But the small, shining fraction of baryonic matter seemed vital to the dark matter creatures. It was a catalyst for the chains of events which sustained their species.
For a start, dark matter could not form stars. And the birds seemed to need the gravity wells of baryonic stars.
When a clump of baryonic gas collapsed under gravity, electromagnetic radiation carried away much of the heat produced — it was as if the radiation cooled the gas cloud. The residual heat left in the cloud eventually balanced the gravitational attraction, and equilibrium was found: a star formed.
But dark matter could not produce electromagnetic radiation. And without the cooling effect of the radiation, a dark matter cloud, collapsing under gravity, trapped much more of its heat of contraction. As a result, much larger clouds — larger than galaxies — were the equilibrium form for dark matter.
So the early Universe had been populated by immense, cold, bland clouds of dark matter: it had been a cosmos almost without structure.
Then the baryonic matter had gathered, and the stars began to implode — to shine. Lieserl imagined the first stars sparking to life across the cosmos, tiny pinprick gravity wells in the smooth oceans of dark matter.
The photino birds lived off a trickle of proton-photino interactions, which fed them with a slow, steady drip of energy. And to get a sufficient flow of energy the birds needed dense matter — densities which could not have formed without baryonic structures.
And the birds’ dependence on baryonic matter extended further. She knew that the birds needed templates of baryonic material even to reproduce.
So baryonic-matter stars had given the photino birds their very being, and now fed them and enabled them to reproduce.
Lieserl brooded. A fine hypothesis. But why, then, should the birds be so eager to kill off their mother-stars?
Once more the chatter of the humans from the Northern passed through her sensorium, barely registering. They were asking her more questions — requesting more detailed forecasts of the likely future evolution of the suffering Sun.
She sailed moodily around the core, thinking about stars and the photino birds.
And her mind made connections it had failed to complete before in millions of years.
At last, she saw it: the full, bleak picture.
And, suddenly, it seemed urgent — terribly urgent — to answer the humans’ questions about the future.
She hurried to the base of her convection cells.
The shower’s needle-sharp jets of water sprayed over Louise’s skin. She floated there at the center of the shower cubicle, listening to the shrill gurgle of the water as it was pumped out of the booth. She lifted her arms up and let the water play over her belly and chest; it was hot enough, the pressure sufficiently high, to make her battered old skin tingle, as if it were being worked over by a thousand tiny masseurs.
She hated being in zero-gee. She always had, and she hated it still; she even loathed having to have a pump to suck the water out of her shower for her. She’d insisted on having this shower installed, curtained off in one corner of the life-lounge, as her one concession to luxury — no, damn it, she thought, this is no luxury; the shower is my concession to what’s left of my humanity.
A hot shower was one of the few sensual experiences that had remained vivid, as she’d got so absurdly old. High-pressure, steaming water could still cut through the patina of age which deadened her skin.
There was hardly anything else left. Since her sense of smell had finally packed up, eating had become a process of basic refuelling, to be endured rather than enjoyed. And, apart from her Virtuals, nothing much stimulated her mentally; it would take more than a thousand-year life to exhaust the libraries of mankind, but she’d long since wearied of the ancient, frozen thoughts of others, rendered irrelevant by the death of the Sun.
She turned off the spigot. Hot air gushed down around her, drying her rapidly. When the droplets had stopped floating off her skin she pulled back the shower curtain.
The lounge was basic — it contained little more than this shower, a small galley, a sleeping cocoon and her data desk with its processor bank. Lashed up in haste from sections of the Northern’s hull material, the lounge was a squat cylinder five yards across, crouched on the shoulders of the Xeelee craft like a malevolent parasite — utterly spoiling the lines of the delicate nightfighter, Louise had thought regretfully. The walls of the lounge were opaqued to a featureless gray, making the lounge rather dingy and claustrophobic. And the place was a mess. Bits of her clothing drifted around in the air, crumpled and soiled, and she was conscious of a stale smell. She really ought to clean up; she knew she utterly lacked the obsessive neatness needed to survive for long in zero gee.
She reached for a towel drifting in the air close by. She rubbed herself vigorously, relishing the feeling of the rough fabric on her skin. A mere blast of air never left her feeling really dry.
The feel of the warm towel on her skin made her think, distantly, about sex.
She’d always had a sour public persona: people saw her as an engineer obsessed with her job, with building things out there. But there was more to her than that — there were elements which Mark had recognized and treasured during their marriage. Sex had always been important to her: not just for the physical pleasure of it but also for what it symbolized: something deep and old within her, an echo of the ancient sea whose traces humans still carried, even now. The contrast of that oceanic experience with her work had made her more complete, she thought.
After she and Mark had reconciled — tentatively, grudgingly, in recognition of their joint isolation in the Northern — they had revived their vigorous sex life. And it had been good, remaining vital for a long time. Longer than either of them had a right to expect, she supposed. She wrapped the towel around her back and began to rub at her buttocks. Maybe if Mark had stayed alive -
The lounge walls snapped to transparency; space darkness flooded over her.
Louise cried out and pulled the towel around her body.
From her comms desk came the sound of laughter.
She scrambled in a locker for fresh clothes. The door of the jury-rigged locker jammed and she hauled at it, swearing, aware of the towel slipping around her.
“By Lethe’s waters, Spinner, what do you think you’re doing?”
Louise could just make out Spinner’s cage, a box of winking lights at the prow of the nightfighter. A shadow moved across the lights — Spinner, probably, twisting in her couch to take a mocking look at her. “I’m sorry. I knew you’d be embarrassed.”
Louise had found a coverall; now she thrust her legs into it. “Then why,” she said angrily, “did you invade my privacy by doing it?”
“What difference does it make? Louise, there’s no one to see; we’re a billion miles from the nearest living soul. And you’re a thousand years old. You really ought to rid yourself of these taboos.”
“But they’re my taboos,” Louise hissed. “I happen to like them, and they make a difference to me. If you ever get to my age, Spinner-of-Rope, maybe you’ll learn a little tolerance.”
“Well, maybe. Anyway, I didn’t de-opaque your walls just to catch you with your pants off.” She sounded mischievous.
Suspiciously, Louise asked, “Why, then?”
“Because — ” Spinner hesitated.