When the slab had completely covered the cave, the thing began to rotate. A loud churning and grinding sound filled the water and the object gradually sank down into the ice. At the same time, the floating sphere rose slowly toward heaven, increasing in speed as it went.
Almost too shocked to chirp-map, Jerik listened as the sound from the ice gradually morphed to a distant rumble and then, all at once, changed to a far off whisper. Then, abruptly, the ice went silent. Jerik felt alone. His best friend was gone. Jerik ping-chirped the hole in the ice, a perfectly circular opening, clearly not something made by nature. He chirped deep into the opening. Empty! Just water where ice had once been. And no ping echo came back from the hole. A void, nothingness!
"The Antigod has taken the heretic,” came the High Priest's voice shouted from behind. “Praise God. And take you that as a lesson."
Jerik spun around. “No!” he shouted. That's a lie.” He startled himself; he'd never openly contradicted an authority—especially not the High Priest. He turned back briefly and pinged the lake. “Those are life-bubbles. But they are not from any god."
"It is time for your beating,” said Harshket, loudly and angrily.
"I will not be beaten,” said Jerik with equal anger. He heard a chirp of support from someone he knew to be a student in the Third School. Then he heard a flurry of encouraging chirps from other Third Schoolers—and then from students in the Fourth. He felt a surge in the current as a mass of the people came toward him, chirping encouragement—just about all the school and many of the older people as well.
Then, as one, they turned on the High Priest and his cohorts.
Jerik heard Harshket's voice over the crowd. “Your beating is deferred.” The priest and his allies then scuttled quickly away.
Yes, it is a lesson. Jerik greeted his friends from the Third, and then all his new friends. Finally, feeling both light-headed and light-weight, he excused himself and glided toward the Rippled Wall—to the cleft where he and K'chir had made their assault on heaven. At the base of that cleft would be his and K'chir's life-bubbles. He would absorb them, his and K'chir's alike. Jerik extended his mandible in the realization that he'd already absorbed some of K'chir's independence and maybe some of his courage as well. He pinged upward to the rising sphere, now almost at the chirp-echo limit, and thought of his friend. Jerik vowed that he'd devote himself to the struggle for change—to assure that when K'chir did return, he'd find a different and a better world.
"Damn it!” Mission specialist Paul Hopcroft let his fist fall at 0.145 Earth gravity onto his control panel. “The observation sphere. It's sinking fast. We've lost control."
"Is it still transmitting video?” Colin called from the “pool.” Surface team leader Colin Shepherd darted toward Paul's display.
"The signal's fine.” Paul peered at the transmission, watching as the group of craboid creatures grew distant on the screen. “Damned robot! I'll take a manned vehicle every time."
"If it weren't for the unmanned Jovian I,” said Alex, the other specialist, “we wouldn't have any idea what we were doing."
Paul gave a grunt of a laugh. “You mean, we know what we're doing?"
Colin, looking over Paul's shoulder, stared silently at the video monitor. Alex also came to look, drawn away from his own monitor by the much more interesting view on Paul's.
The three wore EVA suits, but with their helmets off. A transparent dome provided them with air, pressure, and warmth—and light.
The great orb of Jupiter looming large in the ink-black sky filled the dome with reds and yellows and bathed the Ganymede ice field in an orange glow. A half kilometer away, the lander, their bus home, gleamed against the ice.
The research dome, some twenty meters across, functioned also as an ice-fishing tent. At its center was a two-meter-diameter hole in the ice, the work of the borer module. Near the hole, looking like a kids’ aboveground swimming pool, stood the Ganymede Sub-surface Environment Chamber. A transparent cover sealed it so that the pressure and temperature beneath the ice might be replicated and preserved.
"Looks to me like organized, structured behavior,” said Colin, staring at the group of craboids in the display.
"Ant colonies show that too,” said Alex.
"This looks to be a much higher order,” said Colin, softly. “I'd call it intelligence. In fact, I'd be tempted to call it sentience."
"Sentience?” said Alex. “Come on."
"I tend to agree,” said Paul. “And their rich set of vocalizations could very well be speech."
Colin blew out a breath. “Who'd have thought the first alien intelligence we'd find would be in our own solar system?"
From the corner of his eye, Paul saw motion in Alex's display monitor. Paul turned to look—as did Alex and Colin.
"Ha!” exclaimed Colin. “The critter took the bait."
Alex shook his head, vigorously. “No. I didn't even get the chance to release the bait.” He dashed back to his control panel and gazed at the monitor.
"I saw it,” said Paul. “The craboid just jumped into the chamber."
"Hm,” said Colin. “Adventurous creature, isn't he?” He turned to Alex. “Let's get him up and into the pool—that is, if we can still control the ice-borer."
Alex worked a control. “Borer's fine. I'll speed it up. We should have our six-footed friend on the surface in about twenty minutes."
"Careful not to damage the borer,” said Colin. “I want to be sure we can return the creature to its home."
"Not pickle it and bring it back with us?” said Alex.
"I'm assuming it is an intelligent being,” said Colin with a small trace of anger.
A half hour later, the three had transferred the specimen container holding the craboid from the borer to the pool. They stood watching the creature through the pool's transparent cover. The craboid scuttled, upside-down, on the inner surface of the cover.
"Natural enough,” said Paul. “Its overall density is a bit lower than that of water."
"It does look weird, though,” said Alex.
Paul stared at the meter-long and about-as-wide creature with its six furry legs and fearsome head with unidentifiable organs. “It looks a lot more imposing up close, doesn't it?"
"The cameras and probes are all on, I assume,” said Colin.
"Of course.” Alex went to his console. “And all functioning."
"I wonder,” said Paul, staring at the creature with its agile limbs, articulated nearly to the point of being tentacles, “can a sentient species exist without artifacts or opposable thumbs—or any thumbs for that matter?"
"Hard to generalize from only a single case,” said Colin. “Until now, perhaps."
They gazed at the craboid in silence for a few seconds more. Then Colin said, “I'm going in."
Paul jerked around. “What? In the pool?"
"Our friend shows a spirit of adventure,” said Colin. “Can I do any less?"
Alex came back to poolside. “I'm not sure that's a particularly terrific idea."
Colin shrugged. He retrieved his helmet and had Alex and Paul help him with it. Then, after check out, Colin leaped to the pool cover, an easy task in Ganymede's low gravity. He went to the access hatch.
"You're sure you want to do this?” said Paul over the radio link.
Colin gave a hint of a laugh. “I'd rather not think about it at the moment.” He opened the hatch, slid into the water, and closed the hatch above him. In his EVA suit, he, like the craboid, was lighter than water. Colin lay horizontal, his stomach pressed to the inner surface of the pool cover.
"They're looking at each other,” Alex whispered.
"Not exactly,” said Paul. “The creature doesn't seem to have eyes. Wouldn't need them under the ice."
Paul watched as Colin slithered close to the creature. Then, slowly, very slowly, Colin held out his hand.
"Shaking hands,” Alex whispered. “You think?"
Paul gasped softly as the creature extended a front leg, then touched Colin's hand.
"I'm willing to bet,” Alex whispered, “that this image will be on a postage stamp next year."
Paul, mesmerized, could not pull his eyes away or even answer.
After a few seconds, Colin said a ritual greeting, loudly, so it might be heard through his helmet. The creature made some sounds as well: clickings and chirpings. Then, after another brief pause, Colin and the creature withdrew their appendages. Colin crawled backwards to the hatch.
Alex shook his head. “We're going to have one hell of a story to tell when we get back."
Paul, his eyes on the craboid, said softly, “And so will he."