“But this ancient philosopher, Wigner, took that logic a step further,” Nilis said. “Any observer is herself a quantum object — everything is, we all are — and therefore herself subject to quantum uncertainty. You need a second observer to make her real, and thence to make her observation real. If Wigner is the first observer, his friend is the second.”
Pirius thought that over. “But what about the friends quantum function? That isn’t made definite until a third observer makes an observation of her.”
“You have it,” said Nilis approvingly. “And then you need a fourth, and a fifth.”
Pirius’s head was swimming with infinities. “But no matter how many observers you have, how many friends of Wigner you line up, you always need one more. So nothing can be real.”
“This was called the paradox of Wigner’s friends,” Nilis said. “But the Friends believed they had a resolution.”
The chains of unresolved quantum states will build on and on, growing like flowers, extending into the future. At last the great chains of quantum functions would finally merge at the last boundary of the universe, at timelike infinity.
“And there, argued the Friends, will reside the Ultimate Observer, the last sentient being of all. All quantum functions, all world lines, must terminate in the Observer — for otherwise, she would not be the last. The Observer will make a single climactic Observation—”
“And the chains of observations will collapse.”
“History will be made real at last, but only at its very end.”
Pirius said, “But I don’t see how this was going to help the Friends get rid of the Qax.”
The Friends had come to believe that the Ultimate Observer might not be a passive eye, but that this final being might have a choice: that she might be able to exert an influence on how the chains of quantum functions were collapsed, on which cosmic history out of the many possible was selected.
“And if a being has such power,” Nilis said, “perhaps she can be lobbied. And that was what the Friends intended to do. They were going to send the Ultimate Observer a message.”
“How? With Jupiter?”
“Singularities themselves have structure, you know. The singularity at the heart of the Jupiter black hole was to be shaped, and loaded with information. It would be a plea to the Ultimate Observer. The Friends wanted the Observer to select her chosen history to favor humanity — in particular, to pick out a causal line that would not include the Qax Occupation.”
Pirius thought that over, and laughed, wondering. “That’s astonishing.”
Nilis said, “It’s a terribly nihilistic philosophy — don’t you think? Just like their modern intellectual descendants, the Friends actually seem to have believed that they, their memories, their whole lives would be wiped out of existence when the Ultimate Observer makes her choice and some optimal timeline is plucked out of the quantum tangle. The Friends were not just escaping the Qax, Ensign. Perhaps they were escaping from themselves.”
Pirius wasn’t convinced. He thought of Enduring Hope, back in the Core; if you were stuck in the middle of an endless war, the notion of an end-of-time arbiter who would one day delete all the pain from the world was a comforting idea.
But he had believed it was myth. He hadn’t known that this airy nonsense about a cleansing at the end of the universe might actually have some physics in it. It was a spooky thought.
“Of course their scheme was overcomplicated, and it didn’t work,” Nilis said. “The Friends didn’t even manage to make their black hole properly, let alone send their plea to the end of time. They managed to destroy Jupiter, though.”
The Qax responded to the treachery of the Friends with devastating force. No longer would their rule be light; no longer could human cultural artifacts be used to camouflage rebellion. The Extirpation began: human history would be deleted, human minds wiped clean, even the fossils in the ground would be pulverized. The Qax intended that humans would never pose a threat to the Qax again. They came close to succeeding.
The Friends’ black hole technology was suppressed. And after the Occupation, when the Coalition came to power, such ancient horrors were suppressed again. But a handful of pharaohs kept the old knowledge alive, tucked away where even the long arm of the Commission for Historical Truth could not find it. The pharaohs had always known a day would come when it would be needed again.
They fell silent.
“I have a new assignment for you,” Nilis said hesitantly. “You might find it sticky.”
“Sticky?”
“I need you to think about Pirius Blue.”
Pirius hadn’t thought about his temporal twin for days. “Why?”
It turned out that Blue had been having adventures of his own. Astonishingly, he had flown a ship deep into the Cavity, to scout the Prime Radiant itself.
“I’m trying to build up a picture of Chandra — its nature, its surrounds,” Nilis said earnestly. “I have the material I discovered in the Olympus Archive, the data from the neutrino telescope, and now Blue’s firsthand experience. I need to put it all together — to assemble a theoretical model of our objective. I was there, you know,” he said with a sort of modest pride. “In the Cavity. I sent in an avatar to ride with Pirius Blue. I like to think I acquitted myself well enough! But even that experience isn’t enough. I need to know what Blue himself perceived.”
Pirius nodded slowly. “So why don’t you talk to him?”
“It is a question of nuances,” Nilis said. He reached out his big hands toward Pirius. “I’m not sure I understand you, you see. We discussed this before. Our backgrounds are so different! Of course nobody knows Pirius Blue as well as you do. Nobody will be able to understand his words, his body language — what remains unsaid — as well as you. This is very important. Listen to your time brother, Pirius Red; listen to his feelings…”
Pirius took the assignment.
For the rest of the day, he sat in Nilis’s musty cabin watching Virtual recordings of Pirius Blue, more battered, more weary, even older, as he described his extraordinary jaunt into the core.
Pirius Red still felt a lingering resentment at this stranger from the future who had sent him into involuntary exile. But mostly, Red felt envy: envy for a man who had once more had the opportunity to carry out his duty in the most testing of circumstances, and envy for the companionship of his crew. Watching this scratchy Virtual report, Pirius Red felt shut out, denied.
At the end of the day, Torec and Pirius retired to their small shared room on the corvette. They didn’t speak.
Pirius stripped off his uniform and allowed it to slither into the closet. He got into his bunk, turned his face to the wall and closed his eyes, hoping for sleep. At least he wasn’t on Earth; at least he was back in space, and he could hear the comforting sigh of cycled air, feel the thrumming of the corvette’s drive.
He was surprised when Torec slid into his bunk.
He turned to face her. Her face was so close he could feel her breath on his cheek. Her eyes, dimly visible in the low light, were closed, her mouth tight shut.
He put his hand on her arm. He felt firm flesh and muscle. He whispered, “Things aren’t the same.”
He could feel her roll onto her back. “The trouble is, Pirius, things have changed for me. While you’ve been away, I’ve been useful.”
He knew that was true. There had been her work on the CTC processor, the test flights of the modified greenships, even this early work on the black-hole cannon. He remembered her confusion when they had first been brought to Sol system, when she hadn’t even wanted to get out of bed.