Phase Space

by Stephen Baxter

  But this office, here in the heart of Manhattan, was none of that.

  Malenfant was glaring at Cornelius. ‘You know, I have the feeling you’ve played me for a patsy through this whole damn thing. You’ve always known more than me, been one step ahead, used me to front your projects without telling me the full logic –’

  Cornelius laughed at him, with a chilling arrogance. He barely sees us as human beings at all, Kate realized. He said, ‘Sore pride, Malenfant? Is that really what’s most important to you? We really are just frightened chimpanzees, bewildered by the lights in the sky –’

  ‘You arrogant asshole.’

  Kate looked around the small, oak-panelled conference room. The three of them sat at a polished table big enough for twelve, with small inlaid softscreens. There was a smell of polished leather and clean carpets: impeccable taste, corporate lushness, anonymity. The only real sign of unusual wealth and power, in fact, was the enviable view – from a sealed, tinted window – of Central Park. She saw people strolling, children playing on the glowing green grass, the floating sparks of police drones everywhere.

  The essentially ordinariness made it all the more scary, of course – today being a day when, she had learned, Mars had gone, vanishing into a blurring wave of alternate possibilities, volcanoes and water-carved canyons and life traces and all.

  Kate said, ‘Malenfant’s essentially right, isn’t he? On some level you anticipated all this.’

  ‘How can you know that?’

  ‘I saw you smile. At JPL.’

  Cornelius nodded. ‘You see? Simple observation, Malenfant. This girl really is brighter than you are.’

  ‘Get to the point, Cornelius.’

  Cornelius sighed, a touch theatrically. ‘You know, the facts are there, staring everybody in the face. The logic is there. It’s just that most people are unwilling to think it through.

  ‘Take seriously for one minute the possibility that we are living in a planetarium, some kind of virtual-reality projection. What must it cost our invisible controllers to run? We are an inquisitive species, Malenfant. At any moment we are liable to test anything and everything to destruction. To maintain their illusion, the controllers would surely require that their simulation of every object should be perfect – that is, undistinguishable from the real thing by any conceivable physical test.’

  ‘No copy is perfect,’ Malenfant said briskly. ‘Quantum physics. Uncertainty. All that stuff.’

  ‘In fact your intuition is wrong,’ Cornelius said. ‘Quantum considerations actually show that a perfect simulation is possible – but it is energy-hungry.

  ‘You see, there is a limit to the amount of information which may be contained within a given volume. This limit is called the Bekenstein Bound.’ Equations scrolled across the table surface before Kate; she let them glide past her eyes. ‘The Bound is essentially a manifestation of the Heisenberg Uncertainty Principle, a reflection of the fundamental “graininess” of our reality. Because of the existence of the Bound, every physical object is a finite state machine – that is, it only requires a finite number of bits to replicate its every possible condition. Therefore a perfect simulation of any physical object can be made – perfect, meaning undistinguishable from the real thing by any conceivable physical test.’

  Kate said uneasily, ‘Anything can be replicated?’

  Cornelius smiled. ‘Including you, Kate. But perfect simulations are expensive. The bigger they are, the more energy they burn. And that is the chink in the controllers’ armour.’

  ‘It is?’

  ‘As human civilization has progressed, successively larger portions of reality have come within our reach. And the extent of the universe which must be simulated to high quality likewise increases: the walls around reality must be drawn successively back. Before 1969, for example, a crude mock-up of the Moon satisfying only a remote visual inspection might have sufficed; but since 1969, we can be sure that the painted Moon had to be replaced with a rocky equivalent. You see?’ He winked at Kate. ‘A conspiracy theorist might point to the very different quality of the Moon’s far side to its Earth-visible near side – mocked up in a hurry, perhaps?’

  ‘Oh, bullshit, Cornelius,’ Malenfant said tiredly.

  Kate said, ‘You actually have numbers for all this?’

  Malenfant grunted. ‘Numbers, yeah. The mathematics of paranoia.’

  Cornelius, unperturbed, tapped at his desktop surface, and a succession of images, maps with overlays and graphs, flickered over its surface. ‘We can estimate the resources required to run a perfect planetarium of any given size. It’s just a question of quantum mechanics and thermodynamics.’ He flicked a smile. ‘Graduate physics. Two equations.

  ‘Look here. For much of its pre-agricultural history humanity consisted of small roaming bands with little knowledge, save for tentative trading links, beyond a disc on the Earth’s surface with radius of a few kilometres. To generate planetariums on such a scale would require no more than a few per cent of the energy available to a planetary-scale civilization: we could probably do it.

  ‘But by the time you have to fool a cohesive culture covering a hundred kilometres – that’s a lot smaller than the Roman Empire, say – the capabilities of that planetary-level civilization would be exceeded.

  ‘The bigger the planetarium, the harder it gets. We can characterize our modern globe-spanning civilization by the radius of Earth and a depth corresponding to our deepest mines. To generate a planetarium on such a scale would exceed even the capability of a civilization able to master the energy output of a single star.

  ‘A future human culture capable of direct exploration of the centre of the Earth, and able to reach comets twice as far away as Pluto, would exhaust the resources of a galaxy.

  ‘And if we reach the stars, we would test the resources of any conceivable planetarium …’

  Kate was bewildered by the escalation of number and concept. ‘We would?’

  ‘Imagine a human colonization disc of radius a hundred light years, embedded in the greater disc of the Galaxy. To simulate every scrap of mass in there would exceed in energy requirements the resources of the entire visible universe. So after that point, any simulation must be less than perfect – and its existence prone to our detection. The lies must end, sooner or later. But, of course, we might not have to wait that long.’

  ‘Wait for what?’

  ‘To crash the computer.’ He grinned, cold; on some level, she saw, this was all a game to him, the whole universe as an intellectual puzzle. ‘Perhaps we can overstretch their capacity to assemble increasing resources. Rushing the fence might be the way: we could send human explorers out to far distances in all directions as rapidly as possible, pushing back the walls around an expanding shell of space. But advanced robot spacecraft, equipped with powerful sensors, might achieve the same result …’

  ‘Ah,’ said Kate. ‘Or maybe even active but ground-based measures. Like laser echoing. And that’s why you pushed Project Michelangelo.’

  Malenfant leaned forward. ‘Cornelius – what have you done?’

  Cornelius bowed his head. ‘By the logic of Fermi, I was led to the conclusion that our universe is, in whole or in part, a thing of painted walls and duck blinds. I wanted to challenge those who hide from us. The laser pulse to Centauri – a sudden scale expansion of direct contact by a factor of thousands – was the most dramatic way I could think of to drive the controllers’ processing costs through the roof. And it must have caught them by surprise – our technology is barely able enough to handle such a feat – those critics were right, Malenfant, when they criticized the project for being premature. But they did not see my true purpose.’

  Kate said slowly, ‘I can’t believe your arrogance. What gave you the right –’

  ‘To bring the sky crashing down?’ His nostrils flared. ‘What gave them the right to put us in a playpen in the first place? If we are being contained and deceived, we are in a relationship of unequals. If our cont
rollers exist, let them show themselves and justify their actions. That was my purpose – to force them out into the open. And imagine what we might see! The fire-folk sitting in the air! / The bright boroughs, the circle-citadels there! … Do you know Gerard Manley Hopkins?’

  Malenfant shook his head. ‘You were right, Kate. The guy is crazy.’

  Cornelius studied them both. ‘To practical matters. When the anomalies are visible to all, disorder among the foolish herds will follow. Soon flights will be grounded, the freeways jammed. If you wish to leave –’

  Malenfant touched Kate’s hand. ‘Where is home for you?’

  She shrugged. ‘I have an apartment in LA. I don’t even know where my parents are. Either of them.’

  ‘It’s not a time to be alone. Go be with your mom.’

  ‘No.’ She was shuddering. Her involvement in all this had long passed that of a journalist attached to a story; now she was just another human being, staring bewildered at the approaching hurricane – but here she was at the eye of the storm, and something about Malenfant’s strength reassured her. ‘Let me stay. Please.’

  He nodded brusquely, avoiding her eyes. ‘Cornelius, if you have nowhere else to go –’

  Kate said, ‘How long?’

  Cornelius shrugged. ‘The math is chancy. Twenty-four hours at best.’

  It feels like half the population of the human race has downloaded.

  ‘Into what?’

  Into anything they can find. Some folk are trying to create self-sentient copies of themselves, existing entirely within the data nets. The ultimate bunker, right?

  ‘I thought that is illegal.’

  So what do you think the data cops are going to do about it today?

  ‘Anyhow it’s futile. A copy wouldn’t be you.’

  You tell me. There are philosophical principles about the identity of indiscernibles: if a copy really is identical right down to the quantum level, then it has to be the original … Something like that. Anyhow I doubt it’s going to be achieved in the time left.

  ‘I’m surprised we aren’t running out of capacity.’

  There have been a few crashes. But as ends of the world go, this is an odd one, Kate. Even now it’s still just a bunch of funny lights in the sky. The sun is shining, the water supply is flowing, the power is on.

  And, you know, in a way it’s an exciting time; inside here, anyhow. There’s a kind of huge technological explosion, more innovation in the last few hours than in a decade.

  ‘I think I should go now. I have people I’m meant to be with, physically I mean –’

  Damn right you should go.

  ‘What?’

  More room for me, sister.

  She felt affronted. ‘What use is huddling here? This isn’t a nuclear war. It’s not even an asteroid strike. Rodent, there might be nothing left – no processors to maintain your electronic nirvana.’

  So I’ll take my chance. And anyhow there’s the possibility of accelerated perception: you know, four subjective hours in the tank for one spent outside. There are rumours the Chinese have got a way to drive that ratio up to infinity – making this final day last forever – hackers are swarming like locusts over the Chinese sites. And that’s where I’m headed. Get out of here. There won’t be room for everybody.

  ‘Rodent –’

  Wake up, wake up.

  Kate, with Malenfant and Cornelius, stood on Mike’s porch. Inside the house, the baby was crying.

  And in the murky Houston sky, new Moons and Earths burst like silent fireworks, glowing blue or red or yellow, each lit by the light of its own out-of-view sun.

  There were small Earths, wizened worlds that reminded her of Mars, with huge continents of glowering red rock. But some of them were huge, monster planets drowned in oceans that stretched from pole to pole. The Moons were different too. The smallest were just bare grey rock like Luna, but the largest were almost Earth-like, showing thick air and ice and the glint of ocean. There were even Earths with pairs of Moons, Kate saw, or triplets. One ice-bound Earth was surrounded by a glowing ring system, like Saturn’s.

  Kate found it hard not to flinch; it was like being under a hail of gaudy cannonballs, as the alternate planets flickered in and out of existence in eerie, precise silence.

  It was just seven days since the failed echo from Centauri.

  ‘I wonder what’s become of our astronauts,’ Malenfant growled. ‘Poor bastards.’

  ‘A great primordial collision shaped Earth and Moon,’ Cornelius murmured. ‘Everything about Earth and Moon – their axial tilt, composition, atmosphere, length of day, even Earth’s orbit around the sun – was determined by the impact. But it might have turned out differently. Small, chance changes in the geometry of the collision would have made a large difference in the outcome. Lots of possible realities, budding off from that key, apocalyptic moment …’

  Malenfant said, ‘So what are we looking at? Computer simulations from the great planetarium?’

  ‘Phase space.’ Cornelius seemed coldly excited. ‘The phase space of a system is the set of all conceivable states of that system. We’re glimpsing phase space.’

  Malenfant said, ‘Is this what we were being protected from? This – disorderliness?’

  ‘Maybe. As we evolved to awareness we found ourselves in a clean, logical universe, a puzzle box that might have been designed to help us figure out the underlying laws of nature, and so develop our intelligence. But it was always a mystery why the universe should be comprehensible to our small brains at all. Maybe we now know why: the whole thing was a fake, a training ground for our infant species. Now we have crashed the simulator.’

  ‘But,’ said Kate, ‘we aren’t yet ready for the real thing.’

  ‘Evidently not. Perhaps we should have trusted the controllers. They must be technologically superior. Perhaps we should assume they are morally superior also.’

  ‘A little late to think of that now,’ Malenfant said bitterly.

  No traffic moved on the street. Everybody had gone home, or anyhow found a place to hunker down, until –

  Well, until what, Kate? As she had followed this gruesome step-by-step process from the beginning, she had studiously avoided thinking about its eventual outcome: when the wave of unreality, or whatever the hell it was, came washing at last over Earth, over her. It was unimaginable – even more so than her own death. At least after her death she wouldn’t know about it; would even that be true after this?

  Now there were firebursts in the sky. Human fire.

  ‘Nukes,’ Malenfant said softly. ‘We’re fighting back, by God. Well, what else is there to do but try? God bless America.’

  Saranne snapped, ‘Come back in and close the damn door.’

  The three of them filed meekly inside. Saranne, clutching her baby, stalked around the house’s big living room, pulling curtains, as if that would shut it all out. But Kate didn’t blame her; it was an understandable human impulse.

  Malenfant threw a light switch. It didn’t work.

  Mike came in from the kitchen. ‘No water, no power.’ He shrugged. ‘I guess that’s it.’ He moved around the room, setting candles on tables and the fire hearth; their glow was oddly comforting. The living room was littered with pails of water, cans of food. It was as if they were laying up for a snowstorm, Kate thought.

  Malenfant said, ‘What about the softscreens?’

  Mike said, ‘Last time I looked, all there was to see was a loop of the President’s last message. The one about playing with your children, not letting them be afraid. Try again if you want.’

  Nobody had the heart.

  The light that flickered around the edges of the curtains seemed to be growing more gaudy.

  ‘Kind of quiet,’ Mike said. ‘Without the traffic noise –’

  The ground shuddered, like a quake, like a carpet being yanked from under them.

  Saranne clutched her baby, laden with its useless immortality, and turned on Cornelius. ‘All this from
your damn-fool stunt. Why couldn’t you leave well enough alone? We were fine as we were, without all this. You had no right – no right …’

  ‘Hush.’ Malenfant moved quickly to her, and put an arm around her shuddering shoulders. ‘It’s okay, honey.’ He drew her to the centre of the room and sat with her and the infant on the carpet. He beckoned to the others. ‘We should hold onto each other.’

  Mike seized on this eagerly. ‘Yes. Maybe what you touch stays real – you think?’

  They sat in a loose ring. Kate found herself between Malenfant and Saranne. Saranne’s hand was moist, Malenfant’s as dry as a bone: that astronaut training, she supposed.

  ‘Seven days,’ Malenfant said. ‘Seven days to unmake the world. Kind of Biblical.’

  ‘A pleasing symmetry,’ Cornelius said. His voice cracked.

  The candles blew out, all at once. The light beyond the curtains was growing brighter, shifting quickly, slithering like oil.

  The baby stopped crying.

  ‘Hold my hand, Malenfant,’ Kate whispered.

  ‘It’s okay –’

  ‘Just hold my hand.’

  She felt a deep, sharp stab of regret. Not just for herself, but for mankind. She couldn’t believe this was the end of humanity: you wouldn’t exterminate the occupants of a zoo as punishment for poking a hole in the fence.

  But this was surely the end of the world she had known. The play was over, the actors removing their make-up, the stage set collapsing – and human history was ending.

  I guess we’ll never know how we would have turned out, she thought.

  Now the peculiar daylight shone through the fabric of the walls, as if they were wearing thin.

  ‘Oh, shit,’ Mike said. He reached for Saranne.

  Cornelius folded over on himself, rocking, thumb in mouth.

  Malenfant said, ‘What’s wrong? Isn’t this what you wanted? …’

  The wall dissolved. Pale, disorderly light spilled over them.