But string theory went on to suggest that gravity was really very strong, if only one looked closely enough. At the Planck scale, the smallest possible increment of measurement, string theory predicted that gravity ramped up to equivalence with the other forces. Indeed, at that scale reality looked rather different in other respects as welclass="underline" curled up like dead woodlice were seven additional dimensions — hyperspaces accessible only on the microscopic scale of quantum interactions.
There was an aesthetic problem with this view, however. The other forces — bundled together as a single unified electroweak force — manifested themselves at a certain characteristic energy. But the strong gravity of string theory would only reveal itself at energies ten million billion times greater than for the electroweak forces. Such energies were far beyond the grasp of experimental procedure. This was the hierarchy problem, and it was considered deeply offensive. Brane theory was one attempt to resolve this glaring schism.
Brane theory — as far as Quaiche understood it — proposed that gravity was really as strong as the electroweak force, even on the classical scale. But what happened to gravity was that it leaked away before it had a chance to show its teeth. What was left — the gravity that was experienced in day-to-day life — was only a thin residue of something much stronger. Most of the force of gravity had dissipated sideways, into adjoining branes or dimensions. The particles that made up most of the universe were glued to a particular braneworld, a particular slice of the laminate of branes that the theory referred to as the bulk. That was why the ordinary matter of the universe only ever saw the one braneworld within which it happened to exist: it was not free to drift off into the bulk. But gravitons, the messenger particles of gravity, suffered no such constraint. They were free to drift between branes, sailing through the bulk with impunity. The best analogy Quaiche had been able to come up with was the printed words on the pages of a book, each confined for all eternity to one particular page, knowing nothing of the words printed on the next page, only a fraction of a millimetre away. And then think of book-worms, gnawing at right angles to the text.
But what of the shadows? This was where Quaiche had to fill in the details for himself. What the shadows appeared to be hinting at — the heart of the heresy — was that they were messengers or some form of communication from an adjacent braneworld. That braneworld might have been completely disconnected from our own, so that the only possible means of communication between the two was through the bulk. There was another possibility, however: the two apparently separate braneworlds might have been distant portions of a single brane, one that was folded back on itself like a hairpin. If that were the case — and the shadows had said nothing on the matter either way — then they were messengers not from another reality but merely from a distant corner of the familiar universe, unthinkably remote in both space and time. The light and energy from their region of space could only travel along the brane, unable to slip across the tiny gap between the folded surfaces. But gravity slipped effortlessly across the bulk, carrying a message from brane to brane. The stars, galaxies and clusters of galaxies in the shadow brane cast a gravitational shadow on our local universe, influencing the motions of our stars and galaxies. By the same token, the gravity caused by the matter in the local part of the brane leaked through the bulk, into the realm of the shadows.
But the shadows were clever. They had decided to communicate across the bulk using gravity as their signalling medium.
There were a thousand ways they might have done it. The specifics didn’t matter. They might have manipulated the orbits of a pair of degenerate stars to produce a ripple of gravitational waves, or learned how to make miniature black holes on demand. The only important thing was that it could be done. And — equally importantly — that someone would be able to pick up the signals on this side of the bulk.
Someone like the scuttlers, for instance.
Quaiche laughed to himself. The heresy made a repulsive kind of sense. But then what else would he have expected? Where there was the work of God, would there not also be the work of the Devil, insinuating himself into the schemes of the Creator, trying to robe the miraculous in the mundane?
‘Quaiche?’ the suit asked. ‘Are you still here?’
‘I’m still here,’ he said. ‘But I’m not listening to you. I don’t believe what you say to me.’
‘If you don’t, someone else will.’
He pointed at the scrimshaw suit, his own bony-fingered hand hovering in his peripheral vision like some detached phantasm. ‘I won’t let anyone else be poisoned by your lies.’
‘Unless they have something you want very badly,’ the scrimshaw suit said. ‘Then, of course, you might change your mind.’
His hand wavered. He felt cold suddenly. He was in the presence of evil. And it knew more about his schemes than it had any right to.
He pressed the intercom control on his couch. ‘Grelier,’ he snapped. ‘Grelier, come here this instant. I need new blood.’
TWENTY-SIX
The next day Rashmika got her first view of the bridge.
There was no fanfare. She was inside the caravan, in the forward observation deck of one of the two leading vehicles, having forsworn any further trips to the roof after the incident with the mirror-faced Observer.
She had been warned that they were now very close to the edge of the fissure, but for all the long kilometres of the approach there had been no change in the topography of the landscape. The caravan — longer than ever now, having picked up several more sections along the way — was winding its ponderous way through a sheer-sided ice canyon. Occasionally the moving machines scraped against the blue-veined canyon walls, which were twice as high as the tallest vehicle in the procession, dislodging tonnes of ice. It had always been hazardous for the walkers making their way to the equator on foot, but now that they had to traverse the same narrow defile as the caravan, it must have been downright terrifying. There was no room for the caravan to steer around them now, so they had to let it roll over them, making sure they were not aligned with the wheels, treads or stomping mechanical feet. If the machines didn’t get them, the falling ice-boulders probably would. Rashmika watched with a mingled sense of horror and sympathy as the parties vanished from view beneath the huge hull of the caravan. There was no way to tell if they made it out the other side, and she doubted that the caravan would stop if there was an accident.
There came a point where the canyon made a gentle curve to the right, blocking any view of the oncoming scenery for several minutes, and then suddenly there was an awful, heart-stopping absence in the landscape. She had not realised how used she had become to seeing white crags stepping into the distance. Now the ground fell away and the deep black sky dropped much lower than it had before, like a curtain whose tangled lower hem had just unfurled to its fullest extent. The sky bit hungrily into the land.
The road emerged from the canyon and ran along a ledge that skirted one wall of Ginnungagap Rift. To the left of the road, the sheer-sided canyon wall lurched higher; to the right, there was nothing at all. The road was just broad enough to accommodate the two-vehicle-wide procession, with the right-hand sides of the right-hand vehicles never more than two or three metres from the very edge. Rashmika looked back along the extended, motley train of the caravan — which was now thrillingly visible in its entirety as it had never been before — and saw wheels, treads, crawler plates, piston-driven limbs and flexing carapacial segments picking their way daintily along the edge, scuffing tonnes of ice into the abyss with each misplaced tread or impact. All along the caravan, the individual masters were steering and correcting like crazy, trying to navigate the fine line between smashing against the wall on the left and plunging over the side on the right. They couldn’t slow down because the whole point of this short cut was to make up valuable lost time. Rashmika wondered what would happen to the rest of the caravan if one of the elements got it wrong and went over the side. She had seen the inter-caravan couplings, but had no idea how strong they were. Would that one errant machine take the whole lot with it, or fall gallantly alone, leaving the others to close up the gap in the procession? Was there some nightmarish protocol for deciding such things in advance: a slackening of the couplings, perhaps?