The ColU said, “They may not have been people at all. This is Per Ardua. Remember we had evidence that there was a builder Culture that achieved planetary engineering. Maybe this is somehow a legacy of that.”
Titus was frowning. “I am trying to work this out. So my torch will have slid along this tunnel to the terminus. And then, with nobody to collect it—or so I presume—it will have started to slide straight back again. You say we must wait only a few minutes, ColU. Do you mean until my torch returns? But how can you know that? You don’t know how long this tunnel is…”
“It doesn’t matter,” the ColU said. “It’s an odd quirk of physics. The time the journey takes only depends on the density of the planet, the gravitational constant… Even if you could cut a tunnel right through the center of the planet—”
“Which would have been handy getting from substellar to antistellar,” Stef said drily.
“Even then, though you’d have reached much higher speeds at the midpoint, the journey time there and back would be the same.”
Titus said, “All this sounds like philosophical trickery to me. And how long is this magic transport time you predict, O glass demon?”
The ColU said, “Just wait… About this long.”
And, right on cue, a bundle of reeds came sliding up out of the mouth of the tunnel. As it slowed to a halt, Titus carefully reached down and swept it up with his one good hand. “Ha! A fine trick, demon. But now we have some planning to do. Come! Let us return to camp.”
The first trip through the gravity tunnel, Titus decreed, was to be made by sled, Beth’s cart, with the runners they had made to replace the axles and wheels on the undersurface. Of course they had anticipated having to drag the cart over farside ice, but Stef could see that this arrangement ought to work even better in the frictionless tunnel.
So they wheeled the cart the couple of miles to the tunnel mouth, established a temporary camp, spent a day fixing up the cart with its sled rails. They ate and slept, according to Titus’s stern orders.
Titus decreed that the first to take a trial trip through the tunnel would be himself with his daughter Clodia—and the ColU and Stef, who might be able to interpret the experience, and what they found on the far side. The pregnant Mardina, the baby’s father, Chu, and prospective grandmother Beth, would not be split up come what may; they would be staying behind.
They were evidently going to have to do some fancy work getting the crew loaded on at one end of the tunnel, and successfully off at the other before the sled started to fall back, without any outside help. Before they hauled the cart over to the tunnel Titus had them practice the art. They had most success with Titus and Clodia leaping out at the destination, carrying rope to tie up the cart, while Stef stayed in the cart cradling the ColU.
Then the cart crew bundled up in their warmest gear—they were after all going an unknown distance deeper into the chill of farside—and loaded food, water, blankets, material for a fire, and a few of their precious tools, onto the cart itself. Beth, Mardina and Chu had an easy enough time pushing the cart over the lip of the sloping tunnel, and held it steady while the passengers climbed aboard.
Then Titus ceremoniously lit a torch and held it aloft. “Onward, and into the unknown!”
The support crew let go of the cart. Slowly, almost imperceptibly, it began to slip down the slope.
Stef glanced back at the grinning, somewhat anxious faces of her companions. “It’s taking an embarrassingly long time to get going,” she said. “I feel like the King of Angleterre in his coronation carriage.”
“We will be in the dark soon enough,” the ColU said. “But remember, even if the torch were to fail, it is only forty minutes to complete the one-way trip to the far end.”
Now the mouth of the tunnel was all around them, swallowing them up, their speed gradually increasing. The dark was deepening now. The movement was utterly smooth, and entirely silent.
Stef felt a frisson of fear. “It’s like a roller-coaster ride. Magic Mountain at Disneyland. None of you have the faintest idea what I’m talking about, do you?”
Titus, cradling his torch with his burly body, was suspicious. “I don’t understand. We are moving quite rapidly already. And yet there is not a breath of wind.”
“As I anticipated,” the ColU said smoothly.
Stef snarled, “What now, ColU? I wish you’d be open with us.”
“I apologize, Colonel Kalinski. There could be no air resistance in here. Otherwise, you see, the friction would slow us; we might pass the midpoint but would not reach the tunnel end, and would slip back, eventually settling at the center, the lowest point. Human engineering designs based on this idea always imagined a vacuum tunnel.”
Titus took a deep breath. “We’re in no vacuum.”
“I think there is an invisible subtlety to the design. The air we breathe is carried with us—perhaps the tunnel air is held aside. Given time, Stef Kalinski, you and I could no doubt investigate the engineering. Whatever the detail, it must be robust to have survived a billion years…”
The dark was deep now. They didn’t seem to be moving at all, and Stef soon lost track of time. In the light of the torch, Clodia cuddled closer to her father.
Stef, unable to resist it, moved closer to the big Roman too.
Titus said, “I am sorry I do not have a hand for you to hold, Stef.”
She clutched his stump of an arm and rested her head on his shoulder. “This will do.”
“It won’t be long,” the ColU murmured, from the dark. “Just forty minutes. Not long.”
They emerged on an icebound plain.
Stef walked a few steps, away from the tunnel mouth and the disgorged cart. She swung her arms, breathing in deeply; the cold stung her mouth, and her breath steamed. “This is the far side, all right. Just the way I remember it.”
She looked around. Andromeda still hung huge and looming in a crystal-clear sky; there wasn’t a shred of terminator-weather cloud here. In the crimson galaxy light, the land seemed featureless, flat. But there was a peculiarly symmetrical hillock in the ice a few hundred meters away, like a flattened cone, or a pyramid with multiple flat sides—or like a tremendous jewel, she thought. Could it be artificial? There was no other feature in the landscape to draw her eye.
She walked that way, trying to place her booted feet on ridges in the ice to avoid slipping.
Inevitably Titus called after her. “Don’t go too far!”
She snorted. “I’m hardly likely to have marauding barbarians leap out at me, legionary.”
“You might slip and break your brittle old-lady bones. And with my single arm it would be a chore for me to have to carry you back to the cart and haul you home.”
“I’ll try to be considerate.”
The ColU called, “In fact, Colonel Kalinski, would you mind carrying my slate for a closer inspection? And if you could find a way to bring back a sample of that formation…” With surprising grace on the ice, Clodia jogged out to hand Stef the slate, and a small hammer from their rudimentary tool kit.
As Stef approached the pyramidal structure, she listened to the ColU’s analysis.
“I can deduce our change in position quite clearly from the shift in the visible stars’ position. Andromeda has shifted too of course, but that is too large and messy an object to yield a precise reading…”
The closer she got, the less like a geological formation the pyramid seemed. It was too precise, too sharply defined for that. She supposed there might be a comparison with something like a quartz crystal. But she had an instinct that there was biology at work here, something more than mere physics and chemistry. She took panoramic and close-up images. The pyramid looked spectacular and utterly alien, sitting as it was beneath a sky full of galaxy. Then she bent to chip off a sample from one gleaming, perfect edge.