Julian date 2459483, Kashgar, 3:11 a.m.
Zhou Yan saw it with her own eyes first. She would tell people this again and again later, with no embellishment: not a program alarm, not a confidence popup—her eyes. The residual histogram came up on the screen, and at the right shoulder there was an extra bump, like a jacket on a hanger with padding slipped under the shoulder seam. The fitting curve passed over it smoothly, with perfect self-assurance, because the chi-square test said nothing was wrong. The chi-square test cannot see a shoulder. She could.
She stared at that shoulder for about four minutes, then reached for the cup at the corner of the desk. The cup was cold, and so was the water. She was alone in the duty room; the heating drops a notch in the small hours—station rule, to save power. She finished the water and reran the pipeline from the raw survey data, skipping the two lines of smoothing parameters she had hand-edited the night before. The shoulder was still there.
For a moment she did suspect her own two edited lines—pure routine, once a quarter, coefficients of the solar wind model. She rolled the changes back; the shoulder did not move a hair. She put the changes back; the shoulder still did not move a hair. Nothing to do with her. Rare, in data: a thing so clean it has nothing to do with you, and precisely because of that you don't dare trust it.
By procedure, she should have written an anomaly report to the observatory right then. She didn't. She created a new directory, gave it a name in a format the station rarely used, letters plus underscore, so it looked like system-generated cache. She tucked the histogram and the residual table into it, turned off the screen, and sat in the dark.
Outside the window was the gobi. The late-November gobi at night has nothing—no lights, no trees, only a seventy-meter dish standing two kilometers away, the feed cabin hanging at its focus on a single steel cable. During the daytime inspection she had touched that cable; today it carried frost, one finger wide, crisp under a fingertip, and the crumbs that fell off glinted once in the sunlight and were gone. Eli, the old technician, said the frost had come early this year, nine days earlier than last. Nine days. She had written that number on the back of the maintenance sheet, for no reason, except that there was a pen in her hand.
The dish was tracking pulsars. Timing-array work, stripped to its essentials, is dull: watch the most punctual clocks in the universe, record their time year after year, subtract the Doppler from Earth's orbit and rotation, subtract the interstellar medium delay, subtract clock error, instrument error, attitude error, and subtract until the small change left over at the end—call it the residual. Residuals should be white noise. Should be sand. Eight pulsars, eight lines of sand; she had kept them six years and knew with her eyes closed how each line jittered.
The things subtracted had a list, and she could recite it: Doppler from Earth's orbit, one sine per year; Earth's rotation, one per day; solar wind dispersion, tracking the solar activity index; atomic clock offsets, read daily from the bulletins issued by the BIPM; even the ionized hydrogen column along the line of sight had to be patched in from the dust maps. When she took the job eight years ago the list had eleven items; now it had twenty-three. People who run timing arrays spend their whole lives subtracting—explain away everything that can be explained, and only then does the sand left over deserve to be called a residual. What she liked about the trade was right here: no glory. No one in the sky checks whether you subtract correctly. Only the sand knows.
Now one of those lines had grown a shoulder in its sand.
She gave the shoulder a provisional number, wrote it in her own notebook, not in the system. The notebook was paper, from the station shop, three and a half yuan. She wrote hard; you could feel the ridges on the back of the page.
At 4:20 a.m. she pulled the J1713 baseline out alone and recomputed it for two hours. The shoulder's significance fell short; on a single line, it could at any moment pass for a noise tail grown too fat.
She tried torturing it. Drop the two days with the worst ionosphere data, and the shoulder faded a little; change the weights from uniform to signal-to-noise, and the shoulder came back; switch window functions, and the shoulder moved by less than one sample point. She drew a two-by-two table in her notebook, four treatments, and the shoulder alive in all four cells. Things that survive torture have only two destinations: either real, or she was wrong. A machine room at four in the morning offers no third answer. She needed more lines. She needed Miyun, needed Nanshan, ideally also some station on the far side of the Earth—any one. In the duty log she wrote: routine pipeline validation, involves cross-station data request. Signed it, closed it, went back and slept two hours. Slept deep. She had always been that kind of person—could sleep with the sky falling—and that was exactly what her ex-husband couldn't stand, back then. He said: you're not easygoing. You're missing a piece.
The missing piece went off and did other things later. She never thought it through.
Ten a.m., the ENT department of the county hospital. Her name on the registration slip was mistyped—衍 typed as 演, same sound, wrong character—and she didn't go get it fixed.
Seven people sat on the waiting bench, two of them children, one old man cleaning his ears with cotton. She could hear the calling screen, Mandarin once, Uyghur once. She was number eleven and waited forty minutes; for those forty minutes she queued up the follow-on processing for three baselines in her head. When her turn came, the nurse read out the wrong Yan. She stood up and answered to it.
This was her fifth year of follow-ups. Strictly speaking, the third time in five years she had actually come—for two years in between, she had worked a connection to cover the record. The connection was a college classmate, now at this hospital, Dr. Shen. Shen wasn't on clinic duty today; the one on duty was young, badge reading resident trainee. The audiometry booth door was as thick as a bank vault: inside, one chair, one headset, one button. Tones came one at a time through the headset, left ear first, pure tones, starting at one thousand hertz and climbing step by step. At four thousand hertz she hesitated—that tone she heard, but as if through a layer of wet glass, and she could not be sure whether she had heard it or guessed it. Audiometry punishes the honest: press early and it's a guess; press late and it's not there. She pressed. She knew before the result came up that she had pressed wrong. The young man pulled up the pure-tone audiogram, looked at it a while, then a while longer.
"The low frequencies are fine," he said. "On the high side, four thousand hertz has dropped more than last time. Do you wear a hearing aid?"
"No need," she said. "I sit in the front row at meetings."
"Your last record is from two years ago," the young man said, scrolling. "Nothing in between?"
"Yes, in Shenzhen. I didn't bring the report."
There was no report in Shenzhen. She had never had her ears checked in Shenzhen. She watched the young man type it into the record—patient reports prior examination elsewhere—his stylus pausing on the tablet, a hesitation, but he wrote it anyway. The hair cells in her cochlea were dying, dying on both sides, faster in the right ear; the medical verdict had traveled from "keep under observation" five years ago to "recommend fitting hearing aids as soon as possible; assess for cochlear implant" today. She heard every word of it clearly. Her left ear still had seventy percent—enough, sitting in this quiet consulting room.
The problem was not here. The problem was that if she were fitted with hearing aids, the station's annual physical would have it on record; with it on record, her duty qualification would go up for review. Does timing-array duty require hearing? Strictly speaking, no written clause. But the feed cabin sits seventy meters up, inspection goes by the external ladder, and the safety code requires "capacity for unaided two-way voice communication." How to read the word "unaided" belongs to the security office, and the security office's reading belongs to a place nobody wants to go ask. She was forty-three. The pipeline at this station was hers, the baselines of the eight stars gnawed down one by one, by her. She did not want to leave it over her ears. Not yet, anyway.
Leaving the room, she messaged Dr. Shen from the corridor: Checked. Stable. Thank you. The reply came fast: Send me the report. She put the phone back in her pocket and answered only at the hospital gate: Paper copy. Another day. She wielded "another day" with great fluency—eleven times in five years, on Dr. Shen. Shen did not reply again.
"No prescription for now," she said. "I'll come next quarter."
The young man looked up, probably about to say something by the book. She got there first: "That four thousand hertz you just mentioned," she pointed at her own ear, "is that the same thing as—that ringing? A hiss?"
"That is high-frequency tinnitus. It suggests the hair cells—"
"I've had it for twenty years," she said. "I'm used to it."
She paid and came out and ate a bowl of banmian at the hospital gate. The chili in it was good; only the noodles had clumped. Sitting on the plastic stool she thought: sounds at the threshold are always there; it's just that no one has ever treated them as signal. She stopped halfway, feeling the thought had come from the wrong direction—it was borrowed from the histogram. Borrowed thoughts are the most dangerous. She swallowed that mouthful and thought no more.
The shuttle back to the station left at two; the driver was Eli's nephew, Uyghur radio on in the car. She sat by the window. Her phone buzzed in her pocket. Zhou Yao, with a picture: art-class homework, a hand, palm open, the fingers a little crooked. One line below: Mom, I can't get the fingers right. Should I be practicing sketches?
She looked at it a long time. The bus went over a bump and the phone shook. She typed: Start with the back of the hand, then the fingers, one at a time. Before sending she deleted "one at a time"—felt it was fussy—then felt it wasn't fussy, and in the end put it back. Sent. Zhou Yao did not reply. Twelve-year-olds don't do the silence of people quitting group chats; their silence means they have gone off to do homework, and that is a good thing. She laid the phone face-down on her leg.
The bus came over the last gentle rise; the station lights came out first, then the red obstruction lamp on the tower, on and off, four seconds a cycle. She watched the red lamp and counted three cycles, and remembered Zhou Yao at four being afraid of a flashing light at that frequency—she said it was like someone blinking. These things have nothing to do with pulsars. She allowed herself twelve minutes on the bus for thoughts like these; the bus arrived, and the quota was spent.
She reached the station at four in the afternoon. She went first to the main machine room: the cross-station data requests to Miyun and Nanshan had come back approved—the letter she had sent that morning in the station's name, reason given as "pipeline validation"; the one on duty at the far end was a student she had trained, and he asked nothing further. The data would take three hours to land on disk. She used the gap to go up the tower.
The feed cabin inspection was supposed to be Eli's. She told Eli she wanted to go up for a breath of air; Eli said what does a data person go up for; she said the signal is better up there. Eli swore something and went off to call his nephew.
The external ladder had four hundred and twelve rungs. Halfway up she was already regretting it; the pressure in her ears shifted as she climbed, and the constant hiss in her right ear sharpened a notch, as if someone had pushed the volume of TV static up one bar. She stood still on the ladder and waited for it to recede. Wind came flat across the gobi, and the tower frame gave off one very low note under her feet. She thought: that note is probably two or three hundred hertz; I can still hear it now; in two years I won't. She drew up a duty roster like that for her own ears, and kept climbing.
Inside the feed cabin it was warmer than outside; the equipment heats itself. She ran the checklist once by the book: waveguide flanges, current on the cryogenic amplifier, ice on the feed horn. All normal. She pulled the cabin's temperature-control log: over the past seventy-two hours the cabin temperature had swung plus or minus zero point four degrees, dead center of tolerance; the cable phase-stability curve was flat enough to put in a textbook; she rapped the waveguide with a knuckle—the sound came back dull, no water inside. All of it normal. And the normal things suddenly made her uneasy—she had come up today to find a fault, and for every minute the fault was not here, the shoulder got one degree more real. The No. 7 feed's connector was a little dirty, oil mixed with dust; she wiped it with anhydrous ethanol and it would not come clean; the stain seemed to have soaked into the grain of the metal. She remembered this stain. She had remembered it since her first climb, six years ago. She thought nothing of it.
She sat in the feed cabin a while and looked out the observation window. The sun was nearly down; the antenna's shadow lay stretched kilometers across the gobi like a dropped needle. Her thoughts were very concrete: if the shoulder was real, it should not appear only on the J1713 baseline; if it appeared on all three baselines, the receivers had to be checked; if the receivers were fine, the inter-station clocks; if the clocks were fine too—she did not allow herself to think past the clocks.
The data landed at 7:06. She skipped dinner, merged the three baselines, and ran a joint residual estimate. The keyboard was loud in the empty machine room. At sixty percent she went for a cup of water; when she came back it was at a hundred, and the plot was out.
Three lines. Kashgar, Miyun, Nanshan. Three stations, three sets of receivers, two sets of atomic clocks. Three residual histograms, and at the right shoulder, a shoulder on each.
Same night. Same shape. She laid the three plots out side by side, zoomed in, zoomed again. Outside the window the sky had gone fully dark; the antenna kept turning, tracking the next star, and the frost on the steel cable now and then caught the searchlight.
She sat there, hands on the keyboard, not moving for a long time. Then she started a new email. The To line was empty; the body was empty. She typed a line in the subject field first, and deleted it. The version that finally went into the drafts folder had a subject of one word:
Shoulder.
She glanced at her watch. Julian date 2459483.793. She copied the number into the paper notebook, and the pen tip pressed a ridge into the back of the page.