The answer came to Darya as she again moved her head, first to the left and then to the right, and watched the lines move relative to each other because of parallax. She suddenly knew a method — and it was irritatingly simple. Any practical surveyor would have seen it at once. It needed an imaging system and a good deal of computer power, but their suits could provide that.
“Kallik, we have to take pictures.” She paused and thought for a moment. Two images would fix position in a plane, three in space. “From at least three different positions. Let’s make it more than that, and build in some redundancy. Then we’ll need a rectification program.”
“I can certainly construct such a program. And I will also include a parameter that allows for the refractive index of the wall’s material.” Kallik responded without a pause — it confirmed Darya’s opinion; the Hymenopt was quick. She understood exactly what Darya was proposing. “The program will perform a resection and provide point positions in three-dimensional space. The primary computer output will consist of the depth below the surface of every point on every line. However, that is perhaps not what you would like to see.”
“No. I’d like the output as a set of two-dimensional images. Each different image should correspond to a prescribed depth below the wall surface. Label each one of them” — recognition of Quintus Bloom’s accomplishment and priority was no more than his due — “as a glyph.”
* * *
Kallik was quick and able as a programmer. In this case, though, she was not nearly quick enough to suit Darya. Once the digital images had been recorded and registered to each other, Darya’s role disappeared. She roamed the chamber impatiently, knowing that the worst thing she could do was to interrupt the Hymenopt while she was working. The temptation to kibitz was enormous.
For lack of anything better to do, Darya made stereo sets of digital images of the other five walls of the chamber, then wandered down toward the place where the hexagonal pyramid terminated. There was no sign of wear inside this artifact, none of the pitting and crumbling and scarring that told of a three-million-year history. Score another one for Quintus Bloom. Labyrinth must be new, the only known new artifact in the whole spiral arm.
At the very end, the shape of the room changed to a narrow wedge. Darya placed her gloved hand in as far as it would go. She tried to estimate the angle, and decided it was about ten degrees. That was consistent with the notion of thirty-seven interiors terminating in the sharp point of Labyrinth. If this formed, as Bloom had suggested, the very end of the artifact, then where her hand was resting should be only inches away from the other interiors — and only a few feet away from open space. If J’merlia’s search for a safe way out was unsuccessful, maybe they could smash through the wall to freedom.
Where was J’merlia?
He had been away nearly four hours. Another few minutes and he would be past his deadline.
“With respect.” Kallik’s voice came over Darya’s suit communicator. “The results are now ready for final formatting. How would you like them to be presented?”
“Can you show them as a sequence on my suit display? The surface itself first, then images showing how the plane looks at different depths below the surface. Make one for every millimeter, going gradually deeper. And can you display a couple of images each second?”
“It can be done. Anything else?”
“One more thing. Reverse the polarity, so that white on the wall shows as black on the images.”
Kallik said nothing, but the visor on Darya’s suit darkened to become an output display device. An image formed. Darya was seeing just the top fraction of a millimeter of the wall’s surface, with light and dark reversed. She caught her breath. It was a familiar sight: a blackness deeper than any night, and superimposed on it the white star pattern of the spiral arm.
And then it was suddenly not so familiar. “Freeze it there!”
The display sat unmoving on the visor. It was the spiral arm as seen from above the galactic plane, but not quite as it should have been. The familiar locator stars, the bright blue supergiants used by every species as markers, had been subtly moved in their relative positions.
“Are you sure you didn’t change the look angle? The star positions are wrong.”
“I did not make any change. With respect, may I offer a suggestion?”
“Sure. It looks wrong to you, too, doesn’t it?”
“It does. It is not an accurate portrayal of the spiral arm as it is today. But I suggest that the scene may well be of the past or the future. Then the differences that we are seeing would be no more than the effects of stellar long-term movement. Thus.”
The image held for a moment. There was a flicker, then successive image frames took their place on the display. Tiny changes became visible. The luminous locator stars of the spiral arm began to creep across the screen, all moving at different speeds. It seemed to Darya that the pattern became increasingly familiar, but without a reference set of current stellar positions she would not know when the display showed the arm as it was today.
No wonder the chamber wall had been confusing, filled with sets of lines and smears. It was the image of a myriad of stars, their movements plotted over thousands or millions of years, and all added and portrayed together in one three-dimensional structure.
A bright point of green light suddenly appeared on the display, a new star where none had been before.
“What’s that—”
Darya had the answer before she could complete the question, just as another glint of green appeared close to the first. Then another. The green must be showing stars where some species had reached a critical intelligence level — maybe achieved space flight. And those stars were never the blazing supergiants, which were far too young for intelligent life to have developed on the planets around them. That’s why the green points seemed to spring into existence from nowhere.
They were increasing in number, spreading steadily outward from the original marker. Far off to the right, a point of orange suddenly flared into view.
“A new clade?” Kallik asked softly. “If so, then one would expect…”
And indeed, the first point of orange served as the nucleus for many more bright sparks, spreading out from it. The regions of orange and green spread, finally met, and began to overlap each other. The orange predominated. At the same time a third nucleus, this one showing as a single point of ruby-red, came into existence farther along the arm.
The three colored regions grew, changed shape, and merged. The orange points spread most rapidly, consuming the green and red regions, but Darya was hardly watching. She was feeling a strong emotion — not triumph, but relief. It would have been terrible to go back home and admit that where Quintus Bloom had led, she had not even been able to follow.
She leaned her head on the soft back of the helmet and neck support, and closed her eyes.
“We did it, Kallik!”
The Hymenopt remained silent.
“We figured out the polyglyphs. Didn’t we?”
“Perhaps so.” Kallik did not sound satisfied. “With respect, Professor Lang, would you please look once more at your display.”
Darya’s helmet visor showed the spiral arm, positively ablaze with flecks of light. She frowned at it. All the bright sparks were orange, and the geometry of supergiant star positions looked right. The time shown had to be close to the present day.
“Is there more? Can you see what the future tableau looks like?”
“I can indeed.” Kallik was polite as ever. “I chose to halt the display at this point intentionally. You will note that the stellar array appears close to what we perceive it to be today.”
“Right. Why did you stop it?”
“Because the stellar colonization pattern that we see is totally at odds with what we know to be true, and with what Quintus Bloom reported that he found. This image indicates that almost every star is colonized by a single clade, the species represented by orange on the display.”
Ridiculous, but right. Darya struggled to interpret the pattern in terms of what she knew to be true. The numerically dominant species in the spiral arm were humans and Cecropians. Their colony worlds should appear in roughly equal numbers. But everything showed as gleaming orange.
Orange, orange, orange. Sometimes it seemed that the Builders were obsessed by orange, the color showed up so often in their creations. Was it a clue to the Builders themselves — eyes that saw in a different spectral region from human eyes, organs most sensitive at longer wavelengths?
If that were a clue, it was a singularly useless one. Who even knew if Builders had eyes? Perhaps they were like the Cecropians, seeing by echolocation. The one thing that humans knew for certain about the Builders was that they knew nothing for certain.
“Kallik, can you run the display backwards? I’d like to take a look at how each clade started out.”
“I did so already, for my own information. With respect, I think that the frame most likely to interest us is this one.”
An image popped into existence within Darya’s helmet. It was one she had seen before, presumably representing the arm as it had been some time in the past. Green and orange points of light were plentiful. Far off to one side glowed a single mote of baleful red.
Kallik highlighted it with a cursor on the image. “Here we have the first frame in which the third clade — the human clade, from the position of this point — has appeared. With respect, the green and orange lights do not, I feel sure, correspond to the clade colonization patterns.”
“Then what are they?”
“That, I cannot say.” Kallik did not raise her voice, but Darya heard a rare discomfort in it. “But let us go backward again, to the time when orange showed only at a single location in the spiral arm.” The display changed, to show a scene with one solitary point of orange light. The blinking cursor moved under Kallik’s control to stand beside it on the display.
“Here is the origin of our mystery clade. And here” — the cursor hardly moved — “here is a world that we already know all too well. It is Genizee, the home world of the Zardalu. If this display represented reality, we would conclude that the spiral arm is now completely colonized — by Zardalu alone.”
Chapter Seventeen
Hans Rebka had spent a lot of time studying Paradox. He knew the history of the artifact’s discovery, and all about the effects of its interior on incident radiation (little) and intruding sapient species (disastrous). So far as the spiral arm was concerned, Rebka qualified as a Paradox expert.
Whereas…
He hung in space staring back toward the inaccessible outside, then ahead to the ominous-looking central region, and was filled with a sobering thought: he really knew next to nothing about the structure, nature, or origin of Paradox.
There had certainly been changes — nothing in Paradox’s history spoke of irreversible movement within it, or of an isolated torus at the center. But changes how, when, and why?
Another couple of attempts showed that any attempt to move toward the outer surface was a waste of fuel and energy. He turned off his suit’s thrust. That was when he realized that the situation was worse than he had thought. In principle he should be hovering at a fixed location within Paradox. In practice he was drifting, slowly but steadily, toward the center. He could move tangentially without any problem, but always there was a small radial component carrying him farther inward.
His next action was instinctive, the result of twenty years of hard experience. He did not think about it or try to explain it, although E.C. Tally, had he been present, could have done so in his own terms. When a computing problem of exceptional size and urgency was encountered, all subsidiary computation should be halted. Peripheral activities must go into complete stand-by mode, in favor of work on the single central problem.
Of course, Tally regarded humans as very handicapped by virtue of inefficient design. A major part of human central nervous activity went into simple maintenance work, so that total power-down of peripherals or unwanted memory banks was not feasible.
But given those built-in limitations, Hans Rebka came pretty close to E.C. Tally’s ideal. Rebka did not give a thought to Tally, or his own situation, or to anything that might be happening outside Paradox. He did not waste time with more experiments in tangential movement, or futile back-up attempts, or even in speculation as to the reason for his forward motion. Every scrap of his attention focused on the fat donut-disk twenty kilometers ahead of him. Unless something changed, he would be arriving there in an hour or so. Better be ready.
The outside of the donut was studded with dark markings, possible openings. They indicated that the disk was slowly rotating. At first they seemed no more than tiny pock marks, but as Hans came closer he could see a shape to each of them. They were like scores of little black diamonds, irregularly spaced around the disk, the long diagonal of each parallel to the disk’s main axis. What had appeared from a distance to be a central hole right through the disk, making it into a plump torus, now was of more ambiguous nature. There was certainly a darkness at the center, but the black was touched with cloudiness and a hint of structure that did not match Rebka’s concept of empty space.
He stared until his vision blurred. What could give that impression, of simultaneous presence and absence? Nothing in his experience.
No matter. Unless something changed, he would soon be able to find out by direct experience. His inward progress had not slowed. If anything, he was moving faster. Maybe ten more minutes to the center.
Now his ability to move tangentially was important — because he suddenly had a choice. Not much of one, in normal terms, but he could aim for one of the diamond-shaped openings on the side of the disk, or else head for the black swirl at the center.
Which?
Assume that his inability to move farther from the center continued. Then he could enter one of the diamonds, and if that proved useless he might still be able to go on and see what lay in the darkness at the disk’s center. Explore the black region first, and there would be no later chance to visit the diamonds. Maximize your number of options. Decision made.
The disk was rotating, but very slowly. Rendezvous should present no problem. He could count half a dozen different diamonds along the edge, each looking as good as any other. Rebka picked one at random and used his suit thrustor to match angular velocity with it. Then it was only a matter of watching and waiting, making sure that no anomalous increase in his own radial speed threw him off target.
The opening was bigger than it had seemed from a distance, maybe twenty meters on the diamond’s long axis and fifteen on the short. Rebka aimed right for the middle, wondering in the final seconds if he was about to be dissociated to individual atoms, squeezed to a pinpoint of nuclear density matter, or spun a hundred thousand light-years out of the spiral arm to intergalactic space.
He felt a slight resistance as he entered the opening, as though he was passing through a thin film of sticky material. Then he was inside, tensed and quiveringly ready for whatever life-preserving action might be necessary. A sharp note within his helmet told him to glance at the monitors. He observed that the temperature outside his suit had gone instantly from the bleak frigidity of interstellar space to that of a pleasant spring morning on Sentinel Gate.
What else had changed?
Speculation ahead of time would have been a waste of effort, so before entering the diamond he had not allowed himself the indulgence of wondering what he might find inside. In spite of that, he must have carried somewhere in the back of his head a list of things he definitely did not expect to encounter when he went through the opening. Otherwise, there would have been no reason for his astonishment at what he saw when he emerged into the interior.
He was in a room like a misshapen cube. One dimension was the full width of the disk, with curved ceiling and floor that followed the shap
e of the torus. On either side the plane walls stretched away, to make a chamber at least forty meters across. Every square inch of those walls was occupied by cabinets, nozzles, troughs, gas supply lines, faucets, and hoses. Thousand after thousand of them, in all shapes and sizes.
Rebka moved to the far wall of the chamber, closest to the center of Paradox. It was rock-solid, seamless, and resonated a deep boom under a blow from his fist. No way out through that.
He went to inspect the wall on his right. The first units he came to were apparently a line of gas dispensers. There were no dials, indicators or instructions, but it was hard to mistake the turncocks for anything else. Rebka cautiously cracked one open. He waited for his suit’s sensors to sample what came out, then turned the gas stream off at once. Fluorine! Poisonous, highly reactive, and no knowing how much of it the unit would supply. Maybe enough to fill the whole chamber, assuming the membrane at the entrance was able to hold an atmosphere.
Hans moved along the line, trying each dispenser. Chlorine, helium, nitrogen, neon, hydrogen, methane, carbon dioxide, ammonia. Oxygen. He might starve here or die of thirst, but he was not going to asphyxiate. He could recharge the air supply of his suit, matching it to any preferred proportion of gases. In fact — he eyed the line of units, stretching away in both directions — it would not be surprising if some dispensers offered mixtures of gases. Certainly he saw far more dispensers than were needed to offer the gaseous elements and their simplest compounds.
It was tempting to test that idea. Instead, he turned his attention to smaller units farther along the wall. These provided liquids instead of gases. His suit was able to identify only the simplest as he permitted small samples of each to touch the sensors. Methyl alcohol, acetone, ethyl alcohol, benzene, ether, toluene, carbon tetrachloride.
Water.
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