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 eggs reassembling themselves into whites and yolks…?”
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 straight-aways, 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, yon 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-house, a place for the border patrol to warm their hands.”
“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.”