“Why is that?”
“Marking the position of a star for another observer in the universe is hardly as easy as people imagine. Here’s an analogy: You’re taking a plane through the Sahara Desert and a grain of sand below you shouts ‘Here I am!’ You hear the shout, but can you fix a location for that grain of sand from the plane? There are nearly two hundred billion stars in the Milky Way. It’s practically a desert of stars.”
Luo Ji nodded in apparent relief. “I understand. So that’s it, then.”
“What is?” Ringier asked in confusion.
Luo Ji didn’t answer, but asked instead, “Using our present level of technology, is there a way to indicate the position of a star in the universe?”
“Yes, by using directed very high frequency electromagnetic waves, equal to or higher in frequency than visible light, and then harnessing stellar power to transmit information. In simple terms, you’d make the star flash, like a cosmic lighthouse.”
“This far exceeds our present technical capabilities.”
“Oh, I’m sorry. I overlooked your precondition. At our present technical capabilities, it would be fairly difficult to show a star’s position to the far reaches of the universe. There’s still a way, but interpreting the positional information requires a level of technology far beyond that of humanity, and even, I believe, beyond that of Trisolaris.”
“Tell me about that approach.”
“The key information is the relative position of stars. If you specify a region of space in the Milky Way that contains a sufficient number of stars—perhaps a few dozen would be sufficient—their relative arrangement in three-dimensional space would be totally unique, like a fingerprint.”
“I’m starting to understand. We send out a message containing the position of the star we wish to point out, relative to the surrounding stars, and the recipient compares the data to its star map to determine the star’s location.”
“Right. But things aren’t that simple. The recipient must possess a three-dimensional model of the entire galaxy that precisely indicates the relative position of every one of a hundred billion stars. Then, after receiving our message, they would have to search through that enormous database to find an area of space that matches the pattern of positions we sent out.”
“No, it’s not simple at all. It’s like recording the relative position of every grain of sand in the desert.”
“Even harder than that. The Milky Way, unlike the desert, is in motion, and the relative positions of its stars are constantly changing. The later the position information is received, the greater the error caused by these changes. This means the database has to be able to predict the changes in position of each of those hundred billion stars. In theory, it’s not a problem, but to actually do it… God…”
“Would it be hard for us to send that positional information?”
“No, because we would only need to have a position pattern for a limited number of stars. And now that I’ve had time to think about it, given the average stellar density of the outer arm of the galaxy, a position pattern with no more than thirty stars should be sufficient. That’s a small amount of information.”
“Good. Now I’ll ask a third question: Outside the Solar System, there are other stars with planets. You’ve discovered several hundred, right?”
“More than a thousand to date.”
“And the closest to the sun?”
“244J2E1, sixteen light-years from the sun.”
“As I remember it, the serial numbers are set like this: the prefix digits represent the order of discovery; the letters J, E, and X stand for Jupiter-type planets, Earth-type planets, and other planets, respectively; and the digits following the letter indicate the number of that type of planet in the system.”
“That’s right. 244J2E1 is a star with three planets, two of them Jupiter-type and one Earth-type.”
Luo Ji thought for a moment, then shook his head. “That’s too close. How about a little farther, like… around fifty light-years?”
“187J3X1, 49.5 light-years from the sun.”
“That one’s fine. Can you draw up a position pattern for that star?”
“Of course I can.”
“How long would it take? Would you need help?”
“I can do it here if there’s a computer with Internet. For a pattern of, say, thirty stars, I can give it to you tonight.”
“What time is it now? It’s not nighttime already?”
“I’d say it’s probably morning, Dr. Luo.”
Ringier went to the computer room next door, and Luo Ji called in Kent and Zhang Xiang. He first explained to Kent that he wanted the PDC to hold the next Wallfacer hearing as soon as possible.
Kent said, “There are lots of PDC meetings these days. Once you’ve submitted the application, you’ll probably only have to wait a few days.”
“Then I’ll have to wait. But I’d really like it as soon as possible. Also, I have a request: to attend the hearing here via video rather than go to the UN.”
Kent looked reluctant. “Dr. Luo, don’t you think that’s a little inappropriate? For such a high-level international meeting… It’s a question of respect for the participants.”
“It’s part of the plan. All those bizarre requests I made in the past were fulfilled, but this one’s over the line?”
“You know…” Kent faltered.
“I know that a Wallfacer’s status isn’t like it once was, but I insist on this.” When he continued, it was in a softer voice, even though he knew that the sophons hanging in the vicinity could still hear. “There are two possibilities now: One, if everything is like it used to be, I wouldn’t mind going to the UN. But there’s another possibility: I may be in a very dangerous situation, and I can’t take that risk.”
Then he said to Zhang Xiang, “That’s why I’ve brought you here. We may become a target for a concentrated enemy attack, so security must be strengthened.”
“Don’t worry, Dr. Luo. We’re located two hundred meters below ground. The area above us is under lockdown, an antimissile system has been deployed, and a state-of-the-art subterranean warning system has been installed to detect the digging of a tunnel from any direction. I guarantee to you that our security is foolproof.”
When the two men left, Luo Ji took a walk down the hallway, his thoughts turning involuntarily to the Garden of Eden (he knew its name now, but still called it that in his heart) and its lake and snow peak. He knew that it was quite likely he would spend the rest of his life underground.
He looked around at the sunlamps in the hallway ceiling. The light they emitted was nothing like the sun.
Two meteors moved slowly across the starfield. All was dark on the ground, and the distant horizon blended into one with the night sky. A burst of whispers sounded through the dark, although the speakers remained unseen, as if the voices themselves were invisible creatures floating in the darkness.
With a clink, a small flame appeared in the darkness, its dim light revealing three faces: Qin Shi Huang, Aristotle, and Von Neumann. The flame came from a lighter in Aristotle’s hand. When a few torches were extended, he lit one, which then passed fire among the others to form a shaky light in the wilderness and illuminate a group of people drawn from every era. Their whispers continued.
Qin Shi Huang leapt up on a stone and brandished his sword, and the crowd fell silent.
“The Lord has issued a new command: Destroy Wallfacer Luo Ji,” he said.
“We too have received this command. This is the second assassination order that the Lord has issued for Luo Ji,” Mozi said.