The Time Traveler's Almanac (191 page)

A Brief Alternate History of the Solar System: Part Three

SLIDE 11.

One hundred billion years will pass.

Earth orbits a mere twenty million kilometers from its necrosun in this epoch, and the fires of the accretion disk are banked. Continents jostle and shudder, rising and falling, as the lights strobe around their edges (and occasionally in low equatorial orbit, whenever the Stasis permits a high-energy civilization to arise).

By the end of the first billion years of the voyage, the night skies are dark and starless. The naked eye can still – barely, if it knows where to look – see the Chaos galaxy formed by the collision of M-31 and the Milky Way; but it is a graveyard, its rocky planets mostly supernova-sterilized iceballs ripped from their parent stars by one close encounter too many. Unicellular life (once common in the Milky Way, at least) has taken a knock; multicellular life (much rarer) has received a mortal body blow. Only the Stasis’s lifeboat remains.

Luna still floats in Terrestrial orbit – it is a useful tool to stir Earth’s liquid core. Prone to a rocky sclerosis, the Earth’s heart is a major problem for the Stasis. They can’t let it harden, lest the subduction cycle and the deep carbon cycle on which the biosphere depends grind to a halt. But there are ways to stir it up again. They can afford to wait half a billion years for the Earth to cool, then reseed the reborn planet with archaea and algae. After the first fraught experiment in reterraforming, the Stasis find it sufficient to reboot the mantle and outer core once every ten billion years or so.

The universe changes around them, slowly but surely.

At the end of a hundred billion years, uranium no longer exists in useful quantities in the Earth’s crust. Even uranium 238 decays eventually, and twenty one half-lives is more than enough to render it an exotic memory, like the bright and early dawn of the universe. Other isotopes will follow suit, leaving only the most stable behind.

(The Stasis have sufficient for their needs, and might even manufacture more – were it necessary – using the necrostar’s ergosphere as a forge. But the Stasis don’t particularly want their clients to possess the raw materials for nuclear weapons. Better by far to leave those tools by the wayside.)

The sky is dark. The epoch of star formation has drawn to a close in the galaxies the Earth has left. No bright new stellar nurseries glitter in the void. All the bright, fast-burning suns have exploded and faded. All the smaller main-sequence stars have bloated into dyspeptic ruddy giants, then exhausted their fuel and collapsed. Nothing bright remains save a scattering of dim red and white dwarf stars.

Smaller bodies – planets, moons, and comets – are slowly abandoning their galaxies, shed from stars as their orbits become chaotic, then ejecting at high speed from the galaxy itself in the wake of near encounters with neighboring stars. Like gas molecules in the upper atmosphere of a planet warmed by a star, the lightest leave first. But the process is inexorable. The average number of planets per star is falling slowly.

(About those gas molecules: the Stasis have, after some deliberation, taken remedial action. Water vapor is split by ultraviolet light in the upper atmosphere, and the Earth can ill afford to lose its hydrogen. A soletta now orbits between Earth and the necrosun, filtering out the short-wavelength radiation, and when they periodically remelt the planet to churn the magma, they are at pains to season their new-made hell with a thousand cometary hydrogen carriers. But eventually more extreme measures will be necessary.)

The sky is quiet and deathly cold. The universe is expanding, and the wavelength of the cosmic microwave background radiation has stretched. The temperature of space itself is now only thousandths of a degree above absolute zero. The ripples in the background are no longer detectable, and the distant quasars have reddened into invisibility. Galactic clusters that were once at the far edge of detection are now beyond the cosmic event horizon, and though Earth has only traveled two hundred million light-years from the Local Group, the gulf behind it is nearly a billion light-years wide. This is no longer a suitable epoch for Science Empires, for the dynamic universe they were called upon to study is slipping out of sight.

SLIDE 12.

A trillion years will pass.

The universe beyond the necrosun’s reach is black. Far behind it, the final stars of the Local Group have burned out. White dwarfs have cooled to the temperature of liquid water; red dwarfs have guttered into chilly darkness. Occasionally stellar remnants collide, then the void is illuminated by flashes of lightning, titanic blasts of radiation as the supernovae and gamma-ray bursters flare.

But the explosions are becoming rare. Now it isn’t just planets that are migrating away from the chilly corpses of the galaxies. Stellar remnants are ejected into the void as the galaxies themselves fall apart with age.

Space is empty and cold, barely above absolute zero. The necrostar’s course has passed through what was once the Bootes Void, but there is no end to the emptiness in sight: there are voids in all directions now. The Stasis and their clients have abandoned the practice of astronomy. They maintain a simple radar watch in the direction of travel, sending out a gigawatt ping every year against the tiny risk of a rogue asteroid, but they haven’t encountered an extrasolar body larger than a grain of sand for billions of years.

As for the necrosun’s planetary attendants …

One day they will burn Jupiter to keep themselves warm. And Saturn, and icy Neptune, water bunker for the oceans of Earth. These days have not yet come, for they are still working through the titans, through Rhea and Oceanus, Crius and Hyperion – the brown dwarfs built with Sol’s stolen mass, and the other dwarfs stolen from the Milky Way during the Long Burn. Each brown dwarf burns for many times the age of the universe at the birth of humanity; black holes are nothing if not efficient. But one day they will be used up, the last titan reduced to a dwarfish cinder; and it will be time to start eating the planets.

Not long thereafter, it will be time for the final Reseeding.

Spin Control

Pierce stood uncertainly before the door in the dome. It glowed blue-green with an inner light, and when he looked around, his shadow stretched into the night behind him.

“Don’t wait outside for too long,” someone said waspishly. “The air isn’t safe.”

The air? Pierce wondered as he entered the doorway. The glassy slabs of an airlock slid aside and closed behind him, thrice in rapid succession. He found himself in a spacious vivarium, illuminated by a myriad of daylight-bright lamps shining from the vertices of the dome wall’s triangular segments. There were plants everywhere, green and damp-smelling cycads and ferns and crawling, climbing vines. Insect life hidden in the undergrowth creaked and rattled loudly.

Then he noticed the Librarian, who stood in the clearing before the doors, as unnaturally still as a plastinated corpse.

“I haven’t been here before,” Pierce admitted as he approached the robed figure. “I’ve used outlying branches, but never the central Library itself.”

“I know.” The Librarian pushed back the hood of his robe to reveal a plump, bald head, jowly behind its neat goatee, and gimlet eyes that seemed to drill straight through him.

Pierce stopped, uncertain. “Do I know you?”

“Almost certainly not. Call me Torque. Or Librarian.” Torque pointed to a path through the vegetation. “Come, walk with me. I’ll show you to your reading room, and you can get started. You might want to bookmark this location in case you need to return.”

Pierce nodded. “Is there anybody else here?”

“Not at present.” Torque sniffed. “You and I are the only living human beings on the planet right now, although there may be more than one of you present. You have the exclusive use of the Library’s resources this decade, within reason.”

“Within reason?”

“Sometimes our supervisors – yours or mine – take an interest. They are not required to notify me of their presence.” There was a fork in the path, around a large outcropping of some sort of rock crystal, like quartz; Torque turned left. “Ah, here we are. This is your reading room, Student-Agent Pierce.”

A white-walled roofless cubicle sat in the middle of a clearing, through which ran a small brook, its banks overgrown with moss and ferns. The walls were only shoulder high, a formality and a signifier of privacy; they surrounded a plain wooden desk and a chair. “This is everything?” Pierce asked, startled.

“Not entirely. Look up.” Torque gestured at the dome above them. “In here we maintain a human-compatible biosphere to reprocess your air and waste. We provide light, and heat, although the latter is less important than it will be in a few million years hereabouts. We’ve turned down the sun to conserve mass, but it’s still radiating brightly in the infrared; the real problems will start when we work through the last bunker reserve in about eighteen million years. The dome should keep the Library accessible to readers for about thirty million years after that, well into Fimbulwinter.”

Fimbulwinter: the winter at the end of the world, after the last fuel for the necrosun’s accretion disk had been consumed, leaving Earth adrift in orbit around a cold black hole, billions of light-years from anything else. Pierce shivered slightly at the thought of it. “What’s the problem with the outside air?”

“We were losing hydrogen too fast, and without hydrogen, there’s no water, and without water, we can’t maintain a biosphere, and without a biosphere the planet rapidly becomes less habitable – no free oxygen, for one thing. So about thirty billion years ago we deuterated the biosphere as a conservation measure. Of course, that necessitated major adjustments to the enzyme systems of all the life-forms from bacteria on up, and you – and I – are not equipped to run on heavy water; the stuff’s toxic to us.” Torque pointed at the stream. “You can drink from that, if you like, or order refreshments by phone. But don’t drink outside the dome. Don’t breathe too much, if you can help it.”

Pierce looked around. “So this is basically just a reading room, like a Branch Library. Where’s the real Library? Where are the archives?”

“You’re standing on them.” Torque’s expression was one of restrained impatience: Weren’t you paying attention in class the day they covered this? “The plateau this reading room is built on – in fact, the entire upper crust – is riddled with storage cells of memory diamond, beneath a thin crust of sedimentary rock laid down to protect it. We switched the continental-drift cycle off for good about five billion years ago, after the last core cooling cycle. That’s when we began accumulating the Library deposits.

“Oh.” Pierce looked around. “Well, I suppose I’d better get started. Do you mind?”

“Not at all.” Torque turned his back on Pierce and walked away. “I’ll be around if you call me,” he sent.

Pierce sat down in front of the empty desk and laid his hands palm down on the blotter. A continent of memory diamond? The mere idea of that much data beggared the imagination. “It’ll be in here somewhere,” he muttered, and smiled.

Unhistory

One of the first things that any agent of the Stasis learns is patience. It’s not as if they are short of time; their long lives extend beyond the easy reach of memory, and should they avoid death through violence or accident or suicide, they can pursue projects that would exceed the life expectancy of ordinary mortals. And that is how they live in the absence of the principal aspect of their employment, the ability to request access to the timegate.

Pierce thought at first that the vice-chancellor’s request would be trivial, a matter of taking a few hours or days to dig down into the stacks and review the historical record. He’d return triumphant, a few minutes upstream of his departure, and present his findings before the council. Xiri would be appropriately adoring, and would doubtless write a series of sonnets about his Library visit (for poetics were in fashion as the densest rational format for sociological-academic case studies in Leng): and his adoptive home time would be spared the rigor and pity of a needless doctrinal war. That was his plan.

It came unglued roughly a week after his arrival, at the point when he stopped flailing around in increasing panic and went for a long walk around the paths of the biome, brooding darkly, trying to quantify the task.

Memory diamond is an astonishingly dense and durable data substrate. It’s a lattice of carbon nuclei, like any other diamond save that it is synthetic, and the position of atoms in the lattice represents data. By convention, an atom of carbon 12 represents a zero, and an atom of carbon 13 represents a one; and twelve-point-five grams of memory diamond – one molar weight, a little under half an old-style ounce – stores 6 × 1023 bits of data – or 10 23 bytes, with compression.

The continent the reading room is situated on is fifteen kilometers thick and covers an area of just under forty million square kilometers, comparable to North and South America combined in the epoch of Pierce’s birth. Half of it is memory diamond. There’s well over 1018 tons of the stuff, roughly 10 23 molar weights. One molar weight of memory diamond is sufficient to hold all the data ever created and stored by the human species prior to Pierce’s birth, in what was known at the time as the twenty-first century.

The civilizations over which the Stasis held sway for a trillion years stored a lot more data. And when they collapsed, the Stasis looted their Alexandrian archives, binged on stolen data and vomited it back up at the far end of time.

Pierce’s problem was this: more than 90 percent of the Library consisted of lies.

He’d started out, naturally enough, with two pieces of information: the waypoint in his phone that identified the exact location of the porch of his home in Leng, and the designation of the planetary system in M-33 that had aroused such controversy. It was true, as Xiri had said, that the Hegemony was reveling in the feed from the robot exploration fleet that had swept through the Triangulum galaxy tens of millions of years ago. And he knew – he was certain! – that Xiri, and the Hegemony, and the city of Leng with its Mediterranean airs and absurdly scholastic customs existed. He had held her as his wife and lover for nearly two decades-subjective, dwelt there and followed their ways as an honored noble guest for more than ten of those years: he could smell the hot, damp summer evening breeze in his nostrils, the scent of the climbing blue rose vines on the trellis behind his house —