“Well, then, you see, universes actually are of different ages. They might appear absolutely identical, except for your choice of breakfast this morning, but one of them is twelve billion years old, and the other is”—she looked at her watch—“well, a few hours old now. Of course, the daughter universe would seem to be billions of years old, but it wouldn’t really be.”

Mary frowned. “Umm, Louise, you’re not by any chance a creationist, are you?”

“Quoi?” But then she laughed. “No, no, no—but I see the parallel you’re alluding to. No, I’m talking real physics here.”

“If you say so. But how does this get Ponter home?”

“Well, assume this universe, the one you and I are in right now, is the original one in which Homo sapiens became conscious—the one that initially split from the universe in which Neanderthals became conscious instead. All the other googolplex of universes in which conscious Homo sapiens exist are daughters, or granddaughters, or great-great-great-great-granddaughters, of this one.”

“That’s a huge assumption,” said Mary.

“It would be, if we had no other evidence. But we do have evidence that this particular universe is special—Ponter’s arrival here, out of all the places he might have gone. When Ponter’s quantum computer ran out of universes in which other versions of itself existed, what did it do? Why, it reached across to universes in which it didn’t exist. And, in doing so, it latched first onto the one that had initially split from the entire tree of those in which it did exist, the one that, forty thousand years previously, had started on another path, with another kind of humanity in charge. Of course, as soon as it reached a universe in which a quantum computer didn’t exist in the same spot, the factoring process crashed and the contact between the two worlds was broken. But if Ponter’s people repeat the exact process that led to him being marooned here, I think there’s a real chance that the portal to this specific universe, the one that first split from their timeline, will be re-created.”

“That’s a lot of ifs,” said Mary. “Besides, if they could repeat the experiment, why haven’t they already?”

“I don’t know,” said Louise. “But if I’m right, the doorway to Ponter’s world may open again.”

Mary felt her stomach fluttering—and not just because of the potato chips—as she tried to sort out her feelings about that possibility.

Chapter 43

Adikor Huld stared at the mining robot Dern had provided. It was a sorry-looking contraption: just an arrangement of gears and pulleys and mechanical pincers, vaguely resembling a stubby pine tree denuded of needles. The robot had obviously endured a fire at some point; there had been one in the mine about four months ago, Adikor recalled. Some of the robot’s components had fused, some metal parts were extensively fatigued, and the whole thing had a blackened, sooty look to it. Dern had said this unit was to have been sent to the recycling yards, anyway, so no one would mind if it were lost.

It was tricky determining how to control the robot, though. Although there were robots with artificial intelligence, they were very expensive. This one didn’t have the smarts to do what needed to be done on its own; it would have to be operated by remote control. They couldn’t use radio signals; those would interfere with the quantum registers, ruining the attempt to reproduce the experiment. Dern finally decided to simply run a fiber-optic cable from the robot’s torso back into a small control box, which he perched on a console in the quantum-computing control room. He used twin joysticks to move the robot’s hands, having the machine press down on the top of register 69 just as Ponter had originally done.

Adikor looked at Dern. “All set?”

Dern nodded.

He looked at Jasmel, who was also present. “Ready?”

“Yes.”

“Ten,” said Adikor, standing next to his control unit; he shouted the countdown just as he had the first time, even though there was no one out on the computing floor to hear him.

“Nine.” He desperately hoped this would work—for Ponter’s sake, and for his own.

“Eight. Seven. Six.”

He looked at Dern.

“Five. Four. Three.”

He smiled encouragingly at Jasmel.

“Two. One. Zero.”

“Hey!” shouted Dern. His control box jerked off the desk and clattered to the floor, skittering across it as the fiber-optic cable coming out of its back end was pulled tight.

Adikor felt a great wind swirling about, but his ears didn’t pop; there was no significant change in pressure. It was as if air was simply being exchanged …

Jasmel’s mouth formed the words, “I don’t believe it,” but whatever sound she was making was drowned out by the wind.

Dern, dashing across the room, had stopped the console from being pulled farther by clamping down on its cable with his right foot. Adikor hurried over to the window to look down on the computing floor.

The robot was gone, but—

–but the cable was pulled taut, half an armspan above the floor, stretching from the open control-room door to three-quarters of the way across the computing facility, until—

Until it disappeared, into thin air, as if through an invisible hole in an invisible wall, right next to register column 69.

Adikor looked at Dern. Dern looked at Jasmel. Jasmel looked at Adikor. They hurried over to the monitor, which should be displaying whatever the robot’s camera eye was seeing. But it was just an empty, black square.

“The robot’s been destroyed,” said Jasmel. “Just like my father.”

“Maybe,” said Dern. “Or maybe video signals can’t travel through that—whatever that is.”

“Or else,” said Adikor, “maybe it’s just emerged into a completely dark room.”

“What—what do you suppose we should do?” asked Jasmel.

Dern shrugged his rounded shoulders slightly.

Adikor said, “Let’s haul it back in—see if anything can survive going … going through.” He walked out onto the computing floor and gently took hold of the cable, disappearing a few paces away into nothingness at waist height. He added his other hand and began to pull gently.

Jasmel came over to be behind him, and she began to pull gently as well.

The cable was hauling back easily enough, but it was obvious to Adikor, at least, that there was a weight hanging off the end, as if, somewhere on the other side of the hole, the robot was dangling over a precipice.

“How strong are the connectors on the robot’s end of the cable?” asked Adikor, shooting a glance at Dern, who, now that he no longer had to hold down his control box, had come out onto the computing floor as well.

“They’re just standard bedonk plugs.”

“Will they come free?”

“If you jerk them hard enough. There are little clips that snap onto the cable’s connector to help hold it in place.”

Adikor and Jasmel continued to pull gently. “And did you engage the clips?”

“I—I’m not sure,” said Dern. “I mean, maybe. I was plugging and unplugging the cable a fair bit as I set the robot up …”

Adikor and Jasmel had already hauled in perhaps three armspans’ worth of cable, and—

“Look!” said Jasmel.

The robot’s squat form was emerging through—well, through what they couldn’t say. But the machine’s base was now visible, as if somehow it were passing through a hole in midair that precisely matched the robot’s cross-section.

Dern hurried across the computing chamber, the closed ends of his pant making loud slapping sounds against the polished rock of the floor. He reached out and grabbed one of the robot’s spindly arms, now partially protruding from the air. He was just in time, too, for the cable connector did give way, and Adikor and Jasmel went tumbling backwards, him falling on her. They quickly got to their feet and saw Dern finish pulling the robot through from—the phrase came again into Adikor’s mind—from the other side.