Julian date 2459495, the staff compound at Kashgar station, Saturday.
The crayfish was Zhou Yao's, left behind during last summer's holiday. Her flight got rebooked, carry-on limited to one item, and at security Zhou Yao stood hugging the glass tank for forty seconds, then pushed it into her mother's arms and said: Mom, his name is Lao Wu. Why Lao Wu, Zhou Yao never explained, and she never asked. At the airport farewell she promised three things: change the water weekly, don't overfeed, and watch for the molt. The third was the hardest. Before molting, a crayfish stops eating, hides, its color darkens; on molting night it doesn't move all night, and by morning a complete empty shell lies on the bottom, as if it had taken off its old clothes and folded them. Zhou Yao said the days just after the molt are the most dangerous—the shell is soft, and nobody may touch it.
In her mother's keeping, Lao Wu had molted twice. The first time was last October; she'd gotten up at midnight for water and heard a faint click from the tank, and the next morning there was the empty shell. She photographed it and sent it over; Zhou Yao replied with six exclamation marks. The second time was this April. At that pace, the next was due in October.
She kept a ledger for Lao Wu, in the back pages of the paper notebook: feeding, water changes, water temperature, molts. The first year after Zhou Yao left, the ledger ran patchy; this year it ran complete, because Zhou Yao audited it every Saturday. The October pages were nearly blank except the temperature column. Lao Wu's appetite hadn't dropped, his claws kept gnawing fresh notches into the driftwood, but he simply wouldn't molt. She had looked it up: a crayfish that doesn't molt will die. The shell is the exoskeleton; the flesh grows inside it, the shell doesn't, and sooner or later the body has nowhere to go. The last line of the guide said, please be patient, keeper. She had little confidence in the word "patient." Her own estimates of her patience always ran low; Zhou Yao's ran lower.
November ended, and Lao Wu had not molted.
He ate plenty, his claws were strong, and the driftwood in the tank carried new notches. Only the shell kept darkening, dark till it turned blackish, like a film of gobi dust over it. Zhou Yan messaged Zhou Yao: is Lao Wu due to molt? Zhou Yao replied after school: what's the water temperature? She said: twenty-two. Zhou Yao wrote: drop it two degrees, then wait. Molting depends on the mood. Then one more line: Mom, stop staring at him. The moment you stare he gets tense.
She laid the phone face-down on the table, thinking, what does a crayfish have to be tense about. Then she realized she had in fact been staring, for a long while; her face and the screen of the laptop behind her floated on the tank glass.
On the screen was the new synchronization window.
Saturday she woke late, nine-thirty, boiled a handful of noodles and poached an egg. She ate sitting in front of the tank—the one stretch of her week that wasn't hurried. At the sight of a person Lao Wu backs into a corner, claws folded in front of his chest—not fear, protocol. She scattered a pinch of feed and watched him trap it in the big claw, carry it to his mouthparts: slow, steady movements. The trouble with molting is that shell and flesh are one body: the old support is also the old prison. There are no helpers in a molt; whoever helps it harms it—Zhou Yao had that from the man who sold the crayfish, and the seller probably had it from someone else. The noodles done, she left the bowl soaking in the basin and went out to the machine room.
Once the instruments were buried, the question changed its mode of existence. Before, the shoulder was "where from"; now the shoulder was "how big." She widened the window beyond the three baselines: beyond Kashgar, Miyun, and Nanshan she added Shanghai's Tianma, added a commissioning station at Jiamusi, then pulled Europe and South Africa in from the international data-sharing pool. Twelve stations, eleven pulsars, joint residuals. The window stretched to ninety days.
The work was hers and Hu Yisu's. Hu Yisu was twenty-six, second-year master's, originally with Old Tang on antenna structures; half a year ago he had transferred himself under her, reason given as "data is more interesting." He wrote code faster than she did, and his mouth was faster than his code. The day he delivered the first pipeline he said: Shijie, I used a new interpolation scheme for the window alignment. She read the scheme and said: rewrite it. He asked why. She said: no interpolation before alignment. Interpolation contaminates the word "simultaneous." He said oh, went off and rewrote it, and came back with exactly one sentence: Fine. I dirtied it.
This Saturday he was working overtime in the machine room. At noon he carried up two bowls of banmian and set one on her desk. "Shijie," he said, "let me tell you something, don't take it as me sticking my nose in. That assistance letter of yours last week—the wording steered toward instruments. Someone at Miyun noticed. In the group they're asking, so is it the instruments or not?"
"It is not the instruments," she said. "That's why the letter said what it said."
"Then what do you plan to do now?"
She stirred her noodles and didn't answer that. She pointed at a line of parameters on the screen: eat your lunch, and this afternoon finish the window alignment.
Hu Yisu looked at her for two seconds and put his head down over the bowl. He had this one virtue: a topic he's been deflected from, he never chases—but he remembers, and a few days later he comes back around from another direction. Zhou Yan knew he'd come back around, so she hadn't planned to hide it long; the order simply hadn't arrived. Order, with her, is not a habit but a method. Let only one impossibility happen at a time.
Once the window reached eleven stars, impossibilities were arriving in bulk. Thursday afternoon, when the joint significance crossed three sigma, she stood in the corridor a while and thought about phoning three people: Old Tang, Dr. Shen, and one more person whose name she wouldn't even say inside her own head. She phoned none of them. Old Tang wanted an instrument conclusion; Dr. Shen wanted her ears; the third wanted something he'd wanted twenty years ago. She went back into the machine room and kept running numbers. A choice, made often enough, gets fast—fast enough that at the time you don't notice what it costs.
At three in the afternoon the ninety-day window alignment finished. Eleven pulsars—and of the eleven, whether nine carried shoulders in their residuals was a question for statistics. She made the stacked ephemeris: the nine shoulders fell on the same night. Computed as joint significance over nine independent observations, the number crossed four sigma and landed on the "not coincidence" side.
Hu Yisu stared at the stack plot a long time, long enough for his noodles to clump. He said: Shijie, of these nine stars, the nearest is four hundred light-years away, the farthest—he dug through the archive—the farthest is eleven thousand. From one to another, light takes thousands upon thousands of years. They can't have compared notes.
"I know."
"Light takes thousands of years to get from one to the other. They can't have agreed on it."
"I know."
"Then this—"
"Eat first," she said. "When you're done, bring me the archive page for the nine stars. For each one I want two sets of numbers: galactic longitude and latitude, and dispersion measure."
Hu Yisu didn't eat. He turned his chair around and sat facing away from her a while, then turned back. "Shijie, can I ask a completely amateur question."
"Ask."
"These nine. They're simultaneous."
"Yes."
"So aren't they like—" He stopped, shook his head. "Never mind. Not like."
"Like what?"
"Nothing." He dragged the noodles over and ate two mouthfuls cold. "Like snoring. When I was little my father snored; I could hear it from the next room. But you couldn't say which breath lined up with which breath—only, the whole house was full of it."
Zhou Yan said nothing. There was something wrong with that comparison that she couldn't name, but she remembered it, and went on remembering it for years. The one snoring doesn't know he snores.
At eight in the evening, Zhou Yao's video call came in. The time was an appointment: every Saturday, eight p.m., immovable—the only clause of the divorce agreement she had fought for herself.
At the first ring, the joint window was on its final leg: taking the two most widely separated pulsars—one four hundred light-years out, one eight thousand two hundred—and exiling their residuals onto the same time axis, comparing second by second. Progress bar at eighty percent.
Zhou Yan looked at the name "Zhou Yao" on the phone screen, and at the progress bar on the computer screen. She took the call. Video: Zhou Yao's face filled the screen, hair tied up, saying art class had left a new assignment—draw a family member.
"Draw who?" Zhou Yan pulled the notebook toward her own side as she answered.
"Anyone. The teacher says draw 'someone with their eyes closed'—observation practice; only with the eyes closed can you tell who's paying attention. I'm going to draw you."
"What's wrong with me?"
"You fell asleep during our video last week," Zhou Yao said. "Right there, face-down on the desk, half a minute. Your breathing changed. I took a screenshot."
Zhou Yan remembered—there had been such a night; the window had run past midnight. "Then draw," she said. "Remember the hands."
"I still can't do hands. Mom, what are you running over there?"
"A number." On her side the progress bar reached ninety-one. In the top right corner of the screen, above Zhou Yao's head, hung her ex-husband's ceiling lamp, warm yellow—the look of a household where someone is living properly.
"You said last week you'd show me Lao Wu's shell."
"He didn't molt."
"Not at all? Has the shell gone dark?"
"It has."
Zhou Yao went quiet for a moment on her end. Zhou Yan knew her daughter was holding back blame; at twelve, holding back blame presses the corners of the mouth down—press, hold, then speak, and the voice comes level. "Did you lower the temperature?"
"I did. The day before yesterday."
"Then you wait. Wait for him to work it out himself." Zhou Yao said, "Mom, how many times have I told you—staring at him is useless. With molting, whoever helps it harms it."
Ninety-four percent. Zhou Yan's eyes went back to the progress bar. Zhou Yao saw. Twelve-year-olds see everything.
"Mom."
"Mm."
"Are you listening to me?"
"Listening," Zhou Yan said. "I remember about Lao Wu. Water change Wednesday."
"I'm talking about me," Zhou Yao said. "About drawing you."
The bar jumped to ninety-seven. Zhou Yan switched the phone from her left hand to her right; the right hand is nearer the computer. She said: "Yaoyao, I hear you. Someone with her eyes closed, draw me. Water change Wednesday, and Saturday I'll call you early—"
"Mom, are you running that number again?"
Ninety-eight.
"One minute," Zhou Yan said. "Wait one minute for me. Just one."
Zhou Yao said nothing. In the screen the girl looked at her for three seconds, a look that wasn't a child's look—it was her own look; that's how Zhou Yan looked at shoulders in data. Then Zhou Yao said: "Fine." The camera went face-up at the ceiling, wobbling, with the sound of pages turning.
One hundred percent.
The plot sprang open. Two stars, four hundred light-years and eight thousand two hundred, two residual curves laid over the same time axis, rolling past in segments of zero point three seconds. Eight thousand two hundred light-years. Light leaving that star, walking to Earth, walking all the way to humanity inventing the radio telescope, walking to Zhou Yan sitting down in this machine room, took eight thousand two hundred years. Every twitch it made could be seen, if at all, eight thousand two hundred years later.
At second thirty-seven, both curves lifted at once.
Not one after the other. At once. On a time axis pinned down by the clock ensemble to a billionth of a second, a nearby star and a star eight thousand two hundred light-years away, in the same instant, each gave one twitch—the same shape, the same width, like two fingers of the same hand flexing at the same time.
Zero lag. Within error, zero.
She played that stretch back three times. The first time she suspected the clock ensemble; the second time she suspected the module Hu Yisu had rewritten in her alignment script; the third time she suspected nothing and only watched. The two curves walked side by side down the time axis: when it was one's turn to move, it moved; when it was nobody's turn, neither moved. She thought of Hu Yisu's unfinished sentence from the afternoon—like what; the word he hadn't dared say out loud, she tried thinking it for him, and couldn't. What can't be thought can't go in the notebook. All that could be written was: one moment, two places, one movement. Tomorrow morning, Hu Yisu was to recompute independently, in his own environment, the two of them barred from comparing code. That was everything she could do now, and the only honest way to do it.
Zhou Yan heard her own heartbeat skip a beat. She looked back at the phone—screen to the ceiling, and from the other side the slow sound of pages turning, deliberately slow. She picked the phone up and turned it on herself.
"Yaoyao," she said, "I'm sorry. That number just now—there was no stopping it."
"And if you had stopped it?"
"It would drop out," she said. "Drop out, and it can never be joined again."
Zhou Yao looked at her a long moment, then suddenly asked a completely unrelated question: "Mom, what's that star's name?"
Zhou Yan was caught off guard. She looked down at the archive page and read it out to her daughter: a string of numbers, letters plus digits. Zhou Yao listened and said: "That long. I'll show you when I've drawn it." And hung up.
Zhou Yan set the phone down on the table, screen facing down.
Call log: seven minutes forty seconds. She remembered every word just spoken, and which one she hadn't answered. Her daughter asked what the star's name was; that wasn't a question needing an answer, it was a question needing her to stop. Had she stopped? She wasn't sure.
In the tank Lao Wu lay against the glass, shell a dull black, motionless. Zhou Yan watched him a while, then pulled the paper notebook over, opened a fresh page, and wrote: two stars, synchronized, zero lag. Eight thousand two hundred light-years.
She paused, then added a line beneath: Zhou Yao asked the star's name.
The pen went down very lightly, as if afraid of waking someone.