And, down through the splayed-opened hearts of ancient craters, the quagma pods were descending towards the core.

With the Ambassador, I fell away from the Galaxy, descending beneath the moon.

The sky was empty of stars. The Galaxy was a mottled, glowing ceiling above us, and beneath my feet there was only the distant, etiolated smudge of remote galaxies.

I looked at it all with new eyes. Those shining stars were already infected by the photino birds. Even the most remote galaxy I saw would be affected by the final conflict, between the birds and the doomed Xeelee.

Behind the bright light of the Universe, I had glimpsed the skulllike dismalness of the end of time.

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.