‘Spell it out,’ Gemo said casually, prowling around the gadgetry. ‘Remember, Reth, the education of these young is woefully inadequate.’
‘This is life,’ Hama said. ‘Native to Callisto.’
‘Life - yes,’ Reth said. ‘The highest forms are about equivalent to Earth’s bacteria. But - native? I believe the life forms here have a common ancestor with Earth life, buried deep in time - and that they are related to the more extravagant biota of Europa’s buried ocean, and probably most of the living things found elsewhere in Sol system. Do you know the notion of panspermia? Life, you see, may have originated in one place, perhaps even outside the system, and then was spread through the worlds by the spraying of meteorite-impact debris. And everywhere it landed, life embarked on a different evolutionary path.’
‘But here,’ Hama said slowly, fumbling to grasp these unfamiliar concepts, ‘it was unable to rise higher than the level of a bacterium?’
‘There is no room,’ said Reth. ‘There is liquid water here: just traces of it, soaked into the pores between the grains of rock and ice, kept from freezing by the radiogenic heat. But energy flows thin, and replication is very slow - spanning thousands of years.’ He shrugged. ‘Nevertheless there is a complete ecosystem. Do you understand? My Callisto bacteria are rather like the cryptoendoliths found in some inhospitable parts of Earth. In Antarctica, for instance, you can crack open a rock and see layers of green life, leaching nutrients from the stone itself, sheltering from the wind and the desolating cold: communities of algae, cyanobacteria, fungi, yeasts—’
‘Not any more,’ Gemo murmured, running a finger over control panels. ‘Reth, the Extirpation was very thorough, an effective extinction event; I doubt if any of your cryptoendoliths can still survive.’
‘Ah,’ said Reth. ‘A shame.’
Hama straightened up, frowning. He had come far from the cramped caverns of the Conurbations; he was confronting life from another world, half a billion kilometres from Earth. He ought to feel wonder. But these pale shadows evoked only a kind of pity. Perhaps this thin, cold, purposeless existence was a suitable object for the obsessive study of a lonely, half-mad immortal.
Reth’s eyes were on him, hard.
Hama said carefully, ‘We know that before the Occupation, Sol system was extensively explored, by Michael Poole and those who followed him. The records of those times are lost - or hidden,’ he said with a glance at the impassive Gemo. ‘But we do know that everywhere humans went, they found life. Life is commonplace. And in most places we reached, life has attained a much higher peak than this. Why not just catalogue these scrapings and abandon the station?’
Reth threw up his arms theatrically. ‘I am wasting my time. Gemo, how can this mayfly mind possibly grasp the subtleties here?’
She said dryly, ‘I think it would serve you to try to explain, brother.’ She was studying a gadget that looked like a handgun mounted on a floating platform. ‘This, for example.’
When Hama approached this device, his weapon-laden drone whirred warningly. ‘What is it?’
Reth stalked forward. ‘It is an experimental mechanism based on laser light, which … It is a device for exploring the energy levels of an extended quantum structure.’ He began to talk rapidly, lacing his language with phrases like ‘spectral lines’ and ‘electrostatic potential wells’, none of which Hama understood.
At length Gemo interpreted for Hama.
‘Imagine a very simple physical system - a hydrogen atom, for instance. I can raise its energy by bombarding it with laser light. But the atom is a quantum system; it can only assume energy levels at a series of specific steps. There are simple mathematical rules to describe the steps. This is called a “potential well”.’
As he endured this lecture, irritation slowly built in Hama; it was clear there was much knowledge to be reclaimed from these patronising, arrogant pharaohs.
‘The potential well of a hydrogen atom is simple,’ said Reth rapidly. ‘The simplest quantum system of all. It follows an inverse-square rule. But I have found the potential wells of much more complex structures.’
‘Ah,’ said Gemo. ‘Structures embedded in the Callisto bacteria.’
‘Yes.’ Reth’s eyes gleamed. He snatched a data slate from a pile at his feet. Lines of numbers chattered over the slate, meaning little to Hama, a series of graphs that sloped sharply before dwindling to flatness: a portrait of the mysterious ‘potential wells’, perhaps.
Gemo seemed to understand immediately. ‘Let me.’ She took the slate, tapped its surface and quickly reconfigured the display. ‘Now, look, Hama: the energies of the photons that are absorbed by the well are proportional to this series of numbers.’
1. 2. 3. 5. 7. 11. 13 …
‘Prime numbers,’ Hama said.
‘Exactly,’ snapped Reth. ‘Do you see?’
Gemo put down the slate and walked to the ice wall; she ran her hand over the translucent cover, as if longing to touch the mystery that was embedded there. ‘So inside each of these bacteria,’ she said, ‘there is a quantum potential well that encodes prime numbers.’
‘And much more,’ said Reth. ‘The primes were just the key, the first hint of a continent of structure I have barely begun to explore.’ He paced back and forth, restless, animated. ‘Life is never content simply to subsist, to cling on. Life seeks room to spread. That is another commonplace, young man. But here, on Callisto, there was no room: not in the physical world; the energy and nutrients were simply too sparse for that. And so—’
‘Yes?’
‘And so they grew sideways,’ he said. ‘And they reached orthogonal realms we never imagined existed.’
Hama stared at the thin purple scrapings and chattering primes, here at the bottom of a pit with these two immortals, and feared he had descended into madness.
… 41. 43. 47. 53. 59 …
In a suit no more substantial than a thin layer of cloth, Nomi Ferrer walked over Callisto’s raw surface, seeking evidence of crimes.
The sun was low on the horizon, evoking highlights from the curved ice plain all around her. From here, Jupiter was forever invisible, but Nomi saw two small discs, inner moons, following their endless dance of gravitational clockwork.
Gemo Cana had told her mayfly companions how the Jovian system had once been. She told them of Io’s mineral mines, nestling in the shadow of the huge volcano Babbar Patera. She told them of Ganymede: larger than Mercury, heavily cratered and geologically rich - the most stable and heavily populated of all the Jovian moons. And Europa’s icy crust had sheltered an ocean hosting life, an ecosystem much more complex and rewarding than anybody had dreamed. ‘They were worlds. Human worlds, in the end. All gone now, shut down by the Qax. But I remember …’
Away from the sun’s glare, lesser stars glittered, surrounding Nomi with immensity. But it was a crowded sky, despite that immensity. Crowded and dangerous. For - she had been warned by the Coalition - the Xeelee craft that had glowered over Earth was now coming here, hotly pursued by a Spline ship retrieved from the hands of jasoft rebels and manned by Green Army officers. What would happen when that miniature armada got here, Nomi couldn’t imagine.
Nomi knew about the Xeelee from barracks-room scuttlebutt. She had tried to educate a sceptical Hama. The Xeelee were a danger mankind encountered long before anybody had heard of the Qax; in the Occupation years they had become legends of a deep-buried, partly extirpated past - and perhaps they were monsters of the human future. The Xeelee were said to be godlike entities so aloof that humans might never understand their goals. Some scraps of Xeelee technology, like starbreaker beams, had fallen into the hands of ‘lesser’ species, like the Qax, and transformed their fortunes. The Xeelee seemed to care little for this - but, on occasion, they intervened. To devastating effect.
Some believed that by such interventions the Xeelee were maintaining their monopoly on power, controlling an empire which, perhaps, held sway across the Galaxy. Others said that, like the vengeful gods of humanity’s childhood, the Xeelee were protecting the ‘junior races’ from themselves.
Either way, Nomi thought, it’s insulting. Claustrophobic. She felt an unexpected stab of resentment. We only just got rid of the Qax, she thought. And now, this.
Gemo Cana had argued that in such a dangerous universe, humanity needed the pharaohs. ‘Everything humans know about the Xeelee today, every bit of intelligence we have, was preserved by the pharaohs. I refuse to plead with you for my life. But I am concerned that you should understand. We pharaohs were not dynastic tyrants. We fought, in our way, to survive the Qax Occupation, and the Extirpation. For we are the wisdom and continuity of the race. Destroy us and you complete the work of the Qax for them, finish the Extirpation. Destroy us and you destroy your own past - which we preserved for you, at great cost to ourselves.’
Perhaps, Nomi thought. But in the end it was the bravery and ingenuity of one human - a mayfly - that had brought down the Qax, not the supine compromising of the jasofts and pharaohs.
She looked up towards the sun, towards invisible Earth. I just want a sky clear of alien ships, she thought. And to achieve that, perhaps we will have to sacrifice much.
Reth Cana began to describe where the Callisto bugs had ‘gone’, seeking room to grow.
‘There is no time,’ he whispered. ‘There is no space. This is the resolution of an ancient debate - do we live in a universe of perpetual change, or a universe where neither time nor motion exist? Now we understand. Now we know we live in a universe of static shapes. Nothing exists but the particles that make up the universe - that make up us. Do you see? And we can measure nothing but the separation between those particles.
‘Imagine a universe consisting of a single elementary particle, an electron perhaps. Then there could be no space. For space is only the separation between particles. Time is only the measurement of changes in that separation. So there could be no time.
‘Imagine now a universe consisting of two particles …’ Gemo nodded. ‘Now you can have separation, and time.’ Reth bent and, with one finger, scattered a line of dark dust grains across the floor. ‘Let each dust grain represent a distance - a configuration of my miniature two-particle cosmos. Each grain is labelled with a single number: the separation between the two particles.’ He stabbed his finger into the line, picking out grains. ‘Here the particles are a metre apart; here a micron; here a light year. There is one special grain, of course: the one that represents zero separation, the particles overlaid. This diagram of dust shows all that is important about the underlying universe - the separation between its two components. And every possible configuration is shown at once, from this god-like perspective.’
He let his finger wander back and forth along the line, tracing out a twisting path in the grains. ‘And here is a history: the two particles close and separate, close and separate. If they were conscious, the particles would think they were embedded in time, that they are coming near and far. But we can see that their universe is no more than dust grains, the lined-up configurations jostling against each other. It feels like time, inside. But from outside, it is just - sequence, a scattering of instants, of reality dust.’
Gemo said, ‘Yes. “It is utterly beyond our power to measure the changes of things by time. Quite the contrary, time is an abstraction at which we arrive by means of the changes of things.” ’ She eyed Hama. ‘An ancient philosopher. Mach, or Mar-que …’
‘If the universe has three particles,’ said Reth, ‘you need three numbers. Three relative distances - the separation of the particles, one from the other - determine the cosmos’s shape. And so the dust grains, mapping possible configurations, would fill up three-dimensional space - though there is still that unique grain, representing the special instant where all the particles are joined. And with four particles—’
‘There would be six separation distances,’ Hama said. ‘And you would need a six-dimensional space to map the possible configurations.’
Reth glared at him, eyes hard. ‘You are beginning to understand. Now. Imagine a space of stupendously many dimensions. ’ He held up a dust grain. ‘Each grain represents one configuration of all the particles in our universe, frozen in time. This is reality dust, a dust of the Nows. And the dust fills configuration space, the realm of instants. Some of the dust grains may represent slices of our own history.’ He snapped his fingers, once, twice, three times. ‘There. There. There. Each moment, each juggling of the particles, a new grain, a new coordinate on the map. There is one unique grain that represents the coalescing of all the universe’s particles into a single point. There are many more grains representing chaos - darkness - a random, structureless shuffling of the atoms.
‘Configuration space contains all the arrangements of matter there could ever be. It is an image of eternity.’ He waved a fingertip through the air. ‘But if I trace out a path from point to point—’
‘You are tracing out a history,’ said Hama. ‘A sequence of configurations, the universe evolving from point to point.’
‘Yes. But we know that time is an illusion. In configuration space, all the moments that comprise our history exist simultaneously. And all the other configurations that are logically possible also exist, whether they lie along the track of that history or not.’