the giant molecular cloud complex Sagittarius B2, which had for decades been a favorite hunting ground for complex organic molecules by her radio-astronomical colleagues on Earth. Closer to the center, they encountered another giant molecular cloud, and then Sagittarius A West, an intense radio source that Ellie herself had observed at Argus.
And just adjacent, at the very center of the Galaxy, locked in a passionate gravitational embrace, was a pair of immense black holes. The mass of one of them was fivemillion suns. Rivers of gas the size of solar systems were pouring down its maw. Two colossal—she ruminated on the limitations of the languages of Earth—two supermas-ive black holes are orbiting one another at the center of the Galaxy. One had been known, or at least strongly suspected. But two? Shouldn't that have shown up as a Doppler displacement of spectral lines? She imagined a sign under one of them reading ENTRANCE and under the other EXIT. At the moment, the entrance was in use; the exit was merely there.
And that was where this Station, Grand Central Station, was-just safely outside the black holes at the center of the Galaxy. The skies were made brilliant by millions of nearby young stars; but the stars, the gas, and the dust were being eaten up by the entrance black hole. “It goes somewhere, right?” she asked. “Of course.”
“Can yon tell me where?”
“Sure. All this stuff winds up in Cygnus A.” Cygnus A was something she knew about. Except only for a nearby supernova remnant in Cassiopeia, it was the brightest radio source in the sides of Earth. She had calculated that in one second Cygnus A produces more energy than the Sun does in 40,000 years. The radio source was 600 million light-years away, far beyond the Milky Way, out in the realm of the galaxies. As with many extragalactic radio sources, two enormous jets of gas, fleeing apart at almost the speed of tight, were making a complex web of Rankine-Hugoniot shock fronts with the thin intergalactic gas—and producing in the process a radio beacon that shone brightly over most of the universe. All the matter in this enormous structure, 500,000 light-years across, was pouring out of a tiny, almost inconspicuous point in space exactly midway between the jets. “You're making Cygnus A?”
She half-remembered a summer's night in Michigan when she was a girl. She had feared she would fall into the sky. “Oh, it's not just us. This is a… cooperative project ofmany galaxies. That's what we mainly do— engineering. Only a… few of us are involved with emerging civilizations.”
At each pause she had felt a kind of tingling in her head, approximately in the left parietal lobe.
`There are cooperative projects between galaxies?” she asked. “Lots of galaxies, each with a kind of Central Administration? With hundreds of billions of stars in each galaxy. And then those administrations cooperate. To pour millions of suns into Centaurus… sorry, Cygnus A? The… Forgive me. I'm just staggered by the scale. Why would you do all this? Whatever for?”
“You mustn't think of the universe as a wilderness. It hasn't been that for billions of years,” he said.
“Think of it more as… cultivated.” Again a tingling.
“But what for? What's there to cultivate?”
“The basic problem is easily stated. Now don't get scared off by the scale. You're an astronomer, after all. The problem is that the universe is expanding, and there's not enough matter in it to stop the expansion.
After a while, no new galaxies, no new stars, no new planets, no newly arisen lifeforms—just the same old crowd. Everything's getting run-down. It'll be boring. So in Cygnus A we're testing out the technology to make something new. You might call it an experiment in urban renewal. It's not our only trial run. Sometime later we might want to close off a piece of the universe and prevent space from getting more and more empty as the aeons pass. Increasing the local matter density's the way to do it, of course. It's good honest work.” Like running a hardware store in Wisconsin. If Cygnus A was 600 million light-years away, then astronomers on Earth—or anywhere in the Milky Way for that matter—were seeing it as it had been 600 million years ago. But on Earth 600 million years ago, she knew, there had hardly been any life even in the oceans big enough to shake a stick at. They were old. Six hundred million years ago, on a beach like this one… except no crabs, no gulls, no palm trees. She tried to imagine some microscopic plant washed ashore, securing a tremulous toehold just above the water line, while these beings were occupied with experimental galactogenesis and introductory cosmic engineering.
“You've been pouring matter into Cygnus A for the last six hundred million years?”
“Well, what you've detected by radio astronomy was just some of our early feasibility testing. We're much further along now.”
And in due course, in another few hundred million years she imagined, radio astronomers on Earth—if any —will detect substantial progress in the reconstruction of the universe around Cygnus A. She steeled herself for further revelations and vowed she would not let them intimidate her. There was a hierarchy of beings on a scale she had not imagined. But the Earth had a place, a significance in that hierarchy; they would not have gone to all this trouble for nothing.
The blackness rushed back to the zenith and was consumed; Sun and blue sky returned. The scene was the same: surf, sand, palms, Magritte door, microcamera, frond, and her… father.
“Those moving interstellar clouds and rings near the center of the Galaxy—aren't they due to periodic explosions around here? Isn't it dangerous to locate the Station here?”
“Episodic, not periodic. It only happens on a small scale, nothing like the sort of thing we're doing in Cygnus A. And it's manageable. We know when it's coming and we generally just hunker down. If it's really dangerous, we take the Station somewhere else for a while. This is all routine, you understand.”
“Of course. Routine. You built it all? The subways, I mean. You and those other… engineers from other galaxies?”
“Oh no, we haven't built any of it.”
“I've missed something. Help me understand.”
“It seems to be the same everywhere. In our case, we emerged a long time ago on many different worlds in the Milky Way. The first of us developed interstellar space-flight, and eventually chanced on one of the transit stations. Of course, we didn't know what it was. We weren't even sore it was artificial until the first of us were brave enough to slide down.”
“Who's “we'? You mean the ancestors of your… race, your species?”
“No, no. We're many species from many worlds. Eventually we found a large number of subways— various ages, various styles of ornamentation, and all abandoned. Most were still in good working condition.
All we did was make some repairs and improvements.”
“No other artifacts? No dead cities? No records of what happened? No subway builders left?” He shook his head. “No industrialized, abandoned planets?” He repeated the gesture.
“There was a Galaxy-wide civilization that picked up and left without leaving a trace—except for the stations?”
“That's more or less right. And it's the same in other galaxies also. Billions of years ago, they all went somewhere. We haven't the slightest idea where.”
“But where could they go?” He shook his head for the third time, but now very slowly.
“So then you're not…”
“No, we're just caretakers,” he said. “Maybe someday they'll come back.”
“Okay, just one more,” she pleaded, holding her index finger up before her as, probably, had been her practice at age two. “One more question.”
“All right,” he answered tolerantly. “But we only have a few minutes left.”
She glanced at the doorway again, and suppressed a tremor as a small, almost transparent crab sidled by.
“I want to know about your myths, your religions. What fills you with awe? Or are those who make the numinous unable to feel it?”
“You make the numinous also. No, I know what you're asking. Certainly we feel it. You recognize that some of this is hard for me to communicate to you. But I'll give yon an example of what you're asking for. I don't say this is it exactly, but it'll give you a…”
He paused momentarily and again she felt a tingle, this time in her left occipital lobe. She entertained the notion that he was rifling through her neurons. Had he missed something last night? If so, she was glad. It meant they weren't perfect.
“…flavor of our numinons. It concerns pi, the ratio of the circumference of a circle to its diameter. You know
