Contact by Carl Sagan
Xi’s face showed fierce determination, she thought; Lunacharsky’s a deliberate calm; Sukhavati’s eyes were open wide; Eda revealed only an attitude of quiet attentiveness. Devi caught her glance and smiled.
She wished she had had a child. It was her last thought before the walls flickered and became transparent and, it seemed, the Earth opened up and swallowed her.
PART III
THE
GALAXY
So I walk on uplands unbounded,
and know that there is hope
for that which Thou didst mold out of dust
to have consort with things eternal.
—The Dead Sea Scrolls
CHAPTER 19
Naked Singularity
…mount to paradise
By the stairway of surprise.
—RALPH WALDO EMERSON
“Merlin,” Poems (1847)
It is not impossible that to some infinitely superior being the whole universe may be as one plain, the distance between planet and planet being only as the pores in a grain of sand, and the spaces between system and system no greater than the intervals between one grain and the grain adjacent.
—SAMUEL TAYLOR COLERIDGE
Omniania
THEY WERE falling. The pentagonal panels of the dodecahedron had become transparent. So had the roof and the floor. Above and below she could make out the organosilicate lacework and the implanted erbium dowels, which seemed to be stirring. All three benzels had disappeared. The dodecahedron plunged, racing down a long dark tunnel just broad enough to permit its passage. The acceleration seemed somewhere around one g. As a result, Ellie, facing forward, was pressed backward in her chair, while Devi, opposite her, was bending slightly at the waist. Perhaps they should have added seat belts.
It was hard not to entertain the thought that they had plunged into the mantle of the Earth, bound for its core of molten iron. Or maybe they were on their way straight to… She tried to imagine this improbable conveyance as a ferryboat upon the River Styx.
There was a texture to the tunnel walls, from which she could sense their speed. The patterns were irregular soft-edged mottlings, nothing with a well-defined form. The walls were not memorable for their appearance, only for their function. Even a few hundred kilometers beneath the Earth’s surface the rocks would be glowing with red heat. There was no hint of that. No minor demons were managing the traffic, and no cupboards with jars of marmalade were in evidence.
Every now and then a forward vertex of the dodecahedron would brush the wall, and flakes of an unknown material would be scraped off. The dodec itself seemed unaffected. Soon, quite a cloud of fine particles was following them. Every time the dodecahedron touched the wall, she could sense an undulation, as if something soft had retreated to lessen the impact. The faint yellow lighting was diffuse, uniform. Occasionally the tunnel would swerve gently, and the dodec would obligingly follow the curvature. Nothing, so far as she could see, was headed toward them. At these speeds, even a collision with a sparrow would produce a devastating explosion. Or what if this was an endless fall into a bottomless well? She could feel a continuous physical anxiety in the pit of her stomach. Even so, she entertained no second thoughts.
Black hole, she thought. Black hole. I’m falling through the event horizon of a black hole toward the dread singularity. Or maybe this isn’t a black hole and I’m headed toward a naked singularity. That’s what the physicists called it, a naked singularity. Near a singularity, causality could be violated, effects could precede causes, time could flow backward, and you were unlikely to survive, much less remember the experience. For a rotating black hole, she dredged up from her studies years before, there was not a point but a ring singularity or something still more complex to be avoided. Black holes were nasty. The gravitational tidal forces were so great that you would be stretched into a long thin thread if you were so careless as to fall in. You would also be crushed laterally. Happily, there was no sign of any of this. Through the gray transparent surfaces that were now the ceiling and floor, she could see a great flurry of activity. The organosilicate matrix was collapsing on itself in some places and unfolding in others; the embedded erbium dowels were spinning and tumbling. Everything inside the dodec—including herself and her companions—looked quite ordinary. Well, maybe a bit excited. But they were not yet long thin threads.
These were idle ruminations, she knew. The physics of black holes was not her field. Anyway, she could not understand how this could have anything to do with black holes, which were either primordial—made during the origin of the universe—or produced in a later epoch by the collapse of a star more massive than the Sun. Then, the gravity would be so strong that—except for quantum effects—even light could not escape, although the gravitational field certainly would remain. Hence “black,” hence “hole.” But they hadn’t collapsed a star, and she couldn’t see any way in which they had captured a primordial black hole. Anyway, no one knew where the nearest primordial black hole might be hiding. They had only built the Machine and spun up the benzels.
She glanced over to Eda, who was figuring something on a small computer. By bone conduction, she could feel as well as hear a low-pitched roaring every time the dodec scraped the wall, and she raised her voice to be heard.
“Do you understand what’s going on?”
“Not at all,” he shouted back. “I can almost prove this can’t be happening. Do you know the Boyer-Lindquist coordinates?”
“No, sorry.”
“I’ll explain it to you later.”
She was glad he thought there would be a “later.”
Ellie felt the deceleration before she could see it, as if they had been on the downslope of a roller coaster, had leveled out, and now were slowly climbing. Just before the deceleration set in, the tunnel had made a complex sequence of bobs and weaves. There was no perceptible change either in the color or in the brightness of the surrounding light. She picked up her camera, switched to the long-focal-length lens, and looked as far ahead of her as she could. She could see only to the next jag in the tortuous path. Magnified, the texture of the wall seemed intricate, irregular, and, just for a moment, faintly self-luminous.
The dodecahedron had slowed to a comparative crawl. No end to the tunnel was in sight. She wondered if they would make it to wherever they were going. Perhaps the designers had miscalculated. Maybe the Machine had been built imperfectly, just a little bit off; perhaps what had seemed on Hokkaido an acceptable technological imperfection would doom their mission to failure here in…in wherever this was. Or, glancing at the cloud of fine particles following and occasionally overtaking them, she thought maybe they had bumped into the walls one time too often and lost more momentum than had been allowed for in the design. The space between the dodec and the walls seemed very narrow now. Perhaps they would find themselves stuck fast in this never-never land and languish until the oxygen ran out. Could the Vegans have gone to all this trouble and forgotten that we need to breathe? Hadn’t they noticed all those shouting Nazis?
Vaygay and Eda were deep in the arcana of gravitational physics—twistors, renormalization of ghost propagators, time-like Killing vectors, non-Abelian gauge invariance, geodesic refocusing, eleven-dimensional Kaluza-Klein treatments of supergravity, and, of course, Eda’s own and quite different superunification. You could tell at a glance that an explanation was not readily within their grasp. She guessed that in another few hours the two physicists would make some progress on the problem. Superunification embraced virtually all scales and aspects of physics known on Earth. It was hard to believe that this…tunnel was not itself some hitherto unrealized solution of the Eda Field Equations.
Vaygay asked, “Did anyone see a naked singularity?”
“I don’t know what one looks like,” Devi replied.
“I beg your pardon. It probably wouldn’t be naked. Did you sense any causality inversion, anything bizarre—really crazy—maybe about how you were thinking, anything like scrambled e
Devi looked at Vaygay through narrowed lids.
“It’s okay,” Ellie quickly interjected. Vaygay’s a little excited, she added to herself. “These are genuine questions about black holes. They only sound crazy.”
“No,” replied Devi slowly, “except for the question itself.” But then she brightened. “In fact it was a marvelous ride.”
They all agreed. Vaygay was elated.
“This is a very strong version of cosmic censorship,” he was saying. “Singularities are invisible even inside black holes.”
“Vaygay is only joking,” Eda added. “Once you’re inside the event horizon, there is no way to escape the black hole singularity.”
Despite Ellie’s reassurance, Devi was glancing dubiously at both Vaygay and Eda. Physicists had to invent words and phrases for concepts far removed from everyday experience. It was their fashion to avoid pure neologisms and instead to evoke, even if feebly, some analogous commonplace. The alternative was to name discoveries and equations after one another. This they did also. But if you didn’t know it was physics they were talking, you might very well worry about them.
She stood up to cross over to Devi, but at the same moment Xi roused them with a shout. The walls of the tunnel were undulating, closing in on the dodecahedron, squeezing it forward. A nice rhythm was being established. Every time the dodec would slow almost to a halt, it was given another squeeze by the walls. She felt a slight motion sickness rising in her. In some places it was tough going, the walls working hard, waves of contraction and expansion rippling down the tunnel. Elsewhere, especially on the straightaways, they would fairly skip along.
A great distance away, Ellie made out a dim point of light, slowly growing in intensity. A blue-white radiance began flooding the inside of the dodecahedron. She could see it glint off the black erbium cylinders, now almost stationary. Although the journey seemed to have taken only ten or fifteen minutes, the contrast between the subdued, restrained ambient light for most of the trip and the swelling brilliance ahead was striking. They were rushing toward it, shooting up the tunnel, and then erupting into what seemed to be ordinary space. Before them was a huge blue-white sun, disconcertingly close. Ellie knew in an instant it was Vega.
• • •
She was reluctant to look at it directly through the long-focal-length lens; this was foolhardy even for the Sun, a cooler and dimmer star. But she produced a piece of white paper, moved it so it was in the focal plane of the long lens and projected a bright image of the star. She could see two great sunspot groups and a hint, she thought, a shadow, of some of the material in the ring plane. Putting down the camera, she held her hand at arm’s length, palm outward, to just cover the disk of Vega, and was rewarded by seeing a brilliant extended corona around the star; it had been invisible before, washed out in Vega’s glare.
Palm still outstretched, she examined the ring of debris that surrounded the star. The nature of the Vega system had been the subject of worldwide debate ever since receipt of the prime number Message. Acting on behalf of the astronomical community of the planet Earth, she hoped she was not making any serious mistakes. She videotaped at a variety of f/stops and frame speeds. They had emerged almost in the ring plane, in a debris-free circumstellar gap. The ring was extremely thin compared with its vast lateral dimensions. She could make out faint color gradations within the rings, but none of the individual ring particles. If they were at all like the rings of Saturn, a particle a few meters across would be a giant. Perhaps the Vegan rings were composed entirely of specks of dust, clods of rock, shards of ice.
She turned around to look back at where they had emerged and saw a field of black—a circular blackness, blacker than velvet, blacker than the night sky. It eclipsed that leeward portion of the Vega ring system which was otherwise—where not obscured by this somber apparition—clearly visible. As she peered through the lens more closely, she thought she could see faint erratic flashes of light from its very center. Hawking radiation? No, its wavelength would be much too long. Or light from the planet Earth still rushing down the tube? On the other side of that blackness was Hokkaido.
Planets. Where were the planets? She scanned the ring plane with the long-focal-length lens, searching for embedded planets—or at least for the home of the beings who had broadcast the Message. In each break in the rings she looked for a shepherding world whose gravitational influence had cleared the lanes of dust. But she could find nothing.
“You can’t find any planets?” Xi asked.
“Nothing. There’s a few big comets in close. I can see the tails. But nothing that looks like a planet. There must be thousands of separate rings. As far as I can tell, they’re all made of debris. The black hole seems to have cleared out a big gap in the rings. That’s where we are right now, slowly orbiting Vega. The system is very young—only a few hundred million years old—and some astronomers thought it was too soon for there to be planets. But then where did the transmission come from?”
“Maybe this isn’t Vega,” Vaygay offered. “Maybe our radio signal comes from Vega, but the tunnel goes to another star system.”
“Maybe, but it’s a funny coincidence that your other star should have roughly the same color temperature as Vega—look, you can see it’s bluish—and the same kind of debris system. It’s true, I can’t check this out from the constellations because of the glare. I’d still give you ten-to-one odds this is Vega.”
“But then where are they?” Devi asked.
Xi, whose eyesight was acute, was staring up—through the organosilicate matrix, out the transparent pentagonal panels, into the sky far above the ring plane. He said nothing, and Ellie followed his gaze. There was something there, all right, gloaming in the sunlight and with a perceptible angular size. She looked through the long lens. It was some vast irregular polyhedron, each of its faces covered with…a kind of circle? Disk? Dish? Bowl?
“Here, Qiaomu, look through here. Tell us what you see.”
“Yes, I see. Your counterparts…radio telescopes. Thousands of them, I suppose, pointing in many directions. It is not a world. It is only a device.”
They took turns using the long lens. She concealed her impatience to look again. The fundamental nature of a radio telescope was more or less specified by the physics of radio waves, but she found herself disappointed that a civilization able to make, or even just use, black holes for some kind of hyperrelativistic transport would still be using radio telescopes of recognizable design, no matter how massive the scale. It seemed backward of the Vegans…unimaginative. She understood the advantage of putting the telescopes in polar orbit around the star, safe except for twice each revolution from collisions with ring plane debris. But radio telescopes pointing all over the sky—thousands of them—suggested some comprehensive sky survey, an Argus in earnest. Innumerable candidate worlds were being watched for television transmission, military radar, and perhaps other varieties of early radio transmission unknown on Earth. Did they find such signals often, she wondered, or was the Earth their first success in a million years of looking? There was no sign of a welcoming committee. Was a delegation from the provinces so unremarkable that no one had been assigned even to note their arrival?
When the lens was returned to her she took great care with focus, f/stop, and exposure time. She wanted a permanent record, to show the National Science Foundation what really serious radio astronomy was like. She wished there were a way to determine the size of the polyhedral world. The telescopes covered it like barnacles on a whaler. A radio telescope in zero g could be essentially any size. After the pictures were developed, she would be able to determine the angular size (maybe a few minutes of arc), but the linear size, the real dimensions, that was impossible to figure out unless you knew how far away the thing was. Nevertheless she sensed it was vast.
“If there are no worlds here,” Xi was saying, “then there are no Vegans. No one lives here. Vega is only a guard-h
“Those radio telescopes”—he glanced upward—“are the watchtowers of the Great Wall. If you are limited by the speed of light, it is difficult to hold a galactic empire together. You order the garrison to put down a rebellion. Ten thousand years later you find out what happened. Not good. Too slow. So you give autonomy to the garrison commanders. Then, no more empire. But those”—and now he gestured at the receding blot covering the sky behind them—“those are imperial roads. Persia had them. Rome had them. China had them. Then you are not restricted to the speed of light. With roads you can hold an empire together.”
But Eda, lost in thought, was shaking his bead. Something about the physics was bothering him.
The black hole, if that was what it really was, could now be seen orbiting Vega in a broad lane entirely clear of debris; both inner and outer rings gave it wide berth. It was hard to believe how black it was.
As she took short video pans of the debris ring before her, she wondered whether it would someday form its own planetary system, the particles colliding, sticking, growing ever larger, gravitational condensations taking place until at last only a few large worlds orbited the star. It was very like the picture astronomers had of the origin of the planets around the Sun four and a half billion years ago. She could now make out inhomogeneities in the rings, places with a discernible bulge where some debris had apparently accreted together.