Timelike Infinity

older than you.'

Harry laughed and took a tentative step forward. 'I’m not going to argue with that. But at least it’s your choice. You shouldn’t drink so early in the day, though.'

The Virtual’s projection was slightly off, so there was a small, shadowless gap between Harry’s smart shoes and the floor; Michael smiled inwardly, relishing the tiny reminder of the unreality of the scene. 'The hell with you. I’m two hundred and seven years old; I do what I please.'

A look of sad affection crossed Harry’s brow. 'You always did, son. I’m joking.'

Michael took an involuntary step back from the Virtual; the adhesive soles of his shoes kept him locked to the floor in the weightless conditions of the lifedome. 'What do you want here?'

'I want to give you a hug.'

'Sure.' Michael splashed whiskey over his fingertips and sprinkled droplets over the Virtual; golden spheres sailed through the image, scattering clouds of cubical pixels. 'If that were true you’d be speaking to me in person, not through a Virtual reconstruct.'

'Son, you’re four light-months from home. What do you want, a dialogue spanning the rest of our lives? Anyway, these modern Virtuals are so damned good.' Harry had that old look of defensiveness in his blue eyes now, a look that took Michael all the way back to a troubled boyhood. Another justification, he thought. Harry had been a distant father, always bound up with his own projects — an irregular, excuse-laden intrusion into Michael’s life.

The final break had come when, thanks to AS, Michael had grown older than his father.

Harry was saying, 'Virtuals like this one have passed all the Turing tests anyone can devise for them. As far as you’re concerned, Michael, this is me — Harry — standing here talking to you. And if you took the time and trouble you could send a Virtual back the other way.'

'What do you want, a refund?'

'Anyway, I had to send a Virtual. There wasn’t time for anything else.'

These words, delivered in an easy, matter-of-fact tone, jarred in Michael’s mind. 'Wasn’t time? What are you talking about?'

Harry fixed him with an amused stare. 'Don’t you know?' he asked heavily. 'Don’t you follow the news?'

'Don’t play games,' said Michael wearily. 'You’ve already invaded my privacy. Just tell me what you want.'

Instead of answering directly Harry gazed down through the clear floor beneath his feet. The core of a comet, a mile wide and bristling with ancient spires of ice, slid through the darkness; spotlight lasers from the Hermit Crab evoked hydrocarbon shades of purple and green. 'Quite a view,' Harry said. 'It’s like a sightless fish, isn’t it? A strange, unseen creature sailing through the Solar System’s darkest oceans.'

In all the years he’d studied the comet, that image had never struck Michael; hearing the words now he saw how right it was. But he replied heavily, 'It’s just a comet. And this is the Oort Cloud. The cometary halo, a third of a light-year from the Sun; where all the comets come to die—'

'Nice place,' Harry said, unperturbed. His eyes raked over the bare dome, and Michael abruptly felt as if he were seeing the place through his father’s eyes. The ship’s lifedome, his home for decades, was a half sphere a hundred yards wide. Couches, control panels, and basic data entry and retrieval ports were clustered around the geometric center of the dome; the rest of the transparent floor area was divided up by shoulder-high partitions into lab areas, a galley, a gym, a sleeping area, and a shower.

Suddenly the layout, Michael’s few pieces of furniture, the low single bed, looked obsessively plain and functional.

Harry walked across the clear floor to the rim of the lifedome; Michael, whiskey warming in his hand, joined him reluctantly. From here the rest of the Crab could be seen. A spine bristling with antennae and sensors crossed a mile of space to a block of Europa ice, so that the complete ship had the look of an elegant parasol, with the lifedome as canopy and the Europa ice as handle. The ice block — hundreds of yards wide when mined from Jupiter’s moon — was pitted and raddled, as if molded by huge fingers. The ship’s GUT drive was buried inside that block, and the ice had provided the ship’s reaction mass during Michael’s journey out here.

Harry ducked his head, searching the stars. 'Can I see Earth?'

Michael shrugged. 'From here the inner Solar System is a muddy patch of light. Like a distant pond. You need instruments to make out Earth.'

'You’ve left yourself a long way from home.'

Harry’s hair had been AS-restored to a thick blond mane; his eyes were clear blue stars, his face square, small-featured — almost pixielike. Michael, staring curiously, was struck afresh at how young his father had had himself remade to look. Michael himself had kept the sixty-year-old body the years had already stranded him in when AS technology had emerged. Now he ran an unconscious hand over his high scalp, the tough, wrinkled skin of his cheeks. Damn it, Harry hadn’t even kept the coloring — the black hair, brown eyes — which he’d passed on to Michael.

Harry glanced at Michael’s drink. 'Quite a host,' he said, without criticism in his voice. 'Why don’t you offer me something? I’m serious. You can buy Virtual hospitality chips now. Bars, kitchens. All the finest stuff for your Virtual guests.'

Michael laughed. 'What’s the point? None of it’s real.'

For a second his father’s eyes narrowed. 'Real? Are you sure you know what I’m feeling, right now?'

'I don’t give a damn one way or the other,' said Michael calmly.

'No,' Harry said. 'I believe you really don’t. Fortunately I came prepared.' He snapped his fingers and a huge globe of brandy crystallized in his open palm; Michael could almost smell its fumes. 'Bit like carrying a hip flask. Well, Michael, I can’t say this is a pleasure. How do you live in this godforsaken place?'

The sudden question made Michael flinch, physically. 'I’ll tell you how, if you like. I process comet material for food and air; there is plenty of carbohydrate material, and nitrogen, locked in the ice; and I—'

'So you’re a high-tech hermit. Like your ship. A Hermit Crab, prowling around the rim of the Solar System, too far from home even to talk to another human being. Right?'

'There are reasons,' Michael said, trying to keep self-justification out of his voice. 'Look, Harry, it’s my job. I’m studying quark nuggets—'

Harry opened his mouth; then his eyes lost their focus for a moment, and it was as if he were scanning some lost, inner landscape. At length he said with a weak smile: 'Apparently I used to know what that meant.'

Michael snorted with disgust. 'Nuggets are like extended nucleons…'

Harry’s smile grew strained. 'Keep going.'

Michael talked quickly, unwilling to give his father any help.

Nucleons, protons and neutrons, were formed from combinations of quarks. Under extremes of pressure — at the heart of a neutron star, or during the Big Bang itself — more extended structures could form. A quark nugget, a monster among nucleons, could mass a ton and be a thousandth of an inch wide…

Most of the nuggets from the initial singularity had decayed. But some survived.

'And this is why you need to live out here?'

'The first the inner Solar System knows of the presence of a nugget is when it hits the top of an atmosphere, and its energy crystallizes into a shower of exotic particles. Yes, you can learn something from that — but it’s like watching shadows on the wall. I want to study the raw stuff. And that’s why I’ve come so far out. Damn it, there are only about a hundred humans farther from the Sun, and most of them are light-years away, in starships like the Cauchy, crawling at near lightspeed to God knows where. Harry, a quark nugget sets up a bow wave in the interstellar medium. Like a sparkle of high-energy particles, scattered ahead of itself. It’s faint, but my detectors can pick it up, and — maybe one time out of ten — I can send out a probe to pick up the nugget itself.'

Harry tugged at the corner of his mouth — a gesture that reminded Michael jarringly of a frail eighty-year-old who had gone forever. 'Sounds terrific,' Harry said. 'So what?'

Michael bit back an angry response. 'It’s called basic research,' he said. 'Something we humans have been doing for a couple of thousand years now—'

'Just tell me,' Harry said mildly.

'Because quark nuggets are bundles of matter pushed to the extreme. Some can be moving so close to lightspeed that thanks to time dilation, they reach my sensors barely a million subjective years after leaving the singularity itself.'

'I guess I’m impressed.' Harry sucked on his brandy, turned and walked easily across the transparent floor, showing no signs of vertigo or distraction. He reached a metal chair, sat on it, and crossed his legs comfortably, ignoring the zero-gravity harness. The illusion was good this time, with barely a thread of space between the Virtual’s thighs and the surface of the chair. 'I always was impressed with what you achieved. You, with Miriam Berg, of course. I’m sure you knew that, even if I didn’t say it all that often.'

'No, you didn’t.'

'Even a century ago you were the authority on exotic matter. Weren’t you? That was why they gave you such responsibility on the Interface project.'

'Thanks for the pat on the head.' Michael looked into the sky-blue emptiness of his father’s eyes. 'Is that what you’ve come to talk about? What did you retain when you had your head cleaned out? Anything?'

Harry shrugged. 'What I needed. Mostly stuff about you, if you want to know. Like a scrap-book…'

He sipped his drink, which glowed in the light of the comet, and regarded his son.

* * *

Wormholes were flaws in space and time that connected points separated by lightyears — or by centuries — with near-instantaneous passages of curved space. They were useful… but difficult to build.

On the scale of the invisibly small — on Planck length scales, in which the mysterious effects of quantum gravity operate — spacetime is foamlike, riddled with tiny wormholes. Michael Poole and his team, a century earlier, had pulled such a wormhole out of the foam and manipulated its mouths, distorting it to the size and shape they wanted.

Big enough to take a spacecraft.

That was the easy part. Now they had to make it stable.

A wormhole without matter in its throat — a 'Schwarzchild' solution to the equations of relativity — is unusable. Lethal tidal forces would bar the wormhole portals, the portals themselves would expand and collapse at lightspeed, and small perturbations caused by any infalling matter would result in instability and collapse.

So Poole’s team had had to thread their wormhole with 'exotic' matter.

Space contracted toward the center of the throat and then had to be made to expand again. A repulsive effect in the throat had come from exoticity, the negative energy density of the exotic matter. The wormhole was still intrinsically unstable, even so; but with feedback loops it could be made self-regulating.

At one time negative energy had been thought impossible. Like negative mass, the concept seemed intuitively impossible. But there had been encouraging examples for Michael and his team. Hawking evaporation of a black hole was a kind of mild exoticity… But the negative energy levels Poole had needed were high, equivalent to the pressure at the heart of a neutron star.

It had been a challenging time.

Despite himself Michael found memories of those days filling his head, more vivid than the washed-out lifedome, the imperfect image of his father. Why was it that old memories were so compelling? Michael and his team — including Miriam, his deputy — had spent more than forty years in a slow orbit around Jupiter; the exotic matter process had depended on the manipulation of the energies of the magnetic flux tube that connected Jupiter to its moon, Io. Life had been hard, dangerous — but never dull. As the years had worn away they had watched again and again as the robot