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The Ghosts and their ships had gathered into a rough sphere, a couple of thousand miles from the moon’s surface; the moon hovered above me, a fat, battered orange, made three-dimensional by the subtle shading of Galaxy-core light.
The Sink Ambassador said, “The climax is approaching.” I sensed excitement in the complex patterns which shivered across its surface.
“Tell me how you can make a star of dark matter.”
“Jack Raoul, there are ways to generate compact, self-gravitating solitonlike equilibrium states of bosonic fields. Here we are seeking an oscillating solution, known as an oscillation, which—”
“Lethe,” I said. “I wish Eve was here.”
“Your wife.”
“The real Eve. She was the only one who could make sense of all this stuff for me.”
The Ghost said nothing.
“Keep talking,” I said.
The Ambassador, tried again, in language only slightly less technical, and my internal stores began to feed back trickles of interpretation to me, integrating what the Ghost was saying with the best human models.
Gradually, I began to figure out what the Ghosts were trying to do.
Dark matter can’t form stars, because it can’t cool down fast enough.
When a clump of baryonic gas — normal matter — collapses under gravity, electromagnetic radiation carries away much of the heat produced. It is as if the radiation cools the gas cloud. The residual heat left in the cloud eventually balances the gravitational attraction, and equilibrium is found: a star has formed, a compact, stable body, with internal radiation pressure balancing out the tendency to collapse through gravitation.
But dark matter doesn’t produce electromagnetic radiation. And without the cooling effect of radiation, a dark matter cloud, collapsing under gravity, traps much more of its heat of contraction. So large, diffuse clouds are the equilibrium form for dark matter.
“But,” I said drily, “you’ve found a way around that.” The Sink Ambassador spun complacently. “We are going to use another way to cool a clump of dark matter: gravitational cooling.”
I imagined a swarm of photinos, orbiting each other. The swarm could eject its own faster-moving members, sling-shotting them out like miniature spacecraft around shadowy planets. Because kinetic energy was equivalent to heat, the clump left behind would be cooler, more compact.
“The mechanism is similar to what you know as the Lynden-Bell analysis of the Jeans instability,” the Ghost said. “The mechanism whereby a star cluster can settle to a compact, stable equilibrium by collisionless relaxation: ejecting its own faster-moving components to an outer halo—”
“Enough. So you’re going to use gravitational cooling to form a dark matter star, right here.”
“The quagma pods will impact in the core of the moon, in a complex ma
I tuned him out. I fed all this into my Notebooks.
“Why here?”
The Ghost spun, bobbing in space. “There is much dark matter, here in the galactic halo. And few Xeelee.”
“And few humans, right?”
“I would be interested to know of the source of your information on the project, which—”
“It’s going to take some close control,” I said. “The crucial events will last just microseconds: that complex sequence of quagma collisions in the core… Ambassador, you must have one giant AI controller built into that moon.”
It said nothing to that, and a grain of suspicion lodged in my mind. But I had other issues to pursue.
“Tell me why you’re doing this, Sink Ambassador. If you make a soliton star — so what? What will you have achieved?”
It rolled, as if it was turning to face me.
“You know as much as we do, now, about the fundamental truths of the Universe,” it said. “The secret history of the cosmos: the epochal conflict between light and dark matter, whose effects we have only begun to discern.
“To sustain their existence, the creatures of photino matter need stable baryonic star cores. And therefore they are accelerating the evolution of the stars.” It rolled in space. “Even now,” the Ambassador said, “photino creatures are clustered in the hearts of those hundred billion stars, choking them. Even the original star of mankind, called Sol.”
“But they face resistance.”
“Yes. From the baryonic life forms whose habitats they are destroying. But even the Xeelee, immeasurably stronger than my race or yours, will be defeated.”
I knew that was true, from the glimpses Eve had vouchsafed me.
“And so—”
“And so,” the Ambassador said, “we are striving to generate another option. A better way.” It wheeled over the shaped moon. “Raoul, the quagma pods are merging in the moon’s core. It begins…”
I started to understand. “You think that if you can show the photino birds how to build star-sized objects of dark matter — without using the cores of baryonic stars — they will stop destroying the stars.”
“That is the goal. The dream, if you will.”
“And the great Xeelee war can stop, and we’ll all coexist; we’ll live together, photino birds and Xeelee and humans and Ghosts, like one huge family.” I felt like laughing at it. “Lethe, Ambassador. At least you Ghosts can’t be faulted for thinking big.”
“Now,” it said, “you must understand why your opposition to this project must be withdrawn. On the success of this experiment, the future of the cosmos could hinge.”
I looked up at the engineered moon. There was a sense of mistiness about it, as if a great liquid lens had gathered over that pulverized surface; the light of the Galaxy was refracted, shimmering and softened. I stared into the dark matter mist, hunting for structure.
“It is working,” the Ghost said. “The photinos are coalescing. Soon, the equilibrium oscillations will be induced…”
A trickle of data started whispering in my head. Interpolations and feedback from my datastores, Eve’s Notebooks. Shadowy Virtuals glimmered around me: schematics of the moon, the photino star the Ghosts were building, little charts of growth rates, density-time fluctuations.
There was something odd. The projections of the soliton star’s formation — based on human mathematics — didn’t match up with what the Ghost had told me…
But I was still preoccupied with my hardening suspicions. I thought about prophecy.
Humans had built Michael Poole’s wormhole, and benefited from the fragments of data it had delivered: data from the ends of time. Perhaps the Ghosts, and other races, had achieved similar glimpses of the future.
But all such glimpses are fragmentary and incomplete.
Prophecy is possible using scientific laws, where sufficiently simple events are concerned: the eclipse of a sun, or the return of a long-period comet. And prophecy based in the more complex human arena has been used, after a fashion, for most of humanity’s recorded history. My Notebooks told me about actuarial tables, devices for predicting death rates, that even predated human spaceflight. The more computing power is available, the more detailed a prophecy is possible.